This PDF file contains the front matter associated with SPIE Proceedings volume 7643, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

A patch of piezoelectric material driving a negative impedance shunt circuit can be attached to a flexible structure for vibration damping as well as altering the effective stiffness of the overall structure and shift its resonant frequency. This work uses a truly coupled mechanical/electrical analysis where the negative impedance converter (NIC) circuit is modeled using fundamental operational analysis modeling technique, enabling a straightforward analysis of circuit stability, while clarifying the effect of each parameter in the NIC circuit on the overall circuit impedance, and ultimately, the mechanical response of the structure. Two types of piezoelectric materials are considered, a piezoelectric polymer and a macrofiber composite. Also examined in this work is an alternative approach to load impedance tuning which seeks circuit parameter settings that equate the load impedance to the complex conjugate of the mechanical impedance of the piezoelectric for a particular out-of-plane vibration mode. Additionally, the effects of circuit stability and variations of the reference capacitor are investigated. Both theoretical simulations and experimental results are presented.

Shunted piezoceramics can be used to dissipate vibration energy of a host structure and therefore reduce vibration amplitudes. The piezoceramic converts a portion of the mechanical energy into electric energy which is then dissipated in an electric network. One semi-active control technique is the synchronized switch damping on inductance (SSDI), which has a good damping performance and can adapt to a wide range of excitation frequencies. In the standard SSDI a switch is closed during maximum deformation for one half of the electrical period time. This results in an inversion of the electrical charge. For the rest of the half-period the switch is opened and the charge remains constant. This results in a nearly rectangular voltage signal, which is in antiphase with the deformation velocity. In case of multimodal excitation, more sophisticated switching laws are developed with the aim to extract vibration energy from higher modes (i.e. Richard). This paper describes a novel multimodal switching law for vibration damping. An observer is designed to obtain an estimation of the first two vibration modes, which are used to determine the switching times. In simulations the increase in energy dissipation is evaluated and compared to the standard SSDI technique. With the new switching algorithm an improvement in energy dissipation is observed. The theoretical results are validated by measurements carried out on a clamped-free beam. The location of the piezoceramics is chosen to optimize the electro-mechanical coupling with the first vibration mode of the beam. The modal observer is realized in a realtime environment. Measurements show a good agreement with the theoretical results.

Remarkable vertical seismic motion is one of the prominent characteristics of the near-fault earthquake motions, but the traditional and widely used base isolation system only can effectively mitigate horizontal seismic responses and structural damage. A promising three-dimensional (3D) seismic isolation bearing, consisting of laminated rubber bearing with lead core (LRB) and combined coned disc spring with vertical energy dissipation device (e.g., inner fluid viscous cylindric damper or steel damper), was proposed to mitigate horizontal and vertical structural seismic responses simultaneously and separately. Three-group seismic ground motion records were selected to validate the effectiveness of the proposed 3D seismic isolation bearing on a continuous slab bridge. The appropriate damping of the vertical damping device was presented by parametric study. The analyses results showed that the proposed 3D isolation bearing is essentially effective to mitigate vertical and horizontal structural seismic response simultaneously. Near-fault pulse-type seismic motions should be considered in seismic isolation design and evaluation. The proper damping ratio of the vertical damping device should be 20%-30% for favorable vertical isolation effectiveness. The proposed 3D seismic isolation bearing is promising to be applied to the mediate-to-short span bridge and even some building structures.

Active twist control of airfoils by means of embedded actuators has been widely studied during the last decade (N.A.S.A., University of Maryland, D.L.R., O.N.E.R.A., . . . ) Here, we propose a method which is to our knowledge new and which makes it possible to control the twist by modifications of the internal structure of the profile inducing displacement of the shear center and, therefore, modifications of the torsional moment and angle. This method is only operating if the profile is submitted to an external force. This is why this method is called "reactive" by opposition to the method mentionned above. Experiment has been done to verify the efficiency of the method proposed.

The seismic response of a multi-span continuous bridge isolated with novel superelastic-friction base isolator (S-FBI) is investigated under near-field earthquakes. The isolation system consists of a flat steel-Teflon sliding bearing and a superelastic NiTi shape memory alloy (SMA) device. Sliding bearings limit the maximum seismic forces transmitted to the superstructure to a certain value that is a function of friction coefficient of sliding interface. Superelastic SMA device provides restoring capability to the isolation system together with additional damping characteristics. The key design parameters of an S-FBI system are the natural period of the isolated, yielding displacement of SMA device, and the friction coefficient of the sliding bearings. The goal of this study is to obtain optimal values for each design parameter by performing sensitivity analyses of the isolated bridge. First, a three-span continuous bridge is modeled as a two-degrees-of-freedom with S-FBI system. A neuro-fuzzy model is used to capture rate-dependent nonlinear behavior of SMA device. A time-dependent method which employs wavelets to adjust accelerograms to match a target response spectrum with minimum changes on the other characteristics of ground motions is used to generate ground motions used in the simulations. Then, a set of nonlinear time history analyses of the isolated bridge is performed. The variation of the peak response quantities of the isolated bridge is shown as a function of design parameters. Also, the influence of temperature variations on the effectiveness of S-FBI system is evaluated. The results show that the optimum design of the isolated bridge with S-FBI system can be achieved by a judicious specification of design parameters.

Shape Memory Alloy are considered as one of the best active materials for actuation due to their remarkable properties, mainly their large strain and their power to weight ratio. On the other hand, they also have undesirable features that limit applications. One reason is their large thermal time constant. Antagonistic actuators are generally presented as a possible solution to this problem. Another reason is the non-linear behavior inherent to the hysteresis of the phase transition used for the actuation. This paper addresses this problem in the case of antagonistic actuator using an adaptive control scheme where the identification is performed using Laguerre filters. Results obtained on experimental setup prove that this control scheme is able to handle the complex non-linearities of hysteretic antagonistic actuator.

This paper discusses the modeling, design and performance of SMA actuated Post-Buckled Precompressed (PBP) plates. The paper begins with an outline of past approaches to PBP actuation and control which have mostly been centered on piezoelectric actuators. To skirt problems associated with tensile failure on convex faces of PBP actuators, SMA filaments are used. Because SMA's are far less sensitive to tensile failure, far greater deflections and work outputs are both predicted and experimentally measured. Unlike conventional SMA actuated plates, the total moment generation capability and deflections can be simultaneously amplified, indicating a substantial increase in total work output. Experiments showed that the SMA actuators are capable of tip deflection of up to 45° and that the Post-Buckled Precompressed Mechanism improves tip rotation up to 40% compared to conventional antagonistically actuated SMA plates.

Superelasticity (SE), shape memory effect (SM), high damping capacity, corrosion resistance, and biocompatibility are the properties of NiTi that makes the alloy ideal for biomedical devices. In this work, the 1D model developed by Brinson was modified to capture the shape memory effect, superelasticity and hysteresis behavior, as well as partial transformation in both positive and negative directions. This model was combined with the Euler beam equation which, by approximation, considers 1D compression and tension stress-strain relationships in different layers of a 3D beam assembly cross-section. A shape memory-superelastic NiTi antagonistic beam assembly was simulated with this model. This wire-tube assembly is designed to enhance the performance of the pedicle screws in osteoporotic bones. For the purpose of this study, an objective design is pursued aiming at optimizing the dimensions and initial configurations of the SMA wire-tube assembly.

Personal electronic devices such as cell phones, GPS and MP3 players have traditionally depended on battery energy storage technologies for operation. By harvesting energy from a person's motion, these devices may achieve greater run times without increasing the mass or volume of the electronic device. Through the use of a flexible piezoelectric transducer such as poly-vinylidene fluoride (PVDF), and integrating it into a person's clothing, it becomes a 'wearable transducer'. As the PVDF transducer is strained during the person's routine activities, it produces an electrical charge which can then be harvested to power personal electronic devices. Existing wearable transducers have shown great promise for personal motion energy harvesting applications. However, they are presently physically bulky and not ergonomic for the wearer. In addition, there is limited information on the energy harvesting performance for wearable transducers, especially under realistic conditions and for extended cyclic force operations - as would be experienced when worn. In this paper, we present experimental results for a wearable PVDF transducer using a person's measured walking force profile, which is then cycled for a prolonged period of time using an experimental apparatus. Experimental results indicate that after an initial drop in performance, the transducer energy harvesting performance does not substantially deteriorate over time, as less than 10% degradation was observed. Longevity testing is still continuing at CSIRO.

A novel class of two-stage piezoelectric-based electrical energy generators is presented for rotary machinery in which the input speed is low and varies significantly, even reversing. Applications include wind mills, turbo-machinery for harvesting tidal flows, etc. Current technology using magnet-and-coil rotary generators require gearing or similar mechanisms to increase the input speed and make the generation cycle efficient. Variable speed-control mechanisms are also usually needed to achieve high mechanical to electrical energy conversion efficiency. Presented here are generators that do not require gearing or speed control mechanisms, significantly reducing complexity and cost, especially pertaining to maintenance and service. Additionally, these new generators can expand the application of energy harvesting to much slower input speeds than current technology allows. The primary novelty of this technology is the two-stage harvesting system. The harvesting environment (e.g. wind) provides input to the primary system, which is then used to successively excite a secondary system of vibratory elements into resonance - like strumming a guitar. The key advantage is that by having two decoupled systems, the low-andvarying- speed input can be converted into constant and much higher frequency vibrations. Energy is then harvested from the secondary system's vibrating elements with high efficiency using piezoelectric elements or magnet-and-coil generators. These new generators are uncomplicated, and can efficiently operate at widely varying and even reversing input speeds. Conceptual designs are presented for a number of generators and subsystems (e.g. for passing mechanical energy from the primary to the secondary system). Additionally, analysis of a complete two-stage energy harvesting system is discussed with predictions of performance and efficiency.

Several novel classes of piezoelectric-based energy-harvesting power sources are presented for very high-G gun-fired munitions (40,000 - 240,000 Gs). The power sources are designed to harvest energy from the firing acceleration and in certain applications also from in-flight vibrations. The harvested energy is converted to electrical energy for powering onboard electronics, and can provide enough energy to eliminate the need for batteries in applications such as fuzing. During the munitions firing, a spring-mass system undergoes deformation, thereby storing mechanical potential energy in the elastic element. After release, the spring-mass system is free to vibrate and energy is harvested using piezoelectric materials. Two distinct classes of systems are presented: First are systems where the spring-mass elements are loaded and released directly by the firing acceleration. Second are those which use intermediate mechanisms reacting to the firing acceleration to load and release the spring-mass system. Description and evaluation of various methods for loading and releasing the spring-mass system in the high-impact environment, as well as packaging for very-high-G survivability are discussed at length. Also included are methods for using the devices as hybrid generator-sensors, how the devices intrinsically provide augmented safety, and methods to increase the efficiency of such power sources for very high-G applications. Examples of a number of prototypes for complete high-G energy harvesting systems are presented. These power sources have been designed using extensive modeling, finite element analysis, and model validation testing. The results of laboratory, air-gun and firing tests are also presented.

Vibration energy harvesting has received considerable attention in the research community over the past decade. Typical vibration harvesting systems are designed to be added on to existing host structures and capture ambient vibration energy. An interesting application of vibration energy harvesting exists in unmanned aerial vehicles (UAVs), where a multifunctional approach, as opposed to the traditional method, is needed due to weight and aerodynamic considerations. The authors propose a multifunctional design for energy harvesting in UAVs where the piezoelectric harvesting device is integrated into the wing of a UAV and provides energy harvesting, energy storage, and load bearing capability. The brittle piezoceramic layer of the harvester is a critical member in load bearing applications; therefore, it is the goal of this research to investigate the bending strength of various common piezoceramic materials. Three-point bend tests are carried out on several piezoelectric ceramics including monolithic piezoceramics PZT-5A and PZT-5H, single crystal piezoelectric PMN-PZT, and commercially packaged QuickPack devices. Bending strength results are reported and can be used as a design tool in the development of piezoelectric vibration energy harvesting systems in which the active device is subjected to bending loads.

Shape memory alloys (SMAs) are a relatively new class of functional materials, exhibiting unique thermo-mechanical behaviors, such as shape memory effect and superelasticity, which enable their great potentials in seismic engineering as energy dissipation devices. This paper presents a study of the mechanical behaviors of superelastic SMAs, specially emphasizing on the influence of strain rate under various strain amplitudes. Cyclic tensile tests on superelastic NiTi SMA wires with different diameters under quasi-static and dynamic loadings were carried out to assess their dynamic behaviors. An internal temperature variable which indicates the influence of loading frequency under various strain amplitudes and different temperatures was introduced to the Liang's constitutive equation of SMA. Numerical simulation results based on the proposed constitutive equations and experimental results are in good agreement. The findings in this paper will assist the future design of superelatic SMA-based energy dissipation devices for seismic protection of structures.

By adding randomly distributed short fiber into a shape memory polymer (SMP) matrix, both the mechanical properties and the shape memory behavior are improved significantly, overcoming some traditional defects of SMP composite reinforced by long fiber and particles. In this paper, the short fiber reinforced SMP composite are developed for the improvement of the mechanical and thermal properties of styrene-based SMP bulk. The specimens with different chopped fiber weight fractions are prepared, and then their mechanical behavior and electrical properties are investigated. As a result, the resistance against mechanical and thermal mechanical loads in the developed materials increases due to the role of reinforcement fiber. For the conducting composite filled with short carbon fiber, not only the actuation of SMP composite can be driven by low voltage, but also its tensile, bending strength, glass transition temperature, storage modulus and thermal conductivity increase by a factor of filler content of carbon fiber increasing. The results show meaningful guidance for further design and the performance evaluation of such composite materials.

Actively manipulating flow characteristics around the wing can enhance the high-lift capability and reduce drag; thereby, increasing fuel economy, improving maneuverability and operation over diverse flight conditions which enables longer, more varied missions. Active knits, a novel class of cellular structural smart material actuator architectures created by continuous, interlocked loops of stranded active material, produce distributed actuation that can actively manipulate the local surface of the aircraft wing to improve flow characteristics. Rib stitch active knits actuate normal to the surface, producing span-wise discrete periodic arrays that can withstand aerodynamic forces while supplying the necessary displacement for flow control. This paper presents a preliminary experimental investigation of the pressuredisplacement actuation performance capabilities of a rib stitch active knit based upon shape memory alloy (SMA) wire. SMA rib stitch prototypes in both individual form and in stacked and nestled architectures were experimentally tested for their quasi-static load-displacement characteristics, verifying the parallel and series relationships of the architectural configurations. The various configurations tested demonstrated the potential of active knits to generate the required level of distributed surface displacements while under aerodynamic level loads for various forms of flow control.

The Smart Inhaler design concept recently developed at NC State University has the potential to target the delivery of inhaled aerosol medication to specified locations within the lung system. This targeted delivery could help patients with pulmonary ailments by reducing the exposure of healthy lung tissue to potentially harmful medications. However, controlled delivery can only be accomplished if medication is injected at a precise location in an inhaled stream of properly conditioned laminar flow. In particular, the medication must be injected into the inhaled flow using a small nozzle that can be positioned without disturbing the flow. This paper outlines the procedure used to assemble and control a key component of the smart inhaler: a shape memory alloy (SMA) based dual-joint flexible nozzle that exploits the sensing and actuating capabilities of thermally activated SMA wires. A novel 6-channel power-supply is used to control input power and measure the resistance across the SMA. Since a practical fabrication process may result in SMA wires with different contact resistances, the power supply employs an initialization procedure to self-calibrate and provide normalized power distribution 6 SMA wires simultaneously. Furthermore, a robust control scheme is used to ensure that a constant current is provided to the wires. In validation tests, a LabVIEW-based video positioning system was used to measure the deflection of the nozzle tip and joint rotation. Results show that the carefully controlled assembly of a stream-lined nozzle can produce a practical smart structure, and joint rotation is predictable and repeatable when power input is also controlled. Future work will assess the use of the SMA-resistance measurement as position feedback and PID position control power as a measurement of the convective cooling that results from the moving airflow.

In a piezoelectric energy harvesting (PEH) system, the dynamics of the device as well as the energy flow within the system vary with different harvesting interface circuits connected. Meanwhile, the impedance matching theory is regarded as theoretical base for harvesting power enhancement, and hopefully could provide guidance for harvesting interface optimization. Most previous literatures on impedance matching for PEH started their analyses by assuming that the harvesting interface, which is nonlinear in nature, can be equalized to resistive load, or linear load whose impedance value can be arbitrarily set, so that the output impedance of the piezoelectric structure can surely be matched. Yet, after investigating the equivalent impedances of the existing harvesting interfaces, including standard energy harvesting (SEH), parallel synchronized switching harvesting on inductor (P-SSHI), and series synchronized switching harvesting on inductor (S-SSHI), we found that, their ranges are in fact limited. Therefore, to optimize the harvesting power, constrained matching instead of free matching should be adopted. In addition, we also clarify some confusing points in the previous literatures on impedance matching for energy harvesting. With the understanding on energy flow within piezoelectric devices, we know that only a portion of the extracted energy is able to be harvested, while the other is dissipated throughout the harvesting process. So even the extracted power from the source is maximized by matching the impedance; there is no guarantee that harvesting power is surely improved. The harvesting power also depends on the ratio between harvested energy and dissipated energy. These two issues discussed in this paper are crucial to improve the harvesting power and efficiency in piezoelectric energy harvesting systems.

Pipelines conveying gas under pressure exhibit turbulence-induced vibrations. The current work is concerned with extracting useful power from pipelines operating well within their stability region. At such regions, the pipe vibrations exist in small magnitudes and are unlikely to cause structural failure, yet can be exploited to provide useful energy for low-power electronic devices. Accordingly, emphasis in the present work is placed on the development of an energy harvesting technique employing the omnipresent and inevitable flow-induced vibrations in gas pipelines.

A new cantilevered piezoelectric energy harvester (PEH) of which the additional lumped mass is connected to a harmonically oscillating base through an elastic foundation is proposed for maximizing generated power and enlarging its frequency bandwidth. The base motion is assumed to provide a given acceleration level. Earlier, a similar energy harvester employing the concept of the dynamic vibration absorber was developed but the mechanism of the present energy harvester is new because it incorporates a mass-spring system in addition to a conventional cantilevered piezoelectric energy harvesting beam with or without a tip mass. Consequently, the proposed energy harvester actually forms a two-degree-of-freedom system. It will be theoretically shown that the output power can be indeed substantially improved if the fundamental resonant frequencies of each of the two systems in the proposed energy harvester are simultaneously tuned as closely as possible to the input excitation frequency and also if the mass ratio of a piezoelectric energy harvesting beam to the lumped mass is adjusted below a certain value. The performance of the proposed energy harvester is checked by numerical simulation.

The use of piezoelectric patches for actuation as a vibration control method has been widely investigated. Some of the uses for piezoelectric actuators include velocity feedback, synthetic impedance control, and a shunted sensor-actuator. Likewise, periodic structures have been shown to be effective in allowing the dissipation of travelling wave energy. The combination of these control procedures, an active periodic piezoelectric array, allows for enhanced vibration control. Presented here is the investigation of thin beam with 12 piezoelectric patch pairs. These patches will be shunted with varying selected impedances, specifically negative capacitive impedances, to allow for comparison of control ability. This comparison includes an analysis of spatial RMS velocity and numerical propagation constant.

Modified acceleration feedback (MAF) control, an active vibration control method that uses collocated piezoelectric actuator actuators and sensors is improved using an optimal controller. The controller consists of two main parts: 1) Frequency adaptation that uses Adaptive Line Enhancer (ALE), and 2) an optimal controller. Frequency adaptation tracks the frequency of vibrations using ALE. The obtained frequency is then fed to MPPF compensators and the optimal controller. This provides a unique feature for MAF, by extending its domain of capabilities from controlling tonal vibrations to broad band disturbances. The optimal controller consists of a set of optimal gains for wide range of frequencies that is provided, related to the characteristics of the system. Based on the tracked frequency, the optimal control system decides to use which set of gains for the MAF controller. The gains are optimal for the frequencies close to the tracked frequency. The numerical results show that the frequency tracking method that is derived has worked quite well. In addition, the frequency tracking is fast enough to be used in real-time controller. The results also indicate that the MAF can provide significant vibration reduction using the optimal controller.

The use of energy harvesting systems is becoming a more prominent research topic in supplying energy to wireless sensor nodes. The paper will present an analytical 'toolbox' for designing and modeling a vibration energy harvester where the moving mass is suspended magnetically. Calculations from the presented model and measurements from a prototype are compared, and the presence of system non-linearities is shown and discussed. The use of the magnetic suspension and its equivalent hardening spring suspension leads to the system's non-linearity, demonstrating a broad band response and 'jump' phenomenon characteristic. The benefits of these are discussed and the system's performance is compared with those from literature, showing similarity.

A novel hybrid energy harvester has been proposed which utilizes the presence of nonlinearity and multiple harvesting mechanisms to maximize the power output and the frequency bandwidth. The linear energy harvesters are frequency selective meaning they only generate power if they are excited accurately at their natural frequency. Nonlinear effects can make the harvester more broadband i.e. increase the efficient range of excitations frequency. We incorporate two magnets into the design, to have a nonlinear repulsive force acting on the beam. The piezoelectric patches and the electromagnetic coils convert the mechanical energy of the vibrations of the beam to electrical energy. The proposed energy harvester is therefore a hybrid energy harvester. The method of multiple scales is used to solve the nonlinear energy harvesting system. The electromechanical couplings have been considered in the nonlinear analysis. As a test the special case of linear piezoelectric harvesting has been revisited and the proposed solution precisely matches the exact solution in the literature. The paper concludes by predicting the performance of a fabricated harvester which shows the effectiveness of both nonlinear and hybrid harvesting.

We consider the performance of a vibration based energy harvester with realistic topologies for the electrical circuit, including power conditioning through a rectifier. Specifically we apply a novel perturbation approach to describe the time-varying power harvested in the system, including a rectifier in the circuitry. This approach considers the full electromechanical coupling between the mechanical and electrical components, including the amplitude and phase of the mechanical response. The resulting analysis is able to describe the behavior of the system as the mechanical response is detuned from resonance by the electrical load. In addition, the charging of the circuit over time is also captured by the analysis. Finally, the analytical results are compared against the numerical simulations of the original equations of motion to verify the analytical approach.

The results of the design and development of a new generation of electromagnetic-based energy harvesting systems that can be readily installed in various vehicles are presented. The device resembles a conventional damper or shock absorber that is commonly used for vehicle suspensions. Such devices have received increased attention in the recent years with the much publicized development of GenShock by a group of MIT students. The device described in this study is different than the GenShock technology in that it does not use any fluid, is simpler, and can potentially provide a larger amount of electrical power. The presentation will provide a detailed description of the development of a prototype energy harvester, including the modeling and analysis of the electromagnetic components for increased efficiency. The laboratory test results of the prototype system indicate that more than 20 Watts of RMS energy can be realized at displacements and velocities that resemble the relative motion across a vehicle suspension.

In many applications of vibratory energy harvesting, the external disturbance are most appropriately modeled as broadband stochastic processes. Optimization of power generation from such disturbances is a feedback control problem, and solvable via a LQG control theory. However, attainment of this performance requires the power conversion system which interfaces the transducers with energy storage to be capable of bi-directional power flow, and there are many applications where this is infeasible. One of the most common approaches to power extraction with one-directional power flow constraints is to control the power conversion system to create a purely resistive input impedance, and then to optimize this effective resistance for maximal absorption. This paper examines the optimization of broadband energy harvesting controllers, subject to the constraint of one-directional power flow. We show that as with the unconstrained control problem, it can be framed as a "Quadratic-Gaussian" stochastic optimal control problem, although its solution is nonlinear and does not have a closed-form. This paper discusses the mathematics for obtaining the optimal power extraction controller for this problem, which involves the stationary solution to an associated Bellman-type partial differential equation. Because the numerical solution to this PDE is computationally prohibitive for harvester dynamics of even moderate complexity, a sub-optimal control design technique is presented, which is comparatively simple to compute and which exhibits analyticallycomputable lower bounds on generated power Examples focus a nondimensionalized, ideal, base-excited SDOF resonator with electromagnetic transduction.

This paper presents a dual Adaptive Tuned Vibration Absorber (ATVA) using a magnetorheological elastomer (MRE) for powertrain torsional vibration control. The MRE used in this device is a soft MRE with a significant MR effect. By using the MRE, the ATVA can work in a wide frequency range. In this paper, the dual ATVA is proposed rather than a single ATVA because a single ATVA, at a fixed location, cannot deal with resonances happening to several powertrain vibration modes. Also, the dual ATVA concept design is presented to validate its effectiveness. In addition the soft MRE shear modulus is approximated by a polynomial of magnetic flux intensity B and the approximation was experimentally validated. The simulation results showed that with the ATVA, powertrain vibration response is significantly suppressed. Furthermore, the effect of the dual ATVA parameters such as inertia moment, stiffness and damping coefficients and ATVA locations were examined. The dual ATVA will be useful device for powertrain vibration suppression.

This paper is aimed at developing a novel multifunctional actuator utilizing magnetorheological (MR) fluids. As a key component for assistive knee braces, the actuator can work with multiple functions as motor, clutch and brake in order to meet the requirement of normal human walking. In this paper, design considerations including configurations, materials selection, mechanical and electromagnetic designs are illustrated. Prototype of the multifunctional actuator is fabricated, and each of its functions is investigated. Control strategies for mimicking normal human walking using the multifunctional actuator are illustrated. Adaptive control algorithm is adopted. Experiments on torque and speed tracking are conducted. The results show that the developed multifunctional actuator is promising for assistive knee braces.

In this study a compact compressible magneto-rheological (MR) fluid damper-liquid spring (CMRFD-LS) with high spring rate is designed, developed and tested. The proposed device consists of a cylinder and piston-rod arrangement, with an annular MR fluid valve. The internal pressures in the chambers on either side of the piston develop the spring force, while the pressure difference across the MR valve produces the damping force, when the fluid flows through the MR valve. A fluid mechanics-based model is conducted to predict the behavior of the damper device under sinusoidal input. The device is studied under oscillatory vibrations for various frequencies and applied magnetic fields. The experimental results are in good agreement with the theoretical predictions.

A magnetorheological shock absorber (MRSA) prototype is designed, fabricated and tested to integrate semiactive shock and vibration mitigation technology into the existing Expeditionary Fighting Vehicle (EFV) forward seating positions. Utilizing Bingham-Plastic (BP) constitutive fluid relationships and a steady state fluid flow model, the MR valve parameters are determined using magnetic circuit analysis, and subsequently validated via electromagnetic finite element analysis (FEA). Low speed (up to 0.9 m/s) simulations of normal vibration mode operation are conducted on the MRSA prototype using single frequency sinusoidal displacements by a servohydraulic testing machine. The high speed (up to 2.2 m/s) design procedure is verified by using a rail-guided drop test stand to impact a known payload mass onto the damper shaft. A refined hydromechanical model of the MRSA under both cyclic and impact loadings is developed and validated using the measured test data. This ratedependent, mechanisms-based model predicts the time response of the MRSA under both loading conditions. The hydromechanical analysis marks a significant improvement over previous linear models. Key design considerations for the MRSA to accommodate both vibration and shock spectra using a single MR device are presented.

While few publications exist on the behavior of Magneto-Rheological (MR) fluid in squeeze mode, devices using squeeze mode may take advantage of the very large range of adjustment that squeeze mode offers. Based on results obtained through modeling and testing MR fluid in a squeeze mode rheometer, a novel compression-adjustable element has been fabricated and tested, which utilizes MR fluid in squeeze mode. While shear and valve modes have been used exclusively for MR fluid damping applications, recent modeling and testing with MR fluid has revealed that much larger adjustment ranges are achievable in squeeze mode. Utilizing squeeze mode, a compression element, or MR Pouch, was developed consisting of a flexible cylindrical membrane with each end fastened to a steel endplate (pole plates). The silicone rubber pouch material was molded in the required shape for use in the squeeze mode rheometer. This flexible membrane allows for the complete self-containment of MR fluid and because the pouch compensates for volume changes, there is no need for dynamic seals and associated surface finish treatments on the steel components. An electromagnet incorporated in the rheometer passes an adjustable magnetic field axially through the pole plates and MR fluid. Test results show the device was capable of varying the compression force from less than 8lbs to greater than 1000lbs when the pole plates were 0.050" apart. Simulations were compared against test data with good correlation. Possible applications of this technology include primary suspension components, auxiliary suspension bump stops, and other vibration isolation components, as MR Pouches are scalable depending on the application and force requirements.

Modern vehicles have been increasingly equipped with advanced technologies such as hybrid and cylinder-on-demand to enhance fuel efficiency. These technologies also come with vibration problems due to the switching between the power sources or the variation of the number of active cylinders. To mitigate these vibrations, a large variety of vibration isolators have been proposed, ranging from passive to active isolators. Semi-active mounts are often preferred to other solutions because of their overall low power requirement in operation as well as relatively simpler configurations. Among the semi-active categories, the magnetorheological fluid (MRF) mounts have been proven to be a viable solution for modern vehicle vibration isolation. These mounts can change their stiffness and damping characteristic without involving moving parts, by controlling the yield stress of the MRF housed inside the mount by means of magnetic field. This study looked into several innovative designs for MRF mounts. The characteristics of the mount depend significantly on the compliances of the rubber, the number and arrangement of the fluid chambers and the number of flow passages connecting the chambers. These parameters provide the designers with various options to design the mounts to function in various conditions and over a wide range of frequencies. Different values of the aforementioned parameters were selected to form specific designs with certain characteristics. Mathematical models have been developed for each design and MATLAB/Simulink was used to simulate the response of each mount to certain excitations. As the hydraulic and magnetorheological (MR) effects are dominant in the mount, the elastomer behavior is considered linear. A discussion of the advantages and disadvantages of each design, based on the simulated response, is presented. The outcomes of this study can be a useful reference for MRF mount designers and leads to the development of a general MRF mount design methodology.

This paper presents simulated and experimental results on the flow induced in a closed channel by a magnetic fluid (i.e. magnetorheological (MR) fluid and a ferrofluid) plunger. The results are used to assess the feasibility of using such fluids for development of milli-micro-scale pumps. The magnetic fluid plunger acts as a piston that is moved along the channel by an array of drive coils (or by a permanent magnet) to displace an immiscible fluid. The excited drive coils produce a traveling magnetic field wave inside the channel which in turn produces magnetic dipoles in the magnetic fluid. The dipoles react with the traveling wave leading to a Kelvin force that drags the magnetic fluid plunger through the channel. The flow rates achievable in this approach are a function of channel geometry, magnetic fluid properties, plug size, frequency of the current passing through the drive coils, and the location of the drive coils along the channel. Representative results of the analysis of the effect of these parameters on the flow rates are presented here. While the simulations indicate that both, MR and ferrofluids may be used for fluid actuation in the selected geometry, the experiments validated only the MR fluid option.

A novel energy harvesting device powered by aeroelastic flutter vibrations is proposed to generate power for embedded wireless sensors on a helicopter rotor blade. Such wireless sensing and on-board power generation system would eliminate the need for maintenance intensive slip ring systems that are required for hardwired sensors. A model of the system has been developed to predict the response and output of the device as a function of the incident wind speed. A system of coupled equations that describe the structural, aerodynamic, and electromechanical aspects of the system are presented. The model uses semi-empirical, unsteady, nonlinear aerodynamics modeling to predict the aerodynamic forces and moments acting on the structure and to account for the effects of vortex shedding and dynamic stall. These nonlinear effects are included to predict the limit cycle behavior of the system over a range of wind speeds. The model results are compared to preliminary wind tunnel tests of a low speed aeroelastic energy harvesting experiment.

In this paper, we integrate piezoelectric transducers and coupled circuitry, which themselves form an electrical periodic system, onto a mechanical structure to form an electro-mechanical periodic system. The overall dynamics of the electro-mechanical system can thus be altered by tuning the electrical parameters. A transfer-matrix-based modeling technique is adopted in the dynamic analysis, where each element is represented by two state vectors at its both ends with a transfer matrix relating them. As the transfer matrix has the advantage on describing harmonic motions within the element, the global analysis can be facilitated given the repetitive nature of periodic systems. Numerical simulations are conducted to demonstrate the characteristics of wave propagation and attenuation in terms of propagation constants. Effects of each tunable parameter are also discussed through detailed parametric analysis. The proposed system can be tailored to various engineering needs. One example is adaptive vibration isolation with tunable effective frequency range. Another example is vibration energy harvesting through the piezoelectric transducers and circuitry.

The certification of retro-fitted structural health monitoring (SHM) systems for use on aircraft raises a number of challenges. One critical issue is determining the optimal means of supplying power to these systems, given that access to the existing aircraft power-system is often problematic. Previously, the DSTO has shown that a structural-strain based energy harvesting approach can be used to power a device for SHM of aircraft structure. Acceleration-based power harvesting from airframes can be more demanding than a strain based approach because the vibration spectrum of an aircraft structure can vary dynamically with flight conditions. A vibration spectrum with varying frequency may severely limit the power harvested by a single-degree-of-freedom resonance-based device, and hence a frequency agile or (relatively) broadband device is often required to maximize the energy harvested. This paper reports on an investigation into the use of a vibro-impact approach to construct an acceleration-based power harvester that can operate in the frequency range 29-41 Hz.

In much of the vibration-based energy harvesting literature, devices are modeled, designed, and tested for dissipating energy across a resistive load at a single base excitation frequency. This paper presents several practical scenarios germane to tracking, sensing, and wireless communication on humans and land vehicles. Measured vibrational data from these platforms are used to provide a time-varying, broadband input to the energy harvesting system. Optimal power considerations are given for several circuit topologies, including a passive rectifier circuit and active, switching methods. Under various size and mass constraints, the optimal design is presented for two scenarios: walking and idling a car. The frequency response functions are given alongside time histories of the power harvested using the experimental base accelerations recorded. The issues involved in designing an energy harvester for practical (i.e. timevarying, non-sinusoidal) applications are discussed.

Wave motions represent a source of substantial untapped energy. Given the current interest in renewable power, research continues into the development of wave energy harvesting devices. An evaluation of existing wave energy harvester designs has shown that there are a number of different methods typically used to carry out the mechanical-to-electrical energy conversion process. A common observation is that existing designs only use a subset of possible wave motions to generate electrical energy; while heaving motions are commonly used, other forms of translational and rotational motion such as swaying, pitching and rolling remain unutilised. This paper evaluates the feasibility of a multidimensional wave energy harvester that is able to harvest electrical energy using six degrees-of-freedom. A design for an inertial energy harvesting system is presented, with a suspended proof mass and electromagnetic transducers allowing energy to be harvested from multiple translational and rotational wave motions. A computer-based model of the system is created, allowing the performance of the device to be simulated for a given set of wave motions. Using real-world wave data captured by a data logging buoy, a peak electrical power output in excess of 600mW is obtained.

Size and power requirements of wireless sensor nodes are gradually decreasing and this has allowed data collection across a range of spatial and temporal ranges. These nodes have power requirements that often necessitate batteries as an energy source. As the power requirements decrease for these sensors, alternative energy sources become more attractive. One such technology is thermal energy harvesting. Thermal energy harvesting requires a differential temperature between a heat source and a cool sink. As heat energy flows from source to the sink, energy can be harvested and utilized to power sensor nodes. By exploiting the temperature difference between a sun-warmed plate and a heat sink immersed in water, electrical energy can be harvested. The proposed concept utilizes a thermoelectric device to convert solar energy into electrical power. Initial experiments were carried out at the CSIRO Energy Centre for a variety of winter time intervals in 2009, with peak power outputs in the order of 50mW. Results indicate such a system could power a wireless sensor node continuously at ocean, lake and river water interfaces. We are presently in the process of evaluating the concept by powering a CSIRO Fleck^TM wireless node to transmit water temperature and battery voltage data.

Wind loading from turbulence and gusts can cause damage in horizontal axis wind turbines. These unsteady loads and the resulting damage initiation and propagation are difficult to predict. Unsteady loads enter at the rotor and are transmitted to the drivetrain. The current generation of wind turbine has drivetrain-mounted vibration and bearing temperature sensors, a nacelle-mounted inertial measurement unit, and a nacelle-mounted anemometer and wind vane. Some advanced wind turbines are also equipped with strain measurements at the root of the rotor. This paper analyzes additional measurements in a rotor blade to investigate the complexity of these unsteady loads. By identifying the spatial distribution, amplitude, and frequency bandwidth of these loads, design improvements could be facilitated to reduce uncertainties in reliability predictions. In addition, dynamic load estimates could be used in the future to control high-bandwidth aerodynamic actuators distributed along the rotor blade to reduce the saturation of slower pitch actuators currently used for wind turbine blades. Local acceleration measurements are made along a rotor blade to infer operational rotor states including deflection and dynamic modal contributions. Previous work has demonstrated that acceleration measurements can be experimentally acquired on an operating wind turbine. Simulations on simplified rotor blades have also been used to demonstrate that mean blade loading can be estimated based on deflection estimates. To successfully apply accelerometers in wind turbine applications for load identification, the spectral and spatial characteristics of each excitation source must be understood so that the total acceleration measurement can be decomposed into contributions from each source. To demonstrate the decomposition of acceleration measurements in conjunction with load estimation methods, a flexible body model has been created with MSC.ADAMS© The benefit of using a simulation model as opposed to a physical experiment to examine the merits of acceleration-based load identification methods is that models of the structural dynamics and aerodynamics enable one to compare estimates of the deflection and loading with actual values. Realistic wind conditions are applied to the wind turbine and used to estimate the operational displacement and acceleration of the rotor. The per-revolution harmonics dominate the displacement and acceleration response. Turbulent wind produces broadband excitation that includes both the harmonics and modal vibrations, such as the tower modes. Power Spectral Density estimates of the acceleration along the span of the rotor blades indicate that the edge modes may be coupled to the second harmonic.

Based on flexible spacecrafts, the isolation performance of whole-spacecraft vibration isolators is studied in this paper. A new type of discrete whole-spacecraft vibration isolation platforms is used and the dynamical equations of the systems are established. The transmissibility from the bottom of the isolator to some key points on the flexible spacecraft is computed. The isolation performance of the vibration isolation coupling systems for the flexible spacecraft is analyzed by complex modal method and investigated by vibration table experiment. The analysis results and the testing data show that the discrete whole-spacecraft vibration isolation platforms have good isolation performance in wide frequency range to lateral and longitudinal vibration, and the vibration isolation platforms can be applied to actual flexible spacecrafts.

The Institute for Production Engineering and Forming Machines at the Technische Universität Darmstadt examines the reduction of uncertainty of bar structures by integrating adaptive components into the bars. As sensors, these components allow a monitoring of appearing loads, as actuators they allow an active influencing on appearing disturbances. One approach for producing those structures is given by incremental forming processes. They feature the advantage to combine the forming of the parts as well as the integration of the active components in one process. The research contains numerical analyses and experimental tests.

The vibration control module known as IQ damper had been developed as part of active vibration damping system for optical tables and other precision vibration isolated platforms. The present work describes steps to expand the application of these units to other tasks, namely, (1) dynamic testing of structures and (2) compensation of forced vibration in local areas. The sensor-actuator assembly, including signal conditioning circuits, is designed as a compact dynamically symmetric module with mechanical interface to an optical table. The test data show that the vibration control modules can be used to measure dynamic compliance characteristics of optical tables with precision comparable to that of dedicated vibration measurement systems. Stable concerted work of active vibration control modules compensating forced harmonic vibration is demonstrated experimentally.

We conducted various investigation of energy recycling semi-active vibration suppression method by using piezoelectric transducers attached to structures. In this method, piezoelectric transducers are connected to a shunt circuit with diodes and an inductance, and it makes better use of counter electromotive force to suppress the vibration. We had proposed some new ideas in order to upgrade this method. And we verified their high performances compared to conventional semi-active method by many experiments. In results of experiment that practically apply this method to an actual satellite structural model using lots of the piezoelectric transducer, it was found that vibration suppression performance depend on how piezoelectric transducers were connected each other. It is because their connection affects a resonance frequency and a total resistance of the shunt circuit. The performance of the method related to the connection of the piezoelectric transducers and their resistances dependent on frequency are described using experimental results in this paper.

As storage data density in hard-disk drives (HDDs) increases for constant or miniaturizing sizes, precision positioning of HDD heads becomes a more relevant issue to ensure enormous amounts of data to be properly written and read. Since the traditional single-stage voice coil motor (VCM) cannot satisfy the positioning requirement of high-density tracks per inch (TPI) HDDs, dual-stage servo systems have been proposed to overcome this matter, by using VCMs to coarsely move the HDD head while piezoelectric actuators provides fine and fast positioning. Thus, the aim of this work is to apply topology optimization method (TOM) to design novel piezoelectric HDD heads, by finding optimal placement of base-plate and piezoelectric material to high precision positioning HDD heads. Topology optimization method is a structural optimization technique that combines the finite element method (FEM) with optimization algorithms. The laminated finite element employs the MITC (mixed interpolation of tensorial components) formulation to provide accurate and reliable results. The topology optimization uses a rational approximation of material properties to vary the material properties between 'void' and 'filled' portions. The design problem consists in generating optimal structures that provide maximal displacements, appropriate structural stiffness and resonance phenomena avoidance. The requirements are achieved by applying formulations to maximize displacements, minimize structural compliance and maximize resonance frequencies. This paper presents the implementation of the algorithms and show results to confirm the feasibility of this approach.

This paper presents an innovative concept, control strategies and experimental verification of simultaneous thrust vector control and vibration isolation of satellites. First, the innovative concept is introduced by employing a smart platform as an active structural interface between the main thruster of a satellite and the satellite structure. Second, the inverse kinematics and singularity analysis of the smart platform are performed. Third, thrust vector control model of satellites with smart platforms is deduced. Fourth, a multiple loop control strategy is proposed. It includes three cascaded feedback loops for nonlinear compensation of actuators, smart platform control and trust vector control, respectively, and a combined feedback-feedforward control scheme for vibration isolation. Finally, experiments are carried out and experimental results are illustrated and discussed. The cascaded multiple feedback loops compensate the hysteresis (for piezoelectric stacks inside the three linear actuators that individually have simultaneous precision positioning and vibration suppression), dead-zone, back-lash, and friction nonlinearities very well, and provide precision and quick smart platform control and satisfactory thrust vector control capability. The experimental results demonstrate that the simultaneous thrust vector control and vibration suppression is achieved with satisfactory performance.

The performance (drag, lift, stability, etc.) of a parachute is a function of the physical properties of the canopy fabric (such as porosity) and geometry of the canopy (such as air-vent openings). These variables typically remain constant during descent and therefore the parachute retains constant drag and lift. The ability to change these variables and the parachute drag and lift characteristics during flight will greatly widen the performance envelope of a parachute, the maneuverability, and versatility of the airdrop mission. This paper provides a literature review of existing smart material technologies in an effort to improve the performance characteristics and enhance the safety of existing parachutes and parafoils by incorporating these advanced materials into parachute systems.

Insects are impressive natural flyers. They fly with high agility and maneuverability by flapping their wings. Emulating their flight capability and flight mechanisms may provide a good start in the design of a micro air vehicle (MAV). In this paper, wing flappers are designed and developed with reference to the blueprint of the flight thorax of insects. The developed wing flappers consist of a thoracic frame structure as a flapping mechanism and a vibration motor as a driver. The bio-inspired thorax design is evaluated and its performances are compared with those of the flapping wing insects. The initial prototype demonstrates that the wing flappers are comparable to the insects in terms of the wingbeat frequency and body mass. The initial wing flappers can flaps at a flapping angle of 30°. In addition, simplified analytic model of the wing flappers are derived to optimized the design. Upon redesigned, an improved wing flappers can flaps at a large flapping angle of 75°.

As an effort to explore the potential implementation of wing feather separation and lead-lagging motion to a flapping wing, a biomimetic flapper with separable outer wings has been designed and demonstrated. The artificial wing feather separation is implemented to the biomimetic wing by dividing the wing into inner and outer wings. The features of flapping, lead-lagging and feather separation of the flapper are captured by a high-speed camera for evaluation. The performance of the biomimetic flapper with separable outer wings is compared with that of a flapper with inseparable outer wings in terms of lift and thrust production. For low flapping frequency ranging from 2.47 Hz to 3.90 Hz, the biomimetic flapper shows higher thrust and lift generation capability, which is demonstrated from a series of experiments. The experiments show that the outer parts of the separable wing are able to deform largely resulting smaller amount of drag production during upstroke, while still producing relatively larger lift and thrust during downstroke.

This paper presents a concept of a fish robot actuated by an SMA-based actuator. The bending-type actuator system is composed of a 0.1mm diameter SMA wire and a 0.5mm thick glass/epoxy strip. The SMA wire is installed to the bent composite strip. The actuator can produce about 200gf of blocking force and 3.5mm displacement at the center of the glass/epoxy strip. The bending motion of the actuator is converted into the tail-beat motion of a fish robot through a linkage system. The fish robot is evaluated by measuring the tail-beat angle, swimming speed and thrust produced by the fish robot. The tail-beat angle is about 20° and the maximum swimming speed is about 1.6cm/s. The measured thrust is about 0.4gf when the fish robot is operated at 0.9Hz.

We have studied a biomimetic swimmer inspired by the motility mechanisms of bacteria such as E. coli theoretically and experimentally. Even though E. coli uses one or several rotating helical filaments to swim, a single rotating helical filament swimmer is considered in this work. The performance of this swimmer was estimated by modeling the dynamics of a swimmer in viscous fluid. The model has an ellipsoidal cell body propelled by a helical filament. We applied the resistive force theory on this model to calculate the linear swimming speed and the efficiency of the model. A parametric study on the swimming velocity was performed. To validate the theoretical results, a biomimetic swimmer was fabricated and an experiment setup was prepared to measure the swimming speed in silicone oil. In addition, we have studied the flow patterns surrounding the filament with a finite element simulation to understand the mechanism of propulsion.

In this paper, the influence of carbon nanotube functionalization on interfacial shear strength and hence on damping characteristics of CNT-based polymeric composites is investigated with a multiscale model. The sequential multiscale approach consists of two parts. First, the interfacial shear strength between the functionalized nanotube and the polymer is calculated by simulating a CNT pull-out test using the molecular dynamics method. The strength values obtained from atomic simulation are then applied to a micromechanical damping model of a representative unit cell of a CNT/polymer composite under cyclic loading. The analysis results indicate that the nanotube functionalization increases the interfacial shear strength. The increased shear strength can either enhance or reduce the effective loss factor of the composite, depending on the operational stress range.

As a result of the relatively low intrinsic damping in printed circuit boards, vibration and acoustic energy present in the operating environment may excite vibration modes in the PCB that lead to deleterious effects in attached vibration sensitive components, such as MEMS gyroscopes. An investigation of the use of sandwiched layers of microfibrous metallic cloth in contact with the PCB to increase damping was investigated. Tests were performed for both vibration excitation and acoustic excitation. The initial results indicate that mechanical damping can be increased through this approach.

A piezohydraulic microjet design and experimental results are presented to demonstrate broadband active flow control for applications on various aircraft structures including impinging jets, rotor blades, cavity bays, etc. The microjet actuator includes a piezoelectric stack actuator and hydraulic circuit that is used to throttle a 400 μm diameter microjet using hydraulic amplification of the piezoelectric stack actuator. This system is shown to provide broadband pulsed flow actuation up to 800 Hz. Unsteady pressure measurements of the microjet's exit flow are coupled with high-speed phase imagery using micro-Schlieren techniques to quantify the flow field. These results are compared with in situ stack actuator displacements using strain gauge measurements.

This research seeks to develop a novel branch of materials systems called Distributed Intelligent Materials Systems (DIMS) which incorporate actuation, sensing, electronics and intelligence as inherent parts of the material structure. A microcantilever optical switch is fabricated as a concept demonstrator with Gallium nitride (GaN) as host material. GaN has several material characteristics which enable it to outperform other semiconductor materials for electronic applications. It also displays exceptional chemical inertness, has a relatively high piezoelectric coefficient, good mechanical strength and toughness and is transparent to wavelengths in the visible spectrum. In this paper we develop and fabricate a GaN-based, piezoelectrically actuated microcantilever optical switch/waveguide. While the GaN-material offers the benefits mentioned above, the piezoelectric actuation and the cantilever design provide benefits of lighter weight, compactness, speed of actuation, reduced structural complexity enabling easier fabrication and low wear and tear due to minimal moving parts. The proposed design has a conventional unimorph configuration with GaN actuated in d31 mode. In this configuration, a laminar metal electrode and a doped n-type GaN layer are used to apply an electric field in the top layer to actuate the unimorph. The unimorph is fabricated as a micro-cantilever by using surface micromachining methods on epitaxial GaN grown on a GaN substrate. The cantilever is then etched partially using conventional semiconductor processing techniques and using a recent microfabrication technique known as photoelectrochemical (PEC) etch. PEC etching enables the fabrication of MOEMS structures that are rather difficult to create using conventional methods. Novel modifications and improvements to the current state-of-the art in PEC for GaN are presented and discussed.

We report on using e-beam lithographically technology for enabling the mass replication of custom-designed and prepared Nano-structures via establishing nanoimprint processes for pattern transfer into UV curable prepolymes. By EBL, the new nano-fabrication technology based on the concept of disposal master technology (DMT) is suitable for mass volume manufacturing of large area arrays of sub-wavelength photonic elements. We will present some kinds of PhC and waveguides for fabrication of nanoimprint Electron beam lithography stamps.

Recently, a new biological-inspired fluidic flexible matrix composite (in short, F²MC) concept has been developed for linear/torsional actuation and structural stiffness tailoring. Although the actuation and the variable stiffness features of the F²MC have been successfully demonstrated individually, their combined functions and full potentials were not yet manifested. In addition, the current hydraulic pressurization systems are bulky and heavy, limiting the potential of the F²MC actuator. To address these issues, we synthesize a new variable stiffness actuator concept that can provide both effective actuation and tunable stiffness (dual-mode), incorporating the F²MC with a compact piezoelectric-hydraulic pump (in short, PHP). This dual-mode mechanism will significantly enhance the potential of the F²MC adaptive structures.

The field of structural health monitoring (SHM) has made significant contributions in the field of prognosis and damage detection in the past decade. The advantageous use of this technology has not been integrated into operational structures to prevent damage from propagating or to heal injured regions under real time loading conditions. Rather, current systems relay this information to a central processor or human operator, who then determines a course of action such as altering the mission or scheduling repair maintenance. Biological systems exhibit advanced sensory and healing traits that can be applied to the design of material systems. For instance, bone is the major structural component in vertebrates; however, unlike modern structural materials, bone has many properties that make it effective for arresting the propagation of cracks and subsequent healing of the fractured area. The foremost goal for the development of future adaptive structures is to mimic biological systems, similar to bone, such that the material system can detect damage and deploy defensive traits to impede damage from propagating, thus preventing catastrophic failure while in operation. After sensing and stalling the propagation of damage, the structure must then be repaired autonomously using self healing mechanisms motivated by biological systems. Here a novel autonomous system is developed using shape memory polymers (SMPs), that employs an optical fiber network as both a damage detection sensor and a network to deliver stimulus to the damage site initiating adaptation and healing. In the presence of damage the fiber optic fractures allowing a high power laser diode to deposit a controlled level of thermal energy at the fractured sight locally reducing the modulus and blunting the crack tip, which significantly slows the crack growth rate. By applying a pre-induced strain field and utilizing the shape memory recovery effect, thermal energy can be deployed to close the crack and return the system to its original operating state. The entire system will effectively detect, self toughen, and subsequently heal damage as biological materials such as bone does.

Two of the main components of cell membranes are lipids and proteins. Lipids are the passive structure of the membrane that acts as a barrier between the inner and outer portions of the cell. Proteins are the active structure of the membrane that allows signaling, energy conversion, and open channels between the inner and outer portions of the cell. Artificially made membranes, called bilayers, can be made from natural or artificial membrane components at the interface of aqueous volumes. Some bilayer properties are measured by inducing an artificial potential gradient across the bilayer to induce ion flow. This ion flow is measured by measuring the resulting current output of the device that induced the potential gradient. The lipids of the membrane act electrically as a small conductor and capacitor in parallel where the measured capacitance is related to the area of the bilayer. Some proteins act electrically as an additional conductor in parallel to the lipids with varying conductance properties depending on the specific protein. Some proteins are pores that allow ions to flow freely through the membrane and others are gated and allow ions to flow at different levels depending on the size and polarity of the potential gradient. A large system with multiple aqueous volumes and multiple bilayers made of just passive membrane components can be modeled as an electrical network of resistors and capacitors. The addition of proteins to this network increases the complexity of the system model because the proteins usually do not act as a linear conductance and numerical methods are used to approximate what is happening in the system. This paper shows how a system of multiple aqueous volumes and multiple bilayers can be modeled as a system of first order odes, numerically solved, and then compared to the published results of a similar system.

Biomolecular networks formed from droplet interface bilayers (DIB) use principles of phase separation and molecular self-assembly to create a new type of functional material. The original DIB embodiment consists of lipid-encased aqueous droplets surrounding by a large volume of oil contained in a shallow well. However, recent results have shown that, by reducing the amount of oil that separates the droplets from the supporting substrate, physically-encapsulated DIBs display increased durability and portability. In this paper we extend the concept of encapsulated biomolecular networks to one in which phase separation and molecular self-assembly occur entirely within internally-structured reservoirs of a solid material. Flexible substrates with 200μm wideby- 200μm deep internal microchannels for holding the aqueous and oil phases are fabricated from Sylgard 184 polydimethylsiloxane (PDMS) using soft-lithography microfabrication techniques. Narrowed apertures along the microchannels enable the use of the regulated attachment method (RAM) to subdivide and reattach lipid-encased aqueous volumes contained within the material with an applied external force. The use of perfluorodecalin, a fluorocarbon oil, instead of hexadecane eliminates absorption of the oil phase into the PDMS bulk while a silanization surface treatment of the internal channel walls maximizes wetting by the oil phase to retain a thin layer of oil within the channels to provide a fluid oil/water interface around the aqueous volumes. High-quality 1,2-diphytanoyl-sn-glycero-3-phosphocholine (DPHPC) lipid bilayers formed within the prototype substrates have electrical resistance between 1-100GΩ, enabling the measurement of single and few-channel recordings of alpha-hemolysin (αHL) and alamethicin proteins incorporated into the bilayers.

This paper is centered on a new actuation philosophy executed on an old rotor design. An adaptive rotor employing twist-active piezoelectric root actuators was used as a testbed to investigate the new branch of structural mechanics devoted to low- and zero-net passive stiffness (ZNPS) structures. One of the more common methods to achieve zero net passive stiffnesses in structures is to employ "negative" springs: that is, mechanisms which when combined with the baseline structure null the passive stiffness of the total structural element. This paper outlines the application of such a system via a Post-Buckled Precompression (PBP) technique at the end of a twist-active piezoelectric rotor blade actuator. The basic performance of the system is handily modeled by using laminated plate theory techniques. A dual cantilevered spring system was used to increasingly null the passive stiffness of the root actuator along the feathering axis of the rotor blade. As the precompression levels were increased, it was shown that corresponding blade pitch levels also increased. The PBP cantilever spring system was designed so as to provide a high level of stabilizing pitch-flap coupling and inherent resistance to rotor propeller moments. Experimental testing showed pitch deflections increasing from just 8° peak-to-peak deflections at 650 V/mm field strength to more than 26° at the same field strength with design precompression levels. Dynamic testing showed the corner frequency of the linear system coming down from 63 Hz (3.8/rev) to 53Hz (3.2/rev). Thrust coefficients manipulation levels were shown to increase from 0.01 to 0.028 with increasing precompression levels. The paper concludes with an overall assessment of the actuator design and conclusions on overall feasibility.

This paper presents a detailed analysis of the deflection of the shim stacks used in hydraulic dampers. In hydraulic dampers, a stack of circular disks (shims) is mounted on each side of the main piston to create a pressure drop as the hydraulic oil is passed through the piston from one side to the other. A stiff shim stack creates a high pressure drop across the piston, resulting in high damping. A softer shim stack creates less pressure drop and smaller damping. In practice, shims can be added or removed from the shim stack assembly to tune the damper and generate the desired damping force characteristics as a function of velocity. Tuning a damper requires taking the damper apart, making the changes to the shim stack assembly, and putting the damper back together. This takes a considerable amount of time and effort. Therefore, mathematical modeling of the shim stack assembly becomes a crucial part of the analysis of hydraulic dampers. The goal of the study presented here is to provide a model of the shim stack assembly in order to accurately predict the level of damping for different configurations of the shim stack. The shims that are stacked on each other will deflect under the pressure created by the hydraulic oil, and at the same time, slide against each other. This important characteristic of the shim stack needs to be accounted for in the mathematical model and makes the analysis complicated. For the sake of simplicity, in past studies the shim stack is approximated by the deflection of a single disk and formulas for a single disk are used. This, however, introduces a significant amount of error in the damper hydraulic model. In this paper, the deflection of shim stacks is analyzed and compared with the single disk approximation. It is found that this approximation fails to agree with the more accurate model of representing the shims individually. Therefore, a more detailed and accurate model is necessary for better simulating the damping characteristics of hydraulic dampers as a function of relative velocity across the damper.

In this paper, a robust free space optical coupling of reflection-based fiber Bragg grating (FBG) sensors is presented. Fiber Bragg grating (FBG) sensors have shown great utility for integrity management and environmental sensing of composite structures. However, they suffer from cumbersome and fragile techniques for bringing the sensing light into and out of the structure since the optical fiber must be routed through the surface of the composite (i.e. pigtailing). In our approach, 45-degree-angled mirrors integrated into fibers were used as an input and output coupling technique. With the difficulty of directly free space coupling to the tiny single mode fiber (SMF), a novel method of coupling to the sensor via splicing and fusing a multimode fiber (MMF) to the single mode FBG (SMFBG) was explored. Using this method, we have previously demonstrated free space optical coupling to transmission-based FBG sensors embedded inside a composite panel. In this paper, we are able to interrogate un-embedded sensors with reflected light using 45-degree-angled mirrors. We have also performed preliminary investigation on FBG sensors embedded in a composite panel. We conclude that this novel space coupling method can be used to effectively couple the transmitted and reflected light for FBG sensors.

Shape adaptive systems and structural configurations are necessary to fulfill the demands of a future unmanned aerial vehicle structure. Predominantly the present approaches are based on a passive load-bearing structure having smart actuation systems deforming the passive structural configuration elastically in the wanted shape. Therefore the actuation system can be based on discrete actuators, like electrically driven motors using gearing systems to transform the displacement into the structure or on smart material configurations placed on the load bearing passive structure, deforming the structure within the elastic region into the wanted shape. Using smart materials within load-bearing structures, elastic and static strength properties vary between passive and active structures. Matching these properties is a great challenge for future structural configurations. This is a successful approach for certain applications, e.g. smart rotor blade. The availability of two-dimensional smart actuator configurations with distinct actuation orientation allows the definition of a distinct load bearing active structure. Therefore the so called "web" of a spar-equivalent configuration was substituted by such a smart material actuator also known as macro fiber composite (MFC). Activating the web of the active cantilevered spar-configuration is resulting in a free end displacement. The main advantage lies in the fact that this approach will allow larger active displacements in comparison to a passive structural configuration with applied smart material actuators. Within the paper the process of developing the shear web based actuation system with configuration details will be illustrated and future steps will be proposed.

An energy method is used in order to derive the non-linear equations of motion of a smart flapping wing. Flapping wing is actuated from the root by a PZT unimorph in the piezofan configuration. Dynamic characteristics of the wing, having the same size as dragonfly Aeshna Multicolor, are analyzed using numerical simulations. It is shown that flapping angle variations of the smart flapping wing are similar to the actual dragonfly wing for a specific feasible voltage. An unsteady aerodynamic model based on modified strip theory is used to obtain the aerodynamic forces. It is found that the smart wing generates sufficient lift to support its own weight and carry a small payload. It is therefore a potential candidate for flapping wing of micro air vehicles.

The concept proposed in thei work for chord extension is the use of a bistable arch and thin plate system. There are two foci of this paper: (1) Design of the arch and (2)Model validation via experiment. Results show that bistability and symmetric deformation can be achieved when there are flexible hinges at the boundary and input. In addition, the presented finite element model provides good agreement with experimental results.

This paper presents an analysis of close proximity aerodynamics and aircraft dynamics of two Linked UAVs. As the UAVs approach each other for wingtip docking there will be strong aerodynamic coupling between their wings tips. Lifting line and Computational Fluid Dynamics (CFD) simulation as well as wind tunnel testing of close proximity effects on lift, drag, roll, pitch and yaw moments for two UAV wings has been performed. The proximity aerodynamics effects between the UAVs wings were analyzed as a function of its relative position in all three directions. A look-up library of aerodynamic forces and moments for relative positions and angles of attack between the two UAVs has been developed. In this study we examined how the close proximity aerodynamics affects the dynamics and stability of the UAVs. The aircraft dynamics analysis is done in Simulink, which will include the close proximity aerodynamic look-up library. An aerodynamic disturbance intensity field will be generated, utilizing both simulation and wind tunnel data, to determine a trajectory for the two UAVs to approach each other for docking.

The design of stable trim conditions for forward flight and for hover has been achieved. In forward flight, an ornithopter is configured like a conventional airplane or large bird. Its fuselage is essentially horizontal and the wings heave in a vertical plane. In hover, however, the body pitches vertically so that the wing stroke in the horizontal plane. Thrust directed downward, the vehicle remains aloft while the downdraft envelops the tail to provide enough flow for vehicle control and stabilization. To connect these trajectories dynamically is the goal. The naïve approach-to choose two stable trajectories and switch between them-has been accomplished. A new approach is to establish an open-loop trajectory through a trajectory optimization algorithm-optimized for shortest altitude drop, shortest stopping distance, or lowest energy consumption.

This paper investigates the effectiveness of two adaptive control strategies for modulating control force of piezoelectric friction dampers (PFDs) that are employed as semi-active devices in combination with laminated rubber bearings for seismic protection of buildings. The first controller developed in this study is a direct adaptive fuzzy logic controller. It consists of an upper-level and a sub-level direct fuzzy controller. In the hierarchical control scheme, higher-level controller modifies universe of discourse of both premise and consequent variables of the sub-level controller using scaling factors in order to determine command voltage of the damper according to current level of ground motion. The sub-level fuzzy controller employs isolation displacement and velocity as its premise variables and command voltage as its consequent variable. The second controller is based on the simple adaptive control (SAC) method, which is a type of direct adaptive control approach. The objective of the SAC method is to make the plant, the controlled system, track the behavior of the structure with the optimum performance. By using SAC strategy, any change in the characteristics of the structure or uncertainties in the modeling of the structure and in the external excitation would be considered because it continuously monitors its own performance to modify its parameters. Here, SAC methodology is employed to obtain the required force which results in the optimum performance of the structure. Then, the command voltage of the PFD is determined to generate the desired force. For comparison purposes, an optimal controller is also developed and considered in the simulations together with maximum passive operation of the friction damper. Time-history analyses of a base-isolated five-story building are performed to evaluate the performance of the controllers. Results reveal that developed adaptive controllers can successfully improve seismic response of the base-isolated buildings against various types of earthquakes.

This paper is about mechanical vibration suppression in a three story building like structure. The experimental platform is a laboratory prototype made of aluminum alloy with bolted joints and an elctromagnetic shaker used as a disturbance source. This prototype can be used as a representation of a civil structure as well as an industrial machinery element. This structure is modeled and validated by the application of finite element methods and experimental modal analysis. The system response is controlled by a piezoelectric actuator, properly located on the structure, and with the synthesis of a feedback control law based on the well-known positive acceleration feedback control scheme. Some numerical simulations and experiments results are performed to illustrate the overall system performance in presence of several types of excitation.

Damage detection of spatially periodic structures is challenging, as such structures may have clustered natural frequencies, which makes it difficult to ascertain the damage-induced change of individual vibration frequency/mode. Moreover, the inevitable mistuning (i.e., substructure-to-substructure difference) in these structures further complicates the problem because it results in variations in natural frequencies/modes even under healthy condition. In this paper, taking advantage of the unique characteristics of periodic structures, we explore the possibility of using piezoelectric networking to temporarily induce or intensify the vibration localization in a mistuned periodic structure. The intensified vibration localization will cause drastic change in dynamic response patterns upon damage occurrence to highlight the damage effect. We integrate identical piezoelectric inductive circuits onto all substructures, and couple the circuits with identical capacitance elements, which retains the nominal periodicity of the system. Through analytical studies and parametric investigations, the circuitry inductance and coupling capacitance values that lead to intensified vibration localization are identified. Our analysis indicates that this proposed scheme can significantly amplify the response anomaly for periodic structures when damage occurs.

The present work has been initiated in the frame of the European research project DREAM. Within this highly interdisciplinary project we are focusing on the development and application of vibration damping solutions based on piezoelectric shunt circuits for future aeroelastic applications. The scientific community has put significant effort into the investigation of piezoelectric shunt damping in conjuction with typical engineering test structures such as beams and plates. However, investigations are mainly restricted to surface bonded piezoelectric elements. Commercially available actuators and sensors can be easily bonded to structures using standard epoxy resins. Yet, the structural integration into composite laminates is cumbersome, due to the implications in terms of overall structural integrity and functionality, and due to the problems in achieving a good electrical conductivity, intimate contact betwen electrode and piezoceramic material as well as a perfect isolation from the surrounding host structure. This contribution is concerned with technological aspects related to the integration of piezoceramic actuators into highly loaded CFRP structures. In particular, we present results of a comparative study aiming at the characterization of less invasive electrodes to establish electrical contact between the piezoceramic material and possible shunt circuits. Another drawback of commercial actuators are their limited strain allowables ranging from 0.1% to 0.3% which is not sufficient for high performance lighweight structures. The second part of this contribution is therefore dedicated to the description of a novel prestressing procedure which is used to fabricate actuators that command 170% higher strain allowables than non-prestressed actuators. Mechanical testing of these prestressed actuators are very encouraging, showing high strain allowables, perfect electrical isolation from the host structure, excellent electric contacting of the piezoelectric material and reliable functionality even when applied to curved structures.

The feasibility of piezoelectric-based Adaptive-Impedance Composites (AIC) as a method of protecting aircraft equipment from lightning strike events and the resultant High-Intensity Radiated Fields (HIRF) was investigated. Classical Laminated Plate Theory (CLPT) and sheet vibration theory were applied to analytically derive the performance of the AIC. Multiple prototypes were built for high voltage testing which revealed closed- to open-circuit switching as fast as 77 μs. It was observed that slight geometric variations of the AIC strongly influenced the activation voltage. The voltage necessary to trigger the 85mm long, 3rd generation AIC's impedance could be set between 10 and 60 V. The test data and the analytical predictions were compared with the lightning strike data gathered by ONERA. The comparison indicated the AIC switching speed was over 30 times faster than the necessary minimum to shield typical avionics and flight control mechanisms from lightning-strike induced electrical eddy currents and HIRF.

Acoustic MetaMaterials (AMM) have been considered as effective means for controlling the propagation of acoustical wave energy through these materials. However, most of the currently exerted efforts are focused on studying passive metamaterials with fixed material properties. In this paper, the emphasis is placed on the development of a new class of one-dimensional acoustic metamaterials with effective bulk moduli that are programmed to vary according to any prescribed pattern along the volume of the metamaterial. Acoustic cavities coupled with either actively controlled Helmholtz or flush-mounted resonators are introduced to develop two possible configurations for obtaining Active AMM (AAMM) with programmable bulk modulus capabilities. The resonators are provided with piezoelectric boundaries to enable the control the overall bulk modulus of the acoustic cavity through direct acoustic pressure feedback. Theoretical analyses of these two configurations of the AAMM are presented using the lumped-parameter modeling approach. Numerical examples are presented to demonstrate the performance characteristics of the proposed AAMM configurations and their potential for generating prescribed spatial and spectral patterns of bulk modulus variation.

This paper is a comprehensive study of series tuned mass damper (TMDs) for vibration mitigation in passive, active, and semi-active manners. Recently, the authors proposed a novel configuration of TMD with multiple auxiliary absorbers connected to the primary structure in series, and proved that passive series TMDs are more effective and robust than other types of TMDs. Here we further extend the study to active and semi-active controls using LQG and clipped algorithms. The advantages of series TMDs are further highlighted in comparison with the classic TMD. Numerical simulations based on the parameters of Taipei 101 tower are carried out. It is founded that in the passive implementation we can reduce the total mass requirement by 40%, and decrease the damping coefficient to 1/30. We also found that in the active and semi-active manners, the requirement of actuation force is reduced to only 1/4 while achieving the same or better performance.

In the present work, numerical simulations are carried out to investigate a passive amplified structural damping system, the scissor-jack damper, for controlling vibrations in a seismically-excited truss tower. To reduce computational effort, a bi-model method is employed to represent the 3D truss tower as a dynamically equivalent 2D lumped-mass model. For the scissor-jack damper, a new formulation for the amplification factor equation of the device is presented, and then validated using CAD. The new formulation accounts for the large deformations experienced by the device as a result of the large displacements present in the flexible tower during seismic loading. In order to capture the interaction between the structure and control device, the displacement-dependent amplification factors of the scissor-jack devices, and velocity-dependent forces of the dampers, are calculated at each time step. The resulting amplified damper force is then applied back to the structure to determine its response at the next time step. The response of the tower with scissor-jack damper systems is simulated for the El Centro and Northridge earthquakes, and time-histories of the displacement and absolute acceleration at each level of the tower are obtained. These results indicate that the system is effective in reducing overall response of the tower without exceeding practical limits on the stroke capacity of the scissor-jack dampers.

In this paper we report a scheme of low-cost, small-size differential electrical converter to change analog trigger signals into digital trigger signals. This converter successfully resolves the incompatibility between the digital trigger mode of NI (National Instruments) data acquisition card PCI 5105 in Measurement Studio development environment for a demodulator and the requirement from instability of spectra of fiber Bragg grating (FBG) sensors. The instability is caused by intrinsic drifts of FFP-TF inside this high speed demodulator. The obtained results of frequency response about the converter have clearly demonstrated that this method is effective when the frequency of trigger signal is less than 3,000 Hz. This converter can satisfy the current requirements of demodulator based on FFP-TF, since mostly actual working scanning frequency of FFP-TF is less than 1,000 Hz. This method may be recommended to resolve similar problems for other NI customers who have developed their data acquisition system based on Measurement Studio.

In the synchronized switching damping (SSD) techniques, the voltage on the piezoelectric element is switched synchronously with the vibration to be controlled using an inductive shunt circuit (SSDI). The inherent capacitance and the inductance in the shunt circuit comprise an electrically resonant circuit. In this study a negative capacitance is used in the shunt circuit instead of an inductance in the traditional SSD technique. The voltage on the piezoelectric element can be effectively inverted though the equivalent circuit is capacitive and no resonance occurs. In order to investigate the principle of the new SSD method based on a negative capacitance (SSDNC), the variation of the voltage on the piezoelectric element and the current in the circuit is analyzed. Furthermore, the damping effect using the SSDNC is deduced, and the energy balance and stability of the new system are investigated analytically. The method is applied to the single mode control and two-mode control of a composite beam, and its control performance was confirmed by the experimental results. For the first mode in single mode control, the SSDNC is much more effective than SSDI. In other cases, the SSDNC is also more effective than the SSDI, although not significantly.

This work deals with the problem of the active unbalance control in an asymmetrical rotor-bearing system with two disks supported by an active suspension based on two lateral linear actuators. For the analysis and control synthesis a mathematical model is developed using Finite Element Methods (FEM). A linear quadratic regulator (LQR) is applied in order to minimize the displacements of the two disks by means of the application of an active bearing with control forces provided by an arrangement of two linear actuators. The control scheme is designed to attenuate the overall system response in the natural frequencies (resonances), taking into account the unbalance response associated to both disks and shaft and, hence, controlling the system performance during the first modes. To do this, a Luenberger type observer is used to estimate those not measurable states from the displacements in only one shaft point and, therefore, making possible the synthesis of an optimal LQR control based on the estimated state feedback. The control forces obtained from LQR control are introduced to the mathematical model of actuators and taking into account their dynamics, we get the voltage inputs necessary to provide the unbalance compensation forces. The proposed control scheme is proved by numerical results and then, validated experimentally on a test rig which was designed and constructed. Numerical and experimental results show significant reductions in the unbalance response of the overall system.

Sensor elements employing fine filaments are often vulnerable to particulate fouling when used in certain operational field conditions. Depending on the size, attraction level, thermal and electrical conduction and charge accumulation properties of the particles, erroneous readings can be easily generated in such "dirty" environments. This paper describes the design, development and testing of an ultrasonic system which dynamically rejects highly tenacious electrostatically charged particles of a wide variety of sizes and even water. The paper starts with a brief introduction to the field of acoustic vector sensing, outlining its outstanding characteristics and history. Operational challenges including a statistical analysis of typical Middle-Eastern wind-blown desert sand and charge density are laid out. Several representative subscale hot-wire filaments were fouled with calibrated dust representing desert sand. The fouled elements were then exposed to airflows of 13 ft/s (4m/s) and showed highly erratic, shifted conduction levels with respect to baseline (clean) levels. An ultrasonic cleaning system was designed specifically resonate the filament and cantilever so as to mechanically reject foulants. When operated at resonance, the ultrasonic cleaning system showed 98.6% particulate rejection levels and associated restoration of uncorrupted filament resistance levels to within 2% of baseline resistance measurements. The study concludes with an assessment of such cleaning techniques in various environments.

Self-powered active vibration control is a system that produces a control force using energy generated from vibration and carries out the control without power sources. The authors propose to apply this control system to smart structures using a piezoelectric actuator. Assuming the structure is a simply supported beam, a linear state space equation is derived and an equation to estimate the power balance is presented. The results of the numerical simulations and experiments show the active control system suppresses vibration better than a passive control system where the amount of the power generated exceeds the amount consumed.

An energy harvesting system is presented that converts energy out of flowing media, like water or wind. Without the need for any rotating part the harvester converts the energy out of the bending of a piezoelectric cantilever. A bluff body, which the cantilever is attached to, causes vortices and therefore pressure differences above and beneath the cantilever. Thus the cantilever oscillates and generates an alternating voltage. A first macroscopic model proofed this working concept for air and water. Measurements showed good coupling between flow velocity and power generation. Furthermore a self synchronization of different cantilevers could be observed in water. A second model of the harvester was build with improved distribution of piezoelectric layers. To store and distribute the generated energy of the harvester, it was combined with a low power circuit that was developed, too. Therefore, a complete autonomous system that is able to supply a load and the necessary electric circuit with power is presented.

SMA honeycombs have been recently developed by several Authors [1, 2] as innovative cellular structures with selfhealing capability following mechanical indentation, unusual deformation (negative Poisson's ratio [3]), and possible enhanced damping capacity due to the natural vibration dissipation characteristics of SMAs under pseudoelastic and superelastic regime. In this work we describe the nonlinear damping effects of novel shape memory alloy honeycomb assemblies subjected to combine mechanical sinusoidal and thermal loading. The SMA honeycomb structures made with Ni₄₈Ti₄₆Cu₆ are designed with single and two-phase polymeric components (epoxy), to enhance the damping characteristics of the base SMA for broadband frequency vibration.

This study reports the design, fabrication, and implementation of a horizontal-axis, small-scale modular wind turbine termed as "small-scale wind energy portable turbine (SWEPT)". Portability, efficient operation at low wind speeds, and cost-effectiveness were the primary goals of SWEPT. The fabrication and component design for SWEPT are provided along with the modifications that can provide improvement in performance. A comparative analysis is presented with the prototype reported in literature. The results show that current version of SWEPT leads to 150% increase in output power. It was found that SWEPT can generate 160 mW power at rated wind speed of 7 mph and 500mW power at wind speeds above 10 mph with a cut-in wind speed of 3.8 mph. Furthermore, the prototype was subjected to field testing in which the average output was measured to be 40 mW despite the average wind distribution being centered around 3 mph.

This paper outlines an investigation using shape memory alloy (SMA) filaments to drive a flight control system with precision control in a real flight environment. An antagonistic SMA actuator was developed with an integrated demodulator circuit from a JR NES 911 subscale UAV actuator. The SMA actuator was installed in the fuselage of a 2m uninhabited aerial vehicle (UAV) and used to control the rudder through slips and coordinated turns. Rudimentary design envelope modeling was performed to verify peak-to-peak throw levels and airload resistance capabilities. The actuator was capable of 20 degrees of positive and negative deflection and was capable of 7.5 in-oz (5.29N-cm) of torque at a bandwidth of 2.8Hz.

Dynamic loadings in automotive structures may lead to reduction of driving comfort and even to failure of the components. Damping treatments are applied in order to attenuate the vibrations and improve the long term fatigue behavior of the structures. This experimental study is targeting applications in floor panels that are mounted to the loadcarrying primary structure of the vehicle. The objective is to reach outstanding damping performance considering the stringent weight and cost requirement in the automotive industry. An experimental setup has been developed and validated for the determination of the damping properties of structural specimens also considering interface damping effects. This contribution is structured in three main parts: test rig design, experimental results and discussion. Reliable and easy-to-use devices for the characterization of the damping properties of specimens between 200×40 mm² and 400×400 mm² are not available "on the shelf". In this context, we present a flexible experimental set-up which has been realized to (1) support the development of novel damping solutions for multi-functional composite structures; (2) characterize the loss-factor of the different damping concepts, including boundary effects. A variety of novel passive and active damping treatments have been investigated including viscoelastic, coulomb, magnetorheological (MR), particle, magnetic and eddy current damping. The particle, interface as well as active damping systems show promising performance in comparison to the classical viscoelastic treatments.

Energy can be reclaimed and stored for later use to recharge a battery or power a device through a process called energy harvesting. Piezoelectric is being widely investigated for use in harvesting surrounding energy sources such as sun, wind, tides, indoor lighting, body movement or machine vibration, etc. This paper introduces a wind energy harvesting device using a Piezo-Composite Generating Element (PCGE). The PCGE is composed of layers of carbon/epoxy, PZT ceramic, and glass/epoxy cured at an elevated temperature. In the prototype, The PCGE performs as a secondary beam element. One end of the PCGE is attached on the frame of the device. The fan blade rotates in the direction of the wind and hits the PCGE's tip. When the PCGE is excited, the effects of the beam deformation allow it to generate electric power. In wind tunnel experiments, the PCGE is excited to vibrate at its first natural frequency and generates the power up to 8.5 mW. The prototype can harvest energy in urban regions with minor wind movement.

Due to the availability of small sensors, Micro-Aerial Vehicles (MAVs) can be used for detection missions of biological, chemical and nuclear agents. Traditionally these devices used fixed or rotary wings, actuated with electric DC motortransmission, a system which brings the disadvantage of a heavier platform. The overall objective of the BATMAV project is to develop a biologically inspired bat-like MAV with flexible and foldable wings for flapping flight. This paper presents a flight platform that features bat-inspired wings which are able to actively fold their elbow joints. A previous analysis of the flight physics for small birds, bats and large insects, revealed that the mammalian flight anatomy represents a suitable flight platform that can be actuated efficiently using Shape Memory Alloy (SMA) artificial-muscles. A previous study of the flight styles in bats based on the data collected by Norberg [1] helped to identify the required joint angles as relevant degrees of freedom for wing actuation. Using the engineering theory of robotic manipulators, engineering kinematic models of wings with 2 and 3-DOFs were designed to mimic the wing trajectories of the natural flier Plecotus auritus. Solid models of the bat-like skeleton were designed based on the linear and angular dimensions resulted from the kinematic models. This structure of the flight platform was fabricated using rapid prototyping technologies and assembled to form a desktop prototype with 2-DOFs wings. Preliminary flapping test showed suitable trajectories for wrist and wingtip that mimic the flapping cycle of the natural flyer.

For the sake of avoiding the impact of surrounding buildings on the radar, radar tower is usually high, generally up to 100 meters. As the radar performance reasons, the required fundamental frequency of radar tower should not be less than 1Hz. For such a tall building, how to control the frequency of radar tower is an issue worth studying. Through a lot of calculations and analyses, paper reaches a number of laws to increase frequency: 1) Lowering center of gravity of the structure; 2) Setting leaning bracing; 3) Raising the thickness or number of shear walls. In the above structural frequencies adjustment methods, setting leaning bracing and reducing the top mass of the structure are the most obvious effects of all. At the same time, paper also discusses on the seismic response of radar tower. Analyses used for earthquake are response spectrum method, time history analysis method and random vibration analysis. Three methods of calculation results show: radar tower performance meets China's seismic code to regulate specifications of the story drift limits.