This PDF file contains the front matter associated with SPIE Proceedings Volume 9799 including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

Converting ambient mechanical energy to electricity, vibration energy harvesting, enables powering of the low-power remote sensors. Nonlinear energy harvesters have the advantage of a wider frequency spectrum compared to linear resonators making them more efficient in scavenging the broadband frequency of ambient vibrations. To increase the output power of the nonlinear resonators, we propose an energy harvester composed of a cantilever piezoelectric beam carrying a movable magnet facing a fixed magnet at a distance. The movable magnet on the beam is attached to a spring at the base of the beam. The spring-magnet system on the cantilever beam creates the variable double well potential function. The spring attached to the magnet is in its compressed position when the beam is not deflected, as the beam oscillates, the spring energy gradually releases and further increases the amplitude of vibration. To describe the motion of the cantilever beam, we obtained two coupled partial differential equations by assuming the cantilever beam as Euler-Bernoulli beam considering the effect of the moving magnet. Method of multiple scales is used to solve the coupled equations. The cantilever beam with the two magnets is a bi-stable system. Making one magnet movable can create internal resonance that is explored as a mechanism to increase the frequency bandwidth. The effect of system parameters on the frequency bandwidth of the resonator is investigated through numerical solutions. This study benefits vibration energy harvesting to achieve a higher performance when excited by the wideband ambient vibrations.

We explore the potential for bandwidth enhancement by merely exploiting the hardening nonlinearity of a flexible cantilever. To date, this cubic hardening behavior has been minor due to dissipative effects, especially fluid drag. The goal here is to minimize the fluid damping and thereby achieve the jump phenomenon. A vacuum setup that is compatible with the armature of a long-stroke shaker is employed. Experiments are conducted for a range of air pressure and base excitation levels. The overall nonlinear non-conservative elastodynamics of the cantilever is also modeled and experimentally validated by empirically accounting for fluid damping.

The understanding of wave propagation in a metamaterial with hierarchical, auxetic rectangular perforations is presented in this work. The metamaterial is a 2D structure with chaining horizontal and vertical perforations exhibiting auxetic in-plane behaviour. The unit cell of this lattice is identified as the reference level 0. Hierarchical structures are composed of structural elements which themselves have structure. At level 0, 4 rigid squares are present in the unit cell. In each square, the reference structure is used by applying a scale ratio to obtain the level 1. The same strategy is used to reach the upper level in each subunit. A geometric parametric investigation of these rectangular perforations using a numerical asymptotic homogenisation finite element approach is done. Some numerical eigenvalue tools are used for the dispersion analysis of this structure. It is first observed that the total width of Band gaps increases with the hierarchy. The porosity induced by the perforations is taken into account in the mechanical properties. The symmetry of the geometry in the x-y plane allow to define the entire geometry of the unit cell using only 2 parameters: the void aspect ratio, the intercell spacing and the hierarchy level. When decreasing the intercell spacing, the total width of Band gaps increases and the effective stiffness in x and y directions decrease, allowing for increased rotations of the rigid squares, so auxetic behaviour is greater. Hierarchical levels shift from isotropic to orthotropic, hierarchical levels are always auxetic.

This work describes the development and experimental analysis of hyperelastic honeycombs with graded densities, for the purpose of energy absorption. Hexagonal arrays are manufactured from thermoplastic polyurethane (TPU) via fused filament fabrication (FFF) 3D printing and the density graded by varying cell wall thickness though the structures. Manufactured samples are subject to static compression tests and their energy absorbing potential analysed via the formation of energy absorption diagrams. It is shown that by grading the density through the structure, the energy absorption profile of these structures can be manipulated such that a wide range of compression energies can be efficiently absorbed.

Recent investigations on the concept of modular metastructures have demonstrated remarkable adaptivity of properties as a synergistic product of assembling together metastable modules, modules that exhibit coexisting states for the same topology. It has been found that such modularity provides an accessible pathway for unprecedented massive property adaptation. Despite the extensive report on the static or quasistatic characteristics of modular metastructures, much remains to be explored regarding their dynamic characteristics. This research initiates the study on transient response of a modular metastructure under impulsive excitation. Numerical studies characterize the adaptability of energy exchange and localization characteristics afforded by metastable states. It is found that responses of internal bistable masses of the metastable modules play an important role in determining energy distribution of the overall system. It is discovered that low internal bistable mass and high impulsive energy level are beneficial for energy to be localized and dissipated internally. Additionally, mechanism behind effective energy absorption is disclosed. Overall, this investigation provides opportunities to tailor dynamical responses using modular metastructures and opens potential avenues for designing transient vibration absorbers.

In this paper, a computational study is presented of structural vibration control that is realized by switching a magneto-strictive transducer between high and low stiffness states. Switching is accomplished by either changing the applied magnetic field with a voltage excitation or changing the shunt impedance on the transducer's coil (i.e., the magneto-strictive material's magnetic boundary condition). Switched-stiffness vibration control is simulated using a lumped mass supported by a damper and the magneto-strictive transducer (mount), which is represented by a nonlinear, electromechanical model. Free vibration of the mass is calculated while varying the mount's stiffness according to a reference switched-stiffness vibration control law. The results reveal that switching the magnetic field produces the desired change in stiffness, but also an undesired actuation force that can significantly degrade the vibration control. Hence, a modified switched-stiffness control law that accounts for the actuation force is proposed and implemented for voltage-controlled stiffness switching. The influence of the magneto-mechanical bias condition is also discussed. Voltage-controlled stiffness switching is found to introduce damping equivalent to a viscous damping factor up to about 0.13; this is shown to primarily result from active vibration reduction caused by the actuation force. The merit of magneto-strictive switched-stiffness vibration control is then quantified by comparing the results of voltage- and shunt-controlled stiffness switching to the performance of optimal magneto-strictive shunt damping. For the cases considered, optimal resistive shunt damping performed considerably better than both voltage- and shunt-controlled stiffness switching.

In this study, the pre-stress force in pre-stressed concrete (PSC) girders is monitored via mountable PZT interface under varying temperature. Firstly, an impedance-based technique using mountable PZT interface is proposed for pre-stress-loss monitoring in tendon-anchorage systems. A cross correlation-based temperature-effect compensation algorithm using an effective frequency shift (EFS) of impedance signatures is visited. Secondly, lab-scale experiments are performed on a PSC girder instrumented with a mountable PZT interface at tendon-anchorage. A series of temperature variation and pre-stress-loss events are simulated for the lab-scale PSC girder. Thirdly, the feasibility of the mountable PZT interface for pre-stress-loss monitoring in tendon-anchorage is experimentally verified under constant temperature conditions. Finally, the PZT interface device is examined for pre-stress-loss monitoring under temperature changes to validate its applicability. The temperature effect on impedance signatures is compensated by minimizing cross-correlation deviation between impedance patterns of the mountable PZT interface.

Structural health monitoring (SHM) has attracted researchers’ interests for the past two decades to reinforce the maintenance of the aging infrastructure systems all over the world. As one of the potential solutions, the electro-mechanical impedance (EMI) method was introduced in the early 1990s and has a great number of potential applications in the SHM of civil, mechanical and aerospace industries. This paper studied the impedance-based technique with the presence of environmental/operational variability, especially the influences of temperature and uniaxial stress on the admittance signature-based features. A comprehensive analytical model is established and provides satisfactory agreements with the experimental results. The stress and temperature sensitivities of all the proposed features are quantified using the experimental measurements, with discussions on their advantages and disadvantages. The final results illustrate that the EMI method can potentially provide effective measure for thermal stress.

The piezoelectric impedance-based damage identification, which traditionally uses the inverse optimization with sensitivity matrix, can in theory identify the damage location and damage severity at the same time. However, the inverse problem is underdetermined in most cases, since the number of unknowns (i.e., possible damage locations and severities) is far more than that of useful measurements. Recently, a new damage identification strategy has been proposed, which is based on Bayesian inference framework. This strategy necessitates employing forward analysis-based instead of inverse-based identification procedures. As the Bayesian inference is sampling-based algorithm, it requires repeated evaluation (FEA analysis) in the parameter space. Since in most cases, one has no prior information on the damage location and severity, the Bayesian inference should be carried out in a large parameter space that will need extremely high computing cost. In this research, a robust and efficient damage identification procedure by employing piezoelectric impedance is developed by combining the sensitivity matrix analysis and the Bayesian inference framework. The new procedure includes two steps. In the first step, a group of possible damage locations and corresponding severity are predicted based on sensitivity matrix analysis, which however does not require solving the inverse of the sensitivity matrix. The prediction from the first step is then used as the sample space. Subsequently, Bayesian inference is carried out to further determine the damage location and severity. Numerical simulations are carried out to demonstrate the damage identification performance.

In this paper, a novel ultrasonic propagation imaging system, called a full-field pulse-echo ultrasonic propagation imaging (FF PE UPI) system is presented. The coincided laser beams for ultrasonic sensing and generation are scanned and pulse-echo mode laser ultrasounds are captured. This procedure makes it possible to generate full-field ultrasound in through-the-thickness direction as large as the scan area. The system nondestructively inspected targets with two-axis translation stages. Various structural inspection results in the form of full-field ultrasonic wave propagation videos are introduced, which are an aluminum honeycomb sandwich, ailerons and carbon fiber reinforced plastic (CFRP) honeycomb sandwich structures including various defects.

Fatigue cracks in steel bridges degrade the load-carrying capacity of these structures. Fatigue damage accumulation caused by the repetitive loading of everyday truck traffic can cause small fatigue cracks initiate. Understanding the growth of these fatigue cracks is critical to the safety and reliability of our transportation infrastructure. However, modeling fatigue in bridges is difficult due to the nature of the loading and variations in connection integrity. When fatigue cracks reach critical lengths failures occur causing partial or full closures, emergency repairs, and even full structural failure. Given the aging US highway and the trend towards asset management and life extension, the need for reliable, cost effective sensors and monitoring technologies to alert bridge owners when fatigue cracks are growing is higher than ever.

In this study, an innovative Long-Term Electrochemical Fatigue Sensor (LTEFS) has been developed and introduced to meet the growing NDT marketplace demand for sensors that have the ability to continuously monitor fatigue cracks. The performance of the LTEFS has been studied in the laboratory and in the field. Data was collected using machined specimens with different lengths of naturally initiated fatigue cracks, applied stress levels, applied stress ratios, and for both sinusoidal and real-life bridge spectrum type loading. The laboratory data was evaluated and used to develop an empirically based algorithm used for crack detection. Additionally, beta-tests on a real bridge structure has been completed. These studies have conclusively demonstrated that LTEFS holds great potential for long-term monitoring of fatigue cracks in steel structures

An adaptive control system for correcting wave-front error of a CFRC reflector has been studied. Errors investigated in this paper were mainly introduced by fabrication and gravity. 72 Piezoelectric Ceramic Transducer (PZT) actuators were integrated to the CFRC reflector to conduct wave-front error control. The adaptive CFRC reflector was fixed on an optical platform without any external loads. The temperature and humidity were well controlled during the experimental study. The wave-front error correction algorithm is based on influence matrix approach coupled with least squares optimization method. The linear relationship between the PZT actuator’s input voltage and the output displacement of the adaptive CFRC reflector surface is validated. A laser displacement sensor was used for measuring the displacements. The influence matrix was obtained experimentally by measuring the displacements of the associated points while each actuator was activated separately. The wave-front error and influence matrix were measured using a V-Stars photogrammetry system. Experimental investigation validated that this adaptive control system is capable to significantly reduce the reflector surface geometry error. Experimental results are correlated very well with simulation results which were obtained by using a multidisciplinary analytical approach. Conclusions of this study suggest that the adaptive CFRC reflector technology can provide a low cost method to significantly increase the precision of a CFRC reflector.

Research in broadband nonlinear piezoelectric energy harvesting has gained traction in recent years as resonant, linear harvesters do not operate optimally in dynamic environments. By placing a linear harvester in a symmetric magnetic field, a nonlinear restoring force allows the system to realize motion across two potential wells. Different levels of excitation enable the system to oscillate solely in one potential well, periodically across both potential wells, or aperiodically across both potential wells. Periodic interwell motion is considered desirable for nonlinear energy harvesting systems, however, coexistent attractors inhibit uniqueness of such a solution. The authors have previously shown that chaotic, aperiodic motion between potential wells can be optimized for improved energy harvesting. The technique applied a chaotic controller to stabilize a large amplitude periodic orbit within the chaotic attractor. This work considers the basins of attraction of the two concurrent attractors and applies an intermittent control law in which the system is perturbed from a chaotic, aperiodic interwell response into the desirable large amplitude, periodic, interwell response.

To enhance the energy conversion performance of piezoelectric vibration energy harvesters, such structures have been recently designed to leverage bandwidth-enhancing nonlinear dynamics. While key findings have been made, the majority of researchers have evaluated the opportunities when the harvesters are connected to pure resistive loads (AC interface). The alternating voltage generated by such energy harvesting systems cannot be directly utilized to power conventional electronics. Rectifying circuits are required to interface the device and electronic load but few efforts have considered how a standard rectifying DC interface circuit (DC interface) connected to a nonlinear piezoelectric energy harvester influences the system performance. The aim of this research is to begin exploring this critical feature of the nonlinear energy harvesting system. A nonlinear, monostable piezoelectric energy harvester (MPEH) is fabricated and evaluated to determine the generated power and useful operating bandwidth when connected to a DC interface. The nonlinearity is introduced into the harvester design by tuneable magnetic force. An equivalent circuit model of the MPEH is implemented with a user-defined nonlinear behavioral voltage source representative of the magnetic interaction. The model is validated comparing the open circuit voltage from circuit simulation and experiment. The practical energy harvesting capability of the MPEH connected to the AC and DC interface circuits are then investigated and compared, focusing on the influence of the varying load on the nonlinear dynamics and subsequent bandwidth and harvested power.

This paper presents an experimental verification of a wideband nonlinear vibration energy harvester which has a globally stabilized high-energy resonating response. For the conventional linear vibration energy harvester, the maximum performance of the power generation and its bandwidth are in a relation of trade-off. The resonance frequency band can be expanded by introducing a Duffing-type nonlinear resonator in order to enable the harvester to generate larger electric power in a wider frequency range. However, since such nonlinear resonators often have multiple stable steady-state solutions in the resonance band, it is difficult for the nonlinear harvester to maintain the high performance of the power generation constantly. The principle of self-excitation and entrainment has been utilized to provide the global stability to the highest-energy solution by destabilizing other unexpected lower-energy solutions by introducing a switching circuit of the load resistance between positive and the negative values depending on the response amplitude of the oscillator. In this study, an experimental verification of this concept are carried out. An experimental prototype harvester is designed and fabricated and the performance of the proposed harvester is experimentally verified. It has been shown that the numerical and experimental results agreed very well, and the highest-energy solutions above the threshold value were successfully stabilized globally.

Energy harvesting from galloping oscillations of a bluff body can be used to supply power to a wireless sensor. In this paper we investigate the possibility to use a galloping-based piezo-aeroelastic energy harvester to supply power to a wireless sensors network installed on a freight train to measure the accelerations in correspondence of axle boxes. The monitoring system will be used to detect possible deteriorations of the running conditions that, in the worst cases, can lead to the vehicle derailment. Unlike other applications in this case the air speed relative to the body is due to the train motion and, for typical freight trains and standard running conditions, is equal to about 20 m/s. In the paper we discuss the design of the harvester on the basis of the constrains due to the application. Preliminary aerodynamic tests shows the limitation of the classical quasi-steady theory of galloping as a consequence of the interaction with the vortex shedding phenomenon.

In vibration-based energy harvesting, ambient vibration often occurs in such small amplitudes that it cannot be used to drive electrical generators directly. To maximize the amount of output power, the input motion is usually amplified before being used for power generation. This work presents a non-resonant piezoelectric energy harvester that relies on a compliant mechanism to amplify a given persistent input motion in order to enhance the power output. The device can be used in situations where a small cyclic relative motion occurs between two surfaces, and where a device can be fitted to extract energy. The use of a compliant mechanism, as opposed to conventional gear drives or linkages, alleviates problems of excessive clearances, friction and power losses. A finite element model is developed to investigate the effect of the various design parameters on the system performance in terms of the amplification ratio, stiffness and output voltage. Findings of the present work are verified both numerically and experimentally on a cam-driven polymer mechanism. A parametric study is conducted to investigate the most influential variables in an attempt to optimize the design parameters for maximum power output. A magnetically bistable piezoelectric beam, driven by the compliant mechanism, is finally presented and provides substantially greater amounts of output power.

In this paper, a piezoelectric vibrational energy harvester utilizing coupled bending and torsional vibrations is investigated. The proposed system consists of a cantilever-type substrate covered by the piezoelectric ceramic and a proof mass which is perpendicularly connected to the free end of the cantilever beam by a rigid bar. While the natural frequency and output voltage of the conventional system are affected by bending deformation of the piezoelectric plate, the proposed system makes use of its twisting deformation. The natural frequency of the device can be significantly decreased by manipulating the location of the proof mass on the rigid bar. In order to validate the performance of the proposed energy harvester, numerical simulations and vertical shaker tests are carried out. It is demonstrated that the proposed energy harvester can shift down its resonant frequency considerably and generate much higher output power than the conventional system. It is, therefore, concluded that the proposed energy harvester utilizing the coupled bending and torsional vibrations can be effectively applied to low-frequency vibration situations.

Simple piezo benders are able to harvest energy almost only at their first natural frequency. Thus, their efficiency is good only in presence of harmonic excitation having frequency equal to their first natural frequency. In case of wide band excitation, instead, more complex solutions have to be sought for. In particular, various forms of nonlinearity have been investigated that allow to “bend” resonance peaks and thus convert kinetic energy into electric energy over a wider frequency band. Also harvester with more benders have been analyzed.

In the present paper a novel periodic substructure is proposed that allows to obtain several eigen-frequencies in a given frequency range. Moreover, the position where the piezo bender is placed has the same mode of vibration for all these eigen-frequencies. The bender is therefore able to harvest energy at all these eigen-frequencies thus greatly improving the overall efficiency. The next step will be to introduce nonlinearities in the substructure to even further extend the range of frequencies at which energy is harvested.

Low-power vibration and acoustic energy harvesting scenarios typically require a storage component to be charged to enable wireless sensor networks, which necessitates power conditioning of the AC output. Piezoelectric beam-type bending mode energy harvesters or other devices that operate using a piezoelectric element at resonance produce high voltage levels, for which AC-DC converters and step-down DC-DC converters have been previously investigated. However, for piezoelectric stack energy harvesters operating off-resonance and producing low voltage outputs, a step-up circuit is required for power conditioning, such as seen in electromagnetic vibration energy scavengers, RF communications, and MEMS harvesters. This paper theoretically and experimentally investigates power conditioning of a low-voltage piezoelectric stack energy harvester.

Recently, vibration energy harvesting from surrounding environments to power wearable devices and wireless sensors in structure health monitoring has received considerable interest. Piezoelectric conversion mechanism has been employed to develop many successful energy harvesting devices due to its simple structure, long life span, high harvesting efficiency and so on. However, there are many difficulties of microscale cantilever configurations in energy harvesting from low frequency ambient. In order to improve the adaptability of energy harvesting from ambient vibrations, a two degrees of freedom (2-DOF) magnetic-coupled piezoelectric energy harvester is proposed in this paper. The electromechanical governing models of the cantilever and clamped hybrid energy harvester are derived to describe the dynamic characteristics for 2-DOF magnetic-coupled piezoelectric vibration energy harvester. Numerical simulations based on Matlab and ANSYS software show that the proposed magnetically coupled energy harvester can enhance the effective operating frequency bandwidth and increase the energy density. The experimental voltage responses of 2-DOF harvester under different structure parameters are acquired to demonstrate the effectiveness of the lumped parameter model for low frequency excitations. Moreover, the proposed energy harvester can enhance the energy harvesting performance over a wider bandwidth of low frequencies and has a great potential for broadband vibration energy harvesting.

The important required characteristics of an artificial muscle for a human arm-like manipulator are high strain and high power density. From this viewpoint, an SMA (shape memory alloy) spring is a good candidate for the actuator of a robotic manipulator that utilizes an artificial muscle. In this study, the maximum power density of an SMA spring was evaluated with respect to the input power. The spring samples were fabricated from SMA wires of different diameters ranging between 0.1 and 0.3 mm. For each diameter, two types of wires with different transition temperatures were used. The relationship between the transition temperature and maximum power density was also evaluated. Each SMA spring was stretched downward by an attached weight and the temperature was increased through the application of an electric current. The displacement, velocity, and temperature of the SMA spring were measured by laser displacement sensors and a thermocouple. Based on the experimental data, it was determined that the maximum power densities of the different SMA springs ranged between 1,300 and 5,500 W/kg. This confirmed the applicability of an SMA spring to human arm-like robotic manipulators. The results of this study can be used as reference for design.

In this paper the structural behavior of reinforced concrete (RC) beams with smart rebars under two point loading system has been numerically studied, using Finite Element Method. The material used in this study is Super-elastic Shape Memory Alloys (SE SMAs) which contains nickel and titanium. In this study, different quantities of steel and SMA rebars have been used for reinforcement and the behavior of these models under two point bending loading system is studied. A comparison of load carrying capacity for the model between steel reinforced concrete beam and the beam reinforced with S.M.A and steel are performed. The results show that RC beams reinforced with combination of shape memory alloy and steel show better performance.

This paper presents a simple closed loop circuit (oscillator) design for producing sustained, oscillations required to continuously vibrate the resonance based pressure sensor at its resonant frequency. For each variation in applied input pressure, the sensor’s resonant frequency varies and the circuit makes the sensor to vibrate at its new resonant frequency, thereby enabling the measurement of change in resonant frequency shift due to corresponding pressure. The resonant condition is achieved by automatic tuning of phase angle required to satisfy Barkhausen criteria. The proposed circuit is evaluated analytically and verified experimentally for different pressure sensors fabricated using various grades of Stainless Steel material.

Thermal control is an important aspect of spacecraft design, particularly in the case of crewed vehicles, which must maintain a precise internal temperature at all times in spite of sometimes drastic variations in the external thermal environment and internal heat loads. The successes of the Space Shuttle and International Space Station programs have shown that this can be accomplished in Low Earth Orbit (LEO), however, crewed spacecraft traveling beyond LEO are expected to encounter more challenging thermal conditions with significant variations in both the heat rejection requirements and environment temperature. Such missions will require radiator systems with high turndown ratios, defined as the ratio between the maximum and minimum heat rejection rates achievable by the radiator system. Current radiators are only able to achieve turndown ratios of 3:1, far less than the 12:1 turndown ratio which is expected to be required on future missions. An innovative radiator concept, known as a morphing radiator, uses the temperature-induced shape change of shape memory alloy (SMA) materials to achieve a turndown ratio of at least 12:1. Predicting the thermal and structural behavior of SMA-based morphing radiators is challenging due to the presence of two-way thermomechanical coupling that has not been widely considered in the literature. Previous work has demonstrated the application of a technique known as a partitioned analysis procedure which can be used to simulate the behavior of morphing radiators. This work describes ongoing efforts to evaluate the physical accuracy of this approach by conducting validation studies. A detailed finite element model of a morphing radiator is developed and executed using the framework. Preliminary results show close agreement between the experimental data and model predictions, giving additional confidence in the partitioned approach.

The performance of lightweight structures can be severely affected by vibration. New design concepts leading to lightweight, slender structural components can increase the vulnerability of the components to failure due to excessive vibration. The intelligent approach to address the problem would be the use of materials which are more capable in dissipating the energy due to their high value of loss factor. Among the different materials available to achieve damping, much attention has been attached to the use of shape memory alloys (SMAs) because of their unique microstructure, leading to good damping capacity.

This work describes the design and optimization of a hybrid layered composite structure for the passive suppression of flexural vibrations in slender and light structures. Embedding the SMA layers in composite structure allows to combine different properties: the lightness of the base composite (e.g. fiber glass), the mechanical strength of the insert of metallic material and the relevant damping properties of SMA, in the martensitic phase. In particular, we put our attention on embedding the CuZnAl in the form of thin sheet in a layered composite made by glass fiber reinforced epoxy. By appropriately positioning of the SMA sheets so that they are subjected to the maximum curvature, the damping of the hybrid system can be considerably enhanced.

Accordingly analytical method for evaluating the energy dissipation of the thin sheets with different shapes and patterns is developed and is followed by a shape optimization based on genetic algorithm. Eventually different configurations of the hybrid beam structure with different patterns of SMA layer are proposed and compared in the term of damping capacity.

The shape memory polymer polystyrene (PS) has been used to create complex hierarchical wrinkling in the fabrication of stretchable thin film bimetallic sensors ideal for wearable based gesture monitoring applications. The film has been bonded to the elastomer polydimethylsiloxane (PDMS) and operates as a strain gauge under the general notion of geometric piezoresistivity. The film was subject to tensile, cyclic, and step loading conditions in order to characterize its dynamic behavior. To measure the joint angle of the metacarpophalangeal (MCP) joint on the right index finger, the sensor was adhered to a fitted golf glove above said joint and a motion study was conducted. At maximum joint angle the sensor experienced roughly 23.5% strain. From the study it was found that two simple curves, one while the finger was in flexion and the other while the finger was in extension, were able to predict the joint angle from measured voltage with an average error of 2.99 degrees.

Carbon fiber reinforced plastic (CFRP) has been used various industrial fields, because of high strength, light weight, corrosion resistance and other properties. In this study, lead zirconate titanate (PZT) ceramic particles which is one of typical piezoelectric material and shape memory alloy powder dispersed in CFRP laminate in order to improve the vibration damping by dissipating vibration energy quickly. The loss factor (tanδ) is measured in Dynamic mechanical analyzer (DMA) which is used to measure the viscoelastic behavior of a material to verify the change in vibration damping. The results show that there exists difference on vibration damping ability between CFRP with PZT ceramic particles and CFRP with SMA powder.

A method to improve low velocity impact resistance of aeroengine composite casing using shape memory alloy’s properties of shape memory(SM) and super-elasticity(SE) is proposed in this study. Firstly, a numerical modeling of SMA reinforced composite laminate under low velocity impact load with impact velocity of 10 m/s is established based on its constitutive model implemented by the VUMAT subroutine of commercial software ABAQUS. Secondly, the responses of SMA composite laminate including stress and deflection distributions were achieved through transient analysis under low velocity impact load. Numerical results show that both peak stress and deflection values of SMA composite laminate are less than that without SMA, which proves that embedding SMA into the composite structure can effectively improve the low velocity impact performance of composite structure. Finally, the influence of SM and SE on low velocity impact resistance is quantitatively investigated. The values of peak stress and deflection of SMA composite based on SM property decrease by 18.28% and 9.43% respectively, compared with those without SMA, instead of 12.87% and 5.19% based on SE. In conclusion, this proposed model described the impact damage of SMA composite structure and turned to be a more beneficial method to enhance the impact resistance by utilizing SM effect.

Origami has emerged as a potential tool for the design of mechanical metamaterials and metastructures whose novel properties originate from their crease patterns. Most of the attention in origami engineering has focused on the wellknown Miura-Ori, a folded tessellation that is flat-foldable for folded sheet and stacked blocks. This study advances the state of the art and expands the research field to investigate generic degree-4 vertex (4-vertex) origami, with a focus on facet-binding. In order to understand how facet-binding attributes to the mechanical properties of 4-vertex origami structures, geometries of the 4-vertex origami cells are analyzed and analytically expressed. Through repeating and stacking 4-vertex cells, origami sheets and stacked origami blocks can be constructed. Geometry analyses discover four mechanisms that will lead to the self-locking of 4-vertex origami cells, sheets, and stacked blocks: in-cell facet-binding, inlayer facet-binding, inter-layer facet binding, and in-layer and inter-layer facet-bindings. These mechanisms and the predicted self-locking phenomena are verified through 3D simulations and prototype experiments. Finally, this paper briefly introduces the unusual mechanical properties caused by the locking of 4-vertex origami structures. The research reported in this paper could foster a new breed of self-locking structures with various engineering applications.

This study characterizes hybrid control approaches for the variable recruitment of fluidic artificial muscles with double acting (antagonistic) actuation. Fluidic artificial muscle actuators have been explored by researchers due to their natural compliance, high force-to-weight ratio, and low cost of fabrication. Previous studies have attempted to improve system efficiency of the actuators through variable recruitment, i.e. using discrete changes in the number of active actuators. While current variable recruitment research utilizes manual valve switching, this paper details the current development of an online variable recruitment control scheme. By continuously controlling applied pressure and discretely controlling the number of active actuators, operation in the lowest possible recruitment state is ensured and working fluid consumption is minimized. Results provide insight into switching control scheme effects on working fluids, fabrication material choices, actuator modeling, and controller development decisions.

Increasing demand to harvest energy from renewable resources has caused significant research interest in unsteady aerodynamic and hydrodynamic phenomena. Apart from the traditional horizontal axis wind turbines, there has been significant growth in the study of bio-inspired oscillating wings for energy harvesting. These systems are being built to harvest electricity for wireless devices, as well as for large scale mega-watt power generation. Such systems can be driven by aeroelastic flutter phenomena which, beyond a critical wind speed, will cause the system to enter into limitcycle oscillations. When the airfoil enters large amplitude, high frequency motion, leading and trailing edge vortices form and, when properly synchronized with the airfoil kinematics, enhance the energy extraction efficiency of the device. A reduced order dynamic stall model is employed on a nonlinear aeroelastic structural model to investigate whether the parameters of a fully passive aeroelastic device can be tuned to produce limit cycle oscillations at desired kinematics. This process is done through an optimization technique to find the necessary structural parameters to achieve desired structural forces and moments corresponding to a target limit cycle. Structural nonlinearities are explored to determine the essential nonlinearities such that the system’s limit cycle closely matches the desired kinematic trajectory. The results from this process demonstrate that it is possible to tune system parameters such that a desired limit cycle trajectory can be achieved. The simulations also demonstrate that the high efficiencies predicted by previous computational aerodynamics studies can be achieved in fully passive aeroelastic devices.

This work aims to demonstrate the detrimental effect of fluid damping on the bandwidth of a flexible nonlinear energy harvester and thereby further enhance the performance by minimizing nonlinear damping. A vacuum setup has been introduced to conduct nonlinear base excitation experiments at different air pressure levels in an effort to control the quadratic (velocity-squared) damping coefficient. It is shown that reduced air pressure substantially enhances the frequency bandwidth for primary resonance excitation. The empirical electromechanical model is modified to express the fluid damping in terms of fluid pressure and validated experimentally for different excitation levels.

A multifunctional compliant structure is proposed that can harvest electrical power from both incident sunlight and ambient mechanical energy including wind flow or vibration. The proposed energy harvesting device consists of a slender, ribbon-like, flexible thin film solar cell that is laminated with piezoelectric patches at either ends and mounted in the cross flow of wind in a clamped-clamped end condition with an adjustable axial preload. Taking this motivation forward a system model of the energy harvester is developed which captures the structural response of the solar ribbon and couples it with Theodorsen unsteady aerodynamics to predict the flutter boundary conditions as a function of applied axial preload tension. The model also accounts for geometric and material discontinuities, by effective use of Transfer Matrix Method (TMM) modeling technique both in bending and torsional degrees of freedom. This paper also derives TMM technique for torsional vibrations with an applied axial load from first principles, verifies the method and presents its applicability for the proposed energy harvester. The paper also points out that the flutter instability arises out of different structural modes at different values applied axial tension, with the help of a sample modal convergence plot. The analysis also presents the possibility to tune the solar ribbon to operate at an optimal reduced frequency by adjusting the applied axial preload.

In this paper, we present investigations on wireless sensors for fluid control inside a pipe. Autarkic sensors are in the technical trend. They are typically connected with a transceiver unit for data transmission. Sensors usually need a lower amount of energy than data transceivers. Therefore, they are commonly supplied via wires or batteries with electricity. With common technologies, this request leads to high requirements on tightness in liquids since poor sealing could easily lead to failures. Replacement of batteries inside pipes is complicated and almost accompanied by a flow interruption. The application of energy harvesters as power supply is therefore a good alternative. In our studies we used flexible piezoelectric energy harvesters of PVDF (Poly-Vinylidene-Di-Fluoride). All harvesting units consist of piezoelectric PVDF-foils as active layers and Aluminum-foils as electrodes. The layers were stacked alternating on each other and wound to a spool. A LDPE-film wraps the spool and prevents the inflow of liquids. The device has following parameters:

No. of windings: 4 in air, 4, 5, 7 in water

Dimensions: 15 mm Ø 22mm

Materials: PDVF: 25μm; Aluminimum: 6μm, LDPE: 25μm

A ring shaped bluff body was placed inside the pipe to induce turbulence in the fluid stream. As the harvesters have been arranged downstream of the bluff body, they were forced to oscillate independent of the media. In each case, deformation of the active layers led to a polarization and a separation of electrical charges. Experiments were carried out in a wind channel as well as in a water pipe. In air, the spool oscillates with a frequency of about 30Hz, at a wind speed of about 7m/s. A -Voltage of about 4V (peak-peak) was measured. This delivers in case of power adjustment, power values of about 0.54μW. In water, the velocity of the fluid was limited to nearly one tenth. Oscillation starts only at a water speed above 0.6m/s. The average oscillation frequency is about 18Hz. At a velocity of 0.74m/s, a peak-peak-Voltage up to about 2.3V was found. In case of impedance adjustment, the power was about 0.33μW. This power is stored in a capacitor. Assuming a data transmission unit consumes about 0.2 mWs during one operational period of 1 second, the duty cycle time can be calculated to about 6.2 minutes for air harvesting and 10.1 minutes for harvesting in water.

This paper investigates the use of electrostatic forces for vibration control of MEMS devices. A micro beam subject to electrostatic loading is considered. The electrostatic forces cause softening nonlinearity and their amplitudes are proportional to the square of applied DC voltages. An optimization problem is set up to minimize the vibration level of the micro-beam at given excitation frequencies. A new method based on incrementing nonlinear control parameters of the system and Harmonic Balance is used to obtain the required DC voltages that suppress unwanted vibration of the micro-beam. The results are illustrated using numerical simulations

Energy-harvesting series electromagnetic tuned mass dampers (EMTMDs) have been recently proposed for dual-functional energy harvesting and robust vibration control by integrating the tuned mass damper (TMD) and electromagnetic shunted resonant damping. In this paper, we derive ready-to-use analytical tuning laws for the energy-harvesting series EMTMD system when the primary structure is subjected to force or ground excitations, like wind loads or earthquakes. Both vibration mitigation and energy harvesting performances are optimized using H₂ criteria to minimize root-mean-square values of the deformation of the primary structure, or maximize the average harvestable power. These analytical tuning laws can easily guide the design of series EMTMDs under various ambient loadings. Later, extensive numerical analysis is presented to show the effectiveness of the series EMTMDs. The numerical analysis shows that the series EMTMD is superior to mitigate the vibration of the primary structure nearly across the whole frequency spectrum, as compared to that of classic TMDs. Simultaneously, the series EMTMD can better harvest the energy due to broader bandwidth effect. Beyond simulations, this paper also experimentally verifies the effectiveness of the energy-harvesting series electromagnetic TMDs in both vibration mitigation and energy harvesting.

Real-time hybrid simulation (RTHS) is a modern cyber-physical technique used for the experimental evaluation of complex systems, that treats the system components with predictable behavior as a numerical substructure and the components that are difficult to model as an experimental substructure. Therefore it is an attractive method for evaluation of the response of civil structures under earthquake, wind and anthropic loads. In this paper, the response of three-story shear frame controlled by a tuned liquid column damper (TLCD) and subject to base excitation is considered. Both passive and semi-active control strategies were implemented and are compared. While the passive TLCD achieved a reduction of 50% in the acceleration response of the main structure in comparison with the structure without control, the semi-active TLCD achieved a reduction of 70%, and was robust to variations in the dynamic properties of the main structure. In addition, a RTHS was implemented with the main structure modeled as a linear, time-invariant (LTI) system through a state space representation and the TLCD, with both control strategies, was evaluated on a shake table that reproduced the displacement of the virtual structure. Current assessment measures for RTHS were used to quantify the performance with parameters such as generalized amplitude, equivalent time delay between the target and measured displacement of the shake table, and energy error using the measured force, and prove that the RTHS described in this paper is an accurate method for the experimental evaluation of structural control systems.

Wide-span and lightweight floors are often prone to structural vibrations due to their low resonance frequency and poor material damping. Their dynamic behaviour can be improved using passive, semi-active or active vibration control devices.

The following article proposes a novel method for the controller synthesis for active vibration control. An existing passive TMD (tuned mass damper) is modelled and equipped with an actuator in order to provide more efficient damping. Using an iterative optimization approach under constraints, an optimal controller is found which minimizes a quadratic cost function in frequency domain.

A simulation of an existing test bench shows that the active vibration control device is able to provide increased damping compared to the passive TMD.

This paper presents analytical modeling of a novel type of passive friction damper for seismic hazard mitigation of structural systems. This seismic protective device, which is termed as Passive Electromagnetic Eddy Current Friction Damper (PEMECFD), utilizes a solid-friction mechanism in parallel with an eddy current damping system to dissipate a larger amount of input seismic energy than that by a device with based on solid friction only. In this passive damper, friction force is produced through a magnetic repulsive action between two permanent magnets (PMs) magnetized in the direction normal to the friction surface. The eddy current damping force in the damper is generated because of the motion of the PMS in the vicinity of a conductor. Friction and eddy current damping parts of the damper are able to produce ideal rectangular and elliptical hysteresis loops individually. Seismic hazard mitigation effectiveness of the proposed damper has been demonstrated through an implementation on a two-degree-of-freedom frame building structure. Numerical results show that the proposed damper is more efficient in dissipating input seismic energy than a Passive Linear Viscous Damper (PLVD) with same force capacity.

In this paper, analytical models of partially covered piezoelectric plate actuators operated with longitudinal (d₃₃) or transveral (d₃₁) coupling are developed. The models are based on classical laminated plate theory and linear piezoelectricity. Explicit formulas have been derived for thin piezoelectric films and the optimal structural dimensions are determined. A performance comparison between the two modes of operation is carried out. Finite element analysis validates the analytic models. Finally, the performance of an actuator with an inter digital electrode-based longitudinal coupling is compared with its counterpart transversally coupled actuator. The comparison determines the stronger actuator when operation is electric-field-strength limited.

The semi-active Synchronized Switching Damping (SSD) family is based on a nonlinear shunting circuit applied to piezoelectric actuators, where the circuit characteristics are switched along the vibration cycles of the structure. SSD offers many advantages with respect to other vibration suppression techniques using piezoelectric actuators. Indeed, multiple modes can be suppressed with a relatively simple system and with very low power consumption. This allows the realization of self-powered control systems, without the need of wiring and external power supply. Moreover, the characteristics of this control strategy make it very robust to the variation of the dynamic characteristics of the structure, outperforming the classic passive linear shunts.

Different SSD techniques have been developed, varying the circuit characteristics and the switching logic. Although this control family has been studied for many years, all the works are limited to the single actuator case, losing in generality with respect to many practical cases. For this reason, the aim of this work is to apply SSD control with multiple actuators and to study the interaction of the actuators and their shunting circuits in order to optimize the damping performance.

The study will be performed numerically and then an experimental setup will be realized to test the proposed solutions.

This paper proposes a new type of a direct-drive valve (DDV) suspension system for vehicle controlled by the piezostack actuator associated with displacement amplifier. In order to achieve this goal, a new type of controllable piezostack DDV damper is designed and its performance evaluation of damping force is undertaken. Next, a full vehicle suspension system consisting of sprung mass, spring, tire and the piezostack DDV damper is constructed. After deriving the governing equations of the motion for the proposed the piezostack DDV suspension system, the skyhook controller is implemented for the realization of the full vehicle. Analytical model of the whole suspension system is then derived and performance characteristics are analyzed through numerical simulation. Finally, vibration control responses of the vehicle suspension system such as vertical acceleration are evaluated under both bump and sine road conditions.

An infinite dimensional model for a three-layer active constrained layer (ACL) beam model, consisting of a piezoelectric elastic layer at the top and an elastic host layer at the bottom constraining a viscoelastic layer in the middle, is obtained for clamped-free boundary conditions by using a thorough variational approach. The Rao-Nakra thin compliant layer approximation is adopted to model the sandwich structure, and the electrostatic approach (magnetic effects are ignored) is assumed for the piezoelectric layer. Instead of the voltage actuation of the piezoelectric layer, the piezoelectric layer is proposed to be activated by a charge (or current) source. We show that, the closed-loop system with all mechanical feedback is shown to be uniformly exponentially stable. Our result is the outcome of the compact perturbation argument and a unique continuation result for the spectral problem which relies on the multipliers method. Finally, the modeling methodology of the paper is generalized to the multilayer ACL beams, and the uniform exponential stabilizability result is established analogously.

This paper explores the practical benefits of the recently proposed by the authors tuned mass-damper-inerter (TMDI) visà- vis the classical tuned mass-damper (TMD) for the passive vibration control of seismically excited linearly building structures assumed to respond linearly. Special attention is focused on showcasing that the TMDI requires considerably reduced attached mass/weight to achieve the same vibration suppression level as the classical TMD by exploiting the mass amplification effect of the ideal inerter device. The latter allows for increasing the inertial property of the TMDI without a significant increase to its physical weight. To this end, novel numerical results pertaining to a seismically excited 3-storey frame building equipped with optimally designed TMDIs for various values of attached mass and inertance (i.e., constant of proportionality of the inerter resisting force in mass units) are furnished. The seismic action is modelled by a non-stationary stochastic process compatible with the elastic acceleration response spectrum of the European seismic code (Eurocode 8), while the TMDIs are tuned to minimize the mean square top floor displacement. It is shown that the TMDI achieves the same level of performance as an unconventional “large mass” TMD for seismic protection (i.e., more than 10% of attached mass of the total building mass), by incorporating attached masses similar to the ones used for controlling wind-induced vibrations via TMDs (i.e., 1%-5% of the total building mass). Moreover, numerical data from response history analyses for a suite of Eurocode 8 compatible recorded ground motions further demonstrate that optimally tuned TMDIs for top floor displacement minimization achieve considerable reductions in terms of top floor acceleration and attached mass displacement (stroke) compared to the classical TMD with the same attached mass.

Structural control systems are considered an effective alternative for reducing vibrations in civil structures and are classified according to their energy supply requirement: passive, semi-active, active and hybrid. Commonly used structural control systems in buildings are passive friction dampers, which add energy dissipation through damping mechanisms induced by sliding friction between their surfaces. Semi-Active Variable Friction Dampers (SAVFD) allow the optimum efficiency range of friction dampers to be enhanced by controlling the clamping force in real time. This paper describes the development and performance evaluation of a low-cost SAVFD for the reduction of vibrations of structures subject to earthquakes. The SAVFD and a benchmark structural control test structure were experimentally characterized and analytical models were developed and updated based on the dynamic characterization. Decentralized control algorithms were implemented and tested on a shaking table. Relative displacements and accelerations of the structure controlled with the SAVFD were 80% less than those of the uncontrolled structure

This paper reports the scheme of a research project funded by the Ministry of Land， Infrastructure， Transport and Tourism (MLIT) from the fiscal year of 2012 to 2014 under the title of "Development of base isolation device complied with the ultimate strength design code." The theoretical prediction tells us a new approach to develop a highly stable laminated rubber bearing that has a constant buckling load even under large lateral displacement. Relatively high shear stiffness makes it more stable and the height of the bearing should be longer than its diameter. They are the newly discovered theoretical buckling stability criteria from the previous studies conducted by the author’s research team. The experimental studies in this project show the compatibility with the theoretical prediction and highly linear loaddisplacement relationship under large deformation. The performance of the newly developed device satisfies the requirement of the ultimate strength design code, if the ground condition of the target building is normally solid enough to prevent liquefaction. The theoretically predicted buckling stability of the laminated rubber bearings has been experimentally verified by the specimens of this project.

Impact excitation is common in the environment. Impact piezoelectric energy harvesting could realize frequency up-conversion. However, the dissipation mechanism in impact piezoelectric energy harvesting has not been investigated so far. There is no comprehensive model to be able to analyze the impact piezoelectric energy harvesting thoroughly. This paper is aimed to develop a generalized model that considers dissipation mechanism of impact piezoelectric energy harvesting. In this electromechanical model, Hertzian contact theory and impact dissipation mechanism are identified as constitutive mechanisms. The impact force is compared and the energy distribution is analyzed so that input energy corresponds to impact dissipated energy, structural damping dissipated energy and harvested electrical energy. We then nondimensionalize the developed model and define five dimensionless parameters with attributed physical meanings, including dimensionless parameters of impact dissipation, mass ratio, structural damping, electromechanical coupling, and electrical load. We conclude it is more accurate to consider impact dissipation mechanism to predict impact force and harvested energy. The guideline for improving harvested energy based on parametric studies of dimensionless model is to increase mass ratio, to minimize structural damping, to maximize electromechanical coupling, to use optimal load resistance for impedance matching, and to choose proper impact velocity .

In last ten years, a lot of researchers have begun to look into obtaining electricity from the movement between human and their backpack that occurs during walking. In this paper, an innovative, elastically-suspended backpack with mechanical motion rectifier (MMR) based energy harvester is developed to generate electricity with high efficiency and reliability. Up to 28 Watts peak electrical power can be produced by the MMR based backpack energy harvester. A dynamic model for the system is presented along with experimental results. Three dual mass models for different distinct harvesters: pure viscous, non MMR, and MMR, are proposed, and a comparison in the output power and human comfort between the three models is discussed.

Vibration energy harvesting has been shown as a promising power source for many small-scale applications mainly because of the considerable reduction in the energy consumption of the electronics and scalability issues of the conventional batteries. However, energy harvesters may not be as robust as the conventional batteries and their performance could drastically deteriorate in the presence of uncertainty in their parameters. Hence, study of uncertainty propagation and optimization under uncertainty is essential for proper and robust performance of harvesters in practice. While all studies have focused on expectation optimization, we propose a new and more practical optimization perspective; optimization for the worst-case (minimum) power. We formulate the problem in a generic fashion and as a simple example apply it to a linear piezoelectric energy harvester. We study the effect of parametric uncertainty in its natural frequency, load resistance, and electromechanical coupling coefficient on its worst-case power and then optimize for it under different confidence levels. The results show that there is a significant improvement in the worst-case power of thus designed harvester compared to that of a naively-optimized (deterministically-optimized) harvester.

This article identifies and studies key parameters that characterize a horizontal diamagnetic levitation (HDL) mechanism based low frequency vibration energy harvester with the aim of enhancing performance metrics such as efficiency and volume figure of merit (FoM_v). The HDL mechanism comprises of three permanent magnets and two diamagnetic plates. Two of the magnets, aka lifting magnets, are placed co-axially at a distance such that each attract a centrally located magnet, aka floating magnet, to balance its weight. This floating magnet is flanked closely by two diamagnetic plates which stabilize the levitation in the axial direction. The influence of the geometry of the floating magnet, the lifting magnet and the diamagnetic plate are parametrically studied to quantify their effects on the size, stability of the levitation mechanism and the resonant frequency of the floating magnet. For vibration energy harvesting using the HDL mechanism, a coil geometry and eddy current damping are critically discussed. Based on the analysis, an efficient experimental system is setup which showed a softening frequency response with an average system efficiency of 25.8% and a FoM_v of 0.23% when excited at a root mean square acceleration of 0.0546 m/s² and at frequency of 1.9 Hz.

As electronic devices become both ubiquitous and more energy efficient, powering them with energy harvested from, for example, piezoelectric materials has become a subject of much interest. The field does indeed show promise, as harvesting energy from smart materials has the potential to replace batteries completely in some low-power applications. This paper presents modeling of piezo-electret foam assembled in a multilayer stack configuration, with the required adhesives and conductors, as a multiple degree of freedom (MDOF) system. The benefits of using the foam over some piezo-ceramics include its high flexibility, its light weight, and its lead-free composition. This model predicts the mechanical and electromechanical response to base excitation for any number of layers of piezo-electret foam. Building upon previous work which modeled the piezo-electret stack as a single degree of freedom (SDOF) system, the MDOF model provides information concerning the response of internal stack layers. The MDOF model is validated against the experimentally determined mechanical and electrical responses of a 20-layer piezo-electret foam stack. Also, the internal stack dynamics at higher order vibration modes suggest that charge cancellation is a serious outcome of vibration at these modes that designers need to consider.

By scavenging the vibration energy from the ambience, the piezoelectric energy harvesting (PEH) technology provides one of the most promising solutions towards the everlasting power supplies for distributed wireless sensors. Given the capacitive characteristics of the piezoelectric devices, synchronized switch interface circuits, such as the synchronized switch harvesting on inductor (SSHI), have been developed towards the harvested power enhancement. The self-powered sensing and control issue is essential for implementing these circuit innovations in practical applications. This paper provides a comparative study on the recently proposed mechatronic self-powered SSHI (MSP-SSHI) and the existing electronic self-powered SSHI (ESP-SSHI). The MSP-SSHI uses a single-pole double-throw switch to simultaneously perform the sensing and switching functions in the SSHI interface. It can reduce the switching threshold and energy losses caused in the semiconductors of the electronic solution, and no need to care about the high-voltage breakdown problems in the ESP-SSHI. On the other hand, the distance between the pole and throws will introduce certain switching phase difference under the larger range of excitation. A piecewise linear model of the MSP-SSHI is built to analyze the switching phase difference. It was found that the damping ratio and stiffness in the mechanical switch can significantly influence the switching phase difference. Simulations show that well-designed damping ratio and stiffness can help the MSP-SSHI maintain smaller switching phase difference, and therefore improve the output power.

Considering piezoelectric damping, a resonant shunt can lead to a significant vibration reduction when tuned to the mechanical mode to control. However, limits appear when looking at practical applications in a low frequency range: the required inductance is often too high to be satisfied with standard passive components. Moreover, even if the inductor is eventually available, the internal resistance of the component generally exceeds the value which is required for a shunt optimization. Suitable inductors can be designed for applications requiring high inductance and low resistance values. Indeed, the permeance of a magnetic circuit can be significantly increased by the use of closed cores made of high permeability materials. In this paper, three designs are described and compared: an inductor from standard series and two handmade inductors involving a ferrite core and a nanocrystalline toroid. The components are successively integrated into a piezoelectric shunt dedicated to the vibration control of a cantilever beam. Depending on the frequency of the target mechanical mode to control, the benefits and the limits of the different inductors are observed. It is shown that custom designs can definitely extend to lower frequency the application of the passive resonant shunt strategy.

The aim of active vibration control is to enhance the performance of a system (eg. comfort, fatigue life, etc.) by limiting vibrations. 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). Application of active vibration control often require a complex setup. When large structures are considered, it is often necessary to have a 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. This work arises from the need to simplify this situation, developing a standalone device that is able of carrying out operations of vibration control in an autonomous way, thus containing in itself an actuator, the sensors needed to evaluate the vibratory state of the structure, and a micro-controller embedding different control algorithm. The design of the smart damper covers many aspects and requires a strong integration of different disciplines. A prototype has been realized and tested on a vibrating structure. The experimental results show good performance in suppress vibration.

Self-powered switching control has been proved to be very effective for vibration damping in case it is not possible to power up a fully active system and/or you have stringent requirements from an added weight point of view. However, the capability of harvesting the required energy for switching as well as the authority of the piezo actuator are greatly influenced by the actual position of the patches along the beam as well as by the circuit parameters. Indeed, varying them both control performance and energy requirement strongly change, making feasible or compromising the possibility to obtain a self-powered control system. Moreover, a difference of system or circuit parameters from ideality can affect the behavior of the damping layout.

In this paper the influence of all these parameters on control behavior are deeply studied. Aim of the paper is to provide a handbook to the choice of circuit parameters depending on the control system requirements.

Feedback control strategies are desirable for disturbance rejection of human-induced vibrations in civil engineering structures as human walking forces cannot easily be measured. In relation to human-induced vibration control studies, most past researches have focused on floors and footbridges and the widely used linear controller implemented in the trials has been the direct velocity feedback (DVF) scheme. With appropriate compensation to enhance its robustness, it has been shown to be effective at damping out the problematic modes of vibration of the structures in which the active vibration control systems have been implemented.

The work presented here introduces a disturbance observer (DOB) that is used with an outer-loop DVF controller. Results of analytical studies presented in this work based on the dynamic properties of a walkway bridge structure demonstrate the potential of this approach for enhancing the vibration mitigation performance offered by a purely DVF controller. For example, estimates of controlled frequency response functions indicate improved attenuation of vibration around the dominant frequency of the walkway bridge structure as well as at higher resonant frequencies. Controlled responses from three synthesized walking excitation forces on a walkway bridge structure model show that the inclusion of the disturbance observer with an outer loop DVF has potential to improve on the vibration mitigation performance by about 3.5% at resonance and 6-10% off-resonance. These are realised with hard constraints being imposed on the low frequency actuator displacements.

Performance of piezoelectric-based, semi-active vibration reduction approaches has been studied extensively in the past decade. Originally analyzed with single-degree-of-freedom systems, these approaches have been extended to multi-mode vibration reduction. However, the accompanying analysis typically assumes well-separated modes, which is often not the case for plate structures. Because the semi-active approaches induce a shift in the structural resonance frequency (at least temporarily), targeting a specific mode for vibration reduction can actually lead to additional vibration in an adjacent mode. This paper presents an analysis using a simplified model of a two-degree-of-freedom mass-spring-damper system with lightly-coupled masses to achieve two closely-spaced modes. This investigation is especially applicable to the resonance frequency detuning approach previously proposed to reduce vibrations caused by transient excitation in turbomachinery blades where regions of high modal density exist. More generally, this paper addresses these effects of stiffness state switches in frequency ranges containing regions of high modal density and subject to frequency sweep excitation. Of the approaches analyzed, synchronized switch damping on an inductor offers the greatest vibration reduction performance, whereas resonance frequency detuning and state switching each yield similar performance. Additionally, as the relative distance between resonance peaks decreases, the performance for the vibration reduction methods approaches that of a single-degree-of-freedom system; however, there are distances between these resonant peaks that diminish vibration reduction potential.

In this paper, a nanostructured piezoelectric beam is fabricated using vertically aligned lead zirconate titanate (PZT) nanowire arrays and its capability of continuous power generation is demonstrated through direct vibration tests. The lead zirconate titanate nanowires are grown on a PZT thin film coated titanium foil using a hydrothermal reaction. The PZT thin film serves as a nucleation site while the titanium foil is used as the bottom electrode. Electromechanical frequency response function (FRF) analysis is performed to evaluate the power harvesting efficiency of the fabricated device. Furthermore, the feasibility of the continuous power generation using the nanostructured beam is demonstrated through measuring output voltage from PZT nanowires when beam is subjected to a sinusoidal base excitation. The effect of tip mass on the voltage generation of the PZT nanowire arrays is evaluated experimentally. The final results show the great potential of synthesized piezoelectric nanowire arrays in a wide range of applications, specifically power generation at nanoscale.

An integrated semi-active seat suspension for both longitudinal and vertical vibration control is analyzed and tested in this paper. The seat suspension consists of a switching mechanism transforming both longitudinal and vertical motions into a rotary motion and a real-time damping-controllable system-a rotary magnetorheological (MR) damper working in pure shear mode and its corresponding control system. The switching mechanism employs the parallelogram frames as a motion guide which keeps the seat moving longitudinally and vertically. At the same time, both longitudinal and vertical motions are transformed into a reciprocating rotary motion that is transmitted to the rotary MR damper after an amplification by a gear mechanism. Both the longitudinal and vertical vibrations can be attenuated in real time through controlling the damping force (or torque) of the rotary MR damper. The mathematical model of the seat suspension system is established, simulated, and analyzed. The experimental test based on the test rig in Hefei University of Technology is implemented, and the results of simulation and experimental test are compared and analyzed.

The hydrocarbon industry has expressed interest in developing vibration based energy harvesting systems that can be deployed downhole and supplement or replace existing power sources. The energy output of such harvesters is highly dependent on the level of damping in the supporting structure which, in this case, would drive the systems vibrational input. A first step towards optimizing an energy harvester configuration is then to understand how key variables influence system damping. To this end an investigation was undertaken to identify how changing system boundary conditions effect damping in a fluid conveying pipe confined by a viscous fluid (i.e. a producing hydrocarbon well). The key variables investigated included the rotational boundary springs, the velocity of the conveyed fluid, and the viscosity of the annulus fluid. The system was modeled using Euler-Bernoulli beam theory and included a hydrodynamic forcing function to capture the effects of the viscous annulus fluid. The natural frequencies of the system were solved in the frequency domain with the system damping subsequently calculated. Lower damping ratios were observed: in stiffer systems, for lower conveyed fluid velocities, and for lower annulus fluid viscosities. A numeric example is provided to illustrate the interaction between the three variables of interest. These results are of direct interest to researchers and engineers developing vibrational energy harvesting systems for downhole deployment. Approved for publication, LAUR-16-21227.

The harvesting of mechanical strain and kinetic energy has received great attention over the past two decades in order to power wireless electronic components such as those used in passive and active monitoring applications. Piezoelectric ceramics, such as PZT (lead zirconate titanate), constitute the most commonly used electromechanical interface in vibration energy harvesters. However, there are applications in which piezoelectric ceramics cannot be used due to their low allowable curvature and brittle nature. Soft polymer PVDF (polyvinylidene fluoride) is arguably the most popular non-ceramic soft piezoelectric energy harvester material for such scenarios. Another type of polymer that has received less attention is PP (polypropylene) for electret-based energy harvesting using the thickness mode (33- mode). This work presents figure of merit comparison of PP versus PVDF for off-resonant energy harvesting in thickness mode operation, revealing substantial advantage of PP over PVDF. For thickness mode energy harvesting scenarios (e.g. dynamic compression) at reasonable ambient vibration frequencies, the figure of merit for the maximum power output is proportional to the square of the effective piezoelectric strain constant divided by the effective permittivity constant. Under optimal conditions and for the same volume, it is shown that PP can generate more than two orders of magnitude larger electrical power as compared to PVDF due to the larger effective piezoelectric strain constant and lower permittivity of the former.

This paper presents the analysis of a type of vibration energy harvester composed of an electromagnetic pendulum oscillator combined to an elastic main structure. In this study, the elastic main structure connected to the base is considered as a single degree-of-freedom (DOF) spring-mass-damper subsystem. The electromagnetic pendulum oscillator is considered as a dual-mass two-frequency subsystem, which is composed of a hollow bar with a tip winded coil and a magnetic mass with a spring located in the hollow bar. As the pendulum swings, the magnetic mass can move along the axial direction of the bar. Thus, the relative motion between the magnet and the coil induces a wire current. A mathematical model of the coupled system is established. The system dynamics a 1:2:1 internal resonance. Parametric analysis is carried out to demonstrate the effect of the excitation acceleration, excitation frequency, load resistance, and frequency tuning parameters on system performance.

Energy harvesting has been gaining significant interest as a potential solution for energizing next generation sensor and energy storage devices. The most widely investigated material for piezoelectric and pyro-electric energy harvesting to date is PZT (Lead Zirconate Titanate), owing to its good piezoelectric and pyro-electric properties. However, Lead is detrimental to human health and to the environment. Hence, alternative materials are required to be investigated for this purpose. In this paper, a lead free material Lithium Niobate (LNB) is reported as a potential material for pyro-electric energy harvesting. Although, it has lower pyro-electric properties than PZT, it has better properties than other lead free alternatives of PZT such as ZnO. In addition, LNB has a high curie point of 1142 °C, which makes it suitable for high temperature environment where other pyro-electric materials are not suitable. Therefore, a single crystal LNB has been investigated as a source of energy harvesting under alternative heating and cooling environment. A commercial 0.2 F super-capacitor was used as the energy storage device.

Three-phase transduction affords certain advantages in the efficient electromechanical conversion of energy, especially at higher power scales. This paper considers the use of a three-phase electric machine for harvesting energy from vibrations. We consider the use of vector control techniques, which are common in the area of industrial electronics, for optimizing the feedback loops in a stochastically-excited energy harvesting system. To do this, we decompose the problem into two separate feedback loops for direct and quadrature current components, and illustrate how each might be separately optimized to maximize power output. In a simple analytical example, we illustrate how these techniques might be used to gain insight into the tradeoffs in the design of the electronic hardware and the choice of bus voltage.

This paper presents the system design, construction, and testing of an active variable buoyancy system (VBS) actuator with applications to unmanned multi-domain vehicles. Unmanned multi-domain vehicles require nontraditional VBS designs because of their unique operation requirements. We present a VBS actuator design that targets multi-domain vehicle design objectives of high endurance, stealth, and underwater loitering. The design features a rigid ballast tank with an inner elastic bladder connected to a hydraulic pump and a proportionally controlled vent valve. The system working fluid is obtained from the ambient surrounding water and the elastic bladder separates the water from pressurized gas, thus preventing any gas from escaping during a venting operation. An analytic model of the VBS characterizing the system dynamics is derived. Ballast tank prototype design and construction is discussed. A VBS test platform vehicle is presented, featuring two ballast tanks, motor, pump, and RF receiver for control.

This work presents a numerical framework for the simulation and design of integrally actuated membrane wings with feedback control. The performance of the aeroelastic system are evaluated using a high-fidelity model. It consists in a fluid solver based on the direct numerical integration of the unsteady Navier-Stokes equations implicitly coupled with a geometrically non-linear dynamic structural model which has been calibrated using experimental data. The rate-dependent constitutive law for the dielectric elastomer considered for the integral wing actuation is based on a non-linear formulation. The framework also includes a methodology for the model reduction of the fully-coupled system. The resulting low-order description showed to retain the main system dynamics, and can therefore be used for the design of the control scheme for the wing. Results highlights the potential to achieve on-demand aerodynamics using the actuation concept proposed. In particular, it is shown that the wing aerodynamic performance is noticeably enhanced through the actuation and the disturbances on the lift in case of gusts can be reduced up to 60%.

This work presents the lessons learned from wind tunnel tests of a droop-nose morphing wingtip as part of the EU project NOVEMOR. The design followed a sequential chain and was largely driven through optimization tools, including a glass-fiber composite skin optimization tool and a topology optimization tool for the design of internal super-elastic and aluminium compliant mechanisms. The device was tested in the low speed tunnel at the University of Bristol to determine the structural response under aerodynamic loading. Measurements of strain from strain gauges show that the structure is capable of handing the aerodynamic loads though also show an imbalance of strain between the components. Measurements of surface pressures show a small variation of c^p with the 2° droop morphing variation as per the target. The wind tunnel testing showed that further developments to the design chain are necessary, in particular the need for a concurrent as opposed to sequential chain for the design of the various components. Considerations of other problem formulations, the inclusion of nonlinear finite element analysis, and ways to interpret the structural boundary of the topology optimization results with more confidence are required. The utilization of super-elastic materials in morphing structures may also prove to be highly beneficial for their performance.

Structural topology has a large impact on the flexural stiffness of a beam structure. Reversible attachment between discrete substructures allows for control of shear stress transfer between structural elements, thus stiffness modulation. Electrostatic adhesion has shown promise for providing a reversible latching mechanism for controllable internal connectivity. Building on previous research, a thin film copper polyimide laminate has been used to incorporate high voltage electrodes to Fibre Reinforced Polymer (FRP) sandwich structures. The level of electrostatic holding force across the electrode interface is key to the achievable level of stiffness modulation. The use of non-flat interlocking core structures can allow for a significant increase in electrode contact area for a given core geometry, thus a greater electrostatic holding force. Interlocking core geometries based on cosine waves can be Computer Numerical Control (CNC) machined from Rohacell IGF 110 Foam core. These Interlocking Core structures could allow for enhanced variable stiffness functionality compared to basic planar electrodes. This novel concept could open up potential new applications for electrostatically induced variable stiffness structures.

We investigate the nonlinear dynamics of magnetically coupled beams for multi-modal vibration energy harvesting. A multi-physics model for the proposed device is developed taking into account geometric and magnetic nonlinearities. The coupled nonlinear equations of motion are solved using the Galerkin discretization coupled with the harmonic balance method and the asymptotic numerical method. Several numerical simulations have been performed showing that the expected performances of the proposed vibration energy harvester are significantly promising with up to 130 % in term of bandwidth and up to 60 μWcm^-3g^-2 in term of normalized harvested power.

This article presents the modeling of nonlinear response of micro piezoelectric energy harvesters under amplified base excitation. The micro transducer is a composite cantilever beam made of the PZT thick film deposited on the stainless-steel substrate. The model is developed based on the Euler-Bernoulli beam theory considering geometric and inertia nonlinearities, and the reduced formulation is derived based on the Hamiltonian variational principle. The harmonic balance method is used to simulate the nonlinear frequency response under various magnitudes of excitation and electric loads. The hardening type of nonlinearity is predicted and is found to be in good agreement with experiment. However, the softening response is also observed in different samples fabricated under different conditions. Such disagreement is under investigation.

In this paper, we report an improved novel nonlinear energy harvester with optimized magnetic force. The piezoelectric beam is subject to magnetic force between tip magnet and external ferroic plate. The shape curve of the ferroic plate is designed to optimize the magnetic force in order to make the proposed nonlinear energy harvester have large well distance but small well depth, which offers a high energy orbit and thus large-amplitude motion for the harvester under small excitation level. The magnetic force-deflection curve is obtained experimentally and the potential curve is calculated to verify the well distance and depth. The experiment results show that the excitation level to maintain the large-amplitude motion and perturbation level to trigger the large-amplitude motion increase with the potential well distance and the well depth. With the optimal distance and depth, the maximal output power and output bandwidth of the nonlinear energy harvester increase significantly. Our study gives important guidance for the design of nonlinear energy harvester with certain input excitation level.

Intentionally designed nonlinearities have been employed by several research groups to enhance the frequency bandwidth of vibration energy harvesters. Another type of nonlinear resonance behavior emerges from the piezoelectric constitutive behavior for high excitation levels and is manifested in the form of softening stiffness. This material nonlinearity does not result in the jump phenomenon in soft piezoelectric ceramics, e.g. PZT-5A and PZT-5H, due to their large internal dissipation. This paper explores the potential for wideband energy harvesting using a hard (relatively high quality factor) PZT-8 bimorph by exploiting its material softening. A wide range of base excitation experiments conducted for a set of resistive electrical loads confirms the frequency bandwidth enhancement.

Multimodal passive damping of a mechanical structure can be implemented by a coupling to a secondary structure exhibiting similar modal properties. When considering a piezoelectric coupling, the secondary structure is an electrical network. A suitable topology for such a network can be obtained by a finite difference formulation of the mechanical equations, followed by a direct electromechanical analogy. This procedure is applied to the Kirchhoff-Love theory in order to find the electrical analogue of a clamped plate. The passive electrical network is implemented with inductors, transformers and the inherent capacitance of the piezoelectric patches. The electrical resonances are tuned to approach those of several mechanical modes simultaneously. This yields a broadband reduction of the plate vibrations through the array of interconnected piezoelectric patches. The robustness of the control strategy is evaluated by introducing perturbations in the mechanical or electrical designs. A non-optimal tuning is considered by way of a uniform variation of the network inductance. Then, the effect of local or boundary modifications of the electromechanical system is observed experimentally. In the end, the use of an analogous electrical network appears as an efficient and robust solution for the multimodal control of a plate.

Semi-active and active structural control systems are advanced mechanical devices and systems capable of high damping performance, ideal for mitigation of multi-hazards. The implementation of these devices within structural systems is still in its infancy, because of the complexity in designing a robust closed-loop control system that can ensure reliable and high mitigation performance. Particular challenges in designing a controller for multi-hazard mitigation include: 1) very large uncertainties on dynamic parameters and unknown excitations; 2) limited measurements with probabilities of sensor failure; 3) immediate performance requirements; and 4) unavailable sets of input-output during design. To facilitate the implementation of structural control systems, a new type of controllers with high adaptive capabilities is proposed. It is based on real-time identification of an embedding that represents the essential dynamics found in the input space, or in the sensors measurements. This type of controller is termed input-space dependent controllers (ISDC). In this paper, the principle of ISDC is presented, their stability and performance derived analytically for the case of harmonic inputs, and their performance demonstrated in the case of different types of hazards. Results show the promise of this new type of controller at mitigating multi-hazards by 1) relying on local and limited sensors only; 2) not requiring prior evaluation or training; and 3) adapting to systems non-stationarities.

This paper investigates an acoustic prism for continuous acoustic beam steering by a simple frequency sweep. This idea takes advantages of acoustic wave velocity shifting in metamaterials in the vicinity of local resonance. We apply this concept into the piezoelectric metamaterial consisting of host medium and piezoelectric LC shunt. Theoretical modeling and FEM simulations are carried out. It is shown that the phase velocity of acoustic wave changes dramatically in the vicinity of local resonance. The directions of acoustic wave can be adjusted continuously between 2 to 16 degrees by a simple sweep of the excitation frequency. Such an electro-mechanical coupling system has a feature of adjusting local resonance without altering the mechanical part of the system.

Feedback control strategies are desirable for disturbance rejection of human-induced vibrations in civil engineering structures as human walking forces cannot easily be measured. In relation to human-induced vibration control studies, most past researches have focused on floors and footbridges and the widely used linear controller implemented in the trials has been the direct velocity feedback (DVF) scheme. With appropriate compensation to enhance its robustness, it has been shown to be effective at damping out the problematic modes of vibration of the structures in which the active vibration control systems have been implemented. The work presented here introduces a disturbance observer (DOB) that is used with an outer-loop DVF controller. Results of analytical studies presented in this work based on the dynamic properties of a walkway bridge structure demonstrate the potential of this approach for enhancing the vibration mitigation performance offered by a purely DVF controller. For example, estimates of controlled frequency response functions indicate improved attenuation of vibration around the dominant frequency of the walkway bridge structure as well as at higher resonant frequencies. Controlled responses from three synthesized walking excitation forces on a walkway bridge structure model show that the inclusion of the disturbance observer with an outer loop DVF has potential to improve on the vibration mitigation performance by about 3.5% at resonance and 6-10% off-resonance. These are realised with hard constraints being imposed on the low frequency actuator displacements.

Hydrocarbon well operators deploy downhole reservoir monitoring equipment in order to optimize the rate at which hydrocarbons are extracted. Alternative power sources are sought that could be deployed in these harsh environments to replace or supplement standard power sources currently in use. To this end, a three phase proof-of-concept study was performed to gauge the feasibility of such a device. In the first phase a parametric study was performed to understand how high uncertainty variables affect the natural frequency of a producing hydrocarbon well. In a follow up study, the relationship between boundary conditions and system damping was investigated. In the second phase a structural housing was designed to satisfy American Petroleum Institute load cases. Using finite element models and standard tube/casing geometries, design pressures were iterated until a permissible housing design was achieved. This preliminary design provided estimates of the radial width and volume in which energy harvesting and storage elements may be situated. In the last phase a software program was developed to estimate the energy that might be harvested from user specified harvester configurations. The program is dependent on user input production tube accelerations; this permits well operators to use well-specific vibrational data as inputs to generate well-specific energy output estimates. Results indicate that a downhole energy harvesting tool is structurally feasible under reasonable operating conditions but no conclusions can be made as to the sufficiency of generated power as no in-situ acceleration time histories are available. Future work is discussed. Approved for publication, LA-UR-16-21193.

In the U.S., there are over 4 million miles (6 million km) of roadways and more than 250 million registered vehicles. The energy lost in the pavement system due to traffic-induced vibration and deformation is enormous. If effectively harvested, such energy can serve as an alternative sustainable energy source that can be easily integrated to the transportation system. The potential of PVDF, which is a piezoelectric polymer material, is investigated as a potential energy harvester integrated in pavement systems. The uniqueness of this study lies in that the electrical response of PVDF under coupled mechanical and thermal stimulations are studied. It is well known that most piezoelectric materials are also pyroelectric materials, which convert temperature change into electricity. However, the potential of PVDF as a hybrid piezo-pyroelectric energy harvester has been seldom studied. Through series of well controlled experiments, it is found that there exists interesting coupling phenomenon between piezoelectric and pyroelectric effects of PVDF: the voltage generated by simultaneous mechanical and thermal stimulations is the sum of voltages generated by separate stimulations. In addition, an estimation of power generation through piezoelectric and pyroelectric effect is conducted. Finally, the overall effects of temperature on hybrid piezo-pyroelectric energy harvesting are discussed.

This paper presents a review of piezoelectric based energy harvesting devices and their charge collection and storage electronics for use in very harsh environment of gun-fired munitions. A number of novel classes of such energy-harvesting power sources that have been developed for gun-fired munitions and similar applications, including one with integrated safety and firing setback event detection electronics and logic circuitry. The power sources are designed to harvest energy from firing acceleration and vibratory motions during the flight. As an example, the application of the developed piezoelectric based energy harvesting devices with event detection circuitry to the development of self-powered initiators or switching devices with full no-fire safety circuitry for protection against accidental drops, transportation vibration, and other similar low amplitude accelerations and/or high amplitude but short duration acceleration events is presented. The designs allow the use of a very small piezoelectric elements, thereby making such devices to be highly miniaturized. These devices can be readily hardened to withstand very high G firing setback accelerations in excess of 100,000 G and the harsh firing environments. The design of prototypes and testing in shock loading machines, air guns and actual firing are presented.

This paper investigates the opportunities of deploying distributed sensors within the manufacturing environment of a large scale automobile plant using energy harvesting techniques. Measurements were taken in three domains at the plant in order to characterize ambient energy. Due to the location of the plant, the RF power density for radio access technologies present varied between -127 dBm/cm² and -113 dBm/cm². The maximum temperature difference measured within accessible distance from machine parts on the production lines surveyed was 10°C. Indoor lighting was dominant at the plant via fluorescent tubes, with average irradiance of 1 W/m². The results obtained from this measurement campaign showed that indoor lighting was the most suitable ambient source for energy harvesting.

This paper explains the development of smart nanogrid systems for disaster mitigation employing deployable renewable energy harvesting, or Deployable Disaster Devices (D³), where wind turbines and solar panels are developed in modular forms, which can be tied together depending on the needed power. The D³ packages/units can be used: (1) as a standalone unit in case of a disaster where no source of power is available, (2) for a remote location such as a farm, camp site, or desert (3) for a community that converts energy usage from fossil fuels to Renewable Energy (RE) sources, or (4) in a community system as a source of renewable energy for grid-tie or off-grid operation. In Smart D³ system, the power is generated (1) for consumer energy needs, (2) charge storage devices (such as batteries, capacitors, etc.), (3) to deliver power to the network when the smart D³ nano-grid is tied to the network and when the power generation is larger than consumption and storage recharge needs, or (4) to draw power from the network when the smart D³ nano-grid is tied to the network and when the power generation is less than consumption and storage recharge needs. The power generated by the Smart D³ systems are routed through high efficiency inverters for proper DC to DC or DC to AC for final use or grid-tie operations. The power delivery from the D³ is 220v AC, 110v AC and 12v DC provide proper power for most electrical and electronic devices worldwide. The power supply is scalable, using a modular system that connects multiple units together. This are facilitated through devices such as external Input-Output or I/O ports. The size of the system can be scaled depending on how many accessory units are connected to the I/O ports on the primary unit. The primary unit is the brain of the system allowing for smart switching and load balancing of power input and smart regulation of power output. The Smart D³ systems are protected by ruggedized weather proof casings allowing for operation in a variety of extreme environments and can be parachuted into the needed locations. The Smart Nanogrid Systems will have sensors that will sense the environmental conditions for the wind turbines and solar panels for maximum energy harvesting as well as identifying the appliances in use. These signal will be sent to a control system to send signal to the energy harvester actuators to maximize the power generation as well as regulating the power, i.e., either send the power to the appliances and consumer devices or send the power to the batteries and capacitors for energy storage, if the power is being generated but there are no consumer appliances in use, making it a "smart nanogrid deployable renewable energy harvesting system."

Total Knee Replacement (TKR), one of the most common surgeries in the United States, is performed when the patient is experiencing significant amounts of pain or when knee functionality has become substantially degraded. Despite impressive recent developments, only about 85% of patients are satisfied with the pain reduction after one year. Therefore, structural health and performance monitoring are integral for intraoperative and postoperative feedback. In extension of the author's previous work, a new configuration for implementation of piezoelectric transducers in total knee replacement bearings is proposed and FEA modeling is performed to attain appropriate sensing and energy harvesting ability. The predicted force transmission ratio to the PZT (ratio of force applied to the bearing to force transferred to the embedded piezoelectric transducer) is about 6.2% compared to about 5% found for the previous encapsulated design. Dimensional parameters of the polyethylene bearing including the diameter and depth of the PZT pocket as well as the placement geometry of the PZT transducer within the bearing are hypothesized as the most influential parameters on the performance of the designed system. The results show a small change of 1% and 2.3% in the output of the system as a result of variation in the PZT location and pocket diameter, respectively. Whereas, the output of the system is significantly sensitive to the pocket depth; a pocket 0.01 mm deeper than the PZT transducer leads to no force transmission, and a pocket 0.15 mm shallower leads to full load transmission to the PZT. In order to develop a self-powered sensor, the amount of energy harvested from tibial forces for the proposed geometry is investigated.

An energy harvester in the road pavement made from a piezoelectric composite plate is designed and studied to collect energy from the passing vehicles for the ice melting aim. Piezoelectric material has the ability to produce electric charge on its surface when strain takes place due to any external loading. Based on this property, a rectangular composite plate harvester is developed consisting of piezoelectric material as the energy generation coating layer and A514 steel as the substrate layer to realize the energy harvesting process from the variable pressure generated in the road pavement by passing vehicles. Based on Westergaards stress model, a numerical model is developed to calculate the three dimensional stress distribution in the pavement. Numerical simulations are conducted to study the optimization of various parameters of the harvester, such as depth of the harvester in the pavement, length and width as well as thicknesses of piezoelectric layer and the substrate. By taking in to consideration the maximum stress that can be sustained by both of the piezoelectric material and also the substrate material, an optimum design of the piezoelectric couple composite plate energy harvester is suggested. It is seen that the maximum output power, which can be generated by a single patch of 0.2m*0.2m*0.0026m dimension with a vehicle passing at 22.2 m/s, can reach up to 23.36 W. With the well-designed pavement energy harvesters, it is feasible to collect enough energy to rise the temperature of the ice with the thickness of 1cm covering a 5m width road by 20 degree Celsius within 2.5 hours. This technique can be applied to melt the ice on the roads and bridges especially in cold countries.

This study aims to investigate the effect of using magnetorheological elastomer (MRE)-based adaptive tuned vibration absorbers (ATVA) on the sound transmission in an elastic plate. Sound transmission loss (STL) of an elastic circular thin plate is analytically studied. The plate is excited by a plane acoustic wave as an incident sound and the displacement of the plate is calculated using corresponding mode shapes of the system for clamped boundary condition. Rayleigh integral approach is used to express the transmitted sound pressure in terms of the plate’s displacement modal amplitude. In order to increase sound transmission loss of the plate, the MRE-based ATVA is considered. The basic idea is to be able to change the stiffness of the ATVA by varying magnetic field in order to reduce the transmitted acoustic energy of the host structure in a wide frequency range. Here, a MRE-based ATVA under the shear mode consisting of an oscillator mass, magnetic conductor, coils and MRE is investigated. In order to predict the viscoelastic characteristics of the field-dependent MRE based on the applied magnetic field, the double pole model is used. Finally, MRE-based ATVAs are integrated with the plate to absorb the plate energy with the aim of decreasing the transmitted sound power. Results show that plate with integrated MRE-based ATVAs suppresses the axisymmetric vibration of the plate and thus considerably improves the STL. Parametric studies on the influence of the position of MRE-based ATVAs and the effects of applied current on their performance are also presented.

In this paper, magneto-rheological (MR) mount for a cabin of heavy equipment vehicles is designed for improving vibration isolation in both low and high frequency domains. The proposed mount consists of two principal parts of mount, rubber part and MR fluid path. The rubber part of existed mount and spring are used to change the stiffness and frequency characteristics for low vibration frequency range. The MR fluid path is a valve type structure using flow mode. In order to control the external magnetic field, a solenoid coil is placed in MR mount. Magnetic intensity analysis is then conducted to optimize dimensions using computer simulation. Experimental results show that magnetic field can reduce low frequency vibration. The results presented in this work indicate that proper application of MR fluid and rubber characteristic to devise MR mount can lead to the improvement of vibration control performance in both low and high frequency ranges.

A new magnetic field intensity measurement method using resonance principle is proposed in this paper. The proposed magnetic field sensor consists of magneto rheological (MR) fluid placed between two collocated, piezo-bounded, metallic, circular disc mounted face to face in the z-axis. The resonant frequency of the disc is changed by the magnetic field dependent viscosity of the MR fluid. The key enabling concept in this work is stiffening the circular metal disc using the rheological effect of MR fluid i.e. resonant frequency varies with respect to magnetic field strength. The change in resonant frequency is measured using simple closed loop electronics connected between the two piezo crystals. The analytical model of the vibrating circular discs with MR fluid placed at the center is derived and the results are validated with experimentation. The proposed magnetic flux density measurement concept is novel and it is found to have better sensitivity and linearity.

The requirements for transmission and coupling elements in hybrid powertrains are rising continuously. On this occasion a novel clutch-design is investigated and validated in this contribution. The transmission of power is based on magnetorheological fluids (MRF) including a fluid movement control for enabling a drag torque-free operation for an increased energy efficient operation. Drag losses in powertrains are a serious deficiency for an energy-efficient application. MRFs are highly qualified for the utilization in powertrains considering their particular characteristics of changing their apparent viscosity significantly under influence of a magnetic field by fast switching times and a smooth torque control. The proposed MRF-clutch with three different variations of the fluid movement control is designed based on a numerical model and validated by experimental measurements with a realized prototype. The main aspects during the investigation are focused on the coupling functions under the influence of high rotational speeds up to 6000 min-1 and also the safety behavior of the different variations by the fluid control in case of a system failure. The theoretical and experimental investigation demonstrates the suitability for an integration of clutches based on MRF in electrical or hybrid powertrains as an alternative to conventional coupling elements.

This study shows an optimum structure of a seismic isolation floor against horizontal ground motions. Although a seismic isolation floor is effective with vibration reduction, the response of the floor becomes larger when excited by long-period ground motions. It is shown that caster equipment move and suffer damage in a seismic isolation structure by an experiment. Moreover, the permissible displacement of the floor is limited. Therefore, the focus is on an active seismic isolation. About active control, the system cannot operate without power supply. To solve these problems an energy regeneration is considered in our previous study. These studies only analyze simple model and did not choose the suitable structure for active control and energy regeneration. This research propose a new structure which has regenerated energy exceeds the energy required for the active control by numerical simulation.

This study aims to develop a design principle of a nonlinear dynamic vibration absorber focusing on its robustness against the alteration of the natural frequency of the primary system. To this end, a 2-DOF coupled system consisting of the primary and absorber systems is analytically solved to evaluate the maximally possible level of the displacement response of the primary system by means of averaging method. In this approach, the equation of motion of the vibration absorber is first solved in the steady-state by the averaging method for a given amplitude of the primary system assuming that the whole responses of the coupled system have the same frequency as the excitation force. Then, the equivalent dynamic stiffness of the dynamic absorber is derived which represents how the absorber acts on the primary system in reaction of the displacement of the primary system. Because the maximally possible displacement amplitude of the primary system is enveloped by the reciprocal of the imaginary part of the equivalent dynamic stiffness, the benefit of introducing a softening effect into the design of the dynamic absorber is theoretically suggested, and validated through numerical simulations.

The urgent train braking could bring structural response menace to the bridge under passive control. Based on the analysis of breaking dynamics of a train-bridge vibration system, a magnetorheological elastomeric bearing (MRB) whose mechanical parameters are adjustable is designed, tested and modeled. A finite element method (FEM) is carried out to model and optimize a full scale vibration isolation system for railway bridge based on MRB. According to the model above, we also consider the effect of different braking stop positions on the vibration isolation system and classify the bridge longitudinal vibration characteristics into several cases. Because the train-bridge vibration isolation system has multiple vibration states and strongly coupling with nonlinear characteristics, a human-simulated intelligent control (HSIC) algorithm for isolating the bridge vibration under the impact of train braking is proposed, in which the peak shear force of pier top, the displacement of beam and the acceleration of beam are chosen as control goals. The simulation of longitudinal vibration control system under the condition of train braking is achieved by MATLAB. The results indicate that different braking stop positions significantly affect the vibration isolation system and the structural response is the most drastic when the train stops at the third cross-span. With the proposed HSIC smart isolation system, the displacement of bridge beam and peak shear force of pier top is reduced by 53.8% and 34.4%, respectively. Moreover, the acceleration of bridge beam is effectively controlled within limited range.

In late years, many base isolated structures are planned as the seismic design, because they suppress vibration response significantly against large earthquake. To achieve greater safety, semi-active or active vibration control system is installed in the structures as earthquake countermeasures. Semi-active and active vibration control systems are more effective than passive vibration control system to large earthquake in terms of vibration reduction. However semi-active and active vibration control system cannot operate as required when external power supply is cut off. To solve the problem of energy consumption, we propose a self-powered active seismic isolation floor which achieve active control system using regenerated vibration energy. This device doesn’t require external energy to produce control force. The purpose of this study is to propose the seismic isolation device having charging function and to optimize the control system and passive elements such as spring coefficients and damping coefficients using genetic algorithm. As a result, optimized model shows better performance in terms of vibration reduction and electric power regeneration than the previous model. At the end of this paper, the experimental specimen of the proposed isolation device is shown.

this paper, a novel semi-active magnetorheological tuned liquid column damper (MR-TLCD) device combining tuned liquid column damper (TLCD) and magnetorheological damper (MRD) is devised for wind or earthquake vibration control of civil structures. In this device, a traditional moving head loss in the TLCD is replaced with a controlled MRD in the bottom or one side of the vertical column, which can easily and rapidly adjust the damping of the device. A semi-active experimental prototype MR-TLCD consisting of a shear rotary MRD and a TLCD is built. Based on the four basic presumptions, a dynamic model of the devised MR-TLCD is established using the Lagrange equation. In this equation, the formula of MRD employs the Bingham Boltzmann model. The natural frequency of the MR-TLCD is determined by the total central length and spring stiffness. It is worth noting that the natural frequency differs with the simple TLCD, because the device adds a joint spring. An equivalent linear damping expression is developed under harmonic excitation, and its mechanical model is developed using the equivalent period displacement and the coulomb friction force of MRD. At the same time, the equivalent damping can be adjusted by the real-time applied current, which can achieve the semi-active control performance. To validate the proposed frequency and damping model, Experimental test is conducted on a section area 150mm × 150mm and a total length 2.24m of the MR-TLCD dimensions. Comparisons are made between predicted and measured TLCD liquid surface displacement motion. The result shows the error of its nature frequency is only 2.29%.

A major goal of structural health monitoring (SHM) is to provide accurate and responsive detection and monitoring of flaws. This research work reports an investigation of SPES sensors for damage detection, investigating different sensor sizes and how they affect the sensor’s signal. A sensor able to monitor structural change that can be remotely interrogated and does not need a power supply is presented in this work. The SPES-sensor presents the great advantage of monitoring conductive and non-conductive structures such as fiberglass-reinforced composites (FRC) and carbon fiber-reinforced polymers (CFRP). Any phenomena that affect the magnetic field of the SPES can be detected and monitored. A study was conducted to investigate the capability of sensor to give information on structural changes, simulated by the presence of an external mass placed in the proximity of sensor. Effect of different positions of the SPES within the sample, and how to extend the area of inspection using multiple sensors was investigated. The sensor was tested embedded in the samples, simulating the structural change on both sides of the sample. In both configurations the sensor described herein demonstrated a great potential to monitor structural changes.

In this paper we present experimental results about preliminary activity related to the control of seismic attenuators and inertial platforms using monolithic accelerometer sensors based on folded pendulum mechanical scheme. Apart the compactness and robustness of monolithic implementations of folded pendulums, the main advantages of this kind of sensors are the tune-ability of their resonance frequency and their high sensitivity over a large measurement band. In this preliminary test we show that the main resonant frequencies of the inertial platform, located in the frequency band 0.01 ± 10Hz, can be controlled using open loop monolithic folded pendulums as inertial sensors. The results are presented and discussed in this paper together with the planned further developments and improvements.

This paper proposes a problem-solving method for the stroke limitation problem, which is related to auxiliary masses of active mass damper systems for high-rise buildings. The proposed method is used in a new simple control system for the active mass dampers mimicking the motion of bipedal mammals, which has a neural oscillator synchronizing with the acceleration response of structures and a position controller. In the system, the travel distance and direction of the auxiliary mass of the active mass damper is determined by reference to the output of the neural oscillator, and then, the auxiliary mass is transferred to the decided location by using a PID controller. The one of the purpose of the previouslyproposed system is stroke restriction problem avoidance of the auxiliary mass during large earthquakes by the determination of the desired value within the stroke limitation of the auxiliary mass. However, only applying the limited desired value could not rigorously restrict the auxiliary mass within the limitation, because the excessive inertia force except for the control force produced by the position controller affected on the motion of the auxiliary mass. In order to eliminate the effect on the auxiliary mass by the structural absolute acceleration, a cancellation method is introduced by adding a term to the control force of the position controller. We first develop the previously-proposed system for the active mass damper and the additional term for cancellation, and verity through numerical experiments that the new system is able to operate the auxiliary mass within the restriction during large earthquakes. Based on the comparison of the proposed system with the LQ system, a conclusion was drawn regarding which the proposed neuronal system with the additional term appears to be able to limit the stroke of the auxiliary mass of the AMD.

We present a novel thermal energy harvesting system using triboelectric effect. Recently, there has been intensive research efforts on energy harvesting using triboelectric effect, which can produce surprising amount of electric power (when compared to piezoelectric materials) by rubbing or touching (i.e, electric charge by contact and separation) two different materials together. Numerous studies have shown the possibility as an attractive alternative with good transparency, flexibility and low cost abilities for its use in wearable device and smart phone applications markets. However, its application has been limited to only vibration source, which can produce sustained oscillation with maintaining contact and separation states repeatedly for triboelectric effect. Thus, there has been no attempt toward thermal energy source. The proposed approach can convert thermal energy into electricity by pairing triboelectric effect and active ferromagnetic materials The objective of the research is to develop a new manufacturing process of design, fabrication, and testing of a Magneto-Thermo-Triboelectric Generator (MTTG). The results obtained from the approach show that MTTG devices have a feasible power energy conversion capability from thermal energy sources. The tunable design of the device is such that it has efficient thermal capture over a wide range of operation temperature in waste heat.

In this study, we demonstrate the concept of a new hybrid energy harvesting system by combing solar cells with magneto-thermoelectric generator (MTG, i.e., thermal energy harvesting). The silicon solar cell can easily reach high temperature under normal operating conditions. Thus the heated solar cell becomes rapidly less efficient as the temperature of solar cell rises. To increase the efficiency of the solar cell, air or water-based cooling system is used. To surpass conventional cooling devices requiring additional power as well as large working space for air/water collectors, we develop a new technology of pairing an active thermal backplane (ATB) to solar cell. The ATB design is based on MTG technology utilizing the physics of the 2nd order phase transition of active ferromagnetic materials. The MTG is cost-effective conversion of thermal energy to electrical energy and is fundamentally different from Seebeck TEG devices. The ATB (MTG) is in addition to being an energy conversion system, a very good conveyor of heat through both conduction and convection. Therefore, the ATB can provide dual-mode for the proposed hybrid energy harvesting. One is active convective and conductive cooling for heated solar cell. Another is active thermal energy harvesting from heat of solar cell. These novel hybrid energy harvesting device have potentially simultaneous energy conversion capability of solar and thermal energy into electricity. The results presented can be used for better understanding of hybrid energy harvesting system that can be integrated into commercial applications.

In this work, a new type of haptic master featuring small-sized MR brake is proposed and its performances are evaluated. The proposed haptic master consists of base frame, stick grip and small-sized four MR brakes for 3-DOF rotational motion and 1-DOF gripper motion. To obtain large braking torque under limited small size of MR brake, dual tapered shape inner magnetic core is proposed and its performance is evaluated via both numerical estimation and experimental test. After design and implementation of control algorithm, it has been demonstrated through experiment that the proposed actuator has good performances on tracking control of desired torques. Then, a new haptic master device is designed and constructed by adopting the proposed MR brakes and light weight frame structures. It is verified that the proposed haptic master device is effective for the real application in the field.

The paper presents the wave propagation in one-dimensional metamaterial bar with attached group of non-linear local oscillators by using analytical and numerical models. The focus is on the influence of group of non-linear cells on the filtering properties of the bar in the 1000Hz to 2000Hz range. Group of Periodic cells with alternating properties exhibit interesting dynamic characteristics that enable them to act as filters. Waves can propagate along bars within specific bands of frequencies called pass bands, and attenuate within bands of frequencies called gaps. Gaps in structures with group of periodic cells are located according on the frequency of cells. From the cell, we can yield the effect negative stiffness and effect negative mass. We can also design the gaps from attached oscillators or cells. In the uniform case the gap is located around the resonant frequency of the oscillators, and thus a stop band can be created in the lower frequency range. In the case with group of non-linear cells the results show that the position of the gap can be designed, and the design depends on the amplitude and the degree of non-linear cells.

Magnetorheological dampers (MRDs), a semi-active actuator based on MR effect, have great potential in vibration/shock control systems. However, it is difficult to establish its inverse model due to its intrinsic strong nonlinear hysteresis behaviors, and sequentially the precise, fast and effective control could not be realized effectively. This paper presents an inverse model for MRDs based on a restructured phenomenological model with incorporation of the "normalization" concept. The proposed inverse model of MRDs is validated by the simulation of the force tracking. The research results indicate that the inverse model could be applied for the damping force control with consideration of the strong nonlinear hysteresis behaviors of the MRDs.

Various damages might occur during the solid rocket motor (SRM) manufacturing/operational phase, and the debonding of propellant/insulator/composite case interfaces is one of damage types which determine the life of a motor. The detection of such interface debonding damage will be beneficial for developing techniques for reliable nondestructive evaluation (NDE) and structural health monitoring (SHM). Piezoelectric sensors are widely used for structural health monitoring technique. In particular, electromechanical impedance (EMI) techniques give simple and low-cost solutions for detecting damage in various structures. In this work, piezoelectric EMI structural health monitoring technique is applied to identify the debonding condition of propellant/insulator interface structure using finite element method and experimental investigation. A three-dimensional coupled field finite element model is developed using the software ANSYS and the harmonic analysis is conducted for high-frequency impedance analysis procedure. In the experimental study, the impedance signals were measured from PZT and MFC sensors outside attached to composite case monitoring the different debonding conditions between the propellant and insulator. Root mean square deviation (RMSD) based damage index is conducted to quantify the changes i n impedance for different de bonding conditions and frequency range. Simulation and experimental results confirmed that the EMI technique can be used effectively for detecting the debonding damage in SRM and is expected to be useful for future application of real SRM’s SHM.

This paper describes the design and experimental investigation of a self-reconfigurable icosahedral robot for locomotion. The robot consists of novel and modular tensegrity structures, which can potentially maneuver in unstructured environments while carrying a payload. Twisted and Coiled Polymer (TCP) muscles were utilized to actuate the tensegrity structure as needed. The tensegrity system has rigid struts and flexible TCP muscles that allow keeping a payload in the central region. The TCP muscles provide large actuation stroke, high mechanical power per fiber mass and can undergo millions of highly reversible cycles. The muscles are electrothermally driven, and, upon stimulus, the heated muscles reconfigure the shape of the tensegrity structure. Here, we present preliminary experimental results that determine the rolling motion of the structure.

We propose a method to analyze and design a laminated MRE bearing, in which the optimal parameters of materials and mechanical structure of the MRE bearing are determined. Based on the multi-scale and magneto-mechanical coupling theories, we establish a comprehensive model for the MRE bearing considering the influence of particle volume fraction, particle distribution, and thickness of MRE laminated layers on its mechanical performance. Within the micro-scale analysis, the representative volume unit (RVU) is used to address the effect of particle volume fraction and distribution on mechanical and magnetic properties of MRE itself. Within the macro-scale analysis, we build both mechanical and magnetic models for the laminated MRE bearing. Based on the theoretical analysis, a laminated MRE bearing with four-layer MRE is designed and fabricated. The performance of the MRE bearing has been tested by using MTS test bench. The results are compared with that of model analysis. It demonstrates that the proposed method can be a useful tool in the development of laminated-MRE bearings for practical applications.

Nonlinear internal resonance mechanism is exploited in piezoelectric vibration energy harvesting (PVEH) for the purpose of broadening the resonance band. Conventional linear energy harvester has narrow operating bandwidth. In this research, a buckled piezoelectric beam structure with preload under transverse excitation is investigated to demonstrate the superiority of internal resonance. The condition for 2:1 internal resonance could be established by truncating the continuum beam with geometrical nonlinearity. Integro–partial–differential equations are derived for governing transverse motion measured from a stable equilibrium position. At specific initial axial compressive force, two modes are coupled through the internal resonance interaction. For weak nonlinear perturbations, multiple scales method is used to explore the amplitude-frequency responses of the buckled beam system under primary resonance with 2:1 internal resonance. Numerical examples demonstrate that the resonance bandwidth is broadened thanks to the coexistence of softening and hardening nonlinear characteristics. Moreover, validity of the approximate analytical method is demonstrated by comparing with simulation. Furthermore, the optimal resistance is discussed with a pure resistive load. This research on the internal resonance of buckled beam provides a basis for structure design and optimization in broadband PVEH.

To supply power to wireless sensor networks, a type of broadband electromagnetic vibration energy harvester (VEH) using bistable vibration scavenging structure is proposed. It consists of a planar spring, an electromagnetic transducer with an annular magnetic circuit, and a coil assembly with a ferrite bobbin inside. A nonlinear magnetic force respecting to the relative displacement is generated by the ferrite bobbin, and to broaden the working frequency bandwidth of the VEH. Moreover, the ferrite bobbin increases the magnetic flux linkage gradient of the coil assembly in its moving region, and further to improve its output voltage. The dynamic behaviors of the VEH are analyzed and predicted by finite element analysis and ODE calculation. Validation experiments are carried out and show that the VEH can harvest high energy in a relatively wide excitation frequency band. The further test shows that the load power of the VEH with a load resistor of 90Ω can reach 10mW level in a wide frequency bandwidth when the acceleration level of the harmonic excitation is 1g. It can ensure the intermittent work of many sensors as well as wireless communication modules at least.

Pyroshock or pyrotechnic shock generated by explosive events of pyrotechnic devices can induce fatal failures in electronic payloads. Therefore, understanding and estimation of pyroshock propagation through complex structures are necessary. However, an experimental approach using real pyrotechnic devices is quite burdensome because pyrotechnic devices can damage test structures and newly manufactured test structures are necessary for each experiment. Besides, pyrotechnic experiments are quite expensive, time-consuming, and dangerous. Consequently, nondestructive evaluation (NDE) of pyroshock propagation without using real pyrotechnic devices is necessary. In this study, nondestructive evaluation technique for pyroshock propagation estimation using hydrocodes is proposed. First, pyroshock propagation is numerically analyzed using AUTODYN, a commercial hydrocodes. Hydrocodes can handle stress wave propagation including elastic, plastic, and shock wave in the time domain. Test structures are modeled and pyroshock time history is applied to where the pyroshock propagation originates. Numerical NDE results of pyroshock propagation on test structures are analyzed in terms of acceleration time histories and acceleration shock response spectra (SRS) results. To verify the proposed numerical methodology, impact tests using airsoft gun are performed. The numerical analysis results for the impact tests are compared with experimental results and they show good agreements. The proposed numerical techniques enable us to nondestructively characterize pyroshock propagation.

In this paper we address the chattering phenomenon which is a common drawback associated with the normal Sliding Mode Control (SMC) law for a basic shape memory alloy (SMA) actuated system. A new method has been proposed to counter this effect by combining the concepts of Fast Terminal SMC and Dynamic controller. A phenomenological model is developed for the SMA which incorporates a piecewise linear hysteresis behavior. This model is used for both open loop as well as closed loop simulations for a linear motion control system. Based on this model, a dynamic terminal sliding mode control law is derived and applied to the system. A normal SMC law with saturation function which is known to reduce chattering is compared with the proposed control law for its effectiveness to curb the issue of chattering versus its ability to faithfully track a desired trajectory. Numerical Simulations indicate that the proposed law is able to reduce the chattering effect sufficiently and at par with the control technique involving saturation function.

The capabilities of distributed sensor systems such as marine wildlife telemetry tags could be significantly enhanced through the integration of photovoltaic modules. Photovoltaic cells could be used to supplement the primary batteries for wildlife telemetry tags to allow for extended tag deployments, wherein larger amounts of data could be collected and transmitted in near real time. In this article, we present experimental results used to validate and improve key aspects of our original model for sub-surface solar power. We discuss the test methods and results, comparing analytic predictions to experimental results. In a previous work, we introduced a model for sub-surface solar power that used analytic models and empirical data to predict the solar irradiance available for harvest at any depth under the ocean's surface over the course of a year. This model presented underwater photovoltaic transduction as a viable means of supplementing energy for marine wildlife telemetry tags. The additional data provided by improvements in daily energy budgets would enhance the temporal and spatial comprehension of the host's activities and/or environments. Photovoltaic transduction is one method that has not been widely deployed in the sub-surface marine environments despite widespread use on terrestrial and avian species wildlife tag systems. Until now, the use of photovoltaic cells for underwater energy harvesting has generally been disregarded as a viable energy source in this arena. In addition to marine telemetry systems, photovoltaic energy harvesting systems could also serve as a means of energy supply for autonomous underwater vehicles (AUVs), as well as submersible buoys for oceanographic data collection.

Nanocoating is the result of a coating application of nanomaterials to build a consistent network of molecules in a paint to protect the surfaces of various materials and devices. Hexagonal Boron Nitride (h-BN) is in two dimensional form with excellent thermal, mechanical and chemical properties. These BN nanocoatings are also a thermally insulating material for heat management. After adding functionalized h-BNs into paints or other coatings, they will absorb the harmful UV part of sunlight and prevent coating against the environmental degradations. The impacts of the environmental factors on the coatings can be substantially eliminated. In the present study, h-BNs were modified with [2-(2-Aminoethylamino) propyl] trimethoxysilane and uniformly dispersed into the polyurethane coatings with different amounts, such as 0.1, 0.2, 0.4, and 0.8wt% to increase hardness and water resistance, and decrease the UV degradation level of coatings and transparent plastics. The prepared samples were characterized by using Fourier Transform Infrared Spectroscopy (FTIR), UV-Vis Spectroscopy, Scanning Electron Microscope (SEM), Water Contact Angle, and Differential Scanning Calorimeter (DSC). The test results showed that the nanocoatings with functionalized h-BN provided excellent physical and chemical behaviors against the UV and other physical degradations on the substrates.