The concept of an adaptive aircraft wing, i.e., whose shape parameters such as camber, span-wise twist, and thickness can be varied to optimize the wing shape for various flight conditions, has been extensively studied by numerous researchers. While the aerodynamic benefits (in terms of increased lift/drag ratios, improved maneuverability, and delayed flow separation) have been analytically and experimentally established, the complexity and weight penalty of the designs and actuation using smart materials could potentially alleviate the shortcomings of prior designs, leading the way to a more practical `smart' adaptive wing which responds to changes in flight and environmental conditions by optimally modifying its shape. A summary of recent work in the area of adaptive wing concepts incorporating smart structures technologies is presented. Emphasis is placed on continuing research at Northrop Grumman under a United States Defense Advanced Research Projects Agency contract entitled `Smart Structures and Materials Development-Smart Wing,'. Limitations and potential benefits of adaptive wing designs, applications and advantages of smart material actuators and sensors, and results of recent tests are discussed. Recommendations for future work required to develop an operational smart adaptive wing are also outlined.

A method is being developed to employ TERFENOL to optimize the shapes of wings for minimum drag during transonic cruise. Potential advantages include enhanced UAV attack and surveillance capabilities through increased dash speed, longer loiter, and extended range as well as decreased fuel expenditures for transport aircraft. Two smart-wing concepts were compared: an adaptive wing with the capability to change the shape of the wing box and a smart trailing edge that modifies camber while maintaining a smooth upper surface. While the adaptive wing provides the most capability to change the structural shape to minimize shock- induced drag, when actuator- and structural-weight penalties were considered as well as reliability and maintenance, it was determined that the smart trailing edge is the better concept. Numerical optimization of a simplified smart trailing edge determined the optimum configuration and optimum deflections for minimum drag. The system has the potential to extend the range of a small-fuselage large-wing UAV bomber by 9% and increase its loiter time by 11%. Magnetic and electronic design improvements to the TERFENOL linear-wave motor have been identified that will enable us to miniaturized it for UAV applications while doubling its actuation force and speed, and halving its power.

To verify the predicted benefits of the smart wing concept, two 16% scale wind tunnel models, one conventional and the other incorporating smart wing design features, were designed, fabricated and tested. Meticulous design of the two models was essential to: (1) ensure the required factor of safety of four for operation in the NASA Langley TDT wind tunnel, (2) efficiently integrate the smart actuation systems, (3) quantify the performance improvements, and (4) facilitate eventual scale-up to operational aircraft. Significant challenges were encountered in designing the attachment of the shape memory alloy control surfaces to the wing box, integration of the SMA torque tube in the wing structure, and development of control mechanisms to protect the model and the tunnel in the event of failure of the smart systems. In this paper, detailed design of the two models are presented. First, dynamic scaling of the models based on the geometry and structural details of the full- scale aircraft is presented. Next, results of the stress, divergence and flutter analyses are summarized. Finally some of the challenges of integrating the smart actuators with the model are highlighted.

Shape Memory Effect TiNi torque tubes were fabricated, tested and installed to supply 2500 in.lbs and 500 in.lbs of torque for inboard and outboard sections, respectively, of the DARPA smart wing wind tunnel model. Structural connections to the tubes were designed so that the entire assembly would fit within the interior of the wing, whose maximum dimensions of depth ranged from 1.125' to 0.375', depending on the position along the wing span. The torque tubes themselves were made by the gun drilling a TiNi ingot and ElectroSpark Discharge Machining to the required dimensions, which were calculated from a simple model described in a previous paper. The torque tubes were placed into the wing and twist deflections were measured. Deflections on the wing were measured at 1.3 degree(s), which provided a significant increase (approximately 8%) in the wing rolling moment.

The use of smart materials technologies can provide unique capabilities in improving aircraft aerodynamic performance. Northrop Grumman built and tested a 16% scale semi-span wind tunnel model of the F/A-18 E/F for the on-going DARPA/WL Smart Materials and Structures-Smart Wing Program. Aerodynamic performance gains to be validated included increase in the lift to drag ratio, increased pitching moment (C_m), increased rolling moment (C_l) and improved pressure distribution. These performance gains were obtained using hingeless, contoured trailing edge control surfaces with embedded shape memory alloy (SMA) wires and spanwise wing twist via a SMA torque tube and are compared to a conventional wind tunnel model with hinged control surfaces. This paper presents an overview of the results from the first wind tunnel test performed at the NASA Langley's 16 ft Transonic Dynamic Tunnel. Among the benefits demonstrated are 8 - 12% increase in rolling moment due to wing twist, a 10 - 15% increase in rolling moment due to contoured aileron, and approximately 8% increase in lift due to contoured flap, and improved pressure distribution due to trailing edge control surface contouring.

The development and testing of foam-PVDF smart skin designed for aircraft interior noise control are discussed. The smart skin is designed to reduce sound by the action of the passive absorption of the foam (which is effective at higher frequencies) and the active input of a PVDF element driven by an oscillating electrical input (which is effective at lower frequencies). The device consists of cylindrically curved PVDF piezoelectric film embedded in partially reticulated polyurethane acoustic foam. For performance testing, the foam-PVDF smart skin is mounted in the cockpit of a Cessna Citation III fuselage. Each smart foam element controls the effective acoustic source of individual fuselage panels. The fuselage crown panels are excited with a speaker located on the outside of the cockpit. A MIMO feedforward LMS controller is implemented to minimize the error sensor signals provided by microphones in the close proximity of the active elements under band-limited random excitation. The use of two different reference signals, i.e. the voltage sent to the speaker (disturbance) and the signal from an accelerometer directly mounted on the fuselage (more realistic in practice), are compared in terms of the interior noise attenuation achieved. The potential of the smart foam-PVDF skin for reducing interior noise is demonstrated.

A 1/6-scale F-18 wind-tunnel model was tested in the Transonic Dynamics Tunnel at the NASA Langley Research Center as part of the Actively Controlled Response Of Buffet Affected Tails program to assess the use of active controls in reducing vertical tail buffeting. The starboard vertical tail was equipped with an active rudder and the port vertical tail was equipped with piezoelectric actuators. The tunnel conditions were atmospheric air at a dynamic pressure of 14 psf. By using single-input-single-output control laws at gains well below the physical limits of the actuators, the power spectral density of the root strains at the frequency of the first bending mode of the vertical tail was reduced by as much as 60 percent up to angles of attack of 37 degrees. Root mean square values of root strain were reduced by as much as 19 percent. Buffeting alleviation results when using the rudder are presented for comparison. Stability margins indicate that a constant gain setting in the control law may be used throughout the range of angle of attack tested.

Helicopter design is limited by the compromise inherent in meeting hover and forward flight requirements, and the unsteady environment encountered in forward flight. Active control of helicopter rotors using smart material, in-blade actuation can overcome these barriers and provide substantial reductions in noise and vibrations and improved performance. The present study covers the blade/actuator integration and actuator development for a full scale system to demonstrate active control of noise and vibrations as well as inflight blade tracking on the MD Explorer helicopter. A piezoelectric multilayer stack actuator, driving a trailing edge flap, is used for active control. A shape memory alloy torsion actuator, driving a trailing edge trim tab, is used for inflight tracking. Overall, this DARPA sponsored program entails the design, development, and fabrication of the full scale active control rotor system. If successful, an entry in the NASA Ames 40 X 80 foot wind tunnel and flight tests are planned for a follow on program.

This paper describes various concepts that might be used for controlling the flight of hypersonic vehicles using smart and unconventional structures. These concepts are developed by looking at basic ways of generating maneuvering forces on a hypersonic vehicle, then examining how those forces might be controlled using smart or unconventional structures. The list of maneuvering concepts was made as complete as possible by including both conventional and novel means of controlling a hypersonic vehicle regardless of their suitability for present day smart materials. A preliminary comparison is made to select the more promising concepts based on novelty, amount of maneuvering force generated, and technical hurdles which must be overcome. A comprehensive list of references is included to better describe the various maneuvering concepts.

Mitigation of the undesirable effects of trailing vortex wakes has been a long-standing priority for both reduction of submarine wake signature and alleviation of aircraft vortex wake hazard. A recent study established the feasibility of using relatively weak, secondary vortices with carefully selected unsteady amplitude and phasing to accelerate the breakup of the primary vortex system of a lifting surface, a technique denoted `vortex leveraging'. This paper will summarize progress on the development of SMA-actuated devices for implementing vortex leveraging for hydrodynamic applications. The methods being applied to the hydrodynamic design of these deformable Smart Vortex Leveraging Tabs (SVLTs) will be described, and the results of a preliminary assessment of SVLT performance in achieving wake breakup will be presented. Also, previous work on the design and testing of deformable control surfaces actuated via embedded SMA agonist wires will be reviewed and the design process being employed in the present applications will be discussed. Finally, the plans for near-term computational and experimental work to validate the use of SMA-driven devices for the wake mitigation task will be briefly outlined.

The characteristics of cantilever piezoelectric actuators are investigated both theoretically and experimentally. The type of actuators considered consist of a single sheet of piezoceramic material bounded to a shim--termed a `unimorph' design. A theoretical model, based on beam theory, is developed to predict the static and dynamic behavior of the actuator. The model predictions compare favorably to measurements of the actuator transfer function. A sample application to noise reduction of flow-induced cavity oscillations at low subsonic speeds is described. Use of the actuators in an open-loop control system resulted in 18 and 25 dB attenuation in the broadband and primary tone sound pressure levels, respectively.

New 1-3 piezocomposite materials have been investigated for potential underwater smart skin applications. PZT-5H was used as the ceramic phase in the composite whereas two types of polyurethane resins of different hardness were used as the matrix of the composite in order to assess the effect of the compliance of the host matrix material. The effect of a thin, rigid cover plate was also examined in this study. Measurement results from in-water acoustical evaluation of a series of 25.4 cm X 25.4 cm panels of these 1-3 composite samples are presented. The transmitting voltage response, free-field voltage sensitivity and directivity pattern of each panel were shown as a function of frequency. The effect of underwater explosive shock was also investigated, and it was found that neither the acoustical properties nor the mechanical integrity of the panel structure was adversely affected. These results demonstrated that these new 1-3 piezocomposites are potentially useful for smart skin applications in underwater acoustics.

For smart materials to become widely used in aerospace applications, a number of stringent requirements concerning their performance in various operating environments have to be satisfied. Laboratory scale test procedures have been developed to assess the suitability of piezoceramic/carbon fiber reinforced plastic composites with embedded as well as surface-bonded actuators for active vibration and shape control of aerospace structures. In experimental and analytical investigations various composite configurations were evaluated with respect to the resulting actuation capability as well as the compatibility with various operation conditions.

Successful use of smart materials or derives requires an understanding of the performance characteristics of the combination of smart and passive components. Synergistic material and geometric interactions often produce complex performance characteristics. Computational simulations which explicitly include material components are often required for accurate performance predictions. A performance evaluation is completed for a multilayered composite panel designed for acoustic suppression. The panel contains multiple pistons. Each piston consists of an array of actuators which support an alumina head mass plate. The alumina plate is designed to deliver uniform displacement with movement of the actuators. The panel design features a graphite composite box which functions as both a base plate for the active panel and as housing for the power electronics required for plate activation. ABAQUS, a commercial finite element code, is used for deformation and structural integrity analyses. Performance issues addressed are: (1)Final surface displacement and flatness of the top surface. (2) Loss of actuator authority resulting from intermediate layers of passive materials. (3) Changes in performance due to changes in interfacial layer characteristics. (4) Changes in performance due to changes in operating temperatures. (5) Internal stress and strain levels in each of the component materials.

The objective of this work is twofold. First, the influence of confined vibrations on the sensor and actuator optimization is determined and evaluated. Second, a preliminary design methodology to incorporate confined vibration response in the design stage of the sensor/actuator arrays used in smart structures is introduced. In this paper, the influence of confinement on the performance and optimal location of the sensor/actuator sets is evaluated based on two different optimization criteria. The first criterion is based on a specified performance index related to the observability and controllability grammians of the sensors and actuators, respectively. The second criterion is based on the energy dissipated through collocated sensor/actuator sets. Three types of structural components, beam, plate, and cylinder, are evaluated. Theoretical results are verified by laboratory tests conducted on all three structural components. The preliminary results of this work clearly show that vibrational confinement has a significant effect on the performance and position optimization of sensors and actuators. The proposed modified optimization procedure and design methodology are proven to be effective in addressing certain issues. It is concluded that the unintentional occurrence of confined vibrations may be detrimental to vibration control systems. On the other hand, one may take advantage of the intentional presence of confined vibrations in a structure to reduce the error in the optimal locations of sensors and actuators and optimize their performance by focusing the control effort on the confined areas.

An integrated and automated smart structures approach for in situ damage assessment has been implemented and evaluated in a laboratory environment for health monitoring of a realistic aerospace structural component. This approach, called Active Damage Interrogation (ADI), utilizes an array of piezoelectric transducers attached to or embedded within the structure for both actuation and sensing. The ADI system, which is model independent, actively interrogates the structure through broadband excitation of multiple actuators across the desired frequency range. Statistical analysis of the changes in transfer functions between actuator/sensor pairs is used to detect, localize, and assess the severity of damage in the structure. This paper presents the overall concept of the ADI system and provides experimental results of damage assessment studies conducted for a composite structural component of the MD-900 Explorer helicopter rotor system. The potential advantages of this approach include simplicity (no need for a model), sensitivity, and low cost implementation. The results obtained thus far indicate considerably promise for integrated structural health monitoring of aerospace vehicles, leading to the practice of condition-based maintenance and consequent reduction in life cycle costs.

The NASA/McDonnell Douglas Delta Clipper-Experimental Advanced (DC-XA) re-usable rocket program included the development of a Structural Health Monitoring System (SHMS) to acquire and present structural health information to the DC-XA flight team in near-real-time. The SHMS was successfully demonstrated in 1996 during flight tests of the DC-XA at White Sands Missile Range where it was used to support rapid vehicle turnaround and to provide an improved understanding of the DC-XA's advanced structural components, including a composite liquid hydrogen tank, composite interbank, and aluminum-lithium liquid oxygen tank. Development of the DC-XA SHMS required the selection and integration of fiberoptic and conventional sensors, development of an advanced, multi-channel fiberoptic sensor demodulator, investigation of sensor installation methods, and the development of structural health data analysis and visualization algorithms. This paper describes the design, implementation, and operation of the DC-XA SHMS. Results and conclusions from ground and flight tests are presented.

Embedding sensors in structural composites has been a topic of research in recent years. Embedded sensors can be used to monitor and optimize the manufacturing process, to monitor performance during use, and for structural health monitoring in high-performance applications. To date, optical fiber sensors have been the principal sensing technique for these applications. There are well-known problems with optical fiber sensors, including high manufacturing costs, fragility, the need to provide ingress and egress from the structure, and the interdependence of strain and temperature measurements. The US Naval Research Laboratory is funding a multi-disciplinary team to develop micro-machined sensors and an associated remote-querying capability to allow self- contained microsensors to be embedded in a composite structure and queried using methods that do not require physical connections. The sensors are to be left in place for the lifetime of the structure, are powered by the querying apparatus, and require no penetrations through the surface of the structure. Part of this work included studying electromagnetic propagation into graphite-epoxy (conductive) composites. A key part of this research has been the development of embeddable antennae that can operate within a conductive composite matrix with the efficiency required to both absorb power for the circuitry and to transmit and receive data. This paper describes the integrated approach taken to realize the goal of an interrogatable strain rosette that is embedded 0.25' into a graphite composite plate. Aspects of the sensors, the transponder, and the antenna are also covered.

This paper discusses efforts related to the development and evaluation of smart bolts and fasteners. The work has been directed at meeting the high-strength application requirements for the aircraft industry and selected applications within the construction industry. The fasteners are fabricated from metastable austenitic steel materials which progressively and irreversibly transform from a non- ferromagnetic, austenitic parent phase to a thermodynamically stable, ferromagnetic martensitic phase as a function of applied strain. Thus, the ferromagnetic response of an in-place fastener can be used to indicate the degree of inelastic deformation, i.e., the peak, post-yield, strain, that it has experienced up to that time. A combination of alloy chemistry and thermomechanical treatment was utilized to produce the desired martensitic transformation vs. peak strain behavior. A discussion of the smart materials behavior of the fasteners will be followed by a presentation of recent test results which illustrate the structural bolt monitoring technique with some possible applications.

Civil structural monitoring by optical fiber sensors, require the development of reliable sensors that can be embedded or surface mounted in concrete, mortars, steel, timber and other construction materials as well as in rocks, soils and road pavements. These sensors should be rapid and simple to install in order to avoid any interference with the building site schedule and not to require specialized operators to accomplish the task. The sensors have to be rugged enough to withstand the harsh conditions typically found in civil engineering including, dust, moisture, shocks, EM disturbances and unskilled workman. It is also desirable that the instrumentation survives for tens of years in order to allow a constant monitoring of the structure aging. This contribution presents the results of a four-year effort to develop, test and industrially produce a palette of sensors responding to the above requirements and adapted to different applications and host materials. These sensors include a small version (length up to 2 m) adapted for embedding in mortars, grout and glues, an intermediate version of length between 20 cm and 6 m adapted to direct concrete embedding or surface installation and a long version adapted to measure large deformations (up to 2%) over length up to 30 m and especially adapted for geostructures monitoring.

Despite the attractive mechanical properties of polymer matrix composites, which include high specific stiffness and strength, their use has been limited in many cost-sensitive applications due to high manufacturing costs. Since the processing of these materials is a major component of the cost of the finished product, the development of adaptive systems using feedback sensors for control of the composite cure process will accelerate the adoption of composites technology for diverse commercial and industrial applications. We present an embeddable fiber optic sensor for monitoring of the cure of thermoset resins by measuring the rheology of the polymer. By coupling a fiber optic strain sensor to an actuator, it is possible to realize a miniature dynamic mechanical analysis system. If the sensor is immersed in a curing thermoset resin, and a time-varying excitation is applied to the actuator, the sensor can be made to vibrate harmonically. By comparing the phase of the excitation to the phase of the resulting strain as detected by the strain sensor, it is possible to derive the loss tangent of the resin, which can be related to the degree of cure of the resin. After the resin hardens, the embedded sensor may be used as a conventional fiber optic strain gage to measure in-service strains.

This paper verifies the performance of the active microvibration control system using the piezoelectric actuators with a table of length 3 m, width 1.8 m and weight 4,000 kg, which was applied to the large-scale semiconductor manufacturing equipment whose microlithographic accuracy was actually degraded due to the constant vibration. The mounted equipment was the integral-design semiconductor manufacturing equipment weighing 2,600 kg. The controller was designed by the method dependent on the coprime factor plant model in the preceding study for preventing the elastic vibration of the equipment and table from causing the spillover phenomena of the control system. For frequency forming algorithm, the model matching method and H^(infinity ) method were employed. As a result of this system's application, the microlithographic accuracy of the manufacturing equipment could be recovered.

Some machining processes, such as boring, have been historically limited by excessive bar vibration, often resulting in poor surface finish and reduced tool life. A unique boring bar system has been developed to suppress bar vibration, or chatter, during machining using active control technology. Metal cutting test programs have shown proven, repeatable performance on hard-to-cut, aircraft industry high-temperature nickel alloys as well as more easily cut carbon steels. Critical bar length-to-diameter (L/D) ratios, depths-of-cuts, feed rates and cutting speeds far exceed those attainable from the best available passively-damped boring bars. This industry-ready system consists of three principle subsystems: active clamp, instrumented bar, and control electronics. The active clamp is a lathe-mountable body capable of supporting bars of varying sizes and articulating them in orthogonal directions from the base of the bar shank. The instrumented bar consists of a steel shank, standard insert head and imbedded accelerometers. Wire harnesses from both the bar and clamp connect to control electronics comprised of highly-efficient switched- capacitor amplifiers that drive the piezoelectric actuators, sensor signal conditioning, a PC-based program manager and two 32-bit floating-point DSPs. The program manager code runs on the host PC and distributes system identification and control functions to the two DSPs. All real-time signal processing is based on the principles of adaptive filter minimization. For the described system, cutting performance has extended existing chatter thresholds (cutting parameter combinations) for nickel alloys by as much as 400% while maintaining precision surface finish on the machined part. Bar L/D ratios as high as 11 have enabled deep boring operations on nickel workpieces that otherwise could not be performed free of chatter.

The use of active feedback compensation to mitigate cutting instabilities in an advanced milling machine is discussed in this paper. A linear structural model delineating dynamics significant to the onset of cutting instabilities was combined with a nonlinear cutting model to form a dynamic depiction of an existing milling machine. The model was validated with experimental data. Modifications made to an existing machine model were used to predict alterations in dynamics due to the integration of active feedback compensation. From simulations, subcomponent requirements were evaluated and cutting enhancements were predicted. Active compensation was shown to enable more than double the metal removal rate over conventional milling machines.

The development and initial evaluation of a prototype boring bar feature active vibration control for increased chatter immunity is described. The significance of active damping both normal and tangential to the workpiece surface is evaluated, indicating the need for two axis control to ensure adequate performance over expected variations in tool mounting procedures. The prototype tool features a commercially available boring bar modified to accommodate four PZT stack actuators for two axis bending control. Measured closed-loop dynamics are combined with a computer model of the boring process to simulate increased metal removal rate and improved workpiece surface finish through application of feedback control.

Chatter in machining processes is one of the most important factors limiting production rates. In order to suppress machine tool chatter during orthogonal cutting processes, a real time active chatter controller is designed and implemented that is able to adopt to the continuously changing machining parameters. An electro-hydraulic servo system is used to control the movement of the cutting tool. The cutting force, workpiece acceleration, and tool displacement are measured in real time. The transfer function of the workpiece is estimated by using the cutting force and the acceleration of the workpiece. All the digital signal acquisition and processing tasks are performed by a digital signal processor (MicroStar DAP3200a/415). The digital controller is designed such that the servo/actuator dynamics is adjusted to match the workpiece dynamics to suppress chatter. To make the controller adaptive to the changing dynamics of the workpiece, a recursive least square technique is used to identify the workpiece dynamics in real time. The estimated workpiece dynamics parameters are then used in the digital controller to calculate a new servo output, thus controlling the tool movement. Simulations show that chatter can be suppressed successfully by using this method. Experiments agree well with simulations.

Vibration control of flexible structures composed by plates and shells became a serious problem in the last decade. In this paper the noise problem of modern washers is analyzed and a general investigation on the use of thin in-plane piezoelectric actuators and sensors to accomplish active vibration suppression in the lateral panel of an horizontal axis washing machine is performed. Experimental modal identification and validation of a finite element model of the panel is performed. Very high modal density and very low damping and close zero-pole pairs in proximity of each resonance are displayed, making control not an easy task. A digital control strategy is applied in view of a future general application to mass production home-appliance industry taking into consideration the real excitation conditions of a washing machine. The paper describes the experimental apparatus and real-time procedures implemented and discusses results.

A new piezoelectric drive mechanism has been developed for optical translation in space-based spectrometer systems. The mechanism utilizes a stack of RAINBOW high displacement piezoelectric actuators to move optical components weighing less than 250 grams through a one centimeter travel. The mechanism uses the direct motion of the piezoelectric devices, stacked such that the displacement of the individual RAINBOW actuators is additive. A prototype device has been built which utilizes 21 RAINBOWs to accomplish the necessary travel. The mechanism weighs approximately 0.6 kilograms and uses less than 2 Watts of power at a scanning frequency of 0.5 Hertz, significantly less power than that required by state-of-the-art motor systems.

Optical fiber sensors can be used to monitor many parameters such as strain on modern high-temperature alloys during cyclic loading and pressure in composite manufacturing processes. Presented are the application and operation of several fiber optic sensors based on the extrinsic Fabry- Perot interferometer technique. The results from strain measurements demonstrated that the fiber optic strain sensors are able to withstand extreme temperature [ambient to 2070 degree(s)F (1132 degree(s)C)] while maintaining a high level of performance. The capabilities of the fiber optic sensors make it possible to monitor many material property changes and measureands.

A new technique for recoating optical fiber with a polyimide jacket is demonstrated. Single layer coatings of 7 micrometers , and double layers of 15 micrometers have been applied to 125 micrometers fiber. The coatings are uniform and concentric, and can be applied with no loss of original fiber strength. The technique accommodates multiple fiber diameters without the need for interchanging parts.

Magnetostriction means change of shape of material in the presence of a magnetic field, with the degree of this change proportional to the strength of the magnetic field. The magnetostrictive TERFENOL-D expands in length and contracts diametrically, thereby conserving the volume of an essentially incompressible material. The magnetostrictive effect generates the elastic forces in accordance with a generalized Hooke's law. The principle of magnetostriction of TERFENOL-D can be used in the development of linear motion devices. In an elastic wave type linear motion, the `smart material' TERFENOL-D is enclosed with an interference fit in a stator tube which is enclosed in a series of coils that generate the magnetic field when power is applied. The pattern of activation of these fields is controlled by a digital controller which will enable the TERFENOL-D `smart material' to move inside the stator tube like a worm. During this motion, the TERFENOL-D rod can push and pull loads. When power is turned off this device will lock itself in the stator tube without any slippage. Some of the important applications are nano positioning, aircraft wing warping, airplane/helicopter flap/tab positioning and control, automobile brakes, controlled delivery of fluids, and space applications.

A magnetostrictive reaction mass actuator possessing a large force to weight ratio has recently been developed at SatCon Technology Corporation. Achieving such high performance requires adequate modeling of this multidisciplinary device. The developed models allow performance optimization to be accomplished through parameter selection and control design. At the 1996 smart materials conference, the modeling and design issues associated with this actuator were discussed. Since that time, additional experiments and optimization have been performed that validate the proposed modeling. These experiments include validation of the thermal modeling and dynamic model validation through control experimentation. In addition to these results, a discussion of the trade-offs in terms of eddy current, controller, and thermal requirements, will be presented.

For many current applications, hydraulic power is still the preferred method of gaining mechanical advantage. However, in many of these applications, this power comes with the penalties of high weight, size, cost, and maintenance due to the system's distributed nature and redundancy requirements. A high authority smart material Integrated Electric Actuator (IEA) is a modular, self-contained linear motion device that is capable of producing dynamic output strokes similar to those of hydraulic actuators yet at significantly reduced weight and volume. It provides system simplification and miniaturization. This actuator concept has many innovative features, including a TERFENOL-D-based pump, TERFENOL-D- based active valves, control algorithms, a displacement amplification unit and integrated, unitized packaging. The IEA needs only electrical power and a control command signal as inputs to provide high authority, high response rate actuation. This approach is directly compatible with distributed control strategies. Aircraft control, automotive brakes and fuel injection, and fluid power delivery are just some examples of the IEA's pervasive applications in aerospace, defense and commercial systems.

A general need exists for inexpensive finite-area transducer arrays which intrinsically combine acoustic or vibration sensing with area actuation. Such combination transducers are particularly needed in active sound and vibration control and smart-materials applications. Commercial areas of interest include advanced underwater, aerospace or robotic-sensing applications. To be economically attractive they must be relatively simple to manufacture from reasonable cost materials. One promising new technology for such applications is injection-molded 1-3 composite piezo- ceramics, pioneered by Material Systems Inc. This transducer material is well suited for use as the low-cost actuator component of such a smart actuator. The challenge of this study was to design an inexpensive accelerometer which could be injection molded along with the actuator as an interspersed array. This paper describes a monolithic accelerometer which is suitable for fabrication by injection-molding as an integrated co-formed actuator component. Experimental results are presented for actuator/accelerometer arrays and issues related to the design and use of accelerometers in close proximity to an actuator are discussed.

Advanced Cerametrics Inc. has conceived of and developed the Viscous-Suspension-Spinning Process (VSSP) to produce continuous fine filaments of nearly any powdered ceramic materials. VSSP lead zirconate titanate (PZT) fiber tows with 100 and 790 filaments have been spun in continuous lengths exceeding 1700 meters. Sintered PZT filaments typically are 10 - 25 microns in diameter and have moderate flexibility. Prior to carrier burnout and sintering, VSSP PZT fibers can be formed into 2D and 3D shapes using conventional textile and composite forming processes. While the extension of PZT is on the order of 20 microns per linear inch, a woven, wound or braided structure can contain very long lengths of PZT fiber and generate comparatively large output strokes from relatively small volumes. These structures are intended for applications such as bipolar actuators for fiber optic assembly and repair, vibration and noise damping for aircraft, rotorcraft, automobiles and home applications, vibration generators and ultrasonic transducers for medical and industrial imaging. Fiber and component cost savings over current technologies, such as the `dice-and-fill' method for transducer production, and the range of unique structures possible with continuous VSSP PZT fiber are discussed. Recent results have yielded 1-3 type composites (25 vol% PZT) with d₃₃ equals 340 pC/N, K equals 470, and g₃₃ equals 80 mV/N, k_t equals 0.54, k_p equals 0.19, d_h equals 50.1pC/N and g_h equals 13 mV/N.

Stacks of RAINBOW high-displacement actuators are currently under consideration for use in scanning mechanisms capable of providing controlled travels on the order of 1 cm. In this work, actuator stacks were produced by stacking PZT-5A and PZT-5H RAINBOWs in a clamshell configuration. The displacement properties of the RAINBOW stacks were then evaluated as a function of applied electric field, static load, number of actuators in the stack, and diameter of the actuators. The displacement properties of the stacks were found to increase nearly proportionately to the number of actuators in the stack, with the PZT-5A RAINBOW stacks generating one and half to two times the displacement of the PZT-5H stacks at +/- 8 and +/- 16 kV/cm.

In this paper we report on the development of a high frequency switching amplifier for electrostrictive actuators. This amplifier is specifically designed for the capacitive loads that electrostrictive actuator present to them. An integrated nonlinear model of the actuator and the electronics is also developed. It is shown that one source of distortion in the actuator velocity is the nonlinear field to polarization relationship. The amplifier reduces the impact of this nonlinearity by controlling the current entering the actuator instead of the voltage across the actuator. Another major source of the distortion is caused by the quadratic relationship between polarization and strain in the electrostrictive material. The paper develops a new control scheme for the amplifier which significantly improves the linearity of the overall amplifier/actuator combination. Both experimental and simulation results of the Smart Material are reported.

This paper describes drive amplifier development for large, high voltage piezo actuators. Piezo actuation's highly capacitive nature and its influence on drive amplifiers is discussed. A switching amplifier driving an inductor in series with the piezo material and controlled by an appropriate control law can drive piezo actuators. Since large piezo actuators tend toward higher voltages, a multi- level topology is described that allows drive amplifiers to provide voltages higher than solid state switching device ratings. High efficiency piezo drive amplifiers must accommodate energy stored in the piezo material. A topology is described that actively stores the capacitative energy, thus reducing the size, weight and power consumption of the electronics system. Test results are presented for a developmental 1.2 KV, piezo drive amplifier that can drive a 0.6 (mu) F piezo actuator at 100 Hz. This work done in conjunction with Smart Structures for Rotor Craft Consortium in support of AFORS/DARPA.

The primary objective of this work is to determine to what extent vibration confinement can be used to enhance conventional active vibration control methods. By using a fixed-pinned beam with an attached elastic component, this objective was accomplished by applying active control to suppress vibrations in the component while the beam is under confined and unconfined conditions. Confinement was achieved by passively tuning linear and torsional stiffnesses of an elastic intermediate support, which alter the system's mode shapes. Four different active control methods were studied, including optimal control, adaptive feedforward cancellation, direct velocity feedback, and active isolation. The results show that passive confinement can significantly improve the performance of all four vibration control methods while simultaneously reducing their power requirements.

This paper compares three actuation schemes to attenuate turbulent boundary layer sound radiated into the cabin through an aircraft fuselage. Two actuation schemes make use of piezoelectric materials and are compared with conventional electromagnetic voice coil actuation. Volume displacement of electromechanical actuators is typically proportional to either volts or amperes. Comparison between actuators can be problematic since drive impedances vary greatly. This paper presents a reliable method to compare actuator power using a transfer function of volume per square root of power. This power consumption curve is useful in direct comparison of actuator stroke capability and spacing requirements.

The Smart Structures for Rotor Control (SSRC) is a consortium under the overall Defense Advanced Research Projects Agency Smart Structures program. The program is administered by the Air Force Office of Scientific Research, with Boeing Seattle as the consortium administrator, and MIT, PSU and Boeing Helicopters as the other principal consortium members. The SSRC objectives are to research smart structure methods to achieve reduced rotorcraft vibration, reduced acoustic noise, and increased performance (i.e., payload). The SSRC program includes dynamic piezoelectric actuation of flaps on each rotor, distributed dynamic piezo actuation of the rotor twist, and quasi-static rotor twist control using shape memory alloys. Supporting these actuation approaches are system studies, rotorcraft structural and aero-elastic analyses, piezoelectric materials development, electronics development, and health monitoring studies.

Piezocomposite SmartPanels^TM, consisting of 1-3 actuators and pressure sensors and net-shape-molded PZT accelerometers in a large area low profile panel, have been fabricated at Materials Systems Inc. and evaluated at the Naval Research Laboratory. Single layer and two-layer 100 X 100 mm SmartPanels have been tested for sensor sensitivities, actuator authority, surface displacement uniformity, and sensor-actuator coupling. Multilayer GRP circuits boards are used both as stiff faceplates and to provide electrical connections and ground planes. The SmartPanel technology has recently been scaled up to 250 X 250 mm devices. SmartPanels draw upon PZT (lead zirconate titanate) ceramic injection molding technology, which is used to produce cost-effective and robust 1-3 piezoelectric ceramic-polymer composite materials. The 1-3 materials are used extensively for SonoPanel^TM transducers in a number of sensor and actuator applications. SonoPanels have been qualified for US Navy applications, based on successful completion of pressure and shock tests, and are currently being scaled up from 250 X 250 mm to 750 X 750 mm panels. Several applications for SmartPanels and SonoPanels are described, including conformable transducers, multielement arrays, pressure sensors, and velocity sensors.

Methods for reducing weight, size, and complexity of flight systems are especially desirable in aerospace vehicles. To answer the challenge the Delta Clipper eXperimental Advanced program has developed numerous new technologies including a Bragg-grating based fiberoptic system used for measuring strain on the vehicle's liquid hydrogen fuel tank. This is one of the first known aerospace applications of a practical fiberoptic strain measurement system. The system utilizes four parallel channels of serially multiplexed fiberoptic sensors. Its basic advantages include reduced signal cable complexity and weight, wide temperature operation, efficient use of wavelength bandwidth and power, and potentially small signal conditioner size. This paper presents the design and development of the system as well as performance data and experimental results. The presentation will also discuss advantages over conventional sensor systems, the system's capabilities and drawbacks, and next generation improvements.

A new type fiber sensor with two wavelengths is presented in this paper. The measurement range of surface roughness is greatly extended. Through the analysis of the average optical transfer function, we calculated the upper limit of the surface rms roughness. The sensor is suited for manufacturing process of metal components that have large measurement range of surface roughness, particularly those with complicated shapes.

Ultra-precision machining to sub-micrometer depths is shown to be a threshold area of work requiring a combination of the best of materials, sensors, positioning devices and control strategies. In ultra-precision design, it is extremely likely that there will be few design options for selection. In the case of ultra fine tool feed, the piezoelectric actuator is a potential choice. Currently, European and Japanese tool manufacturers are investigating magnetostrictive actuators for this purpose. Both piezoelectric and magnetostrictive materials suffer from hysteresis type non-linearity, so that the output of such systems depends upon the previous input, and absolute positioning is only achievable with the aid of feedback control. This work compares several modern control techniques for the positioning of a tool post for ultra- precision machining of brittle materials (in the nanometric range), e.g., lead-lag filter, PI+D, PID+feedforward, and fuzzy logic/neural network. The performance of the micropositioning device using both piezoelectric and magnetostrictive (solid-state) actuators are assessed by means of simulation techniques. The performance results are compared with results obtained by other authors.

This article concerns the design and post-fabrication testing of a CMOS integrated circuit (IC) for the Remote- Queried Embedded Microsensor (RQEM) system. The IC may be coupled to capacitive microsensors to measure the output of the sensors, to digitize this measured output, and to condition and encode the digital data. Wireless transmission of the code to a commercial Radio Frequency Identification (RFID) system reader is implemented using Differential Phase Shift Keying of a low-frequency signal, which inductively couples the RQEM antenna coil to the receiving antenna of the RFID reader. The IC extracts its own operating power and digital clock signal from the interrogating signal, which is transmitted by the RFID reader. The IC uses switched- capacitor techniques for acquisition and for A/D conversion of data. A first-order Sigma-Delta ((Sigma) (Delta) ) A/D converter is used with an output transconductance amplifier (OTA) in the balancing integrator and the comparator. The same OTA is also used in the acquisition circuit, which is a sample-and-hold offset-free circuit. Several fabricated chips were tested with on-chip test capacitors, used to calibrate the IC's output.

Natural systems have evolved seamless electro-mechanical integration by exploiting intelligence and by developing multifunctional componentry. This philosophy also holds promise for creating smarter vehicles because the limitations of electronics integration and demand for new features will, sooner or later, clash with vehicle space and cost constraints. Meeting this need to maximize `functional density' and develop smarter vehicles will, however, require further improvements in several of the enabling technologies, such as digital signal processing, micro- electro-mechanical systems and smart materials.