This paper proposes a semiactive controllable magneto-rheological(MR) engine mount for vibration control of a passenger vehicle. A mixed-mode type MR engine mount is devised and incorporated with a full-vehicle model. The governing equation of the model is derived by considering engine excitation force and a semiactive skyhook controller is designed to attenuate unwanted vibrations. The controller is implemented through a hardware-in-the-loop simulation(HILS) and control responses such as acceleration at the driver's position are evaluated in time and frequency domains.

In this paper, a set of MR valves is implemented within a Wheatstone bridge hydraulic power circuit to drive a hydraulic actuator using a gear pump. A compact hydraulic power actuation system is developed that is comprised of a Wheatstone bridge network of magnetorheological (MR) valves with a conventional hydraulic cylinder. There are many advantages of using MR valves in hydraulic actuation systems, including: valves have no moving parts, eliminating the complexity and durability issues in conventional mechanical valves. In such a system MR fluid is used as the hydraulic fluid. A constant volume pump is used to pressurize the MR fluid which eliminates the effect of fluid compliance to a large degree. If a change in direction is required, the flow through each of the valves in the Wheatstone bridge can be controlled smoothly via changing the applied magnetic field. A magnetic field analysis is conducted to design a high-efficiency compact MR valve. The behavior and performance of the MR valve is expressed in terms of non-dimensional parameters. The performance of the hydraulic actuator system with Wheatstone bridge network of MR valves is derived using three different constitutive models of the MR fluid: an idealized model (infinite yield stress), a Bingham-plastic model, and a biviscous model. The analytical system efficiency in each case is compared and departures from ideal behavior, that is, a valve with infinite blocking pressure, are recognized.

This paper demonstrates the feasibility of using PZT thin films as sensors and actuators for smart structures and MEMS applications. The feasibility study includes specimen preparation and vibration testing. The specimen consists of a substrate, a PZT thin film, and a bulk PZT. The substrate is a doped conductive silicon wafer. The PZT thin film is fabricated through sol-gel dip-coating process with added PZT nano-particles to prevent homogeneous crystallization. The thickness of the PZT thin film is about 5 micrometers and the capacitance varies from 90 to 130 pF. The bulk PZT, which is commercially available, serves as a reference sensor and actuator for the specimen. The dimensions of the specimen are 2.7 cmx 1.4 cm . 0.4 mm. The vibration testing consists of sensor testing and actuator testing. In the sensor testing, the PZT thin film serves as a sensor, while the bulk PZT serves as an actuator. The specimen is cantilevered, and harmonic excitations are generated from 500 Hz to 500 kHz. A laser Doppler vibrometer also monitors the specimen vibration in addition to the PZT thin-film sensor. As a sensor, the PZT thin film produces legible harmonic output voltage ranging from 0.5 mV to 200 mV. In the actuator testing, the PZT thin film serves as an actuator, while the bulk PZT serves as a sensor. Similarly, harmonic excitations are generated from 100 Hz to 1 MHz. Depending on the excitation frequency, actuation voltage of the PZT thin film ranging from 0.1V to 100 V results in legible voltage response form the bulk PZT. Also, the PZT thin film experiences significant aging when it serves as an actuator. This might result from fatigue or accumulated defects of the PZT thin film. Finally, the PZT thin film can become nonlinear in sensing and actuation, when the excitation voltage is too high.

A comprehensive experimental characterization of single crystal, martensite, NiMnGa rods is the current subject of study. Preliminary actuator force-displacement curves for DC magnetic fields up to 0.6 T in the static regime have been developed. A peak static actuation force of 5.5N at 0.4 mm in was observed. The effects AC magnetic fields below magnetic saturation were also examined. The dynamic force-displacement characteristics of the NiMnGa alloy in the presence of mechanical preloads was studied. Dynamic testing at AC fields of 0.3 T yielded strains of up to 1.2% and dynamic loads of up to 7 N. A possible material dependence on strain-rate and was observed from the experimental dynamic stress-strain curves.

This paper describes new concepts proposed by the author to realize active and sensitive structural material systems. Two examples of multifunctional composites were fabricated and evaluated in this study as follows: (1) An active laminate of aluminum plate (works as muscle), epoxy film (as insulator), unidirectional CFRP prepreg (as bone and blood vessel) and copper foil electrode (to apply voltage on CFRP) was made with an embedded optical fiber multiply fractured in the CFRP layer (works as nerve), of which curvature change could be effectively monitored with the fractured optical fiber. (2) A stainless steel fiber/aluminum active composite with embedded Ti oxide/Ti composite fiber was fabricated. The Ti oxide/Ti fiber could work as a sensor for temperature by removing a part of the oxide before embedment to make a metallic contact between the embedded titanium fiber and aluminum matrix to be able to generate thermal electromotive force, and also could work as a sensor for strain and as a heater for actuation. In the both cases, the outputs from their embedded sensors can be used to control their actuations.

In heat resisting steels, micro holes, called creep cavities, are formed at grain boundaries by long term use at high temperatures. These creep cavities grow along grain boundaries, form grain boundary cracks by linking up each other anc cause low ductility and premature fracture as shown in Fig. 1. Therefore long term creep rupture strength and ductilities chiefly depend upon the behavior of nucleation and growth of creep cavities. If the growth of creep cavities could be suppressed, creep rupture strength and ductilities should be improved remarkably. Present work is intended to propose a self-healing process for the cavitation, and improve the creep rupture properties by the self-healing. It is thought that chemical compound of BN precipitates at inside surface of creep cavity by addition of B and N to heat resisting steels. As the BN is very stable at high temperatures, the precipitation of BN at creep cavity surface is expected to suppress the creep cavity growth and bring about the healing effect on the cavitation.

Nature builds by 1) use of local, inexpensive, available often recycled materials which 2) are self-ordering or growing by attributes shared between the material and environment; 3) repair themselves, 4) sense and adapt to changes in the environment daily, seasonally, and yearly; 5) easily disintegrate and recycle back into the material sink when their usefulness is at an end; and 6) do not harm the environment, but perhaps enhance it or resolve problems.

We investigated a thermal nondestructive evaluation (NDE) technique based on thermography that uses optical fiber sensors to detect damage within a laminated graphite epoxy composite specimen. Two sets of composite samples were used for testing, one set had fiber optic sensors imbedded between the layers and the other set did not. Thermocouples were attached to the front and back surfaces of all coupons for comparison. Damage was initiated in the samples at various levels with a simulated impact system and damage was confirmed with X-ray. Results suggest that the thermal approach is more sensitive to damage than the X-ray evaluation used. The test apparatus in addition to the results obtained from both sets of samples are presented.

The paper presents a new application of a NDT based on vibrations measurements which has been developed by the authors and already tested for analyzing damages of many structural elements. The proposed method is based on the acquisition and comparison of Frequency Response Functions (FRFs) of the monitored structure before and after a damage occurred. Structural damages modify the dynamical behavior of the structure and consequently its FRFs making possible to calculate a representative Damage Index. Main target of this work was to test the developed NDT for identifying and analyzing typical corrosive phenomena. A thin aluminium plate, typical for aeronautical employ, was chosen as test-article; an array of piezoelectric patches has been employed for both exciting the test article and acquiring the structural response in many points of it. Both homogeneous and localized corrosion phenomena have been recreated on the plate surface in laboratory environment. Two expressions of Damage Indices were calculated and statistically analyzed. Very small percentages of thickness variations have been detected and localized using the proposed methodology and it has been possible to follow corrosion dynamics (in terms of mass and stiffness variations of the test-article) by monitoring the values of the experimental Damage Indices.

Cost-effective and reliable damage detection is critical for the utilization of composite materials. This paper presents the conclusions of an experimental and analytical survey of candidate methods for in-situ damage detection in composite structures. Experimental results are presented for the application of modal analysis and Lamb wave techniques to quasi-isotropic graphite/epoxy test specimens containing representative damage. Piezoelectric patches were used as actuators and sensors for both sets of experiments. Modal analysis methods were reliable for detecting small amounts of global damage in a simple composite structure. By comparison, Lamb wave methods were sensitive to all types of local damage present between the sensor and actuator, provided useful information about damage presence and severity, and present the possibility of estimating damage type and location. Analogous experiments were also performed for more complex built-up structures. These techniques are suitable for structural health monitoring applications since they can be applied with low power conformable sensors and can provide useful information about the state of a structure during operation. Piezoelectric patches could also be used as multipurpose sensors to detect damage by a variety of methods such as modal analysis, Lamb wave, acoustic emission and strain based methods simultaneously, by altering driving frequencies and sampling rates. This paper present guidelines and recommendations drawn from this research to assist in the design of a structural health monitoring system for a vehicle. These systems will be an important component in future designs of air and spacecraft to increase the feasibility of their missions.

A built-in diagnostic system is being developed to identify de-bond between the skins and the honeycomb core of a sandwich structure. The system will be totally automated which will greatly reduce the time needed to inspect sandwich structures. The project is divided into two parts: Design and manufacturing of the sensors to detect damage and development of software to interpret the sensor data. Due to the extreme temperatures, most sensors will not survive the cryogenic temperatures of the inner skin where the damage is located. An array of sensors integrated in the sandwich panel is used to detect the damage. These sensors are embedded on the warmer side of the structure, but are able to probe for damage on the colder side of the tank. A cost-effective method is being developed to install these sensors without modifying the traditional sandwich manufacturing technique. The software compares the sensor and the baseline data. Based on the change in signal, it outputs the location and size of the damage.

The Japanese Smart Material and Structure System Project started in 1998 and has been developing several key sensor and actuator elements. This project consists of four research groups that consist of structural health monitoring, smart manufacturing, active/adaptive structures, and actuator materials/devices. In order to integrate the developed sensor and actuator elements into a smart structure system and show the validity of the system, two demonstrator programs have been established. Both demonstrators are CFRP stiffened cylindrical structures with 1.5 m in diameter and 3 m in length. The first demonstrator integrates the following six innovative techniques: (1) impact damage detection using embedded small-diameter optical fiber sensors newly developed in this program, (2) impact damage detection using the integrated acoustic emission (AE) system, (3) whole-field strain mapping using the BOTDR/FBG integrated system, (4) damage suppression using embedded shape memory alloy (SMA) foils, (5) maximum and cyclic strain sensing using smart composite patches, and (6) smart manufacturing using the integrated sensing system. The second one is for demonstrating the suppression of vibration and acoustic noise generated in the composite cylindrical structure. High-performance PZT actuators developed in this program are also installed. The detailed design of the demonstrator was made and the testing program has been planned to minimize the time and the cost for the demonstration. The present status of the demonstrator program is presented, including the success and difficulty in the on-going program.

In this paper the sensitivity of embedded fiber optic sensors to changes in modal characteristics of plates is discussed. In order to determine the feasibility of embedded fiber Bragg gratings for the detection of modal shapes and modal frequencies, a comparison of holographically imaged modes and the detected dynamic strain from embedded fiber optic Bragg gratings is made. Time averaged optical holography is used for the detection of mechanical defects, or damage, in various aerospace components. The damage is detected by measuring an alteration in structural dynamics, which is visually apparent when using time-averaged holography. These shifts in the mode shapes, both in frequency of the resonance and spatial location of vibration nodes, are caused by changes in parameters that affect the structure's mechanical impedance, such as stiffness, mass and damping, resulting from cracks or holes. It is anticipated that embedded fiber optic sensor arrays may also be able to detect component damage by sensing these changes in modal characteristics. This work is designed to give an initial indication to the feasibility of damage detection through the monitoring of modal frequencies and mode shapes with fiber optic sensors.

This paper discusses a new signal processing tool involving the use of empirical mode decomposition and its application to health monitoring of structures. Empirical mode decomposition is a time series analysis method that extracts a custom set of basis sets to describe the vibratory response of a system. In conjunction with the Hilbert Transform, the empirical mode decomposition method provides some unique information about the nature of the vibratory response. In this paper, the method is used to process time series data from a variety of one-dimensional structures with and without structural damage. Derived basis sets are then processed through the Hilbert-Huang Transform to obtain phase and damping information. This phase and damping information is later processed to extract the underlying incident energy propagating through the structure. This incident energy is also referred to as the dereverberated response of a structure. Using simple physics based models of one-dimensional structures, it is possible to determine the location and extent of damage by tracking phase properties between successive degrees of freedom. This paper presents results obtained on a civil building model. Results illustrate that this new time-series method is a powerful signal processing tool that tracks unique features in the vibratory response of structures.

In this paper, structural health monitoring based on wavelet analysis is investigated to detect damages in thin aluminum plates. Conventional methods in health monitoring mainly focus on differences in the modal parameters such as natural frequency, but they require the existence of a large damage in order to detect the damage efficiently. In this paper the damage feature is extracted from the distribution energy metric by means of wavelet packet algorithms, which can demonstrate the large difference even when the damage is very small. Experimental research is carried out to validate the method used in our approach. Piezoceramic actuators and sensors are used to excite the plate and sense the induced vibrations. Wavelet analysis is then conducted using the recorded data to obtain the distribution energy metric for each plate. As a result, it is shown that the health status of thin aluminum plates with small holes can be effectively identified through the distribution energy metric.

Bonded composite repairs for the reinforcement of damaged aircraft structures are effective in extending the life of aging airframes. The structural integrity of the composite patch repair in terms of disbond, fracture at the bond-lines, delamination, and structural crack growth is to be investigated before the composite repair technology can be adopted by the aerospace industry. We have developed structural health monitoring techniques for locating, identifying, and quantifying damages using the changes in the dynamical response of the repaired structure. A signal-based health monitoring algorithms wavelet transforms, have been developed for monitoring the structural integrity of composite patches, which detects variations induced by small changes in the vibration signature of the repaired structure. In this paper, threshold wavelet maps and neural networks have been integrated to detect and quantify the damage (s) in the composite patch repairs. Neural networks are utilized to find the extent of the damage. This method is also capable of detecting multiple damages. The mode shapes are obtained analytically using finite element analysis and experimentally with laser vibrometer. We have also developed a wireless data acquisition system for collection, feature extraction, and transmission of vibration data. The results of the damage location and extent estimation in the composite patch repairs are satisfactory.

Stabilized platforms are required for two needs: (1) isolating vibrating machinery from a precision bus, and (2) quieting and precisely pointing a payload attached to a noisy, coarsely pointed bus. The early technology was based on platforms with simple passive struts, distributed in some geometry between the bus and the payload. Passive isolators have since improved. Also, active struts have augmented and sometimes replaced passive struts. To date, most research in this field has been concentrated on developing struts, so strut technology is becoming relatively mature. However, several struts are needed to support the payload, so the complex interactions between struts is critical, especially when performing pointing and tracking. Pertinent issues include: supporting the payload; making the struts function in unison in as many axes as possible; fault tolerance; control over a large range of bandwidth, stroke and load. Efforts at different sites are continuing relatively independently and, so far, very little attention has been given to developing optimization methods for matching platform design to applications. In this presentation, we will discuss the state-of-the-art platforms developed to deal with specific applications and present an overview of the performance characteristics of these different platforms. Using these models, we formulate various applications, and problems arising from these applications, that are not addressed by the existing technology. These problems deal with the geometry of the platform, control, DOF, and fault tolerance concerns.

Over-constrained parallel manipulators can be used for fault tolerance. This paper derives the differential kinematics and static force model for a general over-constrained rigid multibody system. The result shows that the redundant constraints result in constrained active joints and redundant internal force. By incorporating these constraints, general methods for overcoming stuck legs or even the complete loss of legs are derived. The Stewart platform special case is studied as an example, and the relationship between its forward Jacobian and its inverse Jacobian is also found.

Adaptive tuned vibration absorbers for attenuation of harmonic vibration may be realized through the use of active materials in absorber designs. For example, the variable elastic modulus of shape memory alloy may be used to incorporate variable springs in an absorber, such that the absorber natural frequency may be on-line tuned. The difficulty then becomes the control of the tuned condition of the absorber. One method for controlling the tuned condition of the absorber is to drive the relative phase between the primary system and the absorber to a desired value. The classical phase-locked loop is one method that might be used to achieve this control goal. An alternative method is to utilize a simple PI controller that uses the relative phase as an error signal. The map between the control input to the active material elements and the resulting relative phase can be modeled as a first-order linear system in series with a static nonlinearity with certain characteristics. This paper presents an analysis of the stability of the phase tracking of an adaptive tuned vibration absorber made of active material. The necessary characteristics for the map between the control signal and the resulting relative phase are presented. A control algorithm is developed that results in asymptotic stability of the system in the presence of an uncertain fixed excitation frequency. Results of implementation of an experimental ATVA on a primary system are presented.

This paper presents on-going research directed towards the development of MEMS actuators for improved aerodynamic efficiency of micro-rotorcraft. A 6 inches diameter micro-rotor system was developed and tested in hover. Results indicated that profile power losses associated with low Reynolds number viscous flows and flow separation and stall at high angles of attack limit the rotor performance at micro-scale. It is envisaged that tripping the flow from laminar to turbulent at the leading edge of the rotor blade can prevent formation of the laminar separation bubble and improve lifting efficiency of the micro-rotor. This study will present the design of a prototype MEMS actuator (piezoelectric thin film). It is envisaged that multiple arrays of such MEMS devices can be assembled on the surface of the airfoil section to create a smart skin. The smart skin when actuated provides controllable surface roughness that can be used to enable premature boundary layer transition.

Modern combat aircraft are required to achieve aggressive maneuverability and high agility performance, while maintaining handling qualities over a wide range of flight conditions. Recently, a new adaptive-structural concept called variable stiffness spar is proposed in order to increase the maneuverability of the flexible aircraft. The variable stiffness spar controls wing torsional stiffness to enhance roll performance in the complete flight envelope. However, variable stiffness spar requires the mechanical actuation system in order to rotate the Variable stiffness spar during flight. The mechanical actuation system to rotate variable stiffness spar may cause an additional weight increase. In this paper, we will apply Shape Memory Alloy (SMA) spars for aeroelastic performance enhancement. In order to explore the potential of SMA spar design, roll performance of the composite smart wings will be investigated using ASTROS. Parametric study will be conducted to investigate the SMA spar effects by changing the spar locations and geometry. The results show that with activation of the SMA spar, the roll effectiveness can be increased up to 61% compared with the baseline model.

In this paper, a prototype SMA-based actuator for a compact kinetic energy missile was fabricated. Thin film nickel-titanium was selected as an actuating mechanism because it exhibited high power density compared to other smart materials. This study represents a proof of concept that high drive frequency and high power density can be both achieved with thin film SMA. The thin film reached a drive frequency of 80Hz while achieving a power density of 27900 Watts/kg. As for the pump, the power density was 2.93 Watts/kg, but obtaining higher value can certainly be achieved by reducing the chamber weight through optimization. In any case, CFD analysis revealed that the pump chamber had to be redesigned to change the flow profile because the present design created non-circulating dead zones immediately adjacent to the diaphragm. Therefore by redirecting the liquid flow to directly cool the SMA diaphragm improved the heat transfer and thus improved performance of the actuator can be achieved.

A shape memory alloy actuated tab deflection mechanism for in-flight rotor blade tracking was designed, fabricated and tested. The design, comprises of dual SMA wire actuation device, passive lock and on-blade sensors. The system is integrated with a feedback position controller. Improvements, over the previous design, in shape memory alloy wire clamping mechanism, locking mechanism and controller operation were examined. An analytical model, incorporating Brinson's thermomechanical model was developed to predict actuator behavior. A design methodology, based on this model, was applied to identify the relationship between actuator design parameters and actuator target goals. The actuation system integrated into an NACA0012 blade section was tested on the bench-top. Tracking capability of +/- 6 degree(s) with a resolution of +/- 0.1 degree(s) was demonstrated.

The unique thermal and mechanical properties exhibited by shape memory alloys (SMAs) present exciting design possibilities in the field of aerospace engineering. When properly trained, SMA wires act as linear actuators by contracting when heated and returning to their original shape when cooled. These SMA wire actuators can be attached to points on the inside of an airfoil, and can be activated to alter the shape of the airfoil. This shape-change can effectively increase the efficiency of a wing in flight at several different flow regimes. Design optimization has previously been conducted to determine the placement of actuators within the reconfigurable airfoil. A wind tunnel model reconfigurable wing was fabricated based on the design optimization to verify the predicted structural and aerodynamic response. Wind tunnel tests indicated an increase in lift for a given flow velocity and angle of attack by activating the SMA wire actuators. The pressure data taken during the wind tunnel tests followed the trends expected from the numerical pressure results.

In the present work, a finite element model based on the layerwise theory of Reddy is developed for laminated plates including piezoelectric layers or patches. Several interpolation schemes are considered and the results achieved are discussed by comparison with 3D elasticity analytical solutions.

The coupling effect of an electric field with a mechanical deformation makes piezoelectric materials feasible for sensing or actuating functions in structural applications. In a self-sensing actuator system, a single piece of piezoelectric element can be used as both sensor and actuator simultaneously. This technique achieves a truly sensor-actuator collocation and reduces the weight of the structural system as compared to the structure with separate sensor and actuator. However, the self-sensing configuration inherently contains a feedforward dynamics. In order to achieve the self-sensing actuation, the feedforward signal due to the control input must be separated so that the sensing signal is only induced from the mechanical response. The feedforward dynamics is related to the equivalent capacitance of the piezoelectric element, which is subject to change in the ambience. In addition, due to the relatively high amplitudes of the control signal to the mechanical response, small variation of the capacitance would corrupt the sensing voltage. For closed loop applications, this corruption would degrade the system performance or lead it to unstable. In this paper, a self-tuning adaptive algorithm is proposed to compensate for the capacitance variation. Subject to temperature variation, a cantilever beam bonded with a single piezoelectric patch is implemented to demonstrate the effectiveness of the self-sensing actuation. The proposed adaptive algorithm is used to separate the mechanical signal from the total response. Concurrently, control input is generated based on the compensated sensing voltage to actively suppress the beam vibration.

The design of fully integrated structures, and especially of new generation composites with embedded sensors and actuators, now requires the development of adequate tools for predicting the static and the dynamic behavior of the structure as well as its life cycle. These tools will provide flexibility in assessing well-suited control strategies for optimum structural performance. As a first step towards the development of integrated computational tools for smart structures, this work validates both theoretically and experimentally the implementation under MSC/NASTRAN of a simplified multilayer tri-dimensional model based on the analogy between thermal strains and piezoelectric strains. Numerical results obtained from this model are first compared to results obtained from a reference finite element tri-dimensional piezoelectric code developed to assess the thermal analogy for different loading conditions. Experimental validation is also conducted on a clamped AS4/3501-6 carbon/epoxy composite beam structure excited at the clamped end by an embedded piezoelectric. Results obtained from vibration testing are assessed with the thermal analogy model using a large number of tri-dimensional elements in order to get a detailed representation of the different variables. Details for practical implementation of the embedment procedures are presented along with the adequate model prediction of the structure's dynamic behavior.

A smart composite material system which has three smart functions of sensor, actuator and processor has been developed intend to apply to structure of house for controlling ambient temperature and humidity, hands of robot for holding and feeling an object, and so on. A carbon fiber reinforced plastics (CFRP) is used as matrix in the smart composite. The size of the matrix is 120mm x 24mm x 0.45mm. The CFRP plate is combined two Ni-Ti shape memory alloy (SMA) wires with an elastic rubber to construct a composite material. The composite material has a characteristic of reversible response with respect to temperature. A photo-sensor and temperature sensor are embedded in the composite material. The composite material has a processor function to combine with a simple CPU (processor) unit. For demonstrating the capability of the composite material system, a model is built up for controlling certain behaviors such as gripping and releasing a spherical object. The amplitude of gripping force is (3.0 plus/minus 0.3) N in the measurement, which is consistent with our calculation of 2.7 N. Out of a variety of functions to be executed by the CPU, it is shown to exert calculation and decision making in regard to object selection, object holding, and ON-OFF control of action by external commands.

Maintaining surface shape of precision structures such as spacecraft antenna reflectors has been a challenging task. The surface errors are often introduced by thermal distortions due to temperature differences. This paper presents numerical and experimental results of active compensation of thermal deformation of a composite beam using piezoelectric ceramic actuators. To generate thermal distortion to the composite beam, two film heaters are bonded to only one-side of the beam using thermally conductive materials. To correct thermal deformation caused by the film heaters, PZT (Lead Zirconate Titanate), a type of a piezoelectric ceramic material, is used in the form of patches as actuators. These PZT patches are bonded on the other side of the beam. First, finite element analyses are conducted with the consideration of the coupled effects of structural, electric, and thermal fields on the composite beam. These analyses include static coupled field modeling of the beam deformation with PZT actuation, transient modeling of the beam under thermal loading, and static coupled field modeling of the composite beam with thermal distortion and simultaneous PZT actuation to correct this distortion. Then, experiments are conducted to study thermal effect, PZT actuation effect and active thermal distortion compensation using PZT actuators with a Proportional, Integral, and Derivative (PID) feedback controller. FEM and experimental results agree well and demonstrate the proposed method can actively perform structural shape control in the presence of thermal distortion.

This paper presents a new standing wave type linear motor that can move bi-directionally with identical performance in both the forward and backward directions. The motor consists of a metallic stator and two piezoceramic plates bonded to the stator with the spatial phase difference of a half wavelength. With two electric driving signals either in-phase or out-of-phase for the two piezoceramic plates, the piezoceramic plates excite two ultrasonic standing waves with a certain phase difference. They generate a new standing wave when combined. The operation principle of the motor is verified through finite element analyses. For an experimental illustration of the theoretical and numerical results, a sample motor is fabricated and characterized following the numerical design. The experimental results confirm the validity and practical applicability of the new motor structure.

A variety of Industrial applications exist where power ultrasonic elements such as the ultrasonic horn are used. These included the Automotive, Instruments, Foods, Medical, Textiles and Material Joining and Fabrication Industries. In many of these devices the ultrasonic horn is the key component. The standard transducer used in these devices consists of three main parts, the backing, the piezoelectric elements and the horn. Standard horn designs have changed very little since their inception. There are four common types of standard horns. They are; constant, linear, exponential and stepped, which refer to the degree to which the area changes from the base to the tip. A magnification in the strain occurs in the horn that in general is a function of the ratio of diameters. In addition the device is generally driven at resonance to further amplify the strain. The resonance amplification is in general determined by the mechanical Q (attenuation) of the horn material and radiation damping. The horn length primarily determines the resonance frequency. For a 22 kHz resonance frequency a stepped horn of titanium has a length of approximately 8 cm. Although these standard horns are found in many current industrial designs they suffer from some key limitations. In many applications it would be useful to reduce the resonance frequency however this would require device lengths of the order of fractions of meters which may be impractical. In addition, manufacturing a horn requires the turning down of the stock material (eg. Titanium) from the larger outer diameter to the horn tip diameter, which is both time consuming and wasteful. In this paper we will present a variety of novel horn designs, which overcome some of the limitations discussed above. One particular design that has been found to overcome these limitations is the folded horn. In this design the horn elements are folded which reduce the overall length of the resonator (physical length) but maintain or increase the acoustic length. In addition initial experiments indicate that the tip displacement can be further adjusted by phasing the bending displacements and the extensional displacements. The experimental results for a variety of these and other novel horn designs will be presented and compared to the results predicted by theory.

In-situ sampling and analysis is one of the major tasks in future NASA exploration missions. It is essential that the samples acquired on other planets including Mars are free of contaminations from the Earth. Recently, a novel drilling technology that is actuated by a piezoelectric drive mechanism was developed and it is called Ultrasonic/Sonic Driller/Corer (USDC). This drill has an inherent capability to extract the formed drilling powder and thus addresses the critical issue of contamination. A modification of this USDC in the form of an Ultrasonic Rock Abrasion Tool (URAT) allows for the formation of pristine rock surface for analysis. An algorithm is being proposed for the reduction of the contamination that may be generated during the acquisition of the samples. The algorithm could be used to control the flow of particles using programmed vibration characteristics and thus allows for smart flow of particles. The hypothesis is that the probability of a contamination left on the ground surface is exponentially inverse- proportional to the volume of the core ground into dusts. To support this hypothesis, we need to understand the flow pattern of the particles. A model proposed by Savage is used to develop a computer program using finite difference method. Some preliminary results have been derived.

An ultrasonic/sonic driller/corer (USDC) was developed to address the challenges to the NASA objective of planetary in-situ rock sampling and analysis. The USDC uses a novel drive mechanism, transferring ultrasonic vibration into impacts on a drill stem at sonic frequency using a free- flying mass block (free-mass). The main parts of the device and the interactions between them were analyzed and numerically modeled to understand the drive mechanism and allow design of effective drilling mechanism. A computer program was developed to simulate the operation of the USDC and successfully predicted the characteristic behavior of the new device. This paper covers the theory, the analytical models and the algorithms that were developed and the predicted results.

MEMS fabrication technology has facilitated the implementation of a broad variety of low-cost miniature sensors, including those for measuring linear and angular rates of objects-of-interest. Earlier work has focused on component-level sensor fabrication issues and proof-of- concept verification of their sensing ability. This prior work has provided the foundation for design and performance assessment of the next generation of multi-axis embedded MEMS sensors at a subsystem level. Subsequently, this will lead to the fabrication of an integrated self-calibrating 6 degree-of-freedom (DOF) strapdown intertial sensor assembled in a low-cost miniature package. This in turn will lead to a variety of applications that are currently unrealistic because of cost-weight-power considerations. This particular effort is directed toward establishing the feasibility of extracting additional information from a MEMS sensor by appropriately exciting a single-axis Coriolis sensor, for example, to generate optimum angular velocity and angular acceleration estimates, whereas prior studies have shown only the ability to generate approximate angular acceleration estimates, whereas prior studies have shown only the ability to generate approximate angular rotational velocity measurements. This work entailed the dynamic modeling of a representative MEMS sensor and several different angular velocity and angular acceleration driving functions in a MATLAB-based simulation. The corresponding raw sensor outputs were then optimally processed to concurrently generate estimates of both angular velocity and angular acceleration. The graphical results form these simulation studies are included to show the benefit of physically co-locating a digital computing element with the MEMS sensor, thereby facilitating the creation of a new generation of digital smart sensors, that will be capable of self-calibration based performance deterioration assessment, fault detection and recovery.

The optimization of actuator and sensor parameters in smart structures often requires extensive piezostructure modeling calculations. In order to facilitate these optimizations, a versatile and computationally efficient technique for the modeling of piezostructures into analytical systems has been developed. The method uses one apriori calculation of the coupling characteristics of gridded piezoelectric elements, contiguously covering the entire structure. This allows for the rapid calculation of the coupling characteristics of any patch configuration by summing the effects of the elements contained within the patch boundaries. Some of the advantages of this approach are the lack of error checking necessary with respect to trial patches being located within structural boundaries. Additionally, patch shape restrictions are not tied to difficulties associated with complicated integration limits, and reversed phasing of patch segments is a trivial matter. A technique is also developed to estimate the extent that patch mass and stiffness contributions will influence system response. This method is entirely parameter based and does not require explicit system modeling. It is illustrated how these techniques can dramatically expand the range, versatility, and efficiency of transducer optimization routines. Implementation examples are shown, along with comparisons with more conventional modeling approaches.

Experimental studies of closed-loop control of longitudinal wave transmission through a hollow cylinder are presented in this article. Model studies coupled with experimental modal analysis are used to understand and characterize the actuator-strut ensemble, and a boundary control algorithm, which falls under the class of feedforward control schemes, is experimentally implemented. The algorithm is based on a partial differential equations (PDE) model of the strut-actuator system, and a combination of strain and acceleration measurements are used to solve the boundary-value problem in the implementation. Harmonic vibratory disturbances are transmitted in the frequency range extending up to 1 kHz, and it has been demonstrated that a vibration attenuation of up to 16 dB can be achieved by using a magnetostrictive actuator in this model-based control scheme.

This paper presents a theoretical development and an experimental validation of a hybrid control algorithm for the active noise control in the rectangular enclosure with lightly damped boundaries. The hybrid control composes of the adaptive feedforward with feedback loop in which the adaptive feedforward control uses the well-known filtered-x LMS(least mean square) algorithm and the feedback loop consists of the sliding mode controller and observer. The hybrid control has its robustness for both transient and persistent external disturbances and increases the convergence speed due to the reduced variance of the filtered-x signal by adding the feedback loop. The sliding mode control (SMC) is used to incorporate modeling errors, disturbances and uncertainties in the controller deign. This paper also investigates the potential of noise control using a smart foam actuator, which is designed to minimize noise passively using an absorption-foam and actively using an embedded PVDF film driven by an electrical input. The error path dynamics is experimentally identified in the form of the auto-regressive and moving-average using the frequency domain identification technique. Experiment results demonstrate the effectiveness of the hybrid control and the feasibility of the smart foam actuator.

Various solid-state mechanisms for the amplification of the small stroke, produced by piezoelectric materials, have been presented in the literature. A designer tasked with designing a device such as a micro-positioner must choose between these mechanisms. In this paper, the use of topological optimization to produce characteristic functions for amplification mechanisms, forming a basis for comparison of different designs, is investigated. The optimization problem was formulated as a variable thickness sheet problem where the stiffness was maximized subject to a constraint on the free stoke. Apart from specifying the design domain, no volume constraints were imposed. The design domain, comprising a piezoelectric and a metallic region, was discretized with eight-noded, plane-strain finite elements. This formulation was found to produce designs with negligible intermediate thickness. These designs are non-unique and repeatedly solving the problem from different starting material distributions results in slightly different 'optimal' stiffness values. The resulting maximum stiffness can be plotted as a function of free stroke producing a curve that is characteristic of the amplification mechanism. Irregularities in this curve would indicate that a local maximum with poor performance has been found. The method is demonstrated by computing the characteristic curve for two amplifier mechanisms.

R<-->A phase transformation in NiTi alloy is associated with a very small recoverable strain of the order of 0.5% compared to that of 6-8% recoverable strain of M<-->A transformation. The stability of R<-->A transformation against large number of thermal cycles is an attractive feature for an application of SMA. A spring of NiTi is designed and fabricated, using 40% prior cold worked nitinol wire of dia 1mm, with appropriate heat-treatment such that martensitic transformation takes place through two stage A-->R-->M. The transformation behaviors of this wire are studied using DSC and electrical resistivity measurements. Further, the spring has been subjected to thermo-mechanical treatment for getting a two-way memory, viz:, while heating the spring gets contracted and while cooling it gets elongated. This spring has been used as an thermal actuator and temperature variation is confined between 50-65 degree(s)C to utilize only R<-->A transformation. Linear stroke of 4cm by the spring is used to rotate a platform carrying a load of 2 kg. The efficiency and reliability of the spring is tested over a million thermal cycles.

Piezoceramic actuation has become an area of increased interest in the past ten years. Having been used for many years as sensors in such applications as pressure transducers and smoke detectors, piezoceramics are now being used as prime movers in fuel injectors and valve lifters. In an effort to aid the engineering community, this paper will conduct a comprehensive review of several piezoceramic actuators. Classical design parameters will be derived for each actuator such as blocked force and free stroke. In addition, more esoteric entities such as mechanical efficiency and energy density will also be derived. The result will be design metrics of popular piezoceramic actuators containing vital design equations, validated with empirical data. Of the many different configurations of piezoceramic actuators, this paper will investigate the bimorph and unimorph bender. These actuator types are finding increased use in semi-active structural damping, energy harvesting and vibration control. The work in this paper will show experimental verification of various actuator types as well as theoretical derivations. In addition to unimorphs, bimorphs and stack actuators a novel type of unimorph bender, the THUNDER actuator (developed and licensed by NASA) will be included in the review.

A new actuator design is introduced, which utilizes a pair of matching piezoelectric stack elements within the actuator housing. The stack elements are utilized in a mechanically opposing configuration and are electrically operated out-of-phase. Conventional piezoelectric stack actuators usually incorporate a compressive preload mechanism to protect the stack from tensile stresses. A common preload method is to incorporate a mechanical spring in parallel with the stack. However, the mechanical spring reduces the free stroke capabilities of the stack actuator. To demonstrate the performance advantages of the new concept, an analytical and experimental comparison study is conducted. The dual stack actuator is compared with two conventional internally preloaded single stack actuators in a parallel configuration, thus both actuator configurations are utilizing equivalent volumes of the piezoelectric material. The analysis indicates the dual stack actuator produces greater free stroke, output energy, and energy efficiency than two parallel single stack actuators. For experimental evaluations, a dual stack actuator and an internally preloaded single stack actuator are fabricated using the same materials, similar construction techniques, and the same piezoelectric stack elements. A testing procedure is formulated to determine the free stroke and blocked force of both actuators. Comparison of the experimental data reveals a number of performance advantages of the dual stack actuator over two traditional preloaded actuators in parallel: the free stroke is 1.3-1.2 times greater; the blocked force is 1.4-1.2 times greater; the output energy is 1.8-1.5 times greater; the specific output energy is 2.4-1.9 times greater; and the energy efficiency is 1.8-1.5 times greater.

The elastic behavior of porous piezo-laminates actuators is developed using modified classical lamination theory (CLT). The curvature is obtained for porous piezoelectric laminate with functionally graded microstructure (FGM) under applied voltage throughout its thickness. The porous FGM system consists of multi porous piezoelectric layers where the porosity gradient increases in the thickness direction. The porous FGM actuator is fabricated by co-sintering powder compacts of PZT and stearic acid in air. The electroelastic properties of each layer in the FGM systems were measured and used as input data in the analytical model to predict the FGM actuator curvature. Two optimization techniques are employed to enhance the performance of the porous FGM actuators: (1) Thickness of each layer in the porous FGM actuator, (2) Number of layer in the porous FGM actuator. The thickness of each layer in the FGM system is made to vary in a linear or non-linear manner by changing the FGM thickness exponent. Two, three, and five layer porous FGM systems are investigated to obtain the maximum curvature. The analytical predictions are found to agree well with the experimental measurements.

This paper proposes a novel type of the piezoactuator-driven hydraulic pump(piezo pump in short) in order to control the position of a cylinder system. The piezo pump is operated by the dynamic motion of a diaphragm directly attached to the piezoactuator. The governing equation of the flow motion of the piezo pump id derived and an appropriate size of the piezo pump is designed and manufactured. The pressure drop and flow rate of the pump are experimentally evaluated at various voltages. The piezo pump is then incorporated with a single-rod cylinder system. A sliding mode controller is designed to achieve an accurate position control of the cylinder and practically realized. Position control performances for step and sinusoidal trajectories are evaluated and presented in time domain.

In this work, smart missile fins with trailing-edge-mounted retractable wedge are investigated. The wedge stretches back or forth in the chordwise direction in a means to reduce the applied pitching moment acting on the missile fins. An actuator system, which is composed of a one-way clutch bearing, driving shaft with thread and sliding nut and a piezo-bimorph beam, has been built and tested to verify the concept of the actuator. This actuator is designed to translate the rotational motion of the shaft into the linear motion of the sliding nut to generate a desired stroke. When a voltage signal is applied at a given frequency to the piezo-element, it will bend up and down. This bending action induces an angular input to the shaft, which is then rectified with the clutch bearing to the rotational output of the shaft. Preliminary tests showed that the proposed actuator system can be very effective in generating large stroke output with relatively small voltage inputs: Nearly 19mm of actuator displacement was obtained under an input voltage of 75 V_rms at a frequency level of 700 Hz. A series of experimental tests as well as CFD calculations for missile aerodynamics have been performed to investigate the effectiveness of the actuator.

The development of a new class of devices for the suppression of structural vibration becomes possible by exploiting the unique properties of single crystal piezoceramics. These vibration absorbers will be compact, robust, and demand minimal power for operation. They will be characterized by frequency agility, which means that the absorber tuning parameters can adapt rapidly to controller command and tuning can be accomplished over a wide frequency range. Identified applications include control of turbomachinery vibration, flexible space structures, jitter control in optical systems, and vibration isolation in machinery mounts. The current state of the art adaptive vibration absorber tuning range is fundamentally limited by the electromechanical coupling of presently available polycrystalline piezoceramic materials. The narrow tuning range characteristic of current vibration absorbers severely limits the implementation of the solid-state absorber concept. This work presents efforts related to the design of vibration absorbers that use the single-crystal piezoceramic large electromechanical coupling to achieve greatly enhanced tuning over a wide frequency range. Absorber electromechanical coupling-coefficients greater than 50% were obtained. Design issues specifically related to the use of single crystals in vibration absorbers were identified and addressed. Several device configurations were analyzed and tested. Good agreement was observed between analytical and experimental results.

This paper presents the design and development of a pitching and plunging (flapping) mechanism for small-scale flight. In order to harness the unsteady lift mechanisms, used by most insects, a biologically inspired flapping/pitching device in conjunction with a rotary wing concept was developed and built. This mechanism attempts to replicate some of the aerodynamic phenomena that enhance the performance of small fliers, replacing the periodic translational motion with a unidirectional circular motion while actively flapping and pitching the rotor blades. In order to find the appropriate combination of phase, amplitude, frequency and rotational speed that leads to enhancement in lift, the device requires uncoupled independent pitch and flap actuation systems to permit the complete mapping of the parameter space. In the device under consideration the phase shift between the flapping and the pitching oscillations can be adjusted from 0 to 360 degrees over a wide range of rotational speeds. Maximum flapping and pitching amplitudes of +/- 23 degree(s) and +/- 20 degree(s) respectively can be attained. Linear displacements of two coaxial shafts are translated into the flapping and pitching motion of the rotor blades. The mechanism was designed to minimize the actuation stroke so that smart materials and conventional actuators such as motors and cams could be used. Kinematic analysis as well as experimental tests were performed. Using a customized test stand thrust and torque produced by the rotor were measured at different angles of attack, in steady-state and under periodical pitching actuation. The results showed that hover efficiency was considerably increased for a range of thrust coefficients. The device was developed based on the University of Maryland's rotary wing Micro Air vehicle (MAV) the MICOR (MIcro COaxial Rotorcraft), an electrically driven 100 g coaxial helicopter. It is anticipated that active flapping and/or pitching could be implemented in the prototype to improve its aerodynamic performance. The present paper will discuss the design and development process of a rotating/pitching/flapping mechanism for MAVs. Test results indicate that unsteady pitching motion can be used to include the aerodynamic effect of delayed stall. Performance measurements confirm that unsteady pitching motion improves efficiency in hover.

The development of a piezoelectric hydraulic pump with innovative active valves is presented in this study. The pump structure basically consists of a diaphragm type piezoelectric stack actuator and two specially designed unimorph disc valves acting as inlet and delivery valves. Static and dynamic piezoelectric finite element analyses were used to maximize the delivered fluid volume per stroke and to predict the resonance characteristics of the pump, respectively. A structural optimization technique was performed to optimize the efficiency of the pump versus its geometrical dimensions. A transient CFD model was used to predict flow rates. Dynamic experiments were also conducted and results are in good agreement with those obtained from the simulation.

The concept of piezohydraulic actuation is to transfer the reciprocal small stroke displacement of piezoceramics into one directional movement by frequency rectification through the media of hydraulic fluid. Our work in piezohydraulic actuation is focused on the development of systems that incorporate active valves for flow control. We present experimental results demonstrating the importance of fluid compressibility and valve timing in the optimization of the output power of the actuation system. An efficiency analysis is also presented. Results show the effective bulk modulus of the fluid is approximately linearly dependent on pressure. A linear bulk modulus to pressure model for the working fluid is developed and the data is compared to experimental results. An array of different timing tests are run on the inlet and outlet valves and the results show that their timing is crucial to the performance of the system. Also shown is that the optimal timing conditions change slightly under different loads. To analyze the power and efficiency, the system is considered as two sub-systems, the piezoceramics sub-system and the hydraulic component sub-system. The power and efficiency of each sub-system is measured and analyzed under different loads. As load increases, the results show that the efficiency of the piezoceramics decreases while the efficiency of the hydraulic components increases.

This paper describes the design and testing of a piezoelectric hydraulic hybrid actuator operating at a high pumping frequency. The actuator is envisaged as a potential actuator for a trailing edge flap of a full scale smart rotor system. Recent research efforts on piezoelectric hydraulic hybrid actuators have investigated devices based on large piezoelectric stacks operating at a relatively low pumping frequency. The present work focuses on the behavior of such an actuator operating at a high pumping frequency and low volumetric displacement. Challenges to achieving high pumping frequencies were identified and solutions were implemented. The actuator was driven by two piezostacks, of a total length of 36 mm and cross-sectional area 10 mm². The actuator was tested up to a pumping frequency of 1 kHz, developing a maximum no-load velocity of 1.2 in/sec and a blocked force of 35 lbs in the uni-directional output mode. Bi-directional output performance was also measured, by incorporating a 4-way valve in the hydraulic circuit. At a frequency of 5 Hz, a no-load output displacement with an amplitude 32 mils was measured.

Inflatable structures have been a subject of renewed interest in recent years for space applications. Actuators and sensors made of piezoelectric materials are recently being considered for the vibration and shapes control of such structures. This study is directed towards developing actuator and sensor models of piezoelectric films attached to an inflatable structure, which can be modeled as a shell under pressure. The derivations are made using the definitions of strain energy and kinetic energy. We use Sanders' shell theory to model the vibration of shell and derive the constitutive equations for combinations of shell and piezoelectric patches in unimorph and bimorph configurations. Equations of motion for the shell vibrating in the presence of actuators have been obtained. The inertia terms in the equations of motion are modified in order to account for the mass of the actuators. The generalized forces due to piezoelectric actuators are found. Finally, a sensor equation is provided.

In this work a combined analysis of the out-of-plane mechanical and dielectric properties of auxetic re-entrant honeycombs is performed. Experimental and numerical simulations are carried out to evaluate the correlation between the anisotropicity of the transverse mechanical properties (shear and compressive modulus) and the permittivity tensor of general and auxetic (Negative Poisson's ratio) honeycombs. Different numerical and experimental techniques have been applied to obtain the mechanical and dielectric properties of general and auxetic honeycombs versus the core material and unit cell geometry parameters. The results are evaluated to assess the feasibility of this kind of cellular solid for electromagnetic screen applications with high structural integrity performance.

This study presents results from an effort to fabricate a shape memory alloy hybrid composite (SMAHC) panel specimen and test the structure for dynamic response and noise transmission characteristics under the action of thermal and random acoustic loads. A method for fabricating a SMAHC laminate with bi-directional SMA reinforcement is described. Glass-epoxy unidirectional prepreg tape and Nitinol ribbon comprise the material system. Thermal activation of the Nitinol actuators was achieved through resistive heating. The experimental hardware required for mechanical support of the panel/actuators and for establishing convenient electrical connectivity to the actuators is presented. Other experimental apparatus necessary for controlling the panel temperature and acquiring structural acoustic data are also described. Deficiency in the thermal control system was discovered in the process of performing the elevated temperature tests. Discussion of the experimental results focuses on determining the causes for the deficiency and establishing means for rectifying the problem.

In high precision space optical systems, it is critical that the structure maintains a near-perfect surface. Previous studies investigated the performance of utilizing piezoelectric ceramic patches for reducing the surface error. The research results demonstrated that the two-dimensional actuation effect of the actuator patches could induce high order modal deformations and cause undesired surface error. It was discovered that decoupling the circumferential and radial actuations of the sheet actuators could improve the system performance. To realize the decoupling effect, an active stiffener design is proposed and analyzed in this paper, where a standoff layer is inserted between the host structure and the piezoelectric ceramic sheet actuator. The stiffener acts as a decoupling mechanism which reduces the transmitted action in one direction while allowing adequate action to be transmitted in the orthogonal direction. For the analysis, a 3-D solid finite element model of a thin circular structure containing stiffeners and piezoelectric ceramic actuators is developed. It is shown that the active stiffener design achieves a smoother surface, corrects for more surface error, reduces controller spillover, and improves system stability.

One of the limitations of a piezoelectric material is the amount of force it can exert. Hence, it is important to optimize the locations and sizes of the actuators so that the required control effort is minimum. Similarly, to obtain good signal to noise ratio, sensors should be chosen to provide maximum output for the vibration in the modes of interest. These problems become more critical as the number of actuators and sensors increases. In this study, we find optimum places and sizes of actuators/sensors on an inflated toroidal shell using genetic algorithm. Using the expressions for the generalized forces and sensor voltages developed previously, modal forces and modal sensing constants are determined. To obtain a cumulative performance measure of all the controlled modes, controllability and observability indices are used. Using these performance indices, optimal locations and sizes of the actuators and sensors are determined so that the actuators require minimum energy and the sensors provides maximum output energy. Finally, using an optimal control, the vibration suppression of the inflated torus using these actuators and sensors has been demonstrated.