This PDF file contains the front matter associated with SPIE Proceedings Volume 6926, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

In urban combat environments where it is common to have unsupported firing positions, wobble significantly decreases shooting accuracy reducing mission effectiveness and soldier survivability. The SMASH (SMA Stabilizing Handgrip) has been developed to cancel wobble using antagonistic SMA actuators which reduce weight and size relative to conventional actuation, but lead to interesting control challenges. This paper presents the specification and design of the SMA actuation system for the SMASH platform along with experimental validation of the actuation and cancellation authority on the benchtop and on an M16 platform. Analytical dynamic weapon models and shooter experiments were conducted to define actuation frequency and amplitude specifications. The SMASH, designed to meet these, was experimentally characterized from the bounding quasi-static case up to the 3 Hz range, successfully generating the ±2 mm amplitude requirement. To effectively cancel wobble it is critical to produce the proper output functional shape which is difficult for SMA due to inherent nonlinearities, hysteresis, etc. Three distinct electrical heating input functions (square, ramp, and preheat) were investigated to shape the actuator output to produce smooth sinusoidal motion. The effect of each of these functions on the cancellation response of the SMASH applied to the M16 platform was experimentally studied across the wobble range (1-3 Hz) demonstrating significant cancellation, between 50-97% depending on the smoothing function and frequency. These results demonstrate the feasibility of a hand-held wobble cancellation device providing an important foundation for future work in overall system optimization and the development of physically based feed-forward signals for closed-loop control.

Complex signal processing functions can be performed by acoustic wave correlators, with simple structures, through the variation of electrode patterns. Numerical simulations of Surface Acoustic Wave (SAW) correlators, previously limited to analytical techniques like delta function and equivalent circuit models, require simplification of second order effects such as backscattering, charge distribution, diffraction, and mechanical loading. With the continual improvement in computing capacity, the adaptation of finite element modelling (FEM) is more eficient for full scale simulation of electromechanical phenomena without model oversimplification. This is achieved by resolving the complete set of partial differential equations. In this paper a novel way of modelling a 3-dimensional acoustic wave correlator using finite element analysis is presented. This modelling approach allows the consideration of different code implementation and device structures. This is demonstrated through the simulation results for a Barker sequence encoded acoustic wave correlator. The device response for various surface, bulk, and leaky modes, determined by the excitation frequency, are presented. Moreover, the ways in which the gain of the correlator can be optimised though variation of design parameters is also outlined.

The overall goal of the research conducted in this paper is to develop next generation force feedback systems by combining novel Magnetorheological (MR) fluid based systems with microstructural analysis and advanced control system design. A novel 5-DOF MR fluid-based robotic arm is designed and prototyped. The 5-DOF system is used to control a remote 5-DOF robot (the slave). Force feedback control is employed to replicate in the master those forces encountered in the slave.

In this paper we present the modeling and simulation of a 2 degree-of-freedom (DOF) bidirectional electrothermal actuator. The four arm microactuator was designed to move in both the horizontal and vertical axes. By tailoring the geometrical parameters of the design, the in-plane and out-of-plane motions were decoupled, resulting in enhanced mobility in both directions. The motion of the actuator was modeled analytically using an electro-thermo-mechanical analysis. To validate the analytical model, finite element simulations were performed using ANSYS. The microactuators were fabricated using PolyMUMPS process and experimental results show good agreement with both the analytical model and the simulations. We demonstrated that the 2-DOF bidirectional electrothermal actuator can achieve 3.7 μm in-plane and 13.3 μm out-of-plane deflections with an input voltage of 10 V.

Piezoelectric actuators used in nano-positioning devices exhibit highly non-linear behavior and strong hysteresis, which limits the efficiency of conventional non-model-based controllers. This paper presents the first results of a free energy model based on the theory of thermal activation for single crystal piezoceramics that couples mechanical stress and electric field. It is capable of predicting the hysteretic behavior along with the frequency-dependence present in these materials. The model is then coupled with a spring as a first step toward a SDOF model of a commercial nano-positioning stage and is the basis for future control applications. Quasi-static simulations are presented to illustrate the effects of spring loading on the actuator behavior.

A switching sliding mode controller for the static shape control of a membrane strip is considered. The membrane strip is augmented with two macro fiber composite (MFC) bimorphs. MFC patches are modeled as monolithic piezoceramics. The combined structure is modeled as an Euler-Bernoulli beam under tensile load. The two bimorphs are actuated independently. One bimorph operates in bending, whereas the other bimorph operates in tension. The presence of the later causes the system to be nonlinear, hence the use of the sliding mode technique, and gives rise to a structural singularity. To evade this problem, a switching command is introduced. Hence, the closed loop system utilizes a hybrid control law, which can cause stability problems. Fortunately, the same Lyapunov function can be used to analyze the stability of both subsystems. Consequently, the switching is safe, and asymptotic stability is guaranteed. Simulation results are presented to demonstrate the efficacy of the switching slide mode controller.

Many piezoelectric systems are operated in resonance, requiring some sort of control. Especially weakly damped systems need a control algorithm to hold the system in resonance. There are many factors, which can change the system's resonant frequency during operation. The two most important factors are load effects and temperature effects. A common algorithm to drive a piezoelectric system in its eigenfrequency is the PLL (phase-locked-loop) controller - well known from communication technologies - including some adaptive variantions of the PLL. Beside a brief introduction into the APLL (adaptive PLL, this paper concentrates on one of the main components of the (A)PLL, the phase detector. It investigates and compares different types of phase detectors with a focus on the implantation on a digital control system.

Sandwich structures consisting of contact-aided compliant mechanisms are presented for morphing aircraft skin. A contact mechanism is used to alleviate stresses and to decrease the out-of-plane deflection. A methodology to design such mechanisms, which takes into account the aerodynamic loads, is presented. The method is applied to a small UAV and results are compared with those of honeycomb structures in terms of structural mass, global strain and maximum stresses. Different material models such as linearly elastic and multi-linear elastic are considered. For linearly elastic materials, contact-induced stress-relief is advantageous and for nonlinear elastic materials, reduction of transverse deflection due to contact is useful. In either case, the structural mass of the contact-aided structures is less than that of the corresponding non-contact structures.

Due to their high stiffness, small dimensions and low mass, piezoelectric stack actuators are capable of developing large displacements with bandwidths of greater than 100 kHz. However, due to their large electrical capacitance, the associated driving amplifier is usually limited in bandwidth to a few kHz. In this paper the limiting characteristics of piezoelectric drives are identified as the signal-bandwidth, output-impedance, cable inductance, and power dissipation. A new dual-amplifier is introduced that exhibits a bandwidth of 2 MHz with a 100 nF capacitive load. Experiments demonstrate a 20 V 300 kHz sine wave being applied to a 100 nF load with negligible phase delay and a peak-to-peak current of 3.8 A. Although the peak output voltage and current is 200 V and 1.9 A, the worst-case power dissipation is only 30 W.

Smart materials display coupling between electrical, magnetic, thermal and elastic behavior. Hence these materials have inherent sensing and actuation capacities. However, the hysteresis inherent to smart materials presents a challenge in control of these actuators/sensors. Inverse compensation is a fundamental approach to cope with hysteresis, where one aims to cancel out the hysteresis effect by constructing a right inverse of the hysteresis. The performance of the inverse compensation is susceptible to model uncertainties and to error introduced by inexact inverse algorithms. We employ a mathematical model for describing hysteresis. On the basis of the hysteresis model, a robust adaptive inverse control approach is presented, for reducing hysteresis. The asymptotic tracking property of the adaptive inverse control algorithm is proved and the issue of parameters convergence is discussed in terms of the reference trajectory. Moreover, suficient conditions under which parameter estimates converge to their true values are derived. Simulations are used to examine the effectiveness of the proposed approach.

In this work, we propose an Adaptive Neuro Fuzzy Inference System (ANFIS) based hysteresis modeling and control strategy for a thin Shape Memory Alloy (SMA) wire. Controlling the SMA wire is a challenging problem because of its dynamic hysteretic behavior. By using a hybrid learning procedure ANFIS architectures are powerful tools for many applications, such as identifying nonlinear parameters in a controlled system, predicting chaotic time series and modeling nonlinear functions. We tested our ANFIS model by making it predict major and minor hysteresis loops in different driving frequencies and compared them with the experimental data. To compensate the hysteretic effect, we used an inverse ANFIS model and used it directly as a controller. After dramatically reducing the hysteretic effect, we implemented a PI control to fine tune the response.

Prediction of scatter on the mechanical behavior of metallic materials due to microstructural heterogeneity is important, particularly for damaged metallic structures, where degradation mechanisms such as fatigue can be very sensitive to microstructure variability, which is also a contributing factor to the scatter observed in the fatigue response of metallic materials. Two-dimensional (2D) and Three-dimensional (3D) representations of microstructures of 2xxx Al alloys are created via a combination of dual-scale serial sectioning techniques, with a smaller scale for particles and a larger scale for grains, Electron Backscattering Diffraction (EBSD) and available meshing and volume reconstruction software. In addition, "artificial" representations of the grains are also built from measurements of the crystallography and the geometry of the grains in representative cross sections of the samples. These measurements are then used to define a Representative Volume Element (RVE) with mechanical properties that are comparable to those in larger length scales, via simulations performed using finite element models of the RVE. In this work, the characteristics of the RVE are varied by introducing changes on either geometry, material properties or both and by "seeding" defects that represent damage (microcraks) or damage precursors (precipitates). Results indicate that models obtained predict the variability on stress fields expected at the local level, due to crystallographic and geometric variability of the microstructure.

This paper formulates a stochastic model of fatigue crack growth in ductile alloys under variable loading of the center wing type. This center wing loading has three different load ratios to depict the most demanding operating conditions. The cumulative distribution function of the crack length estimate is generated by numerically solving a stochastic differential equation describing the physics of the crack growth. The model parameters are obtained by analyzing each load span, and the variable model parameter is used in the corresponding load period. Simulations are used to show that the analytical crack exceedance probability follows the experimental data fairly well.

We have recently proposed a method for classifying waveforms from healthy and damaged structures in a structural health monitoring framework. This method is based on the use of hidden Markov models with preselected feature vectors obtained from the time-frequency based matching pursuit decomposition. In order to investigate the performance of the classifier for different signal-to-noise ratios (SNR), we simulate the response of a lug joint sample with different crack lengths using finite element modeling (FEM). Unlike experimental noisy data, the modeled data is noise free. As a result, different levels of noise can be added to the modeled data in order to obtain the true performance of the classifier under additive white Gaussian noise. We use the finite element package ABAQUS to simulate a lug joint sample with different crack lengths and piezoelectric sensor signals. A mesoscale internal state variable damage model defines the progressive damage and is incorporated in the macroscale model. We furthermore use a hybrid method (boundary element-finite element method) to model wave reflection as well as mode conversion of the Lamb waves from the free edges and scattering of the waves from the internal defects. The hybrid method simplifies the modeling problem and provides better performance in the analysis of high stress gradient problems.

We describe a statistical method for the classification of damage in complex structures. Our approach is based on a Bayesian framework using hidden Markov models (HMMs) to model time-frequency features extracted from structural data. We also propose two different methods for sensor fusion to combine information from multiple distributed sensors such that the overall classification performance is increased. The proposed approaches are applied to the classification and localization of delamination in a laminated composite plate. Results using both discrete and continuous observation density HMMs, together with the sensor fusion, are presented and discussed.

This paper presents the use of guided wave concept in localizing small cracks in complex lug joint structures. A lug joint is a one of the several 'hotspots' in an aerospace structure which experiences fatigue damage. Several fatigue tests on lug joint samples prepared from 0.25" plate of Aluminum (Al) 2024 T351 indicated a distinct failure pattern. All samples failed at the shoulders. Different notch sizes are introduced at the shoulders and both virtual and real active health monitoring with piezoelectric transducers is performed. Simulations of the real time experiment are carried out using Finite Element (FE) analysis. Similar crack geometry and piezoelectric transducer orientation are considered both in experiment and in simulation. Results presented illustrate the use of guided waves in interrogating damage in lug joints. A comparison of sensor signals has been made between experimental and simulated signals which show good correlation. The frequency transform on the sensor signal data yield useful information for characterizing damage. Further, sensitivity studies are performed. The sensitivity study information offers potential application in reducing the computational cost for any defect localization technique by reducing redundant sensors. This information is a key to optimal sensor placement for damage detection in structural health monitoring (SHM).

We investigate the use of low frequency (10-70 MHz) laser ultrasound for the detection of fatigue damage. While high frequency ultrasonics have been utilized in earlier work, unlike contacting transducers, laser-based techniques allow for simultaneous interrogation of the longitudinal and shear moduli of the fatigued material. The differential attenuation changes with the degree of damage, indicating the presence of plasticity. In this paper, we describe a structural damage identification approach based on ultrasonic sensing and time-frequency techniques. A parsimonious representation is first constructed for the ultrasonic signals using the modified matching pursuit decomposition (MMPD) method. This decomposition is then employed to compute projections onto the various damage classes, and classification is performed based on the magnitude of these projections. Results are presented for the detection of fatigue damage in Al-6061 and Al-2024 plates tested under 3-point bending.

Research is being conducted in damage diagnosis and prognosis to develop state awareness models and residual useful life estimates of aerospace structures. This work describes a methodology using Support Vector Machines (SVMs), organized in a binary tree structure to classify the extent of a growing crack in lug joints. A lug joint is a common aerospace 'hotspot' where fatigue damage is highly probable. The test specimen was instrumented with surface mounted piezoelectric transducers and then subjected to fatigue load until failure. A Matching Pursuit Decomposition (MPD) algorithm was used to preprocess the sensor data and extract the input vectors used in classification. The results of this classification scheme show that this type of architecture works well for categorizing fatigue induced damage (crack) in a computationally efficient manner. However, due to the nature of the overlap of the collected data patterns, a classifier at each node in the binary tree is limited by the performance of the classifier that is higher up in the tree.

This paper presents optimization of active, passive, and hybrid damping treatments in sandwich plates. A new mixed layerwise finite element model has been developed for the analysis of sandwich laminated plates with a viscoelastic core, laminated anisotropic face layers and piezoelectric sensor and actuator layers. Proportional displacement and velocity feedback control laws are implemented to account for co-located active control. Optimization of passive damping is conducted by maximizing modal loss factors, using as design variables the viscoelastic core thickness and the constraining elastic layers ply thicknesses and orientation angles. Optimization of the location of co-located sensor-actuator pairs is also conducted in order to maximize modal loss factors. The optimization problem is solved using gradient-based techniques for passive damping and an implementation of a Genetic Algorithm for the optimal location of sensor-actuator pairs.

In this paper we present an efficient method to calculate the thermal conductance in a thermally isolated microplate, connected to the substrate by two thin arms. The method can be applied to uncooled microbolometer pixels which in general, incorporate a thermally isolated microplate. The model approximates the microplate as a two-region slab, where heat flows in one direction. The thermal resistance that results from the constriction of the heat flux lines is added to the model as thermal contact resistance. To evaluate the model, two microplates having different dimensions were fabricated using PolyMUMPs. The experimental results are compared to the proposed model and finite element simulations. It is shown that for the tested structures, the maximum discrepancy in thermal conductance between our model and the experiments is 6%, compared to the ~22% discrepancy found using conventional models. It is concluded that the method is very effective in thermal modeling of microplates and it is applicable to uncooled microbolometer pixels.

Paper presents preliminary findings on porting the Mueller-Achenbach-Seelecke model for the constitutive behavior of shape memory alloys into the finite-element-program ABAQUS. Means to doublecheck the current status of the implementation are traced out and the need for thermomechanical coupling in modeling shape memory alloys is demonstrated.

Plates, with many applications, can be classified into membranes, thin plates, and thick plates based on different aspect ratios of the hydraulic diameter to the plate's thickness. The existing nonlinear models for circular membranes and thin plates are reviewed. It is desirable to have analytical or approximate analytical models for the nonlinear deflections, strains, and stresses of membranes because of their maneuverable and insightful forms albeit the available numerical solutions. The new nonlinear models for prestretched and post-heated circular membranes under uniform pressure by both the Ritz method and the Galerkin method have been derived. The new nonlinear membrane model has been validated and compared to other related existing models. Furthermore, the condition of the pre-tensioned stress to minimize the maximum equivalent stress of membranes has been obtained. The solutions for thin plates have also been extended to include pretension and post-heating. The truncation error of the stretching factor of thin plates is corrected. For circular membranes and thin plates, both the Ritz method and the Galerkin method give the same answer if both the radial and axial displacements derived from the Galerkin method are used. The computer software MATLAB has also been used to verify the derivations of new membrane and thin plate models.

Devices composed of nanoelectromechanical systems (NEMS) possess distinguished properties which make them quite suitable for a variety of applications including ultra-high-frequency (UHF) resonators. However, most GHz resonators have low quality factor even though it has been well above 10³ ~ 10⁵ for very-high-frequency (VHF) microresonators. The motivation for our investigation of single crystal silicon nanoresonator arises from both its technological importance and its extraordinary surface effects. Our simulation results show that the quality factor decreased in a nearly linear manner as the surface area to volume ratio (SVR) was increased, which suggests that surface losses play a significant role in determining the quality factor of nanoresonators.

Piezoelectric polymers have lossy and dispersive dielectric properties and exhibit higher viscoelastic losses. Due to their lossy behavior, the lossy models developed for piezoceramics are insufficient for evaluating polymers. In this work we present a novel SPICE implementation of piezoelectric polymers model which includes the mechanical, electromechanical and dielectric losses. The mechanical/viscoelastic, dielectric/electrical and piezoelectric/electromechanical losses have been included in the model by using complex elastic, dielectric and piezoelectric constants - obtained from measured impedance of PVDF-TrFE sample. The simulated impedance and phase plots of polymer, working in thickness mode, have been compared with measured data. The impedance and phase plots have also been compared with those obtained by using the lossy model approaches reported earlier.

The performance of ferroelectric random access memory devices (FeRAM) relies on the remnant polarisation. For high performance, the remnant polarisation of a ferroelectric thin film memory capacitor is desired to be as great as possible. However, the remnant polarisation in thin film form is typically only a third to a half of its bulk value. The coercive field is also several times greater in a thin film than in its bulk counterpart. A theoretical work is carried out in this study to explore the roles played by substrate and ferroelectric properties in altering the remnant polarisation. A constitutive law based on the crystal plasticity theory and the finite element method are used to model the ferroelectric switching behavior of a memory capacitor. In particular, it is found that factors such as crystallographic orientation and the initial volume fractions of ferroelectric variants, that are dependent on the type of substrate and film deposition method, can significantly alter the achievable remnant polarisation. An explanation of these dependencies is given, suggesting approaches to the problem of increasing the remnant polarisation of a thin film memory capacitor.

Dielectric elastomers (Des) are a type of EAPs with unique electrical properties and mechanical properties: high actuation strains and stresses, fast response times, high efficiency, stability, reliability and durability. The excellent figures of merit possessed by dielectric elastomers make them the most performing materials which can be applied in many domains: biomimetics, aerospace, mechanics, medicals, etc. In this paper, we present a kind of electroactive polymer composites based on silicone Dielectric elastomers with a high dielectric constant. Novel high DEs could be realized by means of a composite approach. By filling an ordinary elastomer (e.g. silicone) with a component of functional ceramic filler having a greater dielectric permittivity, it is possible to obtain a resulting composite showing the fruitful combination of the matrix's advantageous elasticity and the filler's high permittivity. Here we add the ferroelectric relaxor ceramics (mainly BaTiO3) which has high dielectric constant (>3000) to the conventional silicone Dielectric elastomers, to get the dielectric elastomer which can exhibit high elastic energy densities induced by an electric field of about 15 MV/m. Tests of the physical and chemical properties of the dielectric elastomers are conducted, which verify our supposes and offer the experimental data supporting further researches.

An experimental setup is designed and fabricated to measure the force induced by voltage in an SMA wire. Using autoregressive model with exogenous input (ARX) method for system identification of the experimental data, two appropriate transfer functions of the force in SMA wire versus the applied voltage during each of heating and cooling processes were derived. Afterwards, a conventional PID controller and a self-tuning fuzzy PID controller were designed to control the force in SMA wire. The latter control algorithm is used by tuning the parameters of the PID controller thereby integrating fuzzy inference and producing a fuzzy adaptive PID controller, which is used to improve the force control performance. The responses of the system with the both designed controllers for different inputs are simulated and compared to each other. At the end, simulation results show that in force control of the SMA wire, self-tuning fuzzy PID controllers are more efficient than conventional PID controllers.

In this paper the vibration suppression of a flexible structure using fuzzy controller with bonded piezoelements is investigated. A flexible beam with PZT piezoceramics as sensor and actuators is fabricated at the Advanced Dynamic and Control Systems lab (ADCSL). A dynamic model of the smart structure is derived from an experimental system ID. On the other hand using finite element method (FEM), a theoretical model of the structure is obtained which is in good agreement with the experimental model. A fuzzy control system is then designed and implemented for vibration suppression of the smart beam subjected to the impulse excitation and resonance disturbances. Results show the effectiveness of the fuzzy controller and its advantage over conventional controllers.

In the last few years both the fundamentals and the materials have significantly changed in the design of engineering structures. In space structures, for example, metallic components have been intensely replaced by composite and fiber made ones to reduce weight and increase transportation and assembling skills. Impedance-based Structural Health Monitoring is a major concern in this context because different types and categories of damage can affect various areas along the structure. The interpretation of damage signatures is an important challenge to be overcome. As a consequence, erroneous damage identification is quite common. This contribution focus on damage prediction in a tubular space structure by using a methodology that is able to reduce the possibility of misinterpretation in the monitoring procedure. For this aim, an optimization technique using genetic algorithms is applied to the complete damage signature to determine the best frequency range to be investigated in each problem. Then, a meta-model is built to characterize damage in the structure.

It takes much more time for us to read the information of high resolution image. When the object section that we are interested in is high bright image elements in the image and has the line property, the best way to descript it is to use a line segment. The previous image compress technologies including nearest neighbor, bilinearity and bicubic, etc., are designed to adapt the general image and has the satisfaction effect in whole. But sometimes they compress a line to a dot-line. It brings trouble to read the real information of the image. In this paper, we present a new method - maximum extraction based on block segmentation to compress image and it keeps the line property well. Because the maximum extraction improve the average value of the extract image, it looks more bright than the original image, then we use grey transform to change the brightness of the image to make it close to the original image. Through many experiments, it is proved very effect to help us recognize the road and some other high bright objects with line property.

In this paper we describe the architecture and the performances of a hybrid modular acquisition and control system prototype for environmental monitoring and geophysics. The system, an alternative to a VME-UDP/IP based system, is based on a dual-channel 18-bit low noise ADC and a 16-bit DAC module at 1 MHz. The module can be configured as stand-alone or mounted on a motherboard as mezzanine. Both the modules and the motherboard can send/receive the configuration and the acquired/correction data for control through a standard EPP parallel port to a standard PC for the real-time computation. The tests have demonstrated that a distributed control systems based on this architecture exhibits a delay time of less than 25 us on a single channel, i.e a sustained sampling frequency of more than 40 kHz (and up to 80 kHz). The system is now under extensive test in the remote controls of seismic sensors (to simulate a geophysics networks of sensors) of a large baseline suspended Michelson interferometer.

The magnet-coil was used for a passive eddy current damper and an electromagnetic actuator to suppress the vibration of cantilever beams. The magnet-coil system consists of a copper coil attached to the aluminum beam and a permanent magnet installed below the coil, and this conductive coil can be used passively and actively as a damper and an actuator. The effect of the coil shapes including a cylindrical tube, a square tube and a circular sheet was investigated to find an efficient magnet-coil system for the vibration suppression of the cantilever beams. Also, the results of the active control with a positive position feedback scheme were compared with those of the passive eddy current dampers with open and closed circuits. The experimental data showed that the tube type coils had much higher vibration suppression efficiency than the sheet type coil and the active vibration control strategy can be alternatively used to improve the electromagnetic damper system.