This PDF file contains the front matter associated with SPIE Proceedings Volume 6523, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.

In this paper, recent efforts conducted to analyze the dynamic behavior of a biology-inspired miniature directional microphone are presented. Inspired by the tiny ears of the fly Ormia, the proposed directional microphone consists of two circular diaphragms coupled by a beam. The numerical study has shown that the biology-inspired directional microphone enables the amplification of the time delay between the sound pressure induced displacement responses of the two diaphragms. Factors such as the beam stiffness and the air backed cavity, which influence the performance of the directional microphone, are investigated. These analyses and results are expected to be valuable for the development of biology-inspired miniature directional microphones for various applications.

While good marksmanship is the key to the effectiveness of the infantry mission, all soldiers experience a decrease in accuracy due to combat stress that generates detrimental physiological effects. INSTAR is a tactical rifle designed to address these effects by decoupling unwanted shooter-induced disturbances from the barrel via an active suspension system. Previous papers have addressed the design of the active suspension system: the actuation, driving electronics and power supply. In this paper we consider the development of the jitter control system. Beginning with an analytical model of the gun that includes the shooter, we develop the appropriate model for the design of the control system. We investigate two designs. The first design is based on lead compensation. The second design is based on LQG. Both designs show that the control system can effectively reduce the jitter to acceptable levels. The classical compensator demonstrates better transient performance.

Due to physiologically induced body tremors, there is a need for active stabilization in many hand-held devices such as surgical tools, optical equipment (cameras), manufacturing tools, and small arms weapons. While active stabilization has been achieved with electromagnetic and piezoceramics actuators for cameras and surgical equipment, the hostile environment along with larger loads introduced by manufacturing and battlefield environments make these approaches unsuitable. Shape Memory Alloy (SMA) actuators are capable of alleviating these limitations with their large force/stroke generation, smaller size, lower weight, and increased ruggedness. This paper presents the actuator design and quasi-static characterization of a SMA Stabilizing Handgrip (SMASH). SMASH is an antagonistically SMA actuated two degree-of-freedom stabilizer for disturbances in the elevation and azimuth directions. The design of the SMASH for a given application is challenging because of the difficulty in accurately modeling systems loads such as friction and unknown shakedown SMA material behavior (which is dependent upon the system loads). Thus, an iterative empirical design process is introduced that provides a method to estimate system loads, a SMA shakedown procedure using the system loads to reduce material creep, and a final selection and prediction for the full SMASH system performance. As means to demonstrate this process, a SMASH was designed, built and experimentally characterized for the extreme case study of small arms stabilization for a US Army M16 rifle. This study successfully demonstrated the new SMASH technology along with the unique design procedure that can be applied to small arms along with a variety of other hand-held devices.

Morphing structures for applications such as impact mitigation is a challenging problem due to the speed and repeatability requirements that limit the viable actuation approaches. This paper examines a promising stored-energy, active-release approach that can be deployed quickly (~40 ms), is reusable/resetable and can be tuned in the field for changing conditions such as additional mass, temperature compensation or platform changes. The Dual-Chamber SMART (SMA ReseTtable) Lift is a pneumatic air spring controlled via an ultra-fast SMA actuated valve. This paper presents the modeling, sensitivity analysis and experimental validation of this new technology. A control-volume based analytical model was derived that employs compressible, sonic flow and thermodynamic relations to provide a set of differential equations that relate the design parameters (cylinder and valve geometry), application parameters (deployed mass), and operational parameters (pressure, temperature and SMA valve actuation profile), to the deployment performance (deploy time, profile, position, etc.). The model was exercised to explore the sensitivity of the performance with regards to these parameters and explore the off-line and on-line adjustability of the device's performance to compensate for cross platform applications and uncontrolled environmental effects such as temperature and added mass. As proof-of-concept, a full-scale prototype was designed via the model, built and experimentally characterized across several of the parameters for the real case-study of automotive pedestrian protection. The prototype performance agreed closely with model predictions and met the rigorous specifications of the case study with in-situ tailoring which is applicable to a wide range of morphing applications beyond this case study.

Robotic fish is an interesting and prospective subject to develop. The simplest fish swimming mode to be mimicked for fish robots is the ostraciiform mode which only requires caudal fin flapping. An almost submerged ostraciiform fish robot was constructed to study its swimming characteristics. The swimming direction can be controlled by changing the mean angle of caudal fin oscillation. Experiments were conducted to study the behavior of the fish robot and in particular, the transfer function between swimming path angular rate and mean angle of the caudal fin oscillation were identified. Error to signal ratio quantity was used to determine how well the model fits with the experimental data. This identification model was used to design a 2-degree-of-freedom PID controller that meets some specific requirements to improve the steering performance.

Morphing aircraft wings offer great potential benefits of achieving multi mission capability as well as high maneuverability under different flight conditions. However, they present many design challenges in the form of conflicting design requirements. The current research aims to develop design methodologies for the design of a morphing aircraft wing. Focus of this work is on developing an internal mechanism of the wing that can produce the desired wing shape change. This paper presents a design methodology that employs planar unit cells of pre-determined shape and layout as the internal wing structure for achieving the desired wing shape change. This method is particularly useful in cases where the desired morphing is two-dimensional in nature. In such cases, intuitive cell designs such as diamond or hexagonal shaped cells may be used in layouts that achieve desired wing morphing. The shape change depends on the cell shape as well as cell arrangement in the design domain. In this paper, a design based on the TSCh wing (NextGen Aeronautics Inc.) using cellular mechanisms to achieve a two-dimensional wing shape change is discussed. Additionally, a reeling mechanism for achieving cable actuation is presented

Aircraft are often confronted with distinct circumstances during different parts of their mission. Ideally the aircraft should fly optimally in terms of aerodynamic performance and other criteria in each one of these mission requirements. This requires in principle as many different aircraft configurations as there are flight conditions, so therefore a morphing aircraft would be the ideal solution. A morphing aircraft is a flying vehicle that i) changes its state substantially, ii) provides superior system capability and iii) uses a design that integrates innovative technologies. It is important for such aircraft that the gains due to the adaptability to the flight condition are not nullified by the energy consumption to carry out the morphing manoeuvre. Therefore an aeroelastic numerical tool that takes into account the morphing energy is needed to analyse the net gain of the morphing. The code couples three-dimensional beam finite elements model in a co-rotational framework to a lifting-line aerodynamic code. The morphing energy is calculated by summing actuation moments, applied at the beam nodes, multiplied by the required angular rotations of the beam elements. The code is validated with NASTRAN Aeroelasticity Module and found to be in agreement. Finally the applicability of the code is tested for a sweep morphing manoeuvre and it has been demonstrated that sweep morphing can improve the aerodynamic performance of an aircraft and that the inclusion of aeroelastic effects is important.

This paper discusses modeling, simulations and experimental aspects of active aeroelastic control on aircraft wings by using Synthetic Jet Actuators (SJAs). SJAs, a particular class of zero-net mass-flux actuators, have shown very promising results in numerous aeronautical applications, such as boundary layer control and delay of flow separation. A less recognized effect resulting from the SJAs is a momentum exchange that occurs with the flow, leading to a rearrangement of the streamlines around the airfoil modifying the aerodynamic loads. Discussions pertinent to the use of SJAs for flow and aeroelastic control and how these devices can be exploited for flutter suppression and for aerodynamic performances improvement are presented and conclusions are outlined.

Results from experimental studies on the performance of plasma and synthetic jet actuators for active control of flow over a circular cylinder in subcritical flow conditions ranging from a Reynolds Number of 2.5 x 10⁴ to 7.3x10⁴ are presented. The experiments were conducted at the NASA Langley Research Center in the 20" x 28" Shear Flow Wind Tunnel and the results provide an indication of the effectiveness of, as well as the similarities and differences between these two active flow control (AFC) methods for reducing pressure drag on a bluff body shape. Flows over a cylinder are well understood and in particular flow separation characteristics for cylinders are well documented both experimentally and theoretically. The effect of the flow control devices is quantified by measuring the pressure distribution around the bluff bodies using a multi-port piezoelectric pressure scanner and integrating the distribution for drag analysis. This comparison consists of operating the two types of actuators in the same range of Reynolds Numbers (Re) over the cylinder and for the same actuator angular positions on the cylinder. The applied voltages and frequencies to the actuators varies based on the individual actuator operating conditions. At low Re, the plasma actuators have a strong effect on the pressure distribution reducing the drag up to 32% relative to the drag with no actuators on the surface. The synthetic jet reduces drag up to 25% but with lower voltage and frequency. For both actuator cases, the actuator is the most effective 5° to 10° upstream of the baseline separation point.

Resonance tracking control of harmonic oscillators whose natural frequency is unknown is investigated from a Lyapunov stability perspective. In particular, a periodically-modulated cosine driver (PMCD) is investigated for this purpose. The proposed resonance tuner is time-synchronized with periodic sampling of the harmonic oscillator's output to ensure that an analytical relationship exists between the drive frequency and the tracking error. This relation defines a class of discrete time nonlinear systems whose origin, is shown to be asymptotically stable.

Functionally Graded Materials (FGMs) possess continuous variation of material properties and are characterized by spatially varying microstructures. Recently, the FGM concept has been explored in piezoelectric materials to improve properties and to increase the lifetime of piezoelectric actuators. Elastic, piezoelectric, and dielectric properties are graded along the thickness of a piezoceramic FGM. Thus, the gradation of piezoceramic properties can influence the performance of piezoactuators, and an optimum gradation can be sought through optimization techniques. However, the design of these FGM piezoceramics are usually limited to simple shapes. An interesting approach to be investigated is the design of FGM piezoelectric mechanisms which essentially can be defined as a FGM structure with complex topology made of piezoelectric and non-piezoelectric material that must generate output displacement and force at a certain specified point of the domain and direction. This can be achieved by using topology optimization method. Thus, in this work, a topology optimization formulation that allows the simultaneous distribution of void and FGM piezoelectric material (made of piezoelectric and non-piezoelectric material) in the design domain, to achieve certain specified actuation movements, will be presented. The method is implemented based on the SIMP material model where fictitious densities are interpolated in each finite element, providing a continuum material distribution in the domain. The optimization algorithm employed is based on sequential linear programming (SLP) and the finite element method is based on the graded finite element concept where the properties change smoothly inside the element. This approach provides a continuum approximation of material distribution, which is appropriate to model FGMs. Some FGM piezoelectric mechanisms were designed to demonstrate the usefulness of the proposed method. Examples are limited to two-dimensional models, due to FGM manufacturing constraints and the fact that most of the applications for such FGM piezoelectric mechanisms are planar devices. An one-dimensional constraint of the material gradation is imposed to provide more realistic designs.

A smart material is known to be able to generate large force in broad bandwidth in a compact size. However it needs relatively large voltage to drive it and this makes the system bulky. In this paper, first, we introduce an improved version of miniaturized piezo actuator driver and modeling of the dynamics of the piezo actuator, LIPCA. ARX model was used to model the dynamics of the LIPCA. We applied rectangular waves to the LIPCA and measured its responses with a strain gauge and a signal processing circuit. A 5th order model was obtained from the input/output data and applying identification algorithm. Secondly, we designed a simple PID controller based on the obtained model to improve the characteristics of the LIPCA actuator.

This paper is focused on developing a Squeeze Mode MR damper with large control capacity for effective vibration mitigation in infrastructures such as long span bridges and skyscrapers, etc. In order to maximize the magnetic field required for control of MR fluid, this device is designed by separating electromagnet system from the main cylinder for large capability of control force without changing its total length. This developed MR damper is tested to estimate its maximum control capacity and dynamic range(defined as the ratio of the maximum force to the minimum force that MR devices provide), inputting various strength magnet fields. These experimental results make it possible to estimate its maximum control force by drawing a curve showing the relationship between generated forces and applied magnetic fields. In order to verify its performance as a semi-active control device, its dynamic range is calculated. Through all tests, the developed MR is proved to be an effective device for the response control of infrastructures.

In this article, velocity and position controllers for magnetostrictive materials are designed and discussed. Magnetostrictive materials are a competitive choice for micro-positioning actuation tasks because of the large force and strain they provide. Unfortunately, they are highly nonlinear and hysteretic, which makes them difficult to control. In this article, the passivity approach is used to establish stability for velocity control. Using a physical argument, passivity of the system under discussion is proved. No model for magnetostrictive material is used in this proof and the result can be used in any hysteresis model for the material. This result is used to develop a stabilizing velocity controller. For position control, it is shown that a PI controller can provide stability and tracking if the hysteretic plant satisfies certain conditions. It is shown that these conditions are satisfied for the Preisach model under mild assumptions. Using this result, a class of stabilizing position controllers is identified. The velocity and position controllers are evaluated experimentally and their performances discussed.

This paper presents the results of modeling a shear-mode MR damper. The prototype damper consists of two steel parallel plates and in the middle, there is a paddle covered by foam saturated with MR fluid. The force is produced when the paddle is in motion and the magnetic field generated by a coil in one end of the device reaches the fluid. Several response forces were captured at different displacement excitations and magnetic field levels. The goal is to find a relationship between the velocity, the control voltage (inputs of the system) and the force generated by the device. The results of predicting the force using the Bingham, Bouc-Wen and Hyperbolic Tangent based models are compared and the suitability of these models is discussed.

This paper presents the development and application of an H∞ fault detection and isolation (FDI) filter and fault tolerant controller (FTC) for smart structures. A linear matrix inequality (LMI) formulation is obtained to design the full order robust H∞ filter to estimate the faulty input signals. A fault tolerant H∞ controller is designed for the combined system of plant and filter which minimizes the control objective selected in the presence of disturbances and faults. A cantilevered flexible beam bonded with piezoceramic smart materials, in particular the PZT (Lead Zirconate Titanate), in the form of a patch is used in the validation of the FDI filter and FTC controller design. These PZT patches are surface-bonded on the beam and perform as actuators and sensors. A real-time data acquisition and control system is used to record the experimental data and to implement the designed FDI filter and FTC. To assist the control system design, system identification is conducted for the first mode of the smart structural system. The state space model from system identification is used for the H∞ FDI filter design. The controller was designed based on minimization of the control effort and displacement of the beam. The residuals obtained from the filter through experiments clearly identify the fault signals. The experimental results of the proposed FTC controller show its e effectiveness for the vibration suppression of the beam for the faulty system when the piezoceramic actuator has a partial failure.

The current paper presents an explicit expression for an upper bound on the induced energy-to-peak norm for structural systems with collocated sensors and actuators. Using a linear matrix inequality (LMI)-based representation of the L₂ - L∞ norm of a collocated structural system, we determine an analytical upper bound on the L₂ - L∞ norm of such a system. The paper also addresses the problem of static output feedback controller design for such systems. By employing simple algebraic tools, we derive an explicit parametrization of feedback controller gains which guarantee a prescribed level of L₂ - L∞ performance for the closed-loop system. Finally, numerical examples are provided to validate the effciency and benefits of the proposed techniques. The effectiveness of the obtained bound and control design methodology is evident, in problems involving very large scale structural systems where solving Lyapunov equation or LMIs with large number of decision variables is time-consuming or intractable.

This paper presents an explicit expression for an upper bound on H₂ norm for structural systems with collocated sensors and actuators. Using a linear matrix inequality (LMI)-based representation of the H₂ norm of a collocated structural system, we determine an explicit upper bound on H₂ norm of such a system. The present paper also addresses the problem of output H₂ feedback controller design for collocated systems. Employing some simple algebraic tools, we derive an explicit parametrization of H₂ feedback controller gain which guarantees a prescribed level of H₂ performance for the closed-loop system. Numerical examples will be finally provided to validate the efficiency and benefits of the proposed method.

In this work, we revisit the problem of actuator placement within the context of spatial robustness. When one optimizes location-parameterized H² or H^∞ closed loop measures, arrives at actuator locations that provide performance optimality. However, these measures assume an a priori given distribution of disturbances. When the above measures include an additional optimization stage whereby one searches for the worst distribution of disturbances, then the resulting actuator location will result in both an improved performance and enhanced spatial robustness. Using an analytical bound approach that provides an explicit expression for an upper bound on the H^∞ norm of the system transfer function, the worst distribution of disturbances can be found that maximizes the open loop H bound. Subsequently, an optimal actuator location is found that minimizes the H∞ bound of the closed loop transfer function. This method minimizes the optimization complexity and provides great computational advantages in large scale flexible systems where the solution to H∞ optimization problems using standard tools becomes computationally prohibitive.

We consider a multilayer Rao-Nakra sandwich beam with shear damping included in alternate layers. In the case that the wave speeds of the layers are distinct, we show that by "tuning" the damping in each layer appropriately, it is possible to construct a scalar boundary control that exactly controls the entire layered system in a control time related to the sum of the control times of each separate layer. In the case where some waves speeds coincide, one can reduce the number of controls needed, but not to a single scalar control.

In this article, theoretical and the experimental studies are reported on the adaptive control of vibration transmission in a strut system subjected to a longitudinal pulse train excitation. In the control scheme, a magneto-strictive actuator is employed at the downstream transmission point in the secondary path. The actuator dynamics is taken into account. The system boundary parameters are first estimated off-line, and later employed to simulate the system dynamics. A Delayed-X Filtered-E spectral algorithm is proposed and implemented in real time. The underlying mechanics based filter construction allows for the time varying system dynamics to be taken into account. This work should be of interest for active control of vibration and noise transmission in helicopter gearbox support struts and other systems.

A fundamental step in the model construction for ferroelectric, ferromagnetic, and ferroelastic materials is the estimation or identification of material parameters given measurements of the material response. Moreover, actuator and/or material properties may be a function of operating conditions which can necessitate the re-estimation of parameters if conditions change significantly. In this paper, we focus on the development of highly robust and efficient identification algorithms for use in industrial, aeronautic and aerospace applications. Following a discussion of present and future applications, we summarize the homogenized energy model used to characterize hysteresis and constitutive nonlinearities in these compounds. We next discuss the parameter estimation problem and detail algorithms used to speed implementation. The validity of the framework is illustrated through comparison with experimental data.

The present paper is concerned with dynamic shape control of linear elastic plates under the action of transient forces, with prescribed time-dependent boundary conditions, and with given initial conditions. We consider anisotropic linear elastic plates. The following displacement tracking problem is treated: We ask for an additional distribution of actuation stresses such that the resulting displacements of the plates under consideration follow exactly some desired trajectories in every point and at every time instant. We present relations that must be satisfied for the actuation stresses in order that this goal of transient displacement tracking is reached. The actuation stresses we have in mind for enforcing tracking of transient displacements are induced by eigenstrains, such as thermal expansion strains or, more technologically important, piezoelectric parts of strain. Transient vibrations of circular plates in axi-symmetric bending are studied as an exemplary case. The vibrations are excited by support excitations. Actuation stresses are superimposed, which enforce the plate to track prescribed transient deflections. We present analytical solutions for the tracking of prescribed plate deflections with time-dependent support excitation. Coupling between electric and mechanical field is taken into account already at the level of plate theory. The analytical plate solutions are validated by Finite Element computations. Electromechanically coupled three-dimensional piezoelectric elements are used in these numerical calculations. Excellent coincidence between the analytical and the Finite Element computations is observed.

We propose two identification techniques for estimating the piezoelectric couplings and the piezoelectric capacitances of reduced order modal models of linear piezoelectric structures. The two methods are easily implementable and demand few input data, which can be obtained both with experimental testing and numerical models (e.g. finite elements). We apply these methods to a sample structure hosting multiple transducers. We discuss in details the proper definition and identification of the inherent piezoelectric capacitances, whose meaning is often misunderstood.

An inverse method for material parameter estimation of elastic, piezoelectric and viscoelastic laminated plate structures is presented. The method uses a gradient based optimization technique in order to solve the inverse problem, through minimisation of an error functional which expresses the difference between experimental free vibration data and corresponding numerical data produced by a finite element model. Applications are presented using a simulated test case for an adaptive plate.

The objective of this paper is to address one of the more difficult problems in astronomical Adaptive Optics (AO): on future Extremely Large Telescopes (ELT), the computing power required for the requisite number of actuators will exceed the computing power presently available. The PZT actuators for Deformable Mirrors (MD) have three axes: tilt, tip and piston. It is envisioned that these three axes can be controlled by adaptive wavelet filter banks. Adaptive echo cancellation will be applied to achieve wavefront correction in a manner analogous to that used to cancel telephone echoes. This approach will provide a viable alternative to those presently available and reduce the number of computations.

A two-span RC slab that measures 6400mm×800mm×100mm with 3000mm spans and 200mm overhang on each end was tested to failure in the laboratory. UB sections were used as supports. The slab was designed according to the moment redistribution method with 11 N6 bars at 75mm centres for both positive and negative reinforcement. The slab was incrementally loaded at the middle of each span to different load levels to create crack damage using four-point loading. Twelve loading stages were performed with increasing maximum load level. Two load cells are used to record the static loads on left and right spans. The crack locations and lengths were monitored in addition to the displacement measurements. Four displacement transducers are located at two sides of the middle of each span to measure the deflection under the static load. Three sets of accelerometers with nine of them in each set are evenly distributed along the slab to measure the dynamic responses. The measured responses from the RC slab in different cracked damage states are analyzed using the wavelet transform (WT). The damping ratios and instantaneous frequency are extracted. The results show that the damping ratio and instantaneous frequency changes could be two good indicators of damage in the reinforced concrete structure.

This paper applies wave propagation modelling for the analysis of sensor positions in Lamb wave based damage detection. The problem is investigated using the local interaction simulation approach for Lamb wave propagation modelling in an aluminum plate with a rectangular damage slot and a fatigue crack. The study demonstrates the great potential for optimal sensor location in damage detection techniques based on Lamb waves.

Various events in reciprocating machinery, such as connecting rod or piston movement, and diesel combustion produce a series of highly transient forces within the machine. These events generate force transients of short duration and broad frequency content. Even though these events may be part of a machine cycle and therefore periodic, it is often more appropriate to treat them on an individual basis because more diagnostics information is available from a single waveform during a cycle than from averages over several cycles. However, it is very rare for one to have direct access to source waveforms because of the expense and reliability problems associated with the required instrumentation, and non-invasive techniques will have to be used. This paper explores the use of cepstral smoothing and minimum phase extraction technique for non-invasive diagnostics of bearing impacts in reciprocating machinery. The methodology is based on extracting diagnostic signals from vibration measurements taken at a "convenient" location such as the crankshaft casing or bearing end-cap, and consists of source identification, diagnostic signature recovery, and diagnostic system decision-making. A dynamic simulation with lumped mass model is developed to analyze bearing impacts for the big end bearings, experimental measurements from accelerometers, transfer functions of vibration, and the structural response are presented.

The ability to detect and classify damages in complex materials and structures is an important problem from both safety and economical perspectives. This paper develops a novel approach based on Hidden Markov Models (HMMs) for the classification of structural damage. Our approach here is based on using HMMs for modeling the time-frequency features extracted from time-varying structural data. Unlike conventional deterministic methods, the HMM is a stochastic approach which better accounts for the uncertainties encountered in the structural problem and leads to a more robust health monitoring system. The utility of the proposed approach is demonstrated via example results for the classification of fastener damage in an aluminum plate.

The dynamic analysis using computational models is an important tool to simulate the dynamic of structures that have specific uncertain behavior like the cable stayed bridges which nowadays is an alternative to solve long span bridges with a slim structure. In this work we developed a 3D non linear model of a cable in order to evaluate the wind effect on the Papaloapan cable stayed bridge located on Veracruz Mexico, under different scenarios. The health of the structure is an important factor to analyze and there are many different fail causes, one of them is the fatigue fall that is relevant in the anchorage elements of the cable stayed bridges. It is possible to modify the behavior of the structure using dampers to minimize that effect. The geometry and all the forces and stress on the structures are a challenge also for the specialists of the structures, in this work the developed methodology resulted very successful to analyze the behavior of a cable on a cable stayed bridge using damping.

The transport of charge due to electric stimulus is the primary mechanism of actuation for a class of polymeric active materials known as ionomeric polymer transducers (IPT). At low frequency, strain response is strongly related to charge accumulation at the electrodes. Experimental results demonstrated using conducting powder, such as single-walled carbon nanotubes (SWNT), polyaniline (PANI) powders, high surface area RuO₂, carbon black electrodes etc. as an electrode increases the mechanical deformation of the IPT by increasing the capacitance of the material. In this paper, Monte Carlo simulation of a two-dimensional ion hopping model has been built to describe ion transport in the IPT. The shape of the conducting powder is assumed to be a sphere. A step voltage is applied between the electrodes of the IPT, causing the thermally-activated hopping between multiwell energy structures. Energy barrier height includes three parts: the energy height due to the external electric potential, intrinsic energy, and the energy height due to ion interactions. Finite element method software-ANSYS is employed to calculate the static electric potential distribution inside the material with the powder sphere in varied locations. The interaction between ions and the electrodes including powder electrodes is determined by using the method of images. At each simulation step, the energy of each cation is updated to compute ion hopping rate which directly relates to the probability of an ion moving to its neighboring site. Simulation ends when the current drops to constant zero. Periodic boundary conditions are applied when ions hop in the direction perpendicular to the external electric field. When an ion is moved out of the simulation region, its corresponding periodic replica enters from the opposite side. In the direction of the external electric field, parallel programming is achieved in C augmented with functions that perform message-passing between processors using Message Passing Interface (MPI) standard. The effects of conducting powder size, locations and amount are discussed by studying the stationary charge density plots and ion distribution plots.

Cellulose Electro-Active Paper (EAPap) has been reported as a new smart material that can be used as sensors and actuators. This material is attractive due to its advantages of biodegradable, lightweight, dryness, large displacement output, low actuation voltage and low power consumption. Its actuation principle has been known as a combination of ion migration and piezoelectric effects. Although extensive investigations have been made on mechanical properties, chemical and physical characteristics, the electrical properties have not been studied. This paper presents an investigation into the electrical breakdown strength of EAPap, which is important for determining the electric field limit for EAPap actuator. AC dielectric breakdown strength is measured with different humidity levels, according to ASTM standard. The measured data are statistically analyzed and it was found that failures associated with the formative stages of a breakdown mechanism might result in Weibull Statistics. As the humidity of the sample increases, the stress levels on cellulosic portions of the sample are enhanced, leading lower breakdown strength. This investigation will give an insight in understanding EAPap material.

A load-dependent hysteresis model for magnetostrictive materials is studied. Magnetostrictive materials are a class of smart materials which react with a magnetic field and are suitable for many micro-positioning actuation tasks. Unfortunately, these materials are difficult to use because of their highly nonlinear and hysteretic response. Unlike the hysteresis seen in magnetic materials, the shape of the hysteresis curve changes significantly if the load is changed. Because of this complex hysteresis, magnetostrictive actuators are difficult to control. To achieve sub-micron accuracy for micropositioning, an accurate hysteresis model is needed. The model studied in this paper is similar to the Preisach model. By modeling the Gibbs energy for each dipole and the equilibrium states, hysteresis in magnetostrictive materials is modeled. The model is implemented in a way that different hysteresis curves are generated if the load is changed. Using experimental data, optimum model parameters are obtained. The model results and experimental data were compared at different loads. A modification is proposed for more accuracy and the modified model is compared to the original model.