Proceedings Volume 11053

Tenth International Symposium on Precision Engineering Measurements and Instrumentation

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Proceedings Volume 11053

Tenth International Symposium on Precision Engineering Measurements and Instrumentation

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Volume Details

Date Published: 7 March 2019
Contents: 2 Sessions, 175 Papers, 0 Presentations
Conference: 10th International Symposium on Precision Engineering Measurements and Instrumentation (ISPEMI 2018) 2018
Volume Number: 11053

Table of Contents

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Table of Contents

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  • Front Matter: Volume 11053
  • Tenth International Symposium on Precision Engineering Measurements and Instrumentation
Front Matter: Volume 11053
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Front Matter: Volume 11053
This PDF file contains the front matter associated with SPIE Proceedings Volume 11053, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.
Tenth International Symposium on Precision Engineering Measurements and Instrumentation
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Development of optic-electronic autocollimators for monitoring the angular displacements of large objects
Igor Konyakhin
Ways of improving autocollimators for monitoring angular displacements are analyzed. The results of an analysis of control elements based on tetrahedral reflectors with flat reflecting sides are presented. The technical characteristics of experimental models of control elements are presented. The features of tetrahedral reflector as the control elements for three-axis autocollimators are discussed.
Development of auto defect inspection system for cell phone silicone rubber gasket
Chao-Ching Ho, Jhih-Jia Lu
This paper proposes a machine-vision-based system for the inspection of the geometrical features of cell phone rubber gaskets. The system consists of two industrial cameras and an industrial computer. To begin the inspection process, the cell phone gaskets inside the camera field were identified and a novel transparent fixture were employed to guide the lighting to highlight the defects. To characterize the metrological features of cell phone gaskets, image preprocessing procedure was then implemented and defect classification algorithmic strategies was described in detail. Finally, experimental results on images of different type of the cell phone gaskets are reported together with the metrological classification of the proposed measurement system. The geometrical quality of every individual silicone rubber gasket, which could be evaluated and guaranteed to the full grade of assessment which the proposed system can achieve.
Review of the opaque coolant barrier removal techniques for in-process form profile optical measurement
J. Zhu, Y. Gao
In-process measurement can provide feedback for control of workpiece precision in terms of size, form error, and roughness. It can be used for precision control of a machining process, therefore to improve productivity and reduce defect rates. Optical measurement methods have greater advantages in the in-process form profile measurement systems due to their non-contact type and high precision. However, use of opaque coolant in precision machining will introduce an opaque barrier problem, making the workpiece surface y(x, z) inaccessible to the optical measurement devices. To solve this problem, several approaches, including the water beam approach, the single air beam approach, the multiple air beam approach, and the dual coolant displacing medium method, are examined in terms of coolant removal capability, level of acceptance to surface complexity, flow rate and velocity of the coolant displacing media, and also errors induced by the coolant removal methods. The results of the study show that the multiple air beam method and the dual coolant displacing media method are more advantageous than the other methods.
Holographic fabrication of two-dimensional scale gratings for surface encoder by using an orthogonal type two-axis Lloyd's mirror interference lithography
Xinghui Li, Haiou Lu, Weihan Yuan, et al.
In this paper, an orthogonal type two-axis Lloyd’s mirror interference lithography technique was employed to fabricate two-dimensional planar scale gratings for surface encoder application. The two-axis Lloyd’s mirror interferometer is composed of a substrate and two reflective mirrors, which are placed edge by edge perpendicularly. An expanded and collimated beam was divided into three beams by this interferometer, a direct beam and two reflected beam. The unnecessary beam section was blocked by a home designed filter. These two reflected beams interfere with the direct beam respectively, generates perpendicularly cross patterns for forming two-dimensional scale gratings. The two reflected beams also interfere with each other and generate an undesired grating pattern along a 45 degree direction, which influence the pattern uniformity in a certain degree. The undesired grating pattern can be eliminated by polarization modulation, yet which will influence the grating area. Theoretical and experimental study was carefully carried out to evaluate the fabrication quality with and without polarization modulation. Two-dimensional scale gratings with a 1 μm period in X- and Y-directions were achieved by using the constructed experiment system with a 442 nm HeCd laser source. Atomic force microscope (AFM) images and diffraction performances verified that the two-axis Lloyd’s mirror interferometer with a small undesired interference between two reflected beams under an order of nominal value of 0.1 can provide a better fabrication result for scale gratings application.
Autonomous time synchronization method of wireless ad hoc sensor network and its implementation on CC1350 system
Sili Liu, Jianyun Chen, Jiahao Li
Wireless ad hoc sensor networks have been used more and more in recent years, and they are mainly used in the continuous monitoring of complex environment. The low power and dual frequency characteristics of the SimpleLink CC1350 LaunchPad micro control platform are very suitable for the research of wireless ad hoc sensor networks. Because the synchronization of each node clock is the premise of the normal work of wireless sensor network, this paper mainly studies the time synchronization problem of CC1350 development board. In this paper, the advantages and disadvantages of the existing time synchronization methods are analyzed, then the LTSP algorithm is selected at the end, and the experimental verification is carried out on MATLAB software platform and CC1350 system. The experiment result shows that the time synchronization precision and extensibility of the algorithm can meet the requirement of networking.
Multi-matrix optic-electronic systems for measuring the line shifts of the points on the radio-telescope main mirror
Igor Konyakhin, Minh Hoa Tong
The mirror construction of the radiotelescope RT-70 (Suffa) for millimetre wave range requires measuring the line deformation of mirror's surface. Following issues dealing with this problem are described in this article: 1) the possibility of the design of deformation measurement system based on triangular method 2) the new scheme of optic-electronic measurement system. The great attention during the research was paid to the experimental approval of the theoretical results. The model of the described system had the following characteristics: infrared emission diode AL107B by power 15 mWt as sources of radiation; the objective by the focal length 405 mm as aperture of receiver video-camera, the CMOS matrix receiver by type OV05610 Color CMOS QSXGA with 2592*1944 pixels and one pixel size (2.8*2.8) μm2 produced OmniVision as image analyzer . The computer simulation error and the experimental error measurement was 0.05 mm at the range 30 mm on a working distance 25 m, which allows measuring the deformation of radiotelescope construction with the mirror diameter 70 m.
All-optical difference engine for in-process defect inspection for roll-to-roll printed electronics
The increasing capabilities of roll-to-roll (R2R) printing processes present challenges for quality control, requiring inprocess inspection of large substrates with high resolution at high speed. In this paper, an all-optical difference engine (AODE) sensor has been developed for in-process defect inspection for R2R printed electronics. The AODE sensor achieves high-speed inspection by utilising the principle of coherent optical subtraction to minimise data processing. The capability of the developed sensor is demonstrated using industrial printed electrical circuity samples and the sensor is capable of inspecting areas of 4 mm width with a resolution of the order of several micrometres.
Measurement of 3-dB linewidth of FBG Fabry-Perot interferometer using tunable fiber laser
Dajuan Lyu, Peide Liu, Yifei Ma, et al.
We present a simple method to measure the 3 dB linewidth of the sharp peak in the spectrum of the fiber Bragg gratingbased Fabry–Perot (FBG-FP) interferometer. A narrow linewidth tunable laser is used for sweeping the FBG-FP to achieve the reflection spectrum. A triangle wave is used to drive the narrow linewidth tunable laser. The linewidth of the sharp peak is measured with a resolution of 0.001 pm.
Sensing the atmosphere of coastal areas of laser detection methods
In this paper, a weather phenomenon called a hurricane is considered. Major components areconsidered and selected. After the analysis of the components, the indicator substances are chosen, according to which the detection of the incipient phenomenon will be carried out in the future. The method of remote sensing is considered for detecting small concentrations of indicator substances in the air. The sounding area is chosen to study the atmosphere for the presence of indicator substances. The results of calculating the backscattering power for some indicator substances are presented, depending on the range.
Research of the polarization-optical parameters of a solid-state matrix photomultiplier
The work is devoted to the research of the polarization-optical parameters of a solid-state matrix photomultiplier. The main parameters of the performance of the SiPM form from the sensitivity of the photodetector. As an object of study, a silicon photomultiplier ARRAY-C 60035-4P was chosen, which consists of 4 photosensitive sites. The pixels of the SiPM are avalanche photodiodes that are separated from each other by elements that do not participate in the formation of the useful signal and serve to suppress the secondary optical signal due to the optical coupling between. In this paper, experimental studies of the state of polarization reflected from the surface of each of the active regions of the matrix of a silicon photomultiplier are performed using a laser photoelectric ellipsometer LEF-3F-1. The action of the ellipsometer is based on the zero method of determining the polarization angles. In the course of the experiment the contractions of ellipsometric angles were determined. The experiment was carried out at four angles of incidence on the surface of the receiver, which corresponds to a set of reflective characteristics of a silicon photoelectric multiplier. With the help of these data, the estimation of the distribution of the reflection and transmission coefficients becomes possible, as well as the sensitivity distribution over the different sites of the SiPM.
A fast infrared thermal imaging detection method based on spatial correlation
Libing Bai, Xue Chen, Yuhua Cheng, et al.
The existing infrared thermal imaging detection methods usually process the whole video stream data collected by a thermal camera, which involve large amounts of data and have a negative effect on the efficiency of defect detection. In this paper, we propose an infrared thermal imaging detection method which considers the spatial correlation of the adjacent images in the video stream data. By extracting the edge information and analyzing the correlation between two adjacent frames, the defect area and the non-defect area show different correlation coefficients, and only part of the video data is required for defect detection. Furthermore, the fusion method is introduced to enhance the image quality. The experiment results demonstrate that the proposed method can not only reflect the change of heat in the defect area during the heating process but also reduce computation time involved in the subsequent processing.
Research and application of a novel randomly encoded hybrid grating interferometric wavefront sensor
Yongying Yang, Rui Zhang, Zijian Liang, et al.
In this paper, a novel randomly encoded hybrid grating (REHG) interferometric wavefront sensor with the features of high-precision, high-resolution, high-dynamic-range and anti-vibration is proposed. The REHG consists of a randomly encoded binary amplitude grating and a phase chessboard. The far filed Fraunhofer diffractions only contain ±1 orders in two orthogonal directions. Different from the cross grating lateral shearing interferometer (CGLSI), there is no need of order selection mask for quadriwave lateral shearing interference. Without the influence of periodical Talbot effect, a continuously variable shear ratio can be obtained with the REHG, which makes it possible to control the dynamic range and measurement sensitivity of the wavefront sensor. A high-precision calibration method for shear ratio based on the shearing wavefront feature extraction and the generalized wavefront retrieval algorithm are employed to ensure the accuracy of the wavefront measurement results. The REHG wavefront sensor can work in collimated beam and convergent beam modes. Due to self-referenced and common-path characteristics, the REHG wavefront sensor can applied to different application fields in situ. Compared to the ZYGO interferometer, the results of the optical aberration and spherical surface measured by the REHG are highly precise and also show good repeatability. By applying two REHG wavefront sensors with different shear ratio, a wideband sensitivity-enhanced interferometric microscopy with real-time visualization can retrofit existing bright-field microscopes into quantitative phase microscopes.
Energy analysis method of the laser tracing measurement optical system
This paper proposes an energy analysis method of the laser tracing measurement optical system. Based on the principle of the laser tracing measurement optical system, an energy model is established to analyze the effects of non-ideal optical elements on the energy of the optical system. The simulation results show that the interference pattern is the most obvious when the split ratios of the beam splitters in the interference part and the tracing part are respectively 6:4 and 7:3. Under the above split ratios, the interference signal energy values of four receivers are close to each other and the visibility of fringe pattern reaches 0.99. The visibility of fringe patterns of four interference signals is reduced when the reflectivity of all polarization beam splitters is under non-ideal conditions in an entire optical system. The non-ideality of the transmittance of the polarization beam splitters does not affect the visibility of fringe patterns. The paper provides the theoretical basis for the accuracy improvement, reliability evaluation, optical system design and the selection of optical elements of laser tracing measurement systems.
Precision assessment of high-speed railway slab intelligent inspection system
With the rapid development of high-speed railway, there are many problems with the traditional railway slab assessment method. The traditional method is slow, and its precision is limited by the precision of specified tools for railway slab inspection. Scholars have developed a variety of inspection systems for railway slab geometry. Since those systems’ precision assessment relies on railway slab testing tools that are complex for operation, this paper proposes a novel method to assess the precision of an intelligent slab inspection system itself by using the spatial position deviation between the point cloud of a benchmark slab and the corresponding digital 3D model. The proposed method takes the RMSE of the deviation value of points in the key surfaces as the evaluation index. The key surfaces are the two shoulder surfaces and the rail-bearing surface of the rail-bearing platform, which can be extracted by the region growing algorithm associated with surface normals. Based on the real point cloud processed by an intelligent slab inspection system, the experimental results show that the system can align the slab point cloud to its corresponding 3D digital model. The deviation is distributed on the model uniformly, and its precision is 0.1 mm. In addition, this procedure is consistent with that of general slab inspection and can be used as a self-verification tool for daily precision evaluation of the system itself.
Equivalent circuit model based on the average period for periodic overlapping circle metallic mesh
Yongmeng Liu, Cuilian Zuo, Chuanzhi Sun, et al.
The equivalent circuit model based on the average period for periodic overlapping circle metallic mesh is proposed in this paper. The equivalent reactance coefficient b in the equivalent circuit model is revised according to the simulation results of Ansoft designer software. In order to guide the optimization of the electromagnetic shielding effectiveness of periodic overlapping circle mesh, the effects of the diameter 2R and period g on the electromagnetic shielding efficiency were simulated and analyzed. The simulation results show that the electromagnetic shielding effectiveness is better than 22dB in the 2-18GHz band. The periodic overlapping circle mesh can be applied to the area where the strong shielding effectiveness,high optical transmittance and low image-degradation are required simultaneously.
Process optimization: internal feature measurement for additive-manufacturing parts using x-ray computed tomography
X-ray computed tomography (CT) is a non-destructive approach to verify internal features of various industrial components built by additive manufacturing (AM) or other processing methods. However, the measurement results was highly impacted by numerous factors. In this study, DoE (Design of Experiments) was conducted to statistically study impacts of error source of X-ray CT metrology; optimal settings were recommended for different internal geometrical features. Measurement comparison between X-ray CT and CMM (Coordinate Measuring Machine) is also provided in this paper to analyze the principle difference of these two measurement technology.
Statistical measurement method of the standard particles through airborne particle counter based on FESEM
Zhiliang Gao, Qizheng Ji, Jian Chen, et al.
The traceability of cleanness parameter has received high attention from the metrology industry of light-scattering airborne particle counter. Based on the metrology method of the big particle concentration and the traceability method of airborne particle counter’s counting performance on small particle size by statistical analysis, this paper tries to build a coordinate system of the particles distribution on anodic aluminum oxide (AAO) membrane through the counter, choose the statistical samples by aerodynamics, observe these samples on membrane by field emission scanning electron microscope (FESEM), evaluate the uncertainty of measurement on standard particle statistics, analyze the uncertainty range and the key affecting factor, and put forward a method of improving statistics accuracy in process control. The test results prove that the method has important value on improvement of the theory of the cleanness traceability system based on FESEM and statistical analysis.
Method for high-precision distance estimation and dispersion mismatch compensation in frequency scanning interferometry
Hao Pan, Xinghua Qu, Fumin Zhang
The long fiber frequency sampling method has been widely used to eliminate the nonlinearity of laser tuning in the frequency-modulated continuous wave laser ranging technique. Then, fast Fourier transform (FFT) is performed on the resampling signal to obtain the distance spectral information. However, due to the picket fence and leakage of FFT-based methods, it is hard to find the precise location and achieve better range precision. In this paper, we propose a novel frequency estimation method, multiple signal classification (MUSIC), to be used instead of the conventional fast Fourier transform (FFT)-based algorithm to obtain better range precision. In addition, the induced-fiber dispersion could also lead to poor accuracy and precision in the large-bandwidth and long-distance measurements scenes. To solve this problem, a phase compensation method for resolution-enhancement is proposed.
Development of surface profile measurement system based on super luminescent diode light source
Dian Bian, Xinyu Yan, Yang Lu, et al.
This paper dedicated to the development of a surface profile measurement system based on the SLD (Super Luminescent Diode) light source for silicon wafer. The silicon wafer is very important as a substrate of semiconductor products such as integrated circuit (IC) chips, light emitting diodes (LEDs), solar cells and MEMS devices [1] . In this paper, Michelson interferometer is used to generate double beams in order to achieve interference. According to the acquired interference fringe image, we obtain the surface profile of the tested silicon wafer. As a light source, SLD has good spatial coherence and due to its higher transmittance to silicon wafers than other wavelength sources, high fringe visibility can be achieved. It can also perform a full scan in a larger step and achieve rapid on-line measurement of the target surface.
The optimization of segment’s axial support point for large astronomical telescopes
Yongfeng Song, Liangzhou Chen, Chang Song, et al.
Existing axial support for segments mostly adopts the Whiffletree support mode. The location of the support point will have a great influence on the surface precision of the primary mirror, and then influence the final imaging quality of the telescope. At present, there is no special support technology for traditional and thin mirror.In this paper, the research is based on LOT’s hexagonal segment (the surface is hyperboloid, diagonal line is 1.2m, thickness is 45mm, material is Zerodur), which is designed by Huazhong university of science and technology. The optimization of the Whiffletree axial support point of the segment is carried out. Efficient optimization algorithm is used in the research. After building parameterized model of segment support point location, FEM is used to obtain segment surface deformation. Taking the minimum RMS of deformation on segment surface under gravity as the goal, optimized software ISIGHT is applied to find the best support point location. Zernike orthonormal polynomials for hexagonal pupils is used to remove rigid-body motion. Finally, the best support point location point is obtained, the RMS of the segment surface deformation is 11.56nm and the PV is 63.98nm. The result can meets the requirement of LOT design well.
Multiple-exposure adaptive selection algorithm for high dynamic range 3D fringe projection measurement
Haihua Cui, Zhaojie Li, Wei Tian, et al.
In order to cover the high dynamic exposure range requirement of high reflective surface, a multiple-exposure adaptive selection algorithm of phase shifting 3D measurement is developed. At first, the camera response curve function is calibrated with the sequence images of different exposure times. The nonlinear curve function shows the relationship between the image intensity value and exposure amount. The relative irradiance value of all the image pixels is computed based on the linear relation between the exposure time and exposure amount. Both relative irradiance value cover the highest and lowest gray value of the fringe image is set the threshold. Then, the adaptive selection algorithm for exposure time is proposed based on the double threshold principle. At last, different exposure time node is selected adaptively. The sequences images with multi-exposure time are fused. In order to evaluate the performance of this method, some typical metal parts and blade with high range of reflectivity surfaces are used for 3D measurement and construction. The experiment results verify the feasibility of the proposed method.
Applications of wavefront modulation devices in aspheric and freeform measurement
Qun Hao, Yan Ning, Yao Hu
Wavefront modulation devices are of great significance in optical information processing systems. These devices capable of phase modulation are used in a variety of optical applications: wavefront correction, optical metrology, adaptive optics, aberration compensation, etc. The liquid crystal spatial light modulators (LC-SLMs) and deformable mirrors (DMs) have been regarded as the promising device for their flexibility and programmability on wavefront modulations. This paper presents applications of LC-SLMs and DMs when they are used as aberration compensators in testing of aspheric and freeform. Besides, a pixel-wise method based on analysis of the phase maps obtained by a Fizeau interferometer for calibrating the phase modulation characteristics of the LC-SLM is proposed. A PLUTO-VIS-020 LC-SLM produced by the Holoeye Company is employed in the calibrating experiment. A Zygo interferometer based on Fizeau interference theory is also employed. The experimental results demonstrate that the phase modulation characteristics of LC-SLM and a specific lookup table (LUT) for every pixel of the LC-SLM aperture can be obtained by utilizing the proposed method with convenience and high efficiency. The device calibrated in this paper provides a high phase shift up to 6π at 632.8nm wavelength and has a linearized phase distribution. It coincides well with the average modulation curve offered in the manual of the device. This paper provides a simple and accurate method for pixel-wise phase modulation characteristics calibration.
Dual-wavelength off-axis quasi-common path digital holography using polarization multiplexing and flipping
We build a two-wavelength off-axis quasi-common-path digital holography for quantitative phase imaging (QPI) using polarization-multiplexing and flipping. The interference is performed by flipping the relative position of a sample and reference beam, and the dual-wavelength information is spatially multiplexed onto a monochromatic CCD camera simultaneously using polarization-multiplexing. Due to orthogonal interference fringes of two-wavelengths, the unwrapped information on the phase and thickness for the sample can be extracted from a single interferogram. Our setup requires no pinholes, gratings or dichroic mirror with straightforward alignment. Additionally, a division algorithm for dual-wavelength off-axis digital holography with the help of a specimen-free multiplexed interferogram is proposed to extract the phase of a specimen. We demonstrate the operation of the setup with step target and circular pillar.
Micro-LED optical engine with biologically inspired artificial compound eyes for pico-projection display
Light emitting diodes (LEDs) have recently gained much interest as projection light sources. In this work, a compound parabolic concentrator (CPC) coupled to a biologically inspired compound-eye array is designed and fabricated as a light collection engine of a pico-projector. The results indicate that more than 90% light emitted by a monolithic LED array can be collected by the CPC coupled to a compound-eye array and transmitted within the designed angle. This method is advantageous in many respects compared with those available, such as compact volume, high collection efficiency, rectangular radiation pattern and controllable output divergence angle. The result validates that the system reaches a collection efficiency of 87% of micro-LED emitted light. Moreover, the beam collimation quality has been analyzed obtaining a residual divergence of less than 2º. Thus, the results achieved by the proposed optical system improve those obtained with several commercially available devices.
Real-time 3D shape measurement by fringe projection and GPU parallel computing
When fringe projection profilometry is applied for real-time 3D shape measurement, several problems remain to be solved such as multi-wavelength heterodyne phase unwrapping is sensitive to motion and the computation cost is high. In this paper, a real-time 3D shape measurement method with optimized multi-wavelength heterodyne phase unwrapping and GPU parallel computing is proposed. Experimental results demonstrate that the proposed method can acquire 3D shape at 40 fps. Dynamic object with discontinuities can be measured and the phase unwrapping mistakes are eliminated by smoothing the phase of beat frequency during multi-wavelength heterodyne phase unwrapping.
A new non-contact coordinate measuring machine equipped with light-duty optical probe based on fringe projection profilometry
In the modern industrial manufacturing, how to effectively obtain the three-dimensional data of the parts profile is the key component for precision test and subsequent analysis. A light-duty design scheme for optical vision probe, which can be installed with a PH10T motorized probe head in CMM, is discussed in this paper. The optical probe can overcome several defects of the traditional measurement mode of CMM, such as poor efficiency and sparse point cloud. Therefore, the problem of 3D measurement and quality analysis for complicated parts can be solved. To splice data in different fields of view, a registration method using a new designed artifact is proposed. Experiments demonstrated the feasibility of the designed non-contact CMM integrated with optical 3D probe for precise 3D shape measurement. The measurement uncertainty of the optical probe can reach 0.012mm within the measuring volume width 200mm and the measurement uncertainty of the global 3D measurement is less than 0.03mm in 1500mm.
The measurement technology for precision peg-in-hole assembly
Xiaodong Wang, Xingyuan Wang, Tongqun Ren, et al.
Measurement is the prerequisite technology for assembling precise devices in order to guarantee the quality requirements. As a typical category of assembly, peg-in-hole is the most widely employed assembly method in industrial fields, including precision instruments and machinery. Some of the measurement problems and solutions of two major categories of the peg-in-hole assembly, i.e. clearance fits and interference fits, were discussed. The parts to be assembled are small in size. The precision clearance fits require mating surfaces to avoid collisions during assembly; for the precision interference fits, the mating surfaces should not be damaged or generating abrasive chips during press-fit. The hole-shaft alignment and attitude adjustment are the main task need to be carried out precisely in assembly. Furthermore, real-time monitoring and connection strength measurement is also the important for interference fit assembly. Therefore, the purpose of this paper is to achieve precise hole-shaft alignment and attitude adjustment of these two kinds of fits and to real-time monitor the assembly process, as well as connection strength assessment of the interference fit. Two assembly instruments were built for interference fits and clearance fits to achieve precise alignment, attitude adjustment, and real-time monitoring. In addition, an ultrasonic testing apparatus was built to evaluate the connection strength. After calibration, the precision press-fit instrument can achieve high assembly accuracy and demonstrated with experiments. The prediction results of connection strength are in good agreement with experimental results with a relative error less than 20%. Furthermore, the instrument for clearance fits was also designed and introduced.
A novel breakpoint detection method based on dynamic programming for linear laser scanner
Xiao-qia Yin, Wei Tao, Hui Zhao
Linear laser scanner has been widely used in industrial applications, such as 3D reconstruction. Breakpoint detection of the laser stripe centerline is a fundamental step. In practical applications, the centerline is always not perfect due to various noises. A novel breakpoint detection method named Fixed Dynamic Programming (FDP) is proposed. Firstly, the centerline fitting error is illustrated in detail, which is to be used as the criterion in the FDP. Secondly, principle of the FDP method is described, which modified the traditional DP method by utilizing the foreknown breakpoints information of the centerline. Finally, experiment is implemented to detect breakpoints of the noisy laser stripe centerline by using a linear laser scanning system. From the experiment result verifies that the prosed FDP method can avoid the influence of noise and improve the computation efficiency.
Establishment of standard device for high rotational speed generation
Qiao Sun, Jie Bai, Lei Du, et al.
The high rotational speed standard device based on brushless DC coreless micro motor and FPGA technology for highaccuracy rotational speed control was investigated and established, with resolution of 1 r/min in the measurement range of 40000 r/min to 100000 r/min. The expanded calibration uncertainty of this standard device is 1×10-5, k=3 The structure of the device and key technology involved were described.The dual closed-loop control solution was explained. The calibration results were provided.This high rotational speed standard device is used as an important working standard for the feasible traceability of high-precision optical tachometers and rotational speed measuring instruments at measurement range above 40000 r/min.
A two-probe linear encoder by using an arrayed scale grating stitched by multiple separate short gratings
Xinghui Li, Weihan Yuan, Kai Ni, et al.
A line encoder composed of a two-probe reading head an arrayed scale grating stitched by multiple separate gratings was proposed, constructed and evaluated in this research for expanding the measurement range. The scale grating is stitched by multiple separate short gratings fabricated by a holographic lithography that is able to provide sub-micron order grating period. Differing from the conventional stitched grating, in which the gap of the adjacent two gratings should be strictly controlled so that a continuous phase can be ensured, the gap in this research is not necessary to be controlled, neither the gap width nor the phases, by using a two-probe reading head. In contrast to the reading head in conventional linear encoder, the two-probe reading head was designed in such a manner that a collimated laser beam with a diameter of 1mm was divided into two parallels probes (probe A/B) by a specially designed prism lens. These two probes are projected perpendicularly onto the transmission type arrayed scale grating. Taking probe A as an example, after passing the grating, the positive and negative first-order diffraction beams follow a typical grating interferometry principle, including propagating direction changing, co-path by a beam splitter and a polarize for a phase delay module and finally interfere with each other, from which the displacement can be obtained. The two probes propagate along similar optical path. The two probes can ensure as least one can be projected onto the grating. By stitching the two probe outputs suitably, the continuous output of the scale grating can be measured accurately. The jig for stitching the separate gratings was investigated and tested. The two-probe reading head prototype was constructed and evaluated.
GMA internal magnetic field measurement based on FBG
A method to measure the magnetic field inside the Giant Magnetostrictive Actuator (GMA) is proposed. Improved Preisach Model is applied to eliminate the unavoidable nonlinearity error in the measurement. The effect of temperature on measurement can be eliminated by double Fiber Bragg Grating (FBG) structure. The double-sagnac loop combined with Polarization Maintaining Fiber (PMF) is used to demodulate the center wavelength. Sensing model of the FBG is established to realize temperature compensation for the measurement system. Experiment results show that resolution of 2.1×10-4 T can be achieved over a range of 127 mT, and the repeatability of overall measurement is 0.227%. Therefore, the proposed method can be used to measure the internal magnetic field of GMA effectively and reliably.
Development of hybrid measuring system for the complex micro-arrayed surface
Tong Guo, Zhenshan Sun, Jinping Chen, et al.
As the ultra-precision machining technology is developing in various directions and evolving into a higher level, the micro-nano measurement technology is also developing constantly. According to the different manufacturing processes and texture of measurement objects, the requirements of micro-nano measurement technology vary a lot. Optical Microscopy (OM), Scanning Probe Microscopy (SPM) or Scanning Electron Microscopy (SEM) cannot meet requirements of high efficiency, high resolution and three-dimensional morphology characteristics obtaining at the same time. Hence a hybrid measuring system including the Atomic Force Microscopy (AFM) and vertical scanning white-light interferometry is built. The measurement function of the dual feedback AFM system was verified by scanning a one-dimensional grid and the measurement function of white light vertical scanning interferometer was verified by measuring the step structure and comparing it with a three-dimensional optical profiler. And then the micro-arrayed structure is measured by white light vertical scanning interferometry. The vertices of the micro-arrayed unit structure is scanned by using AFM in the same coordinate system to verify the complex measurement function of the system on the complex micro-arrayed surface.
Error analysis of target trajectory tracking applied for measurement of high speed spindle
Jin An, Jiamin Chen, Wenguo Yang, et al.
The measurement of spindle radial error motion is achieved based on target trajectory tracking (TTT). Error analysis of TTT method is performed in this paper. Target trajectory doesn’t contain information about axial error motion. The tilt error motion is included in the target trajectory. However, the tilt error motion is small enough to be ignored. The roundness error of the target trajectory is assessed to obtain the radial error motion of the spindle. The experimental results confirm that the proposed method can be applied to measure the radial error motion of a high-speed spindle having a maximum rotational speed of 6000r/m.
Online vision system for battery FPC connector defect detection based on active shape model template matching
Zhuo Zhao, Bing Li, Fei Gao, et al.
In this paper, a quality detection method for battery FPC (Flexible Printed Circuit) connectors based on active shape model template matching is proposed. It can deal with different kinds of connector appearance defects. Firstly, construct template data set of connector, acquire test images and apply cutting operation to original image, then execute tilt correction and image reconstruction by means of least square method and affine transformation to fulfil the pre-processing stage. Then, match and locate connector region in per-processing image with the help of the active shape model (ASM) based template matching method. To deal with different kinds of defect (soldering offset/tilt, exposed copper clad layer in FPC, broken edge in FPC, defects in center area of connector, defects on metal and plastic components), independent detection algorithm units are integrated in the system. Template can also be real-timely updated according to detection result. Finally, the defects will be classified, located and marked in detection image. In addition, aimed at the need of battery industry, a set of detection system with low cost, high performance and strong stability has been designed. It can be concluded from online and offline experiments that the proposed method is of high detection rate, good real-time performance and strong robustness.
Misalignment recognition of mass pan in joule balance
Joule balance is one of the precise instruments to measure the Plank constant for redefining the kilogram. During the measurement of the joule balance, two electrified coils produce an electromagnetic force to balance the gravity of a standard mass on the mass pan. However, if the mass pan is in a misalignment state, it will waggle and change the posture of the suspended coil during the mass exchanging progress. Then the alignment errors will be induced. In joule balance, the posture of the mass pan cannot be directly measured, which however can be decoupled by measuring the posture of the suspended coil. In this paper, the recognition method of the mass pan misalignment status will be discussed. By measuring and calculating the positon changing of the suspended coil, the alignment states of the mass pan can be evaluated.
The possibility of measuring low altitudes above the sea surface with pulsed laser altimeter under conditions of fog
D. T. Nguyen, E. G. Lebedko
This paper presents analysis of the possibility to design all-weather pulse laser altimeters for measuring lowaltitudes above the sea surface. We proposed special design features which consider the low reflection coefficient and the reflective properties of random rough sea surface. Backscattering by fog with various density was analyzed. With considering the reflection coefficient from the sea surface less than 4%, we proposed measurement method based on the drop of the backscattering signal. We examined the measurement range and measurement errors depending on the transfer function of the receiving-amplifying circuit for inertial and non-inertial detection. The energy compensation for specified measurement precision was carried out.
Improved design principle of Dyson concentric infrared imaging spectrometer
Qian Zhou, Peng Yan, Zhijie Yang, et al.
Dyson concentric configuration has advantages of 1:1 magnification ratio, compact size, light mass, large numerical aperture, less smile and distortion. However, volume of initial structure calculated by two-wavelength astigmatism method is relatively large. Meanwhile, we only obtain one smaller structure for long wavelength infrared range through another improved method widening aberrations. In this paper, we proposed improved design principle of Dyson concentric push-broom infrared imaging spectrometer, which can calculate all smaller initial Dyson structures satisfying requirements of spectral range and resolution in different infrared wavebands. First, obtain initial grating groove density using two-wavelength astigmatism. Then widening aberration, search all of initial Dyson structures satisfying ideal imaging condition under 1 to 10 times of initial grating groove density. Lastly, select infrared materials and detectors suitable for short infrared, medium-wave infrared and long-wave infrared wavebands respectively to demonstrate feasibility of this new method. As results shown, volume of Dyson configuration has reduced about 60% in short-wave infrared waveband, 77% in mid-wave infrared waveband, about 50% in long-wave infrared waveband. So improved design principle proposed in this paper benefits for infrared concentric imaging spectrometer. © 2018 Optical Society of America.
Two-dimensional reflective optical encoder based on point source illuminated grating imaging
A novel two-dimensional reflective grating encoder is introduced. The optical encoder is developed by a binary amplitude reflective scale grating and a two-dimensional slit displacement sensor, which is fabricated by MEMS technology. Based on Talbot effort, the proposed method can achieve millimetric measurement with high accuracy, where the displacement difference within 0.1% and 0.2% for 1 mm and 20 mm measurement, respectively. By using the eight-segment data division program, the proposed method can easily distinguish 1 μm displacement measurement. Furthermore, in measurement speed tests, the proposed method can reach the movement speed about 5000 μm/s. The experimental results showed the proposed method can achieve high resolution, high speed and long-range measurement, which is potential in the industries and workshops application.
Research of the temperature influence on the error rate of incremental optical-electronic encoders of linear displacements based on raster structures
The currently existing incremental optical-electronic linear displacement encoders (OELDE) use raster conjugation, which allows for the measurement of linear motion with high accuracy by means of the conversion of optical signals in the opto-electronic path. In such devices, informative signals constantly undergo transformations associated with their processing. Variable environmental factors, especially temperature, have a harmful effect on signal conversion processes and cause additional error. The aim is to analyze the results of theoretical and experimental studies of the additional error from the effect of changes in ambient temperature on incremental OELDE’s. Analyzing the effect of temperature on the course of information transformation, it is possible to divide the main emerging partial components of the additional error into two groups: - errors due to changes in the relative spatial position of the elements of the OELDE; - errors due to changes in parameters and characteristics of elements of the OELDE.
A domain adaptation deep transfer method for image classification
Yu Chen, Chunling Yang, Yan Zhang, et al.
The deep learning models have recently shown outstanding performance in many computer vision applications. However, this superior performance requires a very large number of annotated image samples, pre-venting application to problems with limited training data. To overcome this limitation, we propose a Do-main Adaptation Deep Transfer Model (DADTM) in this paper. The DADTM improves the classical transfer models by the proposed domain invariance value metric and a domain invariance reconstruction, increasing the model transferability and enhancing the classification performance. The comparative experiments are performed to evaluate the DADTM-based classification algorithm. The results show that the proposed mod-el and algorithm outperform the traditional methods.
Control circuit design of magnetic suspension stylus measuring instrument
Jianfei Zhou, Suping Chang, Chunbing Hu, et al.
During the measurement,The traditional lever type measuring instrument will introduce a nonlinear error due to the rotation of the lever, which will affect the measurement result.A magnetic levitation stylus measuring instrument was designed based on it. It changed the lever supporting mode from the stylus shaft to the vertical direction linear translation which can eliminate the nonlinear error and improve the measurement accuracy.This paper introduces the measuring principle based on the magnetic levitation bearing stylus surface topography sensor, designs the electronic control system of the magnetic levitation contact measuring instrument, and finally conducts the surface topography measurement test.The experimental results show that the designed electronic control system can meet the design requirements of the magnetic levitation system.
Optimization on metering accuracy of smart electricity meter by temperature compensation
Smart electricity meters are playing an indispensable role in modern society, and their measurement accuracy affects the economic interests of both power units and users. In this paper, a compensating method based on neural network approximate modeling is proposed to increase the accuracy of electric energy measurement among the whole range of operational temperature. Based on the measurement data and the internal structure of the smart electricity meter, a MATLAB/Simulink model of the meter is built to evaluate the consistency of power measurement at different temperature levels. The FEM (finite element method) thermal simulation model of the meter device is carried out in ANSYS Icepak to obtain the temperature contours of the smart meter in different operating conditions. Afterwards, based on the simulation data, the component temperature in the metering circuit is evaluated according to the approximation model built by RBF (Radial basis function) neural network. At last, a temperature compensation program is realized in the MCU (Micro-Controller Unit) to adjust the metering accuracy. According to the final testing results, the proposed method significantly enhances the metering accuracy among full temperature range.
Study on temperature characteristics of triangular prisms ring cavity
The refractive indexes of prisms are affected by temperature, hence the optical characteristics of triangular prisms ring cavity is disturbed enough to affect the stability of the laser gyro. Considering the temperature perturbation, the transmission matrices of the reflected and refracted beams on the prism surfaces have been modified. The modified results are the old 2×2 beam transfer matrices are corrected to new 3×3 matrices and the temperature perturbations are added. According to the self-consistent theory of the laser ring cavity, a physical model of the ring cavity light transmission with the temperature disturbance has been established. The theoretical analysis shows that when the temperature varies from -40℃ to 70℃, the changes of the optical cavity-length, frequency offset, and scale factor are 49μm, 0.011MHz and 1.96×10-10, respectively. An experimental system of the prism laser gyroscope has been established whose temperature can be changed, and the experimental results agree with the theoretical values.
Construction of a compact laser wavemeter with compensation of laser beam drift
A compact diffracting grating based laser wavemeter is constructed in this paper. Wavelength is the length unit of laser interferometers, it must be very accurate and stable during the length measurement. An air sensor, which is employed to correct the air refractive index through an empirical equation, is essential in laser interferometers. However, the empirical equation is suffered from indirect measurement, the correction accuracy is depended on the measurement accuracy of the air sensor. Slow response is other disadvantages of the empirical equation. Additional, the empirical equation is not applicable to correct the laser diode wavelength. Therefore, a direct measurement method of laser diode wavelength, based on the diffraction principle, is proposed and a compact, low-cost and simple wavemeter is constructed in this paper. Laser beam drift is recognized as one of critical error source in laser measurement. Therefore, a novel laser beam drift active compensation method is thus proposed in this study that integrates the functions of automatic type angle turning and PID controlled fine angle motion. After introducing the principles of wavelength measurement and laser beam drift compensation, the effectiveness of the wavemeter in real-time wavelength measurement is well verified by the experimental results.
An integrated linear time-grating displacement sensor with single alternating light field
It is difficult to control consistency of light source and large volume in current linear time-grating displacement sensor with four-channel alternating light field. A novel integrated linear time-grating displacement measurement system with single alternating light field is proposed. Single alternating light field and micro-controlling phase-shift method are used to synthesize a signal of traveling wave. And the measurement of linear displacement is achieved by measuring a difference of zero-crossing time between a signal of traveling wave and a reference signal. Design of structural miniaturization, design of integrated circuit, design of transmitting surface of cosine and design of optimization of existing time-grating displacement sensor are analyzed in detail. According to measuring principle, manufacture of light source and photoelectric receiver are completed, and corresponding experimental platform is built. Experimental results indicate that the measuring errors of optimized sensor are reached within±0.2μm using grating pitch of 0.1mm in the measuring range of 100mm.
Laser frequency locking system using orthogonally demodulated Pound–Drever–Hall method
Juan Su, Mingxing Jiao, Fei Jiang, et al.
Based on the principle of orthogonal demodulation, a Pound-Drever-Hall laser frequency locking scheme is developed. In the orthogonal demodulation Pound-Drever-Hall system, three sine signals are generated simultaneously using a direct digital synthesizer. A 0° phase sine signal is used to drive an electro-optic modulator to produce the phase sidebands, and 180° and 270° phase sine signals are used as reference signals for phase demodulation. The phase-modulated laser beam is coupled with a reference Fabry–Pérot cavity, and the reflected beam is sent into a photo-detector, whose output is mixed with two orthogonal reference signals to obtain two orthogonal components of the error signal. Using an analogto- digital converter, the two orthogonal components are processed using orthogonal phase sensitive detection to obtain the error signal on a host computer. The Pound-Drever-Hall laser frequency discrimination and tracking system is established and investigated experimentally using the orthogonal demodulation method. A frequency discrimination curve is obtained, and it is observed that the resonant frequency of the Fabry–Pérot cavity can automatically track laser frequency variation.
Dynamic sensitivity distribution of linear electrostatic sensor matrix
Particle charging is a universal phenomenon due to the collision and contact between particle and particle, particle and wall in the powder pneumatic conveying process. The linear electrostatic sensor matrix (LESM) is able to capture the dynamic information of the moving charged particles in pipeline, whose spatial filtering characteristics has been employed to obtain the flow velocity of particles in gas-solid flow. The spatial filtering characteristics of LESM are closely related to its dynamic sensitivity (DS) distribution. In this paper, the 3D simulated model of the LESM was built by finite element method and the effects of its structural parameters on its dynamic sensitivity and spatial filtering characteristics were studied. The geometric dimensionless model of dynamic sensitivity of LESM was further established. Finally the experiment was carried out on a gravity-fed solids flow rig, and the experimental results was verified the simulation results.
An exchangeable end effector for multi-part-assembly system
Shengsheng Sun, Yi Luo, Xiaoxu Qiao, et al.
Automatic assembly is widely used in precision component fabrication, and the manually assembled task for a small batch of the precise component is replaced by automatic system gradually. One of the key issues is manipulating the workpiece reliably. With the quick updating of the products, the end effectors need to pick more parts with different dimensions and configurations. In this paper, an exchangeable end effector for laser gyroscope assembly is presented. The end effector integrated with adsorption and clamping is designed to suitable for different type of workpieces. The three-position two-way magnetic valve is used to switch the adsorption and clamping. Based on the dimension and shape characteristics of the parts, the adsorption and clamping position of the end-effector was calculated. The maximum weight of the part is 0.5N, thus vacuum degree required for adsorption is 0.078MPa and the reaction time is 0.653s. The clamp for this gas circuit can generate the clamping force of 10N, which meets the requirement of clamping. Finally, the assembly tests were carried out to prove the feasibility of this exchangeable end effort.
Using carbon nanotube membrane as counter electrode in voltammetric electronic tongue system
Yazhuo Li, Xiangdong Zhou
Carbon nanotube membrane (CNTM) has been employed as the counter electrode in a two-electrode voltammetric electronic tongue system. Owing to its large surface area, CNTM provides significant double layer capacitance at the solid/solution interface, and offer a constant potential during the electrochemical detection. In order to characterize the analytical possibilities of the electronic tongue system, hydrogen peroxide has been detected. Principal component analysis (PCA) is used for identification. From the PCA plots, the electronic tongue system by using CNTM counter electrode shows much better performance and more promising than the conventional voltammetric two-electrode electronic tongue system by using large surface stainless steel counter electrode.
Analysis of contacting characteristics on aerostatic bearing stylus displacement sensor
Wu Hao, Suping Chang, Jianfei Zhou, et al.
In this paper, the dynamic and static contact characteristics of the aerostatic bearing stylus displacement sensor are analyzed, including static contact damage and dynamic response. The dynamic response at frequency and different speeds is studied and obtained the relationship between the measured force and frequency and velocity. The stylus does not contact well from the surface when the measuring force is less than 0. In this case, the traceability of the tip can be analyzed based on the characteristics of the amplitude. Finally, the experimental verification of the relevant theory is obtained by measuring the aluminum turning sample at different speeds.
Synthesis and metrology of cellulose nanocrystal films
Cong Cao, Dongsheng Zhao, Ying Tang, et al.
Cellulose nanocrystal (CNC) is an emerging nanomaterial that has drawn increasing attention recently. It is abundant, sustainable, renewable, and biodegradable. They have unique chemical and mechanical characteristics that cannot be met by traditional cellulose-derived materials, such as high aspect ratio, low density, high stiffness, high tensile strength and very low coefficients of thermal expansion. This paper is focused on the formation and characterization of CNC films and the subsequent traceable metrology of CNC film thickness by atomic force microscopy (AFM). The AFM is calibrated by a series of certified reference materials, and thus the measured values can be traceable to the laser wavelength reference (meter definition). Results show that CNC films with negative charges on surface can be formed via physisorption to an amine-terminated thiol layer on gold through spin coating. The CNC film thickness can be controlled by CNC solution concentration. A thorough understanding of CNC metrology is the foundation for further study of CNC chemical and mechanical characteristics and applications.
An interrogation method with high resolution and high response speed for FBGs-based sensors
Recently, fiber Bragg gratings (FBGs) have played significant roles in a variety of fields such as optical communication, dimensional metrology, buildings health monitoring, ultrasonic waves and vibration measurement, petrochemical and other harsh/remote environments owing to their excellent performances like electromagnetic insensitivity, high accuracy and long term stability. In general, FBGs-based sensors are usually decoupled by detecting the variations of FBGs’ central wavelength, wherein, the accuracy and dynamic characteristics of the FBGs-based sensing are directly dependent on the spectral resolutions and response speed of the interrogation method. However, conventional spectral interrogation methods, which directly utilize an optical spectrum analyzer (OSA) with low resolutions and response speeds cannot satisfy the requirements of detecting small and dynamic variations of the FBGs’ central wavelength accurately. It is therefore of significance to find a FBGs interrogation method with high resolution and high response speed. In this paper, a high resolution and response speed interrogation method based on reflective-matched Fiber Bragg Gratings scheme is investigated in detail. The nonlinear problem of the reflective-matched FBGs sensing interrogation scheme is solved by establishing and optimizing the mathematical model. A mechanical adjustment to optimize the interrogation method by tuning the central wavelength of the reference FBG is investigated to improve the stability and antitemperature perturbation performance. To satisfy the measuring requirement of the optical and electric signal processing, an acquisition circuit board is well-designed, and experiments on the performance of the interrogation method are carried out. Experimental results indicate that the optical power resolution of the acquisition circuit border is better than 8 pW, and the stability of the interrogation method with the mechanical adjustment can reach 0.06%. Moreover, the linearity of the interrogation method is 3.3% in the measurable range of 60 pm; the influence of temperature is significantly reduced to 9.5%; the wavelength resolution and response speed can achieve 0.34 pm and 500 kHz, respectively.
Combining compound eyes and human eye: a hybrid bionic imaging method for FOV extension and foveated vision
Based on artificial compound eyes and human vision mechanisms, we propose a hybrid bionic imaging method to achieve field of view (FOV) extension and foveated imaging simultaneously. The imaging model of the proposed method is built, and the key parameters are deduced. Then, simulations are carried out to estimate the properties of the model, including FOV extension ratio (FER), foveal ratio, fovea moving range and so on. Finally, a prototype is developed, and imaging experiments are carried out. The experimental results accord with the simulations well, proving the potential of the proposed method for intelligent surveillance, automatic object detection and recognition with low cost.
Bionic vision improves the performances of super resolution imaging
A novel super resolution reconstruction method is proposed to improve super resolution image performances. The proposed method uses bionic vision sampling model to obtain low resolution images and performs super resolution reconstruction in logarithmic polar coordinates. We carry out comparative experiments between the proposed method and the traditional method in terms of Peak Signal to Noise Ratio (PSNR), Structural Similarity Index Measure (SSIM) and Mean Squared Error (MSE). The results show that the performances of proposed method are better than that of the traditional method. Especially the SSIM of global image (butterfly), the proposed method is 34.45% higher than the traditional method.
Robust concrete crack recognition based on improved image segmentation and machine learning
Qiancheng Zhao, Jiang Shao, Tianlong Yang
This paper presents an automatical crack recognition approach. Compared with the existing methods, it has a significant increase in robustness and efficiency when faced with widely varying field conditions. Inherent characteristics of crack images are exploited using proportional segmentation, combined with robust feature extraction to improve machine learning classifier performance. Experiments show that this method perform well in crack images recognition across different concrete conditions.
Complicated intermittent scratches detection research on surface of optical components based on adaptive sector scanning algorithm cascading mean variance threshold algorithm
Fanyi Wang, Pin Cao, Yongying Yang, et al.
In inertial confinement fusion system, the intermittent scratches on the polished surface of single-sided polished and bottom surface frosted optical components are complex, and it’s of great difficulty to extract them completely. In order to solve this problem, established in the light-field surface detection system, this paper brings forward a novel intermittent scratch detection method based on adaptive sector scanning algorithm (ASC) cascading mean variance threshold algorithm (MVTH). In the preprocessing step, dividing the original image into subimages with a number of integer multiple of cpu cores so as to fully compress image processing time utilizing parallel processing, using mean filter to balance background and then obtaining binary subimages utilizing morphology and threshold operations, finally, utilizing Two-pass algorithm to label the connected domains of binary subimages. In the detection step, considering the complexity of the pattern of intermittent scratches, ASC is first used for routine intermittent scratches stitching and then supplemented by MVTH. In the verification step, in order to prove that the detected intermittent scratches satisfy the criteria for scratches in human eyes, the method of support vector machine (SVM) pattern recognition is utilized to compare the detected results with the continuous scratch samples detected by human eyes. This algorithm has high degree of parallelism, high speed and strong robustness. The experimental results illustrate that the complete extraction rate of intermittent scratches is 93.59% , the average processing time of single image is merely 0.029 second and the accuracy rate of detection is up to 98.72% by SVM verification.
Characterization of beam splitter using Mueller matrix ellipsometry
Song Zhang, Jiamin Liu, Hao Jiang, et al.
Polarization distortion is a phenomenon which the polarization state of output light deviates from the theoretical expectation. Due to the design defects and process limitations, polarization distortion in beam splitter is inevitable, which results in the significant errors in the optical systems. A theoretical analysis method based on Mueller matrix is proposed for characterizing the beam splitter. In the propose approach, polarization distortion in the beam splitter including depolarization, linear and circular birefringence, and linear diattenuation, circular dichroism have been considered. With the proposed method, we can characterize the beam splitters and extract the related effective optical parameters of polarization distortion. The Mueller matrices of two different commonly used beam splitters measured by a commercial Mueller matrix ellipsometer (MME) are consistently fitted by the proposed method and the residual errors have shown the improvement compared to the conventional methods.
A chi-square statistics of arithmetic mean and applications to inter-laboratory comparison
Chenzhe Hang, Guoyuan Ma, Jianli Liu, et al.
Under the condition that comparison results are Gaussian distributed with a common mean, a chi-square statistics of arithmetic mean is proposed and investigated through the Monte Carlo simulation. Simulation results show that the arithmetic mean has its own (n – 1)th-order chi-square statistics under the condition that the uncertainties of participants are comparable. Furthermore, the density curve of the proposed statistics is confined between the (n - 1)th-order and first-order chi-square under the condition that the uncertainties of participants are incomparable. However, the expected value of this statistics equals n – 1, which is unaffected by the uncertainties. Based on these properties, the proposed statistics is applied to the consistence testing of arithmetic mean by examples.
Extracting road edges from MLS point clouds via a local planar fitting algorithm
As the basic element of a road, road edges are of great significance for intelligent transportation and urban foundational geographic information construction. Mobile laser scanning (MLS) provides an effective way to extract road information, but it is difficult to extract accurate road edges from a large-scale dataset with complex road conditions. In this paper, we propose a method to extract road edges from MLS data based on a local planar fitting algorithm. First, scanning lines are extracted based on the horizontal projection distance between the laser points. Second, a planar fitting method is adopted to extract road curb points. Road curb points are then clustered and optimized by differentiating the distance between road curb points and the auxiliary line. Finally, a linear least squares fitting method is applied to obtain the road edges. Three experimental datasets with multi-type road markings were used to evaluate the performance of the proposed method. The results demonstrate the feasibility and effectiveness of the proposed method.
A novel signal process system for angular displacement sensor of time-grating
Wei Wang, Zhaoyao Shi, Donglin Peng
The angular displacement sensor based on time-grating is a novel kind of displacement sensor, but there is a limitation in some applications with harsh environment owing to extracting angular information uses the analog phase detector. To reduce the error comes from solution and improve the static stability of sensor, a novel signal process system is presented. In comparison to the traditional method using analog electrical technology to obtain angular displacement, the proposed method uses the All phase Fast Fourier transform (AP-FFT), that has a perfect performance on suppressing the spectrum leakage and the property of phase invariant, to obtain the phase angle. In the paper, we design the core system for data sampling and processing. Firstly, it utilizes AP-FFT to transform the sensing signal from time domain to frequency domain; in addition, the angle is calculated in the phase spectrum. Finally, the experimental platform is designed to verify the performance of the proposed technique. The error of the novel method is compared to that of the traditional method, it can be concluded that the proposed method is very effective in suppressing noise and enhances the stability in a static condition.
Characterization of a liquid crystal variable retarder by Mueller matrix ellipsometry
With the maturing of liquid crystal technology, liquid crystal variable retarder (LCVR) has been widely used in optical systems. In practice, it is of great importance to characterize the polarization properties of the LCVR for its control and applications to accurately modulate the polarization state of the light in the optical systems. In this paper, the Mueller matrix ellipsometry (MME) is applied to comprehensively characterize the polarization properties including the retardance and the fast axis azimuth of the LCVR versus the driving voltage, the wavelength, as well as the incidence and the azimuth of the light. An analytical model is constructed to describe the LCVR based on the Mueller matrix calculus, in which the influences of the incidence and the azimuth of the light are considered. A house-developed spectroscopic Mueller matrix ellipsometer is employed to perform the experiments. Simulations and experiments about a commercial LCVR product are presented and discussed to verify the proposed method.
Defect detection method for complex surface based on human visual characteristics and feature extracting
Yubin Du, Pin Cao, Yongying Yang, et al.
Aimed at the problem of strong background interference introduced in digital image processing from complex surfaces under industrial defect detection, a method for complex surface defect detection based on human visual characteristics and feature extracting is proposed. Inspired by the visual attention mechanism, defect areas can be identified from the background noise conveniently by human eyes. We introduce the improved grayscale adjustment and frequency-tuned saliency algorithm combined with the salient region mask obtained by dilation and differential operation to eliminate the background noise and extract defect areas. Meanwhile the directional feature matching and merging algorithm is applied to enhance directional features and retain details of defects. Testing images are captured by our established detecting system. Experimental results show that our method can retain defect information completely and achieve considerable extracting efficiency and detecting accuracy.
Micro Coordinate Measurement Machine (uCMM) using voice coil actuator with interferometric position feedback
Quantitative determination of dimensional properties like length, diameter, height, etc. is essential in research, development and in production process control. To meet these requirements, the widely used approach is the coordinate measurement technique. The equipments - the coordinate measuring machines (CMMs) – using the mentioned technique cover a wide measurement range from meter to nanometer. Below a newly developed equipment for the micro scale is presented. The system – the micro coordinate measuring machines (μCMM) - consists of a probing system, voice coil based actuators and an integrated interferometric measurement system. The key component - in addition to the probing system – is the positioning stage, since the characteristics of the position acquisition and control directly influences the achievable accuracy of the complete measurement system. In contrast to a standard interferometer the presented system utilizes a 2D CMOS image sensor to capture the measurement signal. To drive the stage, a commercial voice coil actuator is used: the scanning range of the introduced system covers about 15 mm, and can be easily extended. The applied probing system uses a ruby ball stylus probe. It is a measuring probe, which means that it provides a signal corresponding to the occurring deflections of the probe ball for all three spatial directions. The probe achieves nanometer resolution.
A measurement method for probe microsphere of micro-CMM with double SPMs
Chuan-Zhi Fang, Qiang-Xian Huang, Meng Mi, et al.
Probe tip of the Micro-coordinate Measuring Machine (Micro-CMM) is a microsphere with diameter of several hundred microns, and its sphericity is generally controlled at tens to hundreds of nanometers. Due to the small size and high precision requirement, the measurement of the microsphere morphology is difficult. In this paper, a measurement method for probe microsphere of Micro-CMM is proposed based on two SPM (Scanning Probe Microscope) probes, and a ruby microsphere of a Renishaw commercial CMM stylus is measured by the proposed method. In the experiment, the repeatability error of a maximum section profile is test, and the repeatability error is 41 nm (peak-to-peak value). Two perpendicular maximum section profiles are measured, and the corresponding diameter and roundness are estimated by the least squares method.
Aerosol particle size distribution retrieval algorithm and error analysis based on multi-wavelength radar
In order to alleviate the ill-posed problem of the ill-conditioned equation, the regularization algorithm combined with averaging method is used to retrieve the aerosol particle size distribution. In this method, the selection of the optimal average interval is crucial. According to the spectral of LED, fourteen wavelengths for the LEDs are selected, and different optical parameter combinations are set. By the retrieval of multiple sets of original volume concentration distribution and error statistics, the optimal average interval of each optical parameter combination is obtained. The retrieval simulations of logarithmic-normal volume concentration distribution were completed. The simulation results show that when using a combination of ten backscatter and ten extinction coefficients, the reconstructed monomodal distribution has the best fitting effect, and the relative error of effective radius and volume are the smallest. And when using a combination of six backscatter and six extinction coefficients, the reconstructed bimodal distribution has the best fitting effect, and the relative error of effective radius and volume are the smallest.
Investigation on the dynamic characteristics of CG-6 relative gravimeter for the micro-gravity network
CG-6 is a new generation of full-automatic relative gravimeter produced by Scintrex Company, Canada. It can be used to measure the vertical gravity gradient. This paper mainly addresses dynamic precision of CG-6 relative gravimeters in the vertical gravity gradient measurements during the Comparison of Absolute Gravimeters. This paper analyzes the repeatability and consistency of 4 CG-6 gravimeters in dynamic test. We process the static and dynamic experimental data of 4 CG-6 gravimeters. Results show that the dynamic precision of CG-6 gravimeters in vertical gravity gradient measurements is better than 3μGal1. The static drift rates are all less than 3μGal ∙ h-1. One of the CG-6 gravimeters has been used to monitor the NIM (National Institute of Metrology, China) local gravity network, especially in measuring the vertical gravity gradients. This allows for an evaluation of the overall dynamic performance of CG-6 gravimeters and their stability concerning highly precise determination of vertical gravity gradients for the micro-gravity network.
Optical fiber Fabry-Perot acoustic sensor based on large PDMS diaphragm
Han Zhou, Bingkun Wu, Mingguang Shan, et al.
An extrinsic Fabry-Perot interferometric fibre microphone based on polydimethylsiloxane, or PDMS, diaphragm was proposed. The large free-standing PDMS diaphragm, with a diameter of 4 mm, is prepared by a simple “spin-strip” process. The experimental result shows that the fabricated sensor has a high dynamic pressure sensitivity of about -136 dB re 1 rad/μPa in the range of 100~2000Hz. The noise equivalent acoustic signal level of the microphone, limited by the environmental noise, is about 1000 μPa/Hz1/2. And the dynamic range is tested to be more than 47.48 dB. The proposed microphone is expected to be used in the field of weak acoustic pressure testing.
A research on bolt loosening monitoring based on Lamb wave
Qi Chang, Heming Gao, Weixi Yang, et al.
For the mechanical industry, bolts are an important guarantee for the safety of connection between parts. The traditional method for monitoring bolt loosening is mainly through human judgment, but this method has a large error and cannot be monitored online. At present, the dynamic change process of the bolt loosening can be learned in more detail through the Lamb wave monitoring technology. In this paper, the piezoelectric transducer(PZT) is used to generate the Lamb wave in aluminum structure to monitor the looseness of the bolt on it. The signal with bolt looseness information received by another PZT is analyzed and processed. The S0 modal of the signal is chosen to extract the amplitude of it. After analysis it can be seen that the amplitude of the S0 modal reduces as the bolt gone loose. The relationship between the amplitude and bolt looseness have been drowned. And the functional relationship is presented.
Development of in-situ measuring geometrical characteristics method for crankshaft
Dongliang Liu, Peng Zheng, Zhanxin Zhi
Aiming at the requirement of high-precision and high-efficiency measurement of crankshaft grinding machining, a new method for measuring the geometrical characteristics of crankshaft in-situ is proposed and a crankshaft grinding in-situ measurement system is constructed by this method.In the first place, the overall plan for in-situ measurement system is formulated to confirm the composition of the in-situ measurement system.In the second place, the new type of measurement device is designed and constructed to convert the change in size into the change in inductance to analyze the geometric characteristics of the workpiece during machining.Geometric error operation operator based on the new generation Geometrical Product Specification (GPS) is constructed.And mathematical models for on-site machining measurement such as shaft diameter and roundness are established.The final step is to design the measurement and active measurement controller then develop its corresponding software. The real-time geometric feature information of the crankshaft machining acquired by the measuring device is obtained, analyzed and applied to the control and adjustment of the workpiece geometry in the grinding process.Through experiments, it can be proved that the in-situ measurement device can greatly improve the production efficiency and precision of crankshaft grinding.
A novel miniaturized capacitive absolute angular position sensor based on time-grating with reflective structure
Hewen Wang, Kai Peng, Xiaokang Liu, et al.
With the development of portable intelligent instrumentations, the demand for high-precision, absolute-positioning, low-cost and compact-size angular position sensors has substantially increased. In this paper, a novel miniaturized capacitive angular position sensor based on time-grating, which adopts a reflective structure to realize absolute position measurement and simultaneously achieve high-precision, is proposed. The sensor is comprised of a stator and a rotor both covered with three rings of metal electrodes. The middle ring of the sensor adopts a single-row structure to obtain a high-precision initial travelling signal and reflect it to the stator through the outer ring. The inner loop obtains the final travelling signal through the second modulation signal. The phase difference between the final travelling wave signals and initial travelling wave signals varies periodically with a period of 360° when the rotor rotates; thus, this phase difference can be used to realize the coarse absolute position measurement. Phase detection is realized using the time pulses interpolation technology of time-grating, and the angular displacement is measured with time. High-precision absolute angular positioning is achieved through a compact structure. A prototype sensor with an outer diameter of 60 mm and an inner diameter of 24 mm is fabricated by printed circuit board technique to evaluate the performance. Experimental results show that the proposed sensor achieves a ±3″ measurement accuracy over an entire circumference. Moreover, the rotor is wireless owing to the reflective structure, which has a wider range of applications in engineering.
The analysis of key comparison reference value and its uncertainty using Markov chain Monte Carlo method
Haiyun Zhang, Dinghua Xu, Jianli Liu, et al.
The analysis of Key Comparison data is to determine the Key Comparison Reference Value (KCRV) and its uncertainty. In the current model, the weighted mean is used as KCRV which is put forward by M, G, Cox. However, the method qualifies the measurement results as Gaussian distribution and does not apply to T distribution or other, which causes the risks of chi-square test failure. When the data analysis is invalid based on conventional statistics, the Bayesian approach may be a valid and welcome alternative. Bayesian inference is often required to solve high-dimensional integrations which Markov chain Monte Carlo (MCMC) is such a method. Here is a simple example used to illustrate the application of this method in metrology. The Metropolis-Hastings algorithm is the most flexible and efficient algorithm in MCMC method. In this paper, its basic concepts are explained and the algorithm steps are given. Besides, we obtain the KCRV and its uncertainty using the Metropolis-Hastings algorithm through MATLAB. Then, the convergence of MCMC is diagnosed. In principle, the MCMC method works for any starting value and any proposal distribution. In practice, however, both choices affect performance. We illustrate this influence with the example.
Deformation measurement of testing machine based on laser interference method
Bin Mao, Jianjun Cui, Kai Chen, et al.
Tensile, compressive and universal testing machine (Hereinafter referred to as testing machine) is an important instrument for analyzing the pressure of materials. In order to reasonably assess the influence of the deformation of the beam and fixture on the strength analysis of the tested material, the deformation of the beam and fixture of the tested machine, which under the stress state, should be studied. Firstly, the laser interference method is proposed to measure the mechanical deformation characteristics of the beam and fixture. Secondly, we should analyze the structure and theory of measurement technology, give the test method and then calculate the relationship between the deformation of crossbeam and fixture and the stress. Finally, the experimental data are summarized, and the numerical correction method of material shape variables is obtained when testing materials are measured. The experimental results show that the shape variables between the beam and fixture of the testing machine reaches to 0.57mm when the force value reaches to 5 kN. By using this measurement method, the shape variables of the beam and fixture of the testing machine can be measured accurately, and the material deformation can be corrected relevantly during test and analysis of the material strength, which can improve the measurement accuracy of the material deformation for the testing machine.
Corrected differential fitting for height extraction in chromatic confocal microscopy
As for chromatic confocal sensor system with limited computational capacity, a fast peak extraction algorithm with considerate accuracy is in urgent demand. However, current peak extraction algorithms such as the centroid algorithm (CA) and nonlinear fitting algorithms can not balance the accuracy and computational efficiency. Thus, we propose an accurate peak extraction algorithm with good computational efficiency called corrected differential fitting algorithm (CDFA). At first, the differential signal derived from the original axial response signal is linearly fitted for initial peak extraction. Then corresponding systematic error of this linear fitting operation is analyzed using a first-order linear nonhomogeneous differential equation. At last, error compensation, that is, the solution to this equation is implemented with an introduction of "sum differences of sampling intensity". The performance of CDFA is compared with two conventional peak extraction algorithms including the CA and Gaussian fitting algorithm (GFA) using Monte Carlo simulations. CDFA is found to have a comparable accuracy performance with GFA while have a much higher computational efficiency.
Evaluation of task specific measurement uncertainty for gear measuring instrument using VGMI
This paper aims to evaluate the task specific measurement uncertainty for gear measuring instrument (GMI) using virtual gear measuring instrument (VGMI). With the aid of Modular Simulation and Monte Carlo method, the uncertainty evaluation model is established on VGMI. The measurement uncertainty of the tooth profile deviation is evaluated by VGMI taking the tooth profile deviation of the involute cylindrical gear as the measured parameter. The uncertainty sources are considered in the simulation including the geometric error, the head error and the workpiece installation error. To verify the measurement uncertainty model of VGMI, we designed three involute tooth surface models with different reference precision, and their profile deviation measurement uncertainties are simulated by VGMI. The results show that VGMI is feasible, effective and correct for the measurement uncertainty evaluation. VGMI provides a new tool for evaluating the task specific measurement uncertainty for the gear measurement instrument. It can realize the seamless connection with the real measurement software. The ability to change measured workpiece model without reestablishing the VGMI model is also a significant advantage.
Dual-comb generation from a dual-ring hybrid mode-locked fiber laser
Ruitao Yang, Hao Sun, Jiahao Guo, et al.
Dual-comb generation with bidirectional fiber ring laser is highly prospective for its compactness and coherency. In this paper, we propose a dual-ring hybrid mode-locked fiber laser for dual-comb generation. The dual-ring laser contains elements of hybrid mode-locking for each sub-ring individually, while sharing the bidirectionally pumped erbium-doped fiber (EDF). The hybrid mode-locking is realized by transmission semiconductor saturable absorber (SESA) and nonlinear polarization evolution (NPE). With the help of two three-port optical circulators, non-ideal reflection of two SESAs are eliminated. Accordingly, two series of short pules are generated in each sub-ring with different direction individually. Experimental observations and analyses demonstrate that dual comb of about 300 kHz difference in repetition rates are generated by inserting a 10 cm cavity length difference between the two sub-rings. With the help of hybrid mode-locking and large power bidirectional pumping, the mode-locking of dual combs are stable and self-starting.
Critical point determination method of thermal-force coupling deformation of CNC machine tool bed
Hongtao Yang, Li Li, Shidai Zhang, et al.
In order to reduce the additional influence of the thermal-force coupling deformation of the Computerized Numerical Control(CNC)machine tools bed based on the grating measurement, the concept of the thermal-force coupling deformation critical point in the direction of the grating installation line of the machine bed is proposed. In order to accurately determine the thermal-force coupling deformation critical point of the machine bed, the BV75 CNC machine tool is taken as an example. The factors that cause the deformation of CNC machine bed are analyzed by using material theory, thermos-elastic and nonlinear thermal deformation theory. According to the actual structure size of the machine tool ,a 3D model is established. The heat sources and load conditions of the machine bed deformation are theoretically analyzed, and the finite element thermal- force coupling analysis of worktable is carried out. The deformation critical point in the direction of grating installation line of machine tool bed is determined by theoretical modeling and finite element analysis. Under loading single heat source, the multi heat sources and the different size and position load, the comparison experiments of the thermal deformation of the machine bed and the zero shift errors of the grating measurement are carried out. The experimental results show that the bed thermal deformation is the main source of the grating additional error, and the workpiece loading position will cause the bed deformation. The position of thermal-force coupling deformation critical point is different from the thermal deformation critical point. The zero position and the indication error of the grating can be reduced by fixing the grating on the thermal-force coupling deformation. An accurate grating error prediction compensation model can be established, which is use for the subsequent error compensation of the on-machine measurement system of the CNC machine tools.
Soil moisture sensor design based on fiber Bragg grating
Kejun Yan, Jun Liu, Na Sun, et al.
In order to achieve a large area of deep soil moisture monitoring, a soil moisture sensor based on fiber Bragg grating was designed. The polyimide with high water sensitivity and high linear expansion coefficient was coated to the surface of FBG. The center wavelength of the FBG will change due to moisture absorption and expansion of the polyimide material when moisture changes. Using this basis principle, the soil moisture can be measured. A stainless steel tube with a hole is used as a sensor package and wrapped in polyurethane nets to maintain consistent with the external temperature and moisture environment and prevent soil from entering the sensor. A fiber Bragg grating without a PI coating layer was packaged in the same package structure with the soil moisture sensor as a reference fiber for temperature compensation. An experimental system was set up, calibration experiments were performed on the sensors, and various performances of the sensors were tested. The experimental results show that the measuring range of moisture is 15%RH~75%RH, the sensitivity is 12.6pm/%RH, and the accuracy of the sensor is ±10.26%.
Kinematics identification and measurement accuracy verification of articulated arm coordinate measuring machines
Sen Wang, Guanbin Gao, Jun Zhao, et al.
The Articulated Arm Coordinate Measuring Machine (AACMM) is a kind of coordinate measuring devices in the form of an articulated robot. To improve the accuracy of AACMM, a kinematic identification method is presented in this paper. Firstly, we perform the kinematics modeling and simulation to realize the kinematic transformation from the joint space to the coordinate space. Then, we establish an error model and use least squares method to identify kinematic parameters. And the effectiveness of the least squares method for kinematic parameter identification is studied. Finally, the experiments of single point repeatability accuracy and the standard gauge accuracy are performed. The experimental results show that proposed the kinematic identification method can effectively improve the measurement accuracy of the joint coordinate measuring machine.
Self-calibration method of precision shafting angle measurement error based on multiple reading heads
Run Zhang, Wenhui Bao, Huining Zhao, et al.
With the continuous improvement of equipment measurement accuracy and production efficiency requirements, calibration method with external reference standard can no longer meet the quality and efficiency requirements. In order to solve the online calibration problem and effectively improve the calibration efficiency of the Articulated Arm Coordinate Measuring Machines (AACMMs) in practical application, a self-calibration system of circular grating angle sensor which is applied to joints of the AACMMs was established. Based on the harmonic analysis of the angle measurement error, this paper deduces and analyzes the error suppression principle of the layout of the scanning heads on the calibration result, and establishes a non-uniform layout of the scanning heads to eliminate more and higher order harmonic errors. The simulation and test results show that the self-calibration method using this layout form of multiple reading heads can effectively reduce the measurement angle error without increasing the number of scanning heads, and improve the calibration efficiency and measurement accuracy of AACMMs.
Theoretical analysis and digital simulation of a new capacitive sensor
In order to research a new detection principle of capacitive sensor, a new capacitive sensor based on the edge effects of non-parallel polar plates is proposed in this paper. The capacitance field of the sensor includes two parts, the electric field between the polar plates and the edge electric field. When a special medium is in the edge electric field, it will change the distribution of the electric field line of the edge electric field and cause the change of the capacitance value of the sensor, and then the non-contact detection of the detected object can be realized. This paper studies the relationship between the range of the edge electric field and the basic parameters of the sensor. The model and formula of the sensor are analyzed theoretically in this paper, and these typical projects were simulated by ANSYS. The results show that the detection principle of the new capacitive sensor is reasonable and correct.
Error mapping for rotary axes of machine tools based on pose measurement principle
Haitao Li, Jiangong Sun, Xianming Gao, et al.
Laser tracker has been introduced successfully for geometric deviations calibration of multi-axis machine tools. In this paper, a new method called “pose measurement principle” is developed for measuring geometrical error of rotary axes by means of a single laser tracker and NC precise table. The reflector is mounted on the NC precise table with eccentricity, and the NC precise table is mounted on rotary table. A single laser tracker located at different base stations in order is used for coordinate determination of three fixed points of the reflector to get the pose information of rotary axes, then calculate the pose deviations and identify all the errors. For the error identification, first of all, with the extension of the definition of geometric errors, the 6 geometric errors is represented by pose deviation. Second, 3 angular errors are identified geometrically first, then eliminate the angular errors of all measuring coordinates to obtain the 3 straightness errors. Finally, the 6 errors mathematical model for rotary table is developed. The validity of the proposed method has been confirmed by simulations and experiments. From both of them, it has been confirmed that the proposed method gives precise results and is able to apply to the measurement of rotary axes effectively.
Method of squareness measurement based on laser alignment measuring system
In order to measure the squareness of large-size workpieces, a method of squareness measurement based on laser alignment system was introduced. The structure and principle of the laser alignment system were presented. The squareness measuring method of the squareness measuring system and the laser alignment system were described respectively. This paper improved the method of squareness measurement based on laser alignment system and made the accuracy satisfied with the requirement of most in-site measurement. The experiments show that the squareness measurement accuracy of the laser alignment system can be improved to 5 μm/500 mm.
Super-resolution scanning microscopy with virtually structured illumination
Su Zhang, Jingtao Li, Limin Zou, et al.
The resolution of optical microscopy fundamentally limited by diffraction is at best 200 nm. Super-resolution structured illumination microscopy (SR-SIM) provides an elegant way of overcoming the diffraction limit in conventional widefield microscope by superimposing a grid pattern generated through interference of diffraction orders on the specimen while capturing images. The use of non-uniform illumination field “shift” high specimen frequencies which are out-ofband into the pass-band of the microscope through spatial frequency mixing with the illumination field. Therefore the effective bandwidth of SR-SIM is approximately twice as conventional microscopy, corresponding to a 2-fold resolution enhancement, if the difference between excitation and emission wavelength is ignored. However, such a wide-field scheme typically can only image optically thin samples and is incompatible with multiphoton processes. In this paper, we propose a Super-resolution scanning scheme with virtually structured illumination, utilizes detection sensitivity modulation on line by programming or off line by numerical processing together with temporally cumulative imaging, the excitation intensity is constant while capturing images. In this case a nondescanned array detector such as CCD camera is needed. When combined with multiphoton excitation, this scheme can image thick samples with threedimensional optical sectioning and much improved resolution.
Angle measurement for cross-line target image based on fourier-polar transform algorithm
In visual detection fields based on line-structured light, the analysis of optical stripe image is a key problem. For the cross-line target image, through measuring the angle between two linear optical stripes the target position or some system’s parameters can be obtained. The traditional technique usually needs many preprocessing steps including image filtering, threshold segmentation, thinning processing and so on. For the images with low signal noise ratio or non-uniform intensity distribution, their application performance will be challenged. Based on the characteristic of translation invariance and rotation synchronization of two-dimensional Fourier transform, the paper combines Fourier transform with polar transform to form new Fourier-polar transform algorithm. It implements the angle measurement in the frequency-domain replaced in the spatial domain. At the same time, to improve the convenient of compute, the polar transform is adopted to calculate the distribution direction of amplitude spectrum energy. The proposed Fourier-polar transform algorithm uses the overall information of the image, and the calculating process is simple and no requirement of image preprocessing. Therefore, it can be applied to measure the angle of cross-line target image in low quality image such as low signal-to-noise ratio or with noise.
Microfluidic contact lenses for continuous non-invasive intraocular pressure monitoring
Hongbin An, Liangzhou Chen, Xiaojun Liu, et al.
This paper proposes the microfluidic contact lenses for continuous non-invasive intraocular pressure (IOP) monitoring. The microfluidic contact lenses are the reference-sensing structure, fabricated by using the chemical assisted bonding and next thermoforming technologies. The curvature of contact lenses are made corresponds substantially to that of cornea, so as that, the PDMS (Polydimethylsiloxane) sensing layer can wear on cornea to “feeling” its expansion. The cornea’s deformation is varied in pace with IOP, while the IOP can be simply monitored by using the smart phone to optically detect the movement of visible liquid in the microchannels. The simulated and measured results of the devices with different parameters are presented, showing a good linearity. Also, we have found that the devices with outer distributed chamber or with the smaller microchannel were more sensitive. In next work, the devices will be redesigned to meet the needs of intraocular pressure monitoring and test in vivo.
Eye positioning based on windowed gray-scale integral projection algorithm
Jianmin Zhou, Faling Wang, Chenchen Zhang, et al.
Eye positioning is an important prerequisite for vehicle-mounted fatigue driving monitoring. In this paper, a windowed gray-scale integral projection algorithm based eye-positioning method is introduced. Firstly, the human eye is positioned by Adaboost algorithm, then the eyebrows are separated by the windowed gray-scale integral projection algorithm, consequently, the accurate positioning of human eye parts is achieved. The experimental results show that the separation effect is obvious and the speed of human eye positioning is significantly improved.
A novel Earth’s gravity method for accelerometer calibration
Advanced low frequency vibration calibration is imperative required as the wide applications of low frequency accelerometers. Low frequency calibration is commonly realized by the Earth’s gravity method or the laser interferometry. However, affected by the limited stroke of the standard vibration shaker, the calibration precision of laser interferometry at very low frequency is usually not ideal. Although the Earth’s gravity method can avoid this low calibration precision at very low frequency, its calibration frequency usually <5 Hz due to the influence of rotator centripetal acceleration. In this paper, the Earth’s gravity method mentioned in ISO 16063-16 is improved by using an effective image feature detection method. This method detects the angel between Earth’s gravity field direction and acceleration sensitivity axis direction to improve the Earth’s gravity static calibration accuracy.
Self-calibrating phase shifting shadow moiré technique
Hubing Du, Jianhong Yu, Shaofeng Zhang
The phase shifting shadow moiré is an efficient technique for 3-D shape measurement. Our recent research focuses on improving its measurement accuracy without addition the complication of the experimental set-up. Considering that the existing measurement process of shifting shadow moiré technique is complex, we had been looking for ways to make it easier. In this paper we propose some effective techniques to fulfil the aim. In the proposed method, the binocular stereovision technique is used to calibrate the geometric parameters of our setup. Then a method is developed to determine the grating translation difference. After that an iterative self-tuning algorithm is use to retrieve the accurate phase. The proposed method is fast and can be implemented easily in many applications. Optical experiments are implemented to verify the feasibility of this method.
Research on key technologies of quadrupole electromagnetic tweezer
He Ni, Jingtao Li, Limin Zou, et al.
In this paper, the quadrupole electromagnetic tweezer installed in a fluorescent microscope was developed for the purpose of achieving precise control of magnetic microspheres’ motion trajectory. The key technologies of magnetic microsphere control and positioning by such quadrupole magnetic tweezers were systematically studied. An electromagnetic quadrupole magnetic tweezer system was designed and constructed, a current-magnetic force model of the quadrupole magnetic tweezer was established, and the magnetic force-current inverse force model was derived and simplified. A fluorescence microscopy imaging system was set up and the related program design was completed. The position of magnetic fluorescent microspheres was monitored by a high-speed CCD with sampling frequency of 200 Hz. A proportional-integral closedloop feedback controller was built up for magnetic microspheres. The experimental results demonstrated that the magnetic force range available at the center of the work area was [-80pN, 80pN]. Besides, magnetic microspheres were tested to possess a displacement resolution up to 400 nm as well as the capacity of moving in any direction in a two-dimensional plane. Based on the obtained results, it is expected that the quadrupole electromagnetic tweezer can function one of the effective devices for evaluation of cell mechanical properties.
Error analysis method of weighing cycles based on robotic mass measurement system
Dong Lei, Qianyu Xu, Gang Zheng, et al.
Robotic mass measurement system, which used automatic measurement and data processing, has become the trend of the high accuracy mass measurements. In international comparison and mass-related scientific research, automatic measurement system together with ABABAB weighing cycles can reduce or eliminate the linear drift greatly and improve the accuracy of measurement results further. In this paper, three linear drift error elimination methods of ABABAB weighing cycle model were analyzed, and the corresponding mathematical expressions of error calculation were given, then experimental data was analyzed and compared. All of these three methods based on ABABAB weighing cycle can be applied for automatic measurement in the future.
A high precision edge detection method for the blurred image in motion measurement
The motion measurement based on machine vision has been more and more widely used in robots, object tracking and other fields. However, the relative motion between camera and object often causes images blurred, which decreases the reliability of detection. To improve the detection accuracy of the motion-blurred images edges, a comprehensive method is proposed. By analyzing the grayscale distribution of the object images in different motion directions, we used different methods to enhance the low frequency sub-band images which were obtained by wavelet transform. The subpixel edge detection method based on cubic spline interpolation was applied to detect the edges of the blurred and enhanced images, respectively. Experimental results show that the proposed method avoids the misdetection of the blurred images edges, and obtains higher edge detection accuracy.
A filter algorithm based on ARMA model to suppress the influence of atmospheric disturbance in laser straightness measurement
Atmospheric disturbance influence the measurement accuracy greatly in laser precision measurement of long distance. A real-time filtering algorithm based on time series analysis theory is proposed in this paper. Firstly, ARMA (Auto-Regressive and Moving Average) model of sample data is set up based on the theory of time series analysis, then the mathematical expectation is obtained according to the model as the filtering result, finally, it is integrated into the laboratory laser beam drift measurement system for real-time filtering measurement. It is evident from the simulation results that high accuracy can be obtained after filtering. The experimental results show that the stability of the filtered drift increases by about 20%.
Torque standard machine for calibration of reference torque wrench and torque transducer at Nim
Feng Meng, Zhi Min Zhang, Dian long Zhang
The paper describes a new torque standard machine at NIM. The new reference torque standard machine is designed to calibrate the reference torque wrench and torque transducer. The relative expanded uncertainty of this torque standard from 10Nm to 5000Nm is better than 5×10-4k=2). The calibration experiment of three kinds of reference torque wrenches by the new reference torque standard machine is described in the paper.
Strain transfer characteristics of resistance strain-type transducer
Zhigang Wang, Chi Xiao, Yinming Zhao, et al.
The strain transfer characteristics of resistance strain-type transducer were theoretically investigated. A resistance straintype transducer was modeled to be a four-layer and two-glue (FLTG) structure model, which comprises successively an elastomer, a ground adhesive, a substrate layer, an upper adhesive, a sensitive grids layer, and a polymer cover. The strain transfer progress in a resistance strain-type transducer was described by the FLTG structure model. The strain transitional zone (STZ) was defined and the strain transfer ratio (STR) of the FLTG structure was formulated. The dependence of the STR and STZ on both the structural sizes and material parameters were calculated. The results indicate that the ground adhesive (including its thickness, and shear modulus) have a greater influence on the strain transitional zone ratio and strain transitional zone. In order to ensure a higher sensitivity of the resistance strain-type transducer, the ground adhesive layer should be as thin as possible, while its shear modulus should be as large as possible. Selecting a ground adhesive with a large elasticity modulus can effectively reduce the influence of the thickness of the ground adhesive on the strain transfer ratio.
Design of flexure hinges in an H-drive precision stage with a large span
In order to balance the high translation stiffness and low twist stiffness in an H-drive precision stage with a large span, a design method based on flexure hinges combination is proposed. Firstly, various stiffness requirements in different degrees of freedom (DOF) of an H-drive precision stage with a large span are analyzed. Secondly, half-cartwheel flexure hinges combination is applied to balance these stiffness requirements. Thirdly, based on the Timoshenko beam theory, stiffness matrices of a single flexure hinge and combined hinges are established. Then, various structural parameters of the flexure hinge are determined by analyzing their influence on two performance indicators, including stiffness and motion precision. After that, finite element method is applied to verify these theoretical results. Finally, a stiffness identification experiment and a modal analysis experiment are conducted to test the 2-DOF stiffness of a single half-cartwheel flexure hinge and the natural frequency of the H-drive precision stage. The maximum error of stiffness between theoretical, simulation and experimental results is 13.4%. The natural frequency is up to 176.563 Hz, which could satisfy the control bandwidth requirement of the H-drive precision stage.
Investigation on gPhone gravimeter-119 for gravity variations observation during the 10th International Comparison of Absolute Gravimeters (ICAG-2017)
Qiyu Wang, Lishuang Mou, Jinyang Feng, et al.
The 10th International Comparison of Absolute Gravimeters (ICAG-2017) was held in Changping campus of National Institute of Metrology (NIM), China in October 2017. The observation of gravity variations using relative gravimeters plays an important role in absolute gravimeter comparison and the link of gravity reference value after comparison. We carried out a continuous observation of gPhone gravimeter-119 simultaneously alongside a superconductive gravimeter iGrav-012 for several months. The calibration factor of gPhone-119 is determined to be 0.99355±0.00004 with a precision of 0.004%. When the observation time exceeds 33000 minutes, the calibration values and uncertainties tend to be stable and the precision is better than 0.01%. The non-tidal gravity changes during ICAG-2017 recorded by gPhone-119 are analyzed. The tendency of gravity variations is roughly consistent with that recorded by iGrav-012. The result indicates that the peak-to-peak value of gravity changes is less than 1.5 μGal during the period of ICAG-2017.
Multi-structure elements morpholoy for improved anti-noise edge detection
High precision occupies an extremely important position in the field of mechanical processing and laser measurement. Under these high precision requirements, image processing is widely applied and is especially demanding. As the essential pre-processing step in the process of image processing, the quality of image edge extraction directly affects the processing precision of the whole image, and then affects the final measurement or machining precision. The traditional edge detection method has the defects of no noise immunity, and cannot achieve high-activity processing of sophisticated image edge problems. Through the in-depth research and analysis of various knowledges concerning edge extraction, a novel anti-noise edge detector based on multi-structure elements morphology of different directions for binary, gray scale and color images is proposed in this paper. We get the final edge information by using eight morphological operations respectively and synthetic weighted method. It can remove the noise effectively while detecting complete edge information. Experimental results show that, comparing with conventional edge detection operations, the proposed method attains the outcome of eliminating the image noise and maintaining good edge effectively for simulated image.
Analysis of the extraction accuracy of the corner point of the camera using polarization imaging
Zhenmin Zhu, Xinyun Wang, Quanxin Liu, et al.
In view of the traditional method of corner extraction, the main idea is to improve the corner extraction algorithm and ignore the imaging process of the calibration image, in this paper, an optimal polarization angle image corner extraction algorithm based on linear polarization feedback is introduced in the process of camera calibration, this method is mainly aimed at the problem of high-light regions which are difficult to detect and eliminate in the multi-position calibration image of space under natural light. The method firstly adopts the linear feedback of Stokes variable through a CCD camera with polarizing plates and obtains the corner image of the optimal angle of the checkerboard lattice in different positions in space, then we use the sub-pixel level detection algorithm and GAUSS's fitting method to precisely locate the corner points in the image and to solve the sub-pixel coordinates of the image corner, at last, the two-dimensional pixel coordinates of the corner points in each checkerboard image are extracted.
Evaluation of the diffraction correction during the 10th International Comparison of Absolute Gravimeters (ICAG-2017)
The curved wavefronts of a Gaussian beam used in absolute gravimeters introduce a systematic error in the measured gravity value. Diffraction correction is defined to denote the correction of the error. This paper presents an evaluation of the diffraction correction for some absolute gravimeters participated in the 10th International Comparison of Absolute Gravimeters. An automatic M2-measurement instrument is introduced to achieve an efficient and accurate measurement of the beam waist diameter. On the basis, the diffraction corrections are calculated and estimated. The results indicate that the waist diameter of two laser beams deviates from the typical value. After optimized, the diffraction corrections of all the estimated AGs are less than 2.4 μGal. The accuracy of the correction is better than 0.1 μGal. This work is of great significance for improving the accuracy of the gravity measurements in the comparison.
Improved two dimensional micro-/nanoradian angle generator with single rotation center located on tilting plane and error compensation of capacitive sensors
Fan Zhu, Xinran Tan, Jian Shi, et al.
An improved two dimensional micro-/nanoradian angle generator (2D-MNAG) with single rotation center located on the tilting plane and error compensation of capacitive sensors is presented in this study. The 2D-MNAG is structured on an optimized flexure hinge with single rotation center in orthogonal axes. The rotation center is located on the center of tilting plane of 2D-MNAG so that there is no linear displacement coupled in the angular output of the tilting plane. Three capacitive sensors are used in the 2D-MNAG to monitor the angular output for feedback control. The principle error of capacitive sensor while used in angle measurement is compensated using an established model, thus to improve the accuracy and repeatability of the angular output. A synthetic output error of 0.212 arcsec of 2D-MNAG is obtained using Monte Carlo simulation while the distance from rotation center to each driving and angle monitoring point is 40 mm with manufacturing and mounting errors in the range of [-0.01, 0.01] mm in rectangular distribution. The performance of the angular output monitoring unit and the strategy for closed-loop control are the key for improving the 2D-MNAG while the mechanical structure and driving unit are optimized.
Dependence of micro-morphology of electrical strain gauges on stress distribution
Zhigang Wang, Chi Xiao, Yunlong Mao, et al.
We investigated the determinations by the micro-morphology of the sensitive grids of resistance strain gauge on their stress distributions. The micro-morphologies of the sidewalls for four typical resistance strain gauges were observed by scanning electron microscopy (SEM), and then the microscopic images were binarized to obtain the micromorphological characteristics of the sensitive grids. The observation shows that the sidewalls of the sensitive grids have periodic microstructures. A geometrical model of sinusoidal contour and a strain transfer model was established following the observed micro-morphological features. The influence of the amplitude and period parameters of the sinusoidal contour on the stress level of the sensitive grid was calculated numerically. The results show that the maximum stress increases, however the average stress decreases, with the increase of the profile amplitude with a certain periodicity. For a sinusoidal profile having a fixed amplitude, its maximum stress decreases with the increase of the cycle, wherever the average stress increases. The smaller side wall defects and longer interval in a sensitive grid would make the stress distribution more uniform. The obtained results would provide guidance for the fabrication of the resistance strain gauge.
Research and evaluation of geometric element data fitting software for coordinate measurement machine
Standard geometry element fitting software is a critical important part of the coordinate measuring machine ( CMM ). It is used for coordinate data processing and data evaluation. At present, the commercial fitting software of the coordinate machine manufacturer is not disclosed to the public. So it is inconvenient to develop secondary applications. This work developed a kind of geometric element fitting software based on open source code. The software can be used to fit CMM measurement data to common geometric elements including lines, circles, planes, spheres, cylinders, and cones. The core algorithm of software is based on a least-squares algorithm and a Gauss-Newton iterative algorithm. Least squares is a data optimization technique that seeks the best function match of the data by the sum of the squares of the smallest errors. The basic idea of the Gauss-Newton iteration method is to replace the nonlinear regression model with the Taylor series expansion approximation. Then through multiple iterations, the regression coefficient is modified several times so that the regression coefficient continuously approaches the optimal regression coefficient of the nonlinear regression model. Finally, the residual square sum of the original model is minimized. The accuracy of fitting results are verified with the standard reference data developed by national institute of standards and technology. The software can be used to the geometry element measurement uncertainty evaluation.
Comparison of spacing detection algorithms for optical straight fringes images
Optical fringe is one of important output information from the optical systems. Some important optical or system parameters can be obtained by analyzing the fringe information from optical system such as interferometer system or diffraction setup. The straight fringe is a kind of optical fringes frequently appearing in Young’s double slit interference and single-slit diffraction and other optical structures. For the information extraction of straight fringes, it is often necessary to calculate the fringe spacing parameters. Popular straight fringes analysis methods include the fringe center method and the Fourier transform method. In addition, some image processing methods realized line detection can also be used to analyze this straight fringes image, which include Hough transform and Radon transform. In this paper, four algorithms for fringe analysis are discussed and compared, which focus on method’s principle, algorithm’s simulation and performance when they be applied to detect the fringes spacing. At the same time, the anti-noise performance of two image processing algorithms including Hough transform and Radon transform are analyzed.
Phase measuring method and error compensation in 3D profile measurement
3D profile measurement is widely used in many areas such as manufacturing, computer-aided design, virtual reality and medical diagnostics. As one of the core technologies in 3D profile measurement, digital fringe pattern projection is a highly sensitive noncontact technique for obtaining the 3D shape of an object. Then the grating pattern deformed by the measured object is captured by CCD cameras and decoded using appropriate algorithms so that the shape of the object can be deduced. In this paper, three sets of phase shift fringe patterns with different frequencies are projected on the surface of the measured object by a DLP projector and the deformed patterns are captured by two cameras. Then the four-step phase shift method is used to obtain the three groups of fringe patterns phases, and the three-frequency heterodyne method is adopted to unwrap the phase and obtain the absolute phase. The causes of the phase errors are analyzed and the subsequent compensation method of gamma correction of grating pattern is proposed to eliminate the main errors. Experiments are carried out and the results verify the accuracy and effectiveness of the proposed methods.
A design of high-accuracy angle measurement system for satellite AIT processing
In order to solve the problems and shortcomings of current angle measurement methods for satellites assembly and inspection, such as limited field of vision, relatively low precision and low degree of automation, a novel design of high accuracy angle measurement system is proposed. The new system composed of auto-collimator, electronic gradienter, two-dimensional precise turntable and standard mirrors works by actual collimation measuring among the measured target, auto-collimator and standard mirrors with the measuring basis of earth which is built by electronic gradienter. This paper focuses on the specific structure design, engineering modal and arrangement plan of automatic measuring, also includes precision calibration test in the end. According to the result of the test, the angle measurement system reaches the precision of 3″and repeatability of 1.1″.
FPGA-accelerated one-dimensional Fourier reconstruction LCD defect detection algorithm
With the development of high-generation production lines for Liquid Crystal Display (LCD) panel, online real-time detection of large-scale, high-resolution LCD surface defect imposes stringent requirements on image algorithms and computing platforms. This paper aims at the edge effect in the traditional one-dimensional Fourier reconstruction LCD detection algorithm. Based on the potential periodicity of the Fourier transform and the approximate periodic arrangement of the element array in LCD panel images, a complete period truncation image preprocessing strategy is proposed. The processing strategy not only eliminates the ring effect at the connection joint caused by the original algorithm's extending period at both ends of the image, but also reduces the length of the Fourier operation, which is even more noticeable when detecting large-size panels. In addition, in order to adapt to the fast Fourier transform input interface, the resampling method is applied to the complete period truncated image whose length is not an integer power of 2, and an FPGA-based resampling acceleration structure is designed. The experimental results show that compared with the traditional one-dimensional Fourier reconstruction algorithm, our proposed method not only performs better in eliminating LCD global periodic texture, but also reduces the amount of data to be processed. The FPGA acceleration scheme even reduces the scanning detection time of a 8.5-generation LCD panel to 12.5s
Keysight B1505A power device analyzer output pulse current calibration method
Beichen Guo, Shuqiang Wang, Jingjing Li, et al.
Keysight B1505A Power Device Analyzer has many functional testing projects, the calibration method is more complex. This paper focuses on how to control the output current of Agilent B1505A, solves the problem of impedance matching when calibrating pulse width and we investigate the relatively high accuracy test pulse amplitude method. After comparing the technical specification of the oscilloscope TDS3032C with output current resolution, this paper uses the high-precision digital meter 3458A instead of oscilloscope as the standard for measuring the amplitude of pulse current. In this paper, we investigate the configuration problem of 3458A for the trigger level, the delay time and the integration time in the pulse test, which makes the test result more accurate. A calibration system is designed to convert the pulsed current through the Tektronix Company's current amplifier TCPA300 to smaller voltage signal, which can be read by 3458A. Thus, the 3458A is used to measure the high accuracy of 1-2V voltage amplitude. The method is verified through calibration to show higher accuracy, which has a strong practical application value. At last, we give the uncertainty evaluation in the calibration process , the result is less than Urel=0.2% (k=2). More accuracy than using an oscilloscope as a standard measurement.
Review of convolutional neural network optimization and training in image processing
Major breakthroughs in the fields of image processing, pattern recognition, and scene classification have recently been made through the using of convolutional neural networks (CNNs) and deep learning. If the training set is sufficient, a CNN performs better than traditional machine learning algorithms and differs from them in many ways. In CNNs, feature extraction is more intelligent, so researchers no longer require extensive knowledge about the specific topic. They can focus on the CNN itself, including the structural design of the network, the model optimization, and the numerical solution. The many articles on CNNs published over the past few years propose many neural network models. Methods of training and optimization for CNNs have also been proposed. This paper reviews the history of CNNs, introduces the commonly established CNN structure, and summarizes methods and tips for CNN training.
A passively Q-switched dual-frequency Nd:YAG laser for SBS generation and amplification
Jun-hong Xing, Ne-jie Zhang, Ye Zhou, et al.
Elasticity modulus is a critical parameter to determine the mechanical characters of the human tissue and materials.The new stimulated Brillouin scattering (SBS) method possesses the unique characters of high speed and resolution. In this study, a SBS measurement system of elasticity modulus has been developed using a passively Q-switched dual-frequency Nd:YAG laser as the source, where two beams acting as pump and pumping lights are employed to generate the seed mode of SBS and then amplify it on ectogenous area, respectively. Thus the frequency shift and line width of SBS can be easily got from heterodyne method. Both the oscillation and output characteristics of the dual-frequency pulse laser have been investigated. The simple and efficient SBS setup allows for the generation and amplification of SBS, which will provide a reference of the application SBS of detecting dynamic change on human tissue and materials in biomechanics and medicine science.
Effect of varying load on angle measurement deviation of rotary table
Jia Hou, Zi Xue, Yao Huang, et al.
The angle measurement deviation of high accuracy rotary table is sensitive to loading condition. The mechanism of varying load influence on angle measurement deviation was presented and analyzed through numerical simulation. At meantime, a series of calibrations were performed to investigate how much the angle measurement deviation will vary when the operation condition vary in load from 0 kg to 5 kg. A series of angle measurement deviation curves were obtained with cross-measurement method. The amplitudes of deviation curves were compared and the Fourier components of the deviation curves were analyzed. The numerical simulation result was proved. The self-calibration method was used to restrain the additional angle measurement deviation caused by varying load and have obvious effect.
Measurement method of the compression coefficient of near-monocrystalline silicon density liquid
Xin-yu Ma, Jin-Tao WANG, Zhi-Yong Luo
The standard near-silicon liquid (2329kg/m3) is a mixture liquid of tribromopropane and dibromoethane in a certain proportion. This liquid is used to measure the density of single crystal silicon spheres by a static suspension method and the analysis of the difference in the micro density between two silicon spheres. Measuring the difference in the micro-density of the silicon spheres is of great significance for the new definition of the new mass of kilograms. In order to obtain the micro-density difference of the silicon spheres, it is necessary to calculate the static pressure value and the temperature by separately adjusting the singlecrystal silicon spheres to the same suspension state and the compression coefficient of the near-monocrystalline silicon density liquid. Through the adjustment of the same hydrostatic suspension state of a single silica ball in different suspension states, the linear constants measured by the linear model are analyzed to calculate the liquid compression coefficient. For this purpose, a static suspension measuring device for a single crystal silicon ball was designed to maintain the water bath within a range of ±0.1mk within 3 hours, and the position control of the silicon ball was determined by controlling the pressure of the upper computer.
Research on omnidirectional motion of AGV based on vision guidance
Jian Bao, Zai Luo, Dong Li
This topic mainly studies the navigation parameters obtained by image processing technology to achieve omnidirectional mobile AGV autonomous navigation. The camera is mounted on the bottom of the body of the AGV and captures the black tape path on the ground. Image preprocessing is performed, including image graying, improved CANNY algorithm edge detection, morphological processing, and so on. Then the Hough transform is used to detect the path of the preprocessed image. Finally, a straight line is selected to obtain the effective edge line, and the navigation deviation parameters are extracted. Experimental results show that the effectiveness of the guidance techniques in this paper has achieved the expected results.
Measurement of deionized water density based on single silicon sphere
Jin-Tao Wang, Jing-Yue Zhang, Xin-yu Ma, et al.
Due to perfect stability, deionized water is usually used as one important reference material for density and volume calibration. To evaluate suitability of pure water density formulas for deionized water, one measurement system based on Archimedes’s principle was designed, and silicon ring was used for density standard to measure the density of deionized at 20°C. The experimental result shows that The Tanaka equation can be used to calculate the density of deionized water with deviation 5ppm. The uncertainty budget of measurement is analyzed, and the combined relative uncertainty is 4.09ppm (k=2).
Non-destructive rapid inspection methods for spatial light modulator using swept source optical coherence tomography
A high speed swept source optical coherence tomography (SS-OCT) system has been proposed for tomographic map of spatial light modulator. In the optical arrangement, a swept-source with 100 kHz axial-scanning rate and a compact Michelson interferometer was applied. The implemented SS-OCT system has an axial resolution of 15μm and penetration depth of 12mm. The two-dimensional tomographic grayscale maps of the sample can be obtained in real time. As a result, the thickness of glass substrate, liquid crystal layer and the silicon substrate could be obtained simultaneously. Compared with the traditional detection methods, The SS-OCT system has the characteristics of fast imaging speed, stable repeatability of measurement with high-resolution and non-destructive.
More efficient optical sectioning structured illumination microscopy
In this paper, a structural illumination based technology for microscopic surface topography measurement is investigated, in which only one shot structural illumination image is grabbed and a more efficient optical sectioned image reconstruction algorithm based on Hilbert transform was proposed. Compared with other methods, the technology can avoid strip artefacts problems of in-focus images resulting from the sinusoidal phases mismatch in spatial domain in conventional three-step phase-shifting since the phase-shifting steps decreases from three to one, and the measurement time is decreased effectively. The experimental testing is carried out to verify the feasibility and its measurement accuracy.
Probe error analysis of articulated arm coordinate measuring machine
Zeliang Cai, Zai Luo, Hui Liu
Researched on the probe’s diameter error of the Articulated Arm Coordinate Measuring Machine (AACMM) in the measuring process. Based on the analysis of the influence of the error source on the accuracy of the probe, the influence of the contact force on the measuring diameter of the probe was analyzed emphatically. It was proposed to use the Coordinate Measuring Machine (CMM) to identify the probe diameter error of the AACMM and apply the least square method to compensate the probe diameter error. The results show that the research method has certain feasibility. The maximum error of the length measurement is reduced by about 47 um. The average error is reduced from 0.0315 mm to 0.0046 mm, which improved the measurement accuracy of the AACMM.
Parameter identification of inertial velocity sensor for low-frequency vibration measurement
Junzhong Li, Lei Wang, Bo Zhao, et al.
Whether velocity sensor can accurately acquire payload vibration information has become the most important factor that restricts vibration isolation performance. In order to get accurate sensor parameters, DC excitation method is used to measure the central frequency, damping ratio and sensitivity of inertial velocity sensor. The influence of different currents on the measurement accuracy of sensors such as response voltage, central frequency, damping ratio and sensitivity is analyzed, and the optimal current value is determined, which provides a powerful guarantee for obtaining accurate sensor parameters. Finally, the GS-11D sensor is used to carry out the experiment. The experimental results show that the relative error of the central frequency, damping ratio and sensitivity of the DC excitation method can meet the application requirements.
Design, fabrication, identification and test of a closed-loop moving magnetic scanning module for RGB laser projector
Chien-Kai Chung, Chen-Chang Lin, Ming-Fu Chen, et al.
Galvanometric scanning systems are high inertial behavior and high-speed movement widely that be used in laser marking, drilling, full screen projecting and so on. Therefore, the presented galvanometric scanning system and its applications for laser projector system. In includes a galvanometric unit, motor, position detector and control circuit. All components were discussed and developed by this study. The magnetic rotor and a stator magnet are the main components of the scanner system. The moving magnet is composed of NdFeB material and the stator consists of the coil. In addition, the moving capacitive sensor is used to receive signal feedback. The driver is assembled by the high response performance OP-amplifier circuit. Finally, frequency domain methods were used to identify the scanning system.
Force control and visual measurement in precision assembly
Yawei Li, Xiaodong Wang, Yi Luo, et al.
On account of the assembling demand for the metal framework of frequency stabilizing component for laser gyro, a precision assembly system was designed and developed in this paper. The coaxiality of the metal framework and the grooved mirror is the key index to assembly. Meanwhile, the grooved mirror is fragile and the assembly force has to be monitored and controlled in real time. The installation structure of force sensor is designed and a force control unit is established. The contact force can be detected and feedback to control the movement of the linear stages to complete the displacement in the vertical direction for the operation of pick up and place parts for end effector. To reduce the time of image processing, the machine vision unit is based on high repeatability accuracy of the stage to assist image mosaic, thus the calculation workload for image mosaic is reduced, and the time of image mosaic is about 0.5s.
Adaptive segmentation method of pressed character image based on Wellner algorithm
Xili Duan, Jing Le, Yuyang Ming, et al.
The image of pressed characters on the surface of metal workpieces in industry has obvious unimodal characteristics, for this feature, this paper proposes an adaptive segmentation method based on Wellner algorithm, this method is used to segment the pressed character image whose character gray value is similar to background gray value. Firstly, we use uniform illumination to capture grayscale images. Next, the Retinex algorithm is used to enhance the details of the character edge, the grayscale distribution range is expanded to improve the image contrast. Then, the bilateral filtering algorithm is used to filter the image noise. In this paper, the pixel gray value of a certain point is selected as the center, the row and column mean value of the pixel is calculated, at the same time, the mean value of the pixel gray value in the 8-connected region that it belongs to the pixel selected to be the center is calculated. The algorithm applies the “center-around” idea, the Wellner algorithm is improved with the mean value and the image pixel points are traversed to achieve image binarization. Finally, the final segmentation result is obtained by combining morphological operations. The verification experimental results show that the proposed method has good self-adaptiveness and accuracy for the gray-scale histogram image with unimodal characteristics.
Research on calibration method of rotating axis in line structure light measurement system
In line-structured light measurement systems, in order to achieve higher 3D reconstruction accuracy, it is necessary to calibrate the rotating shaft accurately. When the sensor and the tested part are in the same horizontal plane, it is impossible to measure the characteristic point data of the whole week, so that the calibration of the rotating shaft is inaccuracy. Therefore, in this paper a calibration method of rotating axis based on coordinate transformation is proposed, the sensor performs rotational axis coordinate calibration above the planar target and transform the coordinate of the rotating axis in the sensor coordinate system above the target into the horizontal coordinate system by means of coordinate transformation. This rotary axis calibration method has a certain feasibility because it adopts the method of full-circle revolving calibration, which can effectively improve the calibration accuracy.
Decoupling atmosphere Rayleigh-Brillouin scattering spectrum in kinetic regime
Jingjing Liu, Jiale Kang, Dengxin Hua, et al.
In the detection of atmospheric temperature profile by Rayleigh scattering, the influence of Brillouin scattering is usually ignored and the accuracy of temperature detection is reduced. Current researches on Brillouin scattering are mainly focusing on hydrodynamic and Knudsen regime, few researches has been done on the kinetic regime. In order to improve the precision of atmospheric temperature measurement, a mathematical model based on three Gussian distributions was adopted to study the Rayleigh-Brillouin scattering spectrum (RBS) in kinetic regime, the mixed Rayleigh and Brillouin signal in atmospheric echo signal is separated to obtain independent Rayleigh and Brillouin spectrum. Finally, the experimental platform was set up to control simulation of atmospheric environment system and establishes a hyperspectral splitting optical system based on Fabry-Perot interferometer. The spectrum obtained by the experiment was used to optimize the mathematical model and improve the detection accuracy of atmospheric temperature profiles.
Automatic real-time compensation of wavelength of heterodyne interferometer
Wei Jin, Qi Li, Yushu Shi, et al.
Heterodyne interferometer is a nanometer measurement system that uses the laser wavelength as the working reference for length measurement. Under ideal conditions, the laser wavelength is the wavelength λ0 of the light wave in the vacuum, but in practical applications, the laser wavelength will change with the influence of the air refractive index and the refractive index of air is greatly affected by the environment. This will have a great influence on the measurement results of the high-precision and high-resolution nano-displacement measurement system. Therefore, it is necessary to correct the air refractive index to compensate the laser wavelength. In this paper, the air refractive index in the initial measurement is obtained by using the Edlen empirical formula. Then the relationship between the current air refractive index and the initial air refractive index is obtained by using the wavelength compensation unit to achieve the automatic real-time compensation of the wavelength. The wavelength compensation component is mainly composed of an interference mirror and a fixed length etalon. Through the measurement of air refractive index and the experiment of compensation, the feasibility of the method is confirmed. The relative error after wavelength compensation is less than 0.03% relative to the relative error before compensation.
A real-time nonlinear error measurement method with picometer accuracy and free from target motion state
Haijin Fu, Yue Wang, Ruidong Ji, et al.
Nonlinear error measurement technology is critical for the development of heterodyne laser interferometer. The existing periodic nonlinear error measurement methods is limited in measuring the nonlinear error of the heterodyne interferometer with double-direction Doppler frequency shift during the measured target non-constant velocity motion. To solve the problem, this paper presents a new method of measuring the nonlinearity in picometer level based on the double-channels orthogonal demodulation. A pair of orthogonal signals generated by FPGA multiply with the two output signals of the interferometer, respectively. And two pairs of beat frequency signals are obtained through low pass filtering, which are then mutually multiplicative and obtain the sine and cosine components containing the overall nonlinear errors of the interferometer by mathematical operations. At length the nonlinear errors are obtained through them. The experiments show that the method can measure the periodic nonlinear error in real-time free from target motion state and the measurement accuracy is in picometer level.
Design and testing of a chromatic dispersion system for displacement application by using a spatial-bandpass-filter
Chromatic confocal displacement measurement is a newly developed technology for linear precision positioning with a sub-micron meter accuracy over a millimeter order range. In this technique, the chromatic spectrum of a white light source is divided by an optical dispersion system. The encoded spectrum disperses along the axial direction, with which the axial position can be detected by a spectrometer at a high precision. Thus, the optical dispersion system that determines the final measurement precision is required to own a large dispersion capacity and a small spherical aberration. A chromatic dispersion lens (CDL) module and a spatial-bandpass-filter (SBF) were proposed in this research to improve the dispersion performance. Based on the geometrical imaging principle, the CDL and SBF parameters were preliminarily designed and further tested by the optical design software ZEMAX. The testing results verified that with SBF and CDL, the spherical aberration was largely reduced and the imaging quality was greatly modified. The focus beam spot of the central wavelength 550 nm can be as small as 10μm. Under such a condition, the measurement error is no larger than ±0.7μm over a 1700μm measurement range.
Instrument and equipment monitoring system based on the internet of things technology
Meng Su, Shengyu Wei, Linyi Huang, et al.
For daily use process of monitoring instruments, improve the efficiency of using equipment, this will have especially important significance to establish equipment running condition monitoring system based on Internet of things. This study will focus on different instruments and equipment in the course of everyday use switch machine, working time, power consumption and status of remote monitoring, transmission, recording and analysis of management, easy to master by the instrument use and management of each instrument for a period of time. Instruments and equipment for daily use monitoring system to realize the instruments and equipment in different departments of the remote wireless or LAN monitoring, the server software for real-time analysis of testing data, it is concluded that the instrument for a period of time of use.
Directional phase-shift circular arrays targets for out-of-focus camera calibration
We design a directional phase-shift circular arrays targets to calibrate camera system under the assumption that targets are in a defocus condition. In contrast to conventional camera calibration method, we can achieve accurate camera calibration with severely defocused images by using the proposed directional phase-shift circular arrays targets. In this paper, three directional phase-shift circular arrays targets are used to calibrate the measurement system. We set up a mathematical model to detect the feature points accurately even though the targets images are seriously blurred. In the experiments, the targets are displayed in a LCD monitor, camera system can capture the three targets images at the same position to extract the feature points. Gaussian filters are utilized to blur the targets images to simulate the fuzzy images. And we obtain targets images with different defocus degree by adjusting the depth range of the actual camera system. We have done a series comparative tests with checkerboard. We evaluate the performance of the proposed method on simulated and real data. Finally, the measurements of displacement and morphology are implemented. Experimental results indicate that the directional phase-shift circular arrays targets can be used to achieve accurate camera calibration parameters.
Accurate measurement of displacement using acceleration signal
The accurate measurement of displacement and load in the oil well dynamometer diagram is the need to achieve energy saving, efficiency and stable production. Wherein, the displacement signal is calculated from the acceleration signal in the dynamometer. Theoretically, the acceleration signal can be integrated by two time-domain integrations to obtain the displacement signal. However, the noise and direct-current(DC)components in the time-domain signal would produce a drift-type principle error after two integrals. In order to solve this problem, this paper has proposed a frequency domain integral-based displacement solution method. Meanwhile, this paper has expounded the principle of frequency domain integration and analyzed the possible sources of error of the obtained results. An evaluation model was proposed experimentally verified. Test results indicated this method can be used to improve the accuracy of displacement measurement. This research has important implications for improving the economic benefits of the oil field.
Development of portable digital ultrasonic guided wave detector based on COM Express
Meiju Zhang, Wei Liu, Defeng Liu, et al.
This paper proposes a portable ultrasonic guided wave detector based on ADLINK COM Express (Computer On Module Express) computer module. This detector is equipped with Windows7 operating system and uses the PCIe (Peripheral Component Interconnect Express) bus as the FPGA (Field Programmable Gate Array) of COM Express and Xilinx. The data transmission rate can reach 500MB/s in the transmission line. In addition, a self-developed high-voltage pulse signal generation circuit and signal acquisition circuit are used in the analog circuit. Finally, this developed detector is used to excite ultrasonic guided waves in the aluminum plate and the pipe to realize the identification of defect echo signals in these two structures, which verify the reliability of the designed detector.
A measuring method of coaxiality errors for apart axis
Yuansong Zheng, Zhifeng Lou, Ying Li, et al.
Mechanical failure is primarily caused by coaxiality errors of axis. Traditional methods (synthetic gauge testing methods, method of rotary axis, coordinate measuring machine, etc.) for detecting coaxiality have some disadvantages such as: low efficiency, sensitive to human factors and cannot be used to measure the axis that is far apart without connection. In this paper, based on the principle of laser collimation, a method for measuring coaxiality errors of non-connecting axis with long distance was proposed. By rotating the laser module and the four-quadrant photo detector module respectively, the center and radius of the circle that formed by the laser spot were used to calculate the angular deviation and the parallel deviation. Finally, a measurement system based on the precision instrument deflection was designed to verify the rationality of the method.
Fabrication process and measurement of injection molding aspheric lens
The aspheric optical plastic injection molding technology has many advantages such as lightweight, low cost, saving assembly work, easy mass production and so on. It is the main processing method for aspheric optical plastic lenses. This paper systematically summarizes the error sources in the process of optical plastic injection molding, and displays the current development status of error detection technologies. A method based on wavefront sensing technology for transmission aspheric optical lens error detection is proposed. Finally, this paper gives the prospects for the development of error detection technologies applied in aspheric optical lens.
A compact design of optical scheme for a two-probe absolute surface encoders
Xinghui Li, Yaping Shi, Peirong Wang, et al.
An improved optical scheme of planar encoder is presented in this paper. The modulation of diffractive beams from scale grating and reference grating is analyzed systematically. Based on this analysis, independent modulation of eight diffractive beams from scale grating and reference grating, with no cross effect between each other, is achieved with an improved design of easy to adjust and simplicity in structure, cost-effectiveness and flexibility in use. Furthermore, in this research, the optical configuration of the planar encoder was divided into three function areas, modulation of diffractive beams, optical subdivision and photoelectric detection. Separate design decreases the coupling relationship between various optical elements, which improves the convenience of optical alignment and reduces the cumulative error in debugging process to a certain extent. In this study, a standard interference ranging system is set up by using a grating with a 1μm period. The typical four path interference signals are collected. The quality of the interference signal verified the feasibility and superiority of the innovative design.
Wavelength calibration system for diode laser
Xiang Cheng, Xiaojun Liu, Changchun Chai, et al.
Currently the diode laser is widely used in the field of optoelectronics, especially in precise measurement based on laser-interferometry. Laser wavelength stability is a property that critical to the measurement. Since the laser wavelength is easy to be influenced by the environment and drive current, real-time monitoring and calibration of diode laser wavelength is extraordinary important for interferometry. In this paper, a real-time wavelength monitoring and calibration system for diode laser based interference measurement were developed. The experiment system was built and conducted to verify the feasibility of the system.
Choice of optimal resolution and array for integrated photosynthetically active radiation spectroradiometer
S. S. Baev, I. A. Konyakhin, V. V. Korotaev, et al.
The article is devoted to development of a spectroradiometer for an automatic controlled lighting system for plants cultivated in a greenhouse. The error of the spectroradiometer due to the discreteness of the multielement photodetector and the ratio of the entrance slit monochromatic image half-width to the step of the elements are considered. Relative error of photosynthetically active radiation bands ratio measurement for various instrument line functions is calculated. The results of an experiment for mass-produced optical multi-element photodetectors with different widths of sensitive elements for different entrance slit monochromatic image half widths of a polychromator are presented.
Characterization of surface roughness by double blanket model from laser speckle images
The surface laser speckle image is obtained by the reflected and scattered light beams from a rough surface illuminated by laser. Based on the fractal theory, Double Blanket Model (DBM) is proposed to analyze laser speckle images. The dimension of the space surface is regarded as the characteristic parameter in DBM method. Laser speckle images are preprocessed to remove interference and noise from the environment at first. The size and direction of optimum window are researched. The DBM characteristic parameter is calculated under the optimum window. The relationships are researched between DBM characteristic parameter and surface roughness Ra. The results show that the surface roughness contained in the surface speckle images has a good monotonic relationship with DBM characteristic parameter. To obtain roughness value through a laser speckle image, the fitting function relationship between Ra and DBM characteristic parameter is established, and the fitting function stability is analyzed by experiments. The experiment results show that surface roughness measurement based on DBM method of laser speckle is feasible and applicable to on-line high-precision roughness detection, which has some advantages such as non-contact, high accuracy, fast, remote measurement and simple equipment.
Embedded intelligent camera algorithm based on hardware IP
Guodong Liu, Qifeng Luo, Bingguo Liu, et al.
This article designed an embedded smart camera based on the ZYNQ-7000 development board, which has an ARM+FPGA architecture. The system functions are divided into three parts: image acquisit ion, image processing and image display, each of them adopting a modular design. The image acquisition part adopts OV7725 camera. The image processing section uses the VIVADO HLS development kit to design hardware IP-based image processing algorithms. Compared with the traditional HDL-based IP core design method, HLS method that use C/C++ to design IP reduces the development difficulty and shortens the development cycle. Hardware IP implemented through HLS includes image preprocessing, spot-based centroid positioning algorithm, edge detection and corner detection. For complex image processing algorithms, it is still used software to implement, while preprocessing are accomplished through hardware IP. The VDMA channel realizes high-speed data interaction between hardware and software. The image display part is based on the embedded Linux system, OpenCV, and cross -platform C++ graphical user interface development framework QT to implement the GUI interface. The entire embedded smart camera system finally achieves accelerat ion processing based on hardware IP, such as spot location, sobel edge detection, and corner detection.
Detection of ring gear surface defects of wheel speed sensor based on neural network
Zhenwei Huang, Jina Liang, Liu Lei, et al.
In view of the low efficiency and slow speed caused by the manual inspection of the wheel speed sensor ring gear in the automotive parts industry, this paper proposes a method for detecting the surface defects of the ring gear of the wheel speed sensor based on the neural network. The method is based on the single hidden layer BP neural network model, and the LM algorithm is used to train the network to achieve stability, the defect types are identified by combining the image feature parameters of various gear ring surface defects. The surface defects detection results of the wheel speed sensor ring gear show that the defects classification accuracy of this method is more than 94%, and the detection time of each ring gear is less than 4s. The detection result is better than the manual visual method.
The optical-electronic autoreflection sensor for angular deformations measurement
Igor A. Konyakhin, Aiganym M. Sakhariyanova
The construction features of autocollimation systems for measurement the large-sized and extended objects deformations at industry, power and scientific instrument making are considered. The conditions of increase of a distance of measurement are analyzed in comparison with the serial autocollimation devices. The error of measurement by the restriction of a working beam is investigated. The structure of algorithm for reduces the systematic error of the measurement which based on received analytical expression of function of an error is determined.
Design and testing of a compact optical prism module for multi-degree-of freedom grating interferometry application
Xinghui Li, Xiang Xiao, Haiou Lu, et al.
In this research, a key optical component for multi-degree-of-freedom (MDOF) surface encoder was designed, fabricated and evaluated. In a MDOF grating interferometry system, there are four diffraction beams from the scale grating and reference grating. For further modulation, these beams will propagate more than 100 mm, which makes paralleling these beams necessary. In previous researches, separate prisms and a home fabricated diffraction device by combining four separate one-axis line gratings in a glass substrate have been demonstrated. However, large power loss and assembly complicity makes this technique less competitive. For solving this problem, this research proposed a new lens module, which is an improved type prism, quadrangular frustum pyramid. The prism is designed in such a way that these four reflected beams from the grating are symmetrically incident into the prism through the upper surface, total reflected on the inner sides of the prism, and then paralleling propagate through the bottom surface. A prism that allows an incident beam diameter of 1 mm and four paralleling beams with a 10 mm distance between the two diffraction beams along one direction was designed, fabricated and tested. Testing results based on an entire grating interferometry system verified that the proposal in this research is greatly effective in beam paralleling in terms of less power loss and high paralleling and greatly reduce the assembly complicity, which will eventually be beneficial for grating interferometry application.
Design and implementation of flexible display reliability testing instrument
Meng Su, Nannan Zhu, Linyi Huang, et al.
In this paper, To the reliability life test of flexible display as the research target, the main factors affecting the flexible screen's reliability performance were analyzed and establishes a reliability automation test system based on LabVIEW. We will use open, modular design and flexible hardware framework, can increase the hardware configuration according to customer product testing requirements, has a good price and good versatility. The test process will be automated, the test results will be displayed in real time, and the test data storage, analysis and print. Through the establishment of this system, the entire testing process is automated, which greatly saves the cost of testing and improves the degree of automation and reliability of the test.
A real-time distance measurement data processing platform for multi-axis grating interferometry type optical encoders
Xinghui Li, Su Xiao, Qian Zhou, et al.
Among various nano-scale linear displacement sensors, grating scales have been widely used in industrial fields due to their strong anti-interference ability, cost-effectiveness and compactness. The main development directions of the scale are: high precision, large range, high speed, high dimension and absolute type. Our team has completed the optical layout design of the absolute two-dimensional grating rule, which brings new challenges to the design data acquisition and processing hardware system due to the requirements of multiple dimensions and high speeds. There is no real-time data processing system suitable for absolute two-dimensional scales. This paper presents our latest progress in designing and implementing an absolute two-dimensional grating distance measurement real-time data processing platform. Our platform mainly contains four different functional modules. First, the circuit conditioning module performs I-V conversion and signal amplification and filtering on the weak current signal output from the photodiode. Secondly, an 8- channel high-speed data acquisition module with 14-bit resolution and 80 MSPS maximum sampling rate was designed to convert analog laser pulse signals into digital signals. Third, we have established a real-time data processing module that allows 16 bits of data to be entered in the FPGA to calculate the absolute two-dimensional scale distance. Finally, a data transfer module based on 128MB DDR SDRAM and USB 2.0 was added so that we can easily debug the platform on a PC. The performance of our system is evaluated in real time. The test platform consists of a laser, a twodimensional grating optical path, and our data processing system. The absolute two-dimensional scale has a moving speed of 1m/s, a signal frequency of 10MSPS, a laser emitting signal wavelength of 540nm, and a moving distance of 10-15mm. Experimental results show that our system can output at a rate of 2500 points per second. Measurement results, measurement deviation is less than 50nm.
A differential giant magnetostrictive mitro-displacement actuator
Actuators made of Giant Magnetostrictive Material (GMM) are used more and more widely in ultra-precision positioning, processing, measurement, and vibration isolation of equipment. While a single Giant Magnetostrictive Actuator (GMA) has low load capacity and non-ideal dynamic output characteristics, this paper presents a differential Giant Magnetostrictive Mitro-Displacement Actuator. The effect of the equivalent stiffness and quality of the load on the output characteristics of the actuator is analyzed by establishing the dynamic model of differential GMA. The experimental results show that compared to a single GMA micro-displacement actuator system, the differential GMA system has a positioning noise of ±3 nm, a resolution of 6 nm within a 18.5μm travel range. In the composite control system, a hysteresis-free sinusoidal displacement output with an amplitude of 3μm within 200 Hz is realized, and the maximum output error is 0.6μm, which effectively improves the dynamic performance of the actuator and improves the load capacity of the actuator.
Defect detection of small modulus gear based on machine vision
Jianguo Tao , Zai Luo, Qi Liu
This paper aims at the difficulty of detecting the size limit of small modulus gear, using machine vision inspection method which is popular in precision measurement to build a rapid gears detection system. Firstly,a series of image preprocessing operations such as grayscale processing, filtering, binarization, and morphological processing are implemented,excluding the background image,and the clear gear target is obtained. Then, the gear contour is detected and the gear feature points are identified. Extract the points on the teeth,and the automatic detection of the number of teeth and the accurate identification of missing teeth are achieved.
Experimental study on non-linear calibration of two-dimensional nano-positioning stage
This paper presents the control and non-linear calibration of large-scale two-dimensional nanometer displacement stage. The stage consists of a monolithic compliant mechanism, which using flexible hinge superimposed branch as a transmission part, driven by three piezoelectric actuators, To certify excellent performance of the stage, a micro-displacement measurement system which based on the measurement principle of a laser interferometer was setted up, then comparison of several stage parameters accomplished between before and after calibration. Based on the measurement of optical path and composition of dual-frequency laser interferometer, a experimental study on nano-positiong stage was carried out. The non-linear calibration method which based on newton-steffensen accelerated iteration are described; The accuracy of the calibration method was verified through experiments. Experiments show that: before calibration, the maximum nonlinearity error of x-axis and y-axis were 4.012μm and 2.875μm. after calibration, the maximum non-linearity of the x-axis is 8 nm and the maximum nonlinearity error of the y-axis is 10 nm, Meanwhile, a mathematical model is established to calculate the coupled displacement and yaw angle, The actual coupled displacement and yaw angle of X/Y were limited to 380nm and 1.4μrad.
Reverse compensation to the angle estimate error using multi-groups sensor
Shuxian Wang, Donglin Peng, Zhiyi Wu, et al.
The magnetoresistance(MR) sensor has been successfully demonstrated in rotational speed and position detection, however, the uneven magnetic field or the installation eccentricity are all decrease the signal quality and influence the reliability of measurement. Therefore, this paper presents the theory of time grating in displacement calculation and proposes a reverse compensation method using multi-groups sensor to improve measurement performance. A pair of linear tunnel magnetorsistance (TMR) sensors are spatially displaced by 90° electrical and excited by sin or cos signals. Another pair of sensors is reversed and diametrically apart to the former. A compensated traveling wave is got whose phase is proportional to the displacement of rotation. The angle displacement is measured by counting the time pulses that serve as measurement standards. The effectiveness of the proposed scheme is verified through a prototype permanent magnet motor system. That shows the amplitude of the measurement error from 0.17° to 0.04°, which reduces 75% by the special arrangement of the multi-groups TMR sensor. Even though the magnetic sensor presented here uses TMR sensors, the proposed technique is suited without any modification for Hall and other MR sensors as well.
Precise measurement of large roll angle using digital speckle pattern interferometry
Jing Yang, Sijin Wu, Weixian Li, et al.
Recently, a non-cooperative method of roll angle measurement using digital speckle pattern interferometry (DSPI) is introduced. Mechanism was deduced and the mathematic model of roll angle measurement was established. The novel method also enjoys some other advantages, such as high-accuracy, stand-off, non-contact, and full-field measurement. However, this method is only used for precise measurement of very small roll angle which is up to a few milliradians due to the limitation of DSPI’s measuring range. In this article, a means of range enlargement for DSPI roll angle measurement is introduced. With this means, large roll angle can be divided into a number of small angles which are measured in sequence. Therefore, the large angle is then determined by calculating the sum of these small angles. The proposed method of roll angle is characterized by high-resolution and large-range measurement.
Ultrasonic characteristics of contact stress of small interference fitting parts
Yue Wang, Zhifeng Lou, Xingyuan Wang, et al.
Press-fit assembly is one of the traditional methods for assembly of interference fitting parts, but the assembly quality cannot be acquired directly from this method. At present, the press-fit curve is employed for quality estimation, and thickwalled cylinder theory (TCT) is used for standard press-fit curve prediction. However, the evaluation results cannot predict the stress concentration occurred on the mating surface, and most interference fitting parts fail due to this reason. This paper aims to explore ultrasound as a tool for non-destructive evaluation of contact stress, and then acquire the contact stress distribution eventually. Therefore, it is more convenient and intuitive to evaluate the assembly quality based on this method.
Bias electric field distribution analysis based on finite difference method with non-uniform grids for a non-contact tunneling current probe
During proposal and development of a new non-contact nano-probe based on tunneling effect, analysis of the bias electric field (BEF) distribution is a key step for modeling and characterization of the probe. However, the BEF between the spherical electrode serving as the probing ball and the surface to be measured has combined features of macro- and micro- dimensions, which makes the modeling of it a far tricky problem. In this paper, a modeling finite difference method (FDM) based on non-uniform grids generation according to the structural features of the BEF is proposed, and the field distribution is solved with high accuracy. The maximum relative calculation error is within 15% compared with calculation results for a bias electric field with regular boundary with analytical electric image method.
An enhanced homodyne laser vibrometer based on an auto-gain module
Ke Wang, Haijin Fu, Di Chang, et al.
This study presents an enhanced homodyne laser vibrometer with adaptability to reflectivity. The reflectivity could be quite different when measuring different target, which caused the variation of the intensity of the interference signals. In order to enhance the measurement range for the reflectivity of the target, an auto-gain module, which could enlarge the interference signals to an optimal range of the analog-to-digital converter, is implemented in the signal-processing card. The intensity of the interference signals could be calculated in the auto-gain module, and then amplified according to a predetermined rule by using programmable gain amplifiers. The experimental results indicated that the laser vibrometer proposed is capable of measuring vibration with surface reflectivity down to 0.08%.
Research on multi-degree-of-freedom and high-precision touch screen characteristic test instrument
Meng Su, Nannan Zhu, Linyi Huang, et al.
This paper takes the touch screen characteristic test as an example,Through the multi-dimensional automatic motion platform, the test pen is driven to move on the touch screen according to the set trajectory. The actual feedback track of the touch screen control board is compared with the previously given track, and the test error is passed. To judge the touch screen's touch sensitivity and linear accuracy. The test system selects the upper computer and the lower computer to control the mode. The upper computer software is used for data acquisition and master control. The upper computer adopts the project database management mode. It can perform the playback analysis and waveform display of the original data of each movement; the lower computer takes The PLC and the three-degree-of-freedom motion slide, etc., control the entire equipment operation by controlling the PLC and the step controller through the host computer software. Through the management system software, motion data and curves can be displayed in real time, data is stored to the database, and the history is played back.
Ultra-precision temperature control of circulating cooling water based on fuzzy-PID algorithm
Thermal pollution is one of the most urgent issues in the fields of ultra-precision measurement and manufacturing, which presents the demand of producing ultra-precision circulating cooling water (CCW) with the temperature stability up to millikelvin level and response time at hundred-second level. In this paper, an ultra-precision CCW producing method based on model identification and fuzzy-PID control is proposed and illustrated. A structure of circulating water loop with ultra-precision temperature control is proposed. A cooling module using of thermoelectric cooling device arrays as refrigerator and a heating module using electrical heating-tubes as heater are employed. A control algorithm based on fuzzy-PID is designed, and a variety of model identification experiments has been carried out to extract key parameters of the modules. Experimental results show that a temperature stability up to ±3mK is achieved, the temperature control resolution is better than 5mK, and the adjusting time of 1K step is 128s, satisfying the urgent need of ultra-precision measurement and manufacturing.
An identification method for casing weld in complex environment
In order to achieve automatic welding of casing welds in complex industrial environments, a casing weld visual identity method is proposed. Firstly, the pipe is detected by combining grayscale characteristics and color characteristics. Secondly, the weld potential regions are obtained by the morphological operation. Finally, weld seam identification is realized based on the positional characteristics of the casing weld on the copper pipe. Experimental studies verified the effectiveness of the method in complex environments.
Image displacement analysis for electro-optical system for deflection measurement of floating docks
An influence of external conditions can lead to a random rotation of the base unit of the electro-optical deflectometer. This will affect the variation of the image coordinates of the control elements in relation to base position, and, as a result, will cause the error in determining the deflection of the analyzed structure. The changes in the position of the image coordinates of the reference marks before and after the base unit rotation of the electro-optical deflectometer was estimated with the help of elements of vector algebra and matrix analysis. The results of the analysis show that errors in the assignment of the coordinates of the control elements are affected not only by the angle of rotation, but also by the position of rotation axis around which the base unit rotates.
Design and simulation of a 2-DOF parallel linear precision platform utilizing piezoelectric impact drive mechanism
Chengliang Pan, Ting Zhang, Tianliang Dai, et al.
With rapid developments of micro/nano science and technology, precision platforms are widely required in the research and industry fields. This paper presents a 2-DOF parallel linear precision platform utilizing piezoelectric impact drive mechanism. With symmetrical flexible structure and specific piezoelectric driving manner, effective and decoupled actuation of the stator is achieved. FEA simulations are conducted to investigate the characteristics of the stator. With established dynamic model of the platform, motion responses of stator and slider in the two directions are simulated and analyzed. With simultaneous actuation of the 2-DOF motions, a motion interaction phenomenon is raised and discussed.
Parameter optimization of measuring and control elements in the monitoring systems of complex technical objects with triple reflector
The aim of the work is to study the methods of minimizing errors associated with nonlinear fluctuations of the light flux in the control system of complex structural and dynamic objects, and the development of distributed, adaptable, modular optical-electronic channels of control of transverse displacements of elements of extended structures based on the autoreflection measurement scheme with several retroreflectors and a controlled, energyefficient source of optical radiation, in the case of numerical analysis of the CMOS matrix field with its displays, the specified error value and control range are provided in real time under changing external conditions.
The meat product quality control by a polarimetric method
Research is conducted in the field of food freshness control. The research object is a sample of meat product. A variant of the investigation of meat samples using a polarimetric method is proposed. It includes the illumination of a sample by polarized radiation with a given state of polarization, the registration of this radiation after passing through the object of investigation and analysis of its polarization parameters. It is supposed that it is possible to conduct experimental tests and mathematical modeling of the processes that are taking place. To accomplish this, it is necessary to study the features of the investigation object structure, which is a turbid, highly scattering medium. The use of the polarimetric method becomes possible due to the presence in the biotissue of anisotropic structures. Taking into account the structure of a meat product flat sample, it is proposed to represent it in the form of a set of plane-parallel plates having different parameters. During the research modeling of radiation passage through a plane sample of muscle tissue was carried out, the degree of polarization at the output of the system was obtained. In addition, a model of the setup has been developed, which makes it possible to evaluate the Stokes vector of output emission experimentally.
Online test method and standard instruments for verification of traffic speed meters based on actual traffic
Lei Du, Qiao Sun, Jie Bai, et al.
Traffic speed enforcement is an important issue to guarantee public road security and to reduce the number of traffic accidents. Traffic speed meters are important legal measuring instruments specially used for traffic speed surveillance and enforcement in China and around the world. An online test method based on actual traffic with no need to close the road is introduced in this paper. Firstly, the principle of the online test method based on actual traffic and the requirements for the standard speed-measuring instrument are introduced. Secondly, three main standard speedmeasuring instruments respectively using piezoelectric film sensors, 3D tracking radar and light barrier are given. Finally, two comparison experiments were carried out in the field to evaluate the field speed-measuring performances of the standard speed-measuring instruments used for online tests for verification of traffic speed meters in actual traffic.
Field test method and standard instruments for verification of traffic speed meters based on test vehicle
Lei Du, Qiao Sun, Jie Bai, et al.
Traffic speed enforcement is an important issue to guarantee public road security and to reduce the number of traffic accidents. Traffic speed meters are important legal measuring instruments specially used for traffic speed surveillance and enforcement in China and around the world. A field test method based on test vehicle is introduced in this paper. Firstly, the principle of the field test method based on test vehicle and the requirements for the standard speed-measuring instrument are introduced. Secondly, three main speed-measuring sensors, including non-contact optical speed sensor, GPS speed sensor and dual-antenna Doppler radar sensor, used in the standard speed-measuring instrument are given. Finally, two comparison experiments were carried out in the field to evaluate the field speed-measuring performances of the standard speed-measuring instruments with different speed sensors.
Design and performance analysis of a novel thermos-structure for measuring thermal drift of optics in a next generation interferometer
In this paper, a design of a novel thermo-structure for measuring thermal drift of optics in a next generation interferometer is presented. The novel thermo-structure is used to change the temperature of interferometer under test (IUT) by radiation since the measurement is operated in vacuum to exclude the affect from air. Besides, the thermo-structure is made of multilayers, intergrated with thermo electric coolers as the source of heat, which can provide a uniform temperature field. In addition, the thermo-structure can also protect the IUT from disturbance of environmental radiation. Performance of the system is evaluated by finite element analysis and simulation results show that it can achieve a uniform temperature field which temperature difference is less than 0.02°C and reduce perturbation of environmental radiation from 2°C down to 0.03°C.
Choosing parameters of active reference mark optical-electronic systems spatial position control
Subject of the research. Parameters relations in active reference mark optical-electronic system spatial position control in presence of vertical temperature gradient is considered. The operation principle of the dispersion method of the vertical temperature gradient determination using colour camera and RGB optical radiation source is described. The basic condition for choosing parameters of active reference mark optical-electronic system is derived from relations that define hardware realization of the system and parameters of the air tract which are used in the dispersion method. Method. The principle of equal influence of error components on the total error is used. There is an assumption that there are no fluctuations of the air tract refractive index in time and space. Main results. The basic condition for choosing parameters of active reference mark optical-electronic system for spatial position control in presence of vertical temperature gradient is proposed. The efficiency of the dispersion method vertical temperature gradient influence minimization is proved. The basic condition proposed condition allows to estimate this efficiency and choose the hardware parameters. Practical significance. The results given in the paper can be used in design of active reference mark optical-electronic systems where the influence of the air tract is strong.
CMC based on unitary linear regression equation
Jingjing Li, Xiaoding Huang, Beichen Guo, et al.
Calibration and measurement capability (CMC) that can provide calibration and measurement capability to the user in the normal conditions. CMC has a variety of expressions. Regression analysis is a statistical technique for studying correlation between key quality characteristics and the cause variables. After independently collecting n groups of experimental data(xi, yi), i=1,2,…,n., we can measure the relevancy between the two variables with the correlation coefficient. According to the stipulations of digital multimeter’s calibration method in JJF1587-2016"Calibration Specification for Multimeters", we can analyse the sources of the measurement uncertainties mainly includes the following aspects. (1)Uncertainties of the measurements introduced by the standard instruments.(2)Uncertainties of the measurements introduced by the measuring instrument’s resolution.(3)Uncertainties of the measurements introduced by the measure repeatability. The components of the above uncertainties over analyzed and an expression method of CMC based on unitary linear regression equation has given.
Method for spherical form error evaluation using cuckoo search algorithm
To obtain the accurate evaluation of minimum zone sphericity, this paper investigates a method in Cartesian coordinates using cuckoo search (CS) algorithm. In this method, an appropriate space is set as the search zone according to the solution obtained which is based on least square criteria. The aim of search is to find the best candidate position infinitely approximating the ideal reference center of minimum zone sphere. In order to improve the search efficiency, two essential parameters in CS, namely the control coefficient α of step size and the probability pa of discovering an invasive cuckoo's egg are set to 0.618 (value of golden ratio) and 0.05 (common value of statistical significance), respectively. The updating of the candidate points is carried out by Levy flights and biased/selective random walk mechanisms. Levy flights mechanism can ensure the real global optimum is not missed, biased/selective random walk mechanism guarantee the diversity of search direction and adaptability of search step size. During the updating, the new solution can be kept when it is better than the old one. In each search iteration, the position which corresponds to the smallest sphericity is regarded as the present optimum solution. When the iteration terminal condition is satisfied, the optimum position and corresponding sphericity are output as evaluation results. The validness of the proposed CS algorithm was tested by an application example, the results indicate that the proposed method has the advantage of excellent convergence and high efficiency, which is suitable for the hith-precision evaluation of minimum zone sphericity efficiently.
Design of Gaussian filters based on odd and even functions used for non-closed circular profile
Jingzhi Huang, Huixin Zheng, Lin Jiang, et al.
In order to solve boundary effect for non-closed circular profile with conventional Gaussian filter, two modified Gaussian filters based on odd and even functions are put forward. By extending original profile data on the boundary effect area, the sampling information on the boundary effect area of non-closed circular profile can be used fully, and then open-loop Gaussian filter is used for filtering. The validity of two designed filters was tested by numerical simulation and experiment. The results demonstrate that the modified Gaussian filter based on even function is more effective to reduce boundary effect than that based on odd function.
Research of variable-frequency big current calibration
Xiaoding Huang, Yazhen Tong, Jianzhen Cai, et al.
Measuring Variable-frequency big current has a great technical difficulty, you first need transfer Variable-frequency big current to small current is easy to measure, and then transfer variable frequency small current to a voltage. In this paper we uses a zero flux current transformer transfer high current into a small current, after then use a shunt transfer alternating current to a variable frequency voltage, realizing high accuracy variable-frequency big current calibration, measurement uncertainty up to 1×10-4,which can meet the needs of the current calibration,it has been used in many project, and achieved good results.
Long-range automatic precision displacement measuring of winding system using double timing belt transmission
The winding system has a long travel range, often reaching several meters or even hundreds of meters. Conventional long-range displacement measuring methods have a large measurement error and are difficult to realize bidirectional measuring. An innovative long-range automatic displacement measuring method and device of winding system is proposed and designed, which uses double timing belt transmission pairs as precise clamping conveyer. By analyzing the displacement error of linear transmission caused by the polygon effect of trapezoid tooth and circular arc tooth, this paper proposes to use circular arc tooth timing belt to reduce the measurement error. Double rotary encoders are used to measure the displacement simultaneously, which can effectively reduce the measurement error caused by the slippage of the timing belt transmission. The proposed method and device has been used successfully in cable displacement measurement of trailing cone automatic retracting and releasing system for air static pressure measurement in aircraft test flight. The experimental results show that the proposed method is correct and feasible, and the displacement measurement error is less than 0.5%.
A uniform and flexible model for three-dimensional measurement of line-structured light sensor
Line-structured light sensor is a three-dimensional measurement method which combines the advantage of high precision and speed, applicable in many fields. The mathematical model of line-structured light sensor is an essential foundation which determines measurement precision. Through the comparison of the three representative models which are deduced from different starting points and analysis of the model constraint conditions, we build a uniform and flexible model which shows the common characteristics and connections of the previous models and combines the flexibility and clear geometric meanings of the structured parameters with a correctable constraint condition. It is suitable to most conditions and structured parameters design of line-structured light sensor.
Subwavelength focusing and experimental detection of large-scale metallic multi-annular metasurfaces
To realize a long working distance and high resolution focusing for diffraction optical element, the large-scale optical elements need to be employed. Based on the vectorial angular spectrum theory and genetic algorithm, a large-scale metallic multi-annular metasurface (MAM) was designed. The MAM realizes subwavelength focusing and has a main focal spot within the range of 0–140 μm. The focal length is 113.5 μm. Using electron beam lithography, the designed MAM was fabricated. The experimental setup was built. The intensity distribution of the main focal spot was experimentally obtained. The theoretical and experimental results have a good agreement, which show that the proposed method can be used to design the large-scale MAM.
The internal air gap measurement equipment for dynamic pressure motor
Tongqun Ren, Bo Qin, Xiangdong Xu, et al.
The size of internal air gap of dynamic pressure motor is an important index to determine its performance and running stability. In order to improve the precision and automation degree of the internal air gap measurement for dynamic pressure motor, an automatic measurement equipment was developed based on modular design concept. The equipment was mainly composed of clamping module, automatic forcing module, and displacement measurement module. During measurement, the stator was mounted by clamping module with a flexible support at two ends. Then an external force was loaded by forcing module, which was a 3-D electric precision motion platform integrating one triaxial force transducer. A relative displacement was generated because of the internal air gap. And the relative displacement increased until the rotor and stator touched each other. Thus the air gap was transformed into an external micro displacement. Finally, the displacement was measured by measurement module, a 2-D precision motion platform integrating double inductive probes, with relative measurement principle. Experimental results showed that the measurement accuracy was about 0.2μm.
Study on resonant high-acceleration calibration system
High-acceleration vibrations have a strong effect on parts damage and engine life in the aerospace field. Demand for high-acceleration vibration calibration devices is urgently required. In this paper, a set of resonant high-acceleration calibration system was established. This system generates high-acceleration based on the principle that the resonant beam reaches its natural frequency at the outside frequency to amplify the acceleration amplitude. Experimental results show the system can achieve accurate calibration of sensors at high-acceleration.
Design of optical accelerometer using four-quadrant photodetector
Ying-Jun Lei, Rui-Jun Li, Zhen-Xin Chang, et al.
Low-frequency vibration is a harmful factor that affects the accuracy of precision machining and high precision measurement. Low-frequency micro-vibration cannot be completely eliminated by air-floating platforms. Therefore, lowfrequency vibration must be measured with high-precision before being suppressed actively. A low-cost high-sensitivity low-frequency optical accelerometer is proposed. This optical accelerometer mainly consists of three components: a seismic mass, a leaf spring, and a displacement sensor (four-quadrant photodetector). When vibration is detected, the seismic mass moves up and down due to the effect of inertia, which is amplified by using an optical lever and measured by the four-quadrant photodetector. Then, the acceleration can be calculated. The resonant frequencies and elastic coefficients of various seismic structures are simulated by ANSYS software to attain the optimal detection of lowfrequency low-amplitude vibration. The accelerometer is calibrated using a homemade vibration calibration system, and the calibration experimental results demonstrate that the sensitivity of the optical accelerometer is 4.92 V (m·s−2 ) −1 , the measurement range of the accelerometer is 0.0095–2.58 m·s−2 , and the operating frequencies range from 5 Hz to 15 Hz. The efficacy of the optical accelerometer in measuring low-frequency and low-amplitude dynamic responses is verified.
A novel two-dimensional inductive sensor based on planar coils
The precision measurement of two-dimensional displacements is needed in many domains, such as precision fabrication and detection. This paper presents a novel inductive position sensor with the capability of measuring displacements in x- and y- directions simultaneously. The sensor consists of two parts: a ferromagnetic plate with primary windings which are composed of four layers of planar coils, a ferromagnetic plate with secondary windings which are composed of four layers of planar coils. Primary windings are supplied with two orthogonal 20KHz alternating current to generate traveling wave magnetic field along x- and y- directions separately. Secondary windings output two signals whose phases are proportional to linear displacements of X and Y directions respectively. The structure and working principles of the sensor are proposed. Meanwhile, a sensor model is simulated to verify the feasibility of the working principle and a sensor prototype is fabricated for physical experiment. According to the analysis of experiment results, the measurement range is 140mm×140mm, and the maximum linearity in one pitch is 1%. The performance of sensor may be improved by optimizing the layout of primary and secondary windings and signal processing circuit.
Establishment of measuring coordinate system for large gears measurement by using gauge blocks
Shaokang Li, Zhongpeng Zheng, Linyan Wang
In this paper, the establishment of measuring coordinate system for large gears measurement was studied and discussed. The solution based on gauge blocks was proposed and the scheme was devised. The mathematical model for the establishment of measuring coordinate system was deduced. The main factors that influence the establishment precision of measuring coordinate system were studied, such as the alignment error of the initial position of the blocks, the installation eccentricity error of the gauge blocks and the error caused by the tilt of the rotary table and the different working lengths of the gauge blocks. The experiments were carried out on C40 gear measurement center under the condition of constant temperature and humidity. The experimental results showed the establishment precision of R axis of the measuring coordinate system was higher than that of T axis of the measuring coordinate system. When the working lengths of the gauge blocks were within 300mm, the measuring coordinate precisions of R axis and T axis were less than 2.5 μ m and 4 μ m, respectively, which could meet the requirement of the medium precision large gears measurement.
Equivalent thin film model with complex refractive index of resonant micromesh
Yongmeng Liu, Xv Liu , Zelin Li, et al.
Resonant micromesh with a hexagonal periodic array of micrometer-sized circular apertures is an interesting alternative to non-resonant micromesh and has the potential for superior optical transmission, while providing adequate electromagnetic interference shielding for optical windows. This paper proposes an equivalent thin film model with complex refractive index for prediction of shielding effectiveness of resonant micromesh coating. Corrected equivalent reactance and sheet resistance are given considering the thickness and duty factor of resonant micromesh. And the effects on complex refractive index of resonant micromesh parameters are analyzed. The proposed equivalent thin film model can be used to evaluate shielding effectiveness of resonant micromesh coating for optical windows.
System design of lithium battery internal resistance measurement using LabVIEW
Cun Chang, Tianjian Wu, Wanfu Yang, et al.
Lithium battery internal resistance is an important reference index to evaluate lithium battery performance. Since the mechanism of lithium battery internal resistance is complex and changeable, it cannot be directly measured in a general way. In this paper, an orthogonal vector phase locked amplifier, which uses the AC injection method and adopts the virtual instrument technology, Labview, as the platform, is developed to alleviate noise influence and phase difference of the traditional analog phase locked amplifier. The experiment results show that the system can achieve real-time and on-line measurement of lithium battery internal resistance with considerable accuracy. The experiment results also indicate that the system can accurately measure the internal resistance at the milliohm level with a high level of confidence.