Proceedings Volume 9446

Ninth International Symposium on Precision Engineering Measurement and Instrumentation

Junning Cui, Jiubin Tan, Xianfang Wen
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Proceedings Volume 9446

Ninth International Symposium on Precision Engineering Measurement and Instrumentation

Junning Cui, Jiubin Tan, Xianfang Wen
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Volume Details

Date Published: 27 February 2015
Contents: 2 Sessions, 187 Papers, 0 Presentations
Conference: International Symposium on Precision Engineering Measurement and Instrumentation 2014
Volume Number: 9446

Table of Contents

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Table of Contents

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  • Front Matter: Volume 9446
  • International Symposium on Precision Engineering Measurement and Instrumentation 2014
Front Matter: Volume 9446
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Front Matter: Volume 9446
This PDF file contains the front matter associated with SPIE Proceedings Volume 9446, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.
International Symposium on Precision Engineering Measurement and Instrumentation 2014
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Grating encoder for wide range three-axis displacement measurement
Jie Lin, Jian Guan, Feng Wen, et al.
A grating encoder, which is composed of two equal periodic planar gratings, is proposed for measuring wide range three-axis displacements with nanometric resolution. In the optical reading system, one grating works as a reference planar grating, while another one is a scale planar grating. The grating encoder records the x- and y-axis displacement information in terms of the grating period, while it records the z-axis displacement information in terms of both the wavelength of the laser and the grating period. In this scheme, the gratings and other optical elements satisfy the Littrow configuration. The positions and the size of the detected interference zones are almost constant when the scale grating moves along the z-axis with respect to the optical reading system. Therefore, the measurement range is greatly enhanced in the z-axis direction. When the wavelength of the laser is 632.8 nm and the scale grating with period 8 μm is 100×100 mm2, the measured maximal z-axis displacement of the proposed encoder is 1263 mm theoretically.
Analysis of the rail's settlement on the measurement of the diameter of wheel-set
In order to detect the diameter of a wheel-set online, the diameter was detected by using a laser displacement sensor and two eddy current displacement sensors at a speed of 15km/h. The weight of the wheel -set caused extrusion of the rail and changed the original measuring position, which had severe influence on the measuring results, so the influence of the deformation of the rail is analyzed and a compensation method based on the detection of the settlement of the rail is proposed. After compensation, the errors of the results are within ±0.5mm and the standard deviation is 0.12mm. The measuring results showed that the compensation method satisfied with the need of measuring accuracy.
Recovering fNIRS brain signals: physiological interference suppression with independent component analysis
Y. Zhang, M. Shi, J. Sun, et al.
Brain activity can be monitored non-invasively by functional near-infrared spectroscopy (fNIRS), which has several advantages in comparison with other methods, such as flexibility, portability, low cost and fewer physical restrictions. However, in practice fNIRS measurements are often contaminated by physiological interference arising from cardiac contraction, breathing and blood pressure fluctuations, thereby severely limiting the utility of the method. Hence, further improvement is necessary to reduce or eliminate such interference in order that the evoked brain activity information can be extracted reliably from fNIRS data. In the present paper, the multi-distance fNIRS probe configuration has been adopted. The short-distance fNIRS measurement is treated as the virtual channel and the long-distance fNIRS measurement is treated as the measurement channel. Independent component analysis (ICA) is employed for the fNIRS recordings to separate the brain signals and the interference. Least-absolute deviation (LAD) estimator is employed to recover the brain activity signals. We also utilized Monte Carlo simulations based on a five-layer model of the adult human head to evaluate our methodology. The results demonstrate that the ICA algorithm has the potential to separate physiological interference in fNIRS data and the LAD estimator could be a useful criterion to recover the brain activity signals.
Design of CCD driver for quartz horizontal pendulum tiltmeter based on CPLD
Weiwei Zhan, Haiyan Lu, Li Cai, et al.
In order to improve the resolution and conversion speed of photoelectric transducer, a high sensitive and low dark current CCD image sensor TCD1711DG was used in SQ-70D digital quartz horizontal pendulum tiltmeter. The timing chart of CCD has fixed state transition and rigorous timing requirements at typical pulse frequency. Then, a method of controlling the pulse state transition was developed by synchronous counting. The driver was carried out by using Verilog HDL based on CPLD. Simulation and experimental results indicated that the driver designed by this method was simple and stable enough to meet the timing requirements of TCD1711DG. Furthermore, integration time of the CCD could be revised flexibly by setting controlled variable QINT which improved the adaptability of the tiltmeter to different lighting levels.
Design of handwriting drawing board based on common copper clad laminate
Hongyuan Wang, Wenzhi Gao, Yuan Wang
Handwriting drawing board is not only a subject which can be used to write and draw, but also a method to measure and process weak signals. This design adopts 8051 single chip microprocessor as the main controller. It applies a constant-current source[1][2] to copper plate and collects the voltage value according to the resistance divider effect. Then it amplifies the signal with low-noise and high-precision amplifier[3] AD620 which is placed in the low impedance and anti-interference pen. It converts analog signal to digital signal by an 11-channel, 12-bit A/D converter TLC2543. Adoption of average filtering algorithm can effectively improve the measuring accuracy, reduce the error and make the collected voltage signal more stable. The accurate position can be detected by scanning the horizontal and vertical ordinates with the analog switch via the internal bridge of module L298 which can change the direction of X-Y axis signal scan. DM12864 is used as man-machine interface and this hominization design is convenient for man-machine communication. This collecting system has high accuracy, high stability and strong anti-interference capability. It's easy to control and has very large development space in the future.
Implementation of real-time displacement precision measurement technology for the sinusoidal phase-shifting laser self-mixing interferometer
An advanced sinusoidal phase-shifting technique and a time-domain phase demodulation method were used to improve the measurement accuracy and realize the real-time measurement speed of the laser self-mixing interferometer in a large range of displacement. An electro-optic crystal modulator (EOM) was used to realize the sinusoidal phase-shifting on the laser beam in the external cavity. The interference signal was demodulated using a time-domain phase demodulation method. The speed requirement could be met by combining the two together in a wide range of displacement measurement processes together with the real-time measurement requirement as an interferometer at the same time. It was experimentally verified that the displacement measurement precision of a sinusoidal phase-shifting laser self-mixing interferometer could reach less than 0.5 μm in the hundred mm large-scale displacement measuring process. In addition, the factors affecting the interferometer’s measurement speed in the real-time displacement measurement process is analyzed and the maximum speed of our system was obtained as well. Keywords: self-mixing interference; phase modulation; time-domain phase demodulation
Correction of NIM-3A absolute gravimeter for self-attraction effect
Chunjian Li, Jin-yi Xu, Jin-yang Feng, et al.
The mass of free-fall absolute gravimeter can produce vertical gravitational attraction to the free-falling test body during the measurement of acceleration due to gravity. The vertical gravitational attraction can cause an artificial deviation to the measured value of gravitational acceleration. This paper describes the operating principle of a free-fall absolute gravimeter and the method used to determine the reference height of a gravimeter. It also describes the physical structure of NIM-3A absolute gravimeter lately developed by National Institute of Metrology (China), and studies the correction of gravimeter for Self-attraction effect.
Online measurement for geometrical parameters based on 2D laser sensor
Based on 2-D laser sensor, an optimized system for dynamically measuring geomet rical parameters of train wheels is proposed in this paper. The calibrat ion of the system is simplified by combining a 1-D laser sensor and a 2-D laser sensor. Accuracy of the 2-D laser sensor reaches 0.2mm and it ensures that most information of the wheel tread surface is acquired. The geometrical parameters including wheel diameter, flange thickness, flange height, tread wear and rim width can be calculated once the information is processed. In order to improve the measurement accuracy of wheel diameter, a new method for spatial circle fitting is proposed. According to the results acquired in the field, the measurement system can satisfy the requirements of dynamically measuring the geometrical parameters of train wheels.
Application of harmonic analysis method based on two-dimensional Fourier transform to flatness error sampling
Yu Wang, Xingwang Li, Dongdong Ma, et al.
The flatness errors of several different parts were sampled from a Coordinate Measuring Machine and then the harmonic characteristics of flatness errors were analyzed by observing the three-dimensional frequency spectrum obtained by calculating the data through Two-Dimensional Fast Fourier Transform. It was found through experiment and analysis that each harmonic component of a flatness error is generally similar if the processing system is reliable, i.e. the highest harmonic wavelength of a random error is infinite, and Nyquist Sampling Theorem can not be applied to directly verify flatness error sampling points.
Failure analysis of energy storage spring of automobile composite brake chamber
Zai Luo, Qing Wei, Xiaofeng Hu
This paper set energy storage spring of parking brake cavity, part of automobile composite brake chamber, as the research object. And constructed the fault tree model of energy storage spring which caused parking brake failure based on the fault tree analysis method. Next, the parking brake failure model of energy storage spring was established by analyzing the working principle of composite brake chamber. Finally, the data of working load and the push rod stroke measured by comprehensive test-bed valve was used to validate the failure model above. The experimental result shows that the failure model can distinguish whether the energy storage spring is faulted.
Modeling of terahertz metamaterial-sensors for simulation based on effect of resonance induction
Yehua Bie, Jun Luo, Weijun Li, et al.
In order to observe more properties of an electrically resonant metamaterial-sensor, a single cubic unit of the matamaterial-sensor was simulated using the finite-element algorithm and Microwave Studios by CST. Meanwhile, an adaptive mesh refinement was used to ensure an accurate numerical solution with relatively short calculation time. In order to effectively conduct the simulation, some field monitors were also added to help the observation of electromagnetic properties of the unit. Through the electromagnetic simulation, the transmission and reflection spectra of the unit metamaterial-sensor were acquired. At the SRR gap, each kind of metamaterial-sensor structure presents an obvious resonant response at several THz frequency points. Simulation results indicated that the transmission was as low as 0.03 at ~0.79 THz. Other simulation results such as the surface current, the electric field, the electric energy density, and the power loss density, were also observed. By analyzing the simulation results, an idea to obtain the resonant strength in an indirect way was worked out and a way was found to realize the multispectral imaging in THz region.
Effect of self-vibration on accuracy of free-fall absolute gravity measurement with laser interferometer
A free-fall absolute gravimeter was used to measure the gravity acceleration of a corner-cube released in high vacuum, and the gravity acceleration was determined by fitting the free-falling trajectories obtained through optical interferometry. During the measurement, the self-vibration of an absolute gravimeter caused ground vibration and the change in optical path length due to vibration of vacuum-air interface, which resulted in a measurement error. Numerical simulation was run by introducing vibration disturbance to the trajectories of free-fall. The effect of disturbance under different instrumental self-vibration conditions was analyzed. Simulation results indicated that the deviation of calculated gravity acceleration from the preset value and residuals amplitude after fitting depended on the amplitude and initial phase of the vibration disturbance. The deviation value and fitting residuals amplitude increased with the increasing of amplitude and there was a one-to-one correspondence between the two. The deviation of calculated gravity acceleration decreases by properly setting the initial phase difference of vibration disturbance with respect to the interference fringe signal.
Extension of light transmission distance of single core fiber with a micro axicon fixed at fiber end
Yuanzheng Chen, Tong Zhou, Jiwen Cui, et al.
A micro-axicon was designed and fixed at the end of single core fiber to extend its light transmission distance. The effectiveness of the micro-axicon was verified through simulation and experiment. Simulation and experimental results indicated that compared to a flat end, the divergence angle of effluent light could be reduced from 4.1° to 0.47°, and an increase of 80μm could be achieved using the micro-axicon fixed at fiber end in the light transmission distance of single core fiber. The stability of light beam was improved by 97% using the micro-axicon. It was therefore concluded the micro-axicon fixed at the fiber end was effective in extending the light transmission distance of single core fiber.
Compressive sensing image fusion based on blended multi-resolution analysis
Ying Tong, Leilei Liu, Meirong Zhao, et al.
Focusing on the pixel level multi-source image fusion problem, the paper proposes an algorithm of compressive sensing image fusion based on the multi-resolution analysis. We present the method to decompose the images by nonsubsampled contourlet transform and wavelet successively, and fuse the images in the compressive domain. It means that the images can be sparsely represented by more than one basis functions. Since the nonsubsampled contourlet and wavelet basis functions have complementary advantages in the image multi-resolution analysis, and the signals are sparser after decomposed by two kinds of basis functions, the proposed algorithm has perceived advantages in comparison with CS image fusion in the wavelet domain which is widely reported by literatures. The simulations show that our method provides promising results.
Uncertainty evaluation for field experimental standard of vehicle speed-measuring devices in actual traffic
Lei Du, Qiao Sun, Yin Bai, et al.
A field experimental standard for traffic speed measurement was set up at No.G92 Expressway of China from Hangzhou to Shanghai for field tests of vehicle speed-measuring devices in actual traffic, and it met the requirements of the recommendation in OIML R 91 about the metrological field tests of pattern approval. This paper firstly introduces the speed measurement principle of the standard equipment and evaluates the uncertainty of speed measurement. Secondly, a field test based on this standard equipment is designed and performed on a radar speed-measuring device to evaluate its actual speed measurement performance in actual traffic. Finally, the uncertainty of measurement of field test error in actual traffic is evaluated.
Design of Pound-Drever-Hall laser frequency stabilization system without phase shifter
Juan Su, Mingxing Jiao, Junhong Xing, et al.
The Pound-Drever-Hall (PDH) laser frequency stabilization is a wide spread adopted technique for narrow linewidth and ultra-stable lasers, and a phase shifter is an important part in a traditional PDH frequency stabilization system. A PDH laser frequency stabilization system without phase shifter was proposed, in which quadrature coherent detection method was used to extract the frequency drifts. Orthogonal reference signals are generated using direct digital frequency synthesizer (DDS) and mixed with the output of a photo-detector. Over-sampling technique and cumulative average algorithm were used to improve the detection resolution and SNR, orthogonal phase sensitive detection algorithm was adopted to obtain the frequency drifts. Both the quadrature demodulation system structure and the signal processing methods were adopted, the systematic detection error is reduced, the anti-noise performance is raised and long term frequency stability is improved with the PDH laser frequency stabilization system without phase shifter.
Measurement of the spectral characteristics and color parameters of flat objects
Elena V. Gorbunova, Aleksandr N. Chertov, Elena A. Lastovskaia, et al.
Quality control of different coatings (colorful, paint, marker, safety, etc.) that are applied to the surface of various objects (both metallic and non-metallic) is an important problem. Also, there is a problem of dealing with counterfeit products. So it’s necessary to distinguish the fake replicas of marking from the authentic marking of producer. To solve these problems, we propose an automated device (hardware and software complex) for analysis and control of spectral reflection characteristics, albedo and color parameters of extended (up to 150 mm × 150 mm) flat objects. It allows constructing the color image of the object surface as well as its multispectral images in selected regions of the spectrum. Herewith the color of the object surface can be calculated for various standard light sources (A, B, C, D65, E, F2, F7, F11, GE), or to any light source with a predetermined emission spectrum. The paper presents the description of construction and working principles of the proposed hardware and software complex. All color settings calculations correspond to the requirements and recommendations of CIE.
The system of blade's shape measuring
System that will allow visual and measuring control of blades is proposed. It based on triangulation method of measurement. This method implies using of elements described below: a receiving unit, source of structured light, processing and control unit, the monitor and power supply unit. Geometrical characteristics of the system are calculated. As a result we got numbers of receiving units and sources of structured light needed to monitor blade along its entire length. Theoretical error of system measurement is calculated. It depends on distance to the object, the base between receives unit and sources of structured light, resolution and physical size of image receive. Surface of blade is not flat this fact entails changing distance from object to receive unit. So the error of measurement will be different. The interval for researching was chosen from 90 to 130 mm. Error of measurement have steady upward trend from 0,08 to 0,017 mm all period between chosen distances. The physical model of control method is developed. As a result of its working picture of illuminated metal object was obtained. The program written in MatLab processes experimental picture, find lines of structure light and calculate dislocations of it. Then use this information to make a three-dimensional model of object.
Multipurpose optic-electronic autocollimators for measuring deformations of the axle with a millimeter wave range radiotelescope
Igor Konyakhin, Fedor Molev, Alexey Konyakhin, et al.
The improved autocollimators for measuring angular deformations of the large constructions as support tube of mirror and elevation axle of the radio telescopes are analyzed. Two new types of the reflector for autocollimator are researched. The first type of the reflectors is the tetrahedral reflector with flat reflecting sides and invariant axis. The autocollimator with tetrahedral reflector is used for the measuring 3-D deformations as roll, pitch and yaw angular deviations. The second type of the reflector is the composition of the anamorphic wedge system and ordinary cube-corner retroreflector. This reflector generates the narrow beam, as result the work distance and the range of measurement of the roll angle increase. Technical characteristics of the experimental setups of new reflectors are presented. Features of the tetrahedral reflector and anamorphic system as the reflectors for multipurpose autocollimator are discussed.
Optic-electronic systems for measurement a position of radio-telescope components
Igor A. Konyakhin, Andrew V. Petrochenko, Nina S. Tolochek
In article is described the method of the «angle photometric resection» and the definition of the parameters of the external orientation (spatial coordinates of the points of shooting and the angular position of the shooting plane) and his use for the optic-electronic system that determinates the position of counter-reflector.
A new suspension structure of micro/nano probe
Yong Li, Shuai Wang, ZhaoRui Chu, et al.
The measuring force of a micro/nano probe is an important factor affecting the probe measurement accuracy. The strength of the force largely depends on the nature of the suspension structure. How to improve the flexibility of the suspension structure is a difficult issue. To tackle the problem, this paper will put forwards an integrated suspension structure, which composed of three evenly spaced elastic hinges. Each elastic hinge has two beams, one of which is used to as the support. In measurement, the maximum displacement is occurred at the intersection of the two beams. In this paper, the flexibility of the suspension structure and probe measuring capability related to the elastic hinge's size and material are investigated based on theoretical modeling and simulation. The research result is significant to reduce the probe measuring force and improve its sensitivity.
Calibration of GPS based high accuracy speed meter for vehicles
Yin Bai, Qiao Sun, Lei Du, et al.
GPS based high accuracy speed meter for vehicles is a special type of GPS speed meter which uses Doppler Demodulation of GPS signals to calculate the speed of a moving target. It is increasingly used as reference equipment in the field of traffic speed measurement, but acknowledged standard calibration methods are still lacking. To solve this problem, this paper presents the set-ups of simulated calibration, field test signal replay calibration, and in-field test comparison with an optical sensor based non-contact speed meter. All the experiments were carried out on particular speed values in the range of (40-180) km/h with the same GPS speed meter. The speed measurement errors of simulated calibration fall in the range of ±0.1 km/h or ±0.1%, with uncertainties smaller than 0.02% (k=2). The errors of replay calibration fall in the range of ±0.1% with uncertainties smaller than 0.10% (k=2). The calibration results justify the effectiveness of the two methods. The relative deviations of the GPS speed meter from the optical sensor based noncontact speed meter fall in the range of ±0.3%, which validates the use of GPS speed meter as reference instruments. The results of this research can provide technical basis for the establishment of internationally standard calibration methods of GPS speed meters, and thus ensures the legal status of GPS speed meters as reference equipment in the field of traffic speed metrology.
Study on the detection of a cylindrical surface-breaking bore-hole reflector based on laser ultrasonic technology
Haitao Wang, Wei Zeng, Xianming Yang, et al.
In this paper, a visualization system was proposed based on ultrasound excitation from a Q-switched pulsed YAG laser. The ultrasonic wave was received by a piezoelectric transducer. The electrical time-domain signal was analyzed in the Fourier-domain in order to detect a hole-like reflector in an austenitic stainless steel specimen. At a given receiver position, a piezoelectric transducer received the ultrasonic wave signal. The electrical time-domain signal was analyzed in the Fourier-domain. The experimental research on the influence of the relative position distance between the laser excitation spot and the defect of the test specimen was conducted. The experimental results showed a significant geometrical imaging of the reflector shape with the scanned data. Therefore, a quantitative laser ultrasound visualization system was realized along with the spectral analysis. It will provide a new method of defects detection and sizing.
Measurement of size error in industrial CT system with Calotte cube
DaoDang Wang, XiXi Chen, FuMin Wang, et al.
A measurement method with calotte cube was proposed to realize the high-precision calibration of size error in industrial computer tomography (CT) system. Using the traceability of calotte cube, the measurement of the repeatability error, probing error and length measurement error of industrial CT system was carried out to increase the acceptance of CT as a metrological method. The main error factors, including the material absorption, projection number and integration time and so on, had been studied in detail. Experimental results show that the proposed measurement method provides a feasible way to measure the size error of industrial CT system. Compared with the measurement results with invar 27- sphere gauge, a high accuracy in the order of microns is realized with the proposed method based on calotte cube. Differing from the invar 27-sphere gauge method, the material particularity of calotte cube (material of metallic titanium) could introduce beam hardening effect, the study on the influence of material absorption and structural specificity on the measurement, which provides significant reference for the measurement of metallic samples, is necessary.
On-orbit calibration of space camera based on stellar image correspondences
You Zhai, Luan Zeng, Wei Xiong
At least three stellar images are needed from different points in space with different orientations of the camera and calibration is realized by finding correspondent stars in stellar images. The method doesn't need any knowledge of orientations of the camera and the calibration is only based on the stellar image correspondences. In this method, homography between stellar images induced by stars (called star-homo for short) is used to approximate the infinite homography (called inf-homo for short). It is well known that the inf-homo provides constraints on image of absolute conic (IAC) which is related to camera internal parameters. Therefore, we use star-homo to replace of inf-homo to compute IAC. When IAC is computed, we can decompose camera internal parameters from IAC. When computing IAC, an unknown scale factor exists, this makes the constraints on IAC nonlinear. In order to transform nonlinear equations to linear equations, we precompute the scale factor by initial principal point estimate. The advantage brought by linear equations is that it is easier to calculate and the results are more accurate and robust. The experimental results show that the proposed method is feasible and can calibrate the space camera with high precision. Under 1 pixel star points extraction error, the relative errors of camera internal parameters are below 0.7%.
Modeling and active vibration control of six-DOF manipulator through μ-synthesis with parameter uncertainties
Kaiping Yu, Ying Wu
A new linear dynamic model of a six-spherical-prismatic-spherical (SPS) Stewart platform with the base excitation was formulated via Kane’s method. In order to satisfy the practical situation, the uncertainties of mass center location, stiffness and damping were concerned. Then a robust μ-synthesis controller was developed by applying D-K iteration to attenuate the base excitation. Comparisons were conducted by analyzing the responses of the open and closed loops in the frequency and time domain. Simulation results indicated that the proposed robust controller is of fine properties and good robustness, which laid a sound foundation of active micro-vibration control of a satellite.
Reflective off-axis point-diffraction interferometer based on Michelson architecture
Hongyi Bai, Lili Guo, Zhi Zhong, et al.
A reflective off-axis point-diffraction interferometer based on Michelson architecture is built to measure static and dynamic quantitative phase in a single shot. The interferometer is constructed by a beam-splitter, a pinhole mirror, a reflective mirror and two lenses to build a 4f optical system. The pinhole mirror is used as a low-pass spatial filter to generate reference wave. By tilting the reflective mirror, a small angle is created between the object beam and the reference beam to enable an off-axis interferogram. To reconstruct an interferogram with a few fringes, Kreis Fourier method is used to recovery the specimen phase. Using a plano-convex cylinder lens and an evaporative alcohol drop as the specimens, experiments are run to verify the effectiveness and robustness with this interferometer. Experimental results show that this interferometer has not only simple setup and good anti-interference performance, but also good real-time ability, which makes it suitable for dynamic phase measurement.
Improved SIFT descriptor applied to stereo image matching
Luan Zeng, You Zhai, Wei Xiong
Scale Invariant Feature Transform (SIFT) has been proven to perform better on the distinctiveness and robustness than other features. But it cannot satisfy the needs of low contrast images matching and the matching results are sensitive to 3D viewpoint change of camera. In order to improve the performance of SIFT to low contrast images and images with large 3D viewpoint change, a new matching method based on improved SIFT is proposed. First, an adaptive contrast threshold is computed for each initial key point in low contrast image region, which uses pixels in its 9×9 local neighborhood, and then using it to eliminate initial key points in low contrast image region. Second, a new SIFT descriptor with 48 dimensions is computed for each key point. Third, a hierarchical matching method based on epipolar line and differences of key points’ dominate orientation is presented. The experimental results prove that the method can greatly enhance the performance of SIFT to low contrast image matching. Besides, when applying it to stereo images matching with the hierarchical matching method, the correct matches and matching efficiency are greatly enhanced.
Phase compensation with fiber optic surface profile acquisition and reconstruction system
A fiber-optic sinusoidal phase modulating (SPM) interferometer was proposed for the acquisition and reconstruction of three-dimensional (3-D) surface profile. Sinusoidal phase modulation was induced by controlling the injection current of light source. The surface profile was constructed on the basis of fringe projection. Fringe patterns are vulnerable to external disturbances such as mechanical vibration and temperature fluctuation, which cause phase drift in the interference signal and decrease measuring accuracy. A closed-loop feedback phase compensation system was built. In the subsystem, the initial phase of the interference signal, which was caused by the initial optical path difference between interference arms, could be demodulated using phase generated carrier (PGC) method and counted out using coordinated rotation digital computer (CORDIC) , then a compensation voltage was generated for the PZT driver. The bias value of external disturbances superimposed on fringe patterns could be reduced to about 50 mrad, and the phase stability for interference fringes was less than 6 mrad. The feasibility for real-time profile measurement has been verified.
Establishment of theoretical model and experimental equipment for researching on carbon contamination of EUV multi-layer mirror
Xuepeng Gong, Qipeng Lu, Guoqing Lu
Carbon contamination on extreme ultraviolet (EUV) multi-layer mirror is a seriously restrictive factor for lithography quality, chip output and life of lithography machine. In order to estimate the carbon contamination of EUV multi-layer and study the mechanism of carbon contamination deeply, an effective theoretical model of the carbon deposition on the multi-layer surface and experimental equipment for studying the carbon contamination are established. The theoretical model describes the transport of residual hydrocarbons to the irradiated area and the subsequent dissociation of the hydrocarbon by direct EUV radiation and secondary electron excitation, and indicates that the direct EUV radiation is the primary reason to dissociate the hydrocarbon, and makes the carbon deposited on the surface of multi-layer. Various carbon deposition states are simulated by the theoretical model, and some effective simulated results are obtained. Optical design scheme and structure design scheme of the experimental equipment are presented. The optical system includes two spherical multi-layer mirrors and a plane mirror multi-layer mirror. Ray trace and EUV intensity on sample are calculated, the light spot on sample is about Φ10mm and the EUV intensity is about 0.126mW/mm2. Structure of the experimental equipment includes adjusting mechanism of two spherical mirrors, rotary mechanism of plane mirror, alignment mechanism of EUV source, adjusting mechanism of sample, and so on. After testing, linear resolution and angle resolution of two spherical mirrors adjusting mechanism are 1μm and 5μrad respectively; linear displacement and linear resolution of sample adjusting mechanism are 50mm and 1μm respectively. The structure design scheme meets the requirement of the carbon contamination experiment.
Common mode EMI prediction and research in induction motor for electric vehicles
Yinhan Gao, Juxian Wang, Kaiyu Yang, et al.
This paper presents an equivalent circuit of high frequency voltage-controlled switch model of IGBT, and a surge voltage absorption circuit as well. This model can not only significantly reduce the surge voltage, decrease EMI noise, but also obviously inhibit common mode voltage towards the DC power mains.
Super-resolution imaging based on virtual Airy spot
Zhengjun Liu, Cheng Guo, Junning Cui, et al.
Based on the theoretical model of Airy spot, a method is proposed for improving the imaging speed from confocal microscopy. The virtual Airy spot is designed for obtaining the pattern on CCD at detecting plane. Here the size of the spot is determined by the parameters of imaging system and intensity data from point detector, which can receive data quicker than CCD. The treatment can improve the speed of imaging comparing with CCD at receiving end. The virtual structured detection is also utilized for generating high-resolution image. Some numerical simulation results are provided for demonstrating the validity of the proposed method.
Design of the digital quartz horizontal pendulum tiltmeter based on CCD
Li Cai, Hai-yan Lu, Wei-wei Zhan, et al.
This paper describes the quartz horizontal pendulum tiltmeter system based on CCD to convert traditional analog quartz horizontal pendulum tiltmeter to digital quartz horizontal pendulum tiltmeter, the measurement principle and application of CCD image sensor in this system. The system has the advantages of high resolution, fast response and it can realize the real-time observation. In the actual application, the system can provide valuable precursory information for the work of earthquake analysis and prediction.
Wireless communication bandpass optical window with double-layer hexagon aperture FSS array
Yongmeng Liu, Yu Han, Jieru Cao, et al.
Dielectric loading in bandpass double-layer frequency selective surface design is a necessary process. The problem that dielectric loaded inducing the transmission loss in the centre of the frequency response curve is difficult to be avoided. Hexagon aperture FSS array is studied by numerical calculation and simulation analysis. The different way of loading dielectric, the different dielectric constant of double-layer FSS and the different coupling way of the two layer transmission curve have great influence on the transmission characteristics. Simulation results show that decreasing the thickness and permittivity of the dielectric can reduce the transmission loss. Besides, the sunken degree in the centre of the pass-band can be improved by extending the bandwidth. Aiming at comprehensive improving the transmission characteristics like band width, cutoff steepness, polarization and angle insensitivity and transmission loss, a modified dielectric loaded double-layer hexagon aperture FSS array structure is designed.
Precision measurement of squareness of large rectangular square
Min-qiang Jia, Jian Zhang, Ran Gao, et al.
An entire set of measurement scheme was designed to measure a granite rectangular square of (2000×1600) mm in size. Each angle was measured separately using the squareness measurement system, and data processing was then carried out using closure principle. A dedicated slider with air-bearing was also designed to obtain more stable and reliable data.
Design of extensible meteorological data acquisition system based on FPGA
Wen Zhang, Yin-hua Liu, Hui-jun Zhang, et al.
In order to compensate the tropospheric refraction error generated in the process of satellite navigation and positioning. Temperature, humidity and air pressure had to be used in concerned models to calculate the value of this error. While FPGA XC6SLX16 was used as the core processor, the integrated silicon pressure sensor MPX4115A and digital temperature-humidity sensor SHT75 are used as the basic meteorological parameter detection devices. The core processer was used to control the real-time sampling of ADC AD7608 and to acquire the serial output data of SHT75. The data was stored in the BRAM of XC6SLX16 and used to generate standard meteorological parameters in NEMA format. The whole design was based on Altium hardware platform and ISE software platform. The system was described in the VHDL language and schematic diagram to realize the correct detection of temperature, humidity, air pressure. The 8-channel synchronous sampling characteristics of AD7608 and programmable external resources of FPGA laid the foundation for the increasing of analog or digital meteorological element signal. The designed meteorological data acquisition system featured low cost, high performance, multiple expansions.
Application of coordinate transform on ball plate calibration
Hengzheng Wei, Weinong Wang, Guoying Ren, et al.
For the ball plate calibration method with coordinate measurement machine (CMM) equipped with laser interferometer, it is essential to adjust the ball plate parallel to the direction of laser beam. It is very time-consuming. To solve this problem, a method based on coordinate transformation between machine system and object system is presented. With the fixed points’ coordinates of the ball plate measured in the object system and machine system, the transformation matrix between the coordinate systems is calculated. The laser interferometer measurement data error due to the placement of ball plate can be corrected with this transformation matrix. Experimental results indicate that this method is consistent with the handy adjustment method. It avoids the complexity of ball plate adjustment. It also can be applied to the ball beam calibration.
Abnormal events detection in crowded scenes by trajectory cluster
Abnormal events detection in crowded scenes has been a challenge due to volatility of the definitions for both normality and abnormality, the small number of pixels on the target, appearance ambiguity resulting from the dense packing, and severe inter-object occlusions. A novel framework was proposed for the detection of unusual events in crowded scenes using trajectories produced by moving pedestrians based on an intuition that the motion patterns of usual behaviors are similar to these of group activity, whereas unusual behaviors are not. First, spectral clustering is used to group trajectories with similar spatial patterns. Different trajectory clusters represent different activities. Then, unusual trajectories can be detected using these patterns. Furthermore, behavior of a mobile pedestrian can be defined by comparing its direction with these patterns, such as moving in the opposite direction of the group or traversing the group. Experimental results indicated that the proposed algorithm could be used to reliably locate the abnormal events in crowded scenes.
Design and implementation of embedded ion mobility spectrometry instrument based on SOPC
Genwei Zhang, Jiang Zhao, Liu Yang, et al.
On the hardware platform with single CYCLONE IV FPGA Chip based on SOPC technology, the control functions of IP cores of a Ion Mobility Spectrometry instrument was tested, including 32 bit Nios II soft-core processor, high-voltage module, ion gate switch, gas flow, temperature and pressure sensors, signal acquisition and communication protocol. Embedded operating system μCLinux was successfully transplanted to the hardware platform, used to schedule all the tasks, such as system initialization, parameter setting, signal processing, recognition algorithm and results display. The system was validated using the IMS diagram of Acetone reagent, and the instrument was proved to have a strong signal resolution.
An excitation signal source with anti-interference ability for eddy current testing
Guodong Jiang, Po Li
An eddy current excitation signal source was designed based on the linear control theory. By analyzing the interference and characteristics of signal source, a multi-input-single-output (MISO) feedback control system was designed and created using a lock-in amplifier, and an eddy current sensor was applied in the feedback loop of the system. As a result, the noise in the loop circuit was suppressed; this resolved the current instability problem in eddy current sensor. Furthermore, a mathematical model was established, and the stability and bandwidth of the system were verified by simulations. Compared with the traditional signal sources, experimental results show that this signal source had steadier current output, smaller temperature drift and stronger load capability. Therefore, the foil thickness measurement based on this signal source had a very high accuracy.
A simple fiber optic humidity sensor based on water-absorption characteristic of CAB
A simple fiber-optic relative humidity sensor based on cellulose acetate butyrate (CAB) and Fresnel reflection is proposed and investigated theoretically and experimentally. The sensing system is only composed of one light source, three optical couplers, two photo-detectors and two fiber sensing ends. The operation principle is based on relative Fresnel reflection and water-absorption characteristic of the CAB which simultaneously contains hydrophilic and hydrophobic groups. The water absorption process will lead to variation of the CAB’s refractive index or permittivity. It has to be noted that the double-channel system can effectively eliminate the intensity fluctuation of the light source and the influence of the environment. In this paper, the relative humidity environments approximately ranging from 10 % to 100% are generated and measured both in the humidification and dehumidification processes, which shows a good repeatability and reveals a very good fitting feature with a high value of R2 above 0.99. It is of reflection type and can be simply extend to be a multi-point-monitoring system. The sensing system is of cost- effective, simple operation and high precision.
Research on cloud-based remote measurement and analysis system
Zhiqiang Gao, Lingsong He, Wei Su, et al.
The promising potential of cloud computing and its convergence with technologies such as cloud storage, cloud push, mobile computing allows for creation and delivery of newer type of cloud service. Combined with the thought of cloud computing, this paper presents a cloud-based remote measurement and analysis system. This system mainly consists of three parts: signal acquisition client, web server deployed on the cloud service, and remote client. This system is a special website developed using asp.net and Flex RIA technology, which solves the selective contradiction between two monitoring modes, B/S and C/S. This platform supplies customer condition monitoring and data analysis service by Internet, which was deployed on the cloud server. Signal acquisition device is responsible for data (sensor data, audio, video, etc.) collection and pushes the monitoring data to the cloud storage database regularly. Data acquisition equipment in this system is only conditioned with the function of data collection and network function such as smartphone and smart sensor. This system’s scale can adjust dynamically according to the amount of applications and users, so it won't cause waste of resources. As a representative case study, we developed a prototype system based on Ali cloud service using the rotor test rig as the research object. Experimental results demonstrate that the proposed system architecture is feasible.
A new method for determining the Tikhonov regularization parameter of load identification
Wei Gao, Kaiping Yu
A new method based on quadratic programming theory is proposed to determine the regularization parameter. A function whose variable is the derivative with respect to the regularization parameter is formulated. Based on the property that the value of the function is very dependent on the regularization parameter, the optimal parameters can be determined by using quadratic programming theory. A numerical example is utilized to select the parameters through the method. It is concluded that the new method can effectively overcome the ill-posed problems from an ill-conditioned system matrix, and that it can obtain an approximate solution with higher accuracy, fine stability and effective noise resistance.
GNSS software receiver sampling noise and clock jitter performance and impact analysis
Jian Yun Chen, XuZhe Feng, XianBin Li, et al.
In the design of a multi-frequency multi-constellation GNSS software defined radio receivers is becoming more and more popular due to its simple architecture, flexible configuration and good coherence in multi-frequency signal processing. It plays an important role in navigation signal processing and signal quality monitoring. In particular, GNSS software defined radio receivers driving the sampling clock of analogue-to-digital converter (ADC) by FPGA implies that a more flexible radio transceiver design is possible. According to the concept of software defined radio (SDR), the ideal is to digitize as close to the antenna as possible. Whereas the carrier frequency of GNSS signal is of the frequency of GHz, converting at this frequency is expensive and consumes more power. Band sampling method is a cheaper, more effective alternative. When using band sampling method, it is possible to sample a RF signal at twice the bandwidth of the signal. Unfortunately, as the other side of the coin, the introduction of SDR concept and band sampling method induce negative influence on the performance of the GNSS receivers. ADC’s suffer larger sampling clock jitter generated by FPGA; and low sampling frequency introduces more noise to the receiver. Then the influence of sampling noise cannot be neglected. The paper analyzes the sampling noise, presents its influence on the carrier noise ratio, and derives the ranging error by calculating the synchronization error of the delay locked loop. Simulations aiming at each impact factors of sampling-noise-induced ranging error are performed. Simulation and experiment results show that if the target ranging accuracy is at the level of centimeter, the quantization length should be no less than 8 and the sampling clock jitter should not exceed 30ps.
Conversion of infrared grey-level image into temperature field by polynomial curve fitting
Terry Yuan-Fang Chen, Ming-Hsuan Kuo
A simple method to convert the infrared gray-level image into temperature field is developed by using least squares polynomial curve fitting. In this method, the correspondence between the infrared gray-level image and the associated temperature field for various emissivity values and temperature range is analyzed first. Then a second-order polynomial can be applied to fit the correspondence between the gray-level image and the associated temperature field as a function of emissivity. For multiple conversions of temperature ranges, the constants of the fitted polynomial in multiple ranges can be further fitted as a function of emissivity and temperature range. Test of the method on a cup of hot water was done. An average error less than 1% was achieved between the proposed method and the commercial ones.
Non-contact measurement of rotation angle with solo camera
Xiaochuan Gan, Anbin Sun, Xin Ye, et al.
For the purpose to measure a rotation angle around the axis of an object, a non-contact rotation angle measurement method based on solo camera was promoted. The intrinsic parameters of camera were calibrated using chessboard on principle of plane calibration theory. The translation matrix and rotation matrix between the object coordinate and the camera coordinate were calculated according to the relationship between the corners’ position on object and their coordinates on image. Then the rotation angle between the measured object and the camera could be resolved from the rotation matrix. A precise angle dividing table (PADT) was chosen as the reference to verify the angle measurement error of this method. Test results indicated that the rotation angle measurement error of this method did not exceed ± 0.01 degree.
Position and orientation measurement during Lunar Rover movement test
Zaihua Yang, Laiying Tang, Wangmin Yi, et al.
During the development of the Lunar Rover, a posture tracking measurement scheme was designed to verify its movement control ability and path planning performance. The principle is based on the indoor GPS measurement system. Four iGPS transmitters were set around the test site. By tracking the positions of four receivers that were installed on the rover, the position and orientation of the rover can be acquired in real time. The rotation matrix and translation vector from the Lunar Rover coordinate system to the test site coordinate system were calculated by using the software. The measurement precision reached 0.25mm in the range of 30m2. The real time position and posture datum of the rover was overlaid onto 3-D terrain map of the test site. The trajectory of the rover was displayed, and the time-displacement curve, time-velocity curve, time-acceleration curve were analyzed. The rover’s performances were verified.
Finite element fatigue analysis of rectangular clutch spring of automatic slack adjuster
Chen-jie Xu, Zai Luo, Xiao-feng Hu, et al.
The failure of rectangular clutch spring of automatic slack adjuster directly affects the work of automatic slack adjuster. We establish the structural mechanics model of automatic slack adjuster rectangular clutch spring based on its working principle and mechanical structure. In addition, we upload such structural mechanics model to ANSYS Workbench FEA system to predict the fatigue life of rectangular clutch spring. FEA results show that the fatigue life of rectangular clutch spring is 2.0403×105 cycle under the effect of braking loads. In the meantime, fatigue tests of 20 automatic slack adjusters are carried out on the fatigue test bench to verify the conclusion of the structural mechanics model. The experimental results show that the mean fatigue life of rectangular clutch spring is 1.9101×105, which meets the results based on the finite element analysis using ANSYS Workbench FEA system.
Design of transmission error signal generator system based on FPGA and ARM
The mechanical phase shifting method is often used to evaluate the accuracy of transmission error (TE) testing system, but the application scope of the mechanical phase shifting method is limited. This paper designed a new type of TE signal generator. Firstly, based on the principle analysis of the mechanical phase shifting method, the relationship between angle error from mechanical phase shifting and pulse signal of sensor is established, and then according to the TE’s synthesis formula we can obtained two displacement sensor signals which are used to replace real mechanical phase forming a special TE signal generator. The signal generator is composed of FPGA and ARM. The TE detection system is used to test the signal generator, after analysis, the error of the TE signal generator is 0.1%, which shows that the TE signal generator can be used to assess accuracy of TE system instead of the mechanical phase shifting method.
High precision fabrication of antennas and sensors
Electron and ion beam lithographies were used to fabricate and/or functionalize large scale - millimetre footprint - micro-optical elements: coupled waveguide-resonator structures on silicon-on-insulator (SOI) and THz antennas on low temperature grown LT-GaAs. Waveguide elements on SOI were made without stitching errors using a fixed beam moving stage approach. THz antennas were created using a three-step litography process. First, gold THz antennas defined by standard mask projection lithography were annealed to make an ohmic contact on LT-GaAs and post-processing with Ga-ion beam was used to define nano-gaps and inter digitised contacts for better charge collection. These approaches show the possibility to fabricate large footprint patterns with nanoscale precision features and overlay accuracy. Emerging 3D nanofabrication trends are discussed.
Optical fiber waist-enlarged bitaper-based Michelson interferometric humidity sensor
Pengbing Hu, Zhemin Chen, Sunqiang Pan, et al.
An optical fiber waist-enlarged bitaper-based Michelson interferometric sensor is proposed and experimentally demonstrated for humidity measurement. The waist enlarged bitaper is created for light coupling between core mode and cladding modes propagating in the fiber interferometer. A chitason layer is plated onto the surface of the interferometer to act as a humidity-to-refractive index (RI) transducer and thus humidity measurement can be realized by monitoring the wavelength shifts of its interferogram induced by RI variations. The influence of the coating thickness and concentration of chitason on relative humidity (RH) measurement is experimentally studied. The coating sensor demonstrates an optimal humidity-sensing ability, with a humidity sensitivity and fast time-response of ~26 pm/%RH and ~5 s respectively, when it is 3-dip coated in chitason solutions of the concentration of 1 wt.%. The proposed humidity sensor is compact, cost-effective and of easy-operation, therefore it has potentials in many practical applications.
Study on the station-moving measurement technology in the flatness measurement of large annular planes with a Laser Tracker
Wen Zhu, Xuedong Cao, Tian-quan Fan, et al.
Laser tracker as a three-dimensional measuring instrument for large dimensions is widely used in the industrial measuring system, which is famous for its high precision, high efficiency, in site measurement and easy to be moved or installed, etc. In order to measure the large annular planes, especially non-continuous planes, a method with laser tracker on the basis of station-moving measurement is proposed. In this paper, the working principle of laser tracker system is described firstly, then the principle of the station-moving measurement is analyzed, finally according to the station-moving measurement principle experiment of the flatness measurement of a Φ5000mm round table is carried out, the result is compared with bridge-level, and feasibility of measuring flatness of large precision parts is validated by experiments and analysis results.
Small sample analysis of vision measurement error
Small sample analysis method is proposed to find out the relationship between measurement distance and position error. The grey absolute correlation degree is first used to analyze the correlations of position measurement error. A grey forecasting model is then used to forecast data and expand the small sample size to a relatively larger one. The multivariate multi-order polynomial fitting is made with data. Finally, the accuracy evaluation indices are used to assess the accuracy of curve fitting, which include maximum, minimum and average relative errors. Experimental results show that the difference between maximum and minimum relative errors is in an acceptable range and the accuracy of curve fitting is proved to be superior to 99% which satisfies the engineering requirements.
Ultraviolet communication system based on BPSK subcarrier intensity modulation
Yong Wang, Song Gu
Ultraviolet communication is a novel communication mode, which delivers massages through the scattering of ultraviolet in the atmosphere. Modulation technology is one of key technical challenges in ultraviolet communication. So far, the ultraviolet communication system mostly uses pulsed optical intensity modulation, but this technique cannot improve the performance of ultraviolet communication system. Thus, BPSK subcarrier intensity modulation is introduced to the ultraviolet communication system based on the analysis of the basic principle of the BPSK subcarrier intensity modulation technology. In the single scattering channel model, the ultraviolet communication system based on BPSK subcarrier intensity modulation technology is simulated and compared with a variety of other intensity modulation technique. The simulation results show that the BPSK subcarrier intensity modulation technique outperforms the traditional OOK and PPM modulation techniques in terms of bit-error-rate, information rate and other properties.
Simulation on measurement of five-DOF motion errors of high precision spindle with cylindrical capacitive sensor
Min Zhang, Wen Wang, Kui Xiang, et al.
This paper describes a novel cylindrical capacitive sensor (CCS) to measure the spindle five degree-of-freedom (DOF) motion errors. The operating principle and mathematical models of the CCS are presented. Using Ansoft Maxwell software to calculate the different capacitances in different configurations, structural parameters of end face electrode are then investigated. Radial, axial and tilt motions are also simulated by making comparisons with the given displacements and the simulation values respectively. It could be found that the proposed CCS has a high accuracy for measuring radial motion error when the average eccentricity is about 15 μm. Besides, the maximum relative error of axial displacement is 1.3% when the axial motion is within [0.7, 1.3] mm, and the maximum relative error of the tilt displacement is 1.6% as rotor tilts around a single axis within [-0.6, 0.6]°. Finally, the feasibility of the CCS for measuring five DOF motion errors is verified through simulation and analysis.
Low-noise front-end electronics for detection of intermediate-frequency weak light signals
Cunbao Lin, Shuhua Yan, Zhiguang Du, et al.
A novel low-noise front-end electronics was proposed for detection of light signals with intensity about 10 μW and frequency above 2.7 MHz. The direct current (DC) power supply, pre-amplifier and main-amplifier were first designed, simulated and then realized. Small-size components were used to make the power supply small, and the pre-amplifier and main-amplifier were the least capacitors to avoid the phase shift of the signals. The performance of the developed front-end electronics was verified in cross-grating diffraction experiments. The results indicated that the output peak-topeak noise of the ±5 V DC power supply was about 2 mV, and the total output current was 1.25 A. The signal-to-noise ratio (SNR) of the output signal of the pre-amplifier was about 50 dB, and it increased to nearly 60 dB after the mainamplifier, which means this front-end electronics was especially suitable for using in the phase-sensitive and integrated precision measurement systems.
Double-grating diffraction interferometric stylus probing system for surface profiling and roughness measurement
Peipei Wei, Zhengang Lu, Lihua Liu
A double-grating diffraction interferometric stylus probing transducer consisting of a cylindrical grating and a planar grating has been presented to transform the surface profile information to electrical signals. The transducer has the merit of compact construction and high resolution. The relationship between the electrical signals and the displacement of the cylindrical grating is briefly reviewed. The existence of the cylindrical grating brings angle and position deviation, and the deviation will affect the interference of the diffracted beams. To ensure the interference of the diffracted beams, the relationships between the angle deviation, the position deviation, and the radius of curvature of the cylindrical grating are analyzed. The analysis shows that the diffracted beams will interfere normally when suitable radius of curvature of the cylindrical grating and suitable distance between the two gratings are adopted, thus the profile information can be obtained.
Absolute distance measurement by spectral interferometry through wavelet transform with frequency comb
Hanzhong Wu, Fumin Zhang, Xinghua Qu
Wavelet transform (WT) was exploited to measure distances based on spectrum interferometry. Complex Morlet wavelet was used as the mother wavelet to obtain the amplitude graph and phase graph simultaneously, and the latter showed the wrapped phase in fact. The distances were measured numerically and experimentally, and each distance for ten times. Experimental results indicated that the distance could be obtained uniquely using wavelet transform, and the reproducibility deviation was 77.7 nm when the measured distance is about 1 mm.
Measurement time interval based on FPGA in NIM-3 absolute gravimeter
In order to perform gravity measurement with compact and portable instrument at several ten mGal accuracy level, a digital fringe signal processing method was proposed for the measurement time interval in a ballistic free-fall absolute gravimeter. This method based on the theory of digital phase-shift which was used in the SOPC system on a FPGA DE2 Electric Board and NIOS-II processor produced by Altera company. This method has been successfully used for the measurement of interference fringe numbers and time interval in NIM-3 ballistic free-fall absolute gravimeter.
Optimization of the signal processing in frequency modulated continuous wave laser ranging system
Based on a dual interferometry frequency modulated wave laser (FMCW) laser ranging system, three steps to optimize the signal processing is proposed in this paper. The first step is signal re-sampling, by which the sampling signal is turned to be equal optical frequency intervals. The second step is splicing the re-sampled signal, by which can break though the tuning range of the laser source limitation. The last step is the all-phase pretreatment of the signal, its means that the all-phase Fast Fourier Transformation (apFFT) is used to handle the re-sampled signal, which could reduce the phase error of the signal. The experiments shows that the noise effect due to the tuning nonlinearity of laser can be reduced by re-sampling the signal, 50μm range resolution can be easily obtained by this method, the apFFT is more reliable and effective than FFT in the processing to reduce the phase error and improve the speed of operation.
Improvement spatial resolution of frequency modulated continuous wave laser ranging system by splicing equal optical frequency interval sampled signal
Guang Shi, Fumin Zhang, Xinghua Qu
A dual interferometry FMCW laser ranging system is presented. The auxiliary interferometer for generating the clock pulses at equally spaced optical frequencies is incorporated into the main interferometer to simplify the system configuration and to compensate the tuning linearity of the laser source. The need of widely tunable laser limits the practical application of the FMCW laser ranging for precision industrial measurement. Splicing sampled signal method is proposed to break though the tuning range of the laser source limitation against the special resolution. In the experiments, 50 μm range resolution at 8.7 m is demonstrated, and this resolution is maintained over the entire measuring range. The measuring range depending on the power and coherence length of the source can reach more than 20 m. The system structure is simple, and the requirement on the tuning range of laser source is reduced in this system.
Nonlinear analysis of cylindrical capacitive sensor used for measuring high precision spindle rotation errors
Kui Xiang, Wen Wang, Min Zhang, et al.
A novel cylindrical capacitive sensor (CCS) with differential, symmetrical and integrated structure was proposed to measure multi-degree-of-freedom rotation errors of high precision spindle simultaneously and to reduce impacts of multiple sensors installation errors on the measurement accuracy. The nonlinear relationship between the output capacitance of CCS and the radial gap was derived using the capacitance formula and was quantitatively analyzed. It was found through analysis that the thickness of curved electrode plates led to the existence of fringe effect. The influence of the fringe effect on the output capacitance was investigated through FEM simulation. It was found through analysis and simulation that the CCS could be optimized to improve the measurement accuracy.
Design of a data acquisition system of articulated arm coordinate measuring machines
A novel cylindrical capacitive sensor (CCS) with differential, symmetrical and integrated structure was proposed to measure multi-degree-of-freedom rotation errors of high precision spindle simultaneously and to reduce impacts of multiple-sensors installation errors on the measurement accuracy. The nonlinear relationship between the output capacitance of CCS and the radial gap was derived using the capacitance formula and was quantitatively analyzed. It was found through analysis that the thickness of curved electrode plates led to the existence of fringe effect. The influence of the fringe effect on the output capacitance was investigated through FEM simulation. It was found through analysis and simulation that the CCS could be optimized to improve the measurement accuracy.
Non-contact measurement for profile of different diameter micro/mini holes with capacitance sensor
Liyan Zhu, Wen Wang, Keqing Lu, et al.
Now the basic structures of capacitive sensors always use cylindrical fixed electrodes and the measurement for different diameter hole requires different specifications of sensor probe. For the shortfall of the measurement method for hole profile with capacitive sensor, this paper introduces the principle of capacitive sensor for micro/mini hole measurement and the capacitance-based device used in different diameter micro/mini holes’ profile measurement through the structural improvements of the capacitive sensor probe, then simulation and error analysis are conducted. The simulation results indicate the error is less than 5%, and it verifies the feasibility of the profile measurement principle for different diameter hole with capacitance sensor.
Analysis of Raman spectra of GeAsSe glass using different peak-fitting method
In order to understand the evolution of chemical structure in glasses, Raman features were fitted into different peakfitting functions, including Gaussian and Lorentzian types. It was found that, while single function was used for peakfitting, Gaussian function showed better fitted curves in overlapping bands than Lorentzian function, and Lorentzian function was more suitable for single broad band. On the other hand, while multiple functions were utilized to fit a vibrational peak, the results showed better matching between fitted curve and raw data. Therefore the Raman spectra were decomposed into different structural units. It was found that the evolution of different structural units was correlated with that of the physical parameters reported in literatures in a series of GeAsSe glasses. Therefore, it was concluded that the proposed method could be employed to decompose broad Raman spectra in amorphous materials so that the chemical structure of the material could be understood better.
A precision press-fit instrument for assembling small parts
Zhifeng Lou, Xiaodong Wang, Bo You, et al.
In the paper, a precision press-fit instrument for assembling small interference fitting parts is introduced, which includes pressing module and parts alignment module. The pressing module was used to clamp and position parts, and parts alignment module was used for the two parts’ alignment. Through analyzing press-fit control method, component alignment and adjustment strategy, and machine vision device calibration method, the instrument meets the pressing requirements of precision small components. Finite element method is used to predict the reasonable range of press-fit force, and pressing result of the instrument is tested by experiments.
Detection of arc fault based on frequency constrained independent component analysis
Kai Yang, Rencheng Zhang, Renhao Xu, et al.
Arc fault is one of the main reasons of electrical fires. As a result of weakness, randomness and cross talk of arc faults, very few of methods have been successfully used to protect loads from all arc faults in low-voltage circuits. Therefore, a novel detection method is developed for detection of arc faults. The method is based on frequency constrained independent component analysis. In the process of the method derivation, a band-pass filter was introduced as a constraint condition to separate independent components of mixed signals. In the process of the independent component separations, although the fault mixed signals were under the conditions of the strong background noise and the frequency aliasing, the effective high frequency components of arc faults could be separated by frequency constrained independent component analysis. Based on the separated components, the power spectrums of them were calculated to classify the normal and the arc fault conditions. The validity of the developed method was verified by using an arc fault experimental platform set up. The results show that arc faults of nine typical electrical loads are successfully detected based on frequency constrained independent component analysis.
Research on the relationship between the curvature and the sensitivity of curved PVDF sensor
Lu Shi, Yue Zhang, Weijie Dong
This paper studied the effect of curvature on the charge sensitivity of a curved PVDF sensor. The sensor was fabricated by attaching a PVDF film along the X-axis on a group of cylindrical silicon rods to form an outline with several bumps. The open output voltage of a curved sensor was simulated by using ANSYS with a rod curvature of 333 m-1, 400 m-1 and 500 m-1. It was found that the sensitivity was the highest when the curvature was 500 m-1, and the lowest when the curvature was 333 m-1. Curved PVDF sensors were fabricated and tested with a PVDF patch of 30 mm long and 28 μm thick and a radius of silicon rod of 3 mm, 2.5 mm and 2 mm, respectively. A shaker and mass block were used to apply the same dynamic force to the curved sensors and an oscilloscope was used to observe the output charge. The experiment results are not ideal but do show the same tendency as the simulation. The charge sensitivity increased as the curvature of substrate increased.
Optimal design of a touch trigger probe
Rui-Jun Li, Meng Xiang, Kuang-Chao Fan, et al.
A tungsten stylus with a ruby ball tip was screwed into a floating plate, which was supported by four leaf springs. The displacement of the tip caused by the contact force in 3D could be transferred into the tilt or vertical displacement of a plane mirror mounted on the floating plate. A quadrant photo detector (QPD) based two dimensional angle sensor was used to detect the tilt or the vertical displacement of the plane mirror. The structural parameters of the probe are optimized for equal sensitivity and equal stiffness in a displacement range of ±5 μm, and a restricted horizontal size of less than 40 mm. Simulation results indicated that the stiffness was less than 0.6 mN/μm and equal in 3D. Experimental results indicated that the probe could be used to achieve a resolution of 1 nm.
On chip micro stress test circuit for miniature component
Xiao-Dong Wang, Yong-Jian Qin, Yi Luo, et al.
Adhesive bonding is a popular assembly method for miniaturized component composed of parts with different materials. However, it also inevitably introduces assembly stresses in some stress-sensitive structures, which adversely influence the accuracy of the performance, as well as the long-term stability of the component. An on chip piezoresistive micro stress test circuit was designed and tested in this paper. Piezoresistors were fabricated by doping Boron to n-type silicon wafer. The sensitive structure on the micro part was a flexible beam which had a thickness of 50 μm. Silver epoxy adhesive and double epoxy adhesive were used in the assembly process and the stresses parallel and perpendicular to the flexible beam were calculated. The experimental results showed that silver epoxy adhesive introduced larger stress because the difference in thermal expansion coefficients between silver epoxy adhesive and silicon are larger than that of double epoxy adhesive. Aging tests were also carried out and 46 percent of stress on average was released in 100 days at room temperature. This preliminary work implied that the stress distribution of the sensitive structure at all stages of the assembly could be measured using on chip micro stress test circuit.
Measurement of centering error for probe of swing arm profilometer using a spectral confocal sensor
Lin Chen, Hongwei Jing, Zhongwei Wei, et al.
A spectral confocal sensor was used to measure the centering error for probe of swing arm profilometer (SAP). The feasibility of this technology was proved through simulation and experiment. The final measurement results was also analyzed to evaluate the advantages and disadvantages of this technology.
Front end design of smartphone-based mobile health
Changfan Zhang, Lingsong He, Zhiqiang Gao, et al.
Mobile health has been a new trend all over the world with the rapid development of intelligent terminals and mobile internet. It can help patients monitor health in-house and is convenient for doctors to diagnose remotely. Smart-phone-based mobile health has big advantages in cost and data sharing. Front end design of it mainly focuses on two points: one is implementation of medical sensors aimed at measuring kinds of medical signal; another is acquisition of medical signal from sensors to smart phone. In this paper, the above two aspects were both discussed. First, medical sensor implementation was proposed to refer to mature measurement solutions with ECG (electrocardiograph) sensor design taken for example. And integrated chip using can simplify design. Then second, typical data acquisition architecture of smart phones, namely Bluetooth and MIC (microphone)-based architecture, were compared. Bluetooth architecture should be equipped with an acquisition card; MIC design uses sound card of smart phone instead. Smartphone-based virtual instrument app design corresponding to above acquisition architecture was discussed. In experiments, Bluetooth and MIC architecture were used to acquire blood pressure and ECG data respectively. The results showed that Bluetooth design can guarantee high accuracy during the acquisition and transmission process, and MIC design is competitive because of low cost and convenience.
Surface profile measurement of microstructures with steep slopes by sample-titling strategy
Bin Xu, Wei Chen, Yubo Huang, et al.
A sample-titling strategy is proposed for the correction of the relative slope of microstructures and the scanning stylus during the surface profile measurement of microstructures with steep slopes. The correct surface profile of a measurement sample was reconstructed by data fusion of the probe trace, rotation angles of a sample and the motion of the scanner. Slope prediction and scanner control methods were also proposed to determine the rotation angle of a sample. Simulation was performed using a stylus with a tip of 2 μm and included angle of 90 degrees, and a trapezoid microstructure with a slope of 60 degrees to verify the feasibility of the proposed method. The measurement error of the proposed method is 0.31 μm while that of an existing scanning method is 4.50 μm in the simulation. Simulation results indicated that the proposed method could be used to increase the maximum detectable slope of a stylus profiling system and to reduce slope measurement errors as well.
Comparison between angle interferometer and angle encoder during calibration of autocollimator
An angle interferometer was set up using concept ‘ratio of two lengths’ and an angle encoder was set up using concept ‘subdivision of full circle (2π rad=360°)’ at the National Institute of Metrology, China (NIM). For the analysis of the systematic errors of each device, two autocollimator calibration systems were separately set up based on the angle interferometer and the angle encoder with a similar measuring uncertainty (around 0.1″). An autocollimator was calibrated using two systems in the same measurement range (±1000″) and the same measurement step (10″). The systematic errors of each system were found through comparison between their original calibration results. The compensation curves were calculated using the analysis results, and two systems’ original calibration results were compensated according to two systems’ compensation curves. The maximum difference between the compensated calibration results of two systems was 0.05″ which is lower than measuring uncertainty of each system.
Signal processing for single grating displacement measurement based on 3×3 coupler
Chunhua Wei, Shuhua Yan, Cunbao Lin, et al.
We present a compact displacement measurement system based on single grating and 3×3 coupler, possessing the capability of large range and nanometer precision. With the introduction of 3×3 coupler for phase shift in interference signal, the present scheme has the advantages of simple structure, convenient alignment, and insensitivity to air turbulence, resulting in high robustness. We accordingly developed an efficient and precision signal processing method for phase demodulation on a digital signal processing, adapting to characteristics of outputs in 3×3 coupler, achieving a high-powered subdivision of the interference phase. It was validated that the phase precision was about 1° even when phase and amplitude errors were added to interference signals in the simulation, which corresponded to a displacement precision of about 3nm.
A new method for generation of non-diffraction grating structured light with phase shift
Fangyuan Zhou, Liping Zhou, Long Xu, et al.
A new generation system for structured light is proposed here. This light has non-diffraction characteristic and is generated based on Mach-Zehnder interferometer together with optical wedge as the main optical element, which can realize phase shift easily. Theoretical analysis and ZEMAX simulation between the wedge angle and the strip phase shift are carried out. Experimental results show that the new structured light provided by this system has properties of long focal-depth, narrow strip-width, stable spatial sinusoidal density distribution and good contrast of fringe. The phase of the fringe can be shifted by adjusting the optical wedge’s position. The new structured light generated by this system has great advantages over traditional structured light on three-dimensional surface profile measurement which shows good application prospect.
Measurements of locomotive wheels using one-dimensional laser displacement sensor and eddy sensors
Weixing Xiong, Shuangyun Shao, Qibo Feng
The dynamic diameter measurement of locomotive wheels is important to ensure the vehicle safety. We propose that the diameter of locomotive wheels can be automatically determined by a one-dimensional displacement sensor and two eddy sensors which are installed on the inside rail. The distance between the laser displacement sensor and the wheels can be detected when the wheels pass through the center of the two eddy sensors. The diameter of wheels can be calculated. The experimental results show that the accuracy and repeatability can meet the need of measurement.
Design of transmitter and receiver for experimental blue-green laser communication system
Tao Xu, Xiaolu Chen, Dong Wen, et al.
An experimental blue-green laser communication system was developed using optical pulse position modulation (PPM) to study the feasibility of high-rate underwater communication among submerged objects. As a primary optical modulation means, PPM modulation is reviewed firstly. By comparison with other means, the conclusion was drawn that PPM has lower power requirement and it is a near optimal modulation for background-limited optical communications. For establishing laser beam propagating through the channel with modulated information through different pulse positions from the transmitter to the receiver, the transmitter subsystem and the receiver subsystem are developed and the key techniques are described separately in detail. Results indicated that the whole blue-green communication system was compact, efficient, reliable and inexpensive, and achieved a high-speed rate communication up to megabits per second and a reasonably low error rates.
indirect measurement of machine tool motion axis error with single laser tracker
Zhaoyong Wu, Liangliang Li, Zhengchun Du
For high-precision machining, a convenient and accurate detection of motion error for machine tools is significant. Among common detection methods such as the ball-bar method, the laser tracker approach has received much more attention. As a high-accuracy measurement device, laser tracker is capable of long-distance and dynamic measurement, which increases much flexibility during the measurement process. However, existing methods are not so satisfactory in measurement cost, operability or applicability. Currently, a plausible method is called the single-station and time-sharing method, but it needs a large working area all around the machine tool, thus leaving itself not suitable for the machine tools surrounded by a protective cover. In this paper, a novel and convenient positioning error measurement approach by utilizing a single laser tracker is proposed, followed by two corresponding mathematical models including a laser-tracker base-point-coordinate model and a target-mirror-coordinates model. Also, an auxiliary apparatus for target mirrors to be placed on is designed, for which sensitivity analysis and Monte-Carlo simulation are conducted to optimize the dimension. Based on the method proposed, a real experiment using single API TRACKER 3 assisted by the auxiliary apparatus is carried out and a verification experiment using a traditional RENISHAW XL-80 interferometer is conducted under the same condition for comparison. Both results demonstrate a great increase in the Y-axis positioning error of machine tool. Theoretical and experimental studies together verify the feasibility of this method which has a more convenient operation and wider application in various kinds of machine tools.
Implementation of total focusing method for phased array ultrasonic imaging on FPGA
JianQiang Guo, Xi Li, Xiaorong Gao, et al.
This paper describes a multi-FPGA imaging system dedicated for the real-time imaging using the Total Focusing Method (TFM) and Full Matrix Capture (FMC). The system was entirely described using Verilog HDL language and implemented on Altera Stratix IV GX FPGA development board. The whole algorithm process is to: establish a coordinate system of image and divide it into grids; calculate the complete acoustic distance of array element between transmitting array element and receiving array element, and transform it into index value; then index the sound pressure values from ROM and superimpose sound pressure values to get pixel value of one focus point; and calculate the pixel values of all focus points to get the final imaging. The imaging result shows that this algorithm has high SNR of defect imaging. And FPGA with parallel processing capability can provide high speed performance, so this system can provide the imaging interface, with complete function and good performance.
Development of a scanning touch probe with 5-axis measuring functions
Chih-Liang Chu, Kuan-Wen Lai, Hung-Chi Chen
The purpose of this study is to develop a five-axis scanning touch probe with high precision and low contact force. The development of scanning touch probe is consisted of three parts: mechanism design, optical path design, and rotation structure design. The mechanism design contains three parts, Z-axis system, XY-axis system, and probe mechanism. The Z-axis system applies the characteristic of the thin sheet spring to move vertically. In the design of XY-axis system, a micro-beam is employed, through which length, width, and thickness of the micro-beam and corresponding dimensions of the leaf spring are designed according to the selected contact force. The freedom degree is limited to three. And the center of the mechanism is equipped with a stylus to inhibit displacement of the Z-axis. The contact between the probe and the work piece only leads to change in the angles of X- and Y-axes, achieving the feature of 2-degree freedom. To enable rapid change for the probes, this study designs a probe mechanism, reliability of which is analyzed and validated with ANSYS software, so that the design of 3-degree freedom mechanism is completed. The sensor has a laser diode to coordinate with Position Sensor Detector (PSD) which works with the optical path designed to measure placement of Z-axis and angle placement of XY-axis. The rotation structure refers to the principle of 5-axis machining design, and the two rotary axes (A- and C-axis) to join the self-developed scanning probe. This design can achieve independent measurements and eliminate the dynamic measurement error that three-axis scanning systems typically have. By validation through an experiment, the three-dimensional scanning touch probe developed by this study has a measuring range of ±1mm×±1mm×1mm, and unidirectional repeatability of 0.6μm.
Study on precision spatial measurement network of EAST
Chen Liu, Yongqi Gu, Yuanyang Zheng, et al.
A precision spatial measurement network for EAST was studied and established base on the EAST configuration and Laser Tracker system. 34 fiducials in outside network and 64 fiducials in inside network were united in one cylindrical coordinate by a laser tracker system. Unified Spatial Metrology Network (USMN) analysis showed that the single point average uncertainty of this measurement network was about 0.2mm, which can meet the measurement accuracy requirements of EAST. A combination measurement method with a laser tracker system and measurement arm was used for the assembly process of EAST device and some researches of environmental temperature influence have been done to improve the measurement process.
Theoretical study and experimental verification on calculation of bearing capacity of aerostatic restrictor system with a gas-impedance model
Yang Cheng, Dongsheng Li, Jiacheng Hu, et al.
Bearing capacity is a most significant parameter to evaluate the quality of aerostatic restrictor system. A gas-impedance model was established using the theory of gas dynamics to determine the bearing capacity of three aerostatic restrictor systems which were multi-micro channel, dual U-shaped and dual circle-shaped aerostatic restrictor system respectively. Experiments were run using gas-impedance method and finite difference method to prove the validity of gas-impedance method. Experimental results indicated the gas-impedance model method was effective in establishing the bearing capacity of aerostatic restrictor system.
Complex shape product tolerance and accuracy control method for virtual assembly
Huiping Ma, Yuanqiang Jin, Xiaoguang Zhang, et al.
The simulation of virtual assembly process for engineering design lacks of accuracy in the software of three-dimension CAD at present. Product modeling technology with tolerance, assembly precision preanalysis technique and precision control method are developed. To solve the problem of lack of precision information transmission in CAD, tolerance mathematical model of Small Displacement Torsor (SDT) is presented, which can bring about technology transfer and establishment of digital control function for geometric elements from the definition, description, specification to the actual inspection and evaluation process. Current tolerance optimization design methods for complex shape product are proposed for optimization of machining technology, effective cost control and assembly quality of the products.
Improved LMD algorithm based on extraction of extrema of envelope curve
Local mean decomposition (LMD) is a time-frequency analysis approach to deal with complex multi-frequency signal. However, as the decomposition process is sensitive to noise, there is a distinct limit when it is applied to analysis of the vibration signals of machinery with serious background noise. An improved LMD algorithm based on extracting the extrema of envelope curve is put forward to reduce the influence of high-frequency noise effectively. To verify its effect, three different de-noising methods, i.e., band-pass filter method, wavelet method and lift wavelet method are used, respectively. And the comparison result of the 4 methods shows that the proposed method has satisfactory reproducibility. Then the new algorithm is applied to real bearing signal, and experimental results show that it is effective and reliable. The method also has certain significance for the subsequent eigenvector research in intelligent fault diagnosis.
Design and development of measuring device for beam pointing and positional errors in multi-axes laser interferometric systems
Pengcheng Hu, Yifei Zhang, Ting Wu, et al.
The mechanism of Abbe error and cosine error resulting from beam pointing and positional errors in a laser interference measurement system was analyzed, a PSD-based measurement method was proposed to measure both errors simultaneously. A light intensity adaptive measuring device was designed for measurement of pointing and positional errors. Experimental results indicated that the measuring range and resolution of the position deviation could reach ±4.5mm and 1μm respectively; the angular range and resolution could reach ±0.112rad and 25μrad.
Relaxation matching algorithm for moving photogrammetry
Lei Guo, Ke Liu, Yinxiao Miao, et al.
Moving photogrammetry is an application of close range photogrammetry in industrial measurement to realize threedimensional coordinate measurement within large-scale volume. This paper describes an approach of relaxation matching algorithm applicable to moving photogrammetry according to the characteristics of accurate matching result of different measuring images. This method uses neighborhood matching support to improve the matching rate after coarse matching based on epipolar geometry constraint and precise matching using three images. It reflects the overall matching effect of all points, that means when a point is matched correctly, the matching results of those points round it must be correct. So for one point considered, the matching results of points round it are calculated to judge whether its result is correct. Analysis indicates that relaxation matching can eliminate the mismatching effectively and acquire 100% rate of correct matching. It will play a very important role in moving photogrammetry to ensure the following implement of ray bundle adjustment.
Current ways and means for reduction or elimination of periodic nonlinearity in heterodyne interferometer
Peng Chen, Peng-cheng Hu, Xue-mei Ding, et al.
This paper reviews ways and means used for reduction or elimination of periodic nonlinearity in heterodyne interferometers. The periodic nonlinearity resulting from polarization mixing or frequency mixing in heterodyne interferometers was modeled into one expression, which included the initial polarization state of the laser source, the rotational alignment of the beam splitter along with different transmission coefficients for polarization states and the rotational misalignment of a receiving polarizer. Three compensation techniques, measuring two orthogonal output signals, Lissajous Compensation and Chu-Ray Algorithm, are described and discussed for reduction of periodic nonlinearity. These algorithms needed at least one fringe of motion or a constant velocity sweep to properly correct the motion. And five types of two spatially separated beam interferometer configurations are described and discussed for elimination of periodic nonlinearity to a picometer level. It is concluded that the main disadvantage of these configurations was their complex architecture with unbalanced long beam paths.
Simulation analysis of position error of parabolic trough concentrator mirror installation
Guo-liang Tian, Bi-xi Yan, Mingli Dong, et al.
The research showed the simulation of position error when assembling a reflective mirror of parabolic trough concentrator. The shape of a reflective mirror is like a parabolic cylinder model, relying on the back of the four-point mounted on a special setup, making it unable to move. Therefore, it is of great importance of the machining precision of special bracket. We need to analyze the influence of reflective mirror‘s intercept factor in order to guide the processing precision. It is assumed that each reflective mirror is rigid, we have calculated the intercept factor of reflector with mounting points’ random error of different standard deviation, comparing the simulating results with TRACEPRO. As a sequence, we can approve the feasibility of the algorithm, and give the effect of different random errors on the light-gathering efficiency. On the basis, we provide the machining accuracy of bracket. The simulation results show that when the mounting points’ standard deviation of position error is less than 0.5 mm, the intercept factor of receiver has reached upwards of 92% with 60 mm diameter for receiver, which can satisfy the design requirements.
Control methods of improving tracking precision
Hua Liu, Yinxiao Miao, Ke Liu
The stabilization and tracking line-of-sight with high accuracy is the chief specification and key function of the optic-electronic sight stabilization platform and it has an effect on the performance of loading equipment. The high-speed target is tracked with the shipboard azimuth and pitch optoelectronic platform. The compound-axis tracking servo control technique , the stabilization mirror system and the methods that compensates the azimuth by the rolling angle rate of motion carrier are used. The practice shows that the shipboard azimuth and pitch opto-electronic platform can realize high tracking precision.
Alignment methods for partial compensating lens of aspheric testing in a non-null interferometer
Tu Shi, Yongying Yang, Lei Zhang, et al.
Careful alignment of optical elements is essential in interferometric tests. Misalignments of the key element largely influence the testing accuracy. For aspheric figure error testing, non-null tests achieve more flexible and economical measurements than the null ones. However, retrace error is induced due to the violation of null configuration, making the alignment difficult. In aspheric partial compensation testing, the partial compensating lens (PCL) as the key component needs careful adjustment. The aplanat alignment method is effective for the PCL adjusting with high accuracy employing a removable lens, which combined with the PCL as an aplanat. But its structure is complex. After describing this method, a PCL computer-aided alignment (CAA) method is posed basing on system modeling in a ray tracing software. The structure is simplified with computer calculations. The PCL tilt and decentration are easily aligned with a plane and a standard spherical mirror respectively, according to linear relations with wavefront coma aberrations on the detector. Alignment of the PCL was implemented with these two methods in an aspheric partial compensation testing experimental apparatus. Adjustment and aspheric testing results were presented in order. The CAA method is a generalized approach with simpler structure, while the aplanat alignment method is easy to carry out and suitable for industrial application.
Multiple-grating self-correcting algorithm for processed mark measurement error
When substrate is processed, also any measurement grating marks available on the substrate will be influenced: they will be deformed asymmetrically, which gives rise to a measurement-shift error when measuring such a grating mark. To measure on a processed mark, an algorithm is used. This algorithm describes a method to calculate the weight factor of the information from each order. The weight factors of such an algorithm are based on a model which describes the measurement position as a function of the diffraction orders and the mark position. This paper proposes an algorithm for finding these weight factors, and the feasibility of the method is validated through simulation.
A high-resolution detecting system based on machine vision for defects on large aperture and super-smooth surface
Yongying Yang, Limin Zhao, Shitong Wang, et al.
The high-resolution detecting system based on machine vision for defects on large aperture and super-smooth surface uses a novel ring telecentric lighting optical system detecting the defects on the sample all round and without blind spots. The scattering light induced by surface defects enters the adaptive and highly zoom microscopic scattering dark-field imaging system for defect detecting and then forms digital images. Sub-aperture microscopic scanning sampling and fast stitching on the surface is realized by using precise multi-axis shifting guided scanning system and a standard comparison board based upon binary optics is used to implement fast calibration of micron-dimension defects detected actually. The pattern recognition technology of digital image processing which can automatically output digitalized surface defects statements after scaling is established to comprehensively evaluate defects. This system which can reach micron-dimension defect resolution can achieve detections of large aperture components of 850 mm × 500 mm, solve the durable problem of subjective uncertainty brought in by human visual detection of defects and achieve quantitative detection of defects with machine vision.
Application of deadbeat control with constraint and non-ripple in precision rapid displacement system
In order to enable the output response of a precision rapid displacement system to rapidly track the input instructions, and solve the problem of excessive control amplitude in the shortest period of time, deadbeat control with constraint and non-ripple can be used to enhance the system response rate under the constraint. Simulation results show that the steady-state step signal tracking error of a system can reach ±1.5μm under random disturbance, and the step response is rapid and accurate. Compared with general control strategies, this method has a digital control design to increase the speed of response, the fine anti-disturbance ability, and the potential for wide application.
Vision-based on-machine measurement for CNC machine tool
Ruixue Xia, Jiang Han, Rongsheng Lu, et al.
A vision-based on-machine measurement system (OMM) was developed to improve manufacturing effectiveness. It was based on a visual probe to enable the CNC machine tool itself to act as a coordinate measuring machine (CMM) to inspect a workpiece. The proposed OMM system was composed of a visual probe and two software modules: computer-aided inspection planning (CAIP) module and measurement data processing (MDP) module. The auto-focus function of the visual probe was realized by using astigmatic method. The CAIP module was developed based on a CAD development platform with Open CASCADE as its kernel. The MDP module includes some algorithms for determination of inspection parameters, for example, the chamfered hole was measured through focus variation. The entire system was consequently verified on a CNC milling machine.
Error mechanism analyses of an ultra-precision stage for high speed scan motion over a large stroke
Reticle Stage (RS) is designed to complete scan motion with high speed in nanometer-scale over a large stroke. Comparing with the allowable scan accuracy of a few nanometers, errors caused by any internal or external disturbances are critical and must not be ignored. In this paper, RS is firstly introduced in aspects of mechanical structure, forms of motion, and controlling method. Based on that, mechanisms of disturbances transferred to final servo-related error in scan direction are analyzed, including feedforward error, coupling between the large stroke stage (LS) and the short stroke stage (SS), and movement of measurement reference. Especially, different forms of coupling between SS and LS are discussed in detail. After theoretical analysis above, the contributions of these disturbances to final error are simulated numerically. The residual positioning error caused by feedforward error in acceleration process is about 2 nm after settling time, the coupling between SS and LS about 2.19 nm, and the movements of MF about 0.6 nm.
Performance analysis and experiment validation of a pneumatic vibration isolator
A performance analysis and experiment validation of a pneumatic vibration isolator (PVI) that applied in the wafer stage of lithography is proposed in this work. The wafer stage of lithography is a dual-stage actuator system, including a long-stroke stage (LS) and a short-stroke stage (SS). In order to achieve the nanometer level positioning the isolator is designed to reduce the transmission of LS excitations to SS. In addition, considering the SS with six degrees of freedom and required to keep a strict constant temperature environment, the isolator need to have two functions, including the decoupling for vertical to horizontal and gravity compensation. In this isolator, a biaxial hinge was designed to decouple vertical rotation freedom, and a gas bearing was designed to decouple horizontal motion. The stiffness and damping of the pneumatic vibration isolator were analyzed. Besides, an analysis of the natural frequency and vibration transmissibility of the isolator is presented. In the end, the results show that vibration transmission is reduced significantly by the isolator and natural frequency can be lower than 0.6 Hz. This means that experimental results accord with the prediction model.
Precisely connected and calculated algorithm of punctate scratches in the super-smooth surface defects evaluation system
Chen Li, Yongying Yang, Pin Cao, et al.
In the inertial confinement fusion system (ICF), surface scratches of the large diameter optical surface appear as dot lines (punctate scratches). This kind of scratches is only detected under a high microscope magnification system. This can be caused by the blemishes on the optical processing technology and shallow scratches (< 25nm ). As a result, it can have an impact on the relevant calculation of the width and length of the scratches. Besides, this kind of scratches has a serious impact on the ICF, such as system damage. To solve this problem, this paper proposes the image pattern charter of punctate scratches based on the existing surface defects detection system (SDES). Finally, it proposes an algorithm of scratches based on the linearity differential detection and connectivity. That is, using coordinate transformation and direction differential-threshold discrimination, the scratches can be connected effectively and calculated exactly. Experimental results show that punctate scratches parts can be connected correctly, and the accuracy of the calculated length reaches 95%. Also, the improved algorithm applies to the arc-shaped scratches, which is based the block image processing. Currently, this algorithm can be applied to connect and calculate the shallow scratches accurately and precisely on large fine optics in the ICF system. Thus it can also decrease the misdetection rate of nonconforming super-smooth optics in the ICF system.
Laser confocal measurement system for curvature radius of lenses based on grating ruler
Jiwei Tian, Yun Wang, Nan Zhou, et al.
In the modern optical measurement field, the radius of curvature (ROC) is one of the fundamental parameters of optical lens. Its measurement accuracy directly affects the other optical parameters, such as focal length, aberration and so on, which significantly affect the overall performance of the optical system. To meet the demand of measurement instruments for radius of curvature (ROC) with high accuracy in the market, we develop a laser confocal radius measurement system with grating ruler. The system uses the peak point of the confocal intensity curve to precisely identify the cat-eye and confocal positions and then measure the distance between these two positions by using the grating ruler, thereby achieving the high-precision measurement for the ROC. The system has advantages of high focusing sensitivity and anti-environment disturbance ability. And the preliminary theoretical analysis and experiments show that the measuring repeatability can be up to 0.8 um, which can provide an effective way for the accurate measurement of ROC.
Improving signal-to-noise ratio and reducing noise equivalent radiance of electro-optical systems sensor by binning image pixels
Xiansheng Li, Jian-wei Ren, Zhi Wan, et al.
The signal-to-noise ratio (SNR) and noise equivalent radiance (NER) are important characteristics of an electro-optical systems sensor. A new method to improve the system’s SNR and reduce the NER was studied by analyzing the radiometric calibration data of the system. An image was obtained, when the system was illuminated by the uniform light source outputting from integrating sphere. The adjourn pixels were binned by n×n pixels (n=2, 3, 4, 5) in this image. And the digital numbers of binning pixels were added together. The new images were achieved. With 5×5 pixels binned, the SNR increased from 165.7 up to 842.3, which is improved almost 5 times. At the same time, the NER decreased from 0.077(W/m2/sr) to 0.015(W/m2/sr), which is declined by nearly 5 times. With the binning pixels up to n×n, the SNR and NER were enhanced and decreased almost by n times, respectively.
Accuracy analysis of phase retrieval using Fourier transform method
Beibei Liu, Yingjie Yu, Wenjing Zhou, et al.
Phase retrieval based on the transport of intensity equation (TIE) is a non-interferometric and quantitative technique for phase reconstruction which has been applied to many fields of physics. The TIE expresses the relationship between the object-plane phase and the axial intensity derivative in the Fresnel region for coherent and partially coherent fields and there have been many methods to solve it. In this paper, the Fourier transform method that was an approximate but a widely used solution to the TIE was studied. The concrete steps of the solution were given and two simulations were performed to study the influence of the intensity on the phase retrieval accuracy. Finally, a fiber was selected as the sample to reconstruct its phase using Fourier transform method in practice and the phase was retrieved with acceptable accuracy.
Analytical beam-width characteristics of distorted cat-eye reflected beam
The analytical expression of beam-width of distorted cat-eye reflected beam under far-field condition is deduced using the approximate three-dimensional analytical formula for oblique detection laser beam passing through cat-eye optical lens with center shelter, and using the definition of second order moment, Gamma function and integral functions. The laws the variation of divergence angle and astigmatism degree of the reflected light with incident angle, focal shift, aperture size, and center shelter ratio are established by numerical calculation, and physical analysis. The study revealed that the cat-eye reflected beam is like a beam transmitted and collimated by the target optical lens, and has the same characteristics as that of Gaussian beam. A proper choice of positive focal shift would result in a divergence angle smaller than that of no focal shift. The astigmatism is mainly caused by incidence angle.
Multifocal axial confocal microscopic scanning with a phase-only liquid crystal spatial light modulator
Li Min Zou, Ming Shu Pang, Meng Jiao Zhou, et al.
Aiming at the shortcomings of mechanical scanning methods, non-mechanical scanning method is proposed. A zoom illuminating lens which has multiple focal points is realized by introducing Liquid Crystal Spatial Light Modulator (LC-SLM) into the confocal illumination light path, and thus it produces the multifocal zoom lens axially. The axial optical sectioning in a conventional confocal microscope is achieved by beam scanning rather than mechanically moving the objective lens, which enhances the capacity of chromatography and improves the scanning speed with greater accuracy. To generate and shift the multiple axial focal points, the modulation phase bitmaps of LC-SLM is changed. Simulation results further show that multifocal axial confocal beam scanning replacing mechanical scanning can therefore be implemented.
The least square optimization in image mosaic
Image registration has been a hot research spot in the computer vision technology and image processing. Image registration is one of the key technologies in image mosaic. In order to improve the accuracy of matching feature points, this paper put forward the least square optimization in image mosaic based on the algorithm of matching similarity of matrices. The correlation coefficient method of matrix is used for matching the module points in the overlap region of images and calculating the error between matrices. The error of feature points can be further minimized by using the method of least square optimization. Finally, image mosaic can be achieved by the two pair of feature points with minimized residual sum of squares. The experimental results demonstrate that the least square optimization in image mosaic can mosaic images with overlap region and improve the accuracy of matching feature points.
Experiment study on the characteristics of two-dimensional line scale working standard
National working standard of two-dimensional line scale based on laser two-coordinate standard device was set up to solve the problem of the calibration and traceability of 2-D line scale optical standard and high precision photomask. The operating principle and system composition of the working standard device were introduced. The characteristics were test in special experiments. A high precision differential laser interferometer system was used for a length standard, a high magnification optical microvision system was used for precision optical positioning feedback. In order to improve the measuring accuracy, several high precision sensors were installed to measure environmental parameters for compensating the laser wavelength in atmosphere according to the empirical Edlén equation. High resolution CCD modeling and calibrating based on two-dimensional nanoscale positioning movable platform and laser interferometer were adopted to improve the pointing accuracy. Two-dimensional line scale working standard could be used to measure line spacing, point spacing, and coordinates of 2-D optical standard or photomask, with measurement range 300mm × 300mm, measurement uncertainty U=(0.1~0.3)μm, k=2. Some experiments were carried out to identify the characteristics of length measurement error, probing error, measurement repeatability and measurement reproducibility of the working standard, and measurement uncertainty was validated by the measurement experiments.
Study on controllable LC-micro blazed grating beam deflector in free space
Junbo Yang, Suzhi Xu, Jingjing Zhang, et al.
A liquid crystal (LC) beam deflector with a microblazed grating produced by stepping photolithography and reactive ion etching (RIE) was reported. A homogeneously aligned nematic liquid crystal (NLC) materials are filled inside the microcavity of blazed grating, and sandwiched between two glass plates. An indium tin oxide (ITO) transparent electrode is deposited on it to provide the beam steering capability. Our LC-micro blazed grating device gives a high diffractive efficiency (about 95%) and a controllable large steering angle over 7.2° (for ne) and 1.7° (for no), respectively. It was found that this type of non-mechanical beam steering without any moving parts is ideally suited for applications in optical communication and optical interconnection network.
The detection of wheelflats based on fiber optic Bragg grating array
Qiushi Mi, Xiaorong Gao, Hongna Zhu, et al.
During the long-time working circle, the wheels will be damaged to a certain degree caused by the wearing, the impact, the loads, the climate and so on. In order to evaluate the health of the wheels and reduce the potential losses, many effective methods are used in railway health monitoring, such as laser method or ultrasonic method. But few of them can reach the demand of the real-time online detection, and integrate more comprehensive inspection function at the same time. A composite detection scheme for wheel-tread defects based on FBG sensing technique has been investigated in this paper. By collecting and analyzing the data from the sensors which are distributed on tracks and rails, we can precisely evaluate the Wheel-flats and also measure some other parameters used in rail health monitoring scheme such as speed, loads and axle counting measurement.
Calibration of a high precision rotary table
Heyan Wang, Zi Xue, Ni Shen, et al.
In order to calibrate a high precision rotary table, a calibration system was established to measure the position error and repeatability of rotary table. The position error was measured with a polygon, an index table and an autocollimator to separate the angular error of the polygon from the position error of the rotary table, and the position error of rotary table was calculated using least square method. The rotary table was compensated and calibrated with the position error measured. The repeatability of the rotary table established through 10 times full circle rotations was 0.02 arc second. The measurement results indicated that the combination calibration method was suitable for the calibration of a high precision rotary table. It was found through the analysis that the angular measurement uncertainty was 0.08 arc second.
Altazimuth mount based dynamic calibration method for GNSS attitude measurement
Nan Jiang, Tao He, Shaohua Sun, et al.
As the key process to ensure the test accuracy and quality, the dynamic calibration of the GNSS attitude measuring instrument is often embarrassed by the lack of the rigid enough test platform and an accurate enough calibration reference. To solve the problems, a novel dynamic calibration method for GNSS attitude measurement based on altazimuth mount is put forward in this paper. The principle and implementation of this method are presented, and then the feasibility and usability of the method are analyzed in detail involving the applicability of the mount, calibrating precision, calibrating range, base line rigidity and the satellite signal involved factors. Furthermore, to verify and test the method, a confirmatory experiment is carried out with the survey ship GPS attitude measuring instrument, and the experimental results prove that it is a feasible way to the dynamic calibration for GNSS attitude measurement.
Ranging algorithm based on process measurement for low-altitude radio fuzes
Xiaolu Chen, Tao Xu, Biao Chen, et al.
A ranging algorithm based on process measurement was proposed for low-altitude radio fuzes with wide range of action and low request of absolute ranging precision. For those particular applications, a conception of relative burst height was given to control the initiation point of a fuze instead of the absolute burst height. The received echo power was analyzed and its relationship with the relative burst height was derived. The basic principle and implementation of the ranging algorithm were discussed and the simulation results were given including anti-white Gaussian noise performance and anti-active jamming performance. The results proved the feasibility of the ranging algorithm based on process measurement. It could be used to help the further researches of low altitude radio fuzes.
Development of a high accurate gear measuring machine based on laser interferometry
Hu Lin, Zi Xue, Guoliang Yang, et al.
Gear measuring machine is a specialized device for gear profile, helix or pitch measurement. The classic method for gear measurement and the conventional gear measuring machine are introduced. In this gear measuring machine, the Abbe errors arisen from the angle error of guideways hold a great weight in affection of profile measurement error. For minimize of the Abbe error, a laser measuring system is applied to develop a high accurate gear measuring machine. In this laser measuring system, two cube-corner reflectors are placed close to the tip of probe, a laser beam from laser head is splited along two paths, one is arranged tangent to the base circle of gear for the measurement of profile and pitch, another is arranged parallel to the gear axis for the measurement of helix, both laser measurement performed with a resolution of 0.3nm. This approach not only improves the accuracy of length measurement but minimize the Abbe offset directly. The configuration of this improved measuring machine is illustrated in detail. The measurements are performed automatically, and all the measurement signals from guide rails, rotary table, probe and laser measuring system are obtained synchronously. Software collects all the data for further calculation and evaluation. The first measurements for a gear involute artifact and a helix artifact are carried out, the results are shown and analyzed as well.
Calibration of industrial CT using two forest-balls
A small forest-ball was manufactured and calibrated using CMM F25. An industrial CT called Metrotom1500 was calibrated by the small forest-ball and another big forest-ball produced by Carl Zeiss. These two forest-balls were separately measured at two different magnifications of the industrial CT, and the measurement results could meet the maximum permissible error of Metrotom1500.
Characteristics of coated long-period fiber grating based on mode transition and dual-peak resonance
The mode transition of high-order cladding modes in a coated long-period fiber grating (LPFG) was studied using coupled-mode theory, the response characteristic of cladding mode effective index was analyzed with increasing overlay thickness. It was found through analyses that the shift of resonant wavelength in the mode transition region was larger than that in the non-mode transition region. Further more, the phase-matching curves for 19th cladding mode was investigated when the overlay thickness was located in the mode transition and non-mode transition regions, the shift between two resonance wavelengths of dual peak in the mode transition region was bigger than that in non-transition mode region. The response characteristics of film refractive index of coated LPFG was investigated for a high-order cladding mode while the overlay thickness was located in mode transition and non-transition mode regions, the positions and amplitudes of the dual peak of the high-order cladding mode had different changes when the film refractive index vary slightly. The sensor sensitivity was defined and calculated. The result shows that the sensitivity of film refractive index could reach 69.12 and 0 respectively, when the overlay thickness was located in mode transition and non-mode transition regions. The corresponding resolutions of film refractive index can be available to 10-7 in mode transition region.
Static and dynamic property experiments of giant magnetostrictive material-fiber Bragg grating magnetic field sensors
Guoping Ding, Jiayi Liu, Bin Gao, et al.
Nowadays, there are many kinds of magnetic field sensors such as Hall sensor, Gauss meter and so on. But few of them can be used in the small air gaps which size is about millimeter. A thin-slice Giant Magnetostrictive Material-fiber Bragg grating (GMM–FBG) magnetic field sensor was proposed with the size of 14mm×7mm×1.5mm. The FBG was bonded along the GMM slice length orientation, perpendicular to the major magnetostriction orientation, to measure the GMM’s strain caused by external magnetic field. Experiment systems were established to test the GMM–FBG sensor’s static and dynamic properties. The results show that the sensor’s static property is consistent with the theoretical prediction, and the dynamic response is feasible in low frequencies from 1Hz to 20Hz.
Development of ultra-precision centering and leveling turntable using aerostatic bearing technology
Maosheng Hou, Yanrong Tian, Lin Ji, et al.
To perform the ultra-precision centering and leveling operation of large surface under test in optical and mechanical precision measurements, a novel automatic centering and leveling turntable based on the aerostatic bearing technology is developed. In the functional module of centering, a planar aerostatic bearing and two micro-displacement actuators are utilized to achieve centering operation, and in the leveling functional module, a spherical aerostatic bearing, two microdisplacement actuators and a spring pivot are employed to realize the leveling operation. In the paper, the mathematical models of centering and leveling operation are obtained using coordinate transformation, and coupling between the centering and leveling operation is also analyzed. Furthermore, by using distance-measuring interferometer and autocollimator, the resolutions of centering and leveling operation are measured. Finally, errors of the centering and leveling operation are analyzed and the performance evaluation of the turntable is given. The experimental results show that, with 50Kg load, the leveling operation resolution is better than 1.2″; leveling operation range is ±1°; the centering operation resolution is better than 0.05μm; centering operation range is about ±5mm. The developed turntable can satisfy the requirements of ultra-precision, high resolution, wide range, frictionless, high load stiffness, stabilization and small driving force.
A voice coil motor based measuring force control system for tactile scanning profiler
Shengdong Feng, Xiaojun Liu, Liangzhou Chen, et al.
In tactile scanning profiler, the measuring force would change in a wide range when it was used for profile measurement in a large range, which could possibly destroy the measured surface. To solve the problem, measuring force control system for tactile scanning profiler was needed. In the paper, a voice coil motor-based measuring force control system for tactile scanning profiler was designed. In the design, a low stiffness coefficient spring was used to provide contact force, while a voice coil motor (VCM) to balance the spring force so that the contact force could be kept for constant measuring force. A VCM was designed specially, and for active measuring force control, a precision current source circuit under the control of a DSP unit was designed to drive the VCM. The performance of voice coil motor based measuring force control system had been tested, and its good characteristics were verified.
A vertical scanning positioning system with large range and nanometer resolution for optical profiler
Qian Li, Xiaojun Liu, Zili Lei, et al.
Piezoelectric ceramics with a flexible hinge guide was used for fine positioning at nanometer level, while a stepping motor was used for coarse positioning with a resolution at micrometer level, and their combination helped fulfillment of vertical scanning positioning with large range and nanometer resolution. A grating sensor was used for the real-time measurement of scanning displacement for close-loop positioning control. The properties of the flexible hinge guide was analyzed using ANSYS. Experimental results indicated the performance of the system was good. The system had a good application prospect in an optical profiler for surface measurement.
Image inpainting for the differential confocal microscope
In the process of zero-crossing trigger measurement of differential confocal microscope, the sample surface features or tilt will cause the edges can't be triggered. Meanwhile, environment vibration can also cause false triggering. In order to restore the invalid information of sample, and realize high-precision surface topography measurement, Total Variation (TV) inpainting model is applied to restore the scanning images. Emulation analysis and experimental verification of this method are investigated. The image inpainting algorithm based on TV model solves the minimization of the energy equation by calculus of variations, and it can effectively restore the non-textured image with noises. Using this algorithm, the simulation confocal laser intensity curve and height curve of standard step sample are restored. After inpainting the intensity curve below the threshold is repaired, the maximum deviation from ideal situation is 0.0042, the corresponding edge contour of height curve is restored, the maximum deviation is 0.1920, which proves the algorithm is effective. Experiment of grating inpainting indicates that the TV algorithm can restore the lost information caused by failed triggering and eliminate the noise caused by false triggering in zero-crossing trigger measurement of differential confocal microscope. The restored image is consistent with the scanning result of OLYMPUS confocal microscope, which can satisfy the request of follow-up measurement analysis.
Distributed compressive sensing of light field
Rui Lei, Wei Shen, Zhi-jiang Zhang, et al.
The light field camera array can be regarded as distributed source. The image sequence captured by a camera array contains the inter-correlation and intra-correlation. In order to utilize the correlation, a joint sparsity model was established to combine the light field with distributed compressive sensing, and a recovery algorithm was proposed for the model -- simultaneous regularized orthogonal matching pursuit algorithm (SROMP), which uses the correlation to reconstruct the light field image sequences. Several light field images could be approximate at once using different linear combinations of elementary signals. Experimental results show that SROMP algorithm could be used to achieve high accuracy reported in the literatures.
Experimental study on absolute measurement of spherical surfaces with shift-rotation method based on Zernike polynomials
Weihong Song, Xi Hou, Fan Wu, et al.
Absolute testing methods have been widely employed in the accurate metrology of optical surface deviation. As a general method, the shift-rotation method requires several rotations and translations of the surface under test. And the surface deviation of the reference and the surface under test can be both calculated in terms of Zernike polynomials. The validity of the shift and rotation procedure was proved through experiments. Two different transmission spheres (with the same F number but different quality of the reference surfaces) were used to test the same spherical surface under test. The test results of the spherical surface under test are in good agreement.
Coarse-fine vertical scanning based optical profiler for structured surface measurement with large step height
Yi Zheng, Xiaojun Liu, Zili Lei, et al.
White light interference (WLI) optical profiler had been used widely for structured surface measurement. To achieve high measuring accuracy, piezoelectric ceramic (PZT) was usually used as the vertical scanning unit, which was normally less than 100um and only for small range structured surface measurement. With the development of advanced manufacturing technology, precision structured surfaces with large step height were appearing. To satisfy the measurement requirements of this kind of precision structured surfaces, WLI optical profiler with large range had to be developed. In this paper, an optical profiler was proposed, in which a coarse-fine vertical scanning system was adopted to expand its measurement range to 10mm while its resolution still at nanometer level.
Data communication between Panasonic PLC and PC using SerialPort control in C#.NET environment
With the gradual promotion of Microsoft.NET platform, C# as an object-oriented programming language based on the platform has been widely used. Therefore, more attention is concentrated on how to achieve the communication between Panasonic PLC and PC efficiently and fast in C#.NET environment. In this paper, a method of using SerialPort control which could be used for achieving communication between PLC and PC is introduced. Meanwhile, the reason of abnormal thread when displayed the receiving data in form is analyzed and the programming method to solve the problem of thread safety is designed. Achieving the communication of Panasonic PLC and PC in C#.NET environment can give full play to the advantages of the .NET framework. It is practical, easy communication, high reliability and can combine with other measurement and calibration procedures effectively and conveniently. Configuration software is expensive and can only communicate with PLC separately, but these shortcomings can be solved in C#.NET environment. A well-designed user interface realized real-time monitoring of PLC parameters and achieved management and control integration. The experiment show that this method of data transfer is accurate and the program’ running is stable.
Design and development of 80 meters laser interferometric measurement standard device
Dongjing Miao, Jianshuang Li, Mingzhao He, et al.
A large-scale laser interferometric measurement standard device was designed and developed to improve the quantity transmission and calibration capabilities for linear measuring tools and large-scale high precision measurement instruments such as laser trackers, laser scanners and electronic total stations, etc. It consisted of an 80 meters granite guiding rail system, a length measuring system composed of three interferometers, a coarse-fine composite motion platform, environmental parameter (air pressure, temperature and humidity) automatic measuring system, and an image aiming system. The uncertainty of the standard device was analyzed, and a comparative experiment was made to determine the calibration capability of the built standard device. Experiment result indicated that the measurement uncertainty of this standard device to calibrate the other interferometers was better than 0.1μm + 1.0 × 10-7 L(k = 2).
Investigation of hidden diffuse surfaces using phase-shifting endoscopic digital speckle pattern interferometry
Yan Gao, Sijin Wu, Lianqing Zhu, et al.
Digital speckle pattern interferometry (DSPI) is an important optical tool which is widely used in many sophisticated applications. However, a traditional DSPI system can only be used to investigate the outer surfaces which can be easily observed. Therefore, an endoscopic DSPI was proposed to detect the internal and hidden surfaces. It has a rigid or flexible endoscopic tube to allow a hidden surface being clearly imaged. A fiber-optics-based setup makes the proposed DSPI system compact and robust. The temporal phase-shifting technique is used to help precise extraction of phase distributions from speckle patterns.
Stitching interferometry for asphero-diffractive surface
Weibo Wang, Mengqian Zhang, Siwen Yan, et al.
This article describes the method of mathematically stitching together a plurality of overlapping individual annular sub-aperture maps to yield the full-aperture map of an asphero-diffractive surface. The unknown step height and relative position of each zone causes some ambiguity when the individual sub-apertures are combined into a full aperture map. The uncertainty is mainly caused by alignment error and noise during the measurements of individual sub-aperture maps and step height. The optimization and merit function works to minimize the discrepancy between multiple data sets by including components related to various alignment errors and noise during the measurements of individual sub-aperture maps and step height. The stitching coefficients which minimize the mean square difference between any overlapping values can be found through iterative constrained optimization. The full aperture wave-front is reconstructed by stitching sub-apertures with the stitching coefficients within meaningful bounds.
3D reconstruction for sinusoidal motion based on different feature detection algorithms
Peng Zhang, Jin Zhang, Huaxia Deng, et al.
The dynamic testing of structures and components is an important area of research. Extensive researches on the methods of using sensors for vibration parameters have been studied for years. With the rapid development of industrial high-speed camera and computer hardware, the method of using stereo vision for dynamic testing has been the focus of the research since the advantages of non-contact, full-field, high resolution and high accuracy. But in the country there is not much research about the dynamic testing based on stereo vision, and yet few people publish articles about the three-dimensional (3D) reconstruction of feature points in the case of dynamic. It is essential to the following analysis whether it can obtain accurate movement of target objects. In this paper, an object with sinusoidal motion is detected by stereo vision and the accuracy with different feature detection algorithms is investigated. Three different marks including dot, square and circle are stuck on the object and the object is doing sinusoidal motion by vibration table. Then use feature detection algorithm speed-up robust feature (SURF) to detect point, detect square corners by Harris and position the center by Hough transform. After obtaining the pixel coordinate values of the feature point, the stereo calibration parameters are used to achieve three-dimensional reconstruction through triangulation principle. The trajectories of the specific direction according to the vibration frequency and the frequency camera acquisition are obtained. At last, the reconstruction accuracy of different feature detection algorithms is compared.
Vibration studies of simply supported beam based on binocular stereo vision
Chaojia Liang, Huaxia Deng, Jin Zhang, et al.
That sensors are used to collect experimental data is still prevalent nowadays. A common way to analyze the mode of vibration of a structure, lots of sensors may required to be installed on the structure in order to ensure completeness of data. However, if these data can be obtained based on machine vision, the effects caused by sensors on the beam would be removed. A new kind of non-contact method will be used to measure the mode of vibration of simply supported beam. In this paper, the basic theory of the simply supported beam and machine vision will be introduced. It is different from traditional way that is based on a large number of sensors to collect experimental data. Two cameras record the vibration process of simply supported beam while the beam is vibrating caused by an exciter. After those images that have recorded the vibration process of simply supported beam are processed, calibration and registration included, those data collected by sensors also are reconstructed by traditional modal test method for comparison. Through comparing the machine vision method and sensor based method, errors caused by the process of reconstruction might be analyzed. The first order modal vibration modes by using two ways and combining with finite element method to produce can also be analyzed what their differences are.
Multifunction surface measurement system based on focusing optical stylus interference and confocal image
Fenfen Lin, Shuling Zhao, Suping Chang, et al.
In this paper a multifunction surface measurement system based on focusing optical stylus interference and confocal image is researched. This system is designed on the structure of optical interference microscopy and could accomplish two measurement functions of optical stylus scanning measurement and confocal image measurement. Optical path difference would vary with the surface and interference fringe from optical interference microscopy is detected by photo sensor, so optical stylus scanning measurement would be accomplished combining with the X-Y two-dimensional stage. While the reference path of the interference microscope is blocked and the confocal images of the measured surface from CCD is analyzed, confocal imaging measurement would be carried out by the nanometer scanning displacement stage. According to the performance analysis, optical stylus scanning measurement has the measurement range of 50μm and the vertical scanning resolution of 0.005μm, while confocal imaging measurement has the measurement rage of 2mm and the vertical scanning resolution of 1.5μm.
Anti-jamming capability of pseudorandom noise code ranging systems under narrowband interference
In the presence of narrowband interference (NBI), the ranging receivers should not only remain steady but also satisfy the requirement of ranging precision. By taking into account both the system stability and the precision requirement, this paper defined the anti-jamming margin of a ranging system (RS-AJM) to provide a comprehensive evaluation of anti-jamming capability. A margin reference factor was introduced to describe the relationship between the two requirements, which was used to divide the margin calculation into three cases. When the system is in the high stability region, the system stability is more important than the ranging precision. When the system is in the high precision region, the anti-jamming margin mainly depends on the precision requirement. When the system is in the middle region, the two requirements determine the anti-jamming capability together. The middle region can be further divided into another two zones according to the center frequency of NBI. The margin reference factor and the performance scenario division present a clear and comprehensive description of the anti-jamming capability, which is also verified using numerical results.
The propagation of manufacture uncertainty to dynamic measurement
Jun Wang, Huaxia Deng, Jin Zhang, et al.
Uncertainty is the degree of suspicious for correctness or accuracy of measurement results. Parts of the manufacturing error directly affect the structural dynamic characteristics. The propagation of uncertainty in the static measurement from characteristics to the measurement results has been investigated for decades. However, the propagation of manufacture uncertainty to the results of dynamic measurement has been rarely investigated, which is an important issue for the design and tests of structures and equipment. In this paper, the propagation of manufacturing uncertainty to the dynamic measurement is investigated on the basis of modal analysis method. The manufacturing uncertainty here is represented by the tolerance of form and position, which is the difference between actual shape or position and the digital 3D model of geometry shape and position. Tolerance of form and position is an< important indicator to evaluate object geometry size and the relative position in the mechanical design. The uncertainty of the tolerance of form and position is assumed to satisfy Gaussian distribution. The relationship between modal parameters and tolerance is predicted by analyzing transition rules of modal parameters. A series of beams with tolerance of form and position analyzed experiment to verify transitive relation between varied modal parameters in modal analysis and tolerance. The investigation found that the distribution of the uncertainty of the parameters of dynamic measurement, such as the natural frequencies and modal shapes, are not inherently satisfied with Gaussian distribution, although the uncertainty of characteristics are Gaussian distributed, which confirms the difference of uncertainty propagation in the static measurement and dynamic measurement.
Theoretical analysis of harmonic suppression in multi-step error separation technique
Wei Gu, Jiubin Tan, Jingzhi Huang
Multi-step error separation technique is one of the most widely used roundness separation technique. It can improve the precision of the roundness measuring instrument. By analyzing the model of multi-step, we can find that it has harmonic suppression and cannot be completely separate the roundness error of the tested parts from the rotation error of the spindle. When we use the M-steps, the km times harmonic in tested parts is lost and is mixed 1:1 with the rotation error of the spindle. In this paper, theoretical provement and simulation analysis of harmonic suppression of multi-step error separation technique are carried out: 1) using a group circular standards to separate the same spindle; and 2) using different steps to separate the same spindle.
Influence of diffraction effect on measurements of absolute gravity
By raising measurement accuracy of absolute gravimeter, we need to find out the influence factor and conduct evaluation. After the 8th international key comparison of absolute gravimeter in 2009(ICAG-2009), people emphasize putting forward some correction key point, one of them is the diffraction correction. Due to divergence of laser beam, wave front is arc-shaped, laser beam of interferometer cannot go all the way with falling body’s drop direction. Because of this reason, the measurement result is less than original value. This is called diffraction effect. Here, this correction is called “Diffraction Correction”. For our absolute gravimeter NIM-3A, we research this effect and bring forward evaluation method and correction value. In this paper, we will conduct research and calculate. Consequently, we could receive the correction value of acceleration of gravity.
Analysis of pneumatic hammer in rectangular aerostatic thrust bearing with groove
The pneumatic hammer in rectangular aerostatic thrust bearings with groove is analyzed using perturbation theory. Routh stability criterion was used to evaluate the critical condition of pneumatic hammer in rectangular aerostatic thrust bearings with groove, and the influence of supply pressure, throttle area, groove area, and thickness of film on aerostatic thrust bearings. It was found through analysis that the change rate of stiffness and the volume ratio of aerostatic bearing could be used to analyze the pneumatic hammer in rectangular aerostatic thrust bearings with groove. At a certain film thickness, the stability of aerostatic bearings could be improved by reducing supply pressure, increasing throttle area and decreasing groove area to facilitate the design of a general aerostatic thrust bearing.
Implementation of primary low-g shock standard for laser interferometry
Qiao Sun, Jian-lin Wang, Hong-bo Hu
This paper presents the novel implementation of a primary standard for low-g shock acceleration calibration based on rigid body collision using laser interferometry at National Institute of Metrology (NIM), China. The combination of an electromagnetic exciter and a pneumatic exciter as mechanical power supply of the shock excitation system are built up to achieve a wider acceleration range. Three types of material for shock pulse generators between airborne anvil and hammer are investigated and compared in the aspects of pulse shapes and acceleration levels. A heterodyne He-Ne laser interferometer is employed for precise measurement of shock acceleration with less electronic and mechanical influences from both the standard device itself and its surroundings. For signal acquisition and processing, virtual instrument technology is used to build up data acquisition PXI hardware from National Instrument and calibration software developed by LabVIEW. Some calibration results of a standard accelerometer measuring chain are shown accompany with the uncertainty evaluation budget. The expanded calibration uncertainty of shock sensitivity of the accelerometer measuring chain is 0.8%, k=2, with the peak range of half-sine squared acceleration shape from 20m/s2 to 10000 m/s2 and pulse duration from 0.5 ms to 10 ms. This primary shock standard can meet the traceability requirements of shock acceleration from various applications of industries from automobile to civil engineering and is used for piloting ongoing international shock comparison APMP.AUV.V-P1.
Improvement of spatial resolution in confocal microscope with shifted-focus phase filter
Xiangdong Huang, Xiaoyan Xiang, Chongyang Wang
A spatial super-resolution method is proposed based on the multiplicative character of confocal microscope’s amplitude point-spread functions. The axial resolution can be greatly improved by introducing a shifted-focus phase filters in illumination part of a confocal microscope. However, this improvement is accompanied by a decrease of transversal resolution. Thus, a super-Gaussian phase filter is optimized to control the focal shift and transversal intensity distribution in a confocal microscope. Numerical simulation results indicate that the proposed method is useful to obtain a significant improvement in the optical sectioning capacity.
Elimination of Abbe error method of large-scale laser comparator
Jianshuang Li, Manshan Zhang, Mingzhao He, et al.
Abbe error is the inherent systematic error in all large-scale laser comparators because the standard laser axis is not in line with measured optical axis. Any angular error of the moving platform will result in the offset from the measured optical axis to the standard laser axis. This paper describes to an algorithm which could be used to calculate the displacement of an equivalent standard laser interferometer and to eliminate an Abbe error. The algorithm could also be used to reduce the Abbe error of a large-scale laser comparator. Experimental results indicated that the uncertainty of displacement measurement due to Abbe error could be effectively reduced when the position error of the measured optical axis was taken into account.
Multimode vibration damping as a result of piezoelectric energy harvesting
Hui Shen, Fengsheng Zhang, Jinhao Qiu, et al.
Energy harvesting systems are interesting for use in remote power supplies. Many such systems utilize the motion or deformation associated with vibration, converting the mechanical energy to electrical energy, and supplying power to other electronic devices. In terms of energy harvesting from mechanical vibrations, piezoelectric conversion has received much attention as it can directly convert applied strain energy into useable electric energy and easily be integrated into a microsystem. The removal of mechanical energy from a vibrating structure necessarily leads to a damping effect. This paper addresses the damping associated with a piezoelectric energy harvesting system which is called the adaptive synchronized switching harvesting (ASSH) technique. Furthermore, a self-powered circuit which implements the technique (ASSH) is proposed, which validates that the new technique can be truly self-powered. Experimental results show that the vibration amplitudes of the first two modes are reduced by about 9.27 dB and 0.96 dB in the case of the exciting signal of same amplitude ratio (3:3), respectively. Compared with other self-powered vibration damping technique, this technique not only shows its robustness, but also harvests the energy and supply power to other electronic circuits.
Study on formation and transformation of the optical nonlinearity harmonics in the heterodyne laser interferometer
Haijin Fu, Jiubin Tan, Zhigang Fan
The accuracy of the heterodyne laser interferometer is strongly restricted by the optical nonlinearity harmonics. In order to mathematically reveal the formation and transformation mechanism of optical nonlinearity harmonics, the behavior of the nonlinearity harmonics is investigated with an optical nonlinearity expression based on the optical mixing parameters in the measurement signal. It is found that the formation and transformation of the first-order and second-order nonlinearity harmonics are closely related to the orthogonality of the optical mixing parameters. When the optical mixing parameters satisfy the orthogonal relation, the optical nonlinearity is purely the second-order harmonic whose peak-to-peak value is at least one order smaller than that of the first-order harmonic in the same optical mixing degree, indicating that a larger optical mixing level does not necessarily lead to a considerable optical nonlinearity error, which provides the theoretical guidance for building a heterodyne laser measurement system with low optical nonlinearity.
Equivalent common path method in large-scale laser comparator
Mingzhao He, Jianshuang Li, Dongjing Miao
Large-scale laser comparator is main standard device that providing accurate, reliable and traceable measurements for high precision large-scale line and 3D measurement instruments. It mainly composed of guide rail, motion control system, environmental parameters monitoring system and displacement measurement system. In the laser comparator, the main error sources are temperature distribution, straightness of guide rail and pitch and yaw of measuring carriage. To minimize the measurement uncertainty, an equivalent common optical path scheme is proposed and implemented. Three laser interferometers are adjusted to parallel with the guide rail. The displacement in an arbitrary virtual optical path is calculated using three displacements without the knowledge of carriage orientations at start and end positions. The orientation of air floating carriage is calculated with displacements of three optical path and position of three retroreflectors which are precisely measured by Laser Tracker. A 4th laser interferometer is used in the virtual optical path as reference to verify this compensation method. This paper analyzes the effect of rail straightness on the displacement measurement. The proposed method, through experimental verification, can improve the measurement uncertainty of large-scale laser comparator.
Beam shaping with vortex beam generated by liquid crystal spatial light modulator
An optical vortex is a beam of light with phase varying in a corkscrew-like manner along its direction of propagation and so has a helical wavefront. When such a vectorial vortex beam and the Gaussian beam with orthogonal polarization are focused by low NA lens, the Gaussian component causes a focal intensity distribution with a solid center and the vortex component causes a donut distribution with hollow dark center. The shape of the focus can be continuously varied by continuously adjusting the relative weight of the two components. Flat top focusing can be obtained under appropriate conditions. It is demonstrated through experiments with a liquid crystal spatial light modulator in such a beam, that flattop focus can be obtained by vectorial vortex beams with topological charge of +1 to achieve beam shaping vortex.
Refractive index of air for interferometric length measurements
The refractive index of air can be directly measured by a refractometer or can be calculated by using updated Edlén's formulas by measuring the parameters of the surrounding air or by using the modified two-colour method. In this paper an overview on the three methods is given by taking into account for their features, uncertainties and application fields.
Effects of dynamic characters of the macro-micro fast coupling system in long stroke system
Jianwei Wu, Yong Yuan, Jiwen Cui
Macro-micro fast coupling system of dual-stage is used for the detachment and coupling of the macro-motion system and the wafer-stage. When the macro-motion system couples with the wafer-stage, the wafer-stage is driven by macro-motor to achieve long stroke motion. In this paper, the bottom air bearings of wafer stage are analyzed when the driving force of macro motor shifts the center of mass of wafer stage in Z direction. The X, Y, Z stiffness of the coupling system are obtained by using ANSYS.
Analyzing time walk error of leading trailing edge CFD of timing discrimination for Gaussian and Rayleigh distribution waveform
In this study we analyze one of a CFD for timing discrimination. Walk error, drift and precision are the three performance parameters of timing discrimination. The walk error is the most important error type generally. Firstly, we divided the waveform into two types. One is the Gaussian waveform distribution which has three parameters: amplitude, mean, and the pulse width; and the other is Rayleigh waveform distribution which has two parameters: mean and pulse. We analyzed different situations with their changing parameter, and the drift value of time can be obtained for each parameter changing.
Adjusting and positioning method with high displacement resolution for large-load worktable based on the invariable restoring force
With the fast development of the advanced equipment manufacturing toward precision and ultra-precision trend, especially with the continuously improving of the aviation engine’s performance, the problem of high displacement resolution for the large-load two-dimension adjusting and positioning worktable used for the aeroengine assembling become evident. A method was proposed which is based on the invariable restoring force, and the adjusting and positioning physical model was established. The experiment results indicate that under the occasion of a load with 508 kilogram, the worktable has got a displacement resolution of 0.3μm after using the improved method compared to 1.4μm of the traditional method. The improved method could meet the requirements of aviation engine assembling worktable.
Research on measurement of lateral dimension based on digital micromirror device
Qing Yu, Chang-cai Cui, Wei Fan, et al.
For better machining and electrical characteristic, the complex surfaces topography of some delicate machining tools and electronic components should be acquired precisely, including shape and size of microstructure on surface of engineering material or precision component from microscopic view, and relationship between microstructures from macroscopic viewpoint, such as spaces, distribution and so on. This so called multiscale measurement has been greatly focusing by experts and scholars from home and abroad. People researched this novel measurement in several ways: (1) putting different sensors together, which had different resolution and measuring range; (2) applying software technology, include wavelet theory, fractal theory and image mosaicing technology, to solve this multi-scale measurement problem. However, it’s difficult to cooperate with many different sensors in multi-sensors measurement technology, and mathematical modeling is very complicated in software technology. This paper used Digital Micromirror Device (DMD) as a multiscale measuring tool, and a method of measurement on lateral dimension has been proposed. As an excellent optical modulation device, DMD could modulate incident light to line structure light. Owing to controlling flexibility of DMD, the parameters of the line structure light, include line width, light intensity and scanning frequency, could be modulated by programming. This project has solved the problem of measurement error due to the angle between line structure light and field of view of specimen, and the results of experiment proved that, this method by DMD acquired lateral dimension data conveniently.
Development and validation of a lateral MREs isolator
Zhi-Wei Xing, Miao Yu, Jie Fu, et al.
A novel lateral vibration isolator utilizing magnetorheological elastomers (MREs) with the field-dependent damping and stiffness was proposed in order to improve the adaptive performance. First, soft silicone rubber MREs with a highly adjustable shear storage modulus was fabricated. Then, the lateral MREs isolator was developed with a unique laminated structure of MRE layers and steel plates, which enables to withstand large vertical loads and adapts to the situation of large lateral displacement. Also, the electromagnetic analysis and design employed electromagnetic finite element method (FEM) to optimize magnetic circuit inside the proposed device. To evaluate the effectiveness of the lateral MREs isolator, a series of experimental tests were carried out under various applied magnetic fields. Experimental results show that the proposed MREs isolator can triumphantly change the lateral stiffness and equivalent damping up to 140% and 125%, respectively. This work demonstrates the performance of the designed lateral MREs isolator and its capacity in vibration mitigation for the complex situation.
Effect of reflector angle on the performance of an fiber bundle distance sensor with single mode illumination
Yong Jiang, Quanyang Wang, Zhi Zhong
In order to study the effect of reflector angle on the performance of two fiber distance sensor with single mode illumination, a theoretical model approximating the illumination light exiting the single mode fiber as having a Gaussian intensity profile is established to describe the intensity modulation performance by taking the reflector angle into consideration, and measurements were made to verify the validity of the theoretical model. Numerical simulation results indicate that although the effect of reflector angle α on the sensitivity becomes weaker when α is positive, the blind region, linear range, peak position and sensitivity decreases as the reflector angle becomes more and more positive. The study would help the design and application of fiber distance sensor with single mode illumination.
High-speed measurement of nozzle swing angle of rocket engine based on monocular vision
Yufu Qu, Haijuan Yang
A nozzle angle measurement system based on monocular vision is proposed to achieve high-speed and non-contact angle measurement of rocket engine nozzle. The measurement system consists of two illumination sources, a lens, a target board with spots, a high-speed camera, an image acquisition card and a PC. A target board with spots was fixed on the end of rocket engine nozzle. The image of the target board moved along with the rocket engine nozzle swing was captured by a high-speed camera and transferred to the PC by an image acquisition card. Then a data processing algorithm was utilized to acquire the swing angle of the engine nozzle. Experiment shows that the accuracy of swing angle measurement was 0.2° and the measurement frequency was up to 500Hz.
Multi-functional hinge equipped with a magneto-rheological rotary damper for solar array deployment system
Mingfu Wen, Miao Yu, Jie Fu, et al.
This article describes the design and simulation of a novel multi-functional hinge equipped with a rotary magnetorheological damper for solar array deployment system, which is comprised of a hinge, an angular sensor, a positioning and locking mechanism and a rotary damper. In order to achieve the compact design in structure, some components were reused in different function modules. It’s the first to use magnet-rheological fluid (MRF) to dissipate the energy in solar array deployment system. The main advantage in using MR rotary damper instead of a viscous fluid rotary damper is that the damping force of MR damper can be adjusted according to the external magnetic field environment excited. A mechanic model was built and the structure design was focused on the MR rotary damper, a damping force model of this damper is deduced based on hydromechanics with Bingham plastic constitutive model. A simulation of deployment motion was taken to validate the motion sequence of various components during the unfolding and locking process. It can be obtained that a constant damping coefficient can hardly balance the different performance of solar deployment system, then a simulation of the proposed deployment system equipped with rotary MR damper was carried out. According to the simulation, it can be obtained that the terminal velocity decreased by 75.81% and the deployment time decreased by 72.37% compared with a given constant damping coefficients. Therefore, the proposed new type of rotary damper can reach a compromise with different performance utilizing an on-off control strategy.
A method of gear defect intelligent detection based on transmission noise
Hong-fang Chen, Yun Zhao, Jia-chun Lin, et al.
A new approach was proposed by combing Ensemble Empirical Mode Decomposition (EEMD) algorithm and Back Propagation (BP) neural network for detection of gear through transmission noise analysis. Then feature values of the feature signals are calculated. The feature values which have a great difference for different defect types are chosen to build an eigenvector. BP neural network is used to train and learn on the eigenvector for recognition of gear defects intelligently. In this study, a comparative experiment has been performed among normal gears, cracked gears and eccentric gears with fifteen sets of different gears. Experimental results indicate that the proposed method can detect gear defect features carried by the transmission noise effectively.
Working-point control technique for the homodyne interferometry in hydrophone calibration
Ping Yang, Guangzhen Xing
The stabilization of a homodyne type Michelson interferometer for calibrating the high frequency hydrophone is presented in this article. For the detection of the ultrasonic field, a 5 um thickness pellicle was inserted in water moving in sympathy with the ultrasonic wave. To ensure high signal to noise ratio at high frequencies, a 5 MHz focusing transducer was driven by high voltage and harmonics of the shocked ultrasonic field could be activated. Nevertheless, the homodyne interferometer suffered from the drawback of signal fading caused by the low frequency noise in environment, including acoustic noise and water surface agitation. Direct Current Phase Tracking was utilized to maintain the quadrature working point for the interferometer. Most of environmental noises could be effectively compensated while stabilization was maintained. A piezoelectric actuator supporting the reference mirror was utilized as the stabilizing element whose output was frequency independent over the low frequency disturbances, usually below 200 Hz. The ultrasonic signal fading caused by environmental disturbances could be solved while the negative electric feedback loop was operating. The displacement and voltage output of the hydrophone under test were then processed by DFT to derive the fundamental and harmonic components. Under plane wave conditions, the ultrasonic pressure could be derived by the detected displacement with a stabilized homodyne interferometer, and the hydrophone could then be calibrated. Measurement results indicated that the hydrophone calibration system based on the active stabilization of homodyne interferometry was sound in theory and feasible in practice.
Design and implementation of an illumination device for optical inspection of defects in glass substrates
Ming-Fu Chen, Bo-Cheng Chen, Chih-Wen Chen, et al.
A compact and cost-effective illumination platform was developed for a versatile optical inspection system to improve the detection accuracy of defects in glass substrates. The illumination device was developed in two phases, initially to demonstrate its feasibility for surface defect inspection in glass based on dark field images, and subsequently to optimize the design so it can provide multi-directional lighting and increase light scattering from defects on the substrate. Three LED arrays were installed above the substrate carrier and projected at an angle onto the glass substrate for the phase-I illumination device. Surface defects on the glass substrate were successfully reconstructed from images acquired by a line scanned CCD camera, but non-uniformity of defects intensity distribution on images was revealed. To optimize the illumination, two sets of tightly arrayed 3-watt LEDs were symmetrically installed at the entrance slit of the lens-camera module for phase-II illumination device. The inspection data were able to show clearer images of surface defects. The design issues such as poor contrast and sharpness of acquired images due to low scattering efficiency and non-uniform illumination were addressed as well. PCBs for the installation of the LED arrays and their power supply were also optimized. These were manufactured on aluminum substrate to help regulate heating of the inspection platform. This feature makes the system more compact, operable at low power, and easy for modification.
Discuss on traceability method of light-scattering airborne particle counter’s counting performance
Qizheng Ji, Zhiliang Gao, Xunbiao Zhang, et al.
The traceability of light-scattering airborne particle counter’s counting performance has received more attention, but has failed to settle internationally. This paper puts forward a traceability method of light-scattering airborne particle counter’s counting performance on single particle size, based on Anodic Aluminum Oxide (AAO) template andScanning Electron Microscope (SEM), by reforming the traditional standard airborne particle counter, building a measurement system including AAO and SEM, and utilizing the method of statistical physics in data processing to obtain more accurate measurement results. According to the actual test results and its uncertainty analysis, the traceability method of light-scattering airborne particle counter’s counting performance based on AAO and SEM makes sense in theory, and has certain research value on a solution to the traceability problem of light-scattering airborne particle counter internationally.
Analysis of the effect anisotropic retards collimation turns on polarization and energy radiation parameters
The research of changes of the parameters for the polarized radiation output anisotropic linear phase-shifting elements, with their minor collimation turns about the source of spatial orientation in the optical scheme of measuring polarization device, is performed. Comparative analysis of the polarization and energy parameters of the radiation output retards of crystalline silica, magnesium fluoride, and polyvinyl alcohol are accomplished. The dependencies of changes of the ellipticity and azimuth of the output radiation, as well as the transmission coefficient of the phase plate with the changing spatial orientation from the hade on refracting side and azimuth of linearly polarized radiation at its input are considered.
Calibration of rotary table by whole combination measuring method
Hua Ai, Yanbo Cao
Whole combination measuring method was used to calibrate a rotary table with a system error of 1", together with polygon; the inherent deviation of an angle in the polygon was then extracted from the results. The final PV value of angular measurement precision was ±0.5", which could be extended to the high-precision angular measurement.
Investigating of precision measurement on ultrasonic flow
Fangliang Jiang, Qizheng Ji, Dongwei Zhai, et al.
The flow rate is calculated via ultrasonic flow meter (UFM), which is through measuring the difference of time transmitting flow between flow direction and reverse direction. This paper describes the uncertainty analysis for the method of time difference which is commonly used in ultrasonic flow measurement, and the analysis of error source of uncertainty components as well as the general method of elimination. Based on the technique of pseudo random sequence, this paper presents a precise time difference method based on digital correlation technology, and its principle, realization way and uncertainty evaluation are introduced. On the DSP and FPGA system platform, an ultrasonic flow meter scheme based on the digital correlation technology is suggested.
Generation of stainless steel superhydrophobic surfaces using WEDM technique
This paper presents a novel fabrication methodology for generating superhydrophobic surfaces on stainless steel. The Wire Electric Discharge Machining (WEDM) technique was utilized to change the wettability of stainless steel which is generally hydrophilic. Superhydrophobic surfaces were obtained on the stainless steel by strictly control the machining progress. The mechanism of wettability modulation was explored using the well-established surface metrology and characterisation instruments. It was noted that WEDM can be used to generate a recast layer on stainless steel surface. There was a number of hierarchic micro-structures in the irregular recast layer and the number of micro-holes increases the contact area between the water drop and the top surface of stainless steel. Thus, the contact angle was significantly increased and the wettability of stainless steel changed from hydrophilic into hydrophobic. Compared with other established fabrication approaches, the stainless steel based hydrophobic surface can provide long durability, high efficiency and low cost metallic surfaces, which paves the way for the practical applications of stainless steel hydrophobic surfaces in the academic and engineering fields.
Portable and modularized fluorometer based on optical fiber
WeiWei Yue, Lei Zhang, ZhenYa Guo, et al.
A portable and modularized fluorometer based on optical fiber was proposed in this work. The fluorometer included a light emitter diode (LED) light source module (LSM), a sample cell module (SCM), an optical-electrical converter module (OCM) and a signal process module (SAM). The LEDs in LSM were driven by a constant current source to provide stable exciting light with different wavelength. The OCM included a modularized optical filter and used a photomultiplier tube (PMT) to detect fluorescence signal. The SCM was used to locate sample cuvette and could be connected by optical fibers with the LSM and OCM. Via modularized design, the LSM and OCM could both selected and replaced based on different fluorescence dyes. In order to improve the detecting dynamic range of the fluorometer, the SAM could control the light intensity of LED source in LSM, to control the gain of PMT in OCM, and particularly, four channel signal acquisition circuits with different gain were constructed to collect fluorescence signal simultaneously. Fluorescein isothiocyanate (FITC) was selected as sample to test the fluorometer. The fluorometer has shown a high sensitivity with FITC concentration of 10ng/mL and presented a good linearity from 10 ng/mL to 10 μg/mL.
A displacement measuring system based on grating double diffraction
Bo Zhao, Lei Wang, Min-er Xu, et al.
A displacement measuring system based on grating double diffraction is proposed in this paper to eliminate the impact of multiple reflections of the zero-order diffraction beam and to reduce the stray light coming from the interference field. The principle of the proposed system is that with the proper interference of the first order beam of second diffraction, a displacement transducer can be obtained via the Doppler frequency shift and phase decoding. Simulation tests are conducted using LightTools model to prove the effectiveness of the proposed system. And experiment results shows that a resolution of 20 nm can be achieved over a range of 25 mm. It is therefore concluded that the proposed system can be used to improve the measurement resolution and accuracy.
Simulation research on ATP system of airborne laser communication
Zhongyi Zhao, Hailong Huang
The compound axis tracking control circuits model of the ATP system was established and simulation was run on the tracking control performance of the ATP system. It was found through simulation that with the fixed coarse tracking error, the dynamic lag error in the coarse tracking servo system could be suppressed to 120μrad; and with the fixed fine tracking error, the dynamic lag error in the fine tracking servo system could be restrained to 2.73μrad, and the vibration residual could be controlled within 1.5μrad.
Modeling and simulation of continuous wave velocity radar based on third-order DPLL
Yan Di, Chen Zhu, Ma Hong
Second-order digital phase-locked-loop (DPLL) is widely used in traditional Continuous wave (CW) velocity radar with poor performance in high dynamic conditions. Using the third-order DPLL can improve the performance. Firstly, the echo signal model of CW radar is given. Secondly, theoretical derivations of the tracking performance in different velocity conditions are given. Finally, simulation model of CW radar is established based on Simulink tool. Tracking performance of the two kinds of DPLL in different acceleration and jerk conditions is studied by this model. The results show that third-order PLL has better performance in high dynamic conditions. This model provides a platform for further research of CW radar.
Recent advances in absolute distance measurements using femtosecond light pulses
Seung-Woo Kim, Young-Jin Kim, Sangwon Hyun, et al.
Absolute distance measurement (ADM) with high precision is required for various fields of precision engineering, which has long been implemented by means of time-of-flight measurement of a pulsed laser, intensity or frequency modulation of a continuous-wave laser, and cross-correlation of pseudo-random micro-wave signals. Recently, in response to increasing demands on the measurement precision and range beyond conventional limits, femtosecond pulse lasers began to draw attention as a new light source that permits realizing various advanced ADM principles such as synthetic radiofrequency wavelength generation, Fourier-transform-based dispersive analysis and multi-wavelength interferometry. In this talk, we present the state-of-the-art measurement principles and performance demonstrated by exploiting the unique temporal and spectral characteristics of femtosecond laser pulses for high-precision ADM applications.
Absolute distance measurement using frequency-comb-referenced four-wavelength interferometry
Guochao Wang, Yoon-Soo Jang, Hyunjay Kang, et al.
We measure absolute distances by performing multi-wavelength interferometry (MWI) using four different wavelengths generated simultaneously from the frequency comb of a femtosecond laser. The measurement precision is estimated to be less than 63 nm in peak-to-valley over a distance of 1 m as compared to an incremental HeNe laser interferometer. We also evaluate the operational stability and robustness of the interferometer hardware system over a time period of 12 hours. Finally, it is concluded that the proposed frequency-comb-referenced multi-wavelength interferometry is capable of providing fast, precise and high stable absolute distance measurements, being well suited for industrial precisionengineering applications and near-future space missions.
Communication design for multi-boards based on VME bus
Yang Liu, Fazhi Song, Kai Wei, et al.
As a widely used open-architecture computer bus ,VME bus is increasingly applied in military, aerospace, transportation and other large-scale control systems. Lithography, a very delicate and complicated integrated circuit manufacturing equipment, uses many circuit boards with VME interface in its control system, including one single-board computer, many movement control boards and one data acquisition board. This paper designs communication modules which include VME bus module and VME user-defined bus module for multi-boards in Lithography control system. VME bus module is designed for the communication between the single-board computer and movement control boards and VME user-defined bus is designed for the communication between movement control boards and data acquisition board. The experimental results demonstrate its effectiveness.
Parameter estimation of an air-bearing suspended test table
Zhenxian Fu, Yurong Lin, Yang Liu, et al.
A parameter estimation approach is proposed for parameter determination of a 3-axis air-bearing suspended test table. The table is to provide a balanced and frictionless environment for spacecraft ground test. To balance the suspension, the mechanical parameters of the table, including its angular inertias and centroid deviation from its rotating center, have to be determined first. Then sliding masses on the table can be adjusted by stepper motors to relocate the centroid of the table to its rotating center. Using the angular momentum theorem and the coriolis theorem, dynamic equations are derived describing the rotation of the table under the influence of gravity imbalance torque and activating torques. To generate the actuating torques, use of momentum wheels is proposed, whose virtue is that no active control is required to the momentum wheels, which merely have to spin at constant rates, thus avoiding the singularity problem and the difficulty of precisely adjusting the output torques, issues associated with control moment gyros. The gyroscopic torques generated by the momentum wheels, as they are forced by the table to precess, are sufficient to activate the table for parameter estimation. Then least-square estimation is be employed to calculate the desired parameters. The effectiveness of the method is validated by simulation.
Four-wheel alignment based on computer vision
Dongzhao Huang, Qiancheng Zhao, Tianlong Yang
A model was built for four-wheel alignment on a vehicle based on computer vision. Such parameters as toe-in angle, camber angle, kingpin inclination and kingpin caster were accurately defined and calculation formulas were formulated for the parameters, especially the calculation methods for vector N and vector E. A kind of new 3D four-wheel aligner vas developed. Simulation results and actual measurements indicated that the model and solution method were feasible and effective.
Measurement of duration of AC transient signal waveform using Hilbert transform and least square method
Puzhong Ouyang, Zhonghua Zhang
The time coordinates of interaction points could be established by extracting the envelop of a transient signal waveform through Hilbert transform and formulating the line equations for the increasing and decreasing segments of an envelope using least square method. The difference of time coordinates lies in the duration time. The duration of increasing and decreasing segments and the whole duration of AC transient signal waveform could be accurately evaluated using waveform measurement and least square method. It was found through analyses and experiments that an uncertainty of less than 0.5ms could be achieved for a SNR of more than 40 dB. It was therefore concluded that the proposed method could be used to measure under-voltage waveform and further extended to do power characteristics testing including compliance test of automotive electronic devices.
Detection of sub-pixel chessboard corners based on gray symmetry factor
Qiancheng Zhao, Zhongzhu Chen, Tianlong Yang, et al.
In order to solve the robustness and efficiency problems of chessboard corner detection under on-site condition, a method based on the square-closed loop template and local gray symmetry factor is proposed for detecting sub-pixel chessboard corners with high precision and efficiency. Interest points on edges of original image is detected by square-closed loop template according to the transition times on the template, on this basis, corners are roughly detected by averaging the adjacent coordinates of interest points; gray symmetry factors, calculated in the local neighborhood of roughly detected corners, are used as the weighting factors to precisely detect corners on sub-pixel level. Experimental results indicate that computing speed and positioning accuracy of this method was obviously increased. The corner detection performance could be significantly improved using the proposed method.
Research on dual-wavelength photometric method for micro liquid volume measurement
Jintao Wang, Ziyong Liu, Lin Tong
In order to overcome the shortcoming of significant influence of evaporation capacity on gravimetric method and meet the requirement of online measurement, dual-wavelength photometric method is introduced for measuring microliquid volume. Based on Lambert-Beer law, this paper introduces the dual-wavelength photometric method (DWP method) at 520 nm and 730 nm, which can measure the microliquid volume through the linear relation between the concentration of dilute solution and the absorbance. Comparing to gravimetric method, an experimental system for dual-wavelength photometric method was designed. Experimental results indicate that the test result obtained by using DWP method was better than obtained by using gravimetric method, and met the technical requirement of ISO 8655. Compared with the gravimetric method, the non-gravimetric methods can provide a better solution for microliquid volume measurement, which was less stringent for measurement environment, easy to realize the online calibration and capable of reducing the influence of liquid evaporation.
An improved PSO algorithm and its application on model identification of coarse-stage in lithography machine
Yang Liu, Fazhi Liu, Kai Wei, et al.
Lithography machine is a high-precision manufacturing equipment of electromechanical integration, involving precision machinery, precision control and measure, precision measurement and other subjects. PSO algorithm is easy to fall into local optimum, which has simple concepts and fast convergence. This paper proposes an improved PSO algorithm with adaptive parameters and boundary constraint, in ensuring accuracy of the algorithm optimization and fast convergence. Simulation results show that the methods have good applicability and stability for coarse-stage in lithpgraphy machine.
A novel method for measuring transit tilt error in laser trackers
Zili Zhang, Weihu Zhou, Han Zhu, et al.
A novel method was proposed to measure the tilt error between the transit axis and standing axis of the laser tracker. A gradienter was first used to make the standing axis of the laser tracker perpendicular to the horizontal plane. The laser beam of the tracker was then projected onto a vertical plane set at a certain distance from the tracker with equal horizontal angles and diverse vertical angles in two-face mode. The contrail of the laser beam was recorded while the simulation was manipulated to estimate the beam trail under the same circumstance. The tilt error was thus obtained according to the comparison of the actual result against the simulated one. Experimental results showed that the accuracy of the tilt measuring method could meet the user’s demand.
Research on PID controller with input shaping algorithm for linear motor
Yang Liu, Yue Dong, Wenchao Fan, et al.
The reticle stage of lithography is a high precision servo motion platform, which requires using macro movement of linear motor and micro movement of voice coil motor to realize an nm-level positioning precision and tracking. In order to increase the control effect and response speed of macro movement linear motor of reticle stage of lithography, the paper presents an efficient control for linear motor. The method use input shaping technique with Proportional Integral Derivative (PID) controller to realize the high position precision in small stetting time. In the paper we firstly build the linear motor mathematical modeling which is end to velocity loop or position loop. so that we mainly focus on the tracking of speed signal. Then a PID controller is introduced in the system, which is high frequency used in industrial control. Finally, as the need of high positioning precision and small stetting time, we apply input shaping algorithm to solve the problem. The simulation of the system is performed by using MATLAB/Simulation. The evaluation of the method is the performance of input tracking capability.
Passive protective strategy for ultra-precision dual-stage
Yang Liu, Zhenyu Chen, Zhenxian Fu
In order to improve the throughput of lithography machine, a new type of lithography machine began to adopt double wafer stages which make the exposure and measurement work simultaneously. But at the same time, this structure also increases the risk greatly, the wafer stage collision for instance. Therefore, a corresponding safety protection system is necessary to protect the whole double wafer stages system and to improve the throughput on the premise of safety. In this paper, a passive safety protection strategy for double-stages lithography machine is proposed based on analysis of its working conditions. The design principle of safety needle is elaborated, and then needle distribution is determined correspondingly. The simulation results show that, the proposed passive protection method carried out by safety needles could avoid damages of sensitive apparatus.
Cogging force rejection method of linear motor based on internal model principle
Yang Liu, Zhenyu Chen, Tianbo Yang
The cogging force disturbance of linear motor is one of the main factors affecting the positioning accuracy of ultraprecision moving platform. And this drawback could not be completely overcome by improving the design of motor body, such as location modification of permanent magnet array, or optimization design of the shape of teeth-slot. So the active compensation algorithms become prevalent in cogging force rejection area. This paper proposed a control structure based on internal mode principle to attenuate the cogging force of linear motor which deteriorated the accuracy of position, and this structure could make tracking and anti-disturbing performance of close-loop designed respectively. In the first place, the cogging force was seen as the intrinsic property of linear motor and its model constituting controlled object with motor ontology model was obtained by data driven recursive identification method. Then, a control structure was designed to accommodate tracking and anti-interference ability separately by using internal model principle. Finally, the proposed method was verified in a long stroke moving platform driven by linear motor. The experiment results show that, by employing this control strategy, the positioning error caused by cogging force was decreased by 70%.
Multi-view 3D measurement data registration based on encoding point spatial location and match
Haihua Cui, Zhimin Zhao, Minghui Tang, et al.
This paper presents a novel registration method by encoding feature point identification and spatial location to make the registration of 3D measurement easy. A new proposed decoding algorithm based on polar coordinate segmentation is first used for identification feature point, the feature points are then measured and constructed. The overlapped 3D measurement feature points within two views are used to unify coordinate system, so the feature points of each view are achieved for global spatial location. The object is finally measured with any view which only contains at least three feature points. The unconstrained 3D registration is acquired with the feature points matching between single measurement view and global spatial points. Our experiments show that the proposed method is convenient and effective, and greatly enhances the flexibility of 3D measurement applications.
Real time measurement for deformation of large expansion frame based on retro-reflective technique and vision method
Wei Tao, Kai Jiang, Hui Zhao
Large frames made of compound material are widely used in many areas such as industry and aerospace. To ensure the frames working properly, monitor of its deformation after expansion is of great importance. A real time measurement system based on retro-reflective technique and vision method is proposed. Several round retro-reflective marks are placed on some defined positions of the frame as mark points which can precisely describe the shape of the frame. The marks are illuminated by laser beams and the image of the marks is captured by a camera. The positions of the marks on the camera are determined by designed image process program. Experimental results show that the whole process can be finished within 0.1 second. The designed system can measure the deformation of up to 50mm and the accuracy of the measurement is better than 0.02 mm.
Measurement of manufacturing resolution for two photon polymerization structures with different manufacturing parameters
Tien-Tung Chung, Wan-Jou Li, Sheng-Yuan Chen, et al.
This paper studied manufacturing resolutions of micro structures made by two photon polymerization (TPP) technology with different manufacturing parameters. The light source used for the TPP manufacturing system was a low-cost 532 nm Nd:YAG green laser, and the material used was commercial resin Photomer 3015. Two objective lenses, one with magnification of 100 times (100x) and numerical aperture (NA) of 1.3 and the other with 50x and NA0.8 were used in TPP production. The manufacturing resolution, which is also named as voxel size, changed with different manufacturing parameters such as laser power and exposure time. The measurement results of TPP structures manufactured with different manufacturing parameters indicated that the minimum line width produced by the 100x-NA1.3 lens could be reduced down to 67 nanometer (nm), which was quite good for TPP systems with low-cost Nd:YAG laser.
Calibration of positional consistency between mechanical shaft and electronic boresight for radar antenna
Li Jiang, Dong-wei Wang, Yong Liu, et al.
By fixing a glass cubic prism facing an antenna, the positional relation between the coordinates of the cubic prism and the mechanical shaft was measured in a lab for the antenna, and the positional relation between the coordinates of the cubic prism and the wave was measured in a microwave anechoic chamber. The positional relation between the antenna and the wave was used to calibrate the positional consistency between the mechanical shaft and the electronic boresight. The calibration uncertainty was calibrated by analyzing the measurement data collected in the lab and the microwave anechoic chamber. Experimental results indicated that the proposed method could be used to calibrate the positional consistency between the antenna and the electronic boresight of a radar system, and the calibration results are within the accuracy limits for radar antennas.
A new wideband interference suppression method for GNSS system
Yan Bai, XiaoChun Lu, Tao Han, et al.
GNSS navigation system has a shortage—the satellite navigation signal is vulnerable to various interferences and thus leads to losses in performance of received signal. Wideband interference is common oppressive which impact on the receiver performance badly. In this paper, aiming at the linear frequency modulation (LFM) wideband interference, a new interference suppression method based on NEW-MDCFT is presented, and the model and implementation method of the suppression algorithm have been introduced. By adding the LFM jamming to the COMPASS B1 signal, the interference suppression method is simulated, and time domain performance, frequency domain performance, acquisition performance and tracking performance of the signal before and after interference suppression have been given. The results indicate that, the suppression method based on NEW-MDCFT has good LFM interference suppression performance and is able to perform good interference suppression in seriously-interfered environment.
Influence of measuring algorithm on shape accuracy in the compensating turning of high gradient thin-wall parts
Tao Wang, Guilin Wang, Dengchao Zhu, et al.
In order to meet the requirement of aerodynamics, the infrared domes or windows with conformal and thin-wall structure becomes the development trend of high-speed aircrafts in the future. But these parts usually have low stiffness, the cutting force will change along with the axial position, and it is very difficult to meet the requirement of shape accuracy by single machining. Therefore, on-machine measurement and compensating turning are used to control the shape errors caused by the fluctuation of cutting force and the change of stiffness. In this paper, on the basis of ultra precision diamond lathe, a contact measuring system with five DOFs is developed to achieve on-machine measurement of conformal thin-wall parts with high accuracy. According to high gradient surface, the optimizing algorithm is designed on the distribution of measuring points by using the data screening method. The influence rule of sampling frequency is analyzed on measuring errors, the best sampling frequency is found out based on planning algorithm, the effect of environmental factors and the fitting errors are controlled within lower range, and the measuring accuracy of conformal dome is greatly improved in the process of on-machine measurement. According to MgF2 conformal dome with high gradient, the compensating turning is implemented by using the designed on-machine measuring algorithm. The shape error is less than PV 0.8μm, greatly superior compared with PV 3μm before compensating turning, which verifies the correctness of measuring algorithm.
The precision measurement and assembly for miniature parts based on double machine vision systems
X. D. Wang, L. F. Zhang, M. Z. Xin, et al.
In the process of miniature parts’ assembly, the structural features on the bottom or side of the parts often need to be aligned and positioned. The general assembly equipment integrated with one vertical downward machine vision system cannot satisfy the requirement. A precision automatic assembly equipment was developed with double machine vision systems integrated. In the system, a horizontal vision system is employed to measure the position of the feature structure at the parts’ side view, which cannot be seen with the vertical one. The position measured by horizontal camera is converted to the vertical vision system with the calibration information. By careful calibration, the parts’ alignment and positioning in the assembly process can be guaranteed. The developed assembly equipment has the characteristics of easy implementation, modularization and high cost performance. The handling of the miniature parts and assembly procedure were briefly introduced. The calibration procedure was given and the assembly error was analyzed for compensation.
Detection of wheel rim by immersion scan of phased array ultrasonic flaw testing
Yi-He Cai, Jian-qiang Guo, Ze-yong Wang, et al.
In order to achieve the in-service detection to high speed train wheel rims, this article analyzed the effects of the number of array elements to image focusing and image quality using water immersion ultrasonic phased array technology. Also, the effects of the depth of water to detecting technique had been researched. According to the results of the experiments, the number of optimal array elements, the corresponding thickness of immersion layer, and the optimal range of water’s depth had been obtained. Thus, appropriate references had been provided to water immersion ultrasonic phased array testing.
Experimental study on imaging spectrometer focusing formula in orbit
Hong-tao Ma, Hui Jin
Experimental verification for a focusing mechanism of imaging spectrometer is studied. The mechanism uses stepper motor driven precision harmonic drive. Wave generator is composed of elliptical cam and a flexible bearing. The output end is connected with the ball screw rotary motion into linear motion, which drives the focusing lens linear guide reciprocating motion. In view of the practical application of the mechanism in the imaging spectrometer, the thermal optical experimental imaging spectrometer has been focusing the formula. Data show that the focus formula ensures linear relationship between the focal plane position and temperature. The linear relationship shows that the imaging spectrometer onboard the variation with temperature and automatic focusing is very important.
Stiffness modeling of flexible suspension structure for displacement measurement probing sensors
In order to solve the problem of performance analysis and optimal design of flexible suspension structure for displacement measurement probing sensors, a novel theoretical model of stiffness with high accuracy is proposed. Both displacements constraint and angle constraint of elastic diaphragms are considered during modeling, and a stiffness equation including all dimensional parameters and material characteristics of elastic diaphragms is obtained. Thus the stiffness of the flexible suspension structure is modeled theoretically and accurately, and the influence on performance of probing sensors by each parameter can be analyzed. Simulations results show that the theoretical model of stiffness proposed is more accurate than existing models, and performance analysis and optimal design of probing sensors can be carried out based on it.
Research and development of novel wireless digital capacitive displacement sensor
In order to solve the problem of noncontact, wireless and nonmagnetic displacement sensing with nanometer resolution within critical limited space for ultraprecision displacement monitoring in the Joule balance device, a novel wireless digital capacitive displacement sensor (WDCDS) is proposed. The WDCDS is fabricated with brass and other nonmagnetic material and powered with a small battery inside, a small integrated circuit is assembled inside for converting and processing of capacitive signal, and low power Bluetooth is used for wireless signal transmission and communication. Experimental results show that the WDCDS proposed has a resolution of better than 1nm and a nonlinearity of 0.077%, therefore it is a delicate design for ultraprecision noncontact displacement monitoring in the Joule balance device, meeting the demand for properties of wireless, nonmagnetic and miniaturized size.
A novel active suppression technology against thermal drift for ultra-precision spherical capacitive sensors
In order to solve the problem of thermal drift and further improve the performance for sensors with extreme demand for precision, based on analysis of shortcomings of existing compensation methods and characteristics of thermal drift, a novel active suppression technology against thermal drift is proposed. Considering the change of properties of reference elements in sensors caused by temperature variation is the most major factor that introduces thermal drift error, a special thermal structure is designed to provide a small environmental chamber with sub-structure design of high performance heat isolation, heat conduction and homogenization of temperature, and the temperature in the environmental chamber is controlled with high precision based on bilateral temperature adjusting with thermo electronic cooler (TEC) devices, and a compound control algorithm of Bang-Bang and anti-windup PID. Experimental results with an ultra-precision spherical capacitive sensor show thermal drift error is significantly eliminated and the precision of the sensor can reach the level of several resolutions.