This PDF file contains the front matter associated with SPIE Proceedings Volume 10595, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

This paper investigates the efficiency and the effectiveness of the stabilization control which makes the highest-energy steady-state solution of a nonlinear wideband piezoelectric vibration energy harvester globally stable. For the conventional linear vibration energy harvester, there is a trade-off between the bandwidth of the resonance peak and the performance of the power generation in the resonance frequency band. A nonlinear harvester can expand the resonance frequency band to generate larger electric power in a wider frequency range. However, since the nonlinear oscillator can have multiple stable steady-state solutions in the resonance band, it is difficult for the nonlinear vibration energy harvester to maintain the response in the highest-energy solution under the presence of disturbances. A self-excitation circuit has been proposed to make it possible to stabilize the highest-energy solution globally for a nonlinear piezoelectric vibration energy harvester. The self-excitation circuit consists of a switch that connects/disconnects the load circuit and a positive velocity feedback circuit. This circuit can destabilize other unexpected lower-energy solutions and entrain the oscillator only in the highest-energy solution by providing electric energy to the piezoelectric elements. In this study, numerical analyses and experiments are conducted to show that the proposed self-excitation control can provide the global stability to the high-energy solution and maintain the performance of the power generation in the widened resonance frequency band. Furthermore, the energy consumption by the self-excitation circuit is evaluated by numerical analyses in order to find more efficient control law to realize the self-powered control circuit.

Magnetically coupled energy harvesters have been demonstrated to achieve broad tuning of nonlinear behaviors and multi-directional dynamic response by adjusting the relative spacing among magnets. Such flexibility permits a wide accommodation to diverse ambient base excitations for energy conversion and capture. Yet, the magnetic coupling of an energy harvesting system has not been examined as a useful means to enhance energy harvesting outcomes when the excitation source contains the impulsive excitations commonly encountered in ambient environments. To obtain new understanding on the effectiveness of magnetic coupling, a nonlinear vibration energy harvesting system is devised and studied for the electrodynamic responses and direct current power charging that are enabled by impulsive excitations. By comparing experimental and numerical simulation results, the energy harvesting system model is firstly validated. The studies demonstrate the sensitivity of total energy collection on change in the impulse characteristics. The findings reveal that nonlinear snap-through behaviors induced by bistable nonlinearities with magnetic coupling are effective for DC power charging, so long as an impulsive excitation threshold is met. Results from this research emphasize the importance of accurately quantifying the magnetic coupling effects towards characterizing the sensitivities the energy harvesting system when subjected to impulsive excitations.

An internal bypass magnetorheological damper (MRD) with twin cylinders (Bai et al., 2013, Magnetorheological damper utilizing an inner bypass for ground vehicle suspensions, IEEE Transactions on Magnetics, 49(7): 3422-3425) was proposed for both vibration and shock control systems. In the internal bypass MRD, the gap between the inner and outer cylinders is the flow gap for MR fluids. The coil winding is wound on the inner cylinder to provide the electromagnetic field. The mechanical responses of the internal bypass MRD, including the controllable damping force and response time, are modeled and analyzed in this paper. The corresponding experimental tests are carried out to validate using selfdeveloped test systems.

During the last years, the research interest in assessing noise and vibration optimization has been addressed on different control typologies, based both on active and passive architectures. Within the paper, some preliminary activities aimed at the realization of a structurally simple, cheap and easily replaceable active control systems is discussed. Under these premises, the paper deals with the assessment of an Enhanced Synchronized Shunted Switch Architecture (SSSA) control architecture, based upon the use of piezoelectric devices, specifically optimized for a cantilver beam structure. Main activities regarded the control system set up and optimization, both under the electronic than the piezo location points of view, and control results under deterministic and stochastic forcing actions. Experimental results have been compared with the numerical one as well as a comparison between the SSSA approach and other active control architectures has been also presented and discussed. Results have shown a good performances of the proposed approach that present also a relative easy implementation if compared with already assessed control technologies.

Various researchers have investigated the behavior of a linear oscillator weakly coupled to a nonlinear mechanical attachment that has essential stiffness nonlinearity. Under certain conditions, the essentially nonlinear attachment can act as a nonlinear energy sink (NES) and the irreversible transfer of vibration energy from a main structure to the nonlinear attachment is observed. Another characteristic of an essentially nonlinear attachment is the nonexistence of a resonance frequency. Therefore, nonlinear energy sinks have increased robustness against detuning. While mechanical nonlinear attachments are usually linked to a host structure by nonlinear mechanical elements, linear coupling (piezoelectric transduction) is observed in piezoelectric based nonlinear energy sinks and nonlinearity can be achieved through electrical circuit design. This work presents an experimentally validated piezoelectric based nonlinear energy sink. An essentially nonlinear piezoelectric shunt circuit and its practical realization are discussed in detail. The circuit nonlinear behavior and the performance of the piezoelectric nonlinear energy sink to attenuate vibrations of a cantilever over a wide range of frequencies are experimentally validated.

Piezoelectric-based state switching selectively switches between available stiffness states. Some state switching methods require switching from a high- to low-stiffness state at points in the vibration cycle of non-zero strain, resulting in a rapid dissipation of the stored piezoelectric voltage, and a corresponding rapid variation in the system stiffness. This manner of switching induces high-frequency, large-amplitude mechanical transients that are unavoidable and is analogous to an impact, where increasing the switch duration reduces the range of modes excited. Recent develops show that controlling the duration of the voltage dissipation by means of a resistor in the shunt circuit significantly reduces these induced transients; however, incorporating a resistor in the shunt can introduce damping which may be undesirable, depending on the application. As such, this paper numerically investigates an alternate method of controlling the duration of the switch via a variable capacitance shunt.

A novel semi-active damping device termed Variable Friction Cladding Connection (VFCC) has been previously proposed to leverage cladding systems for the mitigation of natural and man-made hazards. The VFCC is a semi-active friction damper that connects cladding elements to the structural system. The friction force is generated by sliding plates and varied using an actuator through a system of adjustable toggles. The dynamics of the device has been previously characterized in a laboratory environment. In this paper, the performance of the VFCC at mitigating non-simultaneous multi-hazard excitations that includes wind and seismic loads is investigated on a simulated benchmark building. Simulations consider the robustness with respect to some uncertainties, including the wear of the friction surfaces and sensor failure. The performance of the VFCC is compared against other connection strategies including traditional stiffness, passive viscous, and passive friction elements. Results show that the VFCC is robust and capable of outperforming passive systems for the mitigation of multiple hazards.

The paper is focuses on the development of a theoretical framework together with an experimental validation to investigate rotational piezoelectric energy harvesting. The proposed device includes an electrically rectified piezoelectric bimorph mounted on a stationary base with a magnet attached to its free end. Energy is harvested by vibration of beam induced by non-contact rotary magnetic plucking. The DC power frequency response is predicted and found to be in good agreement with experiment. It shows that the harvested DC power is around 1 mW in average with the rotational frequency ranging from 5 Hz to 14 Hz. In addition, the parallel connection of two piezoelectric oscillators with respective electrical rectification is considered. It is observed that the power output of the array is the addition of the response from each individual piezoelectric oscillator.

In the studies of piezoelectric energy harvesting (PEH) systems, literature has shown that the circuit solution has a significant effect towards the enhancement of energy harvesting capability under resonance. Some studies started to investigate its bandwidth-broadening effect recently. This paper provides a comprehensive comparison on the impact of circuit solutions towards the broadband and high-capability energy harvesting. The comparison is intuitively presented based on the equivalent impedance model. The joint dynamics and harvested power of the PEH systems using different interface circuits are thoroughly discussed. Simulation and experiments show good agreement with the analysis. It is shown that, within the existing circuit solutions, the currently proposed phase-variable synchronized parallel triple bias-flip (PV-P-S3BF) circuit provides the most extensive span of electrically induced damping and electrically induced stiffness/mass. By tuning the values of the two equivalent components in operation, the tasks of harvesting capability enhancement and bandwidth broadening can be simultaneously made by using PV-P-S3BF.

In this paper, we investigate the feasibility of energy harvesting from the torsions using a piezoelectric beam. The piezoelectric beam is partially patterned and is tested in an experimental setup to force pure torsional deformation. In particular, the beam consists of two identical piezoelectric parts attached on one side of a supporting substrate. We propose a model for the energy harvesting system through the equations for a slender composite beam with the physical properties and the electromechanical coupling equations of the piezoelectric material. The theoretical predictions are validated by the comparison with the experimental results.

This paper aims to improve the off-resonance energy harvesting performance of a vibration-based energy harvesting system by exploiting the dynamic interaction between two attractive magnets. A static force-displacement model is firstly derived by a simple experiment to describe the magnetic force and then extended to the dynamic model to characterize the transient interaction of the magnets. A theoretical model is developed and experimentally verified to be capable of accurately predicting the voltage and power outputs of the proposed off-resonance energy harvesting system with different resistive loads. The performance of the proposed energy harvesting system under off-resonance excitations is examined and evaluated by comparing with the one of the system without magnetic interaction. Results reveal that the nonlinear dynamic force induced by the relative motion between the two magnets could significantly enhance the off-resonance power output. The influence of the distance between the two magnets, as well as the external resistive load, on the voltage and off-resonance power outputs of the system is studied. The proposed magnetic field enhanced energy harvesting system has 1760 times more power output than the counterpart system without magnetic interaction at the off-resonance harmonic excitation of 3 Hz and 0.5 m/s² and an optimal resistance of 20 kΩ.

Recently, space structures are getting larger and more complex because of the more demanding requirements in the space mission. Constructing large structures in space has several challenging issues such as assembly, maintenance and delivering cost. Deployable structures can be the appropriate solution to construct large space structures. Employing bistable characteristics can provide additional advantages to the deployable structure for solving these issues because the overall system can be made relatively simple as well as reliable. In this study, a new concept of the deployable structure using bistable characteristics is proposed. Due to the bistability, both folded and deployed states of the proposed deployable structure can stay under the stable state. The mathematical model of the single bistable component is established to analyze the effect of the off-axis ratio on the characteristics of the proposed structure. In order to analyze the deployment behavior of the proposed structure, the dynamic model of the single bistable component is established. The driving force from the SMA spring is measured from an experiment. By applying the force profiles to the dynamic model, the simulation of the proposed structure is conducted. In order to validate the dynamic model, the experimental model is constructed and the deployment process is captured. The comparison of the simulated and experimental results shows good agreement.

The design and application of adaptive devices are currently ambitious targets in the field of aviation research addressed at new generation aircraft. The development of intelligent structures involves aspects of multidisciplinary nature: the combination of compact architectures, embedded electrical systems and smart materials, allows for developing a highly innovative device. The paper aims to present the control system design of an innovative morphing flap tailored for the next generation regional aircraft, within Clean Sky 2 – Airgreen 2 European Research Scenario. A distributed system of electromechanical actuators (EMAs) has been sized to enable up to three operating modes of a structure arranged in four blocks along the chord-wise direction:

•overall camber-morphing;

•upwards/downwards deflection and twisting of the final tip segment.

A state-of-art feedback logic based on a decentralized control strategy for shape control is outlined, including the results of dynamic stability analysis based on the blocks rational schematization within Matlab/Simulink® environment. Such study has been performed implementing a state-space model, considering also design parameters as the torsional stiffness and damping of the actuation chain. The design process is flowing towards an increasingly “robotized” system, which can be externally controlled to perform certain operations. Future developments will be the control laws implementation as well as the functionality test on a real flap prototype.

The in-flight control of the wing shape is widely considered as one of the most promising solutions to enhance the aerodynamic efficiency of the aircraft thus minimizing the fuel burnt per mission ([1]-[26]). In force of the fallout that the implementation of such a technology might have on the greening of the next generation air transport, ever increasing efforts are spent worldwide to investigate on robust solutions actually compliant with industrial standards and applicable airworthiness requirements. In the framework of the CleanSky2, a research program in aeronautics among the largest ever founded by the European Union, the authors focused on the design and validation of two devices enabling the camber-morphing of winglets and flaps specifically tailored for EASA CS-25 category aircraft ([29]). The shape transition was obtained through smart architectures based on segmented (finger-like) ribs with embedded electromechanical actuators. The combined actions of the two smart systems was conceived to modulate the load distribution along the wing while keeping it optimal at all flight conditions with unequalled benefits in terms of lift-over-drag ratio increase and root bending moment alleviation. Although characterized by a quasi-static actuation, and not used as primary control surfaces, the devices were deeply analysed with reference to their impact on aircraft aeroelastic stability. Rational approaches were adopted to duly capture their dynamics through a relevant number of elastic modes; aeroelastic coupling mechanisms were identified in nominal operative conditions as well as in case of systems’ malfunctioning or failure. Trade off flutter and divergence analyses were finally carried out to assess the robustness of the adopted solutions in terms of movable parts layout, massbalancing and actuators damping.

A morphing structure can be considered as the result of the synergic integration of three main systems: the structural system, based on reliable kinematic mechanisms or on compliant elements enabling the shape modification, the actuation and control systems, characterized by embedded electromechanical actuators and robust control strategies, and the sensing system, usually involving a network of sensors distributed along the structure to monitor its state parameters. Technologies with ever increasing maturity level are adopted to assure the consolidation of products in line with the aeronautical industry standards and fully compliant with the applicable airworthiness requirements. In the framework of the CleanSky2, one of the largest research projects ever funded by the European Union, a novel multi-modal camber morphing flap was conceived for the enhancement of the aerodynamic performances of the next generation green regional aircraft. Thanks to different morphing modes, the shape of the flap can be suitably adapted in order to preserve an optimal configuration as the aircraft trim parameters change according to the specific flight phase (take-off, climb, cruise, descent, landing). To further improve the benefits brought by such technology on the wing aerodynamic efficiency, an active flow control system based on plasma synthetic jet (PSJ) actuators was investigated for a potential installation on the upper skin of the flap. PSJ actuators, or Sparkjets, are able to produce very high jet velocities, without the aid of any moving parts, affecting the structure of the flow-field to be controlled and allowing a positive variation of the aerodynamic forces on the aircraft, with a modest power consumption. This work is focused on the two main aspects related to the feasibility of PSJ actuators integration into the adaptive flap skin: the thermal and electromagnetic interferences of the actuators with the other electronic equipment of the flap. Experimental measurements were carried out to characterize the thermal and the electromagnetic fields induced by the operating device into the surrounding structure. A simplified test article was designed and manufactured to support all experimental activities while being fairly representative of the actual PSJ-skin assembly. Test results allowed for a definition of the safety-critical areas for the installation of flap actuation, control and sensing systems.

The Train of Frozen Boxcars (TFB) model has been developed for a continuous piezoelectric cantilever fluidic harvester to simplify the effective one-way interaction between the fluid and the structure for certain flows. The TFB model treats the force due to vortex or turbulent flow as a series of boxcars of different amplitudes, widths and separations advected with a constant velocity over a piezoelectric beam. In this paper, the effect of five parameters, namely the number, amplitude, width, spatial separation and advection speed of the boxcars in the TFB forcing model, is studied for four different forcing scenarios. It has been observed that an increase in the amplitude or advection velocity of the boxcars leads to an increase in the power output, whereas a saturation limit in the power output is observed with an increase in the width or number of boxcars. More importantly, however, it is concluded that the separation between boxcars is the determining factor in maximizing or minimizing the power output from the harvester.

For supplying water monitoring systems at points of use over their entire application period an in-pipe flow harvester is proposed. It eliminates the maintenance requirements of current energy supplies such as batteries. This harvester exploits the piezoelectric properties of Polyvinylidenedifluoride (PVDF) to convert turbulence-induced oscillations into electrical energy. It is intended to be used in water pipes with diameters of ¾ in. and above. Turbulences induced by an upstream arranged ring-shaped bluff body force a wrap of piezoelectric films to oscillate, thus generate electrical charge. The wrap consists of two layers of 30 μm thick and 12 mm wide PVDF layered alternately with two centered 6µm thick and 8mm wide aluminum electrodes. It is sealed by a shell of polyethylene.

A bottom-fixed wrap with 3 windings is characterized in a 1in. water pipe at a flow velocity of 0.75 m/s. It delivers a constant power output of 0.53 μW at a 2.3 MΩ load and an effective voltage of 1.1 V. Considering the extremely low power requirements of modern sensors, several harvesters may be combined to supply such devices.

Resonant fluidic harvesters can typically be tuned to the frequency of the flow, so they yield a larger power output compared to their non-resonant counterparts. In order to explore increasing this output for non-resonance harvesters, a feasibility study has been performed to analyze the behavior of two side-by-side piezoelectric harvesters in low-intensity (less than 0.5%) grid-generated turbulence with respect to beam configurations, mean flow velocity, distance from the grid and separation between the two beams. Experimental results show that the potential for energy harvesting is perhaps not as great in the low mean-velocity flow as it is for the higher speed cases which are accompanied by flutter, but the side-by-side piezoelectric beams display potential for use as turbulence sensors at low speeds.

For bio-inspired, fish-like robotic propulsion, the Macro-Fiber Composite (MFC) piezoelectric technology offers noiseless actuation with a balance between actuation force and velocity response. However, internal nonlinear- ities within the MFCs, such as piezoelectric softening, geometric hardening, inertial softening, and nonlinear dissipation, couple with the hydrodynamic loading on the structure from the surrounding fluid. In the present work, we explore nonlinear actuation of MFC cantilevers underwater and develop a mathematical framework for modeling and analysis. In vacuo resonant actuation experiments are conducted for a set of MFC cantilevers of varying length to width aspect ratios to validate the structural model in the absence of fluid loading. These MFC cantilevers are then subjected to underwater resonant actuation experiments, and model simulations are compared with nonlinear experimental frequency response functions. It is observed that semi-empirical hydro- dynamic loads obtained from quasilinear experiments have to be modified to account for amplitude dependent added mass, and additional nonlinear hydrodynamic effects might be present, yielding qualitative differences in the resulting underwater frequency respones curves with increased excitation amplitude.

As a nonlinear system, bistable energy harvester produces large amplitude vibration and high energy output since it allows the system transit from one stable state to the other. However, it is challenging to activate the high-energy orbit oscillation in ambient environments, where vibration level would be low. This paper proposes a method that an electrical coupling between an electromagnetic energy harvester and a piezoelectric energy harvester is used to help the hybrid system overcome the potential well barrier and maintain in the high-energy orbit. A control switch is employed to electrically connect or disconnect the two energy harvesters. The interaction between them will bring the system from low-energy orbit to high-energy orbit. Benefited from nonlinear features with the coupling, both energy harvesters will stay on the high-energy orbit after the coupling action. Harmonic balance method is employed to demonstrate the multi-solution characteristics of the bistable energy harvester. Furthermore, a coupled model based on Hamilton’s principle and Kirchhoff’s circuit laws is developed to reveal the jumping phenomenon. Simulation results show that high-energy orbit is achieved and maintained after the coupling. Our proposed solution requires no complex structure design or external power source, so as to provide a feasible and reliable solution to address the critical issue of bistable energy harvesters in practical applications.

Vibration energy harvesters have been proposed as an autonomous power source for meeting the limited power requirements of present-day sensors and electronics that find extensive usage in structural health monitoring systems. Recent research reveals that nonlinear energy harvesters outperform their linear counterparts, designed to operate on the principle of resonance, owing to their wide frequency bandwidth which allows for better performance in realistic operational environments. Particularly, bi-stable energy harvesters designed to exploit piezoelectricity to achieve the mechanical to electrical energy conversion have been widely investigated in literature. Additionally, several investigations have been also proposed to enhance power conversion in linear harvesters by introducing nonlinear circuits, e.g. based on synchronized switching (SS). In this respect, unveiling the effects on the bandwidth and coexisting solutions in the response of strongly nonlinear electrical SS shunts interacting with multi-stable structures requires further investigation. In particular, synchronized switch harvesting on inductor (SSHI) circuits, when connected in parallel with bi-stable energy harvesters, facilitate an increase in the harvested voltage, thus allowing for higher power generation as compared to a standard shunt load. This paper investigates the effects of utilizing a SSHI circuit for enhancing the power output in the different dynamical regimes of a bi-stable energy harvester. In particular, we present a comprehensive study of the efficiency of the SSHI circuit when the response configuration of the system is shifted between coexisting dynamical states of the bi-stable harvester. The herein presented semi-analytical and numerical results show that the qualitative performance of the SSHI circuit is quite robust in terms of superiority over the standard load circuit. However, the quantitative nature of the increase in power harvested by the SSHI circuit is sensitive to the optimal load in the circuit, which in turn varies with the dynamical state of the system.

Energy harvesting from smart tire has been an influential topic for researchers over several years. In this paper, we propose novel energy harvester for smart tire taking advantage of adaptive tuning stochastic resonance. Compared to previous tire energy harvesters, it can generate large power and has wide bandwidth. Large power is achieved by stochastic resonance while wide-bandwidth is accomplished by adaptive tuning via centrifugal stiffening effect. Energy harvesting configuration for modulated noise is described first. It is an electromagnetic energy harvester consists of rotating beam subject to centrifugal buckling. Equation of motion for energy harvester is derived to investigate the effect of centrifugal stiffening. Numerical analysis was conducted to simulate response. The result show that high power is achieved with wide bandwidth. To verify the theoretical and simulation results, the experiment was conducted. Equivalent horizontal rotating platform is built to mimic tire environment. Experiment results showed good agreement with the numerical result with around 10% of errors, which verified feasibility of proposed harvester. Maximum power 1.8mW is achieved from 3:1 scale experiment setup. The equivalent working range of harvester is around 60-105 km/h which is typical speed for car in general road and highway.

In this study, the use of the twisted string concept with a pin, serving as a moment arm, is proposed to produce the snapthrough of a pre-compressed beam so that the whole system can be used as an effective on/off actuator. The twisted string mechanism is to produce a horizontal pulling force to the pin, which triggers the snap-through of the beam. The actuation moment required to trigger the bistable beam in this study is 24.3 Nmm, corresponding to a horizontal force of 0.81 N. The twisted string actuator is able to produce a pulling force of 1 N, which is further pulled through a distance of 5-mm. Static performance of the integrated system based on the effects of the length of the string on the required input motor voltage, torque, and the overall system response time is experimentally investigated. The snap-through sequence during the static experiment is also captured with a high-speed camera. The input voltage to the motor increases as the length of the string is increased. The length of the string also affects the overall system response, motor speed and torque. The whole snap-through of the beam happens within 100 msec after the trigger signal is sent.

Snap-through oscillation has been widely utilized in nonlinear energy harvesting for power improvement and bandwidth enlargement. In this paper, the snap-through phenomenon of a bistable dual-beam vibration energy harvester (DB-VEH) when driven by harmonic and random excitations is investigated. First, the electromechanical model is established and the parameters are determined by experimental tests. Subsequently, the dynamic responses under different levels of excitation are simulated and the corresponding experiments are conducted. Results indicate that the bistable DB-VEH can achieve the inter-well and chaotic oscillations near the first and second resonances, providing two frequency bands of snap-through, which is helpful for enlarging the bandwidth. For the inter-well oscillation, the remarkably increased output of one beam is always in sacrifice of the efficiency of the other beam, resulting in an outperformed beam and an underperformed one. Finally, the performance when the bistable DB-VEH is under a random excitation is investigated in comparison with that of its linear counterpart. Results indicate that, thanks to the snap-through phenomenon, the standard deviation of voltage of a bistable DB-VEH is much higher than that of a linear DB-VEH for a certain range of intensity.

In this study, the dynamics of a lattice of bistable elements connected by linear springs are investigated with emphasis on the spatial dependence of the response profiles created by the nonlinear transition wave. We address the difficulty in creating a permanent-form transition wave in real-world settings even though such a solution theoretically exists and explain how to utilize the speed difference in wave propagation to minimize this undesirable behavior through numerical investigations. We further introduce dissipative elements along with asymmetric on-site potentials to the baseline lattice and show that almost perfect response invariance can be achieved, where the response is not only spatially independent but also input-independent.

This paper presents a novel design of a magnetically-sprung mechanical resonator for electromagnetic vibration energy harvesting. The proposed resonator consists of a plastic cylinder, a moving magnet encapsulated in the cylinder, and two fixed ring magnets fitted on the cylinder suspending the moving magnet between them. The magnetic poles of the ring magnets are arranged so that the face opposed to the moving magnet has the opposite polarity. Thanks to this arrangement, the ring magnet attracts the moving magnet when it is far, but repels it when it comes close. This means that a single ring magnet can stably hold the moving magnet at its equilibrium, and the magnetic force between them is highly nonlinear. As a result, the overall restoring force-displacement relationship shows variety of nonlinear characteristics, from high-stiffness monostability to low-stiffness essential nonlinearity and even bistability, depending on the distance between the ring magnets. Simplified and detailed mathematical models of the proposed magnetic spring are presented to understand the dependence of the force-displacement characteristics on the design parameters. The numerical model of a prototype harvester is investigated to demonstrate the tunability of the resonance frequency by adjusting the axial position of the ring magnets.

Motivated by the sophisticated geometries in origami folding and the fluidic actuation principle in nastic plant movements, the concept of fluidic origami cellular structure was proposed for versatile morphing and actuation. The idea is to assembly compatible origami sheets into a cellular architecture, and apply fluidic pressure into its naturally embedded tubes to achieve effective shape reconfigurations. Despite the promising potentials, the actuation capabilities of fluidic origami, such as free stroke and blocking force, are not elucidated. Especially, we do not understand the effects of thick facet material compliance and pressure-sealing end caps. This research aims to address these issues by incorporating realistic considerations into the design, fabrication, and analysis of fluidic origami. We construct CAD models of fluidic origami tubes that incorporate the finite facet material thickness and flat end caps. Various design parameters are chosen carefully to ensure that they can be fabricated via commercially accessible 3D printing techniques. These models are then used to analyze the actuation performance via finite element simulation (FEA). Results show that the undesired effects from end caps are limited to the unit cells at the tube ends, and fluidic origami can indeed provide robust actuation and morphing capability.

Animal locomotion and movement requires energy, and the elastic potential energy stored in skeletal muscle can facilitate movements that are otherwise energetically infeasible. A significant proportion of this energy is captured and stored in the micro- and nano-scale constituents of muscle near the point of instability between asymmetric equilibrium states. This energy may be quickly released to enable explosive macroscopic motions or to reduce the metabolic cost of cyclic movements. Inspired by these behaviors, this research explores modular metastructures of bistable element chains and develops methods to release the energy stored in higher-potential system configurations. Quasi-static investigations reveal the role of state-transition pathways on the overall efficiency of the deployment event. It is shown that sequential, local release of energy from the bistable elements is more efficient than concurrent energy release achieved by applying a force at the free end of the structure. From dynamic analyses and experiments, it is shown that that the energy released from one bistable element can be used to activate the release of energy from subsequent links, reducing the actuation energy required to extend or deploy the chain below that required for quasi-static deployment. This phenomenon is influenced by the level of asymmetry in the bistable constituents and the location of the impulse that initiates the deployment of the structure. The results provide insight into the design and behavior of asymmetrically multistable chains that can leverage stored potential energy to enable efficient and effective system deployment and length change.

Inspired by evolutionary game theory, the biological game of replicator dynamics is investigated for vibration control of bridge structures subjected to earthquake excitations. Replicator dynamics can be interpreted economically as a model of imitation of successful individuals. This paper uses replicator dynamics to reduce vibrations while optimally allocating the control device forces. The control algorithm proposed is integrated with a patented neural dynamic optimization algorithm to find optimal growth rate values with the goal of achieving satisfactory structural performance with minimum energy consumption. A model is described for hybrid vibration control of smart highway bridge structures subjected to earthquake loading.

Energy transfer inside the fluid domain and altering the natural flow state or development path into a more desirable state or path, are extensive and ever-expanding areas of research and application. In this research, we investigate the energy transfer by coupling multiple vibrating structures through flow interactions in an otherwise quiescent fluid. Arrays of closely-spaced, clamped piezoelectric macro-fiber composite bimorphs (which are actuators or sensors) are attached perpendicular to the bottom surface of a tank. The coupling of the vibrating bimorphs due to their interaction with the surrounding fluid is investigated. We study the modal coupling to explore the energy exchange and the induced flow pattern through controlling the parameters such as size, pattern, the density of the attached bimorphs, and the magnitude and frequency of the actuation voltage. An analytical study, supported by experiments, is performed to assess the velocity and output voltage response of the bimorphs to see their effects on the interconnection between the induced fluid-particle dynamics and the geometric and electroelastic properties of the sensor bimorphs. Characterization of the electrohydroelastic dynamics of the active and interacting bimorphs and the induced fluid motion is done by focusing on the vibration of the actuator, vibration and electrical responses of the piezoelectric bimorphs, and the inertia and drag terms.

In this research, we numerically and analytically investigate the nonlinear energy transmission phenomenon in a metastable modular metastructure. Numerical studies on a 1D metastable chain provide clear evidence that when driving frequency is within the stopband of the periodic structure, there exists a threshold for the driving amplitude, above which sudden increase in the energy transmission can be observed. This onset of transmission is due to nonlinear instability and is known as supratransmission. We discover that due to spatial asymmetry of strategically configured constituents, such transmission thresholds are considerably different when structure is excited from different ends and this discrepancy creates a region of non-reciprocal energy transmission. We demonstrate that when the loss of stability is due to saddlenode bifurcation, the transmission threshold can be predicted analytically using a localized nonlinear-linear system model, and analyzed via combining harmonic balancing and transfer matrix methods. These investigations elucidate the rich and complex dynamics achievable by nonlinearity and metastabilities, and provide synthesize tools for tunable bandgaps and non-reciprocal wave transmissions.

Inductive shunt circuits have thus far been explored mainly for low-frequency bandgap formation in locally reso- nant piezoelectric metamaterials. Other than the well-studied bandgap phenomenon, the substantial sensitivity of the dispersion curves to variations in the target frequency (i.e. to variations in the inductance value) right below or above the bandgap offers a very rich potential for applications ranging from on-demand spatial tailoring of the refractive index profile to dynamic stiffness modification for leveraging in novel problems of wave propa- gation with spatial and temporal property modulation. As a specific instance, if the unit cells of a metamaterial are shunted to resonate at gradually varying frequencies above the design frequency, one can achieve a smooth variation of both group velocity and phase velocity in space for wavelengths much longer than the lattice size, as a low-frequency electromechanical gradient-index metamaterial. In this work, we explore flexural waves in a one-dimensional piezoelectric metamaterial with unit cells that are shunted to inductive circuits of varying inductance values. Unit cell dispersion characteristics for an infinite metamaterial are studied to demonstrate various phenomena, such as the modification of the phase velocity and the refractive index. Specifically, case studies are given for the formation of a hyperbolic secant refractive index profile to enable plane wave focusing. The effects of dissipation and frequency variation are also studied, revealing that the proposed concepts can enable significant refractive index variation even in the presence of damping (e.g. sufficient for lens design). The advantages of this approach span from low-frequency gradient-index metamaterial design to stiffness modulation beyond the limits of short- and open-circuit values even in the absence of a negative capacitance circuit.

A piezoelectric metamaterial beam is proposed in this paper for both vibration suppression and energy harvesting. Additional springs are introduced to create internal coupling alternately between local resonators. Each resonator is associated with a piezoelectric element for producing electrical energy. First, the mathematical model of the piezoelectric metamaterial beam is developed. The analytical solutions of the transmittance of the system and the open-circuit voltage responses of the piezoelectric elements are derived. As compared to the conventional counterpart without internal coupling, it is found that the energy harvesting performance is significantly reinforced in the low frequency range and the vibration suppression performance is slightly enhanced due to the appearance of an additional band gap. Subsequently, an equivalent finite element model – model A for verifying analytical solutions is developed. The lumped local resonators in the analytical model are modelled by using cantilevers with tip masses in the finite element model. The tip masses are alternately coupled with one-dimensional two-node spring elements. The finite element analysis results show good agreement with the analytical results for both the transmittance of the system and the open-circuit voltage responses of the piezoelectric elements. Finally, a model B with a more practical realization of the internal coupling is established. The coupling spring is replaced by a beam connection. The finite element analysis results show that the behavior of model B is different from model A and is not equivalent to the proposed analytical model. No significant enhancement in terms of energy harvesting is observed but a remarkably enhanced vibration suppression performance appears in model B. The difference between the two models is then discussed.

Locally resonant metamaterials offer bandgap formation for wavelengths much longer than the lattice size, en- abling low-frequency and wideband vibration attenuation. Acoustic/elastic metamaterials made from resonating components usually do not exhibit reconfigurable and adaptive characteristics since the bandgap frequency range (i.e. target frequency and bandwidth combination) is fixed for a given mass ratio and stiffness of the resonators. In this work, we explore locally resonant metamaterials that exploit shape-memory alloy springs in an effort to develop adaptive metamaterials that can exhibit tunable bandgap properties. An analytical model for locally res- onant metastructures (i.e. metamaterials with specific boundary conditions) is combined with a shape-memory spring model of the resonator springs to investigate and exploit the potential of temperature-induced phase transformations and stress-induced hysteretic behavior of the springs. Various case studies are presented for this new class of smart metamaterials and metastructures.

Contactless energy transfer (CET) is a technology that is particularly relevant in applications where wired electrical contact is dangerous or impractical. Furthermore, it would enhance the development, use, and reliability of low-power sensors in applications where changing batteries is not practical or may not be a viable option. One CET method that has recently attracted interest is the ultrasonic acoustic energy transfer, which is based on the reception of acoustic waves at ultrasonic frequencies by a piezoelectric receiver. Patterning and focusing the transmitted acoustic energy in space is one of the challenges for enhancing the power transmission and locally charging sensors or devices. We use a mathematically designed passive metamaterial-based acoustic hologram to selectively power an array of piezoelectric receivers using an unfocused transmitter. The acoustic hologram is employed to create a multifocal pressure pattern in the target plane where the receivers are located inside focal regions. We conduct multiphysics simulations in which a single transmitter is used to power multiple receivers with an arbitrary two-dimensional spatial pattern via wave controlling and manipulation, using the hologram. We show that the multi-focal pressure pattern created by the passive acoustic hologram will enhance the power transmission for most receivers.

A thermally buckled piezoelectric energy harvester is designed to power biomedical devices inside the body. The energy harvester (EN) uses the vibrations inside the body to generate the electricity needed for powering biomedical sensors and devices. The piezoelectric beam consists of a brass substrate and two piezoelectric patches attached to the top and the bottom of the substrate. The bimorph beam is inside a rigid frame. The bimorph beam is buckled due to the difference in the coefficient of the thermal expansion of the beam and the frame.

Inside the body, most of the energy content come from the low-frequency vibrations (less than 50 Hz). Having high natural frequency is a major problem in Microelectromechanical systems (MEMS) energy harvesters. Considering the small size of the EN, 1 ܿ݉cm³, the natural frequency is expected to be high. In our design, the natural frequency is lowered significantly by using a buckled beam. A mass is also used in the middle of the beam to decrease the natural frequency even more. Since the beam is buckled, the design is bistable and nonlinear which increases the output power.

In this paper, the natural frequencies and mode shapes of the EN are analytically derived. The geometric nonlinearities are included in the electromechanical coupled governing equations. The governing equations are solved and it is shown that the device generates sufficient electricity to power biomedical sensors and devices inside the human body.

Piezoelectric patch energy harvesters can be directly integrated to plate-like structures which are widely used in automotive, marine and aerospace applications, to convert vibrational energy to electrical energy. This paper presents two different AC-DC conversion techniques for multiple patch harvesters, namely single rectifier and respective rectifiers. The first case considers all the piezo-patches are connected in parallel to a single rectifier, whereas in the second case, each harvester is respectively rectified and then connected in parallel to a smoothing capacitor and a resistive load. The latter configuration of AC-DC conversion helps to avoid the electrical charge cancellation which is a problem with the multiple harvesters attached to different locations of the host plate surface. Equivalent circuit model of the multiple piezo-patch harvesters is developed in the SPICE software to simulate the electrical response. The system parameters are obtained from the modal analysis solution of the plate. Simulations of the voltage frequency response functions (FRFs) for the standard AC input – AC output case are conducted and validated by experimental data. Finally, for the AC input – DC output case, numerical simulation and experimental results of the power outputs of multiple piezo-patch harvesters with multiple AC-DC converters are obtained for a wide range of resistive loads and compared with the same array of harvesters connected to a single AC-DC converter.

In elastic dielectrics, piezoelectricity is the polarization response to applied mechanical strain, and vice versa. Piezoelectric coupling is controlled by a third-rank tensor and is allowed only in materials that are non-centrosymmetric. Flexoelectricity, however, is the generation of electric polarization by the application of a non-uniform mechanical strain field, i.e. a strain gradient, and is expected to be pronounced at submicron thickness levels, especially at the nanoscale. Flexoelectricity is controlled by a fourth-rank tensor and is therefore allowed in materials of any symmetry. In this work, we explore the effects of varying crosssection and axial strain gradient on bending vibrations on flexoelectric cantilevers. The focus is placed on the development of governing electroelastodynamic flexoelectric equations for a cantilever with varying cross-sectional widths for energy harvesting. The coupled governing equations are analyzed to obtain the frequency response and study the effects of various axial geometry profiles on the electromechanical coupling. The effect of axial strain gradient was also studied and found to be negligible for the geometries and various cross-sections studied here. Varying cross-section profile (with a reduced tip width) yields increased flexoelectric coupling.

Many bio-medical applications entail the problems of spatially manipulating microbubbles by means of high-intensity focused ultrasound (HIFU) pressure field. This paper investigates the nonlinear coupling between radial pulsations, axisymmetric modes of shape oscillations and translational motion of a single spherical gas bubble in water domain when it is subjected to a focused nonlinear acoustic pressure. A multiphysics mathematical model is investigated to obtain nonlinear acoustic field from a focused transducer and to account for bubble oscillations in the resultant HIFU pressure field. The effects of acoustic nonlinearity on the bubble dynamics are examined to determine the instability of the mode shapes of a bubble, which is contributing to form the translational instability, known as dancing motion. Furthermore, acoustic streaming effects caused by radial pulsations of a microbubble in the surrounding water domain are reported.

While the vast majority of the literature in energy harvesting is dedicated to resonant harvesters, non-resonant harvesters, especially those that use turbulence-induced vibration to generate energy, have not been studied in as much detail. This is especially true for grid-generated turbulence. In this paper, the interaction of two side-by-side fluidic harvesters from a passive fractal grid-generated turbulent flow is considered. The fractal grid has been shown to significantly increase the turbulence generated in the flow which is the source of the vibration of the piezoelectric beams. In this experimental study, the influence of four parameters has been investigated: Beam lengths and configurations, mean flow velocity, distance from the grid and gap between the two beams. Experimental results show that the piezoelectric harvesters in fractal grid turbulence are capable of producing at least the same amount of power as those placed in passive rectangular grids with a larger pressure loss, allowing for a potentially significant increase in the efficiency of the energy conversion process, even though more experiments are required to study the behavior of the beams in homogeneous, fractal grid-generated turbulence.

In this paper, we present our study on a piezoelectric gas controller based on dual-bimorph piezoelectric valve [1]. The bimorph structure was designed to be a one-dimensional plate to reduce the overall size of the piezoelectric actuator. A rod was placed at the center of a pair of piezoelectric bimorphs, and the piezoelectric valve was slightly compressed to create a pre-stressed condition. These two piezoelectric bimorphs were synchronized to push the cylinder valve to initiate valving process. The performances of this system were studied and evaluated, including frequency response, pressure drop, and flow rate. The piezoelectric actuator was fabricated by attaching two 5 mm wide, 50 mm length and 0.4mm thick bimorph PZT together. The poling direction of the two PZT layers was in opposite direction to create a serial bimorph. PMMA cylinder were created by using a CO₂ laser cutter. The level of the valving movement was studied under a different driving voltage and operating frequency. Preliminary finding showed that a 0.103mm displacement at 1 Hz can be achieved and the developed piezoelectric valve can be used to control output pressure.

Ultrasound acoustic energy transfer systems are receiving growing attention in the area of contactless energy transfer for its advantages over other approaches, such as inductive coupling method. To date, most research on this approach has been on modeling and proof-of-concept experiments in the linear regime where nonlinear effects associated with high excitation levels are not significant. We present an acoustic-electroelastic model of a piezoelectric receiver in water by considering its nonlinear constitutive relations. The theory is based on ideal spherical sound wave propagation in conjunction with the electroelastic distributed-parameter governing equations for the receiver’s vibration and the electrical circuit.

An inerter is a mechanical analogue to a capacitor, where the force across the device is proportional to relative, rather than absolute, acceleration. This concept can offer attractive performance in a wide variety of engineering vibration problems, because the engineer can tune the device without dramatically increasing the physical mass of the structure. Consequently, there have been many studies over the last two decades that have explored their application to bridge vibrations, seismic isolation of tall buildings, vehicle suspensions, and other engineering problems. Several configurations of inerter systems have been proposed, typically involving the inerter in a vibration absorber, or by using the inerter as part of an isolation system. However, to date there have been limited studies that have explored the combination of inerters with semi-active devices such as magnetorheological fluid dampers. Furthermore, because one manifestation of inerters involves the use of hydraulic fluid, it is possible for magnetorheological effects to be integrated into the inerter itself. The present study investigates the feasibility of this approach for practical scenarios. A quasi-static model is developed, combining an existing model of a fluid inerter with simplified models for magnetorheological fluids. The trade-off between damping performance and inerter performance is explored. The model is then used in a case study, where its potential use in a control strategy known as a parallel-layout inerter damper is investigated.

We perform a theoretical simulation to investigate how the magnetic field induces the interaction of ferromagnetic particles inside MRE, and consequently how the surface microstructures of MRE are changed. Firstly, we propose a mesoscopic model of the MRE by assuming that particles have the same radius, and they are randomly distributed in the matrix. Both particles and matrix are considered as linear elastic materials. We apply Monte-Carlo method to produce the initial surface microstructure of the MRE before considering the magnetic field effect. Further, we use sequential decoupling FEM method to solve the magneto-mechanical coupling problem. The relationships of surface roughness of MREs with the volume fraction of ferromagnetic particles, the magnetic field strength, the initial surface microstructure, and the matrix modulus have been numerically investigated.

Airplane landing gears are subjected to a wide range of excitation conditions due to variations in sink speed and road condition. An existing passive type damper for the landing gear is hard to satisfy these various conditions. A semi-active type magnetorheological (MR) damper is one of attractive solutions to resolve this problem. This work presents design and analysis of MR damper applicable to the landing gear system. MR damper is designed based on the required damping force and packaging constraints. Especially, the geometry of the magnetic core is optimized in terms of magnetic intensity at magnetic poles to achieve uniform magnetic intensity under the packaging constraints. The effectiveness of the proposed MR damper is given by presenting the field-dependent damping force and the efficiency.

Dynamic performance of a compressible magnetorheological fluid (CMRF) damper with an asymmetric damping performance was examined. Due to the 400°F operational environment , a high-temperature silicone damping fluid was utilized as the base of the CMRF. The CMRF damper valve was designed and optimized using two-dimensional axisymmetric electromagnetic finite element analysis. A secondary piston that incorporates check valves was attached to the CMRF valve, which provides the asymmetry under jounce and rebound. The CMRF damper utilizes a twin tube structure, whereas the space between the inner and outer tubes was used as a high-pressure accumulator for operation at elevated temperatures. Up to a certain temperature, the designed CMRF damper acts as a liquid spring, whereas after certain in-chamber pressure is exceeded, the CMRF damper behaves as a conventional damper. Dynamic characterization of the CMRF damper was performed under sinusoidal excitation for velocities up to 1.27 m/s (50 in/s). This study also examined the CMRF damper under several different environmental conditions including, humidity, salt fog, extreme temperatures and sand exposure. It was demonstrated that the CMRF damper can provide asymmetric and controllable rebound and compression forces. It was also shown that the selected components such as CMRF base fluid, seals and electromagnet wires can withstand the several different operating conditions.

Haptic feedback is desired for numerous applications including simulators, teleoperations, entertainment and more. While many devices today feature vibrotactile feedback, most do not provide kinesthetic feedback. To address the need for both vibrotactile and kinesthetic feedback, this study investigates the use of electrorheological (ER) fluids for their tunable viscosity under electrical stimulation. A prototype device containing ER fluid was designed and fabricated. The device operates based on pressure-driven flow of the fluid between charged plates due to user interaction with the touch contact surface. The prototype was tested using a dynamic mechanical analyzer to measure the actuator’s resistive force with respect to indentation depth for a range of applied voltages and frequencies. The results indicate that increasing the applied voltage causes an increase in the force produced by the actuator. Varying the supplied signal over a range of voltages and frequencies can convey a range of force and vibrational feedback. This range is sufficient to transmit distinct haptic sensations to human operators and demonstrates the design’s capability to transmit remote or virtual touch feedback conditions.

Traditional electric motors rapidly lose power density as their size decreases. Motors on the order of 1 cubic micron , roughly the size of a red blood cell, have nearly six orders of magnitude smaller power densities than cubic millimeter sized motors. Strain-mediated multiferroic motors have recently been predicted to be energy efficient and power dense at the micron scale. These motors leverage magnetoelastic anisotropy to control the magnetic moments of small nanodiscs or domain walls, and use dipolar forces to couple rotors or beads to the stray magnetic field. While deterministic control methods have already been proposed, a variety of device designs and motor concepts abound. This presentation will explore the relative merits of two key linear motor designs; one using individual magnetic nano-islands, and another focusing on propagating Bloch-type domain wall motion in structures analogous to magnetic ‘racetrack’ memory. A combination of Stoner-Wohlfarth magnetic macrospin modeling and numerical FEA simulations fully coupling micromagnetics and elastodynamics will be presented and analyzed. Results demonstrate the racetrack design is capable of applying larger forces to dipole coupled magnetic beads, but that the use of nano-islands may be capable of achieving higher linear velocities due to domain wall speed limits in the racetrack design.

There has been considerable research on the design of vibration based energy harvesters in the last decade exploring the potential of autonomous power supply for miniaturized electronic systems. Nonlinear energy harvesting mechanisms are in general perceived as more robust than linear harvester designs owing to the broadband resonance dynamics which allow for efficient energy transduction over a diverse range of input vibrations. In particular, geometrically bi-stable composites with embedded piezoelectric elements have been investigated as a scalable and bio-compatible design with a strong potential for harvesting energy from the high-amplitude interwell oscillations encompassing both the statically stable states of the harvester. Significant research effort has been devoted to devise efficient strategies for shifting between the co-existing stable solution configurations of bi-stable harvesters, thus allowing to consistently maintain the high-amplitude inter-well oscillations favorable for energy harvesting. However, analysis of the compatibility of conventional linear mode shape based harvester designs to harness the complete potential for energy harvesting from nonlinear solution configurations of bistable harvesters has received lesser attention. This study presents an experimental analysis of the operational deformation shapes associated with the intra-well and inter-well response regimes of bi-stable energy harvesters. A qualitative comparison of the operational deformation shapes characterizing the nonlinear response of the harvester with the linear design mode shapes is presented. The results indicate that operational deformation shapes differing significantly from the linear mode shapes are active in the nonlinear response regime of the harvester. The aforementioned deformation shapes, while influencing the mechanical response of the harvester, may not result in any significant contribution to the harvested power as they are essentially excluded in the linear mode shape based harvester design envelop. The presented experimental results essentially highlight the need for considering the operational deformation shapes associated with the nonlinear response regime while designing for the dimensions and the position of the piezoelectric elements on bi-stable composites to ensure that the complete potential for energy conversion across all of the dynamical regimes is harnessed adequately.

Total knee arthroplasty, as one of the most common surgeries in the United States, has been widely used to help restore the functionality of damaged knee joints. Alignment of the knee joint during surgery is an extremely important factor to achieve a successful operation. Several methods have been used to quantify the alignment and to provide surgeons with a repeatable method of surgery. However, lack of in vivo information has hindered establishment of correlation between intra- and postoperative knee conditions. In this work, the application of multiple piezoelectric transducers encapsulated inside the ultra high molecular weight polyethylene knee bearing for collecting in vivo data is suggested. The piezoelectric elements display the ability to sense and harvest energy from the joint during daily activity. As a sensor, piezoelectric transducers are designed to measure the compartmental forces as well as the location of the contact points between the femoral and tibial components of the knee implant. Initially, finite element analysis is performed to investigate the sensing performance of the system. In addition, a prototype instrumented bearing is fabricated and the performance of the system in measuring the forces and locations is investigated experimentally. In the experiments, the voltage signals generated by the piezoelectrics are obtained and processed to measure two components of force as well as two different contact points, one each on the medial and lateral compartments of the knee bearing. On the other hand, the actual force profile and the location of contact areas are recorded using the load frame’s built in load cell, and pressure-sensitive films, respectively, and compared to the measured data from the piezoelectrics. The result of FE simulation showed a maximum error of about 1.5% in force sensing and a maximum deviation of about 0.5 mm in the measured location of the contact points. The experimental results also showed that the measured force and location by the piezoelectric sensors match the actual quantities measured from load frame and pressure film fairly well.

An ultrasonic clothes dryer was developed by researchers at Oak Ridge National Laboratory based on a novel approach of using high-frequency mechanical vibration instead of heat to extract moisture as a cold mist. This technology is based on direct mechanical coupling between mesh piezoelectric (PZT) transducers and wet fabric. The vibration introduces sufficient momentum to the droplets trapped in the fabric pores to atomize them and leave the garment in a cold state. In the vibrating transducer, deformation followed by the effects of boundary layer acoustic streaming results in ejection of the atomized droplets. The research presented bridges the vibration of a PZT mesh transducer to the induced acoustic field and to capillary-wave theory. Mathematical modeling studies free and forced vibrations of a mesh-like PZT structure, using the structural parameters identified by actuation testing in several case studies. Computational fluid–structure interaction modeling is performed to couple the vibrations of a PZT transducer with an in-contact droplet. The results obtained are used to investigate (1) the transverse deformation of the vibrating mesh transducer in contact with a droplet, (2) the resultant boundary layer acoustic streaming in the fluid surrounding the vibrating surface, and (3) the droplet deformation and fluid ejection. The physics of atomization are linked to the level of the near-wall droplet vibrations induced by the surface deformation of the transducer. Then the surface deformation is linked to the properties of the PZT mesh transducer and input actuation frequency and power.

The recent radio frequency communication system developments are generating the need for creating space antennas with lightweight and high precision. The carbon fiber reinforced composite (CFRC) materials have been used to manufacture the high precision reflector. The wave-front errors caused by fabrication and on-orbit distortion are inevitable. The adaptive CFRC reflector has received much attention to do the wave-front error correction. Due to uneven stress distribution that is introduced by actuation force and fabrication, the high order wave-front errors such as print-through error is found on the reflector surface. However, the adaptive CFRC reflector with PZT actuators basically has no control authority over the high order wave-front errors. A new design architecture assembled secondary ribs at the weak triangular surfaces is presented in this paper. The virtual experimental study of the new adaptive CFRC reflector has conducted. The controllability of the original adaptive CFRC reflector and the new adaptive CFRC reflector with secondary ribs are investigated. The virtual experimental investigation shows that the new adaptive CFRC reflector is feasible and efficient to diminish the high order wave-front error.

This paper presents the results of experimental tests of a new proof mass actuator that can be used to implement a velocity feedback loop to reduce the flexural vibration of large flexible structures. Classical proof mass actuators used in vibration control systems require low fundamental resonance frequency to produce a constant force effect at the control position in the desired frequency range. The actuator considered in this study uses a piezoelectric stack transducer, which is characterised by large force and small stroke properties. Thus, to meet the requirement of low resonance frequency, the actuator should be equipped with a large proof mass. However, in this case when the actuator is exposed to shocks the piezoelectric transducer undergoes large deformations, which may lead to cracks. Also, the bulky proof mass limits the range of applications in which the actuator can be used. The actuator presented in this paper includes an additional flywheel element that produces an apparent mass effect without increasing the proof mass. As a result, the fundamental resonance frequency of the actuator is lowered without increasing the total weight of the suspended mass. This leads to both a more robust feedback loop with higher vibration control performance and a more robust actuator to shocks and large disturbances. The paper presents the measured frequency responses functions that characterise the electro-mechanical response of the proposed flywheel piezoelectric actuator, which are contrasted with simulations obtained from a simplified lumped parameter model.

In this paper, a novel torsional resonator is proposed to measure the viscosity of fluids. The proposed measurement system is based on the torsional mode vibration of a metallic cylindrical tube bonded with specially designed twisting-motion-d33-piezo actuators. Two piezoelectric patches are bonded nearer to the fixed end of the cylindrical tube. The one bonded on the upper semicircle of the cylindrical tube is used as a twisting actuator and the other on the bottom semicircle is used as a sensor. The entire system is maintained at its torsional mode resonance frequency by using simple closed loop resonator electronics connected between the two piezo patches. The free end of the resonating cylindrical tube is half immersed into a viscous medium of which the viscosity is intended to be measured in this proposed paper. The torsional resonator experiences an additional viscous drag force-Fd due to the viscosity of the fluid medium which alters its torsional mode resonance frequency (ωT). The value of drag force Fd acting on the torsional resonator will vary depending on the type of viscous fluids in use. The closed loop resonant circuit tracks the change in torsional resonance frequency due to Fd and vibrates the tube with the new resonance frequency whenever the force generated by the viscous fluid changes. The shift in torsional resonant frequency is related to the viscosity of the fluid medium. The analytical model of the vibrating cylindrical tube with viscous fluid is derived and the results are validated with numerical simulation and experimentation. The key enabling concept of this proposed paper is the benefit of torsional mode resonator over the flexural mode resonator i.e., the torsional mode resonator experiences much less viscous damping at its resonance frequency. For the real-time laboratory experimentation, the hollow cylindrical tube with 30cm length and 2.5cm diameter is used. For the actuation and sensing, the MFC M-8528-F1 type (450 fiber orientation) d33 twisting actuator is used. The torsional resonance frequency of the tube in air is 2.5KHz. The proposed fluid viscosity measurement concept is novel and it is found to have better sensitivity and linearity than the flexural mode viscosity measurement system.

In this paper a piezoelectric energy harvester for scavenging wasted vibration energy inside a vehicle tire is designed and its performance is experimentally verified. Piezoelectric type energy harvesters can be used to collect vibrational energy and power such systems, but they need to be carefully designed to address power generation and durability performances. In this study, we address a reliability based design optimization (RBDO) approach to design the harvester that considers the uncertainty in dimensional tolerances and material properties, to be compared to the traditional deterministic design optimization (DDO). Both designs are manufactured for the experimental evaluation to demonstrate the merits of RBDO design over DDO.

Breathing produces chest motion 24 hours a day, hence it is ideal for continuous energy harvesting of up to milliwatt scale power levels. A soft band wrapped around the chest can extend by centimeters at relatively low force levels. A stiff band extends at higher force levels but with some discomfort to the user. Chest strain energy harvesters must balance power generation and the soft tissue compression associated with user discomfort. This paper explores the modeling and analysis of wearable chest strain energy harvesters that use electromagnetic generators and piezoelectric polymers including the effects of soft tissue compliance. Electromagnetic generators are shown to produce more power than piezoelectric polymers during deep breathing. During shallow breathing, however, the polymer harvester performs better because static friction and soft tissue compression limit power generation in the electromagnetic harvester.

This paper performs a design parameter study for development of a self-powering brain neurostimulation system by harvesting deformation energy generated from mandibular (lower jaw) movements. For decades, scientists recognized that electrical stimulation of the brain (deep brain stimulation, DBS) has the potential to treat a variety of refractory medical conditions including chronic pain, Parkinson’s disease, movement disorders, major depression and epilepsy. A commercial DBS device comprise a stimulation lead, neurostimulation unit with microcontroller, and a battery for power supply. The batteries in DBS need replacement every 3~5 years and thus problematic because additional surgery is required to replace them. This paper describes an innovative technology to power DBS by converting stresses/strains in the mandible caused by jaw movements into electrical energy using piezoelectricity. The proposed energy harvester has a multilayer layout composed of piezoelectric composite and biocompatible titanium layers, and will be secured in place on the body of the mandible using titanium screws. For optimal design of this harvester, we build an experimentally verified FEM model for the mandible and harvester assembly, and perform parameter study of the energy harvester. The parameter study on the size/location of the piezoelectric material as well as its cross sectional properties of piezoelectric harvester is performed and experimentally tested. Its practical use by integrating it with electrical circuit is also discussed.

A wireless structure health monitoring (SHM) system for wind turbine blades has been actively researched to realize its low cost and efficient maintenance. A sustainable power supply to the wireless SHM system installed in a rotating blade has been one of the most challenging issue. Vibration energy harvesting via piezoelectricity or electromagnetism can provide a solution, but varied blade rotation and the corresponding random natured vibration make it difficult to design a practical harvester. In this paper, an impact-driven piezoelectric energy harvester (PEH) is proposed to efficiently generate an electric power at PEH’s natural frequency for any rotation speed of blades. This harvester can be installed within the blade to power the wireless SHM system sustainably. The impact-driven PEH consists of a piezoelectric cantilever beam and a gravity-induced rotator. When the wind turbine blade rotates, the orientation of the cantilever changes but the orientation of the gravity-induced rotator remains fixed to a global coordinate system (defined on the earth). At every rotation cycle, the gravity-induced rotator strikes the cantilever tip, which causes vibration. Then, the piezoelectric cantilever beam generates electric power at PEH’s natural frequency. A testing setup for the proposed PEH is built, by installing the PEH prototype on the blades driven by a DC motor. Experimental result shows that the proposed PEH generates electric power at PEH’s natural frequency for any rotation speed, and average power generated from the proposed PEH is 1.56 mW at the typical blade’s rotation speed of 20 RPM.

Lifejacket is an indispensable life-saving equipment for ships and airplanes. Traditional lifejacket is designed to prevent human from drowning. However, the water temperature is usually low, especially in winter, which significantly reduces the human body temperature and leads to death. Meanwhile, power is critical for drowning people to use emergency communication equipment. This paper proposed an ocean wave powered lifejacket using 2DOF floating boards to provide both buoyance and electricity for drowning people. Hence, they can use this continuous electric power to keep key body warm and send distress signal. This lifejacket is featured with two 2DOF floating boards and the mechanical motion rectifier (MMR) can convert the 2-DOF motions to the unidirectional rotation of generator. The design principle is illustrated and the dynamic modelling for the 2-DOF motions has been analyzed. Bench test and lake test have been conducted to validate the design concept.

During trips and outdoor adventures, there are a lot of electric equipment and thus power supply for those devices is critical. At the same time, the burden on shoulders from heavy baggage is substantial. This paper presents a one-way energy harvesting backpack with ball-screw mechanism to generate electricity with high efficiency and reliability, while relieves the burden on shoulders. The one-way energy harvesting method only harvests negative work from human body and potentially reduce metabolic cost while carrying backpack. Simulations show that 4.5W of electrical energy can be obtained from human walking. Bench test results indicate this system can obtain an average power of 7.3 W with excitation of 2Hz and 25mm direct drive. Treadmill test to verify the performance of burden relieve on shoulders indicates this one-way design combing with elastic support strap can reduce the force on shoulders, which reduce fatigue in human.

Bridge cables should always be equipped with vibration mitigation measures and monitoring techniques. The proposed electromagnetic damper was developed to reduce vibration of the cable and utilize induction current as the power source of the wireless sensor. Major parameters for the design of the damper were derived. Then, the cable experiment was carried out under the conditions of free vibration and force vibration. For free vibration conditions, the change of damping ratio according to the acceleration amplitude evaluation point was analyzed through Hilbert transform. As a result, the damping performance of the passive electronic damper applying the external resistance under the free vibration condition was improved to 2.18% of the maximum damping ratio and 1.88% of the average damping ratio. Under the sinusoidal forced vibration conditions, it was found that the acceleration and frequency domain response at each measurement point of the cable decreased by 30% to 50% or more, and the RMS displacement response decreased by 45% to 49% under the excitation with 1st to 3rd natural frequencies. In addition, it has been confirmed that effective damping performance is exhibited in the 2nd and 3rd natural frequency, which are the main response conditions of the cable. Hybrid simulation was carried out to evaluate the energy harvesting performance of the electromagnetic damper. As a result, the output power was 174.6mWh at the mean wind speed of 5.4 m/s. Even if the sensor and the battery loss were considered, enough power was generated to operate the wireless sensor.

Reducing vibration of high-rise structures under earthquake load has been the subject of considerable efforts in Japan. Relevant researches about vibration energy dissipation devices for buildings have been undertaken. An active mass damper is one of the well-known vibration control devices. Despite the accumulation of much knowledge of control design methods for the system, application of the devices to high-rise structures under earthquake load is challenging, because the active mass dampers have one serious disadvantage about stroke limitation of the auxiliary mass. In this study, we have proposed a new control system, which had a neural oscillator and position controller, to solve this problem. The main role of this neural oscillator included in newly proposed system is picking up the phase information of the eigen-frequency component of a target structure, then the auxiliary mass of an active mass damper is excited by reference to the oscillator’s signal. We can easily regulate the stroke of the active mass damper no matter how large the target structure swings, because the control signal for the auxiliary mass of the phase and amplitude information of the active mass damper are separately processed. However, there is no general determination method for the desired stroke of the auxiliary mass from the oscillator’s signal. The previous method determined the desired stroke of the auxiliary mass using two state quantities of the oscillator, which depends on types of oscillators and has non-linearity and instability. Thus, this study proposes a generation method for the desired stroke of the auxiliary mass by using synchronous detection. From the results of numerical simulation, the presenting method can apply to any types of oscillators and generate the linear and stable signal by reference to an oscillators’ signal, and was effective for improving the control performance.

Piezoelectric materials have been investigated for vibration control in various engineering applications. Passive and active control techniques using piezoelectric materials are among the most important ones in the literature of vibration control. However, passive techniques present a good performance over a narrow frequency bandwidth. On the other hand, although active techniques require external power sources, sensor and actuators, they usually provide a good control performance over a wider range of frequency. To overcome the drawbacks of passive and active techniques, authors have focused on the nonlinear treatment of voltage output of the piezoelectric materials. A particular nonlinear technique, named Synchronized Switch Stiffness Control (SSSC), changes the stiffness of the structure through softening or hardening nonlinearities. The motivation is to ensure that the structure is excited out of its resonance frequency, preventing large displacements. The use of the SSSC technique has already been reported in the literature. However, few works show a circuitry that reproduces the SSSC technique. Furthermore, reported SSSC topologies allow only a hardening or softening effects. This work presents a novel adaptive SSSC piezoelectric circuit that combines the hardening and softening effects, significantly reducing mechanical amplitudes over a wide range of frequencies. The proposed SSSC circuit uses two piezoceramic patches (one as sensor and one as the stiffness actuator) and two symmetrical voltage sources. In the final version of the paper, experimental verifications of numerical predictions will be provided.

Coupling beam is a very important component in shear wall structure. However, the reinforced concrete coupling beam does not have an efficient energy dissipation capacity and a stable hysteretic behavior. A new type energy-dissipating coupling beam is proposed in the paper, which has a large energy dissipation capacity and a stable hysteretic behavior. It can be constructed and repaired easily. Models with different shapes were established in a Finite Element Analysis program to simulate the performance of the damper. The hysteretic behaviors of the damper were also numerical analyzed.

In this paper, we present some innovative and general strategies for the control of benches and platforms, that the introduction of the new class of monolithic UNISA Folded Pendulum is now making it possible, also in terms of environmental conditions, like ultra-high-vacuum (UHV), cryogenics and harsh environments. In particular, we present and discuss a parametric analysis of the control models in connection with the sensors limitations in terms of sensitivity and band. Finally, we present and discuss some experimental laboratory tests on a laboratory platform, underlining the present advantages and the expected future improvements.

Nowadays, the energy harvesting has attracted considerable interest of international researchers from many disciplines, due to the promising application around the industrial area. The energy harvesting technology is very important because it can extract electrical energy from ambient environment for supplying power to wireless monitoring nodes. Although much work has been done for extracting energy from vibration motions, there are few successful applications for the rotational motions. Also, those energy harvesters for rotational motion will be incapable for realistic applications when the priori knowledge of monitoring objectives is absent. This paper proposes a novel electromagnetic energy harvester for the online bearing health condition monitoring. The circular Halbach array is introduced to the arrangement of permanent magnets, which can achieve frequency-up conversion and enhance the magnetic field. In order to optimize output power performance, the theoretical magnetic field model to analyze the magnetic coupling is established. The proposed dynamic model can predict voltage response and output power. The numerical and experimental results show that the output power and power density can be improved for condition monitoring.

The paper investigates the opportunity of exploiting self-sensing properties of carbon nanotubes to generate a feedback signal, representative of the vibratory state of the structure, to actively suppress vibrations. Due to the so called “tunneling effect”, carbon nanotubes (CNT) embedded in the matrix of a composite structure realize a distributed sensor. This means there is a no more a sensor, but, in fact, it is the same structure that is able to provide information on its state on vibration. The paper demonstrates it is possible to exploit electrical signal related to the deformation of the structures to estimate vibration and to design suitable control forces to suppress them.

This paper proposes a compact electromechanical modeling of multi-electrode piezoelectric transformer. This modeling can be applied to the study of standing or traveling flexural wave in piezoelectric systems and especially for ring type piezoelectric transformers. This modelling is based on the Euler-Bernoulli beam theory and from this theory and piezoelectric equations, transfer matrixes linking stresses, velocities and voltages for a beam are determined. In piezoelectric systems with no mechanical boundary in the propagation direction of the wave, for example a ring, an admittance matrix is obtained from the modeling linking all the currents and voltages. This modelling allows moreover the representation and electrical simulation of a piezoelectric element subjected to a traveling wave.

Existing smart composite piezoelectric beam models in the literature mostly ignore the electro-magnetic interactions and adopt the linear elasticity theory. However, these interactions substantially change the controllability and stabilizability at the high frequencies, and linear models fail to represent and predict the governing dynamics since mechanical nonlinearities are pronounced in certain applications. In this paper, first, a consistent variational approach is used by considering nonlinear elasticity theory to derive equations of motion for single-layer piezoelectric beams with and without the electromagnetic interactions (fully dynamic and electrostatic). This modeling strategy is extended for the three-layer piezoelectric smart composite by adopting the widely-accepted sandwich beam theories. For both single and three-layer models, the resulting infinite dimensional equations of motion can be formulated in the state-space form. It is observed that the fully dynamic nonlinear models are unbounded boundary control systems (same in linear theory) y(t) = (A + N)y(t) + Bu(t), the electrostatic nonlinear models are unbounded bilinear control systems y(t) = (A + N)y(t) + (B₁ + B₂y)u(t) in sharp contrast to the linear theory. Finally, we propose B*−type feedback controllers to stabilize the single piezoelectric beam models. The filtered semi-discrete Finite Difference approximation is adopted to illustrate the findings.

It has been reported that using the method of one-frequency-two-mode to drive a piezoelectric linear motor, the nature resonant effect induced by the finite boundaries can be eliminated. The structure of the piezoelectric linear motor is based on placing two piezoelectric actuators on a one-dimensional finite plate. This method uses a single driving frequency at the middle of two adjacent bending modes to drive these two piezoelectric actuators with a 90° phase difference, and a traveling wave can be generated. However, due to the driving frequency was not directly at the resonant frequency, the efficiency and traveling distance cannot be very efficient. Based on our previous studies, it shows that the driving voltage and velocity of displacement has a linear relationship, and the size and location of actuators can also influence the distance of generated traveling waves. In this paper, we report our study on using another method of two-frequency-two-mode that used two adjacent bending modes to generate traveling waves. Since the operating frequencies of the two actuators are at resonant frequencies, the efficiency can be very high. Our studied showed that the difference between native electrical impedance and mechanical impedance of the two adjacent resonant modes, the performance of the induced traveling waves can be varied significantly. Furthermore, the total distance and profile of the traveling waves can also be different. To understand this mechanism, we study the influence of the two driving frequencies with different amplitude and phase differences. Thus, the energy that falls into the two adjacent modes can be changed, and the ratio of vibrating amplitudes of these two modes can be adjusted. We demonstrate that the total traveling distance can be much enhanced by controlling the driving amplitude and phase difference between two actuators.

This paper describes the finite element modeling and experimental testing of a magnetic T-shaped piezoelectric energy harvester that activates the internal resonance phenomena to increase voltage output and frequency bandwidth. The harvester consists of two magnets and two coupled beams, a cantilever piezoelectric beam attached to a clamped-clamped beam. A finite-element model is used to obtain the global mode shapes and natural frequencies of the system. We controlled the distance between the two magnets to achieve a nonlinear phenomenon of internal resonance of the structure, where the 2:1 ratio is satisfied between the modal natural frequencies. The T-shaped structure is combined with the magnetic nonlinearity such that a large, distinct internal resonance can occur at much lower excitation levels compared to a T-shaped structure without magnetic nonlinearity. Presented experimental results validate the benefits of the T-shaped structure nonlinearity when combined with a magnetic nonlinearity to achieve higher bandwidth and large responses, which can improve the energy conversion efficiency of the vibration energy harvester.

Shape memory alloys (SMAs) are unique materials with the ability to generate and recover moderate to large inelastic deformations. Due to their aforementioned ability, SMAs are suitable for applications in aerospace, oil and gas and automotive industries, where compact actuators with high actuation energy density are required. The current work presents a modeling framework that links the heat treatment of SMAs with their effective response and aims to accelerate the discovery of new high temperature SMAs with optimal performance. Thus a finite element based, multi-field micromechanical framework is developed to capture the constitutive response of precipitation hardened Ni-Ti-Hf SMAs. A representative volume element of precipitated polycrystalline SMAs is considered which contains randomly distributed non-overlapping precipitates, while periodic boundary and geometric conditions are maintained. The SMA matrix is assumed to behave isotropic as a result of random texture while the precipitates are considered as linear elastic solids. The effect of the lattice mismatch between the precipitates and the matrix, and the effect of the Ni and Hf depletion during precipitation on the thermo-mechanical response of the material are taken into consideration. The Fickian diffusion law is used to predict the Ni and Hf concentration field in the vicinity of the precipitates, which results in substantial SMA transformation temperature shifts. Finally, the predictive capability of the developed framework is assessed through correlations with experimental results.

Advancements in controlled drug delivery (CDD) technology still face major challenges in practice, including chemical issues with synthesizing biocompatible drug containers, releasing the pharmaceutical compounds at the targeted location in a controlled time rate and using an effective and safe trigger for initiating the drug release. This work aims to overcome these challenges with employing biodegradable shape memory polymer (SMP) based drug-delivery containers. Besides biological safety, biodegradability ensures that no further surgery will be needed for the removal of the containers. Focused ultrasound (FU) is used as a trigger for noninvasively stimulating SMP-based drug capsules. FU has a superior capability to localize the heating effect, thus initiating a controlled shape recovery process only in selected parts of the polymer, which affects the amount of drug released. The current research uses a mathematical multiphysics model which performs an acoustic-thermoelastic analysis, to optimize the design of SMP containers. The proposed designs exploit various parameters such as nonlinearity, absorption and diffraction effects, as well as input power and frequency of the propagating acoustic wave to attain the desired shape recovery, as required by the application or location of drug release. The acoustic-thermoelastic effects on the SMP containers are studied with the help of finiteelement methods. Multilayer simulations are performed at millimeter scale to mimic the in vivo conditions of a drug delivery container travelling inside an artery. By manipulating the design and the shape recovery rate of the SMP containers, velocity of the drug particles is controlled and directed towards a specific location.

Long-distance crewed space exploration will require advanced thermal control systems (TCS) with the ability to handle a wide range of thermal loads. The ability of a TCS to adapt to the thermal environment is described by the turndown ratio. Developing radiators with high turndown ratios is critical for improving TCS technology. This paper describes a novel morphing radiator designed to achieve a high turndown ratio by varying its own radiative view factor and effective emissivity through the use of shape memory alloys (SMAs).

This radiator features two SMA torque tubes cantilevered to a rigid fixture. The working fluid is transported within the SMA tubes through an annular flow system. In a cold environment, radiator panels fixed to the free ends of the tubes are oriented vertically in a parallel-plate fashion, where the high-emissivity interior faces have restricted views to the environment and heat rejection is minimized. When the system heats up, the tubes actuate by twisting in opposing directions, bringing the panels to a horizontal position with the interior faces exposed to maximize heat rejection. When the system cools down, the tubes twist in reverse, restoring the panels to the vertical orientation where heat rejection is again minimized. This variable heat rejection system has the potential for achieving higher turndown ratios than those of current state-of-the-art systems. A benchtop prototype has been designed and tested to demonstrate actuation and to explore internal heat transfer effects. Prototype design, testing, and results are herein described.

This paper presents a bio-inspired continuously adapting architectural element, to enable a smart canopy that provides shade to buildings that need protection from sunlight. The smart actuator consists of two elements: one NiTi shape memory (SME) spring and one NiTi superelastic (SE) wire. The SE wire is deformed to a ‘U’ shape and then the SME spring is attached to it. Due to the force of SE wire exerted on SME spring, the smart canopy is in its open position. When the environment’s temperature increases, the actuator activates and shrinks the SME spring and hence it closes the canopy. In continues, when the temperature decreases at evening, the actuator inactive and SE wire will open the smart fabric. This unique activation provides different advantages like silent actuation, maintenance free, eco-friendly, and no or low energy consumption. Here, the conceptual design of the smart canopy actuator will be discussed. Then, a simulation study, using finite element method, is used to investigate components’ behavior. The extracted material parameters are implemented in the subroutine, to simulate the behavior of the shape memory alloy elements. Simulation’s results predict superelastic behavior for the SE wire and shape memory effect for the NiTi spring. For further studies, a prototype will be fabricated to confirm simulation’s results, as well as performing some experimental tests.

In this research, by combining the concept of elastic metasurfaces with piezoelectric transducer with shunted circuitry, we investigate the designs of elastic metasurfaces, consisting of an array of piezoelectric transducers shunted with negative capacitance, which is capable of modulating wave fronts adaptively. In order to construct different adaptive elastic metasurfaces, different phase profiles along the interface can be framed through properly adjusting the negative capacitance values. Flat planar lenses for focusing transmitted A0 Lamb waves are achieved, and possess the flexibility of changing focal locations through electromechanical tunings. Additionally, nonparaxial self-bending beams with arbitrary trajectories and source illusion devices can also be accomplished owing to the free manipulation of phase shifts. With their versatility and tunability, the adaptive elastic metasurfaces could pave new avenues to a wide variety of potential applications, such as nondestructive testing, ultrasound imaging, and caustic engineering.

Acoustic metamaterials have attractive potential in elastic wave attenuation and wave guiding over specific frequency ranges. In this research, we apply acoustic metamaterial into the manipulation of stationary wave in a finite beam, i.e., tailoring vibration modes of the structure. Rather than geometrical modification, we demonstrate that vibration modes can be adjusted by combing the resonance and bandgap characteristics of piezoelectric metamaterial. For instance, it’s shown that new vibration modes can be created while the region with excitation applied has minimum displacement. Furthermore, it’s illustrated that resonance region of the metamaterial beam can be arbitrarily assigned due to the adaptiveness of the piezoelectric metamaterial beam. The analytical investigations are confirmed with finite element simulations.

Spatiotemporal periodic structures are systems whose properties are periodically modulated both in space and time, able to support waves only in one direction, so breaking the so called reciprocity principle. Studies till now focused mainly on continuous systems, where properties are modulated in a continuous manner both in space and time. However, this is not the case of real mechanical systems: if on the one hand it is possible to think of a continuous temporal modulation by the means of an actively controlled smart material, on the other hand it is really hard to imagine a system that can be controlled punctually in space. For this reason discretely modulated structures are studied in this work, putting in evidence the differences with the continuous ones and providing some basis for the actual design of such a system.

In this manuscript, we envision deployable structures (such as solar arrays) and origami-inspired foldable structures as metamaterials capable of tunable wave manipulation. Specifically, we present a metamaterial whose bandgaps can be modulated by changing the fold angle of adjacent panels. The repeating unit cell of the structure consists of a beam (representing a panel) and a torsional spring (representing the folding mechanism). Two important cases are considered. Firstly, the fold angle (angle between adjacent beams), Ψ, is zero and only flexural waves propagate. In the second case, the fold angle is greater than zero (Ψ > 0). This causes longitudinal and transverse vibration to be coupled. FEM models are used to validate both these analyses.

Increasing the fold angle was found to inflict profound changes to the wave transmission characteristics of the structure. In general, increasing the fold angles caused the bandwidth of bandgaps to increase significantly. For the lowest four bandgaps we found bandwidth increases of 252 %, 177 %, 230 % and 163 % respectively at Ψ = 90 deg (relative to the bandwidths at Ψ = 0). In addition, significant increase in bandwidth of the odd-numbered bandgaps occurs even at small fold angles- the bandwidth for the first and third bandgaps effectively double in size (increase by 100%) at Ψ = 20 deg relative to those at Ψ = 0. This has important ramifications in the context of tunable wave manipulation and adaptive filtering.

In addition, by expanding out the characteristic equation of transfer matrix for the straight structure, we prove that the upper band edge of the n^th bandgap will always equal the n^th simply supported natural frequency of the constituent beam. Further, we found that the ratio (EI/k_t) is an important parameter affecting the bandwidth of bandgaps. For low values of the ratio, effectively, no bandgap exists. For higher values of the ratio (EI/k_t), we obtain a relatively large bandgap over which no waves propagate. This can have important ramifications for the design of foldable structures. As an alternative to impedance-based structural health monitoring, these insights can aid in health monitoring of deployable structures by tracking the bandwidth of bandgaps which can provide important clues about the mechanical parameters of the structure.

Mitigating excessive vibration of civil engineering structures using various types of devices has been a conspicuous research topic in the past few decades. Some devices, such as electromagnetic transducers, which have a capability of exerting control forces while simultaneously harvesting energy, have been proposed recently. These devices make possible a self-regenerative system that can semi-actively mitigate structural vibration without the need of external energy. Integrating mechanical, electrical components, and control algorithms, these devices open up a new research domain that needs to be addressed. In this study, the feasibility of using an actor-critic based reinforcement learning control algorithm for simultaneous vibration control and energy harvesting for a civil engineering structure is investigated. The actor-critic based reinforcement learning control algorithm is a real-time, model-free adaptive technique that can adjust the controller parameters based on observations and reward signals without knowing the system characteristics. It is suitable for the control of a partially known nonlinear system with uncertain parameters. The feasibility of implementing this algorithm on a building structure equipped with an electromagnetic damper will be investigated in this study. Issues related to the modelling of learning algorithm, initialization and convergence will be presented and discussed.

This manuscript details the derivation and solution of the equations of motion of angle-shaped resonators, composed of two prismatic members attached at various angles. The first part of the paper is devoted to the derivation of the analytical solution for the dynamic of a two member structure. The governing equation and the boundary conditions are derived by taking the variation of the Hamiltonian. The boundary value problem is then solved analytically giving rise to the characteristic equation of the system. In order to assess the validity of the analytical model presented, the analytical solution is compared against a semi-analytical model, finite element analysis and experiments. In the second part of the manuscript, we derive the electro-mechanical equation of motion of the angle-shaped resonator. The behavior of the harvester when subjected to single and multiple harmonic excitation is investigated along with the sensitivity onto the power harvested due to the folding angle.

This paper describes a method that could generate electric energy from the propagating ocean waves by implementing an actively controlled tuned mass damper on a ship sailing on the ocean. There are three fundamental requirements for any alternative energy method to make it work in practice. The first issue is that there should be affluent energy sources in the nature. Then, we should collect and confine them in a compact space by means of a smart method. Finally, we must convert the renewable energy into electric power as fast as possible. The author discusses the weak points and strong points of the proposed power generating method, while paying attention to these three requirements. The author started an observation project that the vibration data from the vessels sailing on the ocean would be collected under different conditions. The motion data obtained from a ship on the ocean gives the energy density spectrum in the frequency domain, which verifies the first requirement mentioned above. There is the appropriate natural period that determines the performance of the device, or equivalently the power of the generator. The solution for the second requirement is the tuned mass damper method, which indirectly collect the energy from the primal system to the auxiliary system by means of gravity. The last requirement is satisfied by the unique control algorithm known as acceleration feedback method, which enhances the cost performance of the tuned mass damper with the low frequency dynamic property.

Energy harvesting of environmental vibrations has been an intensive research field for several years, but there are lingering challenges regarding low frequency applications. Building off our recent invention of a multi-stable, broadband electromagnetic harvester relying on a dual resonant, rectilinear-to-rotary motion converter, research detailed in this paper outlines the creation of theoretical models for the dual resonator and systematically examines these models through experiments to further understand the interrelation of key design parameters and to optimize the harvester’s performance. More specifically, the dual resonant system converts broadband rectilinear vibrations to rotational motions via magnetic coupling, while frequency up-conversion via magnetic plucking converts low frequency vibrations into high frequency rotations. By combining the advantages of multi-stable nonlinearity, the invented dual resonant energy harvester possesses high power density at low operating frequencies. In this paper, a nonlinear electromechanical model of the dual resonant harvester is established, and the parametric study is conducted for various repulsive magnets configurations. Subsequent experiments validate the theoretical analysis. Systematic analysis of both theoretical and experimental results shows that the initial rotation angle and the configurations among the coupling magnets are critical to determining the operating patterns of the rotor and fully exploiting the potential of magnetic plucking to increase voltage output. The optimized dual resonator is advantageous over the linear harvesters by providing wider low frequency bandwidth via the inherent nonlinear dynamics.

Energy harvesters primarily depend on on a groups of unit cells to harvest energy at broadband frequencies so that each unit cell is responsible to harvest energy at a distinct frequency. Other design complexity, space, and financial profusion are required for transferring from unit-frequency to multi-frequency energy scavenging. Also, it is very unlikely to obtain expected power output if the available vibration source doesn’t match the designed loading condition (usually, unidirectional) of the device and requires rearrangement of the base structure to have projected output. In this paper we model the unique feature of acoustic metamaterial (AM), which is not only able to harvest energy at multiple frequencies using only a unit cell device, but also able to harvest energy under a variety of uncoupled (unidirectional) and coupled (multi-directional) vibration environments with an identical base structure arrangement.

Parametric excitation has been investigated for several years as an effective way to drive a structure parametrically into large distinctive responses. However, parametric resonance requires a minimum threshold of excitation to be triggered. To reduce the threshold, we propose a two-degree-of-freedom vibration system. This system consists of two perpendicular beams each with a tip magnet placed so the same poles face each other. The repulsive magnetic force couples the motion of the two beams. By decreasing the distance between the magnets, the threshold value for parametric excitation decreases. In addition, the repulsive magnetic force decreases the first resonance frequency of the vertical beam and thus its principal parametric resonance. Lowering the threshold excitation and parametric resonance frequency are two unique properties that make the device ideal for energy harvesting at low frequencies.

There is increasing interest in the use of lighter and more flexible hydrodynamic lifting bodies, and the use of active and passive smart structures to simultaneously increase efficiency and maneuverability or to harvest flow kinetic energy. Hydrodynamic lifting bodies can behave very differently compared to aerodynamic lifting bodies because of the much higher fluid density. To focus on the physics, we will use a cantilevered rectangular hydrofoil as a canonical proxy to more complex lift generating devices such as propellers, turbines, wings, and control surfaces, etc. Specifically, we will investigate the maximum deformation and stability limit for hydrofoils made of different materials to quantify the feasible operation space. To efficiently explore the large parametric space, inviscid analytical equations are used to determine the governing non-dimensional material, geometric, and flow parameters, which are systematically varied to examine the passive hydroelastic responses and stability boundaries of canonical hydrofoils with spanwise flexibility. The results demonstrate the influence of the relative magnitude between the solid and fluid inertial, damping, and stiffness terms, and resulting impact on the hydroelastic response, governing instability mechanism, and instability boundaries. The results also demonstrate that lifting bodies in water have much lower natural frequencies and higher damping coefficients than in air because of higher fluid inertial and damping forces, both of which are proportional to the fluid density. While all components of the fluid forces are proportional to the fluid density, the fluid damping forces grow with the velocity, while the fluid disturbing forces grow with velocity square. Therefore, the static divergence tends to be the governing instability mode for lifting bodies in water, while the flutter is typically the governing instability mode for lifting bodies in air. The results indicate that the maximum tip deformations in water are limited to approximately the chord length for bending and less than two degrees for twisting to avoid the material or static divergence failure.

A controllable damper that utilizes a friction type magnetorheological gel (MRG) valve and liquid spring technology was designed, built, and characterized under this study. A high-performance MRG material was developed for this damper, where the design space constraints minimized the damper dimensions. Electromagnetic finite element analyses were performed to optimize the controllable and liquid spring valve dimensions. The liquid spring valve utilized shim stacks for asymmetric rebound and compression loading. System modeling was performed where the effectiveness of various control system algorithms in reducing the transmitted acceleration levels were analyzed. The fabricated liquid spring controllable damper was characterized, and then installed on a single degree-of-freedom quarter-car experimental system. The characterization study demonstrated the liquid spring effect, as well as the controllability of the device. The quarter car experiments revealed that the device is more effective in reducing the acceleration levels at relatively higher operating speeds (up to 11 in/s). The device was also tested for spring stiffness at elevated temperatures. It was demonstrated that the liquid spring stiffness changes minimally at high operating temperatures.

Magnetorhological fluids (MR) have been applied to numerous devices or systems which require forward or feedback control to achieve desired performances. One of applications is the rehabilitation device. MR dampers applied to artificial joints are implemented with two phases; stance phase: motion to support the feet on the ground, and swing phase : motion to step out. In case of stance phase, the damping force should be increased by applying the magnetic field to support the body. On the other hand, in case of swing phase, the damping force should be removed by not applying the magnetic field so that the prosthesis can be easily rotated by the motor. In this study, a special mechanism of MR damper is proposed to make a prosthetic leg which can derive on/off mode using permanent magnet only. The design mechanism is undertaken and damping force is analyzed to validate the effectiveness of the proposed damper system for the patient’s motion without control device.

A magnetorheological elastomer (MRE) shock and vibration isolation mount with a semi-active control system was designed, built and tested. The stiffness of the MRE mount can be increased or decreased with respect to a fail-safe stiffness value, based on the control system feedback for effective shock and vibration mitigation. The 12.7mm (0.5") thick MREs of the mount were specifically formulated to achieve a fail-safe static stiffness of the system equal to the legacy mount to be replaced. The magnetic circuit of the mount was designed and optimized using three-dimensional electromagnetic finite element analysis. A control algorithm was developed that detects and differentiates between both shock and vibration events to adjust the MRE mount stiffness properties accordingly to mitigate the event. The control algorithm was developed, incorporated with hardware and tested for functionality. The shock and vibration mitigation performance of the MRE mount with control system was examined via an experimental study. It was demonstrated that the MRE mount and control system mitigates up to 15g shock and 25 Hz vibration events for weights up to 550 lbs attached to the mount. The mount was also tested under various atmospheric conditions (temperature, pressure, relative humidity, water submergence), and no variation in performance of the MRE mount was observed.

The requirements for transmission and coupling elements are rising continuously. Our previous investigations were focused on the elimination of viscous induced drag-torques in coupling elements based on magnetorheological fluids by a MR-fluid movement control. For a further reduction of weight and space requirements a design of a magnetic circuit with a serpentine flux guidance was introduced last year. For a further enhancement of the torque density a design based on multiple shear gaps is proposed in this contribution. Due to the MR-fluid movement control using partially filled shear gaps a simple arrangement of several coaxial shear gaps is not applicable. Instead, each shear gap has to be separated by a novel MR-fluid sealing, which allows also a drag- torque free operation above certain rotational speeds. Combining these features result in a MRF-based coupling element with an enhanced torque density at simultaneously reduced drag-torque.

Heavy duty vehicles are essential for the heavy duty purpose in harsh environment. Therefore, severe vibration transmitted to the vehicle driver even can lead to the illness. In this study, the operating principle for the conventional passive and semi-active mount that isolate vibration is analyzed. Based on this, a new MR (magnetorheological) mount that overcomes the problem of conventional mount is proposed. In the first step, the working principle of the proposed mount is analyzed. Subsequently, the feasibility of the proposed model is confirmed by presenting the damping force and controllable range.

In this paper, we propose a new method for tuning parameters in a negative capacitor circuit, which is utilized in the piezoelectric shunt damping. A stochastic numerical optimization method, called Covariance Matrix Adaptation-Evolution Strategy (CMA-ES), is selected to minimize the effect of disturbance to an experimental setup. In addition, an additional restriction is imposed on CMA-ES so that the internal stability of the closed-loop system is guaranteed. The effectiveness of the proposed method is demonstrated by numerical examples.

Separation along the interfaces of layers (delamination) is a principal mode of failure in laminated composites and its detection is of prime importance for structural integrity of composite materials. In this work, structural vibration response is employed to detect and classify delaminations in piezo-bonded laminated composites. Improved layerwise theory and finite element method are adopted to develop the electromechanically coupled governing equation of a smart composite laminate with and without delaminations. Transient responses of the healthy and damaged structures are obtained through a surface bonded piezoelectric sensor by solving the governing equation in the time domain. Wavelet packet transform (WPT) and linear discriminant analysis (LDA) are employed to extract discriminative features from the structural vibration response of the healthy and delaminated structures. Dendrogram-based support vector machine (DSVM) is used to classify the discriminative features. The confusion matrix of the classification algorithm provided physically consistent results.

Semi-active suspensions based on magnetorheological (MR) dampers are expected to innovate automotive suspension systems. However, the accuracy of the damping force models of MR dampers affects the control performance of MR semiactive suspension systems. Based on the experimental data of a self-developed MR damper, the parameters of a resistorcapacitor (RC) hysteresis model are identified. The obtained RC hysteresis model can describe and predict the hysteresis nonlinear damping force of the MR damper effectively. Further, the dynamic model of a 1/4 MR semi-active suspension system based on the MR damper is established, and a linear quadratic regulator (LQR) control strategy based on state feedback is designed. The performance of the 1/4 MR semi-active suspension system is simulated and analyzed in time and frequency domains.

Carbon nanotubes (CNT) can be profitably embedded into the matrix of composite structure to obtain a distributed sensor able to estimate deformations due to vibrations, impacts or high load applied. In this paper electrical measurements of carbon nanotube multiscale GFRPs have been carried out to monitor low velocity impacts and to estimate the severity of corresponding damages. The work has been developed experimentally, by monitoring the variation of the structure electrical impedance as a consequence of impacts. Electrical measurements show that there is an initial decrease of electrical resistance due to plate compression, followed by an increase due to tunneling effect of carbon nanotubes. Criteria based on the dynamic variation of electrical impedance were proposed and their correlation with the impact energy was studied. Severity of damages has been estimated with different approaches, by measuring the damage extends through the microscope. The analysis shows that CNT can properly describe the dynamics of impact. Synthetic indexes proposed in this work to estimate the severity of damages from CNTs electrical measurements have some limitations and, at now, only partially fit with experimental data.

Deep drawing is a practical process to create shell metal parts. In this process punch draw sheet metal into die cavity. Punch and die must be changed for part with new geometry leading to high costs and time waste. To overcome this problem, in the last years the use of rubber die has become more and more widespread. This technique requires the use of ultrasonic vibration that helps to reduce friction between punch and die and then the risk of thinning. In this paper a numerical study, based on finite element method, of the deep drawing process of circular sections with rubber die assisted by ultrasonic vibration is presented. An in depth analysis on the effects of amplitude and frequency of ultrasonic vibration is carried out. Results show that by increasing amplitude and frequency of ultrasonic vibration, limits on the forming force can be profitably increased, ensuring a better execution of the process.

Active vibration suppression can be profitably implemented on large structures to enhance their performance (eg. comfort, fatigue life, etc.). Application on large structures, however, often require a complex setup that makes these solutions too complex to be effectively used. That is because of the high number of sensors and actuators, suitably cabled, in addition to all the devices necessary to condition and amplify the signals of measurement and control and to execute in real time the control algorithms synthesized. One of the most effective technique to reach this goal is to increase the equivalent damping of the system and then the dissipation of the kinetic energy (the so called skyhook damping technique).

This work is aimed to simplify this setup by using stand-alone smart dampers developed to carry out operations of vibration control in an autonomous way, thus containing an actuator, the sensors needed to evaluate the vibratory state of the structure, and a micro-controller embedding different control algorithm. The paper shows that the use of more devices, each working independently to perform a decentralized control, can be profitably used to better suppress vibration of the structure.

Wind turbine blades are being bigger and bigger, thus requiring lightweight structures that are more flexible and thus more sensitive to dynamic excitations and to vibration problems. This paper investigates a preliminary architecture of large wind turbine blades, embedding thin sheets of SMA to passively improve their total damping. A phenomenological material model is used for simulation of strain-dependent damping in SMA materials and an user defined material model was developed for this purpose. The response of different architectures of SMA embedded blades have been investigated in the time domain to find an optimal solution in which the less amount of SMA is used while the damping of the system is maximized

Stringed wooden instruments, like violins or double basses, experience a decrease in performance if they are not played for a long time. For this reason, top class instruments are usually given to musicians and played every day to preserve sound quality. The paper deals with the design, construction and testing of a device to be inserted in the bridge of a stringed wooden instrument to simulate the stresses experienced by the instrument during normal playing. The device could provide a simple, fast and inexpensive way to recover the sound of an instrument that has not been played for a period of time, or even to enhance the instrument’s sound. The device is based on two magnetostrictive actuators that can exert suitable forces on the body of the violin. The device has been designed and tested to exert forces as constant as possible in the range of frequency between 10 Hz and 15kHz. Experimental tests are carried out to evaluate the effect of the device on the sound produced by the violin during a 3 weeks hours training. Two hi-quality microphones have been used to measure principal harmonics and changes during the test. Results show that in the first part of the test (approximately 100 hours) amplitudes of main harmonics widely change, while in the following their values remain constant. This behavior demonstrates the violin has reached its “nominal” status.

In this work an active vertically hung tube has been designed, fabricated and tested. The active tube was made of three separate 3D printed parts assembled and glued together. Shape Memory Alloy (SMA) wires were embedded as actuators in the body of the tube to privilege from their robust actuation and high energy density. Three SMA wires were trained and installed evenly on the exterior peripheral side of the tubes to realize motion in multiple directions. A deadweight was hung to one end of the tube to exert a certain amount of pre-stress on actuators. This design offers a restricted actuation because the two wires on the opposite side always resist the intended deflection. Hence, for a proper actuation, each wire was stressed to a certain level to exhibit either expansion or contraction upon demand. This amount of stress was selected based on rigorous experimental data. Power supply units were integrated and linked to a python program to control the amount of power passed through each SMA wire. The active tube was tested, and its movement was captured via a camera and analyzed by ImageJ software for the two cases free of stress and with an applied external load. The electrical resistance of the each SMA wire was measured and used for controlling the tube’s deflection in each direction. This work demonstrated the feasibility of using three evenly distributed SMA wires on a tube to create motion in 3D direction.

Deployable structures are increasingly studied for their enormous potential of space application. In this paper, we report the fabrication and analysis of an Active Bimorph Structure (ABS) by evaluating the variation of the curvature and the tip-displacement of the top fiber layer with respect to the change in applied voltage. The composite showing the bi-directional bending behaviour was fabricated using E-Glass fibre and Room Temper- ature Vulcanising (RTV) Silicone Rubber, embedded with NiTiNOL Shape Memory Alloy wires in two layers, at 0 and 90 degrees. The study of the deflection motion of the ABS shows that with an increase in temperature of the SMA wire, the bending curvature initially increases almost proportionally and finally reaches a constant steady curvature and the experimental results satisfy this condition. The second layer of the ABS system when actuated gives the composite a bi-directional bending behaviour. The future aim is to create an Active Bimorph Box Structure (ABBS) with composites placed and glued in such a manner that upon excitation the structure transforms first into a cylinder and eventually into a curved cylindrical element following its property of bi-directional bending.

Nano-piezoelectric energy harvesters, due to their ability to convert mechanical vibrations to electrical current, are apt candidates for self-powered NEMs devices. Further, these are strain based electrical potential generators and can be used in tactile devices for accurate position sensing. ZnO, due to its piezoelectric properties and semiconducting nature is the ideal candidate for such applications. This paper proposes an analytical model to explain the potentials generated due to ZnO nano-films on being subjected to different forms of static loading. The model also incorporates the effect of different boundary conditions imposed on the nano-film. A perturbation theory based approach has been used to generate the analytical model. Initially, the strains are calculated ignoring the piezoelectric effect. Later, the electromechanical coupling is taken into consideration and the potentials have been calculated as a second order effect. The finite element simulation results agree with the theory to an accuracy of 5%. The profiles for piezoelectric potential distribution agree also well with the simulations. These piezoelectric potential profiles can also be used in smart materials for obtaining the required deformation in a specimen by applying a similar electrical potential across it.

Phosphor-free InGaN/AlGaN core-shell nanowire light-emitting diodes (LEDs) grown by molecular beam epitaxy have been developed and their application in visible light communication (VLC) has been investigated. The electroluminescence spectra of these nanowire LEDs show a very broad spectral linewidth and fully covers the entire visible spectrum. High-brightness phosphor-free LEDs with highly stable white-light emission and high color-rendering index (CRI) of >98 were obtained by controlling the Indium composition in the device active region. Moreover, the phosphor-free nanowire white-LEDs exhibit relatively high 3-dB frequency bandwidth of ~ 1.4 MHz which is higher compared to that of phosphor-based white LEDs at the same measurement condition. Such high-performance phosphorfree nanowire LEDs are being further improved and are ideally suited for future smart lighting applications and communications.

This research reports on the design and experimental verification of a tuned inertial mass electromagnetic trans- ducer (TIMET) for energy harvesting from vibrating large structures and structural vibration control devices. The TIMET consists of a permanent-magnetic synchronous motor (PMSM), a rotational mass, and a tuning spring. The PMSM and the rotational mass are connected to a ball screw mechanism so that the rotation of the PMSM is synchronized with the rotational mass. And the tuning spring interfaced to the shaft of the ball screw mechanism is connected to the vibrating structure. Thus, through this ball screw mechanism, transla- tional vibration motion of the structure is converted to rotational behavior and mechanical energy is absorbed as electrical energy by the PMSM. Moreover, the amplified equivalent inertial mass effect is obtained by rotating relatively small physical masses. Therefore, when the stiffness of the tuning spring is determined so that the inertial mass resonates with the natural frequency of the vibratory structure, the PMSM rotates more effectively. As a result, the generated energy by the PMSM can be increased. The authors design a prototype of the TIMET and carry out experiments using sine and sine seep waves to show the effectiveness of the tuned inertial mass mechanism. Also, an analytical model of the proposed device is developed using a curve fitting technique to simulate the behavior of the TIMET.

The tuned vibration absorber (TVA) has been an effective device for vibration control in many engineering applications. However, using the TVA can cause resonance and actually increase the vibration of the primary system. In recent years, many configurations of the adaptive tuned vibration absorber (ATVA) have been developed to improve the performance of the TVA. In all these studies, a great deal configurations focused on how to widen the bandwidth of the ATVA, but very little effort has been put into the work on reducing the resonance of the primary system. In this paper, a modified control plan based on variable mass ATVA is proposed to reduce the primary system resonance. A number of simulations were carried out to verify the performance of the control plan, and the results show that it’s effective on resonance reduction of the primary system.

This paper deal with a semi-active type bush design and magnetic analysis associated with the magnetorheological elastomer. It is focused on the magnetic field intensity analysis with 3 coil structure. The bush design consists of 3 coil structure of the bush in order to apply the magnetic field. As a result of first investigation, it is found that MRE thickness and electric current are most important parameters to design an effective bush. From the magnetic analysis, it is identified that the magnetic permeability of the MRE is lower than MR fluid. In addition, the bush model is formulated to have the uniformity of the magnetic flux and intensity field distribution.