This PDF file contains the front matter associated with SPIE Proceedings Volume 8688, including the Title Page, Copyright Information, Table of Contents, and the Conference Committee listing.

Hydraulic pressure ripple energy harvesters generate low-power electricity from off-resonance dynamic pressure excitation of piezoelectric elements. Improvements were made to hydraulic pressure ripple energy harvester prototype performance. Hydraulic systems inherently have a high energy intensity associated with the mean pressure and flow. Accompanying the mean pressure is dynamic pressure ripple, which is caused by the action of pumps and actuators. Pressure ripple is generally a deterministic source with a periodic time-domain behavior conducive to energy harvesting. An energy harvester prototype was designed for generating low-power electricity from pressure ripples. These devices generate low-power electricity from off-resonance dynamic pressure excitation. The power produced per volume of device was increased through decreasing the device size and adding an inductor to the system circuit. The prototype device utilizes a piezoelectric stack with high overall capacitance allowing for inductance matching without using a switching circuit. Initial testing with addition of an inductor produced over 2.1 mW, an increase of 78% as compared to the device without the inductor. Two power output model simulations of a resistive-inductive circuit are analyzed: (1) ideal circuit case and (2) non-ideal circuit case with inductor internal resistance included.

Energy harvesters of PVDF were used to power a wireless sensor system. Simple technologies are sufficient for the fabrication of these harvesting modules. A critical process step is the polarization of the piezoelectric material. Main piezoelectric parameters depend strongly on the polarization material. Particularly, the remanent polarization of PVDF is influenced by the electric field strength and the polarization temperature. Dielectric breakdowns of the film at higher temperatures prevent a sufficient polarization. At least, all modules were polarized at a field strength of 100 – 120 MV/m and a temperature of 90°C. Modules with dimensions of 165mm × 95mm × 1.5mm were used to power a commercial available “development kit for Energy Harvesting Wireless systems” (EnOcean ‘EDK 300’). The modules possess of 20 layers of PVDF. Each module was connected via a standard four diode full rectifier bridge with the development kit EDK 300. Positioned underneath a parquet floor (thickness=10mm), the modules converted mechanical energy of footsteps into electricity. Goal of these investigations were to find out configurations suited to generate a sufficient energy level to supply the operation of the EDK 300. Two capacitors in the development kit are used to start the operation of the kit (C₁=470μF) and to store converted energy (C₂=0.25F). Already a few steps onto one module were sufficient to charge C₁ and to start the operation of the EDK 300. Following steps (>100) produced energy which was stored in C₂. Increasing numbers of mechanical loaded modules lead to a rise of energy stored in C₂.

Recent interest in bistable devices for vibration energy harvesting has given evidence of their beneficial performance in realistic stochastic or low frequency excitation environments since the snap through effect (high displacement switching from one stable state to another) is a non-resonant dynamic. It has yet to be rigorously determined how adding additional degrees-of-freedom may influence bistable energy harvesting response since the nonlinearities do not allow for a direct analogy from multi-body linear examples. We analytically and experimentally assess the potential for improving energy harvesting dynamics by adding a conventional linear oscillator to a bistable energy harvester. The traditional coupling parameters of mass ratio and tuning ratio are evaluated as means to tune the harvester's response. Advantageous design regimes are classified and explanations for the rich dynamics are provided. Experiments confirm the benefit of appending a linear oscillator to the bistable system as a simple means by which to enhance harvesting performance.

This article reports the modeling of the parallel connection of multiple piezoelectric oscillators with respective electrical rectification. Such an array structure offers advantages of boosting power output and exhibiting broadband energy harvesting. The theoretical estimates are proposed for different choices of electronic interfaces, including the standard and parallel-/series-SSHI (synchronized switch harvesting on inductor) circuits. It is shown that the electrical response is governed by a set of simultaneous nonlinear equations with constraints indicating blocking by rectifiers. Finally, the validation is carried out by circuit simulations and shows good agreement.

This paper presents experimental energy harvesting efficiency analysis of a piezoelectric device driven to limit cycle oscillations by an aeroelastic flutter instability. Wind tunnel testing of the flutter energy harvester was used to measure the power extracted through a matched resistive load as well as the variation in the device swept area over a range of wind speeds. The efficiency of this energy harvester was shown to be maximized at a wind speed of about 2.4 m/s, which corresponds to a limit cycle oscillation (LCO) frequency that matches the first natural frequency of the piezoelectric structure. At this wind speed, the overall system efficiency was 2.6%, which exceeds the peak efficiency of other comparably sized oscillator-based wind energy harvesters using either piezoelectric or electromagnetic transduction. Active synchronized switching techniques are proposed as a method to further increase the overall efficiency of this device by both boosting the electrical output and also reducing the swept area by introducing additional electrical energy dissipation. Real-time peak detection and switch control is the major technical challenge to implementing such active power electronics schemes in a practical system where the wind speed and the corresponding LCO frequency are not generally known or constant. A promising microcontroller (MCU) based peak detector is implemented and tested over a range of operating wind speeds.

This paper focuses on the influence of the topology of a network of piezoelectric harvesters using the SSHI (Synchronized Switch Harvesting on Inductor) technology. Generally, an energy harvester is used as a localized and standalone system. In the case of large structure and for large harvested energies, it is usually not easy to increase the size of the piezoelectric patches. In order to harvest energy in the regions of maximum strain of the structure, a networked piezoelectric harvester including many separated piezoelectric patches must be set up with only one output. The main concern is how to connect the piezoelectric elements together and how to implement accurately the SSHI strategy for maximizing the total output power. This paper presents 5 different circuit topologies with or without SSHI enhancement. This work is based upon simulations of a structure with embedded piezoelectric harvesters, made in the Matlab/Simulink environment and using the Simscape library for defining and simulating the electric network. The simulations are done exclusively in pulse mode. For each circuit topology, the total output energy is computed and the optimal harvesting capacitance is defined. The results show the feasibility of grouping various harvesters within a network connected onto a common harvesting capacitance without affecting the extracted energy. The interest of SSHI for networked configuration is confirmed as well as the need for multiple switching units. The effect of the parasitic capacitances due to the bonding of the piezoelectric patches on a metallic structure is also investigated. This capacitance corresponds to the isolation layer between the structure and the bottom electrode of the piezoelectric patches. Results show that an optimal bonding layer thickness can be found that does not affect significantly the coupling coefficient of the piezoelectric patches and which induces parasitic capacitances that do not affect the network functionality.

In the past decade, there has been a dramatic rise of research in the field of energy harvesting from ambient environment, such as mechanical vibrations and dissipated heat. As a key element connecting the harvester and energy storage element in energy harvesting systems, power electronic interface circuitry has drawn significant interests. Abundant research on the power electronic circuits with functions of voltage regulation, optimal power extraction and damping control for energy harvesting systems has been conducted and reported, together with control algorithms and implementations to achieve these functions. This paper reviews the reported concepts for power electronic interface circuits in kinetic energy harvesting systems, such as electromagnetic and piezoelectric harvesters. Power electronic interface circuit concepts included were grouped in the view of energy scale, power flow direction, functionality and complexity. An overview of the power electronic circuit topologies with various functions available for constructing the power electronic interface circuits and problems yet to be solved for kinetic energy harvesting systems is provided by this paper.

Many closed-loop control methods for increasing the power output from piezoelectric energy harvesters have been investigated over the past decade. Initial work started with the application of Maximum Power Point Tracking techniques (MPPT) developed for solar power. More recent schemes have focused on taking advantage of the capacitive nature of piezoelectric harvesters to manipulate the transfer of energy from the piezoelectric to the storage element. There have been a couple of main techniques investigated in the literature: Synchronous Charge Extraction (SCE), Synchronized Switching and Discharging to a Capacitor through an Inductor (SSDCI), Synchronized Switch Harvesting on an Inductor (SSHI), and Piezoelectric Pre-Biasing (PPB). While significant increases in harvested power are seen both theoretically and experimentally using powerful external control systems, the applicability of these methods depends highly on the performance and efficiency of the system which implements the synchronized switching. Many piezoelectric energy harvesting systems are used to power devices controlled by a microcontroller (MCU), making them readily available for switching control methods. This work focuses on the practical questions which dictate the applicability of synchronized switching techniques using MCU-based switching control.

Vibration energy harvesting using piezoelectric material has received great research interest in the recent years. To enhance the performance of piezoelectric energy harvesters, one important concern is to increase their operating bandwidth. Various techniques have been proposed for broadband energy harvesting, such as the resonance tuning approach, the frequency up-conversion technique, the multi-modal harvesting and the nonlinear technique. Usually, a nonlinear piezoelectric energy harvester can be easily developed by introducing a magnetic field. Either mono-stable or bi-stable response can be achieved using different magnetic configurations. However, most of the research work for nonlinear piezoelectric energy harvesting has focused on the SDOF cantilever beam. A recently reported linear 2-DOF harvester can achieve two close resonant frequencies with significant power outputs. However, for this linear configuration, although a broader bandwidth can be achieved, there exists a deep valley in-between the two response peaks. The presence of the valley will greatly deteriorate the performance of the energy harvester. To overcome this limitation, a nonlinear 2-DOF piezoelectric energy harvester is proposed in this article. This nonlinear harvester is developed from its linear counterpart by incorporating a magnetic field using a pair of magnets. Experimental parametric study is carried out to investigate the behavior of such harvester. With different configurations, both mono-stable and bi-stable behaviors are observed and studied. An optimal configuration of the nonlinear harvester is thus obtained, which can achieve significantly wider bandwidth than the linear 2-DOF harvester and at the same time overcome its limitation.

The mathematical models used to predict power produced from piezoelectric energy harvesters have seen continued refinement in the last decade. Despite this, we have been unable to give general power limits for the technology. This is due in large part to the fact that power output is heavily dependent on acceleration magnitude and frequency, as well as the internal damping of the harvester itself. The existing power models all assume some magnitude of excitation acceleration, that scales the harvested power, usually by the square of its magnitude. We know that this excitation can only be taken to the point at which the harvester is damaged, and no longer produces power. The power produced at this excitation acceleration magnitude thus represents the power-harvesting limit of the technology. In this paper, we seek to relate acceleration, displacement, stress, and harvested power in a way that provides a general limit for the technology. We will show that, based on the ultimate strength of the material, there is an upper limit on the excitation acceleration. Then using this expression for allowable excitation acceleration, we are able to develop an expression for the upper limit of harvestable power. The resulting expression for power capabilities is independent of acceleration magnitude and harvester mechanical damping. It does, however, depend on the acceleration frequency and beam design. Using this expression, we then explore the power harvesting limits of the technology across a range of input frequencies and beam sizes.

In this paper, a micro piezoelectric energy harvester based on stainless steel substrate with dual oscillators is presented. The first mirco-dual oscillator design (Figure 6(a)) showed intense stress concentration at the corner of beam, which induced device failure on 0.5g. Therefore, an improved design with better durability by broadening the root of the beam is proposed, fabricated and verified. As we wished to keep the characteristic of low resonance frequencies, the improved device can scavenge energy at a resonance frequency of approximately 40.2Hz. In order to obtain a better output, the device was in d₃₁ mode, and fabricated on stainless-steel substrate. The stainless steel substrate provides superior robustness allowing the micro device to withstand harsher environments. A series of simulation and test is presented, and the performance of the device is demonstrated. The maximum output power of 0.25 g was 2.4μW with the resonance frequency of the device 40.2Hz.

An important limitation in the classical energy harvesters based on cantilever beam structure is its monodirectional sensibility. The external excitation must generate an orthogonal acceleration from the beam plane to induced flexural deformation. If the direction of the excitation deviates from this privileged direction, the harvester output power is drastically reduced. This point is obviously very restrictive in the case of an arbitrary excitation direction induced for example by human body movements or vehicles vibrations. In order to overcome this issue of the conventional resonant cantilever configuration with seismic mass, a multidirectional harvester is introduced here by the authors. The multidirectional ability relies on the exploitation of 3 degenerate structural vibration modes where each of them is induced by the corresponding component of the acceleration vector. This specific structure has been already used for 3 axis accelerometers but the approach is here totally revisited because the final functional goal is different. This paper presents the principle and the design considerations of such multidirectional piezoelectric energy harvester. A finite element model has been used for the harvester optimisation. It has been shown that the seismic mass is a relevant parameter for the modes tuning because the resonant frequency of the 1st exploited flexural mode directly depends on the mass whereas the resonance frequency of the 2nd flexural mode depends on its moment of inertia. A simplified centimetric prototype limited to a two orthogonal direction sensibility has permitted to valid the theoretical approach.

Recently, the idea to exploit nonlinearity to achieve broadband energy harvesting has been introduced. Bi-stable systems have been used to realise broadband energy harvesting devices. Amongst these, harvesters constructed with bi-stable composites show great potential due to their rich dynamic behaviour. This paper studies a novel cantilevered configuration for a piezoelectric bi-stable composite device for broadband energy harvesting. The cantilevered configuration allows to exploit high strains developed close to the clamped root, further enhancing the harvesting characteristic of bi-stable composites. Furthermore, the desired broadband dynamics are obtained for lower input amplitudes when compared to previous designs constituting a significant improvement for energy harvesting applications. Several cross-well dynamic behaviours are obtained over a relatively wide range of frequencies with the proposed design. In addition, the performance of the developed concept is investigated using a switching shunt harvesting circuit suitable for conversion of broadband oscillations resulting from the cross-well dynamics exhibited by bi-stable composite laminates showing very good results.

Recently, an adaptive structure concept based on fluidic flexible matrix composite (F²MC) cells has been investigated for its potential to provide multiple functionalities simultaneously. This structure consists of different F²MC cells that are connected through internal fluidic circuit, and due to the interaction between the fluid flow and cell wall deformation, the structure exhibits distinct system poles and zeros. By adjusting the F²MC cellular design parameters, the poles and zeros can be placed at appropriate positions so that the cellular structure can perform dynamic functions such as vibration absorption and dynamic actuation. In order to fully explore the potential of the F²MC based cellular structure, this research develops a synthesis procedure for a triple cellular structure based on a set of prescribed poles and zeros. This procedure is essentially a hybrid numerical method combining the Jacobi inverse eigenvalue problem solver and genetic algorithm with discrete variables. It is capable of selecting physically feasible design parameters for each F²MC cell in order to achieve the desired pole and zero positions accurately.

Vibro-Impcact harvesting devices are one concept to increase the bandwidth of resonant operated piezoelectric vibration generators. The fundamental setup is a piezoelectric bending element, where the deflection is limited by two stoppers. After starting the system in resonance operation the bandwidth increases towards higher frequencies as soon the deflection reach the stopper. If the stoppers are rigid, the frequency response gives constant amplitude for increasing frequencies, as long the system is treated as ideal one-DOF system with symmetric stoppers. In consequence, the bandwidth is theoretically unlimited large. However, such a system also has two major drawbacks, firstly the complicated startup mechanism and secondly the tendency to drop from the high constant branch in the frequency response on the much smaller linear branch if the system is disturbed. Nevertheless, the system has its application wherever the startup problem can be solved. Most modeling approaches utilize modal one-DOF models to describe the systems behavior and do not tread the higher harmonics of the beam. This work investigates the effects of the stoppers on the vibration shape of the piezoelectric beam, wherefore a finite element model is used. The used elements are one-dimensional two node elements based on the Timoshenko-beam theory. The finite element code is implemented in Matlab. The model is calculated utilizing time step integration for simulation, to reduce the computation time an auto-resonant calculation method is implemented. A control loop including positive feedback and saturation is used to create a self-excited system. Therefore, the system is always operated in resonance (on the backbone curve) and the frequency is a direct result of the computation. In this case tip velocity is used as feedback. This technique allows effective parametric studies. Investigated parameters include gap, excitation amplitude, tip mass as well as the stiffness of the stopper. The stress and strain distribution as well as the generated electrical power is analyzed with respect to the proper operation range.

The performance of standing and traveling wave thermoacoustic-piezoelectric energy harvesters are developed using an electrical circuit analogy approach. The harvesters convert thermal energy, such as solar or waste heat energy, directly into electrical energy without the need for any moving components. The input thermal energy generates a steep temperature gradient along a porous medium. At a critical threshold of the temperature gradient, self-sustained acoustic waves are developed inside an acoustic resonator. The associated pressure fluctuations impinge on a piezoelectric diaphragm, placed at the end of the resonator. The resulting interaction is accompanied by a direct conversion of the acoustic energy into electrical energy. The behavior of these two classes of harvesters is modeled using an electrical circuit analogy approach. The developed models are multi-field models which combine the descriptions of the acoustic resonator and the stack with the characteristics of the piezoelectric diaphragm. The onset of self-sustained oscillations of the harvesters are predicted using the root locus method and SPICE software (Simulation Program with Integrated Circuit Emphasis). The predictions are validated against published results. The developed electrical analogs and the associated analysis approach present invaluable tools for the design and the optimization of efficient thermoacoustic-piezoelectric energy harvesters.

In this paper, we demonstrate a non-contact magnetic/piezoelectric-based thermal energy harvester utilizing an optimized thermal-convection mechanism to enhance the heat transfer in the energy harvesting/converting process in order to increase the power output. The harvester consists of a CuBe spring, Gadolinium soft magnet, NdFeB hard magnets, frame, and piezoelectric PZT cantilever beams. According to the configuration, the energy harvesting/converting process under a temperature-difference is cyclic. Thus, the piezoelectric beams continuously oscillate and subsequently produce voltage responses due to the piezoelectric effect. The maximum voltage response of the harvester under a temperaturedifference of 25°C is 16.6 mV with a cycling frequency of 0.58 Hz. In addition, we compare the testing result of the harvester utilizing the new thermal-convection mechanism reported in this paper and using previous thermal-convection mechanism reported elsewhere. According to the comparison, the results show the harvester utilizing the new thermal-convection mechanism has a higher cycling frequency resulting in a higher power output than the previous mechanism.

In this paper a novel electromagnetic vibration type energy harvester which uses a diamagnetic levitation system is conceptualized, designed, fabricated, and tested. The harvester uses two diamagnetic plates made of pyrolytic graphite between which a cylindrical magnet levitates passively. Two archimedean spiral coils are placed in grooves which are engraved in the pyrolytic graphite plates, used to convert the mechanical energy into electrical energy efficiently. The geometric configurations of coils are selected based on the field distribution of the magnet to enhance the efficiency of the harvester. A thorough theoretical analysis is done to compare with the experiment results. At an input power of 103.45 μW and at a frequency of 2.7 Hz, the harvester generated a power of 0.744 μW at an efficiency of 0.72 %. Both theoretical and experimental results show that this new energy harvesting system is efficient and can capture low frequency broadband spectra.

The well known frequency-domain observability range space extraction (FORSE) algorithm provides a powerful multivariable system-identification tool with inherent flexibility, to create state-space models from frequency-response data (FRD). This paper presents a method of using FORSE to create “context models” of a lightly damped system, from which models of individual resonant modes can be extracted. Further, it shows how to combine the extracted models of many individual modes into one large state-space model. Using this method, the author has created very high-order state-space models that accurately match measured FRD over very broad bandwidths, i.e., resonant peaks spread across five orders-of-magnitude of frequency bandwidth.

Current autonomous underwater vehicle (AUV) designs have a serious deficiency in autonomy time due to its ballistic type of construction: a cylindrical body propelled by a rear engine. This type of design does not take complete advantage of the fluid that has to be displaced to move the vehicle forward, reducing the overall system efficiency and consequently its operation time. In order to overcome this limitation, research has focused on understanding of the propulsive mechanisms employed by the natural organisms. Jellyfish is one of the simplest and most relevant model systems as it exhibits one of the lowest cost-of-transport among all the known creatures. The learning and implementation of jellyfish-inspired vehicle design requires an evaluation of the current mathematical modeling approaches in order to adequately describe the dynamics of such a vehicle. This paper develops a time-varying rigid body model for the kinematics and dynamics of an AUV based on jellyfish rowing propulsion. A nonlinear sliding mode controller is also proposed to drive the system.

This paper presents an integrated methodology for optimizing vibroacoustic energy flow in interaction between an adaptive metacomposite made of periodically distributed shunted piezoelectric material glued onto passive plate and open acoustic domain. The computation of interacting Floquet-Bloch propagators is also used to optimize vibroacoustic behavior. The main purpose of this work is first to propose a numerical methodology to compute the fluid-structure multi-modal wave dispersions. In a second step, optimization of electric circuit is used to control the acoustic power flow. 3D standard computation is used to confirm the efficiency of the designed metacomposite in terms of acoustic emissivity and absorption.

The objective of this study is to improve the cost-effectiveness and production efficiency of wind farms using cooperative control. The key factors in determining the power production and the loading for a wind turbine are the nacelle yaw and blade pitch angles. However, the nacelle and blade angles may adjust the wake direction and intensity in a way that may adversely affect the performance of other wind turbines in the wind farm. Conventional wind-turbine control methods maximize the power production of a single turbine, but can lower the overall wind-farm power efficiency due to wake interference. This paper introduces a cooperative game concept to derive the power production of individual wind turbine so that the total wind-farm power efficiency is optimized. Based on a wake interaction model relating the yaw offset angles and the induction factors of wind turbines to the wind speeds experienced by the wind turbines, an optimization problem is formulated with the objective of maximizing the sum of the power production of a wind farm. A steepest descent algorithm is applied to find the optimal combination of yaw offset angles and the induction factors that increases the total wind farm power production. Numerical simulations show that the cooperative control strategy can increase the power productions in a wind farm.

This paper presents design of smart composite platforms for adaptive trust vector control (TVC) and adaptive laser telescope for satellite applications. To eliminate disturbances, the proposed adaptive TVC and telescope systems will be mounted on two analogous smart composite platform with simultaneous precision positioning (pointing) and vibration suppression (stabilizing), SPPVS, with micro-radian pointing resolution, and then mounted on a satellite in two different locations. The adaptive TVC system provides SPPVS with large tip-tilt to potentially eliminate the gimbals systems. The smart composite telescope will be mounted on a smart composite platform with SPPVS and then mounted on a satellite. The laser communication is intended for the Geosynchronous orbit. The high degree of directionality increases the security of the laser communication signal (as opposed to a diffused RF signal), but also requires sophisticated subsystems for transmission and acquisition. The shorter wavelength of the optical spectrum increases the data transmission rates, but laser systems require large amounts of power, which increases the mass and complexity of the supporting systems. In addition, the laser communication on the Geosynchronous orbit requires an accurate platform with SPPVS capabilities. Therefore, this work also addresses the design of an active composite platform to be used to simultaneously point and stabilize an intersatellite laser communication telescope with micro-radian pointing resolution. The telescope is a Cassegrain receiver that employs two mirrors, one convex (primary) and the other concave (secondary). The distance, as well as the horizontal and axial alignment of the mirrors, must be precisely maintained or else the optical properties of the system will be severely degraded. The alignment will also have to be maintained during thruster firings, which will require vibration suppression capabilities of the system as well. The innovative platform has been designed to have tip-tilt pointing and simultaneous multi-degree-of-freedom vibration isolation capability for pointing stabilization. Analytical approaches have been employed for determining the loads in the components as well as optimizing the design of the system. The different critical components such as telescope tube struts, flexure joints, and the secondary mirror mount have been designed and analyzed using finite element technique. The Simultaneous Precision Positioning and Vibration Suppression (SPPVS) smart composites platforms for the adaptive TVC and adaptive composite telescope are analogous (e.g., see work by Ghasemi-Nejhad and co-workers [1, 2]), where innovative concepts and control strategies are introduced, and experimental verifications of simultaneous thrust vector control and vibration isolation of satellites were performed. The smart composite platforms function as an active structural interface between the main thruster of a satellite and the satellite structure for the adaptive TVC application and as an active structural interface between the main smart composite telescope and the satellite structure for the adaptive laser communication application. 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. In addition, for example for the adaptive TVC, the experimental results show that the smart composite platform satisfactorily provided precision and fast smart platform control as well as the satisfactory thrust vector control capability. The vibration controller isolated 97% of the vibration energy due to the thruster firing.

This paper presents a novel approach for damping the vibration of a cantilever beam by bonding a fluidic flexible matrix composite (F²MC) tube to the beam and using the strain induced fluid pumping. The transverse beam vibration couples with the F²MC tube strain to generate flow into an external accumulator through an orifice that dissipates energy. The energy dissipation is especially significant at the resonances of the cantilever beam, where the beam vibrates with greatest amplitude and induces the most fluid flow from the F²MC tube. As a result, the resonant peaks can be greatly reduced due to the damping introduced by the flow through the orifice. An analytical model is developed based on Euler-Bernoulli beam theory and Lekhnitskii’s solution for anisotropic layered tubes. In order to maximize the vibration reduction, a parametric study of the F²MC tube is performed. The analysis results show that the resonant peaks can be provided with a damping ratio of up to 13.2% by tailoring the fiber angle of the F²MC tube, the bonding locations of the tube, and the orifice flow coefficient.

The classic tuned mass damper (TMD) is a passive vibration control device composed of an auxiliary mass connected to a vibrating object with a spring and an energy-dissipative element. When its parameters are optimized, it can reduce the vibration effectively. Recently, the authors proposed simultaneous vibration control and energy harvesting from tall buildings by replacing the energy-dissipative element of the TMD with electromagnetic transducers, which is called electricity-generating TMD. However, the electromagnetic transducers and the energy harvesting circuit, the modeling of which is an essentially a RL circuit, will introduce extra dynamics into the system, which has significant influence on the vibration mitigation performance. This paper investigates the influence, by optimizing the parameters. We found that the electricity-generating TMD can provide better vibration mitigation performance than the classic TMD and similar performance as the three-element TMD while harvesting the vibration energy at the same time. This paper utilizes the H2 criterions, which is to minimize the root-mean-square vibration under random excitation. The optimization method is presented in this paper, as well as the concise closed-form solution of the optimal parameters. A case study is also given to illustrate the effectiveness, robustness of the electricity-generating TMD and the sensitivity to the parameter changes.

A new global approach for improved vibration damping of smart structure, based on global energy redistribution by means of a network of piezoelectric elements is proposed. It is basically using semi-active Synchronized Switch Damping technique. SSD technique relies on a cumulative build-up of the voltage resulting from the continuous switching and it was shown that the performance is strongly related to this voltage. The increase of the piezoelectric voltage results in improvement of the damping performance. External voltage sources or improved switching sequences were previously designed to increase this voltage in the case of single piezoelectric element structure configurations. This paper deals with extended structure with many embedded piezoelectric elements. The proposed strategy consist of using an electric network made with non-linear component and switches in order to set up and control a low-loss energy transfer from source piezoelements extracting the vibration energy of the structure and oriented toward a given piezoelement in order to increase its operative energy for improving a given mode damping. This paper presents simulation of a clamped plate with four piezoelectric elements implemented in the Matlab/Simulink^TM environment and Simscape^TM library. The various simulation cases show the relationship between the damping performance on a given targeted mode and the established power flow. SSDD and SSDT are two proposed original networks. Performances are compared to the SSDI baseline. A damping increase of 18dB can be obtained even with a weakly coupled piezoelectric element in the multi-sine excitation case. This result proves the importance of new global non-linear multi-actuator strategies for improved vibration damping of extended smart structure.

Current sport stadia designs focus mainly on maximizing audience capacity and providing a clear view for all spectators. Hence, incorporation of one or more cantilevered tiers is typical in these designs. However, employing such cantilevered tiers, usually with relatively low damping and natural frequencies, can make grandstands more susceptible to excitation by human activities. This is caused by the coincidence between the activity frequencies (and their lowest three harmonics) and the structural natural frequencies hence raising the possibility of resonant vibration. This can be both a vibration serviceability and a safety issue. Past solutions to deal with observed or anticipated vibration serviceability problems have been mainly passive methods, such as tuned mass dampers (TMDs). These techniques have exhibited problems such as lack of performance and offtuning caused by human-structure interaction. To address this issue, research is currently underway to investigate the possible application of hybrid TMDs (HTMDs), which are a combination of active and passive control, to improve the vibration serviceability of such structures under human excitation. The work presented here shows a comparative experimental investigation of a passive TMD and a prototype HTMD applied on a slab strip structure. The most effective control algorithm to enhance the performance of the HTMD and also deal with the off-tuning problem is investigated. The laboratory structure used here is an in-situ cast simply-supported post-tensioned slab strip excited by forces from a range of human activities.

Commonly, vibration isolation systems reduce the transmissibility from seismic base vibrations to sensitive structures. To obtain a desirable low isolation frequency, vibration isolation systems are typically equipped with low stiffness interfaces between the involved structures. Strongly detrimental influences to the possible vibration reduction performance are caused by the effects of additional force disturbances that act directly on the isolated object. To protect sensitive structures from vibrations, isolation systems need to generate high flexibility against the vibrating ground. In the same time those systems need to generate high stiffness against the direct (force) disturbances as well. The technique described in this paper enables vibration reduction at such a sensitive object while seismic base and direct force disturbances are concurrently present. It is theoretically introduced and experimentally examined how the emerging conflict of simultaneous vibration isolation and energy reflection can be solved at a single isolation interface. This paper shows that even soft, adaptively altered isolation interfaces can reach these contrary goals. These interfaces are equipped with piezoelectric foil actuators to enable active control. The used active control mechanism and the very promising experimental results are highlighted in this paper.

Aiming at fundamentally improving the performance of MR dampers, including maximizing dynamic range (i.e., ratio of field-on to field-off damping force) while simultaneously minimizing field-off damping force, this study presents the principle of an inner bypass magnetorheological damper (IBMRD). The IBMRD is composed of a pair of twin tubes, i.e., the inner tube and outer concentric tube, a movable piston-shaft arrangement, and an annular MR fluid flow gap sandwiched between the concentric tubes. In the IBMRD, the inner tube serves simultaneously as the guide for the movable piston and the bobbin for the electromagnetic coil windings, and five active rings on the inner tube, annular MR fluid flow gap, and outer tube forms five closed magnetic circuits. The annular fluid flow gap is an inner bypass annular valve where the rheology of the MR fluids, and hence the damping force of the MR damper, is controlled. Based on the structural principle of the IBMRD, the IBMRD is configured and its finite element analysis (FEA) is implemented. After theoretically constructing the hydro-mechanical model for the IBMRD, its mathematical model is established using a Bingham-plastic nonlinear fluid model. The characteristics of the IBMRD are theoretically evaluated and compared to those of a conventional piston-bobbin MR damper with an identical active length and cylinder diameter. In order to validate the theoretical results predicted by the mathematical model, the prototype IBMRD is designed, fabricated, and tested. The servo-hydraulic testing machine (type: MTS 810) and rail-guided drop tower are used to provide sinusoidal displacement excitation and shock excitation to the IBMRD, respectively.

A variable stiffness and damping isolator (VSDI) is designed, developed and tested using a magnetorheological elastome (MRE). A double lap shear test is performed to characterize the MRE-based VSDI under the quasi-static shear loading. A phenomenological model that can capture the behavior of the VSDI is developed and related parameters are identified using experimental data.

The use of magnetorheological (MR) fluids in vehicles has been gaining popular recently due to its controllable nature, which gives automotive designers more dimensions of freedom in functional designs. However, not much attention has been paid to apply it to bicycles. This paper is aimed to study the feasibility of applying MR fluids in different dynamic parts of a bicycle such as the transmission and braking systems. MR continuous variable transmission (CVT) and power generator assisted in braking systems were designed and analyzed. Both prototypes were fabricated and tested to evaluate their performances. Experimental results showed that the proposed designs are promising to be used in bicycles.

Here, Digital image correlation (DIC) is demonstrated to be an accurate tool for the noncontact, non-destructive and rapid characterization of the converse piezoelectric effect in bulk and thin films. The out-of-plane (d₃₃) and in-plane (d₃₁) piezoelectric strain coupling coefficients of PZT- 5H wafers are measured simultaneously by imaging the wafer’s cross section under free mechanical boundary conditions. The large piezoresponse at switching domains and nonlinear behavior of PZT-5H are visualized in strain-electric field butterfly loops. The results show DIC as a simple advantageous technique to use for the characterization of piezoelectric materials under the influence of any field and physical constraints.

Electrohydraulic servo valves have been widely used in various automatic systems which need high precision of flow rate or pressure control to provide excellent static and dynamic control performance. The servo valves are generally classified into single-stage valve and two-stage valve. Direct drive servo valve (DDV) is a kind of single-stage valve in which the actuator is directly connected to the spool of the valve. In the conventional DDVs, the spool is generally actuated by electromagnetic actuator. Therefore, performance characteristics such as the accuracy and bandwidth of the DDVs are limited due to the inherent characteristics of the actuator. In this paper, a new type of the DDV operated by piezostack actuator is proposed and the goal of the proposed DDV is to achieve an accurate control of the flow rate at high frequency. The proposed DDV consists of a piezostack actuator, a lever mechanism to amplify displacement from the piezostack actuator and a spool part. A dynamic model of piezostack driven DDV system is derived by considering the flow force. After formulating the governing equation of the piezostack driven DDV system, a sliding mode control algorithm is designed to enforce the spool position to the desired position trajectories by activating the piezostack actuator. For the computer simulation, the specific geometric dimensions of the spool are chosen in order to achieve operation requirements: spool motion amplitude: over than 0.5mm; flow rate: over than 12liter/min; operating frequency: over than 200Hz. After confirming the maximum displacement of the spool and the flow rate of the valve at 200Hz, control performances are evaluated in time domain.

This paper presents power transmission performance of the ultrasound-based piezoelectric recharging system for implantable medical devices. The efficiency of the piezoelectric ultrasonic transcutaneous energy transfer system depends on frequency matching of the transmitter and receiver, electrical, mechanical and acoustical impedance characteristics, distance between the transducers, and misalignment. However, it was realized that the angular misalignment between transmitter and receiver was one of key factors to have effect on the power transmission efficiency. As such, misalignment effect of the piezoelectric ultrasound transmitter and receiver on the power transmission efficiency was investigated by theoretical analysis using finite-difference time-domain method. The pressure field variation in the near field was also estimated to examine the influence of the power transfer performance of the ultrasound-based charging system. Analytical results indicate that the transferred power is greatly reduced by voltage cancellation on the receiver from phase shift due to the misalignment. Furthermore, significant acoustic pressure variation in the near field makes the effect of misalignment on power transmission dependent on the receiver location.

Aircraft wings with smooth, hinge-less morphing ailerons exhibit increased chordwise aerodynamic efficiency over conventional hinged ailerons. Ideally, the wing would also use these morphing ailerons to smoothly vary its airfoil shape between spanwise stations to optimize the lift distribution and further increase aerodynamic efficiency. However, the mechanical complexity or added weight of achieving such a design has traditionally exceeded the potential aerodynamic gains. By expanding upon the previously developed cascading bimorph concept, this work uses embedded Macro-Fiber Composites and a flexure box mechanism, created using multi-material 3D printing, to achieve the Spanwise Morphing Trailing Edge (SMTE) concept. The morphing actuators are spaced spanwise along the wing with an elastomer spanning the gaps between them, which allows for optimization of the spanwise lift distribution while maintaining the continuity and efficiency of the morphing trailing edge. The concept is implemented in a representative section of a UAV wing with a 305 mm chord. A novel honeycomb skin is created from an elastomeric material using a 3D printer. The actuation capabilities of the concept are evaluated with and without spanning material on a test stand, free of aerodynamic loads. In addition, the actuation restrictions of the spanning elastomer, necessary in adapting the morphing concept from 2D to 3D, are characterized. Initial aerodynamic results from the 1’×1’ wind-tunnel also show the effects of aerodynamic loading on the actuation range of the SMTE concept for uniform morphing.

Former research on morphing droop-nose applications revealed great economical and social ecological advantages in terms of providing gapless surfaces for long areas of laminar flow. Furthermore a droop-nose for laminar flow applications provides a low noise exposing high-lift system at the leading-edge. Various kinematic concepts for the active deployment of such devices are already published but the major challenge is still an open issue: a skin material which meets the compromise of needed stiffness and flexibility. Moreover additional functions have to be added to keep up with standard systems. As a result of several national and European projects the DLR developed a gapless 3D smart droop-nose concept, which was successfully analyzed in a low speed wind tunnel test under relevant loads to prove the functionality and efficiency. The main structure of this concept is made of commercial available glass fiber reinforced plastics (GRFP). This paper presents elementary tests to characterize material lay-ups and their integrity by applying different loads under extreme thermal conditions using aged specimens. On the one hand the presented work is focused on the integrity of material-interfaces and on the other hand the efficiency and feasibility of embedded functions. It can be concluded that different preparations, different adhesives and used materials have their significant influence to the interface stability and mechanical property of the whole lay-up. Especially the laminate design can be optimized due to the e. g. mechanical exploitation of the added systems beyond their main function in order to reduce structural mass.

In this paper, the authors have developed a new application where MR fluid is being used as a sensor. An MR-fluid based torque wrench has been developed with a rotary MR fluid-based damper. The desired set torque ranges from 1 to 6 N.m. Having continuously controllable yield strength, the MR fluid-based torque wrench presents a great advantage over the regular available torque wrenches in the market. This design is capable of providing continuous set toque from the lower limit to the upper limit while regular torque wrenches provide discrete set torques only at some limited points. This feature will be especially important in high fidelity systems where tightening torque is very critical and the tolerances are low.

This study investigates a lumped-parameter human body model which includes lower leg in seated posture within a quarter-car model for blast injury assessment simulation. To simulate the shock acceleration of the vehicle, mine blast analysis was conducted on a generic land vehicle crew compartment (sand box) structure. For the purpose of simulating human body dynamics with non-linear parameters, a physical model of a lumped-parameter human body within a quarter car model was implemented using multi-body dynamic simulation software. For implementing the control scheme, a skyhook algorithm was made to work with the multi-body dynamic model by running a co-simulation with the control scheme software plug-in. The injury criteria and tolerance levels for the biomechanical effects are discussed for each of the identified vulnerable body regions, such as the relative head displacement and the neck bending moment. The desired objective of this analytical model development is to study the performance of adaptive semi-active magnetorheological damper that can be used for vehicle-occupant protection technology enhancements to the seat design in a mine-resistant military vehicle.

In this work, magnetorheological (MR) haptic master and slave robot for minimally invasive surgery (MIS) have been designed and tested. The proposed haptic master consists of four actuators; three MR brakes featuring gimbal structure for 3-DOF rotation motion(X, Y and Z axes) and one MR linear actuator for 1-DOF translational motion. The proposed slave robot which is connected with the haptic master has vertically multi- joints, and it consists of four DC servomotors; three for positioning endoscope and one for spinning motion. We added a fixed bar with a ball joint on the base of the slave for the endoscope position at the patient’s abdomen to maintain safety. A gimbal structure at the end of the slave robotic arm for the last joint rotates freely with respect to the pivot point of the fixed bar. This master-slave system runs as if a teleoperation system through TCP/IP connection, programmed by LabVIEW. In order to achieve the desired position trajectory, a proportional-integral-derivative (PID) controller is designed and implemented. It has been demonstrated that the effective tracking control performances for the desired motion are well achieved and presented in time domain. At last, an experiment in virtual environments is undertaken to investigate the effectiveness of the MR haptic master device for MIS system.

With fast response time and adjustable damping properties, magnetorheological (MR) dampers have shown their capabilities in reducing vibration of structures when subjected to impact loadings. In order to achieve the best performance of MR dampers for vibration control, a suitable semi-active control method is desired. Understanding and modeling of the dynamic behavior of MR dampers is crucial in development of control strategies. This paper presents both theoretical and experimental studies on modeling MR dampers under impact loadings. An improved polynomial model with simple form, which is easy to be solved inversely and suitable for implement in real time control, is proposed. A group of experimental tests are performed to evaluate the accuracy of the proposed model. The results show that the proposed model can well describe the relationship of damper velocity and its output force during buffering motion.

A challenge opposing a commercial use of actuators like brakes and clutches based on magnetorheological fluids (MRF) are durable no-load losses. A complete torque-free separation of these actuators is inherently not yet possible due to the permanent liquid intervention for the fluid engaging parts. Especially for applications with high rotational speeds up to some thousand RPM, this drawback of MRF actuators is not acceptable. In this paper, a novel approach will be presented that allows a controlled movement of the MRF from a torque-transmitting volume of the shear gap into an inactive volume of the shear gap, enabling a complete separation of the fluid engaging surfaces. This behavior is modeled for a novel clutch design by the use of the ferrohydrodynamics and therefore simulations are performed to investigate the transitions between engaged and idle mode. Measurements performed with a realized clutch show that the viscous induced drag torque can be reduced significantly.

This paper investigates the controllable magnetorheological (MR) mount for the marine diesel-generator (D/G) sets. Sometimes, significant vibrations over the allowable limit are observed on the D/G sets due to their huge excitation forces. Because the severe vibration can lead to structural damages to the D/G sets, it should be reduced to below the limit. Although passive mounts with rubber isolators are usually used, the vibration reduction performance is not always sufficient. In addition, expecting that the vibration levels required by customers will get more severe, semi-active vibration isolation system needs to be developed. To the aim, the valve (flow) mode type of MR mount has been designed. Especially, the annular-radial configuration was adopted to enhance the damping force within the restricted space. The geometry of the mount has been optimized to obtain the required damping force and the magnetic field analysis has been carried out using ANSYS APDL. To verify the performance of the developed MR mount, excitation test was conducted and the dynamic characteristics were identified. Since damping property of the MR fluid is changed by the applied magnetic field strength and excitation frequency, responses to changing applied currents and frequencies were obtained. From the results, damping performance of the MR mount was evaluated.

In this paper the novel design of Galfenol based vibration energy harvester is presented. The device uses Galfenol rod diameter 6.35 mm and length 50mm, polycrystalline, production grade, manufactured by FSZM process by ETREMA Product Inc. For experimental study of the harvester, the test rig was developed. It was found by experiment that for given frequency of external excitation there exist optimal values of bias and pre-stress which maximize generated voltage and harvested power. Under optimized operational conditions and external excitations with frequency 50Hz the designed transducer generates about 10 V and harvests about 0,45 W power. Within the running conditions, the Galfenol rod power density was estimated to 340mW/cm3. The obtained results show high practical potential of Galfenol based sensors for vibration-to-electrical energy conversion, structural health monitoring, etc.

Piezoelectric transducers are widely employed in vibration-based energy harvesting schemes. The efficiency of piezoelectric transducers fundamentally hinges upon the electro-mechanical coupling effect. While at the material level such coupling is decided by material property, at the device level it is possible to vary and improve the energy conversion capability between the electrical and mechanical regimes by a variety of means. In this research, a new approach of compensating the effective flexibility of piezoelectric transducers by using non-contact magnetic effect is explored. It is shown that properly configured and positioned magnet arrays can induce approximately linear attraction force that can improve the electro-mechanical coupling of the piezoelectric energy harvester. Analytical and experimental studies are carried out to demonstrate the enhancement.

An electromagnetic energy harvesting device, which converts a translational base motion into a rotational motion by using a rigid bar having a moving mass pivoted on a hinged point with a power spring, has been recently developed for use of civil engineering structures having low natural frequencies. The device utilizes the relative motion between moving permanent magnets and a fixed solenoid coil in order to harvest electrical power. In this study, the performance of the device is enhanced by introducing a rotational-type generator at a hinged point. In addition, a mechanical stopper, which makes use of an auxiliary energy harvesting part to further improve the efficiency, is incorporated into the device. The effectiveness of the proposed hybrid energy harvesting device based on electromagnetic mechanism is verified through a series of laboratory tests.

In recent years, wind energy harvesting systems using piezoelectric materials have been studied by a lot of researchers. However, energy harvesting methods using flexible thin piezoelectric wind energy harvesting method using high-polymer films was investigated experimentally. At first, the feasibility of the systems was shown in laboratory experiment by using various shapes, sizes, and boundary conditions of piezoelectric films subjected to the artificial wind airflow from consumer air blower. Then, a flag-type piezoelectric wind energy harvester was manufactured and the characteristic against natural winds was verified by outdoor experiments.

This work addresses the design of an integrated energy harvesting system under production viewpoints. The system is developed to harvest energy from rotational movements. Therefore, a piezoelectric bending element – mounted on the rotational part - is actuated by magnetic force introduced by hard magnets installed in the fixed frame. This work concentrates on a high integration, the energy harvesting circuit, including rectifier, power management and storage is integrated in the structure of the bending harvester. Further the soft magnetic tip mass is equipped with a coil for electromagnetic energy harvesting; the necessary electronic is also integrated in the structure. The paper addresses the special systems demands for large scale production. The production technology for a small series of prototypes is explained in detail. Performance tests of the device conclude this study.

The need to power small electronic components, such as wireless sensor networks, has prompted interest in energy harvesting technologies capable of generating electrical energy from ambient vibrations. There has been a particular focus on piezoelectric materials and devices due to the simplicity of the mechanical to electrical energy conversion and their high strain energy densities compared to electrostatic and electromagnetic equivalents. This paper describes research on an arrangement of piezoelectric elements attached to a bistable asymmetric laminate to understand the dynamic response of the structure and power generation characteristics. The inherent bistability of the underlying structure is exploited for energy harvesting since 'snap-through' from one stable configuration to another is used to strain the piezoelectric materials bonded to the laminate and generate piezoelectric energy. Using high speed digital image correlation, a variety of dynamic modes of oscillation are identified in the bistable harvester. The sensitivity of such vibrational modes to changes in frequency and amplitude are investigated. Electrical power outputs are measured for repeatable snap-through events and are correlated with the modes of oscillation. The typical power generated is approximately 25mW and compares well with the needs of typical wireless senor node applications.

This work presents experimental evidence of giant electromechanical and electrothermal transduction under ferroelectric/ferroelectric rhombohedral-orthorhombic phase transformation. Combinations of stress, electric field and temperature drive a phase transformation from rhombohedral to orthorhombic in [110]cut and poled ferroelectric single crystals. This phase transformation is accompanied by a large jump in polarization and strain. The results indicate that the ferroelectric crystals produce significant electrical energy density per cycle. Electrical transduction properties are measured from mechanical and thermal excitations applied to a ternary Pb(In_1/2Nb_1/2)O₃-Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PINPMN- PT) single crystal of composition just at the rhombohedral side of a morphotropic phase boundary. An overview of 32 mode phase transformation transduction characterization is discussed.

Preliminary experimental studies have shown that piezoelectric structures excited by turbulent flow can produce significant amounts of useful power. The research presented in this paper could benefit applications such as powering self-sustained sensor networks in small rivers or air flow environments where turbulent fluid flow is a primary source of ambient energy. A novel prototype called piezoelectric grass was designed to be a robust solution for harvesting energy in turbulent fluid flow environments. In this paper, the authors present an experimentally validated theoretical analysis of the piezoelectric grass harvester modeled as a single unimorph cantilever beam exposed to turbulent cross-flow. Lastly, a brief parameter optimization study will be presented. This study will demonstrate how the unimorph harvester design could be modified to achieve maximum power output in a given turbulent fluid flow condition.

This article theoretically and experimentally studies deterministic and stochastic piezoelectric energy harvesting using a multilayer stack configuration for civil infrastructure system applications that involve large compressive loads, such as vehicular and foot loads acting upon pavements. Modeling of vibrational energy harvesters has been mostly focused on deterministic forms of mechanical excitation as in the typical case of harmonic excitation. In this paper, we present analytical and numerical modeling of piezoelectric energy harvesting from harmonic and random vibrations of multilayer piezoelectric stacks under axial compressive loading. The analytical electromechanical solution is based on the power spectral density (PSD) of random excitation and the voltage – to – pressure input frequency response function (FRF) of the harvester. The first one of the two numerical solution methods employs the Fourier series representation of the vibrational excitation history to solve the resulting ordinary differential equation (ODE), while the second method uses an Euler-Maruyama scheme to directly solve the governing electromechanical stochastic differential equation (SDE). The electromechanical model is validated through several experiments for a multilayer PZT-5H stack under harmonic and random excitations. The analytical predictions and numerical simulations exhibit very good agreement with the experimental measurements for a range of resistive loads and input excitation levels.

Piezoelectric materials due to their high electromechanical coupling properties are good candidates for energy harvesting applications by transforming mechanical energy to electrical power. The piezoelectric coupling coefficient of each material is dependent on its operating mode and higher coupling coefficient means higher efficiency in energy harvesting. In most of the piezoelectric materials, the d₁₅ piezoelectric strain coefficient is the highest coefficient compared to the d₃₃ and d₃₁ coefficients. However complicated fabrication and evaluation of energy harvesting devices operating in the shear mode has slow down the research in this area. The shear piezoelectric effect can be induced during the steady state response of a thick cantilever composite beam due to the effect of shear force through the thickness. Here, a model based on the Timoshenko beam theory is developed to estimate the electric power output in a cantilever beam with a piezoelectric core subjected to the base excitation. The governing electromechanical equations as well as the output voltage and power frequency responses are derived for the piezoelectric sandwich beam. This model is applicable to different geometries and piezoelectric compositions in order to design an optimal shear energy harvester. At the end, the performance of this type of shear energy harvesters is compared to the typical cantilever bimorph energy harvesting beams with the same piezoelectric volume.

When the thickness of a plane structure is much smaller than its other characteristic lengths, a plate model is more realistic than a beam model. For a thin piezoelectric layer fully coated with metal electrodes on its top and bottom surfaces, the internal electric field is simple and easy to model. Therefore, it is advantageous to derive a piezoelectric composite plate model based on e-form constitutive equations. This approach is adopted to develop a mathematical model of Kirchhoff–Love type for a plate composed of a piezoelectric layer and a metal layer. To develop a method for calculating the loaded-circuit voltage between the top and bottom electrodes is one of the major tasks of this paper. The electric power generated from piezoelectric layer is found by modal analysis. Top and bottom electrodes of the piezoelectric layer are shorted for calculating resonant frequencies and mode shapes. Once these two electrodes are connected to an external circuit load, boundary conditions of top and bottom surfaces become nonhomogeneous. Superposition of short-circuit modes and one particular field constitutes the nonhomogeneous solution. A composite plate composed of a 0.3mm thick copper layer and a 0.2mm thick PZT-5A layer is investigated. The cantilever plate of 25mm in length is base-excited near the first resonant frequency. When connected to a circuit with certain load impedance, more than 80% efficiency of power generation can be achieved.

Multi-axial behavior of shape memory alloy (SMA) bars with circular cross section is studied by considering the effect of temperature gradient in the cross section as a result of latent heat generation and absorption during forward and reverse phase transformations. The local form of energy balance for SMAs by taking into account the heat flux effect is coupled to a closed-form solution of SMA bars subjected to multi-axial loading. Non-Mises definitions are employed for the effective stress and strain to enable the model to capture the coupling between tension and torsion. The resulting coupled thermo-mechanical equations are solved for SMA bars with circular cross sections. A number of experiments were conducted and the results were then successfully compared with the model. It is shown that the isothermal solution is valid only for specific combinations of ambient conditions and loading rates. The present approach is a beneficial platform in modeling and analysis of applications with high loading rates.

In general active vibration control intrinsically implies a fatigue damage reduction. Anyway, this assumption is not always verified. In these cases it is possible to deeper investigate the fatigue phenomena on smart flexible structures and their reduction from a control point of view. In this article, to identify the problem main parameters, a simplified interpretation of fatigue damage is given using the frequency analysis framework. Then, the active control logic is defined as an optimization problem with a quadratic functional taking into account the previously cited parameters. Finally, because of non-linearity of fatigue phenomenon, an adaptive approach is applied and a numerical/experimental validation is carried out.

In this paper the modelling and feedback control of non-contact ultrasonic squeeze film levitation bearings are presented. Simple models are employed to describe the levitation effect in order to make it accessible to a wide range of applications. The ultrasonic transducer acts as the dominating lag element in the ultrasonic levitation system. Thus the transient behavior of the ultrasonic transducer is investigated by averaging method in order to analyse the dynamic behavior. Finally the design of the overall feedback control system is presented. This is applied to a linear squeeze film levitation bearing. For the system at hand the theoretical model is validated experimentally. It turns out that the theoretical model is in good agreement with the obtained experimental results.

This paper presents a new methodology for eliminating the influence of the power fluctuations of the renewable power systems. The renewable energy, which is to be considered an uncertain and uncontrollable resource, can only provide irregular electrical power to the power grid. This irregularity creates fluctuations of the generated power from the renewable power systems. These fluctuations cause instability to the power system and influence the operation of conventional power plants. Overall, the power system is vulnerable to collapse if necessary actions are not taken to reduce the impact of these fluctuations. This methodology aims at reducing these fluctuations and makes the generated power capability for covering the power consumption. This requires a prediction tool for estimating the generated power in advance to provide the range and the time of occurrence of the fluctuations. Since most of the renewable energies are weather based, as a result a weather forecast technique will be used for predicting the generated power. The reduction of the fluctuation also requires stabilizing facilities to maintain the output power at a desired level. In this study, a wind farm and a photovoltaic array as renewable power systems and a pumped-storage and batteries as stabilizing facilities are used, since they are best suitable for compensating the fluctuations of these types of power suppliers. As an illustrative example, a model of wind and photovoltaic power systems with battery energy and pumped hydro storage facilities for power fluctuation reduction is included, and its power fluctuation reduction is verified through simulation.

A recent technological revolution in the fields of integrated MEMS has finally rendered possible the mechanical integration of active smart materials, electronics and power supply systems for the next generation of smart composite structures. Using a bi-dimensional array of electromechanical transducers, composed by piezo-patches connected to a synthetic negative capacitance, it is possible to modify the dynamics of the underlying structure. In this study, we present an application of the Floquet-Bloch theorem for vibroacoustic power flow optimization, by means of distributed shunted piezoelectric material. In the context of periodically distributed damped 2D mechanical systems, this numerical approach allows one to compute the multi-modal waves dispersion curves into the entire first Brillouin zone. This approach also permits optimization of the piezoelectric shunting electrical impedance, which controls energy diffusion into the proposed semi-active distributed set of cells. Furthermore, we present experimental evidence that proves the effectiveness of the proposed control method. The experiment requires a rectangular metallic plate equipped with seventy-five piezo-patches, controlled independently by electronic circuits. More specifically, the out-of-plane displacements and the averaged kinetic energy of the controlled plate are compared in two different cases (open-circuit and controlled circuit). The resulting data clearly show how this proposed technique is able to damp and selectively reflect the incident waves.

Past research and field trials have demonstrated the viability of active vibration control (AVC) technologies for the mitigation of human induced vibrations in problematic floors. They make use of smaller units than their passive counterparts, provide quicker and more efficient control, can tackle multiple modes of vibration simultaneously and adaptability can be introduced to enhance their robustness. Predominantly single-input-single-output (SISO) and multi- SISO collocated sensor and actuator pairs have been utilized in direct output feedback schemes, for example, with direct velocity feedback (DVF). On-going studies have extended such past works to include model-based control approaches, for example, pole-placement (PP), which demonstrate increased flexibility of achieving desired vibration mitigation performances but for which stability issues must be adequately addressed. The work presented here is an extension to the pole-placement controller design using an algebraic approach that has been investigated in past studies. An approximate pole-placement controller formulated via the inversion of the floor dynamics, considered as minimum phase, is designed to achieve target closed-loop performances. Analytical studies and experimental tests are based on a laboratory structure and comparisons in vibration mitigation performances are made with a typical DVF control scheme with inner loop actuator compensation. It is shown that with minimal compensation, primarily in the form of notch filters and gain adjustment, the approximate pole-placement controller scheme is easily formulated and implemented and offers good vibration mitigation performance as well as the potential for isolation and control of specific target modes of vibration. Predicted attenuations of 22dB and 12dB in both the first and second vibration modes of the laboratory structure were also realized in the experimental studies for DVF and the approximate PP controller.

Different methods for suppressing random (turbulence induced) vibrations of a plate like wing with embedded piezoceramics are investigated. An electromechanically coupled finite element model (that accounts different external circuits) is combined with unsteady aerodynamic models (the doublet-lattice method and Roger’s model) to develop a piezoaeroelastic model of cantilevered plates representing wing-like structures. An atmospheric turbulence model (Von-Karman’s and Dryden’s spectrum) is used to induce random vibrations at different airflow speeds. An active controller and different piezoelectric shunt circuits – passive and hybrid (combining passive circuits and voltage sources – are applied to suppress random vibrations over a range of airflow speeds when a single pair of piezoceramics is modeled on the clamped end of the plate. The behavior of the piezoaeroelastic system is investigated in time and frequency domains. Simulation results demonstrate that the hybrid control approach is more effective than purely passive or active controllers.

This paper aims to evaluate the effectiveness of MR damper for vibration mitigation of stay cable under complex wind excitations. The MR damper, RD-1005-03, provided by Lord Company was used, a semi-active control algorithm based on the universal design curve for linear dampers and the bilinear mechanical model of the MR damper was developed, and simulation study was carried out for the cable-MR damper system. Firstly, fluctuating wind field was generated using the method of weighted amplitude wave superposition (WAWS) and Kaimal spectrum and the time-history sample curve of turbulent wind speed of stay cable was obtained. Then the dynamic response of the cable-MR damper system was computed with the proposed semi-active control algorithm applied for mitigating the vibration of stay cable. Finally, the effectiveness of MR damper for controlling cable vibration was assessed by comparing the dynamic responses of stay cable before and after damper installation.

The proposed article deals with a new control technique for the vibration reduction of flexible structures based on modal approach and named Dependent Modal Space Control (DMSC). The well-known Independent Modal Space Control (IMSC), devised in the '80 s, by using diagonal control gain matrices, allows changing the frequency and the damping of the controlled modes leaving the mode shapes unaltered. The DMSC, instead, besides frequency and damping, can also impose the controlled mode shapes by making use of full control gain matrices. This will be the first way in which the DMSC can be applied allowing the creation of virtual nodes in desired point of the structure with consequent advantages in many applications. In the majority of control problems, due to the limited number of sensors-actuators available and the worsening spillover effects, the generic eigenvector imposition is not possible thus the same method is applied in a different way. Imposed the desired controlled poles, the optimal eigenstructure assignment can be suitably computed through a Genetic Algorithm in order to reduce the structure vibration by minimizing an Input-Output performance index in a desired frequency range depending on the physics of the problem. In this second application of the DMSC the stability of a determined number of modes in closed loop can be ensured constraining the optimization. In order to prove the advantages of this new method, a comparison of the IMSC and DMSC using a numerical and experimental simulation on a cantilevered beam Finite Element Method (FEM) model is provided.

The present paper derivate the asymptotic solution of modal damping of one taut stay cable attached with one passive damper including damper stiffness and viscous damping. The effect of the damper stiffness on the modal damping of the stay cable-passive system was analytical investigated. On the basis of the asymptotic solution of modal damping of one stay cable attached with one passive damper with the effect of cable stiffness and by using the decay factor of damper stiffness and the decay factor of cable sag, maximum modal damping ratio and corresponding optimal damping coefficient, which indicates the relationships of the characteristics of the damper and the cable sag was theoretically analyzed. Numerical analysis of parameters on the effect of dynamic performance of the controlled stay cable was conducted.

Recently, prosthetic knees in the developing stage are usually tested by installing them on amputees’ stumps directly or on above-knee prostheses (AKPs) test platforms. Although amputees can fully provide the actual motion state of the thigh, immature prosthetic knees may hurt amputees. For AKPs test platforms, it just can partly simulate the actual motion state of the thigh with limitation of the motion curve of the thigh, the merits or demerits of newly developed bionic above-knee prosthetic knees cannot be accessed thoroughly. Aiming at the defects of two testing methods, this paper presents a bio-inspired AKPs test system for bionic above-knee prosthetic knees. The proposed bio-inspired AKPs test system is composed of a AKPs test platform, a control system, and a bio-inspired system. The AKPs test platform generates the motion of the thigh simulation mechanism (TSM) via two screw pairs with servo motors. The bio-inspired system includes the tester and the bio-inspired sensor wore by the tester. The control system, which is inspired by the bio-inspired system, generates the control command signal to move the TSM of the AKPs test platform. The bio-inspired AKPs test system is developed and experimentally tested with a commercially available prosthetic knee. The research results show that the bio-inspired AKPs test system can not only ensure the safety of the testers, but also track all kinds of the actual motion state of the thigh of the testers in real time.

This paper presents modeling and analysis methods for design of a acoustic metamaterial panel consisting of two isotropic plates and small membrane-mass subsystems for absorption of low frequencies transverse elastic waves. Two models of a unit cell are derived and used to demonstrate the existence of negative effective material properties. Moreover, the design of experiment sample confirms that the model and analysis methods are valid. (1) The frequency of the membrane-mass subsystems are uniform distribution in whole acoustic metamaterial panel have two vibration models. (2) The different distributions of membrane-mass subsystems and their resonance frequencies result in different vibration isolation characteristics. (3) PSV is used to test and the result show that a low frequency wave absorber does not require nano-manufacturing techniques. (4) If we design the frequency of the membrane-mass subsystems different it can change the character of the metamaterial panel.

The work presented aims at modeling, designing and implementing an energy harvesting system capable of generating electricity from environmental vibrations. Subject of the analysis is a piezoelectric bimorph; this particular transducer, composed of two layers of piezoceramic material, is clamped in a cantilever configuration and is dynamically bent due to vibrations. The resulting deformation ensures enough current to power the electronic circuit of a wireless sensor. An analytical model is adopted, that describes the dynamics of the mechanical system using an electrical duality. In particular the coupling of the variables is represented by an equivalent transformer. The obtainable voltage and power are investigated, focusing on the influence of the electric load on the performance of the conversion process. In addition, to overcome the limitations related to the analytical study, a finite element model is provided, capable of simulating the behavior of the system more accurately. Finally, both models are validated by means of experimental tests, showing the mutual influence between the mechanical and the electrical domain.

Continuous electrode configuration (CEC) has been widely used in piezoelectric energy harvesters (PEHs). A PEH with CEC works around the first resonance efficiently but it suffers from low efficiency due to cancellation effect around higher modes. The use of segmented electrode configuration (SEC) can avoid the cancellation effect around higher modes. To achieve this, the output from each electrode pair on the opposite sides of the strain node needs to be rectified separately. In such a case, the theoretical formulation for power estimation becomes challenging because of some nonlinear electrical components included. In this paper, a method based on combining the equivalent circuit model (ECM) and the circuit simulation is proposed to estimate the power outputs of the cantilevered PEH with the SEC. First, the parameters in the ECM considering multiple modes of the PEH with the SEC are identified from the finite element analysis. The ECM is then established and simulated in the SPICE software. The optimal power outputs from the PEH with the SEC are compared with those from the PEH with the CEC. The results illustrate the advantage of the SEC to enhance the power outputs of a PEH at higher resonance frequencies.

Recently, it is very popular in modern medical industry to adopt robotic technology such as robotic minimally invasive surgery (RMIS). Compared with open surgery, the RMIS needs the robot to perform surgery through the usage of long surgical instruments that are inserted through incision points. This causes the surgeon not to feel viscosity and stiffness of the tissue or organ. So, for the tactile recognition of human organ in RMIS, this work proposes a novel tactile device that incorporates with magnetorheological (MR) fluid. The MR fluid is fully contained by diaphragm and several pins. By applying different magnetic field, the operator can feel different force from the proposed tactile device. In order to generate required force from the device, the repulsive force of human body is firstly measured as reference data and an appropriate size of tactile device is designed. Pins attached with the diaphragm are controlled by shape-memory-alloy (SMA). Thus, the proposed tactile device can realize repulsive force and shape of organ. It has been demonstrated via experiment whether the measured force can be achieved by applying proper control input current. In addition, psychophysical experiments are conducted to evaluate performance on the tactile rendering of the proposed tactile device. From these results, the practical feasibility of the tactile device is verified.

The semi-active control technology has been paid more attention in the field of structural vibration control due to its high controllability, excellent control effect and low power requirement. When semi-active control device are used for vibration control, some challenges must be taken into account, such as the reliability and the control strategy of the device. This study presents a new large tonnage compound lead extrusion magnetorheological (CLEMR) damper, whose mathematical model is introduced to describe the variation of damping force with current and velocity. Then a current controller based on the fuzzy logic control strategy is designed to determine control currents of the CLEMR dampers rapidly. A ten-floor frame structure with CLEMR dampers using the fuzzy logic control strategy is built and calculated by using MATLAB. Calculation results show that CLEMR dampers can reduce the seismic responses of structures effectively. Calculation results of the fuzzy logic control strategy are compared with those of the semi-active limit Hrovat control structure, the passive-off control structure, and the uncontrolled structure. Comparison results show that the fuzzy logic control strategy can determine control currents of CLEMR dampers quickly and can reduce seismic responses of the structures more effectively than the passive-off control strategy and the uncontrolled structure.

The need for long-term solutions to power various wireless sensor systems has been driving the research in the area of energy harvesting for the past decade. The present paper brings forth an investigation into the realm of piezoelectric energy harvesting (PEH) using nonlinear vibrations. A piezoelectric cantilever beam with a magnetic tip mass interacting with additional magnets around it forms a multi-stable nonlinear PEH configuration. The study indicates that the multistable configuration provides a widened bandwidth as compared to the conventional linear PEH devices and an increased voltage output as compared to many other PEH devices. An experimental parametric study is conducted to arrive at an optimal configuration for the performance enhancement of the harvester along with a glimpse into the enhanced magnetostatic interactions equations and various possible magnetic nonlinear configurations for the given conditions.

The vibration reduction in mechanical systems can be performed by means of active control strategies. For non-linear and time-varying systems, a suitable choice is the use of an adaptive feedback solution, in which the identification system is a fundamental part of the control scheme. In this work, a non-model-based identification system is proposed and its results are used to automatically set the gain of the Direct Velocity Feedback (DVF) control law. The proposed adaptive control algorithm has been tested on a smart structure represented by a carbon fibre plate instrumented with strain gauge, accelerometers and piezoelectric patches.

The conversion of aeroelastic vibrations into low-power electricity has received growing attention in the energy harvesting literature. Most of the existing research on wind energy harvesting has focused on transforming flow-induced vibrations into electricity by employing electromagnetic or piezoelectric transduction mechanisms separately. In this work, a hybrid airfoil-based aeroelastic energy harvester that simultaneously exploits piezoelectric transduction and electromagnetic induction is analyzed based on fully coupled electroaeroelastic modeling. Both forms of electromechanical coupling are introduced to the plunge degree of freedom. The interaction between total power generation (from piezoelectric transduction and electromagnetic induction) and the linear electroaeroelastic behavior of the typical section is investigated in the presence of two separate electrical loads. The effects of systems parameters, such as internal coil resistance, on the total power output and linear flutter speed are also discussed.

An experimental investigation is carried out on a cantilever-type passive/active autoparametric vibration absorber, with a PZT patch actuator, to be used in a primary damped Duffing system. The primary system consists of a mass, viscous damping and a cubic stiffness provided by a soft helical spring, over which is mounted a cantilever beam with a PZT patch actuator actively controlled to attenuate harmonic and resonant excitation forces. With the PZT actuator on the cantilever beam absorber, cemented to the base of the beam, the auto-parametric vibration absorber is made active, thus enabling the possibility to control the effective stiffness and damping associated to the passive absorber and, as a consequence, the implementation of an active vibration control scheme able to preserve, as possible, the autoparametric interaction as well as to compensate varying excitation frequencies and parametric uncertainty. This active vibration absorber employs feedback information from a high resolution optical encoder on the primary Duffing system and an accelerometer on the tip beam absorber, a strain gage on the base of the beam, feedforward information from the excitation force and on-line computations from the nonlinear approximate frequency response, parameterized in terms of a proportional gain provided by a voltage input to the PZT actuator, thus modifying the closed-loop dynamic stiffness and providing a mechanism to asymptotically track an optimal, robust and stable attenuation solution on the primary Duffing system. Experimental results are included to describe the dynamic and robust performance of the overall closed-loop system.

Due to their two-way electromechanical coupling effect, piezoelectric transducers can be used to synthesize passive vibration control schemes, e.g., RLC circuit with the integration of inductance and resistance elements that is conceptually similar to damped vibration absorber. Meanwhile, the wide usage of wireless sensors has led to the recent enthusiasm of developing piezoelectric-based energy harvesting devices that can convert ambient vibratory energy into useful electrical energy. It can be shown that the integration of circuitry elements such as resistance and inductance can benefit the energy harvesting capability. Here we explore a dual-purpose circuit that can facilitate simultaneous vibration suppression and energy harvesting. It is worth noting that the goal of vibration suppression and the goal of energy harvesting may not always complement each other. That is, the maximization of vibration suppression doesn’t necessarily lead to the maximization of energy harvesting, and vice versa. In this research, we develop a fuzzy-logic based algorithm to decide the proper selection of circuitry elements to balance between the two goals. As the circuitry elements can be online tuned, this research yields an adaptive circuitry concept for the effective manipulation of system energy and vibration suppression. Comprehensive analyses are carried out to demonstrate the concept and operation.

In the present work, a computer based smart integrated energy monitoring and management system for standalone photovoltaic systems is designed and implemented. Monitoring, controlling, and recording features are fully obtained in the present system using an efficient programming environment. All required data are monitored as real-time data therefore the system status is continuously evaluated and decisions are made to take immediate actions. The energy consumption of different appliances are automatically controlled and optimized using a hierarchical self adaptive algorithm based on input data and real-time information provided by the system sensors. The proposed system is successfully implemented for photovoltaic modules under realistic operating conditions.