This PDF file contains the front matter associated with SPIE Proceedings Volume 9431, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

In this work we explore efficient transformation of broadband wave energy into low-power electricity using patterned polymer piezoelectrics integrated with an Elliptical Acoustic Mirror (EAM) configuration. The mirror under consideration features a semi-elliptical continuous mirror with a rectangular arrangement of harvesting material overlapping the geometrical focus of the mirror. Spatial and temporal transformation of the wave propagation field into the frequency-wavenumber domain is performed in order to identify the wavenumber content inside the mirror region. A frequency-domain Root-Mean-Square (RMS) evaluation is then applied in order to guarantee broadband harvesting characteristics to the resulting Distributed Harvester (DH). Computational modeling and experimental testing are employed to quantify performance enhancement of the presented approach in the 20-120 kHz range, where broadband focusing characteristics of the continuous EAM are confirmed experimentally. Additionally the patterned configuration with proper wiring results in substantial power enhancement over 20-60 kHz, i.e. the neighborhood of the center frequency used in its Fourier transform-based design.

In the last decade there has been an increasing attention on the use of highly- and weakly- nonlinear solitary waves in engineering and physics. These waves can form and travel in nonlinear systems such as one-dimensional chains of spherical particles. One engineering application of solitary waves is the fabrication of acoustic lenses, which are employed in a variety of fields ranging from biomedical imaging and surgery to defense systems and damage detection. In this paper we propose to couple an acoustic lens to a wafer-type lead zirconate titanate transducer (PZT) to harvest energy from the vibration of an object tapping the lens. The lens is composed of a circle array made of chains of particles in contact with a polycarbonate material where the nonlinear waves coalesce into linear waves. The PZT located at the designed focal point converts the mechanical energy carried by the stress wave into electricity to power a load resistor. The performance of the designed harvester is compared to a conventional cantilever beam, and the experimental results show that the power generated with the nonlinear lens has the same order of magnitude of the beam.

Hydraulic pressure energy harvesters (HPEH) are devices that convert the dynamic pressure within hydraulic systems into usable electrical power through axially loaded piezoelectric stacks excited off-resonance by the fluid. Within hydraulic systems, the dominant frequency is typically a harmonic of the pump operating frequency. The pressure fluctuations coupled with the piezoelectric stack can be amplified by creating a housing design that includes a Helmholtz resonator tuned to the dominant frequency of the fluid excitation. A Helmholtz resonator is an acoustic device that consists of a cavity coupled to a fluid medium via a neck, or in this case a port connection to the fluid flow, that acts as an amplifier when within the bandwidth of its resonance. The implementation of a piezoelectric stack within the HPEH allows for a Helmholtz resonator to be included within the fluidic environment despite the significantly higher than air static pressures typical of fluid hydraulic systems (on the order of one to tens of MPa). The resistive losses within the system, such as from energy harvesting and viscous losses, can also be used to increase the bandwidth of the resonance; thus increasing the utility of the device. This paper investigates the design, modeling, and performance of hydraulic pressure energy harvesters utilizing a Helmholtz resonator design.

This paper investigates analytical modeling and experimental validation of Ultrasonic Acoustic Energy Transfer (UAET) for low-power electricity transfer to exploit in wireless applications ranging from medical implants to underwater sensor systems. A piezoelectric receiver bar is excited by incident acoustic waves originating from a source of known strength located at a specific distance from the receiver. The receiver is a free-free piezoelectric cylinder operating in the 33- mode of piezoelectricity with a fundamental resonance frequency above the audible frequency range. In order to extract the electrical power output, the piezoelectric receiver bar is shunted to a generalized resistive-reactive circuit. The goal is to quantify the electrical power delivered to the load (connected to the receiver) in terms of the source strength. Experimental validations are presented along with parameter optimization studies. Sensitivity of the electrical power output to the excitation frequency in the neighborhood of the receiver’s underwater resonance frequency, source-to-receiver distance, and source-strength level are reported. Resistive and resistive-reactive electrical loading cases are discussed for performance enhancement and frequency-wise robustness. Simulations and experiments reveal that the presented multiphysics analytical model for UAET can be used to predict the coupled system dynamics with very good accuracy.

This article presents the possibility of energy scavenging (ES) utilizing the physics of acousto-elastic metamaterial (AEMM) and use them in a dual mode (Acoustic Filter and Energy Harvester), simultaneously. Concurrent wave filtering and energy harvesting mechanism is previously presented using local resonance phenomenon in phononic crystal, however energy harvesting capabilities of AEMM is not reported extensively. Traditionally acoustic metamaterials are used in filtering acoustic waves by trapping or guiding the acoustic energy, whereas this work presents that the trapped dynamic energy inside the soft constituent (matrix) of metamaterials can be significantly harvested by strategically embedding piezoelectric wafers in the matrix. With unit cell model, we asserted that at lower acoustic frequencies maximum power in the micro Watts (~36μW) range can be generated, which is significantly higher than the existing harvesters of same kind. Efficient energy scavengers at low acoustic frequencies are almost absent due to large required size relevant to the acoustic wavelength. In this work we propose sub wave length scale energy scavengers utilizing the coupled physics of local, structural and matrix resonances. Upon validation of the argument through analytical, numerical and experimental studies, a broadband energy scavenger (ES) with multi-cell model is designed with varying geometrical properties.

A prosthetic knee for above-knee (AK) amputees is categorized into two types; namely a passive and an active type. The passive prosthetic knee is generally made by elastic materials such as carbon fiber reinforced composite material, titanium and etc. The passive prosthetic knee easy to walk. But, it has disadvantages such that a knee joint motion is not similar to ordinary people. On the other hand, the active prosthetic knee can control the knee joint angle effectively because of mechanical actuator and microprocessor. The actuator should generate large damping force to support the weight of human body. But, generating the large torque using small actuator is difficult. To solve this problem, a semi-active type prosthetic knee has been researched. This paper proposes a semi-active prosthetic knee using a flow mode magneto-rheological (MR) damper for AK amputees. The proposed semi-active type prosthetic knee consists of the flow mode MR damper, hinge and prosthetic knee body. In order to support weight of human body, the required energy of MR damper is smaller than actuator of active prosthetic leg. And it can control the knee joint angle by inducing the magnetic field during the stance phase.

This study presents a theoretical investigation of a flexible, electromagnetically controlled microchannel transport system (i.e., controllable micropump) utilizing a soft magnetorheological elastomer. A two-dimensional time-dependent model using a coupled fluid-solid-magnetic analysis is developed to conduct a parametric study on a system which consists of a flexible channel and valves. Effect of different geometric, magnetic and mechanical properties on the performance of the system is investigated through the net generated flow. It is demonstrated that the microchannel diameter, elastic foundation constant, elastic modulus of the microchannel and the valves, fluid viscosity, and the applied magnetic field have significant effect on the net generated flow.

Drag losses in the powertrain are a serious deficiency for any energy-efficient application, especially for hybrid electrical vehicles. A promising approach for fulfilling requirements like efficiency, wear, safety and dynamics is the use of an innovative MRF-based clutch design for the transmission of power that is based on magnetorheological fluids (MRF). MRF are smart fluids with the particular characteristics of changing their apparent viscosity significantly under influence of the magnetic field. Their characteristics are fast switching times and a smooth torque control in the powertrain. In this paper, a novel clutch concept is investigated that facilitates the controlled movement of the MRF from an active torque-transmitting region into an inactive region of the shear gap. This concept enables a complete disengagement of the fluid engaging surfaces in a way that viscous drag torque can be eliminated. Therefore, a simulation based design for such MRF-based clutches is used to design the required magnetic excitation systems for enabling a well-defined safety behavior by the fluid control. Based on this approach, an MRF-based clutch is developed in detail which provides a loss-reduced alternative to conventional disengagement devices in the powertrain. The presented MRF-based clutch enables a investigation of different systems in one design by changing the magnetic excitation. Especially, different possibilities for the fail-safe behavior of the MRF-based clutch are considered to ensure a well-defined condition in electrical or hybrid powertrains in case of a system failure.

In this paper, we investigate the feasibility of energy harvesting from axisymmetric vibrations of annular ionic polymer metal composites (IPMCs). We consider an in-house fabricated IPMC that is clamped at its inner radius to a moving base and is free at its outer radius. We propose a physics-based model for energy harvesting from underwater vibrations, in which the IPMC is described as a thin annular plate undergoing axisymmetric vibrations with an added mass due to the encompassing fluid. Experiments are performed to elucidate the effect of the shunting resistance and the excitation frequency on energy harvesting.

In this work, Macro-Fiber Composite (MFC)-based piezoelectric structures are employed for underwater mechanical base excitation (vibration energy harvesting) and electrical biomimetic actuation in bending operation at low frequencies. The MFC technology (fiber-based piezoelectric composites with interdigitated electrodes) exploits the effective 33-mode of piezoelectricity and strikes a balance between structural deformation and force levels for actuation to use in underwater locomotion, in addition to offering high power density for energy harvesting to enable battery-less underwater sensors. Following in-air electroelastic composite model development, it is aimed to establish semianalytical models that can predict the underwater dynamics of thin MFC cantilevers for different length-to-width aspect ratios. In-air analytical electroelastic dynamics of MFCs is therefore coupled with added mass and nonlinear hydrodynamic damping effects of fluid to describe the underwater electrohydroelastic dynamics in harvesting and actuation. To this end, passive plates of different aspect ratios are tested to extract and explore the repeatability of the inertia and drag coefficients in Morison’s equation. The focus is placed on the first two bending modes in this semianalytical approach. Additionally, nonlinear dependence of the output power density to aspect ratio is characterized theoretically and experimentally in the underwater base excitation problem.

This paper proposes a multifunctional compliant structure that can harvest electrical power from both incident sunlight and ambient mechanical energy including wind flow or vibration. The energy harvesting device consists of a slender, ribbon-like, flexible thin film solar cell that is laminated with piezoelectric patches. The harvester is mounted in longitudinal tension and subjected to a transverse wind flow to excite flow-induced aeroelastic vibrations. This paper formulates an analytic model of the bending dynamics of the device. We present a Transfer Matrix formulation that also accounts for the changes in natural frequencies and mode shapes of the system when subjected to axial loads in a beam. It also observed that mode shape obtained using TMM formulation shows numerical stability even for very high tensile loads providing results consistent with the geometric boundary conditions applied at the ends of a beam. This article also discusses about structurally modeling a piezo - solar energy harvester using TMM methodology, where a thin clampedclamped solar film is bonded with piezo patches having a much higher bending stiffness. Additionally, the effect of axial tension on the mode shape of the thin host structure of the piezo-solar ribbon is presented and it is shown how this tension can be used advantageously to affect the strain distribution of the entire structure and introduce higher strains at the piezo patches.

Galloping phenomenon has attracted extensive research attention for small-scale wind energy harvesting. In the reported literature, the dynamics and harvested power of a galloping-based energy harvesting system are usually evaluated with a resistive AC load; these characteristics might shift when a practical harvesting interface circuit is connected for extracting useful DC power. In the family of piezoelectric energy harvesting interface circuits, synchronized switching harvesting on inductor (SSHI) has demonstrated its advantage for enhancing the harvested power from existing base vibrations. This paper investigates the harvesting capability of a galloping-based wind energy harvester using SSHI interfaces, with a focus on comparing the performances of Series SSHI (S-SSHI) and Parallel SSHI (P-SSHI) with that of a standard DC interface, in terms of power at various wind speeds. The prototyped galloping-based piezoelectric energy harvester (GPEH) comprises a piezoelectric cantilever attached with a square-sectioned bluff body made of foam. Equivalent circuit model (ECM) of the GPEH is established and system-level circuit simulations with SSHI and standard interfaces are performed and validated with wind tunnel tests. The benefits of SSHI compared to standard circuit become more significant when the wind speed gets higher; while SSHI circuits lose the benefits at small wind speeds. In both experiment and simulation, the superiority of P-SSHI is confirmed while S-SSHI demands further investigation. The power output is increased by 43.75% with P-SSHI compared to the standard circuit at a wind speed of 6m/s.

There have been a number of new applications for energy harvesting with the ever-decreasing power consumption of microelectronic devices. In this paper we explore a new area of marine animal energy harvesting for use in powering tags known as bio-loggers. These devices record data about the animal or its surroundings, but have always had limited deployment times due to battery depletion. Reduced solar irradiance below the water's surface provides the impetus to explore other energy harvesting concepts beyond solar power for use on marine animals. We review existing tag technologies in relation to this application, specifically relating to energy consumption. Additionally, we propose a new idea for energy harvesting, using hydrostatic pressure changes as a source for energy production. We present initial testing results of a bench-top model and show that the daily energy harvesting potential from this technology can meet or exceed that consumed by current marine bio-logging tags. The application of this concept in the arena of bio-logging technology could substantially increase bio-logger deployment lifetimes, allowing for longitudinal studies over the course of multiple breeding and/or migration cycles.

A new energy harvester, based on the fluttering phenomenon, is presented. The device is done with a wing connected to a support via two elastomers. When a fluid in motion impinges on this elastic structure, an amount of kinetic energy is transferred to the system, inducing large amplitude oscillations if few mechanical parameters are correctly set. In order to transform the mechanical energy in electrical energy, an electromagnetic coupling is adopted. In this way, it is possible to produce several mW in a wind of 4 m/s with a centimeter-sized device. The device is conceived as an autonomous power source for distributed sensors to be used in Internet of Things.

By combining the physical principles behind the nastic plant movements and the rich designs of paper folding art, we propose a new class of multi-functional adaptive structure called fluidic origami cellular structure. The basic elements of this structure are fluid filled origami "cells", made by connecting two compatible Miura-Ori stripes along their crease lines. These cells are assembled seamlessly into a three dimensional topology, and their internal fluid pressure or volume are strategically controlled just like in plants for nastic movements. Because of the unique geometry of the Miura-Ori, the relationships among origami folding, internal fluid properties, and the crease bending are intricate and highly nonlinear. Fluidic origami can exploit such relationships to provide multiple adaptive functions concurrently and effectively. For example, it can achieve actuation or morphing by actively changing the internal fluid volume, and stillness tuning by constraining the fluid volume. Fluidic origami can also be bistable because of the nonlinear correlation between folding and crease material bending, and such bistable character can be altered significantly by fluid pressurization. These functions are natural and essential companions with respect to each other, so that fluidic origami can holistically exhibit many attractive characteristics of plants and deliver rapid and efficient actuation/morphing while maintaining a high structural stillness. The purpose of this paper is to introduce the design and working principles of the fluidic origami, as well as to explore and demonstrate its performance potential.

This paper describes the design and experimental analysis of novel artificial muscles, made of twisted and coiled nylon fibers, for powering a biomimetic robotic hand. The design is based on circulating hot and cold water to actuate the artificial muscles and obtain fast finger movements. The actuation system consists of a spring and a coiled muscle within a compliant silicone tube. The silicone tube provides a watertight, expansible compartment within which the coiled muscle contracts when heated and expands when cooled. The fabrication and characterization of the actuating system are discussed in detail. The performance of the coiled muscle fiber in embedded conditions and the related characteristics of the actuated robotic finger are described.

Trees exploit intriguing mechanisms such as multimodal frequency distributions and nonlinearities to distribute and dampen the aerodynamically-induced vibration energies to which they are subjected. In dynamical systems, these mechanisms are comparable to the internal resonance phenomenon. In recent years, researchers have harnessed strong nonlinearities, including internal resonance, to induce energetic dynamics that enhance performance of vibration energy harvesting systems. For trees, the internal resonance-like dynamics are evidently useful damping mechanisms in spite of the high variation associated with excitation and structural parameters. Yet for dynamic systems, studies show narrow operating regimes which exhibit internal resonance-based behaviors, suggesting that the energetic dynamics may be deactivated if stochastic inputs corrupt ideal excitation properties. To address these issues, this research evaluates the opportunities enabled by exploiting nonlinear, multimodal motions in an L-shaped energy harvester platform. The system dynamics are probed analytically, numerically, and experimentally for comprehensive insights on the versatility of internal resonance-based behaviors for energy harvesting. It is found that although activating the high amplitude nonlinear dynamics to enhance power generation is robust to significant additive noise in the harmonic excitations, parameter sensitivities may pose practical challenges in application. Discussion is provided on means to address such concerns and on future strategies that may favorably exploit nonlinearity and multimodal dynamics for robust energy harvesting performance.

Piezoelectric transducers are widely employed in vibration-based energy harvesting schemes. Simple piezoelectric cantilever for energy harvesting is uni-directional and has bandwidth limitation. In this research we explore utilizing internal resonances to harvest vibratory energy due to excitations from an arbitrary direction with the usage of a single piezoelectric cantilever. Specifically, it is identified that by attaching a pendulum to the piezoelectric cantilever, 1:2 internal resonances can be induced based on the nonlinear coupling. The nonlinear effect induces modal energy exchange between beam bending motion and pendulum motions in 3-dimensional space, which ultimately yield multidirectional energy harvesting by a single cantilever. Systematic analysis and experimental investigation are carried out to demonstrate this new concept.

Linear cantilevered piezoelectric energy harvesters do not typically operate efficiently through a large span of excitation frequencies. Beam theory dictates optimum displacement at resonance excitation; however, typical environments evolve and vary over time with no clear dominant frequency. Nonlinear, non-resonant harvesting techniques have been implemented, but none so far have embraced chaotic behavior as a desirable property of the system. This work aims to benefit from chaotic phenomena by stabilizing high energy periodic orbits located within a chaotic attractor to improve operating bandwidth. Delay coordinate embedding is used to reconstruct the system states from a single time series measurement of displacement. Orbit selection, local linearization, and control perturbation are all computed from the single time series independent of an explicit system model. Although chaos in non-autonomous systems is typically associated with harmonic inputs, chaotic attractor motion can also exist throughout other excitation sources. Accelerometer data from inside a commercial vehicle and a stochastic excitation signal are used to illustrate the existence of chaos in dynamic environments, allowing such environments to be likely candidates for the proposed bandwidth improving energy harvesting technique.

For a nonlinear beam-mass system used to harvest vibratory energy, the two-mode approximation of the response is computed and compared to the single-mode approximation of the response. To this end, the discretized equations of generalized coordinates are developed and studied using a computational method. By obtaining phase-portraits and time-histories of the displacement and voltage, it is shown that the strong nonlinearity of the system affects the system dynamics considerably. By comparing the results of single- and two-mode approximations, it is shown that the number of mode shapes affects the dynamics of the response. Varying the tip-mass results in different structural configurations namely linear, pre-buckled nonlinear, and post-buckled nonlinear configurations. The nonlinear dynamics of the system response are investigated for vibrations about static equilibrium points arising from the buckling of the beam. Furthermore, it is demonstrated that the harvested power is affected by the system configuration.

This article investigates a horizontal diamagnetic levitation (HDL) system for vibration energy harvesting. In this configuration, two large magnets, alias lifting magnets, are arranged co-axially at a distance such that in between them a magnet, alias floating magnet, is passively levitated at a laterally offset equilibrium position. The levitation is stabilized in the horizontal direction by two diamagnetic plates made of pyrolytic graphite placed on each side of the floating magnet. This HDL configuration permits large amplitude vibration of the floating magnet and exploits the ability to tailor the geometry to meet specific applications due to its frequency tuning capability. Theoretical modeling techniques are discussed followed by an experimental setup to validate it. At an input root mean square (RMS) acceleration of 0.0434 m/s² (0.0044 g_rms) and at a resonant frequency of 1.2 Hz, the prototype generated a RMS power of 3.6 μW with an average system efficiency of 1.93%. Followed by the validation, parametric studies on the geometry of the components are undertaken to show that with the optimized parameters the efficiency can be further enhanced.

A novel piezoelectric energy harvesting device is presented in this paper. Different from the existing designs, the proposed apparatus is based on the principle of nonlinear energy sink (NES) in order to achieve broadband energy harvesting. First, the concept of the proposed design is described. Then the system modeling and parameter identification are addressed. The transient responses and voltage output performance of the apparatus are examined through an experimental study. The study shows that the proposed apparatus behaves similarly as the NES with the following features: initial energy dependence, 1:1 resonance, targeted energy transfer, etc. Broadband voltage output is achieved when NES is activated.

Bistable systems have recently been employed for vibration energy harvesting owing to their favorable dynamic characteristics and desirable response for wideband excitation. In this paper, we investigate the use of bistable harvesters to extract energy from spinning wheels. The proposed harvester consists of a piezoelectric cantilever beam that is mounted on a rigid spinning hub and carries a tip mass in the form of a permanent magnet. Magnetic repulsion forces from an opposite magnet cause the beam to possess two stable equilibrium positions. Inter-well lead-lag oscillations caused by rotation in a vertical plane provide a good source for energy extraction. The design offers frequency tuning, as the centrifugal forces strain the harvester, thereby increasing its natural frequency to cope with a variable rotational speed. This has applications in self-powered sensors mounted on spinning wheels, such as tire pressure monitoring sensors. An effort is made to select the design parameters to enable the harvester to exhibit favorable inter-well oscillations across a range of rotational speeds for enhanced energy harvesting. Findings of the present work are verified both numerically and experimentally.

Unmanned Aerial Vehicles are prime targets for morphing implementation as they must adapt to large changes in flight conditions associated with locally varying wind or large changes in mass associated with payload delivery. The Spanwise Morphing Trailing Edge concept locally varies the trailing edge camber of a wing or control surface, functioning as a modular replacement for conventional ailerons without altering the spar box. Utilizing alternating active sections of Macro Fiber Composites (MFCs) driving internal compliant mechanisms and inactive sections of elastomeric honeycombs, the SMTE concept eliminates geometric discontinuities associated with shape change, increasing aerodynamic performance. Previous work investigated a representative section of the SMTE concept and investigated the effect of various skin designs on actuation authority. The current work experimentally evaluates the aerodynamic gains for the SMTE concept for a representative finite wing as compared with a conventional, articulated wing. The comparative performance for both wings is evaluated by measuring the drag penalty associated with achieving a design lift coefficient from an off-design angle of attack. To reduce experimental complexity, optimal control configurations are predicted with lifting line theory and experimentally measured control derivatives. Evaluated over a range of off-design flight conditions, this metric captures the comparative capability of both concepts to adapt or “morph” to changes in flight conditions. Even with this simplistic model, the SMTE concept is shown to reduce the drag penalty due to adaptation up to 20% at off-design conditions, justifying the increase in mass and complexity and motivating concepts capable of larger displacement ranges, higher fidelity modelling, and condition-sensing control.

Wing twisting has been shown to improve aircraft flight performance. The potential benefits of a twisting wing are often outweighed by the mass of the system required to twist the wing. Shape memory alloy (SMA) actuators repeatedly demonstrate abilities and properties that are ideal for aerospace actuation systems. Recent advances have shown an SMA torsional actuator that can be manufactured and trained with the ability to generate large twisting deformations under substantial loading. The primary disadvantage of implementing large SMA actuators has been their slow actuation time compared to conventional actuators. However, inductive heating of an SMA actuator allows it to generate a full actuation cycle in just seconds rather than minutes while still . The aim of this work is to demonstrate an experimental wing being twisted to approximately 10 degrees by using an inductively heated SMA torsional actuator. This study also considers a 3-D electromagnetic thermo-mechanical model of the SMA-wing system and compare these results to experiments to demonstrate modeling capabilities.

There is currently an interest in developing mobile sensing platforms that fly indoors. The primary goal for these platforms is to be able to successfully navigate a building under various lighting and environmental conditions. There are numerous research challenges associated with this goal, one of which is the platform’s ability to detect and identify the presence of transparent barriers. Transparent barriers could include windows, glass partitions, or skylights. For example, in order to successfully navigate inside of a structure, these platforms will need to sense if a space contains a transparent barrier and whether or not this space can be traversed. This project’s focus has been developing a multimodal sensing system that can successfully identify such transparent barriers under various lighting conditions while aboard a mobile platform. Along with detecting transparent barriers, this sensing platform is capable of distinguishing between reflective, opaque, and transparent barriers. It will be critical for this system to be able to identify transparent barriers in real-time in order for the navigation system to maneuver accordingly. The properties associated with the interaction between various frequencies of light and transparent materials were one of the techniques leveraged to solve this problem.

The aim of this paper is to present two control logics and an attitude estimator for UAV stabilization and remote piloting, that are as robust as possible to physical parameters variation and to other external disturbances. Moreover, they need to be implemented on low-cost micro-controllers, in order to be attractive for commercial drones. As an example, possible applications of the two switching control logics could be area surveillance and facial recognition by means of a camera mounted on the drone: the high computational speed logic is used to reach the target, when the high-stability one is activated, in order to complete the recognition tasks.

Tailless airplanes with swept wings rely on variations of the spanwise lift distribution to provide controllability in roll, pitch and yaw. Conventionally, this is achieved utilizing multiple control surfaces, such as elevons, on the wing trailing edge. As every flight condition requires different control moments (e.g. to provide pitching moment equilibrium), these surfaces are practically permanently displaced. Due to their nature, causing discontinuities, corners and gaps, they bear aerodynamic penalties, mostly in terms of shape drag. Shape adaptation, by means of chordwise morphing, has the potential of varying the lift of a wing section by deforming its profile in a way that minimizes the resulting drag. Furthermore, as the shape can be varied differently along the wingspan, the lift distribution can be tailored to each specific flight condition. For this reason, tailless aircraft appear as a prime choice to apply morphing techniques, as the attainable benefits are potentially significant. In this work, we present a methodology to determine the optimal planform, profile shape, and morphing structure for a tailless aircraft. The employed morphing concept is based on a distributed compliance structure, actuated by Macro Fiber Composite (MFC) piezoelectric elements. The multidisciplinary optimization is performed considering the static and dynamic aeroelastic behavior of the resulting structure. The goal is the maximization of the aerodynamic efficiency while guaranteeing the controllability of the plane, by means of morphing, in a set of flight conditions.

Vibration-based energy harvesting using a disk-type piezoelectric bimorph with thickness poled circular piezoelectric laminates is explored theoretically and experimentally. The bimorph disk consists of two circular laminates electrically connected in series and shunted through the outer surface electrodes to an electrical load for characterizing the power output and piezoelectrically shunted vibration in response to base excitation. The bimorph disk with free edge conditions is mounted to the vibrating base from its center and the focus is placed on the fundamental axisymmetric vibration mode. Electromechanical coupling is introduced to the distributed-parameter model of the thin circular plate and a resistive load is considered across the electrodes. Following a modal analysis-based electroelastic solution, closed-form expressions are obtained for the voltage output and shunted vibration frequency response functions by accounting for the two-way coupling in the presence of a finite electrical load impedance. Experimental validations of the electroelastic model are given for two separate bimorph disks of different diameters.

Electronic devices are high demand commodities in today’s world, and such devices will continue increasing in popularity. Currently, batteries are implemented to provide power to these devices; however, the need for battery replacement, their cost, and the waste associated with battery disposal present a need for advances in self-powered technology. Energy harvesting technology has great potential to alleviate the drawbacks of batteries. In this work, a novel piezoelectret foam material is investigated for low-level energy harvesting. Specifically, piezoelectret foam assembled in a multilayer stack configuration is explored. Modeling and experimentation of the stack behavior when excited in compression at low frequencies are performed to investigate piezoelectret foam as a multilayer energy harvester. An examination of modeling piezoelectret foam as a stack with an equivalent circuit is made following recently published work and is used in this study. A 20-layer prototype device is fabricated and experimentally tested via harmonic base excitation. Electromechanical testing is performed by compressing the foam stack to obtain output electrical energy; consequently, allowing the frequency response between input mechanical energy and output electrical energy to be developed. Modeling results are compared to the experimental measurements to assess the fidelity of the model. Lastly, energy harvesting experimentation in which the device is subject to harmonic base excitation at the natural frequency is conducted to determine the ability of the piezoelectret foam stack to successfully charge a capacitor.

This paper presents the design, simulation, assembly and testing of a force-compensated hydrogel-based pH sensor. In the conventional deflection method, a piezoresistive pressure sensor is used as a chemical-mechanical-electronic transducer to measure the volume change of a pH-sensitive hydrogel. In this compensation method, the pH-sensitive hydrogel keeps its volume constant during the whole measuring process, independent of applied pH value. In order to maintain a balanced state, an additional thermal actuator is integrated into the close-loop sensor system with higher precision and faster dynamic response. Poly (N-isopropylacrylamide) (PNIPAAm) with 5 mol% monomer 3-acrylamido propionic acid (AAmPA) is used as the temperature-sensitive hydrogel, while poly (vinyl alcohol) with poly (acrylic acid) (PAA) serves as the pH-sensitive hydrogel. A thermal simulation is introduced to assess the temperature distribution of the whole microsystem, especially the temperature influence on both hydrogels. Following tests are detailed to verify the working functions of a sensor based on pH-sensitive hydrogel and an actuator based on temperature-sensitive hydrogel. A miniaturized prototype is assembled and investigated in deionized water: the response time amounts to about 25 min, just half of that one of a sensor based on the conventional deflection method. The results confirm the applicability of t he compensation method to the hydrogel-based sensors.

Fluidic Actuated Flow Control (FAFC) has been introduced as a technology that influences the boundary layer by actively blowing air through slots or holes in the aircraft skin or wind turbine rotor blade. Modern wing structures are or will be manufactured using composite materials. In these state of the art systems, AFC actuators are integrated in a hybrid approach. The new idea is to directly integrate the active fluidic elements (such as SJAs and PJAs) and their components in the structure of the airfoil. Consequently, the integration of such fluidic devices must fit the manufacturing process and the material properties of the composite structure. The challenge is to integrate temperature-sensitive active elements and to realize fluidic cavities at the same time. The transducer elements will be provided for the manufacturing steps using roll-to-roll processes. The fluidic parts of the actuators will be manufactured using the MuCell® process that provides on the one hand the defined reproduction of the fluidic structures and, on the other hand, a high light weight index. Based on the first design concept, a demonstrator was developed in order to proof the design approach. The output velocity on the exit was measured using a hot-wire anemometer.

Conventional seismic design of reinforced concrete structures relies on yielding of steel reinforcement to dissipate energy while undergoing residual deformations. Therefore, reinforced concrete structures subjected to strong earthquakes experience large permanent displacements and are prone to severe damage or collapse. Shape memory alloys (SMAs) have gained increasing acceptance in recent years for use in structural engineering due to its attractive properties such as high corrosion resistance, excellent re-centering ability, good energy dissipation capacity, and durability. SMAs can undergo large deformations in the range of 6-8% strain and return their original undeformed position upon unloading. Due to their appealing characteristics, SMAs have been considered as an alternative to traditional steel reinforcement in concrete structures to control permanent deformations. However, the behavior of SMAs in combination with concrete has yet to be explored. In particular, the bond strength is important to ensure the composite action between concrete and SMA reinforcements. This study investigates the bond behavior between SMA bars and concrete through pull-out tests. To explore the size effect on bond strength, the tests are performed using various diameters of SMA bars. For the same diameter, the tests are also conducted with different embedment length to assess the effect of embedment length on bond properties of SMA bars. To monitor the slippage of the SMA reinforcement, an optical Digital Image Correlation method is used and the bond-slip curves are obtained.

Shape Memory Alloys (SMA’s) are known as actuators with very high energy density. This fact allows for the construction of very light weight and energy-efficient systems. In the field of material handling and automated assembly process, the avoidance of big moments of inertia in robots and kinematic units is essential. High inertial forces require bigger and stronger robot actuators and thus higher energy consumption and costs. For material handling in assembly processes, many different individual grippers for various work piece geometries are used. If one robot has to handle different work pieces, the gripper has to be exchanged and the assembly process is interrupted, which results in higher costs. In this paper, the advantages of using high energy density Shape Memory Alloy actuators in applications of material-handling and gripping-technology are explored. In particular, light-weight SMA actuated prototypes of an adaptive end-effector and a vacuum-gripper are constructed via rapid-prototyping and evaluated. The adaptive end-effector can change its configuration according to the work piece geometry and allows the handling of multiple different shaped objects without exchanging gripper tooling. SMA wires are used to move four independent arms, each arm adds one degree of freedom to the kinematic unit. At the tips of these end-effector arms, SMA-activated suction cups can be installed. The suction cup prototypes are developed separately. The flexible membranes of these suction cups are pulled up by SMA wires and thus a vacuum is created between the membrane and the work piece surface. The self-sensing ability of the SMA wires are used in both prototypes for monitoring their actuation.

Since shape memory alloy (SMA) actuators can generate large force per unit weight, they are expected as one of the next generation actuators for aircraft. To keep a position of conventional control surfaces or morphing wings with SMA actuators, the SMA actuators must keep being heated, and the heating energy is not small. To save the energy, a new control method proposed for piezoelectric actuators utilizing hysteresis in deformation [Ikeda and Takahashi, Proc. SPIE 8689 (2013), 86890C] is applied to an antagonistic SMA system. By using the control method any position can be an equilibrium point within hysteresis of stress-strain diagrams. To confirm a feasibility of the control method, a fundamental experiment is performed. The SMA wires are heated by applying electric current to the wires. When a pulsed current is applied to the two SMA wires alternately, the equilibrium position changes between two positions alternately, and when a series of pulse whose amplitude increases gradually is applied to one SMA wire, the equilibrium position changes like a staircase. However, just after the pulse the position returns slightly, that is, overshoot takes place. To investigate such a behavior of the system, numerical simulation is also performed. The one-dimensional phase transformation model [Ikeda, Proc. SPIE 5757 (2005), 344-352] is used for a constitutive model of the SMA wires. The simulated result agrees with the experiment qualitatively, including the overshoot. By examining volume fraction of each phase, it is found that the overshoot is caused by that austenite phase transforms into stress-induced martensite phase during the cooling process after the pulse.

This paper presents an experimental and theoretical analysis of a novel metamaterial-inspired distributed vibration suppression system. The proposed research takes advantage of uniquely designed cantilevered zigzag structures that can have natural frequencies orders of magnitude lower than a simple cantilever of the same scale. A key advantage of the proposed vibration suppression system is that the dynamic response of each zigzag structure can be made highly nonlinear with the use of magnets. Arrays of these compact linear and nonlinear zigzag structures are integrated into a host structure to form what is referred to here as a metastructure. The proposed and experimentally validated analytical model employs a Rayleigh-Ritz formulation for a linear metastructure represented as a cantilever beam with a distributed array of attached single degree of freedom oscillators. These attached oscillators are lumped parameter representations of the zigzag structures. Experimental modal analysis results are shown comparing the response of the nonlinear metastructure to that of both the linear metastructure and also to the host structure with no vibration suppression. Results show that the linear system can reduce the maximum response of the host structure by 41.0% while the nonlinear system can achieve over twice that with a reduction of 84.5%. These promising preliminary results provide motivation for future work to be focused on developing nonlinear metastructures for vibration suppression.

In damping devices involving piezoelectric elements, a single piezoelectric patch cannot consistently achieve multimodal control because of charge cancellation or vibration node location. In order to sense and control structural vibration on a prescribed frequency range, a solution consists in using an array of several piezoelectric patches being small compared to the smallest wavelength to control. Then, as an extension of the tuned mass damper strategy, a passive multimodal control requires to implement a damping system whose modes are as close as possible to those of the controlled structure. In this way, the electrical equivalent of the discretized mechanical structure represents the passive network that optimizes the energy transfer between the two media. For one-dimensional structures, a periodic distribution in several unit cells enables the use of the transfer matrix method applied on electromechanical state-vectors. The optimal passive networks are obtained for the propagation of longitudinal and transverse waves and a numerical implementation of the coupled behavior is performed. Compared to the more classical resonant shunts, the network topology induces promising multimodal damping and a reduction of the needed inductance. It is thus possible to create a completely passive electrical structure as it is demonstrated experimentally by using only purely passive components.

Smart fiber placement is an ambitious topic in current research for automated manufacturing of large-scale composite structures, e.g. wing covers. Adaptive systems get in focus to obtain a high degree of observability and controllability of the manufacturing process. In particular, vibrational issues and material failure have to be studied to significantly increase the production rate with no loss in accuracy of the fiber layup. As one contribution, an adaptive system has been developed to be integrated into the fiber placement head. It decouples the compaction roller from disturbances caused by misalignments, varying components’ behavior over a large work area and acceleration changes during operation. Therefore, the smart system axially adapts the position of the compaction roller in case of disturbances. This paper investigates the behavior of the system to compensate quasi-static deviations from the desired path. In particular, the compensation efficiency of a constant offset, a linear drift with constant gradient and a single-curved drift is studied. Thus, the test bed with measurement devices and scenarios is explained. Based on the knowledge obtained by the experimental data, the paper concludes with a discussion of the proposed approach for its use under operating conditions and further implementation.

In this paper, two Piezo-Based Rotating Inertial Actuators (PBRIAs) are considered for the suppression of the structureborne noise radiated from rotating machinery. Each inertial actuator comprises a piezoelectric stack element shunted with the Antoniou’s gyrator circuit. This type of electrical circuit can be used to emulate a variable inductance. By varying the shunt inductance it is possible to realize two tuneable vibration neutralizers in order to suppress single frequency vibrations of a slowly rotating shaft. As a consequence, reductions in the sound radiated from the machine housing can be also achieved. First a theoretical study is performed using a simplified lumped parameter model of the system at hand. The simplified model consists of a rotating shaft and two perpendicularly mounted shunted PBRIAs. Secondly, the shunted PBRIA is tested on an experimental test bed comprising a rotating shaft mounted in a frame. The noise is radiated by a plate that is attached to the frame. The experimental results show that a reduction of 11 dB on the disturbance force transmitted from the rotating shaft through the bearing to the housing can be achieved. This also generates a reduction of 9 dB for the plate vibration and the radiated noise.

The knee replacement is the second most common orthopedic surgical intervention in the United States, but currently only 1 in 5 knee replacement patients are satisfied with their level of pain reduction one year after surgery. It is imperative to make the process of knee replacement surgery more objective by developing a data driven approach to ligamentous balance, which increases implant life. In this work, piezoelectric materials are considered for both sensing and energy harvesting applications in total knee replacement implants. This work aims to embed piezoelectric material in the polyethylene bearing of a knee replacement unit to act as self-powered sensors that will aid in the alignment and balance of the knee replacement by providing intraoperative feedback to the surgeon. Postoperatively, the piezoelectric sensors can monitor the structural health of the implant in order to perceive potential problems before they become bothersome to the patient. Specifically, this work will present on the use of finite element modeling coupled with uniaxial compression testing to prove that piezoelectric stacks can be utilized to harvest sufficient energy to power sensors needed for this application.

The synchronized switch interface circuits, e.g., synchronized switch harvesting on inductor (SSHI), can significantly enhance the harvesting capability of piezoelectric energy harvesting (PEH) systems. In these power conditioning circuits, the piezoelectric voltage is flipped with respect to a bias voltage at the instants when the piezoelectric element is at maximum deforming positions. Voltage peak detection and in time switching action are required for implementing these functions. The state-of-the-art solutions are mostly realized by electronic methods, i.e., both functions are carried out by electronic comparators and electronic switches. However, the peak detectors usually introduce switching phase lag; while the electronic switches function only when the vibration magnitude is above a threshold level. When the vibration is lower than such threshold, the SSHI interface shows no improvement. In this paper, we propose a mechanical solution for constructing the self-powered SSHI interface for PEH systems. This technique is realized by installing a low cost vibration sensor switch (VSS) at the free end of a piezoelectric cantilever. It senses the maximum deflecting places of the cantilever and automatically carries out synchronized switching actions. Compared to the existing electronic solutions, this mechanical solution is compact and has relative low switching threshold. Therefore, with this self-powered solution, the advantage of SSHI interface circuit can be sufficiently released, in particular, at low level vibration. Experiment shows the feasibility of this mechanical solution. The advantages and limitations are also discussed in this paper.

Intrinsic localized modes (ILMs) are localized vibrational responses that may occur in a variety of nonlinear periodic systems. Many investigations have characterized the existence and stability of ILMs and they have been realized in systems representing numerous domains and length scales. Previous studies indicate that ILMs strongly interact with an impurity via attraction or repulsion from the damage location. In this research to exploit such phenomena for structural damage identification, we analyze the interaction of an ILM with multiple impurities, where a steered impurity strategically guides the ILM towards another, static impurity representative of damage. We discover and catalog the distinct phenomenological interaction types between steered ILMs and damage. For some interaction types, the ILM propagation rate temporarily exceeds a threshold, a behavior that is shown to consistently coincide with ILM interaction with damage (the static impurity). The quantitatively distinct interaction types are used to devise a method to effectively identify damage in the nonlinear periodic structure. Numerous studies are performed to assess the viability and accuracy of the proposed damage identification method and to examine its robustness to random structural heterogeneity. Beyond stiffness change, the proposed method is applicable to monitoring other system characteristics, such as changing mass or multi-field features, which may be representative of damage or static impurity.

Electroelastic and dissipative nonlinearities of commonly used soft piezoelectrics (PZT-5A and PZT-5H) are pronounced in various engineering applications such as actuation, sensing, vibration control, and most recently, in energy harvesting from dynamical systems. The present work investigates the nonlinear nonconservative dynamic behavior of bimorph piezoelectric cantilevers under low-to-high excitation levels with a focus on most popular soft piezoceramics: PZT-5A and PZT-5H. A unified mathematical framework we recently developed is analyzed by using the method of harmonic balance to identify and validate nonlinear system parameters based on a set of rigorous experiments for different samples.

Magneto-rheological (MR) fluids have been utilized in devices like orthoses and prostheses to generate controllable braking torque. In this paper, a flat shape rotary MR brake is designed for powered knee orthosis to provide adjustable resistance. Multiple disk structure with interior inner coil is adopted in the MR brake configuration. In order to increase the maximal magnetic flux, a novel internal structure design with smooth transition surface is proposed. Based on this design, a parameterized model of the MR brake is built for geometrical optimization. Multiple factors are considered in the optimization objective: braking torque, weight, and, particularly, average power consumption. The optimization is then performed with Finite Element Analysis (FEA), and the optimal design is obtained among the Pareto-optimal set considering the trade-offs in design objectives.

In the field of medicine, several new areas have been currently introduced such as robot-assisted surgery. However, the major drawback of these systems is that there is no tactile communication between doctors and surgical sites. When the tactile system is brought up, telemedicine including telerobotic surgery can be enhanced much more than now. In this study, a new tactile device is designed using a single magnetorhological (MR) sponge cell to realize the sensation of human organs. MR fluids and an open celled polyurethane foam are used to propose the MR sponge cell. The viscous and elastic sensational behaviors of human organs are realized by the MR sponge cell. Before developing the tactile device, tactile sensation according to touch of human fingers are quantified in advance. The finger is then treated as a reduced beam bundle model (BBM) in which the fingertip is comprised of an elastic beam virtually. Under the reduced BBM, when people want to sense an object, the fingertip is investigated by pushing and sliding. Accordingly, while several magnitudes of magnetic fields are applied to the tactile device, normal and tangential reaction forces and bending moment are measured by 6-axis force/torque sensor instead of the fingertip. These measured data are used to compare with soft tissues. It is demonstrated that the proposed MR sponge cell can realize any part of the organ based on the obtained data.

This paper presents a novel force modeling for an incision surgery into tissue and its haptic application for a surgeon. During the robot-assisted incision surgery, it is highly urgent to develop the haptic system for realizing sense of touch in the surgical area because surgeons cannot sense sensations. To achieve this goal, the force modeling related to reaction force of biological tissue is proposed in the perspective on energy. The force model describes reaction force focused on the elastic feature of tissue during the incision surgery. Furthermore, the force is realized using calculated information from the model by haptic device using magnetorheological fluid (MRF). The performance of realized force that is controlled by PID controller with open loop control is evaluated.

The technologies related to saving energy/or green vehicles are actively researched. In this tendency, the problem for reducing exhausted gas is in development with various ways. Those efforts are directly related to the operation of engine which emits exhausted gas. The auto start/stop of vehicle engine when a vehicle stop at road is currently as a main stream of vehicle industry resulting in reducing exhausted gas. However, this technology automatically turns on and off engine frequently. This motion induces vehicle engine to transmit vibration of engine which has large displacement, and torsional impact to chassis. These vibrations causing uncomfortable feeling to passengers are transmitted through the steering wheel and the gear knob. In this work, in order to resolve this vibration issue, a new proposed magnetorheological (MR) fluid based engine mount (MR mount in short) is presented. The proposed MR mount is designed to satisfy large damping force in various frequency ranges. It is shown that the proposed mount can have large damping force and large force ratio which is enough to control unwanted vibrations of engine start/stop mode.

This paper proposes a driver assistance device to notify vehicle drivers an optimal gear shifting timing considering fuel consumption in manual transmission vehicles. The haptic cue function of the proposed gear shifting assistance device is utilizing magnetorheological (MR) clutch mechanism as haptic interface between driver and vehicle. The shear stress level and hysteretic behavior of the employed MR fluid are experimentally observed and identified with the Preisach model. A rotary type clutch mechanism is designed and manufactured with electromagnetic circuit and its transmission torque level is experimentally evaluated according to the applied current. The manufactured MR clutch is integrated with accelerator pedal on which driver’s foot is placed to transmit haptic cue signal. In the meantime, a cue algorithm for gear shifting is formulated by considering vehicle model. The cue algorithm is then integrated with a haptic controller which is a torque model based-compensation strategy regarding Presiach hystersis linearization of the employed MR fluid. In this work, the haptic cue controller is implemented in discrete manner. Control performances are experimentally evaluated such as haptic tracking responses.

Power source is critical to achieve independent and autonomous operations of electronic mobile devices. The vibration-based energy harvesting is extensively studied recently, and recognized as a promising technology to realize inexhaustible power supply for small-scale electronics. Among various approaches, the piezoelectric energy harvesting has gained the most attention due to its high conversion efficiency and simple configurations. However, most of piezoelectric energy harvesters (PEHs) to date are based on bending-beam structures and can only generate limited power with a narrow working bandwidth. The insufficient electric output has greatly impeded their practical applications. In this paper, we present an innovative lead zirconate titanate (PZT) energy harvester, named high-efficiency compressive-mode piezoelectric energy harvester (HC-PEH), to enhance the performance of energy harvesters. A theoretical model was developed analytically, and solved numerically to study the nonlinear characteristics of the HC-PEH. The results estimated by the developed model agree well with the experimental data from the fabricated prototype. The HC-PEH shows strong nonlinear responses, favorable working bandwidth and superior power output. Under a weak excitation of 0.3 g (g = 9.8 m/s²), a maximum power output 30 mW is generated at 22 Hz, which is about ten times better than current energy harvesters. The HC-PEH demonstrates the capability of generating enough power for most of wireless sensors.

Unwanted accretions on structures are a common machinery maintenance problem, which can pose a serious safety threat if not treated effectively and punctually. In this paper we investigate the capability of piezo-excited structural waves for invoking delamination of accreted material from waveguides. We apply a wave-based technique for modelling piezoelectric excitation based on semi-analytical finite elements to model the interface shear stress associated with piezo-actuated structural waves. As a proof of concept, we present a demonstration experiment in which patches of material are removed from a beam-like waveguide with emulated anechoic terminations using ultrasonic excitation.

Production of high tip deflection in a piezoelectric bimorph laminar actuator by applying high voltage is limited by many physical constraints. Therefore, piezoelectric bimorph actuator with a rigid extension of non-piezoelectric material at its tip is used to increase the tip deflection of such an actuator. Research on this type of piezoelectric bending actuator is either limited to first order constitutive relations, which do not include non-linear behavior of piezoelectric element at high electric field, or limited to curve fitting techniques. Therefore, this paper considers high electric field, and analytically models tapered piezoelectric bimorph actuator with a rigid extension of non-piezoelectric material at its tip. The stillness, capacitance, effective tip deflection, block force, output strain energy, output energy density, input electrical energy and energy efficiency of the actuator are calculated analytically. The paper also discusses the multi-objective optimization of this type of actuator subjected to the mechanical and electrical constraints.

A piezofan is a resonant device that uses a piezoceramic material to induce oscillations in a cantilever beam. In this study, lumped-mass modelling is used to analyze a piezoelectric fan. Uncertainties are associated with the piezoelectric structures due to several reasons such as variation during manufacturing process, temperature, presence of adhesive layer between the piezoelectric actuator/sensor and the shim stock etc. Presence of uncertainty in the piezoelectric materials can influence the dynamic behavior of the piezoelectric fan such as natural frequency, tip deflection etc. Moreover, these quantities will also affect the performance parameters of the piezoelectric fan. Uncertainty analysis is performed using classical Monte Carlo Simulation (MCS). It is found that the propagation of uncertainty causes significant deviations from the baseline deterministic predictions, which also affect the achievable performance of the piezofan. The numerical results in this paper provide useful bounds on several performance parameters of the cooling fan and will enhance confidence in the design process.

In this work, nano-transducers with a superparamagnetic iron oxide (SPIO) core have been synthesized by preparation of precursor gold nanoseeds loaded on SPIO-embedded silica to form a gold nanoshell. The goal is for such nanotansducers to be used in theranostics to detect brain tumors by using MRI imaging and then assist in their treatment by using photothermal ablation. The iron oxide core provides for the use of a magnetic-field to guide the particles to the target (tumor) site. The gold nanoshell can be then readily heated using incident light and/or an alternating magneticfield. After synthesis of nano-transducer samples, Transmission Electron Microscopy was employed to analyze the formation of each layer. Then UV spectroscopy experiments were conducted to examine the light absorbance of the synthesized samples. The UV-visible absorption spectra shows a clear surface plasmon resonance (SPR) band around 530 nm, verifying the presence of gold coating nanoshells. Finally photothermal experiments using a high-power laser beam with a wavelength of 527 nm were performed to heat the samples. It was found that the temperature reaches 45° C in 12 minutes.

Traditional aeroelastic models rely only on good mechanical design and accurate crafting in order to match the required structural properties. This paper proposes an active regulation of their structural parameters in order to improve accuracy and reliability of wind tunnel tests. Following the design process steps typical of a smart structure, a damping tuning technique allowing to control a specific set of vibration modes is developed and applied on the aeroelastic model of a long-span suspended bridge. Depending on the testing conditions, the structural damping value can be adjusted in a fast, precise and repeatable way in order to highlight the effects of the aerodynamic phenomena of interest. In particular, vortex-induced vibration are taken into consideration, and the response of a bridge section to vortex shedding is assessed. The active parameter regulation allows to widen the pattern of operating conditions in which the model can be tested. The paper discusses the choice of both sensors and actuators to be embedded in the structure and their positioning, as the control algorithm to obtain the desired damping. Experimental results are shown and results are discussed to evaluate the performance of the smart structure in wind dunnel tests.

Electromagnetic dampers (EMD) have been widely studied and designed in the control of vibrating structures. Yet, their use for space applications has been almost negligible, due mainly to their high ratio of system mass over damping force produced. The development of shunted circuits, and in particular negative impedances, has allowed higher currents to flow in the device, thus obtaining an increased damping performance. However, the need for a thermal analysis has become crucial in order to evaluate the power and temperature limits of EMDs, and hence allow a more efficient optimization of the whole device. This paper presents a multiphysics Finite Element Analysis (FEA) of an EMD in which the thermal domain is integrated with the electromagnetic and mechanical domains. The influence of the temperature on the device parameters and overall performance in the operative temperature and frequency range of a space mission is shown. It follows a design optimization of an electromagnetic shunted damper for 5-kg SDOF to obtain a second-order filter. In particular, the analytical results are compared with the typical transfer function of a viscoelastic material. This paper demonstrates the feasibility to achieve the same slope of -40 dB/dec while considerably decreasing the magnitude of the characteristic resonance peak of viscoelastic materials.

Vibration of piezolaminated beams with extension and shear mode piezo actuators subjected to electromechanical loading is studied. A finite element eight node isoparametric element is adopted in the formulation with higher order shear deformation theory. Constitutive law for piezoelectric is considered. In case of the extension actuation mechanism, top and bottom layers of beam are of PZT-5A piezoelectric material and the central core is of Aluminum. Whereas, in case of shear actuation mechanism, top and bottom layers are of Aluminum and the central core is provided with a small patch of PZT-5A piezoelectric material and the rest of the core is a rigid foam material. Frequencies obtained by using present methodology are presented for both extension as well as shear actuation mechanism of piezoelectric material

Research presented in this paper focuses on the experimental and theoretical analysis of a compact, nonlinear, broadband energy harvesting device. Cantilevered structure zigzag beams have been shown to have natural frequencies orders of magnitudes lower than traditional cantilever beam geometries of the same size. Literature has also demonstrated that a cantilever beam harvester design combined with a magnetic field introduces nonlinearities in the response which can increase bandwidth of the device. Current energy harvester designs are relatively large in size, are most efficient at high frequencies, or only useful for narrowband linear operation. The proposed research introduces a zigzag geometry beam used in conjunction with a magnetic field to create a compact device capable of low frequency broadband energy harvesting. Experimental results are shown comparing both the linear and nonlinear energy harvesting capabilities of the zigzag structures. Experimental results are the focus of this paper, however, analytical expressions for the fundamental mode shape, natural frequency, and electromechanical coupling are presented for the linear lumped parameter system. A physics based magnetic force model for the nonlinear system is also proposed.

In this paper, a self-powered wireless sensor node utilising ambient vibrations for power is described. The device consists of a vibration energy harvester, power management system, microcontroller, accelerometer, RF transmitter/receiver and external LED indicators. The vibration energy harvester is adapted from a previously reported hybrid rotary-translational device and uses a pair of copper coil transducers to convert the mechanical energy of a magnetic sphere into usable electricity. The device requires less than 0.8 mW of power to operate continuously in its present setup (with LED indicators off) while measuring acceleration at a sample rate of 200 Hz, with the power source providing 39.7 mW of power from 500 mg excitations at 5.5 Hz. When usable input energy is removed, the device will continue to transmit data for more than 5 minutes.

The dynamic characteristics of mid-story isolated buildings and seismic response reduction due to a semi-active control system were investigated using a three-lumped-mass model that simplified the sixteen story building with an isolation layer in the sixth story. A semi-active control method using a rotary inertia mass damper filled with magnetorheological fluid (MR fluid) was proposed. The damper shows both mass amplification effect due to rotational inertia and variable damping effect due to the MR fluid. The damping force is controlled by the strength of the magnetic field that is applied to the MR fluid. It is determined by using the electric current, which is calculated by the proposed semi-active control method based on the velocity of the isolation layer relative to the layer just underneath it. Real-time hybrid tests using an actual damper and simulations using a building model were conducted to check the damper model; the test results were in good agreement with the simulation results. The simulation results suggest that the response displacement of the structure above the isolation layer is significantly reduced, without increasing the response acceleration of the entire structure against near-fault pulse and long-period ground motions. The proposed semi-active control using an MR rotary inertia mass damper was confirmed to be effective for mid-story isolated buildings.

Structural walls are important components of resisting the lateral loads for high-rise structures. However, the traditional walls are difficult to repair or replace in post-earthquake events. Hence, over the past few years, a research was made of several kinds of replaceable structures such as replaceable coupling beam and replaceable wall toe. In this paper, a new seismic energy dissipation wall structure is proposed. The new wall is one with purposely build-in vertical slits within the wall panel, and metallic dampers are installed on the vertical slits so that the seismic performance of the structure can be controlled. Moreover, the metallic damper is easy to be replaced in post-earthquake events. The proposed metallic damper is with a serial of diamond-shaped holes and designed based on the lateral deformation of the wall. The yielding scheme of the metallic damper is proposed in order to achieve the ductility and energy dissipation demand of the walls. The mechanical model of the metallic damper is established. Finally, the numerical simulations of the metallic damper based on the finite element software ABAQUS are presented to validate the effectiveness of the proposed mathematic model.

Piezoelectric-based vibration energy harvesting is of interest in a wide range of applications, and a number of harvesting schemes have been proposed and studied { primarily when operating under steady state conditions. However, energy harvesting behavior is rarely studied in systems with transient excitations. This paper will work to develop an understanding of this behavior within the context of a particular vibration reduction technique, resonance frequency detuning. Resonance frequency detuning provides a method of reducing mechanical response at structural resonances as the excitation frequency sweeps through a given range. This technique relies on switching the stiffness state of a structure at optimal times to detune its resonance frequency from that of the excitation. This paper examines how this optimal switch may be triggered in terms of the energy harvested, developing a normalized optimal switch energy that is independent of the open- and short-circuit resistances. Here the open- and short-circuit shunt resistances refer to imposed conditions that approximate the open- and short-circuit conditions, via high and low resistance shunts. These conditions are practically necessary to harvest the small amounts of power needed to switch stiffness states, as open-circuit and closed-circuit refer to infinite resistance and zero resistance, respectively, and therefore no energy passes through the harvesting circuit. The limiting stiffness states are then defined by these open- and short-circuit resistances. The optimal switch energy is studied over a range of sweep rates, damping ratios, and coupling coefficients; it is found to increase with the coupling coefficient and decrease as the sweep rate and damping ratio increase, behavior which is intuitive. Higher coupling means more energy is converted by the piezoelectric material, and therefore more energy is harvested in a given time; an increased sweep rate means resonance is reached sooner, and there will less time to harvest before the switch occurs; finally, increased damping nominally reduces the response of the system, therefore less mechanical energy is present and less energy will be harvested.

This paper presents the design and fabrication of a 2-degree of freedom vibration energy harvesting device for converting kinetic energy into electrical energy using electromagnetic transduction. The relative motion between a magnet and a conductive coil induces an electromotive force. A non-uniform magnetic field design is used where an oscillating magnet is suspended by a spring-damper system. In addition the coil is suspended to serve as the second oscillating mass to effectively harvest energy at two different frequencies. The design parameters are elucidated in this paper which describes the effects of voltage cancellation due to coil phase, coil placement for optimal performance and the benefits of separating magnets using material with high permeability. The investigation was performed using multi physics finite element analysis (COMSOL) with sinusoidal vibration input. A prototype was developed to demonstrate that practical amount of power can be generated from the design. The resonant frequencies of the prototype harvester were tuned to match the dominant frequencies of the host structure (i.e. heavy haul railcars). Peak output powers of 212 mW and 218 mW were generated from sinusoidal vibration with 0.4 g peak acceleration (where g = 9.8 m/s²) at 6.5 Hz and 14.5 Hz respectively.

In order to realize a six-degree-of-freedom (six-DOF) piezoelectric energy harvester through integrating six single-degree-of-freedom (single-DOF) piezoelectric energy harvesters into a parallel mechanism, which has six sensitive axes and broader bandwidth, a single-DOF piezoelectric energy harvester utilizing a clamped beam configuration is proposed in this paper. It consists of a proof mass and a corrugated clamped beam covered by piezoelectric patches, where the proof mass is mounted at the center of the beam. Compared to the conventional energy harvester, the proposed single-DOF vibration energy harvester has two parallelism mounting planes at the support of the beam and the mass, separately, and can be easily integrated into the parallel mechanism. The stiffness equation of the single-DOF piezoelectric energy harvester is established and analyzed. On this basis, the natural frequency and stress distribution of the harvester are investigated through analytical developments and numerical simulations. These results show that the proposed single-DOF vibration energy harvester has output with the excitation along its axis, while no outputs with the excitation perpendicular to the axis, and the natural frequency and stress distribution can be accurate estimated by the established theoretical models.

The existing vibration energy harvesters can only harvest the vibration energy with single sensitive axial and narrow band, which lead to the problems of low efficiency and high level requirements for installation. This paper proposes a piezoelectric energy harvester for six-degree-of-freedom (six-DOF) vibration energy harvesting utilizing a six-DOF parallel mechanism with cubic configuration. It consists of a proof mass as the upper platform, six flexible legs with two spherical joints connected by a single-degree-of-freedom (single-DOF) harvester, and a foundation support. Compared to the conventional energy harvester, the proposed six-DOF vibration energy harvester has six sensitive axes and broader bandwidth for the proper designed six adjacent natural frequencies, so higher efficiency of energy harvesting can be expected. To investigate the characteristics of the proposed energy harvester, analytical developments and numerical simulations on its natural frequency and modes of vibration are carried out. These results show that the proposed six- DOF vibration energy harvester can harvest six-DOF vibration energy.

Thermal control is an important aspect of every spacecraft. The thermal control system (TCS) must maintain the temperature of all other systems within acceptable limits in spite of changes in environmental conditions or heat loads. Most thermal control systems used in crewed vehicles use a two-fluid-loop architecture in order to achieve the flexibility demanded by the mission. The two-loop architecture provides sufficient performance, but it does so at the cost of additional mass. A recently-proposed radiator concept known as a morphing radiator employs shape memory alloys in order to achieve the performance necessary to use a single-loop TCS architecture. However, modeling the behavior of morphing radiators is challenging due to the presence of a unique and complex thermomechanical coupling. In this work, a partitioned analysis procedure is implemented with existing finite element solvers in order to explore the behavior of a possible shape memory alloy-based morphing radiator in a mission-like thermal environment. The results help confirm the theory of operation and demonstrate the ability of this method to support the design and development of future morphing radiators.

A passive control methodology to increase the seismic safety of multi-drum columns is presented. The response of a large scale column-model to dynamic excitations is investigated experimentally. A particle damper is used to replace one of the columns’ original drums. The influence of the system parameters on the response of the column is also examined. The seismic response of the column can be considerably reduced if a particle damper replaces a drum above the mid-height. Guidelines and a design methodology are proposed to restore and protect monumental structures consisting of multi-drum columns.

Viscoelastic dampers are one of popular vibration mitigation devices applied to tall buildings to reduce seismic and wind-induced vibiration. In this paper，a new kind of viscoelastic-wall damper, which could be installed at the shearwall location of high-rising buildings, is proposed to enhance the energy disspation ability. The seismic resistance behaviors of one tall building installed with the viscoelastic-wall dampers are investigated by numerical analysis. The mechanical property testing of the viscoelastic-wall damper is carried to investigate its performance parameter under various exciting frequency and strain amplitude. According to the testing results, a mathematical model of viscoelastic - wall damper is modeled based on Kelvin model. On the basis of a 36-floor frame-shear wall structure and using the finite element software ABAQUS, two finite element models of the high-rising building with and without viscoelastic-wall dampers are set up. Elasto-plastic time-history analysis is used to compare the seismic performance of the two structures subjected to the frequently and rarely earthquakes. It is proved that the seismic response of the structure is mitigated effectively when it is equipped with viscoelastic-wall dampers.

Recently, the concept of developing an active steerable needle has gathered a lot of attention as they could potentially result in an improved outcome in various medical percutaneous procedures. Compared to the conventional straight bevel tip needles, active needles can be bent by means of the attached actuation component in order to reach the target locations more accurately. In this study, the movement of the passive needle inside the tissue was investigated using numerical and experimental approaches. A finite element simulation of needle insertion was developed using LSDYNA software to study the maneuverability of the passive needle. The Arbitrary-Eulerian-Lagrangian (ALE) formulation was used to model the interactions between the solid elements of the needle and the fluid elements of the tissue. Also the passive needle insertion tests were performed inside a tissue mimicking phantom. This model was validated for the 150mm of insertion which is similar to the depth in our needle insertion experiments. The model is intended to be based as a framework for modeling the active needle insertion in future.

A relatively unexplored but extremely attractive field for the application of the shape memory technology is the area of rotary actuators, especially for generating continuous rotations. This paper deals with a novel design of a rotary motor based on SMA wires and overrunning clutches which features high output torque and boundless angular stroke in a compact package. The concept uses a long SMA wire wound round a low-friction cylindrical drum upon which the wire can contract and extend with minimum effort and limited space demand. Fitted to the output shaft by means of an overrunning clutch the output shaft rotates unidirectionally despite the sequence of contractions-elongation cycles of the wire. Following a design procedure developed in a former paper, a six-stage miniature prototype is built and tested showing excellent performance in terms of torque, speed and power density. Characteristic performances of the motor are as follows: size envelope = 48×22×30 mm³; maximum torque = 20 Nmm; specific torque = 6.31×10⁻⁴ Nmm/mm3; rotation per module = 15 deg; continuous speed (unloaded) = 4 rpm.

We propose two frameworks for the derivation of constitutive models for solids undergoing phase transformations. The first is based on the assumption that solid phases within the material are finely mixed whereas the second considers the material as a heterogeneous solution of phase fragments and uses the homogenization theory to derive equilibrium conditions for displacement fields and phase distributions. It is shown that in the case of reversible phase transformation, the energy of the material can be obtained by taking the convex envelope of the energy functions of the constituent phases. As an application, a schematic model is derived for an idealized shape memory alloy and used to obtain a novel analytical solution for the problem of semi-infinite mode III crack in this material. The derivation of the analytical solution uses the hodograph method to map Cartesian coordinates into the hodograph plane. The resulting boundary-value problem for the mode III crack considered becomes analytically tractable for the idealized shape memory alloy considered and leads to closed-form expressions for the displacement and phase volume fraction fields near the crack tip as well as for the boundaries between different phase regions.

Base isolation technology has been widely theoretically and experimentally investigated, and it has also been verified through many severe earthquakes. Three dimensional (3-D) isolation technology was proposed several years ago, and the 3-D isolation theory has well developed till now. However, the development of 3-D isolation technology was deeply affected by the 3-D isolator devices. Many presented 3-D isolators are generally made up of complicated components, such as rubber, springs, dampers or theirs combinations. These isolators have some problem in certain extent, such as difficult fabrication process or little energy dissipation ability along the vertical direction. This paper presents a novel 3- D isolator which is made up of martensitic shape memory alloy wires through weaving, rolling, and punching. Mechanical properties of 3-D shape memory alloy pseudo-rubber isolator (SMAPRI) are investigated including compression, shear, and compression-shear loading with different frequencies and amplitudes. The mechanical behavior of isolators with different parameters is also compared. Accordingly, the mechanism resulting in the above differences is also analyzed. Experimental results indicated that 3-D SMAPRI has good mechanical properties and energy dissipation ability along both of horizontal and vertical direction. The fabrication process of the proposed 3-D isolator is relatively easy and the mechanism of isolation is clearer than the traditional 3-D isolators. Therefore, this new kind of 3-D isolator has good potentiality in both of seismic isolation for civil infrastructures and industrial isolation for important or precision equipment.

Shape memory alloys (SMA) are a unique class of materials which have ability to undergo large deformation and also regain its undeformed shape by removal of stress or by heating. This unique property could be effectively utilized to enhance the safety of a structure. This paper presents the pushover analysis performance of a Reinforced Concrete moment resistance frame with the traditional steel reinforcement replaced partially with Nickel-Titanium (Nitinol) SMA. The results are compared with the RC structure reinforced with conventional steel. Partial replacement of traditional steel reinforcement by SMA shows better performance.

Active vibration controls are helpful in improving fatigue life of structures through limitation of absolute displacements. However, control algorithms are usually designed without explicitly taking into account the fatigue phenomenon. In this paper, an adaptive vibration controller is proposed to increase the fatigue life of a smart structure made of composite material and actuated with piezoelectric patches. The main innovation with respect to the most common solutions is that the control laws are directly linked to a damage driving force, which is correlated to a fatigue damage model for the specific material. The control logic is different depending on the damage state of the structure. If no significant damage affects the structure, the controller decreases the crack nucleation probability by limiting the driving forces in the overall structure. On the contrary, if initiated cracks are present, their further propagation is prevented by controlling the damage driving forces in the already damaged areas. The structural diagnostics is performed through a vibration-based health monitoring technique, while periodical adaptation of the controller is adopted to consider damage-induced changes on the structure state-space model and to give emphasis to the most excited modes. The control algorithm has been numerically validated on the finite element model of a cantilever plate.

Non-linear behavior is present in many mechanical system operating conditions. In these cases, a common engineering practice is to linearize the equation of motion around a particular operating point, and to design a linear controller. The main disadvantage is that the stability properties and validity of the controller are local. In order to improve the controller performance, non-linear control techniques represent a very attractive solution for many smart structures. The aim of this paper is to compare non-linear model-based and non-model-based control techniques. In particular the model-based sliding-mode-control (SMC) technique is considered because of its easy implementation and the strong robustness of the controller even under heavy model uncertainties. Among the non-model-based control techniques, the fuzzy control (FC), allowing designing the controller according to if-then rules, has been considered. It defines the controller without a system reference model, offering many advantages such as an intrinsic robustness. These techniques have been tested on the pendulum nonlinear system.

One of the important parameters in the design of transmission lines is the evaluation of the susceptibility of these cables to vibrations and if necessary, providing proper means to mitigate these vibrations. Transmission lines are especially susceptible to vibrations as a result of their light weight. Viscous dampers are one of the tools that can be applied to mitigate cable vibrations. However, the damping ratio obtained by these dampers is very limited. The present study provides a finite element formulation for an isoparametric cable element. A comparison is made between the results of presented approach with finite series method to validate the model. Additionally, a comparison is made between linear and non-linear behavior of a cable under sweep sinusoidal excitations with different amplitudes. Finally, a case study is conducted to investigate the potential of additional damping provided by a third viscous damper for the case in which two rubber bushings are already attached to the cable near the anchorages. Based on this case study, the dependency between the third damper location and optimum viscosity for maximum vibration mitigation that can be given to a cable with rubber bushings is investigated. The results of the present study show that although rubber bushings may help mitigating vibrations, they reduce the effect of additional damping devices. Additionally, for non-sagged cables, the nonlinearity is negligible in moderate vibrations. Lastly, if the third damper viscosity is selected properly, it can be very effective in further mitigating the vibrations amplitudes.

Motors are nearly the sole constituents for actuation and driving applications, but there exist cases where their use proves to be impractical. Shape memory alloy (SMA), then revolutionized the actuator technology, thereby opening the door for new ideas and designs and with it what seemed unfeasible in the past have now become challenging. Many conventional actuators and sensors could be substituted with SMA, obtaining advantages in terms of reduction of weight, dimensions and its cost. SMAs are a group of metallic materials that revert to a predefined shape via phase transformation induced by a thermal procedure. Unlike metals that exhibit thermal expansion, SMA exhibits contraction when heated, which is larger by a hundredfold and exerts tremendous force for its small size. The focus of this work is to realize SMA wire as actuator which finds suitable applications (space, aerospace, biomechanics, etc.) where minimizing space, weight and cost are prime objectives. The accomplishments reported in this paper represent a significant development in the design of SMA actuator configurations for linear actuation. Report on design, fabrication and characterisation of the proposed system is presented. The design took advantage of converting the small linear displacement of the SMA wire into a large linear elastic motion under the influence of biasing element. From the results with control it is aspired that with further improvements on the design, the actuator can be utilized in enabling practical SMA technologies for potential robotic and commercial applications.

This paper presents a hyper-redundant continuous robot used to perform work in places which humans can not reach. This type of robot is generally a bio-inspired solution, it is composed by a lot of flexible segments driven by multiple actuators and its dynamics is described by a lot degrees of freedom. In this paper a model composed of some rigid links connected to each other by revolution joint is presented. In each link a torsional spring is added in order to simulate the resistant torque between the links and the interactions among the cables and the robot during the relative rotation. Moreover a type of EAP actuator, called spring roll, is used as the end-effector of the robot. Through a suitable sensor, such as a camera, the spring roll allows to track a target and it closes the control loop on the robot to follow it.

Magnetostrictive actuators can be profitably used to reduce vibration in structures. However, this technology has been exploited only to develop inertial actuators, while patches actuators have not been ever used in practice. Patches actuators consist on a layer of magnetostrictive material, which has to be stuck to the surface of the vibrating structure, and on a coil surrounding the layer itself. However, the presence of the winding severely limits the use of such devices. As a matter of fact, the scientific literature reports only theoretical uses of such actuators, but, in practice it does not seem they were ever used. This paper presents an innovative solution to improve the structure of the actuator patches, allowing their use in several practical applications. The principle of operation of these devices is rather simple. The actuator patch is able to generate a local deformation of the surface of the vibrating structure so as to introduce an equivalent damping that dissipates the kinetic energy associated to the vibration. This deformation is related to the behavior of the magnetostrictive material immersed in a variable magnetic field generated by the a variable current flowing in the winding. Contrary to what suggested in the theoretical literature, the designed device has the advantage of generating the variable magnetic field no longer in close proximity of the material, but in a different area, thus allowing a better coupling. The magnetic field is then conveyed through a suitable ferromagnetic structure to the magnetostrictive material. The device has been designed and simulated through FEA. Results confirm that the new configuration can easily overcome all the limits of traditional devices.

In this paper we present preliminary experimental results relative to the control of a multi-stage seismic attenuators and inertial platforms in the band 0:01±10Hz, using a open loop monolithic folded pendulum as inertial sensors. In fact, beyond the obvious compactness and robustness of monolithic implementations of folded pendulum, the main advantages of this class of sensors are the tune-ability of the resonance frequency, the high sensitivity, due to integrated laser optical readout, in a large measurement band. The results are presented and discussed in this paper together with the planned further developments and improvements.

This article considers a theoretical and experimental comparative analysis in the responses of a three-story building-like structure using two different schemes of passive vibration control. These control schemes are designed to reduce the effects of resonant vibrations generated by an electromechanical shaker located in the base of the building-like structure. The first control scheme consists on the design of a Tuned-Mass-Damper located over the third floor of the structure, and the second control scheme considers the implementation of an autoparametric cantilever beam absorber. The mathematical model of the overall system is obtained using Euler-Lagrange method. In order to validate the frequency response of the main system a finite element model is completed. Some numerical and experimental results are included to show the dynamic behavior and stability performance of the overall mechanical system.

In this paper, a new innovative modified high-loaded magneto-rheological fluid (MR in short) damper-mount is presented. The proposed damper-mount is designed based on two modes of MR fluid such as flow mode and shear mode, and it includes two separated electric coil for establishing magnetic field. The damping force of the damper-mount is analyzed based on the difference pressure between upper chamber and lower chamber. After analyzing the mathematical function of damping force, the proposed mount is optimized following the maximal damping force by using ANSYS software. Besides, there is a laboratorial MR fluid using in this optimization such as plate-like fluid MRF140. Results of optimization show that the requirement of damping force is obtain and the saturation of materials is in range of limitation.

In this paper, for modeling the MR dampers, based on the phenomenological model, a normalized phenomenological model is derived through incorporating a “normalization” concept and a restructured model is proposed and realized also with incorporation of the “normalization” concept. In order to demonstrate, a multi-islands genetic algorithm (GA) is employed to identify the parameters of the restructured model, the normalized phenomenological model as well as the phenomenological model. The research results indicate that, as compared with the phenomenological model and the normalized phenomenological model, (1) the restructured model not only can effectively decrease the number of the model parameters and reduce the complexity of the model, but also can describe the nonlinear hysteretic behavior of MR dampers more accurately, and (2) the normalized phenomenological model can improve the model efficiency as compared with the phenomenological model, although not as good as the restructured model.

In this work, a new type of MR brake featuring tapered inner magnetic core is proposed and its braking performance is numerically evaluated. In order to achieve high braking torque with restricted size and weight of MR brake system, tapered inner magnetic core is designed and expands the area that the magnetic flux is passing by MR fluid-filled gap. The mathematical braking torque model of the proposed MR brake is derived based on the field-dependent Bingham rheological model of MR fluid. Finite element analysis is carried out to identify electromagnetic characteristics of the conventional and the proposed MR brake configuration. To demonstrate the superiority of the proposed MR brake, the braking torque of the proposed MR brake is numerically evaluated and compared with that of conventional MR brake model.

This work deals with the robust asymptotic output tracking control problem of the tip position of a space frame flexible structure, mounted on a rigid revolute servomechanism actuated and controlled with a dc motor. The structure is also affected by undesirable vibrations due to excitation of its first lateral vibration modes and possible variations of the tip mass. The overall flexible structure is modeled by using finite element methods and this is validated via experimental modal analysis techniques. The tip position of the structure is estimated from acceleration and strain gauge measurements. The asymptotic output tracking problem is formulated and solved by means of Passivity-Based and Sliding-Mode Control techniques, applied to the dc motor coupled to the rigid part of the structure, and those undesirable vibrations are simultaneously attenuated by an active vibration control using Positive Position Feedback control schemes implemented on a PZT stack actuator properly located into the mechanical structure. The investigation also addresses the trajectory tracking problem of fast motions, with harmonic excitations close to the first vibration modes of the structure. The overall dynamic performance is evaluated and validated by numerical and experimental results.

Wireless sensor networks need energy harvesting from vibrational environment for their power supply. The conventional resonance type vibration energy harvesters, however, are not always effective for low frequency application. The purpose of this paper is to propose a high efficiency energy harvester for low frequency application by utilizing plucking and SSHI techniques, and to investigate the effects of applying those techniques in terms of the energy harvesting efficiency. First, we derived an approximate formulation of energy harvesting efficiency of the plucking device by theoretical analysis. Next, it was confirmed that the improved efficiency agreed with numerical and experimental results. Also, a parallel SSHI, a switching circuit technique to improve the performance of the harvester was introduced and examined by numerical simulations and experiments. Contrary to the simulated results in which the efficiency was improved from 13.1% to 22.6% by introducing the SSHI circuit, the efficiency obtained in the experiment was only 7.43%. This would due to the internal resistance of the inductors and photo MOS relays on the switching circuit and the simulation including this factor revealed large negative influence of it. This result suggested that the reduction of the switching resistance was significantly important to the implementation of SSHI.

In this paper, a new sensor-less parameter estimation method is proposed for electromagnetic shunt damping. The purpose is to estimate parameters of an electromagnetic transducer and a vibrating structure. The frequency domain measurements of an electrical admittance are only supposed to be available but any other sensor measurements are not; therefore, the estimation problem is nontrivial. Two types of numerical optimization, a linear optimization to select an initial seed and a nonlinear optimization to determine a final estimate, are presented. The effectiveness of the method is demonstrated by vibration control experiments as well as parameter estimation experiments.

This paper presents theoretical investigation on a coupling system consisting of bistable oscillator with an elastic magnifier (EM) to improve the output performances in vibration energy harvesting. Lumped-parameter nonlinear equations of the coupling system are derived to describe the broadband large-amplitude periodic displacement responses of the coupling system. The effects of the system mass ratio and stiffness ration on the output performances are studied. It shows that increasing the mass ratio and stiffness ratio can improve the system output performances. The distinct advantage in the coupling system lies in the existence of large-orbit periodic vibration over low level range. With the comparison of the electromechanical trajectories obtained from simulations, it shows that the coupling system can harvest more power at low excitation level with larger bandwidth as compared to the bistable oscillator without an EM.

The topic of this paper is the analysis of a control system for a semi active rear suspension in an off-road 2-wheel vehicle. Several control methods are studied, as well as the recently proposed Frequency Estimation Based (FEB) algorithm. The test motorcycle dynamics, as well as the passive, semi active, and the algorithm controlled shock absorber models are loaded into BikeSim, a professional two-wheeled vehicle simulation software, and tested in several road conditions. The results show a detailed comparison of the theoretical performance of the different control approaches in a novel environment for semi active dampers.

A magnetorheological (MR) damper can adapt its dynamic performance to the vibration environment by controlling the current applied. Compared to other types of dampers, the MR damper has a wider range of dynamic characteristics. Two different dampers: hydraulic, and MR dampers were tested under forced sinusoidal excitations of low to high frequencies. Also, different currents were applied on the MR damper to investigate its performance under varying electromagnetic fields. The results reveal that the two dampers have nonlinear dynamic characteristics and that characteristics of the hydraulic damper are different from those of the MR damper. The hydraulic damper provides slight nonlinear damping force whereas the MR damper shows a strong nonlinear property. In addition, the hydraulic damper is designed to provide an asymmetric damping force of rebound and compression whereas the MR damper provides a symmetric damping force. In the experiments conducted, the excitation frequency was varied from 3 Hz to 11 Hz and the amplitude from 2.5 mm to 12 mm. For the hydraulic damper, the lowest compression damping force only increases by about 0.54 kN while the rebound force increases by about 1.9 kN. In contrast, the variations of compression and rebound forces of the MR damper are 1.9 and 2.0 kN, respectively. Furthermore, the damping force of the MR damper increases as the current increases from 0 to 0.75 A.

A new lead-zirconium-titanate (PZT) actuator design for a micro scanning illuminating device is being developed. The thin PZT film is deposited directly on stainless steel by using an aerosol deposition machine. The aerosol deposition method enables inexpensive, quick, room temperature fabrication while producing high quality PZT films. The presented scanners would be attractive for endoscopic device applications, where inexpensive systems with high resolution would be a move toward disposal endoscopes. The design of this scanning illuminator and fabrication method are presented. Measurements of the PZT layer surface roughness and the aerosol deposited PZT powder particle diameter are presented. Ongoing work and fabrication challenges are discussed.