This PDF file contains the front matter associated with SPIE Proceedings Volume 6928, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Unmanned aerial vehicles typically have limited flight time due to their reconnaissance payload requirements and their restricted scale. A microwave/solar powered flight vehicle, on the other hand, can remain in-theater continuously by harvesting electromagnetic radiation using on-board antennas and solar panels. A rectifying antenna is used to harvest power and rectify it into a form usable by the on-board electric motors and other electronics, while photovoltaic cells harness incoming solar radiation. Discussed is the design of the fuel-less air vehicle and its sensitivity to several key performance metrics for this class of aircraft. New metrics are presented that are unique to microwave-powered aircraft and are useful in the design of its missions. Of critical importance is the strong coupling among the aircraft's flight performance, power harvesting abilities, and its mission capabilities. Traditional and non-traditional wing shapes are presented in order to motivate a discussion of some of the key parameters in the design of a fuel-less air vehicle.

This paper addresses a particular type of power harvesting in which energy in the periodic movement of structures is parasitically converted to stored electric charge. In such applications, tuning of the vibration power harvesters' resonance frequency is often required to match the host structures' forcing frequency. This paper presents a method of adjusting the boundary conditions of nonlinear stiffness elements as a means of tuning the resonance frequency of piezoelectric vibration power harvesters (altering the deformation mode from bending to in-plane stretching). Using this tuning method, the resonance frequency was experimentally varied between 56 and 62 Hz. For a vibration level of 2 mm/s, the harvester has a similar Q to a linear system but its Q is reduced by one third at a vibration level of 10 mm/s. This behavior is important for applications where high sensitivity is required for low vibration levels but mechanical robustness is required for high vibration levels.

The field of renewable energy has recently taken a surge with the advent of power harvesting systems. Much of the work previously done has focused primarily on dipole materials such as piezoelectric generators due to their high energy density. Exploring other vibration conversion techniques, electromagnetism has been theorized to be highly viable as well. In fact, in the presence of strong magnetic fields, its energy density can exceed that of piezoelectric systems. The key aspects to its usefulness lie in maximizing the rate of change of magnetic flux and thus maximizing the electric potential from the electromotive force. The specifics of this research include the descriptions of the electromagnetic theory, fabrication, and performance of a micro-electromagnetic power harvester with a vibration energy source. In addition, an empirical analysis of the influence of the micro-coil's geometry on the performance of the MEMS power harvester is given.

Vibration powered electrical generators typically feature a mass/spring resonant system to amplify small background vibrations. The compliance element in these resonant systems can become non-linear as a result of manufacturing limitations, physical operating constraints, or by deliberate design. The characteristics of mass/spring resonant systems with non-linear compliance elements are well known but they have not been widely applied within the field of energy harvesting. In this paper analysis of non-linear system behaviour using the harmonic balance method is presented, giving an insight into the potential benefits of non-linearities in energy harvesting applications. The design of a vibration powered energy harvester is reviewed and it is shown how the deliberate incorporation of non-linear behaviour within a design can be beneficial in improving magnetic loading and also in extending the range of frequencies over which the device can generate useful power.

Recent progresses in electronics allow powering complex systems using either batteries or environmental energy harvesting. However using batteries raises the problems of limited lifespan and recycling process, leading to the research of other energy sources for mobile electronics. Recent work on Synchronized Switch Harvesting (SSH) shows a significant improvement of energy harvesting from vibrations compared to standard techniques. Nevertheless, harvesting energy from vibrations necessitates that the electromechanical structure has to be driven by mechanical solicitations, which generally have a limited amount of energy. Therefore, for the design of efficient and truly applicable self-powered devices, combining several sources for energy harvesting would be greatly beneficial. Thermal energy is rarely considered due to the difficulty of getting efficient devices. However, the potential of such a source is one of the most important. This paper deals with energy harvesting using either piezoelectric or pyroelectric effect. Theoretical and experimental validations of thermal energy harvesting are presented and discussed. Standard thermodynamic cycles may be adapted in order to improve conversion effectiveness. Experimental converted energy as high as 160 mJ.cm^-3.cycle^-1 has been measured with a 35°C temperature variation, corresponding to 2.15% of Carnot efficiency.

Recent efforts in power harvesting systems have concentrated primarily on the optimization of isolated energy conversion techniques, such as piezoelectric, electromagnetic, solar, or thermal generators, but have focused less on combining different energy transducer types and have placed less emphasis on storing the converted energy for use by other devices. The purpose of this work is to analyze and present an integrated piezoelectric and electromagnetic power harvesting system utilizing existing technology for energy management and storage. Primary emphasis is on the analysis of the combination of existing, or readily obtainable, energy conversion techniques, operating as a single system, and the energy conversion efficiency of the alternating to direct current management, or storage, circuit.

Vibration powered electrical generators produce a raw AC electrical output that often needs to be converted into DC for use by the load systems. There are many possible ways to achieve this conversion (rectification) however the specific application of vibration energy harvesting requires a solution that is a delicate balance between efficiency, converter quiescent loss and impact upon the resonant generator operation. In this paper we investigate how vibration powered generators interact with typical rectification schemes and assess the overall system performance, comparing it to the theoretical maximum power that could be generated. Further to this we present practical circuits that address the inherent problems of passive rectification techniques including a unity power factor power converter, realised at ultra low powers, suitable for energy harvesting applications. Numerical models are validated with measured results.

The purpose of this effort is to investigate the effect of bias conditions on the power harvested using magnetostrictive materials. Towards that end, we first develop an analytical model to describe the dependence of the constitutive parameters on the bias conditions. We validate this model experimentally and define a range for its validity. We obtain a one-dimensional lumped-parameter model of the energy harvester and optimize it with respect to the load resistance and frequency ratio. The optimal expressions are then used to study the effect of bias conditions on the optimal values. We observe that the bias conditions significantly affect the antiresonance frequency allowing for possible real time control to maximize the energy flow from the environment to the load. Furthermore, it is observed that, in the range of bias conditions for which our model is valid, the harvested power increases with magnetic bias and decreases with the prestress.

This paper presents experimental results that demonstrate energy generating performance of circular piezoelectric diaphragm harvesters for use in implantable medical devices. The piezoelectric energy generators are designed to transfer internal biomechanical forces into electrical energy that can be stored and used to power other in vivo devices. Such energy harvesters can eliminate complicated procedures for replacement of batteries in active implants by possibly increasing the longevity or capacity of batteries. Experimental results indicated that the PZT circular diaphragm harvesters generated enough power to meet requirements for specific implantable medical devices. It is also found that edge condition, thickness of bonding layer, and a degree of symmetry in fabrication for the unimorph circular diaphragms affect the energy generating performance significantly.

The use of monolithic piezoceramic materials in sensing and actuation applications has become quite common over the past decade. However, these materials have several properties that limit their application in practical systems. These materials are very brittle due to the ceramic nature of the monolithic material, making them vulnerable to accidental breakage during handling and bonding procedures. In addition, they have very poor ability to conform to curved surfaces and result in large add-on mass associated with using a typically lead-based ceramic. These limitations have motivated the development of alternative methods of applying the piezoceramic material, including piezoceramic fiber composites (PFCs), and piezoelectric paints. Piezoelectric paint is desirable because it can be spayed or painted on and can be used with abnormal surfaces. The ease at which the active composite can be applied allows for far larger surfaces to be used for energy harvesting than can be achieved with typical materials. Developments in piezoelectric nanocomposites for energy harvesting will also allow for the development of compliant materials with electromechanical coupling greater than available through existing piezoelectric polymers such as polyvinylidene floride (PVDF). Furthermore, the application of PVDF is limited to thin films due to the straining process required to obtain piezoelectric phase of the material. However, active nanocomposites can be molded into geometries that could not be obtained using currently available materials. The present study will characterize a variety of piezoelectric nanocomposite materials to determine how the properties of the polymer matrix and the piezoelectric inclusion affect the energy harvesting performance. The resulting active nanocomposites will be compared to existing piezo-polymers for power harvesting.

Cantilevered piezoelectric harvesters have been extensively considered in the energy harvesting literature. Mostly, a traditional cantilevered beam with one or more piezoceramic layers is located on a vibrating host structure. Motion of the host structure results in vibrations of the harvester beam and that yields an alternating voltage output. As an alternative to classical cantilevered beams, this paper presents a novel harvesting device; a flexible L-shaped beam-mass structure that can be tuned to have a two-to-one internal resonance to a primary resonance ω₂ ≅ 2ω₁ which is not possible for classical cantilevers). The L-shaped structure has been well investigated in the literature of nonlinear dynamics since the two-to-one internal resonance, along with the consideration of quadratic nonlinearities, may yield modal energy exchange (for excitation frequency ω≅ ω₁or the so-called saturation phenomenon (for ω≅ω₂). As a part of our ongoing research on piezoelectric energy harvesting, we are investigating the possibility of improving the electrical outputs in energy harvesting by employing these features of the L-shaped structure. This paper aims to introduce the idea, describes the important features of the L-shaped harvester configuration and develops a linear distributed parameter model for predicting the electromechanically coupled response. In addition, this work proposes a direct application of the L-shaped piezoelectric energy harvester configuration for use as landing gears in unmanned air vehicle applications.

Novel tetrachiral honeycomb structures are evaluated for the first time from the vibroacoustic point of view. A numerical method based on Bloch wave approximations for Finite Element models of the unit cells is applied to simulate the pass-stop band characteristics of these cellular solids. Experimental modal analysis and modal densities are measured on honeycomb panels and sandwich plate, and the results evaluated with the experimental findings. The novel tetrachiral honeycombs show pass-stop band characteristics with isotropic acoustic signature, while sandwich structures made with the same honeycomb cores have the interesting feature of presenting a high-pass frequency behavior on the same pass-stop bands of the honeycomb.

Bimolecules have demonstrated the potential to function as active components in energy harvesting devices, biosensors and bioinspired actuators. The bilayer lipid membrane (BLM) formed from lipid molecules and supported in the pores of porous substrates is the standard platform for fabricating the biomolecule based devices. The techniques for forming BLM in an in-vitro environment like lipid painting, Lagmuir-Blodgett, Langmuir-Schaffer and lipid folding methods were developed by researchers in the biophysical community to investigate the properties of membrane bound proteins. While all of these methods can form a BLM and has been used in laboratory research for few decades, they are not equally well-suited for fabricating an engineering device. Of the different methods, the lipid deposition technique for BLM self-assembly and protein insertion is the closest in its qualities to an engineering prototyping method. This article presents a detailed electrical model of the substrates and the BLM formed in the pores from SOPC, POPS:POPE and DPhPC lipids using lipid deposition technique. The equivalent circuits of the substrates and the BLM are used to interrogate the quality of the BLM by impedance spectroscopy. The deviations of the prepared BLMs from desirable parameters are traced to the preparation procedure that could be used as a feedback information for fabricating a single BLM in the pores of the substrate. The impedance response is also used to understand the change in electrical properties of BLMs formed in an array of pores of a multi-porous substrate.

Presented in this paper is the development of a novel honeycomb sandwich panel with variable transverse stiffness. In this structure, the traditional sandwich face sheets are replaced by the fluidic flexible matrix composite (F²MC) tube layers developed in recent studies. The F²MC layers, combined with the anisotropic honeycomb core material properties, provide a new sandwich structure with variable stiffness properties for transverse loading. In this research, an analytical model is derived based on Lekhitskii's anisotropic pressurized tube solution and Timoshenko beam theory. Experimental investigations are also conducted to verify the analytical findings. A segmented multiple-F²MC-tube configuration is synthesized to increase the variable stiffness range. The analysis shows that the new honeycomb sandwich structure using F²MC tubes of 10 segments can provide a high/low transverse stiffness ratio of 60. Segmentation and stiffness control can be realized by an embedded valve network, granting a fast response time.

Helicopter aircrews are exposed to high levels of whole body vibration during flight. This paper presents the results of an investigation of adaptive seat mount approaches to reduce helicopter aircrew whole body vibration levels. A flight test was conducted on a four-blade helicopter and showed that the currently used passive seat systems were not able to provide satisfactory protection to the helicopter aircrew in both front-back and vertical directions. Long-term exposure to the measured whole body vibration environment may cause occupational health issues such as spine and neck strain injuries for aircrew. In order to address this issue, a novel adaptive seat mount concept was developed to mitigate the vibration levels transmitted to the aircrew body. For proof-of-concept demonstration, a miniature modal shaker was properly aligned between the cabin floor and the seat frame to provide adaptive actuation authority. Adaptive control laws were developed to reduce the vibration transmitted to the aircrew body, especially the helmet location in order to minimize neck and spine injuries. Closed-loop control test have been conducted on a full-scale helicopter seat with a mannequin configuration and a large mechanical shaker was used to provide representative helicopter vibration profiles to the seat frame. Significant vibration reductions to the vertical and front-back vibration modes have been achieved simultaneously, which verified the technical readiness of the adaptive mount approach for full-scale flight test on the vehicle.

Orthogonal eigenstructure control is used for designing a control law that decouples the dynamic modes of a flying vehicle. Orthogonal eigenstructure control is a feedback control method for linear time invariant multi-input multi-output systems. This method has been recently developed by authors. The advantage of this control method over eigenstructure assignment methods is that there is no need for defining the closed-loop poles or shaping the closed-loop eigenvectors. This method eliminates the error due to the difference between achievable and desirable eigenvectors, by finding vectors orthogonal to the open-loop eigenvectors within the achievable eigenvectors set and replacing the open-loop eigenvectors with them. This method is also applicable to the systems with non-collocated actuators and sensors. Application of this method for designing a flight control law for the lateral directional dynamics of an F-18 HARV is presented, and compared to the results of an eigenstructure assignment method. In this case study, the actuators and sensors are not collocated. It is shown that the application of the orthogonal eigenstructure control results in a more significant dynamic modes decoupling in comparison to the application of the eigenstructure assignment technique.

This paper presents optimal design of a controllable magnetorheological (MR) shock absorber for a passenger vehicle and shows several advantages of the optimized MR shock absorber on vibration control performance. In order to achieve this goal, a cylindrical MR shock absorber, which satisfies design specifications for a mid-sized commercial passenger vehicle, is designed using an optimization methodology. The optimization problem is to find optimal geometric dimensions of the magnetic circuit for the MR shock absorber in order to maximize damping force. The first order optimization method using commercial finite element method (FEM) software is adopted for the constrained optimization algorithm. After manufacturing the MR shock absorber with optimally obtained design parameters, its field-dependent characteristics are experimentally evaluated. The effect of the optimized MR shock absorber on suspension control is investigated using a quarter-vehicle system. Control performances such as vertical acceleration and power consumption are evaluated and compared between the initial and optimal shock absorbers.

One of the most limiting factors for distributed sensor networks used for railroad track health monitoring applications is the lack of a long-term, low-maintenance power supply. Most existing systems still require a change of battery, and remoteness of location and low frequency of maintenance can limit their practical deployment. In this paper we describe an investigation of two principal methods for harvesting mechanical power from passing railcars in order to supply electrical power to remote networks of sensors. We first considered an inductive voice coil device directly driven by vertical rail displacement. We then considered a piezoelectric device that is attached to the bottom of the rail and is driven by the longitudinal strain produced by rail bending due to passing railcars. Theoretical models of the behavior of these devices were integrated with an analytical model of rail track deflection to perform numerical simulations of both of these power scavenging techniques. Lab and field tests were also performed to validate the simulation results. Resulting values of average power production show promise for scavenging near the targeted level of 1 mW, and the field data matched well with the simulations.

This paper documents the development of a prototype smart aerosol drug inhaler system using shape memory alloy (SMA) actuators. Unlike conventional dispersed-release inhalers, the smart inhaler system releases the aerosol drug in a very small area within the mouth inlet. Kleinstreuer and Zhang [1] have found that controlled release in the mouth inlet increases drug efficiency and allows targeting of specific sites within the lung. The methodology has been validated numerically and experimentally using fixed-exit position inhalers. The design presented in this work, however, allows for variation of nozzle exit position using SMA wire actuators in a combined actuator/sensor role. In contrast to other possible mechanisms, SMA wires are lightweight, require low power, and are the least obstructive to the flow of air through the inhaler. The dual actuator/sensor nature of the SMA wires (via resistance measurement) further simplifies the design. Solutions and insights into several SMA actuator design challenges are presented. SMA wire actuator characteristics such as achievable stroke and their effect on the design are highlighted. Consideration of actuator force requirements and the capabilities of SMA wires and studied. The problems posed by the thermal characteristics of SMA wires and innovative solutions are reported.

An analysis and design study using Shape Memory Alloy (SMA) wire integrated beam and its buckling shape control are reported. The dynamical system performance is analyzed with a mathematical set-up involving nonlocal and rate sensitive kinetics of phase transformation in the SMA wire. A standard phenomenological constitutive model reported by Brinson (1993) is modified by considering certain consistency conditions in the material property tensors and by eliminating spurious singularity. Considering the inhomogeneity effects, a finite element model of the SMA wire is developed. Simulations are carried out to study the buckling shape control of a beam integrated with SMA wire.

Superelastic shape memory alloy (SMA) is a potential candidate for use in structural damping devices due to its unique mechanical properties. An innovative re-centering SMA damper is presented. Being configurated simply, the device comprises two functional groups of SMA strands, such as the un-pre-tensioned wires and the pre-tensioned wires, resulting in a perfect energy dissipation compatible with a negligible residual displacement. Based on the cyclic loading tests of the superelastic SMA wires, the Lagoudas simplified model is determined. Extensive experiments are carried out to investigate the influence of cycles, frequency and displacement amplitude on the mechanical behaviors of the damper, such as the secant stiffness, the dissipated energy per cycle and the equivalent viscous damping. By analyzing the working mechanism, a model is set up to simulate the hysteretic curve of the damper, its feasible predictions being validated by the experimental results. Furthermore, nonlinear time history analyses of a SDOF system are performed, and the results show that the re-centering damper not only can decrease the vibration of the system under excitations, but also can mitigate residual displacement after excitations.

Shape memory alloys (SMAs) have been used as actuators in many different industries since the discovery of the shape memory effect, but the use of SMAs as actuation devices in aeronautics has been limited due to the temperature constraints of commercially available materials. Consequently, work is being done at NASA's Glenn Research Center to develop new SMAs capable of being used in high temperature environments. One of the more promising high-temperature shape memory alloys (HTSMAs) is Ni_19.5Ti_50.5Pd₂₅Pt₅. Recent work has shown that this material is capable of being used in operating environments of up to 250°C. This material has been shown to have very useful actuation capabilities, demonstrating repeatable strain recoveries up to 2.5% in the presence of an externally applied load. Based on these findings, further work has been initiated to explore potential applications and alternative forms of this alloy, such as springs. Thus, characterization of Ni_19.5Ti_50.5Pd₂₅Pt₅ springs, including their mechanical response and how variations in this response correlate to changes in geometric parameters, are discussed. The effects of loading history, or training, on spring behavior were also investigated. A comparison of the springs with wire actuators is made and the benefits of using one actuator form as opposed to the other discussed. These findings are used to discuss design considerations for a surge-control mechanism that could be used in the centrifugal compressor of a T-700 helicopter engine.

Control of jet noise continues to be an important research topic. Exhaust-nozzle chevrons have been shown to reduce jet noise, but parametric effects are not well understood. Additionally, thrust loss due to chevrons at cruise suggests significant benefit from active chevrons. The focus of this study is development of an active chevron concept for the primary purpose of parametric studies for jet noise reduction in the laboratory and secondarily for technology development to leverage for full scale systems. The active chevron concept employed in this work consists of a laminated composite structure with embedded shape memory alloy (SMA) actuators, termed a SMA hybrid composite (SMAHC). SMA actuators are embedded on one side of the neutral axis of the structure such that thermal excitation, via joule heating, generates a moment and deflects the structure. The performance of two active chevron concepts is demonstrated in the presence of representative flow conditions. One of the concepts is shown to possess significant advantages for the proposed application and is selected for further development. Fabrication and design changes are described and shown to produce a chevron prototype that meets the performance objectives.

A new actuator system is being developed at the Cornell Laboratory of Intelligent Material Systems to address the problems of dynamic self-actuated shape change. This low profile actuator, known as the 'smart joint', is capable of maintaining rigidity in its nominal configuration, but can be actively strained to induce rotation at flexure joints. The joint is energetically efficient, only requiring power consumption during active morphing maneuvers used to move between shapes. The composite beam mechanism uses shape memory alloy (SMA) for strain actuation, with shape memory polymer (SMP) providing actively tailored rigidity due to its thermally varying properties. The first phase of the actuator development was modeling of the generic composite structure, proving analytically and computationally that the joint can produce useful work. The next phase focuses on optimization of this joint structure and usage, including ideal layering configurations and thicknesses in order to maximize various metrics specific to particular applications. Heuristic optimization using the simulated annealing algorithm is employed to best determine the structure of the joint at various scaling ratios, layering structures, and with varying external loading taken into account. The results are briefly compared to finite element models.

Optimization of the topology of a plate coupled with an acoustic cavity is presented in an attempt to minimize the fluid-structure interactions at different structural frequencies. A mathematical model is developed to simulate such fluid-structure interactions based on the theory of finite elements. The model is integrated with a topology optimization approach which utilizes the Moving Asymptotes Method. The obtained results demonstrate the effectiveness of the proposed approach in simultaneously attenuating the structural vibration and the sound pressure inside the acoustic domain at several structural frequencies by proper redistribution of the plate material. The presented topology optimization approach can be an invaluable tool in the design of a wide variety of critical structures which must operate quietly when subjected to fluid loading.

Dynamics of gas-turbine blades are particularly aero-elastic coupling sensitive. These aerodynamic limits can be pushed away by adding extra damping to the structure in order to reach even better compressor performance. However nowadays design and manufacturing techniques in aero-mechanics are achieving their maximum of state-of-the-art. As in many fields active control would solve easily this kind of instability. But the diffculty remains in the needed energy supply for actuators whereas these components are aimed to be bonded on rotating structures. The capacity of different auto-supplied devices using shunted piezoelectric circuits had been studied here to prevent turbomachine bladed from fluttering. Before realizing the study on complex turbomachine geometries, the presented technique uses a numerical development thanks to a 1D Euler-Bernoulli beam model combining both mechanical and electrical coupling parameters. A second development thanks to a 3D model had been made using a commercial tool, Comsol software. These approximate models are used to optimize electrically the shunted piezoelectric element and its localization. The results, verified experimentally, let suppose that vibrations can be reduced signiffcantly when shunted piezoelectric circuits are mounted on a real structure.

In this paper, a LQG controller based on the finite element model of SSI system is established to optimally control the responses of SSI system. Substructuring analysis is used to reduce the system into a smaller set of DOFs system to design the active controller, which includes the complete informations of SSI system. Furthermore, the influence of the boundary condition and the depth of soil layer on control effectiveness are investigated using the proposed method. The results show that different boundary conditions can get almost same control effectiveness, but depth of soil layer will influence the control effectiveness. Finally, the standard two-floor shear structure with SSI effects used as the model, and AMD controller strategy designed based on the proposed method is validated through a serial of shaking table tests, which further verify the proposed method, results show that the proposed method can more effectively control the responses of SSI system than that designed based on the lump-parameter model does.

The essence of AMD controller based on the fixed-base structure to control SSI system is interpreted, firstly. Then the applicability of AMD controller based on fixed-base structure to control SSI system is studied through simulation analysis using LQR algorithm. The results show that the AMD controller designed based on the fixed-base structure can control SSI system effectively when the ratio of the frequencies of the SSI system and the fixed-base structure ω_s / ω_r is larger than 0.9. However, when s ω_s / ω_r is smaller than 0.4 this kind controller is not suitable to control SSI system. Finally, the shaking table tests about AMD control SSI system built on three kinds of soil parameters are carried out using four kinds AMD controllers. Tests result that while the soil foundation is stiff enough the controllers work very effectively, while the soil foundation is soft the controllers can't control the response of SSI system even make larger deformation and acceleration of the structure. The test results further validate the conclusion of simulation analysis.

Numerical and technological tools have been developed for complete electromechanical integration of innovative shunting damping strategies for piezoelectric composite beam stabilization to realize a new type of hybrid piezo-composite smart structure. The approach enhances the performance of fully passive configurations to control mechanical power flow in a beam by using negative capacitance elements. In contrast to passive shunted components that target discrete modes, negative capacitance shunted piezoelectric transducers offer the potential for broadband control from the low Hertz into the kilohertz range. This paper presents an original approach to tune vibration power flow dispersion in a piezocomposite beam to obtain total wave absorption by only optimizing the electrical circuit configuration shunting a single piezopatch. The numerical study considers the power flow efficiency of the strategy and the stability and robustness difficulties observed when a single device is considered. The simplicity of the proposed electromechanical controlling device affords the possibility to define and realize distributed configurations and also lends itself to integrated distributed smart composite structures.

A fourth-order accurate method is presented for the computation of dynamic response in the field of structural vibration. Based on Benthien-Gurtin's principle of minimum transformed energy in linear elastodynamics in Laplace space, functional in the form of single convolution integral is obtained by restoring the functional in the Laplace space back into the original space. Based on the functional after spatial discretization, five-order Hermite interpolation functions are adopted to approximate the nodal displacement in local time domain. A unconditionally stable two-step recursive method is presented after the variational operation. The value of parameter θ is selected according to the unconditionally stable analysis. Accuracy analyses and examples show that the algorithm is a higher accurate method. The method provided an useful tool with simple code and easy implementation for the investigations of dynamic response computations in practical engineering.

Recently, a sensitivity enhancement technique for damage detection using eigenstructure assignment has been extended from linear to nonlinear systems. Nonlinearities have been accounted for by forming (higher dimensional) augmented systems, which are designed for each trajectory of the nonlinear system, and are characterized by a specific forcing that ensures that the augmented systems follow that trajectory (when projected onto the original, lower dimensional space). The use of system augmentation for damage detection has several benefits beyond its ability to handle nonlinearities. For example, sensitivity can be increased compared to existing linear techniques through nonlinear feedback auxiliary signals because the constraint that the system is stable during its interrogation has to be applied only to the linearized closed loop system, while the augmented linear system does not have that constraint. In this work, the various benefits of nonlinear feedback auxiliary signals are explored for damage detection in linear systems. System augmentation is used in a linear system because a nonlinear controller is employed to enhance sensitivity. In addition to the increased sensitivity, fewer controller actuator points and sensors are required compared to existing linear techniques due to the efficient use of added (augmented) equations. Numerical simulations for a linear mass-spring and a linear mass-spring-damper system are used to validate the approach and discuss the effects of noise.

The reliability assessment of complex active systems requires simulation methods, which reproduce complex system performance and also account for failure and fatigue scenarios. More and more, test methods traditionally carried out experimentally are replaced by computational or 'virtual' methods. Reliability of these complex adaptive systems is hard to estimate for several reasons. A priori undetermined interaction between various influencing parameters, unknown fatigue properties of the multifunctional materials employed in sensors and actuators and very complex system performance requirements make it difficult to predict under which circumstances the system may fail. Sensitivity Analysis (SA) of the comprehensive adaptive system model has proven to be a valuable tool for the identification and assessment of scenarios that are relevant for system reliability. For the example of an active oil pan, which is equipped with piezoelectric sensors and actuators to suppress structural vibrations, the method is outlined.

Smart fluid dampers can undergo large temperature changes due to the heating associated with energy dissipation. Such heating will alter the fluid's properties and could degrade control system performance. For example, previous work by the authors has shown that the stability of an MR damper under feedback control is dependent on the fluid's compressibility and viscosity. In the present study, a temperature dependent model of a magnetorheological damper is developed from experimental data, and it is shown that the fluid's yield stress, viscosity and compressibility parameters vary significantly. An experimental and numerical control study is then performed to investigate the resulting effects of temperature on the stability of two feedback controllers - a PID controller, and a proportional controller. Experimental results indicate that both controllers can exhibit a reduction in stability with increasing temperature, particularly if the controller gains are not suitably chosen. The temperature dependent MR damper model predicts this behaviour well, and it is shown that the change in viscosity has the most significant effect on stability. Future work could focus on the resulting effect on a complete vibration system, devices with different modes of operation, and alternative controllers.

Noise and vibration have always affected not only the operation of various devices but also people's comfort. These issues are highly present in currently emerging technologies like hydraulic launch assist vehicles. While the switching mechanisms in hydraulic hybrid vehicles enhance fuel efficiency, they cause complicated patterns of noise and vibration. This, combined with a wider range of frequencies excited by this mechanism requires advanced vibration isolators that can provide variable damping and stiffness. A solution to this problem can be provided by MR fluid based mounts. An MR fluid mount is capable of changing its stiffness and damping characteristics to accommodate various input excitation amplitudes and frequencies. This paper presents simulated results for a mixed mode magnetorheological (MR) fluid mount. If the MR mount is only working in one mode, either flow or squeeze mode, the range of isolation force provided by the damping and spring rate of the mount is constrained by the geometry of the respective mode. However, when the mount operates in both modes simultaneously, their effects are combined to accommodate a wider range of amplitudes and frequencies of excitation. The mathematical governing equations of the mount are derived to account for its operation with mixed flow modes. These equations implemented in MATLAB/Simulink^(c), with a specific set of parameters, predict the response of the mount for various excitations. The simulated results indicate that the combination of modes is beneficial for the mount performance in the low frequency range of operation.

In this work the performance of a new design concept utilizing a magnetorheological (MR) fluid-elastomer (MRF-E) is examined. A prototype MRF-E vibration isolator is built and its dynamic behavior is investigated under harmonic motions for a range of frequencies between 0.1Hz to 10.0Hz, under various applied magnetic fields. The experimental results exhibit the effects on the stiffness and the damping capability of the MRF-E vibration isolator is a function of the displacement and magnetic field strength; and weakly dependent on the frequency of motion. It is demonstrates that the new vibration isolator, whose mechanical properties can be controlled by an applied magnetic field, has potential in applications where tuning vibration characteristics are desired.

The mitigation of torsional responses in structures using semi-active devices is pursued in the current study. Multiple magnetorheological (MR) dampers are employed for real-time control of response of a benchmark structure to earthquake excitations. MR damper resistance levels are intelligently managed by a global fuzzy logic controller (FLC). The FLC is generated using a controlled-elitist genetic algorithm (GA). Development of an optimal FLC is expedited by a discretized search space of fuzzy logic membership functions. To enable robust control a training excitation is created using the RSPMatch2005 algorithm which modifies historic ground records in the time-domain by wavelet operations. Both numerical and large-scale experimental efforts are undertaken to validate the proposed control system. Results show the GA-optimized FLC performs superior to passive operation in 42% of considered cases.

This paper proposes an assistive knee brace that is aimed to provide assistance to old or disabled people. A magnetorheological (MR) actuator is developed to be used in assistive knee braces to provide controllable torque. The MR actuator consists of a DC motor and an MR brake/clutch. When active torque is needed, the DC motor works and the MR actuator functions as a clutch to transfer the torque generated by the motor to the leg; when passive torque is desired, the DC motor is turned off and the MR actuator functions as a brake to provide controllable passive torque. The prototype of this MR actuator is fabricated and experiments are carried out to investigate the characteristics of the MR actuator. The results show that the MR actuator is able to provide sufficient torque needed for normal human activities. Adaptive control is proposed for controlling the MR actuator. Experiments of the MR actuator under control are performed to study the torque tracking ability of the system.

The Macro Fiber Composite (MFC) is an actuator that offers high performance and flexibility. The application of MFC in the field of driving biomimetic tail is discussed in the paper. Making full use of the d33 effect, a piece of aluminum lamina with certain thickness is sticked in order to make the structures divided by the PZT fibers in MFC dissymmetrical. When applying voltage on the MFC, the structure will have a certain bending angle which is utilized to offer swinging power for the tail. In this paper, the ideal driving effect has been got with the limited driving force via the study of material property, material thickness, shape and size of the metal piece connected to the MFC, method of connection, the shape of the under water part of the fish. A reasonable shape and swinging strategy for biomimetic fish is designed according to the observation to the movement of alive fish and the study of bionics. The results of the experiment indicate that the largest extend of the tail's swinging angle in the air is 4 degree. The available frequency for the fastest speed is 2.5Hz. Comparing with the traditional biomimetic fish, it has the advances of small cubage, little noise, simple structure, and could be controlled in speed and extent because there is no motor inside. And the limit ability of driving, the uncontrollable feature of floating and sinking, and the existence of the power wires need to be solved in the coming research.

In this paper, we illustrate and study the opportunities of resonant ring type structures as wing actuation mechanisms for a flapping wing Micro Air Vehicle (MAV). Various design alternatives are presented and studied based on computational and physical models. Insects provide an excellent source of inspiration for the development of the wing actuation mechanisms for flapping wing MAVs. The insect thorax is a structure which in essence provides a mechanism to couple the wing muscles to the wings while offering weight reduction through application of resonance, using tailored elasticity. The resonant properties of the thorax are a very effective way to reducing the power expenditure of wing movement. The wing movement itself is fairly complex and is guided by a set of control muscles and thoracic structures which are present in proximity of the wing root. The development of flapping wing MAVs requires a move away from classical structures and actuators. The use of gears and rotational electric motors is hard to justify at the small scale. Resonant structures provide a large design freedom whilst also providing various options for actuation. The move away from deterministic mechanisms offers possibilities for mass reduction.

The goal of the research since the early 1990s has been to develop self-repairing and self sensing composites. Our revolutionary approach involves the autonomous release of repair chemicals from within the composite matrix itself and the active sensing to assess that action utilizing the same tube structure. The repair agents are contained in hollow, structural fibers that are embedded within the matrix. Under stress, the composite senses external environmental factors and reacts by releasing the repair agents from within the hollow vessels. This passive autonomous response occurs wherever and whenever cracking, debonding or other matrix damage transpires. Superior performance over the life of the composite is achieved through this self-repairing mechanism. The active sensing measures volume of voided repair chemical and location of voiding reveals the location and amount of damage to the laminate. This health monitoring of composites is important for their widespread use in life safety applications such as structures. The focus of the research being the implementation of active sensors and passive actuators which by using the same structure of glass tubes provide large area coverage without adding much parasitic weight. The development is a novel, voiding based sensor for damage detection with composite structures. This consists of a inspection guide produced from glass reinforcing fibers which release repair chemical when damaged.. The sensor was shown to be sensitive to very low impact energies, but also capable of revealing more extensive damage caused by high energy impacts. This unique combination of active sensing and passive repair serves as an example of combination for autonomous systems that can consist of various approaches in one integrated system.

This analytical work focuses on enhancing the ductility capacity and damage mitigation of reinforced concrete bridge columns during earthquakes by using innovative active confinement technique. The high recovery stress associated with the shape recovery of shape memory alloys (SMAs) is exploited to apply the confining pressure. A 2-D analytical model for a single column is developed and analyzed. The model is used to evaluate the seismic behavior of the column retrofitted with SMA rings and compare it with the behavior of the column retrofitted with the more conventional approach using carbon fiber reinforced polymer (CFRP) sheets. The stress-strain behavior of the concrete confined with internal ties only, internal ties and external SMA rings, and internal ties and external CFRP sheets is described based on two different constitutive models. The column model is subjected to cyclic loading with increasing amplitude and a ground motion excitation. The analysis shows that the SMA rings provide the column with more damage protection represented by a reduction in the maximum strain by up to 273% compared to CFRP sheets. In addition, the column retrofitted with SMA rings shows smaller lateral drifts compared to the column retrofitted with the CFRP sheets when subjected to the same ground motion excitation. The superior performance of the SMA rings is primarily attributed to the increase in the compressive strength at early stages of loading associated with applying the active confinement pressure.

This work presents the design and testing of a shape memory alloy and spring steel flexure actuator for use in a meso-scale, 18 degree of freedom hexapod. The paper discusses the general hexapod body design as well as a detailed design of the joints, actuators, and control methods of the individual hexapod legs. The performances of the control methods and of the hexapod legs are presented and discussed. Based on this measured performance, the expected rates of movement for different gaits are given. Other work on SMA actuated walking robots differs in scale or environment. In the field of walking robots the use of SMA as an actuator is mainly limited to micro-scale applications, in which we consider robots measuring less than 5 cm in any dimension micro-scale. This work seeks to demonstrate that actuation with SMA is also possible and worthwhile at the meso-scale of robotics, the proposed robot measuring roughly 45 centimeters. A notable meso-scale SMA actuated walking robot, the RoboLobster, differs from this work in intended environment. The RoboLobster, designed to operate in shallow ocean water, benefits from its environment through cooling for the SMA actuators which improves cycle time (Ayers [1]). This robot also differs in leg number, possessing eight legs over the six of a hexapod. A final group of meso-scale walking robots, hexapods and otherwise, are actuated by smart materials other than shape memory alloys, including piezoelectric actuators (Goldfarb [2], Yumayanto [3]).

We have analyzed and experimentally examined the flapping performances in terms of aerodynamic force generation, flapping frequency and flapping angle of the two flappers actuated by the original LIPCA and the compressed LIPCA, respectively. The flapping tests for two wing shapes were conducted at three different wing rotation angles and various flapping frequencies to search for the optimum flapping frequency, at which the maximum aerodynamic force was achieved, and investigate the effect of wing shape and wing rotation angle on the force generation of the flapper. The aerodynamic forces were calculated by subtracting the inertia forces measured in the vacuum from the total forces measured in the air. For the CFD simulation, we established the corresponding kinematical equations of the wing by examining the high-speed camera images taken from front and top at the same time. The experimental results showed we could improve the flapping angle 18.2 % and the average vertical aerodynamic force 24.5 % by using the compressed LIPCA.

The present study proposed a coupling method for the fluid-structural interaction analysis of a flexible flapping wing. An efficient numerical aerodynamic model was suggested, which was based on the modified strip theory and further improved to take into account a high relative angle of attack and dynamic stall effects induced by pitching and plunging motions. The aerodynamic model was verified with experimental data of rigid wings. A reduced structural model of a rectangular flapping wing was also established by using flexible multibody dynamics and a modal approach technique, so as to consider large flapping motions and local elastic deformations. Then, the aeroelastic analysis method was developed by coupling these aerodynamic and structural modules. To measure the aerodynamic forces of the rectangular flapping wing, static and dynamic tests were performed in a low speed wind-tunnel for various flapping pitch angles, flapping frequencies and the airspeeds. Finally, the aerodynamic forces predicted by the aeroelastic analysis method showed good agreement with the experimental data of the rectangular flapping wing.

This paper investigates the stabilization and control for flapping-wing flight of a simple flapping-wing vehicle. The aerodynamic forces and moments of flapping-wing flight are estimated by modified strip theory. From the resultant forces of the aerodynamics the flight dynamic analyses have been performed. For simulating cruising flight, one of the proper conditions has been chosen through parametric study and is assigned to the dynamics. As a result the trajectory and the body orientation of the vehicle are obtained which shows phugoid and short period motion in trim condition. With an adequate tail-wing pitch control, the vehicle simulated level-up movement from a trim condition to another.

The following is an investigation into the dynamic behavior of small deformable mirrors based on thin, metallized membranes. Focusing on providing a predetermined focus/defocus correction to a beam, as well as producing specified angular deflections of the beam in the vertical and horizontal planes. Directing the mirrored surface is accomplished using electrostatic actuation. Current designs are comprised of 3 actuator pads fabricated on a fiber reinforced plastic substrate that drive a metallized kapton membrane, which is separated from the substrate by spacers that provide a known air gap. A previous paper[3] consisted of a variable area actuation strategy that would only allow membrane deflection of 1/3 the total gap size before incurring instability due to "snap down". Addressed here is the proingblem of extend the control strategy into the deflection regime where the full nonlinear model must be used for the actuation force. A solution to this problem is an extended controller that can handle the full deflection range of the 40m air gap between the charged electrodes on the fixed substrate and the movable metallized reflective membrane. The observer for the control system operates in continuous time mode. Although the discrete area approximation is also shown alongside, only the continuous-area approximation is studied here. From the continuous-area approximation it is easily seen that the open loop system would be unstable, while the closed loop system closely follows the desired reference specification (maximum deflection approaching 40m, and bandwidth approaching 500 Hz).

The integration, analysis, control, and application of a linear actuator are investigated. The linear actuator has super-precision, large stroke, and simultaneous precision positioning and vibration suppression capabilities. It is an integration of advanced electro-mechanical technology, smart materials technology, sensing technology, and control technology. Based on the electromechanical technology, a DC-motor driven leading screw ensures the large stroke of motion and coarse positioning. The smart piezoelectric technology makes the fine positioning and vibration suppression over a wide frequency range possible. The advanced control strategy greatly compensates the hysteresis characteristics such as backlash and/or dead zone, and enables the excellent performance of the actuator. Several sensors such as load cells, displacement sensors, and encoders are also integrated for various applications. Controller design and testing of this linear actuator are also conducted. The applications of the linear actuator are also explored in precision positioning and vibration suppression of a flexible manipulator and smart composite platform for thrust vector control of satellites.

In this paper, a novel application of adaptive composite structures, a University of Hawaii at Manoa (UHM) smart composite platform, is developed for the Thrust Vector Control (TVC) of satellites. The device top plate of the UHM platform is an adaptive circular composite plate (ACCP) that utilizes integrated sensors/actuators and controllers to suppress low frequency vibrations during the thruster firing as well as to potentially isolate dynamic responses from the satellite structure bus. Since the disturbance due to the satellite thruster firing can be estimated, a combined strategy of an adaptive disturbance observer (DOB) and feed-forward control is proposed for vibration suppression of the ACCP with multi-sensors and multi-actuators. Meanwhile, the effects of the DOB cut-off frequency and the relative degree of the low-pass filter on the DOB performance are investigated. Simulations and experimental results show that higher relative degree of the low-pass filter with the required cut-off frequency will enhance the DOB performance for a high-order system control. Further, although the increase of the filter cut-off frequency can guarantee a sufficient stability margin, it may cause an undesirable increase of the control bandwidth. The effectiveness of the proposed adaptive DOB with feed-forward control strategy is verified through simulations and experiments using the ACCP system.

A novel thin film lead zirconate titanate Pb(Zr,Ti)O₃ (PZT) MEMS energy harvesting device is designed and developed for powering autonomous wireless sensors. It is designed to harvest energy from parasitic vibrational energy sources and convert it to electrical energy via the piezoelectric effect. The new pie-shaped design for the harvester is about a size of a nickel and has a radical departure from previous design concepts. This design always generates positive tension on the PZT layer and then positive charge output throughout vibration cycles. It produces mono-polarity output charge without using any additional bridge rectifier circuitry, which will be a huge cost saving for commercial production of scaled-up products. Contrary to the high Q cantilever designs, the new design has a low Q, doubly anchored beam design, which provides a wide bandwidth of operational frequency. This will enable more robust power generation even if the frequency spectrum of the source vibration varies unexpectedly. Furthermore, the beam shape is optimized to achieve uniform strain throughout the PZT layer. To authors' knowledge, this is the first self-rectifying piezoelectric power generator at the MEMS-scale

This paper presents a new type of jetting dispenser driven by a ring type piezoelectric actuator. By operating at very high frequencies, the dispenser is expected to provide very small dispensing dot size of low viscous adhesives (viscosity of 50cp to 500cp) at high dispensing flow rate in semiconductor packaging processes. After describing the mechanism and operational principle of the dispenser, a mathematical model of the system is derived by considering behaviors of the piezostack, the actuating spring, the dispensing needle and the adhesive fluid dynamics. In the modeling, a lumped parameter method is applied to model the adhesive whose rheological property is approximately expressed by Bingham model. The governing equation of the whole dispenser is then derived by integrating the structural model with the fluid model. Based on the proposed model, the dispenser is designed and manufactured. Subsequently, the dispensing performances such as dot size and dispensing flow rate are investigated using the proposed model and then validated by experiment.

Recently, power harvesting technologies for low-power electronic devices have attracted much interest. In this paper, the design and fabrication methods of a micro-electrostatic power generator is presented. This power generator comprises a stator developed using an electret film for charge storage and a rotor covered by an interdigital electrode for electric power generation. The newly developed electret material is made from mixing two solutions. The first solution was made by blending polystyrene (PS) and cycloolefin copolymer (COC). The second solution was obtained by an additive process as polar molecule was added into COC. This unique two solution electret method can easily be integrated and adopted to the micro fabrication process. The charge storage capability of this new electret material was investigated and results showed that low concentration of polystyrene in the blended material will not only have more stable but also higher electrostatic charge than that of pure COC. In addition, the polar molecular additives also improve the electret properties of COC due to micro-cavities formation and the interactions between molecules and polymer. Our newly developed blended electret material has excellent mechanical properties and is easy to use when compared to using Teflon Fluorinated Ethylene Propylene (FEP) and polypropylene (PP). A feasibility study of a micro electrostatic power generator based on our blended electret material was performed. Experimental results demonstrate the feasibility and effectiveness of this new type of micro electrostatic power generator.

With the objective of unraveling the issues involved in the piezo-electric control of the structures afflicted by nonlinearities, two examples are studied, viz. the problem of an axially compressed imperfect column resting on a softening elastic foundation and an imperfect stiffened plate with coincident local and overall critical loads. It is shown that the buckling capacity (the maximum static load, P_s) of these structures can be increased by piezo-electric patches actuated by feedback voltage proportional to the extreme fiber strains. In particular, in the case of stiffened plate piezo-electric patches conveniently located at the top and bottom tips of the stiffener can adequately perform this task. Next the control of these structures set into motion by a sudden application of a lateral load is investigated. The ensuing vibrations are controlled by voltages proportional to the strain rates sensed at the same locations. The control is feasible as long as the axial compression < P_d , the dynamic instability load. The optimality of the 'velocity control' is studied by appropriately varying the feedback gain. In the case of stiffened plate, stabilizing the stiffener has the effect of mitigating the local buckling displacements and amplitudes of the plate thus counteracting the adverse effects of interaction. However, it is shown that local buckling oscillations can be scotched by adding a thin longitudinal piezo-electric patch on the surfaces of the plate panel. While the control within the benchmark values of P_s and P_d in the static and dynamic cases is facile, any increase beyond these values are fraught with steeply increasing demand of electric field strength and consumption of energy.

Negative impedance shunts have been used with piezoelectric materials for the purposes of vibration suppression. Details of the shunt design may be determined using different performance objectives such as maximum dissipation or minimization of reactive input power. Experimentally optimized shunts are applied to a composite piezoelectric aluminum beam subjected to a broadband disturbance. Performance measures of interest include an overall power balance for the system, as well as tip vibration suppression and spatial average vibration suppression. The resulting measures are compared to the wave-tuning and reactive power input tuning suppression theories.

Using dirct and inverse piezoelectric effects of distributed piezoelectric films simultaneously, active flexible structures which posess vibration damping ability can be able to construct. However, conventional studies are limited to the control of relatively small (micron-order) displacements of thin flexible structures as well as numerical studies by handling controller design of software aspects. In this paper, several fundamental active vibration control principles, which will be valid in actual implementation, of smart flexible structures using piezoelectric films as distributed sensor/actuator have been developed. By applying each of these methods, it was verified that the enough vibration control effects were actually obtained and the theory agrees well with the experiment.

Some harsh environments contain high frequency, high amplitude mechanical vibrations. Unfortunately some very useful components, such as MEMS gyroscopes, can be very sensitive to these high frequency mechanical vibrations. Passive micromachined silicon lowpass filter structures (spring-mass-damper) have been demonstrated in recent years. However, the performance of these filter structures is typically limited by low damping. This is especially true if operated in low pressure environments, which is often the optimal operating environment for the attached device that requires vibration isolation. An active micromachined vibration isolation filter can be realized by combining a state sensor, and electrostatic actuator and feedback electronics with the passive filter structure. Using this approach, a prototype active micromachined vibration isolation filter is realized and used to decrease the filter Q from approximately 180 to approximately 50, when evaluated in a low pressure environment. The physical size of these active filters is suitable for use in or as packaging for sensitive electronic and MEMS devices, such as MEMS vibratory gyroscope chips.

This paper proposes a new method for the frequency response analysis of a vibration system with parametric excitation of damping coefficient. A base-excited single-degree-of-freedom model with a variable damper is considered. The variable damping coefficient can be changed to that in the case of a sine wave, i.e., a parametric excitation whose frequency can be arbitrarily selected. One of the external forces acting on the mass through the damper from the base is equivalent to the product of the damping coefficient and the input velocity. The product of the input sine wave and the frequency-controlled sine wave for variable damping, yields a new vibration that has a frequency different from the input frequency. Therefore, the oscillation of the damping coefficient at a suitable frequency can generate a new vibrational component that has the same frequency as that of the eigen-oscillation of the vibration system. As a result, the vibration amplitude increases because of resonance. In this study, first, we carry out theoretical analysis and obtain the frequency response of the proposed system. Subsequently, we confirm the effectiveness of the proposed analysis method by comparing the analysis result with previous simulation results.

Space structures would benefit greatly from an ability to tune the dissipation and stiffness of the structural element. This would provide a compromise between large passive systems, and complex, real-time, active control implementations. Different elements of a structure could be altered based on the loads that they experience. This study will focus on thin piezoelectric film strips connected in parallel with an electronic circuit which provides a "negative capacitance," and an electrical load consisting of a resistor and a capacitor. Due to the inverse piezoelectric effect, each film forms an electromechanical system in conjunction with the parallel circuit. The overall impedance of this system can be controlled by correctly varying gain parameters within the circuit. This work models the PVDF strips of non-vanishing thickness and stretched under a constant, boundary applied tension. Both flexural stiffness and in-plane tension are accounted for in setting up the partial differential equation of motion. Harmonic excitation was provided with an acoustic speaker driven by a wave form generator. Measurements of out-of-plane deflection at a chosen point were taken using an LED/photodiode pair, which was calibrated experimentally. The voltage developed between the electrodes was also measured. Theoretical and experimental results are analyzed and compared.

The addition of energy harvesting is investigated to determine the benefits of its integration into a small unmanned air vehicle (UAV). Specifically, solar and piezoelectric energy harvesting techniques were selected and their basic functions analyzed. The initial investigation involved using a fundamental law of thermodynamics, entropy generation, to analyze the small UAV with and without energy harvesting. A notional mission was developed for the comparison that involved the aircraft performing a reconnaissance mission. The analysis showed that the UAV with energy harvesting generated less entropy. However, the UAV without energy harvesting outperformed the other UAV in total flight time at the target. The analysis further looked at future energy harvesting technologies and their effect on the energy harvesting UAV to conduct the mission. The results of the mission using the advanced solar technology showed that the effectiveness of the energy harvesting vehicle would increase. Designs for integrating energy harvesting into the small UAV system were also developed and tests were conducted to show how the energy harvesting designs would perform. It was demonstrated that the addition of the solar and piezoelectric devices would supply usable power for charging batteries and sensors and that it would be advantageous to implement them into a small UAV.

Unmanned aerial vehicles (UAVs) are a critical component of many military operations. Over the last few decades, the evolution of UAVs has given rise to increasingly smaller aircraft. Along with the development of smaller UAVs, termed mini UAVs, has come issues involving the endurance of the aircraft. Endurance in mini UAVs is problematic because of the limited size of the fuel systems that can be incorporated into the aircraft. A large portion of the total mass of many electric powered mini UAVs, for example, is the rechargeable battery power source. Energy harvesting is an attractive technology for mini UAVs because it offers the potential to increase their endurance without adding significant mass or the need to increase the size of the fuel system. This paper investigates the possibility of harvesting vibration and solar energy in a mini UAV. Experimentation has been carried out on a remote controlled (RC) glider aircraft with a 1.8 m wing span. This aircraft was chosen to replicate the current electric mini UAVs used by the military today. The RC glider was modified to include two piezoelectric patches placed at the roots of the wings and a cantilevered piezoelectric beam installed in the fuselage to harvest energy from wing vibrations and rigid body motions of the aircraft, as well as two thin film photovoltaic panels attached to the top of the wings to harvest energy from sunlight. Flight testing has been performed and the power output of the piezoelectric and photovoltaic devices has been examined.

The morphing of wings from three different bat species is studied using an extension of the Weissinger method. To understand how camber affects performance factors such as lift and lift to drag ratio, XFOIL is used to study thin (3% thickness to chord ratio) airfoils at a low Reynolds number of 100,000. The maximum camber of 9% yielded the largest lift coefficient, and a mid-range camber of 7% yielded the largest lift to drag ratio. Correlations between bat wing morphology and flight characteristics are covered, and the three bat wing planforms chosen represent various combinations of morphological components and different flight modes. The wings are studied using the extended Weissinger method in an "unmorphed" configuration using a thin, symmetric airfoil across the span of the wing through angles of attack of 0°-15°. The wings are then run in the Weissinger method at angles of attack of -2° to 12° in a "morphed" configuration modeled after bat wings seen in flight, where the camber of the airfoils comprising the wings is varied along the span and a twist distribution along the span is introduced. The morphed wing configurations increase the lift coefficient over 1000% from the unmorphed configuration and increase the lift to drag ratio over 175%. The results of the three different species correlate well with their flight in nature.

In this study, we examine the propagation of mechanical waves on thin lightweight structures, with the aim of developing a method of crack detection in such structures. By comparing the response of healthy and cracked samples, we are sometimes able to differentiate between the two. Using a network of sensors it would be possible to determine the presence of a crack on a structure that is remote. Experimental work has been performed with single-crystal Silicon thin plates and a thin rectangular sheet of steel. The Silicon plates were tested healthy and cracked, and the steel was only tested when healthy. Piezo-ceramic stacks were used to provide actuation and sensing, and wave solutions to the equation of motion are obtained for the Silicon plate. Calculated and experimental results agree reasonably well.

Currently in optical machining systems, the voice coil actuator is implemented for servo control. The main obstacle that hinders the machining accuracy and efficiency is the limited bandwidth of voice coil. To fundamentally solve this issue, we develop a hybrid actuation system that consists of the voice coil that covers the coarse motion and a piezoelectric stack that induces the fine motion. The focus of this present research is the mechatronics synthesis of the actuation system through mechanism design. A series of numerical and experimental studies are carried out to optimally design the dual-stage actuation system that has adequate bandwidth at the system level while maintaining the stroke and alignment of the piezo stack. The performance of the new system is demonstrated via closed-loop system simulation.

In this paper we explore the use of bistable mechanisms for rotor morphing, specifically, blade tip twist. The optimal blade twist distributions for hover and high-speed forward flight are very different, and the ability of the rotor to change effective twist is expected to be advantageous. Bistable or "snap-through" mechanisms have multiple stable equilibrium states and are a novel way to achieve large actuation output stroke at relatively modest effort for gross rotor morphing applications. This is because in addition to the large actuation stroke associated with the snap-through (relative to conventional actuator/ amplification systems) coming at relatively low actuation effort, no locking is required in either equilibrium state (since they are both stable). In this work, the performance of a bistable twisting device is evaluated under an aerodynamic lift load. The device is analyzed using finite element analysis to predict the device's load carrying capability and bistable behavior.

Development and test results of a rotor blade twist control system that utilizes a thermo-mechanical shape memory alloy (SMA) are presented. The actuation system controls the blade shape during flight operations allowing the blade to be configured for greater lift during takeoff and landing. SMA actuators provided an excellent solution because of their very high torque output to weight ratio and suitability to the dynamic environment of a rotor blade. Several challenges related to the behavior of the SMA material are overcome by innovative control system design. Thermoelectric modules (TEM's) are used to actively transfer heat between SMA tubes and other heat conductor and radiator components. Modeling and system identification techniques and a non-trivial solution to nonlinear and coupled thermal response equations are used to insure effective use of the TEM's and to improve control during SMA phase transition.

This paper will present the effect of the vehicle dynamics of an aircraft with shape changing wings. The aerodynamic forces will be calculated using a 3D aerodynamic model developed that utilizes a modern adaptation of Prandtl's lifting-line method which can be used for wings of arbitrary camber, sweep and dihedral. The method will be applied to analyze the dynamics of different out-of-plane wing configuration of interest for morphing aircraft application. One particular wing configuration of interest is the wing configuration that has two sections, an out-of-plane dihedral section and a horizontal configuration, like a V shape wing configuration. An investigation as to how the partial dihedral will affect the dynamics of the vehicle, in turning is performed. A Comparison for symmetric and asymmetric wing configurations is performed.

Nowadays active vibration suppression of flexible manipulators is important in many engineering applications, such as robot manipulators and high-speed flexible mechanisms. The demand for short settling time and low energy consumption of the vibration suppression has necessitated the consideration to optimal control. For a wide range of operating conditions, the fixed optimal parameters determined for a control algorithm might not produce the highest performance. Hence, a self-tuning optimal control method for a flexible manipulator should be used to enhance the performance. This method can tune itself to the optimal parameters on the basis of the initial maximum responses of the controlled system. In this study, the multi-objective genetic algorithm is used to search for optimal parameters with regard to positive position feedback, thereby minimizing the settling time and energy consumption multi-objective functions. The experimental results reveal that the energy consumption can be reduced significantly while the settling time is still slightly increased.

Deformation of a cantilever beam having thin piezoelectric actuators partially debonded and buckling is analyzed by using a linear mathematical model based on the Timoshenko beam theory. Effects of location and size of the debonding are investigated for passive and active extension and bending. The buckling of the actuators is considered by applying a constant force equal to the buckling load at the boundary between the debonded and the bonded regions. When the actuators are debonded at their edges, only the bonded regions contribute to the deformation of the beam but the debonded regions do not contribute at all. When the actuators are debonded in the middle, both the ends of which are keeping bonded, their performances are almost the same as those for perfectly bonded actuators irrespective of the location and size of the debonded region before the debonded region buckles. However, after it buckles, the performance deteriorates depending on the distance from the clamp and the size of the debonded region.

The overall objective of the BATMAV project is the development of a biologically inspired bat-like Micro-Aerial Vehicle (MAV) with flexible and foldable wings, capable of flapping flight. This first phase of the project focuses particularly on the kinematical analysis of the wing motion in order to build an artificial-muscle-driven actuation system in the future. While flapping flight in MAV has been previously studied and a number of models were realized using light-weight nature-inspired rigid wings, this paper presents a first model for a platform that features bat-inspired wings with a number of flexible joints which allows mimicking the kinematics of the real flyer. The bat was chosen after an extensive analysis of the flight physics of small birds, bats and large insects characterized by superior gust rejection and obstacle avoidance. Typical engineering parameters such as wing loading, wing beat frequency etc. were studied and it was concluded that bats are a suitable platform that can be actuated efficiently using artificial muscles. Also, due to their wing camber variation, they can operate effectively at a large range of speeds and allow remarkably maneuverable flight. In order to understand how to implement the artificial muscles on a bat-like platform, the analysis was followed by a study of bat flight kinematics. Due to their obvious complexity, only a limited number of degrees of freedom (DOF) were selected to characterize the flexible wing's stroke pattern. An extended analysis of flight styles in bats based on the data collected by Norberg and the engineering theory of robotic manipulators resulted in a 2 and 4-DOF models which managed to mimic the wingbeat cycle of the natural flyer. The results of the kinematical model can be used to optimize the lengths and the attachment locations of the wires such that enough lift, thrust and wing stroke are obtained.

Construction of a novel vibratory tabular valve- and its design optimization is presented in the paper. The principle of the system operation is based on the effect of dynamic positioning of a steel ball in a vibrating tube. Theoretical analysis of the stability of this non-linear system is coupled together with the experimental study of an operating valve. Laser holographic interferometry is used for the identification and optimization of working regimes of the system.

Piezoelectric optical scanner is developed for multi-coordinate control of optical laser beam by excitation of microstructures. The manufactured microstructure is the grating which implemented in piezoelectric optical scanner. Such type of opto-micro-mechanical systems can be used for accurate angular or linear deflection of optical elements in various optomechanical and optoelectronic systems. The operating principle of these devices is based on piezoelectric effect and on conversion of high-frequency multi-dimensional mechanical oscillations of piezoelectric vibration transducers into directional multi-coordinate motion of the optical elements in the measurement chain. The main distinctive feature of such optical piezoelectric scanners is the combination of high micrometer range resolution with a wide range of angular deflections of the scanning elements. The manufacturing process and visualization of the microstructure were presented. The device consists of piezoelectric cylinder and a scanning element with three degrees of freedom. The control model of this device was derived using simulation of the working regimes of optical scanner by COMSOL Multiphysics software. Optical holography system was used to validate the result of simulation of piezoelectric optical scanner and to test the functionality of piezoelectric optical scanner with implemented microstructures.

This paper presents an approach to define an optimal piezoactuator length to actively control structural vibration. The optimal ratio of the piezoactuator length against beam length when a pair of piezoceramic actuator and accelerometer is used to suppress unwanted vibration with direct velocity feedback (DVFB) control strategy is not clearly defined so far. It is well known that direct velocity feedback (DVFB) control can be very useful when a pair of sensor and actuator is collocated on structures with a high gain and excellent stability. It is considered that three different collocated pairs of piezoelectric actuators (20, 50 and 100 mm) and accelerometers installed on three identical clamped-clamped beams (300 * 20 * 1 mm). The response of each sensor-actuator pair requires strictly positive real (SPR) property to apply a high feedback gain. However the length of the piezoactuator affects SPR property of the sensor-actuator response. Intensive simulation and experiment shows the effect of the actuator length variation is strongly related with the frequency range of SPR property. A shorter actuator gave a wider SPR frequency range as a longer one had a narrower range. The shorter actuator showed limited control performance in spite of a higher gain was applied because the actuation force was relatively small. Thus an optimal length ratio (actuator length/beam length) was suggested to obtain relevant performance with good stability with DVFB strategy. The result of this investigation could give important information in the design of active control system to suppress unwanted vibration of smart structures with piezoelectric actuators and accelerometers.

Two adjacent parallel building structures are connected by control devices including stiffness and damping components. These building structures are currently used in engineering since the control devices may reduce the dynamic responses in earthquake and wind excitation. But the connecting stiffness may chance dynamic characteristics of whole building and the coupling between two structures should be considered. In this paper, a new optimal design method for twostructure connection control system is proposed. The mathematical model of two-structure connection control system is established only including the damping components. The optimal parameters of dampers can be obtained by using the simplex optimal method with the performance index J in frequency domain. A new performance index ▵J of control devices is also proposed to obtain the optimal number and placement of control dampers. Numerical results illustrate that the proposed optimal design method is effective and flexible. It may properly utilize the interaction between two structures and the control devices to reduce the response of buildings.

The paper highlights the design and some results concerning a novel sensor for robotic applications. The need of reliable, redundant multisensor devices has brought us to investigate a way of realizing a prototype with discrete components, freely available on the market or just developed. The product allows measurement of pressures, temperatures and vibrations over a surface similar to a Letter-size sheet.

In the preliminary design phase of the bio-inspired flapping-wing MAV (micro air vehicle), it is necessary to predict the aerodynamic forces around the flapping-wing under flapping-wing motion at cruising flight. In this study, the efficient quasi-steady flapping-wing aerodynamic model for MAV application is explained and it is experimentally verified. The flapping-wing motion is decoupled to the plunging and pitching motion, and the plunging-pitching motion generator with load cell assembly is developed. The compensation of inertial forces from the measured lift and thrust is studied to measure the pure aerodynamic loads on the flapping-wing. Advanced ratio is introduced to evaluate the unsteadiness of the flow and to make an application range of flapping-wing aerodynamic model.

Energy dissipation technique, relying on the absorption and dissipation of big amount of energy by devices, provides a very effective passive method of protecting structures from the hazard of earthquakes. An innovative hybrid damper combining friction device with superelastic shape memory alloy (SMA) wires was proposed. The most important property of the damper is the integration with stable energy dissipation capacity mostly provided by the friction device and re-centring feature profited from the superelastic pre-tensioned SMA wires. To investigate the mechanical behaviors of the damper as a function of pre-displacement, displacement amplitude and loading frequency, cyclic tensile tests on a scale model under various loading conditions were conducted. The effectiveness of the damper to reduce the seismic vulnerability of structures is assessed through nonlinear time history analysis on a steel frame with the innovative dampers subjected to representative earthquake ground motions. The experimental and analytical results show that the hybrid SMA damper has both the stable energy dissipating and recentring features with the hysteretic loop under cyclic loading-unloading, and it is effective in reducing the seismic response of structures.

Traditional solutions to vibration problems often employ viscoelastic materials which can be heavy, temperature-sensitive and bulky. Active solutions can provide useful damping but are often complex and expensive. This paper outlines a passive piezoelectric damping system with an adaptive controller capable of not only providing useful damping levels, but of modifying the components so as to change the circuit resonant frequency and thereby the damping effort. Experiments on simple beams and more realistic structures are described and the potential benefits and power requirements of such a system discussed. Increases in loss factor up to a factor of 10 and a high level of tuning repeatability were seen.

Micro-fabricated diaphragms can be used to provide pumping action in microvalve and microfluidic applications. In this paper, a design for a micro-diaphragm that features low power and small area is presented. The diaphragm is actuated using a Surface Acoustic Wave (SAW) device that is interrogated from an RF signal to provide secure actuation operation. The micropump is targeted for in vivo nano-scale drug delivery and similar applications. For low power micropump operation, it is important to design the diaphragm with a higher flexibility while maintaining the stability. Analysis is carried out using ANSYS simulation tools with different design methods and materials. Results achieved from analytical and Finite Element Modeling (FEM) methods are compared and discussed to decide on optimal dimensions for the diaphragm.

Novel methods for remote coupling of light into optical fibers embedded in composite structures has been explored. A passive technique in which light is coupled via a 45° angled mirror manufactured at the end of a plastic optical fiber (POF) was explored as well as an active technique in which a dye-impregnated POF was used to couple light to immersed fibers without physical connectorization. The fibers were immersed in fluids with different refractive indices to determine the effect of index on the coupling efficiency and simulate optical fibers embedded in a polymer composite. The passive technique proved much more efficient with a maximum efficiency of 91.4% achieved in an index of 1.33. The dye-impregnated POF was much less efficient with typical values ranging from 1%-2% for various indexes.