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Showing papers in "Smart Materials and Structures in 1997"


Journal Article•DOI•
TL;DR: In this paper, the authors reviewed the history of micromachined pressure sensors and examined new developments in the field of pressure sensors, starting from metal diaphragm sensors with bonded silicon strain gauges, and moving to present developments of surface-micromachines, optical, resonant, and smart pressure sensors.
Abstract: Since the discovery of piezoresistivity in silicon in the mid 1950s, silicon-based pressure sensors have been widely produced Micromachining technology has greatly benefited from the success of the integrated circuit industry, borrowing materials, processes, and toolsets Because of this, microelectromechanical systems (MEMS) are now poised to capture large segments of existing sensor markets and to catalyse the development of new markets Given the emerging importance of MEMS, it is instructive to review the history of micromachined pressure sensors, and to examine new developments in the field Pressure sensors will be the focus of this paper, starting from metal diaphragm sensors with bonded silicon strain gauges, and moving to present developments of surface-micromachined, optical, resonant, and smart pressure sensors Considerations for diaphragm design will be discussed in detail, as well as additional considerations for capacitive and piezoresistive devices Results from surface-micromachined pressure sensors developed by the authors will be presented Finally, advantages of micromachined sensors will be discussed

533 citations


Journal Article•DOI•
TL;DR: In this paper, the authors apply the Preisach model for the hysteresis in piezoceramic and shape memory alloys (SMAs), and present experimental results for actuators bonded to a flexible aluminum beam and a Nitinol SMA wire muscle.
Abstract: Smart materials such as piezoceramics, magnetostrictive materials, and shape memory alloys exhibit hysteresis, and the larger the input signal the larger the effect. Hysteresis can lead to unwanted harmonics, inaccuracy in open loop control, and instability in closed loop control. The Preisach independent domain hysteresis model has been shown to capture the major features of hysteresis arising in ferromagnetic materials. Noting the similarity between the microscopic domain kinematics that generate static hysteresis effects in ferromagnetics, piezoceramics, and shape memory alloys (SMAs), we apply the Preisach model for the hysteresis in piezoceramic and shape memory alloy materials. This paper reviews the basic properties of the Preisach model, discusses control-theoretic issues such as identification, simulation, and inversion, and presents experimental results for piezoceramic sheet actuators bonded to a flexible aluminum beam, and a Nitinol SMA wire muscle that applies a bending force to the end of a beam.

240 citations


Journal Article•DOI•
TL;DR: In this article, the basic properties of Love wave and their utilization in sensor devices for (bio)chemical as well as for density and viscosity measurements are discussed in general and illustrated by means of numerical sample results for an -quartz layered structure.
Abstract: Love wave sensors are highly sensitive microacoustic devices which are especially suited for sensing in liquids In this paper we review the basic properties of Love waves and their utilization in sensor devices for (bio)chemical as well as for density and viscosity measurements These properties are first discussed in general and then illustrated by means of numerical sample results for an -quartz layered structure Furthermore the technology needed to produce such a Love wave device is discussed Finally we present an overview on the current state of the art in Love wave sensor research

217 citations


Journal Article•DOI•
TL;DR: In this paper, a finite element model based on the classical laminated plate theory is developed for the active vibration control of a composite plate containing distributed piezoelectric sensors and actuators.
Abstract: A finite-element model based on the classical laminated plate theory is developed for the active vibration control of a composite plate containing distributed piezoelectric sensors and actuators. The formulation is derived from the variational principle. The piezoelectrics' mass and stiffness are taken into account in the present model. A simple negative velocity feedback control algorithm coupling the direct and converse piezoelectric effects is used to actively control the dynamic response of an integrated structure through a closed control loop. The static analysis and active vibration suppression of a cantilever composite plate are performed as a numerical example to verify the proposed model. The modal superposition technique and the Newmark- method are used in the numerical simulation to calculate the dynamic response of the laminated composite plate.

209 citations


Journal Article•DOI•
TL;DR: In this article, the results of a representative sampling of recent papers dealing with smart materials and structures as actuators in aeronautical systems are summarized and the status of some of the most promising developments is noted and the remaining problems are touched on.
Abstract: The original version of this paper was presented and distributed as part of the 37th Israel Annual Conference on Aerospace Sciences Proceedings. Without attempting a thorough review of the burgeoning literature, the results of a representative sampling of recent papers dealing with smart materials and structures as actuators in aeronautical systems are summarized here. Their potential for improving performance, handling qualities in a stall, and increasing fatigue life is discussed briefly as requiring relatively slow-acting shape and shape-distribution changes. A similar review is made of applications for improving aeroelastic divergence, flutter instabilities, and tail buffeting on fixed-wing aircraft; and reducing vibrations, improving external acoustics, and providing flight controls for rotating-wing aircraft - all of which require a high-frequency response. The status of some of the most promising developments is noted and the remaining problems are touched on. Two approaches, which have not been given substantial attention elsewhere, are reviewed; these are: developing concentrated, namely nondistributed, piezoelectric actuators in helicoidal configurations, on the one hand, as a way to improve force - deflection output; and using control surfaces purposefully designed to be marginally unstable and stabilized by smart structures, on the other hand, as a means of reducing the force - deflection combinations required of smart-structure actuators.

186 citations


Journal Article•DOI•
TL;DR: In this paper, the authors report on commonly used acoustic wave devices in sensor applications as well as the design techniques and fabrication processes, and a portable sensor array system is described, which allows for the integration of a total physical and chemical analysis system in the one IC package, leading to the evolution of smart sensors.
Abstract: Acoustic waves are currently being used in a wide range of sensor fields including physical sensing, chemical sensing and biosensing. Their implementation requires specific knowledge of materials, acoustic wave properties, device design and the sensing mechanisms involved for a wide range of applications. In this paper, the authors report on commonly used acoustic wave devices in sensor applications as well as the design techniques and fabrication processes. Sensing mechanisms and a portable sensor array system are described. The development of IC-based processes, thin-film deposition and sensitive layer fixation will allow for the integration of a total physical and chemical analysis system in the one IC package, leading to the evolution of smart sensors.

159 citations


Journal Article•DOI•
TL;DR: In this article, a nonlinear dynamic model is presented that characterizes electrorheological material behavior in terms of its shear stress versus shear strain behavior, which is represented by a simple network consisting of two parallel linear mechanisms whose outputs are combined using nonlinear weighting functions.
Abstract: A nonlinear dynamic model is presented that characterizes electrorheological material behavior in terms of its shear stress versus shear strain behavior. The ER fluid model is essentially a nonlinear combination of linear shear flow mechanisms. These linear shear flow mechanisms, a three-parameter viscoelastic fluid element and a viscous fluid element, are used to describe shear flow behavior in the pre-yield and the post-yield regimes, respectively. In order to capture the material behavior in the transition through the yield point, a nonlinear combination of these linear shear flow mechanisms is used. The model, which relates the shear strain input to the shear stress output, is represented by a simple network that consists of two parallel linear mechanisms whose outputs are combined using nonlinear weighting functions. The weighting functions are dependent on the strain rate in the material. A system identification technique is developed to estimate the model parameters from experimental data, which consists of shear stress versus shear strain hysteresis loops at different levels of electric field. The results of this system identification approach indicate that the model parameters are smooth monotonic functions of the electric field. The experimental hysteresis loops are reconstructed using the estimated model parameters and the results show that the model accurately predicts material response. It is shown that the Coulomb friction-like behavior at high field strengths, which is characteristic of ER fluids, can be captured by this nonlinear mechanism-based model.

157 citations


Journal Article•DOI•
TL;DR: In this paper, a novel linear actuator is presented, which exploits the electromechanochemical phenomena of -electron conjugated conducting polymers, occuring when ionic species are exchanged with the surrounding medium, i.e. solid or liquid electrolyte.
Abstract: The demand for actuators featuring biomimetic properties, such as linearity, high power density and compliance, is growing in microrobotics and bioengineering. In the present paper a novel linear actuator is presented. It exploits the electromechanochemical phenomena of -electron conjugated conducting polymers, occuring when ionic species are exchanged with the surrounding medium, i.e. solid or liquid electrolyte. In our experiments, a polypyrrole film doped with benzensulphonate anions is considered as the conducting polymer and a liquid electrolyte bath as the ionic reservoir. The actuating properties of the material are investigated and quantified in terms of both isotonic displacement and isometric developed force. A lumped parameter, muscle-like model of the system is proposed and verified with respect to the experimental data. The results of the electromechanical characterization and the goodness of fit of the model provide favourable indications for the utilization of the material as an effective muscle-like linear actuator, once the response time is decreased by means of a suitable scaling down of the film thickness.

142 citations


Journal Article•DOI•
TL;DR: In this article, a thermomechanical model is developed to predict the structural response of a flexible beam with shape memory alloy (SMA) wire actuators, which is used for shape control of active flexible structural systems.
Abstract: A thermomechanical model is developed to predict the structural response of a flexible beam with shape memory alloy (SMA) wire actuators. A geometrically nonlinear static analysis is first carried out to investigate the deformed shape of a flexible cantilever beam caused by an externally-attached SMA wire actuated electrically. The actuation force applied by the SMA actuator to the beam is evaluated by solving a coupled problem that combines a thermodynamic constitutive model of SMAs with the heat conduction equation in the SMA and the structural model of the beam. To calculate the temperature history of the SMA actuator for given electrical current input, the heat transfer equation is solved with the electrical resistive heating being modeled as a distributed heat source along the SMA wire. The steps in the formulation are connected together through an iterative scheme that takes into account the static equilibrium of the beam and the constitutive relation of SMAs, thus translating an electrical current history input into beam strain output. The proposed model is used to simulate the experimental results, thus demonstrating the feasibility of using SMA actuators for shape control of active flexible structural systems.

124 citations


Journal Article•DOI•
Jae-Hung Han, Keun-Ho Rew, In Lee1•
TL;DR: In this paper, an analytical model of the laminated composite beam with piezoelectric sensors and actuators has been developed using the classical laminated beam theory and Ritz method.
Abstract: In order to reduce the vibrational level of lightweight composite structures, active vibration control methods have been applied both numerically and experimentally. Using the classical laminated beam theory and Ritz method, an analytical model of the laminated composite beam with piezoelectric sensors and actuators has been developed. Smart composite beams and plates with surface-bonded piezoelectric sensors and actuators were manufactured and tested. It is found that the developed analytical model predicts the dynamic characteristics of smart composite plates very well. Utilizing a linear quadratic Gaussian (LQG) control algorithm as well as well known classical control methods, a feedback control system was designed and implemented. A personal computer (PC) was used as a controller with an analogue - digital conversion card. For a cantilevered beam the first and second bending modes are successfully controlled, and for cantilevered plates the simultaneous control of the bending and twisting modes gives a significant reduction in the vibration level. LQG has shown advantages in robustness to noise and control efficiency compared with classical control methods. In this study examples of control spillover are demonstrated via the instantaneous power spectrum of the sensor output.

108 citations


Journal Article•DOI•
TL;DR: In this paper, the authors used a polymer waveguide sensor to detect protein adsorption on the polymer surface from IgG solutions within the concentration range of 1 -. Radiolabelled IgG was applied to the device surface in order to calibrate the wave response to protein surface mass density.
Abstract: Love waveguide devices utilize shear-horizontal waves which propagate on the top layer of a coated SSBW acoustic device. Initially, attention was focused on the selection of a material which would effectively guide the Love wave. Silica and polymethyl methacrylate were used as guiding layers and the mass sensitivity of the corresponding sensors was tested in air. Low-shear-acoustic-velocity polymer overlayers were found to guide the Love wave most effectively with a maximum sensitivity of . The polymer waveguide sensor was further used to detect protein adsorption on the polymer surface from IgG solutions within the concentration range of 1 - . Radiolabelled IgG was applied to the device surface in order to calibrate the wave response to protein surface mass density. Finally, the effect of the acoustoelectric interaction on liquid-based applications was studied by utilizing a three-layer waveguide geometry. It was found that the evaporation of a 50 nm gold layer on the polymer overlayer can be used to eliminate acoustoelectric interactions without interfering with the Love wave propagation. After activation with protein A and IgG, the above system was used successfully to detect the direct binding of 400 ppb atrazine.

Journal Article•DOI•
TL;DR: In this paper, a smart structure was tested for active vibration control of frame structures in which the bending moment of the columns was controlled by stack-type piezoelectric actuators integrated into the columns.
Abstract: A smart structure was tested for active vibration control of frame structures in which the bending moment of the columns was controlled by stack-type piezoelectric actuators integrated into the columns. Excitation tests were carried out for a model of a four-storey building 3.7 m in height and 2000 kg in total weight in which thirty-two piezoelectric actuators were used for bending moment control. The actuators were installed in two ways: in one case eight actuators were attached to each column of the first storey, and in the other case four actuators were attached to each column of the first and second storeys. Two control strategies, a model-matching method and the control theory, were examined for the smart structure. The tests showed that the smart structure could effectively reduce the responses of the building model, and all combinations of actuator installation method and the control strategy yielded almost the same performance.

Journal Article•DOI•
TL;DR: In this article, real-time monitoring of fatigue damage and dynamic strain in a continuous unidirectional carbon fiber polymer-matrix composite by longitudinal electrical resistance measurement was achieved.
Abstract: Real-time monitoring of fatigue damage and dynamic strain in a continuous unidirectional carbon fiber polymer-matrix composite by longitudinal electrical resistance measurement was achieved The resistance R decreased reversibly upon tensile loading in every cycle, thus providing dynamic strain monitoring The peak R in a cycle irreversibly increased as fatigue damage occurred, due to fiber breakage Fiber breakage started to occur at 50% of the fatigue life, but significant growth of the fraction of fibers broken did not start till 55% of the fatigue life From 55% to 89% of the fatigue life, more than 1000 fibers broke at a time, but not in every cycle From 89% to 999% of the fatigue life, fiber breakage occurred continuously in every cycle Beyond 999% of the fatigue life, fiber breakage occurred rapidly, both continuously and in spurts, with the last spurt occurring at 9999% of the fatigue life Catastrophic failure occurred when 18% of the fibers were broken

Journal Article•DOI•
TL;DR: In this article, the stability of sandwich panels subjected to the simultaneous action of a uniform temperature and a uniaxial compression is considered, and the best results are achieved when the spacing of SMA fibers across the panel is nonuniform, i.e., the spacing which is minimum at the centerline, gradually increases with the approach to the edges (sinusoidal distribution).
Abstract: The stability of sandwich panels subjected to the simultaneous action of a uniform temperature and a uniaxial compression is considered. At elevated temperatures, the buckling load can be increased by using shape memory alloy (SMA) fibers in resin sleeves embedded within the core, at the midplane of the sandwich panel. The best results are achieved when the spacing of SMA fibers across the panel is nonuniform, i.e. the spacing, which is minimum at the centerline, gradually increases with the approach to the edges (sinusoidal distribution). The effectiveness of SMA fibers increases with temperature due to larger tensile recovery stresses. The example of stability of sandwich panels considered in the paper illustrates that functionally graded SMA composites may present significant advantages in engineering design.

Journal Article•DOI•
TL;DR: In this article, an experimental-analytical study on the active tuning of composite beams using shape memory alloy (SMA) wires was presented, which indicated that inserting 25 SMA wires of 20 mils diameter into a graphite - epoxy beam of 30 in length, 1 in width and 62 mils thickness increases its first frequency by 276%.
Abstract: This paper presents an experimental - analytical study on the active tuning of composite beams using shape memory alloy (SMA) wires. Two graphite - epoxy composite beams with embedded fused silica tubes (also called sleeves) with `dummy' steel wires inserted in the sleeves were manufactured using an autoclave molding technique. After curing, the `dummy' wires were replaced by pre-strained SMA wires. During testing of such a beam, the beam and SMA wire are independently clamped at both ends and the SMA wires are activated using electrical resistive heating. A large tensile recovery force develops in the wires due to a phase transformation and the mechanical constraints provided by the clamps. The influence of this recovery force on the vibration behavior of the composite beams was determined by vibration testing. Analytically, these beams with SMA wires inserted in embedded sleeves were examined as beams on an elastic foundation; the spring constant of the elastic foundation depended on the axial recovery force of the SMA wire. Good correlation between analysis and experiment was achieved. A numerical parametric study of natural frequencies of composite beams with activated SMA wires was conducted. The parameters considered were the diameter and the number of SMA wires. The numerical study suggests that inserting 25 SMA wires of 20 mils diameter into a graphite - epoxy beam of 30 in length, 1 in width and 62 mils thickness increases its first frequency by 276%.

Journal Article•DOI•
TL;DR: In this paper, two methods of producing the Love wave guiding layer were utilized to fabricate devices based on ST-cut quartz and spin coating of polymethylmethacrylate (PMMA) films.
Abstract: Love wave surface acoustic wave devices are very promising as sensors in gaseous and liquid environments because of their high sensitivity. In this work, two methods of producing the Love wave guiding layer were utilized to fabricate devices based on ST-cut quartz. The methods involved sputter deposition of silicon dioxide films and spin coating of polymethylmethacrylate (PMMA) films. -cut quartz devices with thicknesses up to and PMMA/ST-cut quartz devices with PMMA thicknesses up to have been manufactured and compared. Mass sensitivity, insertion loss, temperature coefficient of oscillation frequency and frequency noise have been studied as a function of layer thickness. A number of hybrid devices consisting of PMMA film/ film/ST-cut quartz have also been assembled and evaluated. These devices exhibit higher sensitivity than the devices and the PMMA devices produced here.

Journal Article•DOI•
TL;DR: In this paper, independent modal space control (IMSC) is adopted for vibration control of piezoelectric active structures and a set of modal sensors and actuators is proposed.
Abstract: Independent modal space control (IMSC) is adopted in this paper for vibration control of piezoelectric active structures. Single-mode controllability and observability conditions are presented. A set of modal sensors and actuators is proposed. Although they are to some extent approximate when compared to those developed previously, their design and application are much simpler. Numerical results are shown to illustrate the feasibility of the approximate modal sensors and actuators.

Journal Article•DOI•
TL;DR: In this article, a load line equation is developed that relates the free strain with the mechanical stress experienced by the magnetostrictive particles, and a macroscopic behavior model of a MPA is developed to find the orientation factor and pre-stress.
Abstract: Magnetostrictive particulate actuators (MPAs) that take advantage of easy embedability and remote excitation capability of magnetostrictive particles are proposed as new actuators for smart structure applications. A MPA is configured as a small rectangular polymeric beam with magnetostrictive particles dispersed uniformly. Based on the compatibility condition, a load line equation is developed that relates the free strain with the mechanical stress experienced by the magnetostrictive particles. The load line equation and the magnetoelastic property of the material are used to develop a macroscopic behavior model of a MPA. Characterization experiments are used to find the orientation factor and pre-stress. Experimental work shows that the static performance of MPAs for an applied magnetic field depends on the volume fraction, orientation field, mechanical preload, and the stiffness of the polymeric matrix. In general this actuator can be used where the structure needs to be excited with a large force and small strain over a wide frequency range. For example, embedded in a laminated composite, MPAs can be used as micropositioners, vibration dampers, platform stabilizers, and motors.

Journal Article•DOI•
TL;DR: In this paper, the authors deal with advances in surface acoustic wave (SAW) sensor research relating to the use of both a new chemically interactive material (metal porphyrin) and new amplifiers for low-noise SAW oscillators.
Abstract: This paper deals with some advances in surface acoustic wave (SAW) sensor research relating to the use of both a new chemically interactive material (metal porphyrin) and new amplifiers for low-noise SAW oscillators, which are illustrated and discussed in some detail. The trend toward SAW matrixes, implemented on silicon, required for more sensitive chemical image systems, has led to the observation of coupling effects between adjacent SAW oscillators, even if the electronics were not implemented on Si. This effect must be considered at design level in order to achieve a higher resolution value in detecting either single chemical species or chemical images.

Journal Article•DOI•
TL;DR: In this paper, a novel design for a large bending actuator is presented for the first time, which is composed of three components: an inner flexible beam or strip, a nickel - titanium shape memory alloy (SMA) contractile wire, and an outer soft plastic tube.
Abstract: A novel design for a large bending actuator is presented for the first time. It is composed of three components: an inner flexible beam or strip, a nickel - titanium shape memory alloy (SMA) contractile wire, and an outer soft plastic tube. The SMA wire is embedded between the beam and the plastic tube, and connected to the beam only at both ends of the beam. With this structure, a small change in the strain of the SMA wire results in a large bending deformation of the beam. To predict the behavior of the actuator, a mathematical model and a numerical simulation approach are then developed. The Brinson model for SMAs with constant material functions is used for modeling of the SMA wire component. The model of the actuator structure is associated with geometric nonlinearity of the large deflection beam and hysteretic nonlinearity of the SMA wire. A Galerkin finite-element formulation and an iterative procedure are used in the development of the numerical approach. A prototype of the actuator is made. Experimental observation on the shape change of the prototype with temperature change agrees with the numerical simulation result. This shows that the numerical approach developed in this paper is capable of providing a reasonable prediction for the behavior of the proposed large bending actuator.

Journal Article•DOI•
TL;DR: In this article, a thermodynamics-based domain switching criterion is proposed to govern domain switching in quasi-static processes in polycrystalline ferroelectric ceramics, where each grain is modeled as a mixture, consisting of distinct types of domains which are characterized by their mass fractions as internal variables.
Abstract: This paper is concerned with the modeling of domain switching in polycrystalline ferroelectric ceramics. In the present analysis, each grain is modeled as a mixture, consisting of distinct types of domains which are characterized by their mass fractions as internal variables. Domain switching corresponds to changes of mass fractions of the corresponding domains, and the driving force of domain switching is the difference in Gibbs' energies. A thermodynamics-based criterion is proposed to govern domain switching in quasi-static processes. Some numerical results for an idealized one-dimensional ferroelectric system are included to illustrate the polycrystalline effect on the grain-level electric field distribution and the polarization response to applied electric fields.

Journal Article•DOI•
TL;DR: In this article, a quasi-static variational principle and finite-element scheme are used to model the nonlinear interactions between mechanical and magnetic fields in magnetostrictive materials, incorporating both types of nonlinearity mentioned above.
Abstract: Materials such as Terfenol-D that are capable of giant magnetostriction are increasingly being used for sensing and actuation in active and adaptive structures. Designers of such adaptive structures need robust analytical and modeling tools for solving coupled electro-magneto - mechanical boundary value problems. While linear piezoelectric analysis is a standard feature of several general-purpose commercial finite-element codes, there are fewer tools for addressing the strong nonlinearities inherent in this class of problems. Electro-magneto - mechanical interactions manifest themselves not only through constitutive nonlinearities, but also through nonlinear terms in the governing equations. There have been recent works to deal with the constitutive nonlinearities in electrostriction and piezoelectricity, but a general computational framework for the comprehensive treatment of both these types of nonlinearity in magnetostrictives has not yet been developed. This paper presents a quasi-static variational principle and finite-element scheme to model the nonlinear interactions between mechanical and magnetic fields in magnetostrictive materials, incorporating both types of nonlinearity mentioned above. The basis of the finite-element scheme is presented here and applied to simulation of the actuation response of two actuator configurations. While the nonlinear scheme developed is of general three-dimensional nature, the application examples utilize material property data that pertain to the crystalline and geometrical symmetry of commercially produced Terfenol-D.

Journal Article•DOI•
TL;DR: In this article, a three-dimensional finite element model was developed for analyzing the response of active damping structures to steady state input in a closed loop, which indicated the significant and broad band attenuation capability of piezoelectric sensors and actuators.
Abstract: This is the first attempt at closed loop numerical simulation in the frequency domain using control theory and detailed finite element modeling of a smart structure with embedded piezoelectric sensors and actuators. A three-dimensional finite element model is developed for analysing the response of active damping structures to steady state input in a closed loop. Control authority resulting from charge or voltage as the active control force applied to the actuator are studied for the first two modes of vibration of a flexible beam. Comparison between constant velocity feedback control and constant displacement feedback control is also investigated. By applying an appropriate feedback control using the voltage generated by the piezoelectric sensor, substantial reduction of the resonance amplitude peaks of the cantilever beam is obtained. Numerical results are present which indicate the increase in damping as the feedback gain is increased. The results obtained clearly demonstrate the significant and broad band attenuation capability of piezoelectric sensors and actuators. A major advantage of active damping is to reduce the resonance peak without significantly altering the structural mass or stiffness.

Journal Article•DOI•
TL;DR: In this paper, the experimental results of wireless passive IDT strain microsensors, which consist of inter-digital transducers on piezoelectric wafers to transmit and receive surface acoustic waves, are presented.
Abstract: This paper presents the experimental results of wireless passive IDT strain microsensors, which consist of inter-digital transducers (IDTs) on piezoelectric wafers to transmit and receive surface acoustic waves. By connecting the IDTs to a small microwave antenna, the IDT microsensors are wirelessly readable by a microwave reading system. The sensors are calibrated on a static cantilever beam and used to measure the dynamic strain of a vibrating beam wirelessly. The calibrated sensitivity compares reasonably with the theoretical estimation. The feasibility of compensating for temperature variations and reading multiple sensors simultaneously and the ability to combine the sensor and the wireless recognition systems are discussed.

Journal Article•DOI•
TL;DR: In this article, the energy dissipation characteristics of active constrained layer damping (ACLD) treatments, consisting of visco-elastic cores constrained by active piezo-electric layers, are optimized using rational design procedures.
Abstract: The energy dissipation characteristics of active constrained layer damping (ACLD) treatments, consisting of visco-elastic cores constrained by active piezo-electric layers, are optimized using rational design procedures. The optimal lengths and control gains of these ACLD treatments are determined when a globally stable boundary control strategy is utilized to control the longitudinal strain of the active piezo-electric layers in response to the structural vibrations. The optimal parameters are obtained such that the sum of the passive and active loss coefficients of the ACLD treatments is maximized. The effect of the visco-elastic loss factor on the performance and the optimal parameters of the ACLD treatments is determined. Comparisons with optimal passive constrained layer damping (PCLD) indicate that the optimal ACLD is more effective in dissipating vibrational energy, particularly for visco-elastic cores with low-loss factors.

Journal Article•DOI•
TL;DR: In this paper, a robust vibration control of smart composite beams using neural networks was studied using linear quadratic Gaussian with loop transfer recovery (LQG/LTR) methodology.
Abstract: Robust vibration control of smart composite beams using neural networks was studied. Linear quadratic Gaussian with loop transfer recovery (LQG/LTR) methodology was used to design a robust controller on the basis of the state space model of the system. The state space model of the system was obtained using the finite-element method and mode superposition. The finite-element model was based on a higher-order shear deformation theory which included the lateral strains. The mode superposition method was used to transform the coupled finite-element equations of motion in the physical coordinates into a set of reduced uncoupled equations in the modal coordinates. The performance of the LQG/LTR controller was verified for various arbitrary initial conditions. A system of neural networks was then trained to emulate the robust controller. The neural network system was trained using the backpropagation algorithm. After suitable training, the NN (neural network) controller was shown to effectively control the vibrations of the composite beam. A robustness study including the effects of tip mass, structural parameter variation, and loss of a sensor input was performed. The NN controller is shown to provide robustness and control capabilities equivalent to that of the LQG/LTR controller.

Journal Article•DOI•
TL;DR: The development of an artificial urethral valve for the treatment of urinary incontinence which occurs frequently in the aged is described and experiments are conducted using a canine bladder and urinary canal.
Abstract: The development of an artificial urethral valve for the treatment of urinary incontinence which occurs frequently in the aged is described The prototype urethral valve is assembled in hand-drum form with four thin shape memory alloy (SMA) (nickel - titanium alloy) plates of 03 mm thickness The shape memory effect in two directions is used to replace the urinary canal sphincter muscles and to control the canal opening and closing functions The characteristic of the SMA is to assume the shape of a circular arc at normal temperatures and a flat shape at higher temperatures Experiments have been conducted using a canine bladder and urinary canal

Journal Article•DOI•
TL;DR: Several chemical sensing applications for surface acoustic wave (SAW) devices are described in this paper, including gas detection, thin-film polymer characterization, dew-point measurements, surface energy measurements, and a method to measure surface cleanliness.
Abstract: Surface acoustic wave (SAW) devices have been studied for the last twenty years as highly sensitive yet relatively inexpensive microsensors for applications ranging from temperature and stress to gas and biological sensing. This wide range of applications is due to the SAW microsensors' high sensitivity to several physical parameters including mass, temperature, stress, and conductivity. Their low cost results from the use of standard batch microelectronic fabrication techniques for their manufacture. In this paper several chemical sensing applications for SAW devices are described. These include: gas detection; thin-film polymer characterization; dew-point measurements; surface energy measurements; and as a method to measure surface cleanliness. Experimental results are presented along with comparisons to other measurement techniques.

Journal Article•DOI•
TL;DR: In this article, a theoretical analysis of the application of piezoceramic transducers to cantilever beam modal testing is presented, where the frequency response functions (FRFs) for the four pairs of sensors and actuators are derived and written in the conventional modal format.
Abstract: This paper presents a theoretical analysis of the application of piezoceramic transducers to cantilever beam modal testing. Four pairs of sensors and actuators, including accelerometer - point force, accelerometer - PZT, PVDF - point force and PVDF - PZT, are considered. The frequency response functions (FRFs) for the four pairs of sensors and actuators are first derived and written in the conventional modal format. The characteristics of modal parameters can thus be interpreted through the FRFs. A column of the FRF matrix can then be obtained based on the theoretical formulation. A curve-fitting algorithm is then applied to extract the modal parameters, such as natural frequencies, mode shapes and damping ratios. Results show that any sensor - actuator pair can successfully determine natural frequencies and damping ratios. Point types of transducer result in the displacement mode shapes, while piezoceramic transducers that are strip types and distributed in sense give the mode shapes of the slope difference between the edges of piezoceramic transducers. The paper provides the theoretical basis of applying piezoceramic transducers to experimental modal analysis and numerically supports the feasibility of cantilever beam modal testing using piezoceramic transducers.

Journal Article•DOI•
TL;DR: In this article, the integration of MEMS, SAW devices and required microelectronics and conformal antenna to realize a programmable wireless accelerometer is presented, which can be remotely sensed by a microwave system with the advantage of no power requirements at sensor site.
Abstract: The integration of MEMS, SAW devices and required microelectronics and conformal antenna to realize a programmable wireless accelerometer is presented in this paper. This unique combination of technologies results in a novel accelerometer that can be remotely sensed by a microwave system with the advantage of no power requirements at the sensor site. The microaccelerometer presented is simple in construction and easy to manufacture with existing silicon micromachining techniques. The relatively small size of the sensor makes it an ideal conformal sensor. The accelerometer can be used for applications such as air bag deployment sensors, vibration sensors for noise control, deflection and strain sensors, inertial and dimensional positioning systems, ABS/traction control, smart suspension, active roll stabilization and four wheel steering. The wireless accelerometer is very attractive to study the response of a `dummy' in automobile crash tests.