Search

In this work, the fabrication of Rochelle salt based piezoelectric structures is illustrated. Structures composed of paper and Rochelle salt are easily manufactured using simple processes. Both manufacturing and the material itself are environmental friendly. Additionally Rochelle salt is biocompatible. In the paradigm of a cleaner piezoelectric technology, the fabrication of active sensing or actuating devices is developed. Thus processing method, material and piezoelectric properties have been studied: (1) pure crystals are used as acoustic actuator, (2) properties of paper impregnated with Rochelle salt are detailed, (3) charge generation is demonstrated on the impregnated material. Actuating and sensing devices are reported in order to highlight the potential of this green piezoelectric material. [ABSTRACT FROM AUTHOR]

This paper comprehensively reviews effective control applications using shape memory alloy (SMA) actuators. Among many applications, this paper focuses on the vibration and stiffness control of flexible structures and shape control in the aerospace engineering field. In the vibration control of flexible structures, three different methods are introduced and discussed, including their merits and demerits. In addition, several control strategies, such as neuro-fuzzy controller, are investigated in terms of the implementation associated with the microchip. In the control process, the inherent hysteretic behavior of SMA is also reviewed as a feedforward loop or actuating force compensator. At the second part, applications on the morphing wing in the field of aerospace engineering are reviewed, and salient characteristics are discussed. In this review, the morphing wing, which is closely related to aircraft stability, is mainly investigated considering control logics and geometrical parameters. For easily understanding morphing control using SMA, a table which summarizes the main contribution of each research is presented. It is expected, since this review article provides numerous approaches for vibration and morphing control conducted over the last decade, it will be very helpful to the same research community to create novel ideas to achieve more advanced and effective results in vibration and morphing control using SMA actuators. [ABSTRACT FROM AUTHOR]

Linear first/second order fin direct current (DC) actuator model approximations for missile applications are currently limited to angular position and angular velocity state variables. Furthermore, existing literature with detailed DC motor models is decoupled from the application of interest: tail controller missile lateral acceleration (LATAX) performance. This paper aims to integrate a generic DC fin actuator model with dual-mode feedforward and feedback control for tail-controlled missiles in conjunction with the autopilot system design. Moreover, the characteristics of the actuator torque information in relation to the aerodynamic fin loading for given missile trim velocities are also provided. The novelty of this paper is the integration of the missile LATAX autopilot states and actuator states including the motor torque, position and angular velocity. The advantage of such an approach is the parametric analysis and suitability of the fin actuator in relation to the missile lateral acceleration dynamic behaviour. [ABSTRACT FROM AUTHOR]

The initial internal temperature of a hard disk drive (HDD) differs according to the operating environment, and the various heat sources from the surrounding environment raise the internal temperature of the HDD after operation starts. Such temperature change ranges from 0 °C to 60 °C in the usual operating environment. This affects the characteristics of a pivot bearing that supports the HDD actuator. This paper predicts how the characteristics of pivot bearings change in relation to temperature and how the dynamic characteristics of actuators change according to the change of bearing characteristics. These changes are also verified through experiments. [ABSTRACT FROM AUTHOR]

This paper considers the electrical actuation of aircraft wing surfaces, with particular emphasis on flap systems. It discusses existing hydraulic and electrohydraulic systems and proposes an electrical alternative, examining the potential system benefits in terms of increased functionality, maintenance, and life-cycle costs. This paper then progresses to describe a full-scale actuation demonstrator of the flap system, including the high-speed electrical drive, step-down gearbox, and flaps. Detailed descriptions of the fault-tolerant motor, power electronics, control architecture, and position sensor systems are given, along with a range of test results, demonstrating the system in operation. [ABSTRACT FROM AUTHOR]

In this paper, we propose a model for ionic polymer metal composite (IPMC) actuators that its superiority over the other models is its capability to make a confident prediction about the bending displacement of all points along the IPMC strip in large bending displacements, without using previous data of the output and also with consideration of the effects of the ambient conditions on its performance. To achieve this aim, we used a nonautoregressive model named as Laguerre-multilayer perceptron network. Moreover, the effect of ambient temperature and humidity changes in the range of biomedical applications of IPMC was investigated using variance analysis of experimental data and also these ambient conditions were applied to the proposed model as operating points. This model was described in detail and validated by experimental results. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Mechanical Engineering / Strojniški Vestnik is the property of University of Ljubljana, Faculty of Mechanical Engineering, Journal of Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents an electromechanical coupled dynamic equation for the lateral-flexural and torsional vibrations of a flexible ring for an electromechanical integrated electrostatic harmonic actuator as well as the equation of the forced response of the electromechanical integrated electrostatic harmonic actuator to voltage excitation. By solving these equations, the natural frequency and vibration modes of the flexible ring for the actuator are investigated. Changes in the natural frequency with respect to the main system parameters are also examined and the dynamic responses of the actuator to voltage excitation obtained. [ABSTRACT FROM AUTHOR]

This paper presents a detailed study of the dynamic performance of an electrostatic surface drive actuator. This actuator is capable of producing 50 g's of acceleration with 70 μm travel at a 30 V bias. For the first time, air operation of a dipole surface actuator is demonstrated and we describe a fabrication process that has increased device yield more than an order of magnitude. Detailed characterization of the actuator performance is enabled by the integration of a capacitive position sensor that provides 0.5 Å resolution in a 1-Hz bandwidth. The performance of this actuator is compared with other micromachined actuators and with more conventional milliactuators. [ABSTRACT FROM AUTHOR]

This paper describes a newly developed Levy form adaptive cable dome, which has the ability to alter its stiffness configuration and stress properties to adapt its behavior to current loading conditions. This novel structure contains sensors that detect forces in the system and an action member that adjusts its stiffness and stress state, making the structure more rigid or flexible, depending upon the actual load applied. This system consists of 42 tensioned cables, 6 compressed struts, and a central strut that is designed to function as an actuator. Results of the experimental and theoretical analyses are compared. Tests are aimed at verifying the cable dome's ability to adapt its state of stress to changing load cases to maintain the reliability of the system. Tests confirmed the functionality of the developed adaptive system and the applicability of the proposed equipment, software, computational models, and control commands. Results demonstrate that the behavior of the adaptive cable dome obtained by tests generally can be closely predicted numerically with nonlinear finite element analyses. [ABSTRACT FROM AUTHOR]

The paper addresses the forced flexural vibrations and dissipative heating of a circular viscoelastic plate with piezoactive actuators under axisymmetric loading. A refined formulation of this coupled problem is considered. The viscoelastic behavior of materials is described using the concept of complex moduli dependent on the temperature of dissipative heating. The electromechanical behavior of the plate is modeled based on the Timoshenko hypotheses for the mechanical variables and analogous hypotheses for the electric-field variables in the piezoactive layers of the actuator. The temperature is assumed constant throughout the thickness. The nonlinear problem is solved by a time stepping method using, at each step, the discrete-orthogonalization and finite-difference methods to solve the elastic and heat-conduction equations, respectively. A numerical study is made of the effect of the shear strain, the temperature dependence of the material properties, fixation conditions, and geometrical parameters of the plate on the vibrational characteristics and the electric potential applied to the actuator electrodes to balance the mechanical load [ABSTRACT FROM AUTHOR]

To advance the state of the art of physical-principle-enhanced hybrid artificial neural network (ANN) modeling, network configurations with parallel modules (PMNN) reflecting the structural information of the physical principles have been developed (Cao, 2001). In this paper, the PMNN configuration is applied to develop a scalable and invertible dynamic magneto-rheological (MR) fluid damper model. To advance the state of the art and address issues of the current ANN-based MR damper models found in the open literature, two ANN-based MR damper models are developed in this study. The first one is a conventional first-principle-enhanced hybrid neural network model (defined as the baseline model in the current study) that improves upon the previous ANN-based MR damper models by introducing feedback loops to represent the dynamic behaviors of the MR damper. A PMNN-based MR damper model is then derived to further improve the control-input-output scalability and realize the invertible model concept. "Input-output scalability" refers to the model's capability to accurately estimate the system response with input profiles significantly different from the training data. "Invertible model" means that the resultant forward model can be directly transformed into an inverse model through a simple algebraic operation. The network training/testing results indicate that while both models provide satisfactory performance, the PMNN model outperforms the baseline model by showing superior control-input-output scalability. The candidacy of PMNN as a control-oriented actuator modeling tool is further strengthened by the fact that it is invertible, in other words, the inverse model with desired force as input and the control signal-voltage as output can be easily established by algebraically manipulating the forward model. This study indicates that PMNN, as a scalable and invertible dynamic modeling tool, is feasible for developing system-design-oriented models of vibration control purposes. [ABSTRACT FROM AUTHOR]

Abstract: This paper investigates the electro-mechanical behaviour of a thick, laminated actuator with piezoelectric and isotropic lamina under externally applied electric loading using a new two-dimensional computational model. The elastic core is relatively thick and thus it is modelled by Timoshenko thick-beam theory. Although the piezoelectric lamina is a beam-like layer, it is formulated via a two-dimensional model because of not only the strong electro-mechanical coupling, but also of the presence of a two-dimensional electric field. It is shown in this paper that a one-dimensional model for the piezoelectric beam-like layer is inadequate. The piezoelectric model is constructed within the scope of linear piezoelectricity. The actuation response is induced through the application of external electric voltage. Under the strong coupling of elasticity and electricity, the strain energy and work of electric potential are presented. The electro-mechanical response of the laminated Timoshenko beam is formulated and determined via a variational energy principle. Numerical examples presented illustrate convincing comparison with finite element solutions and existing published data. New numerical solutions are also presented to investigate the geometric effect on the electro-mechanical bending behaviour. [Copyright &y& Elsevier]

This paper reports on the development of a unique Digital Loudspeaker Array solution, based on Pb(Zr 0.52 ,Ti 0.48 )O 3 (PZT) thin-film actuated membranes, arranged in a matrix and which operate in a binary manner by emitting short pulses of sound pressure. Using the principle of additivity of pressures in the air, it is possible to reconstruct audible sounds. For the first time, electromechanical and acoustic characterizations were reported on 256 MEMS membranes DLA. Sounds audible as far as several meters from the loudspeaker have been generated using low-voltage. [ABSTRACT FROM AUTHOR]

In production processes, many adjustment tasks have to be carried out manually. In order to automate these activities, there is a need for cost and space efficient actuators that can provide comparatively high forces. This paper presents a novel actuator concept based on the phase change material paraffin wax. Furthermore, a numerical modelling strategy is introduced enabling the prediction of actuator properties. The model considers paraffin wax as a deformable body. The temperature-dependent volume expansion data of the paraffin wax is obtained experimentally to allow for a realistic description of the thermal-mechanical properties. The simulation is verified, using experimental data from actuators with varying paraffin wax volumes. With a maximum deviation of 6%, the simulations show a good agreement with the experiments. [ABSTRACT FROM AUTHOR]

Abstract: Many applications involve actuated devices made of shape memory alloys, but the lack of efficient numerical tools hinders the development of such technologies. Software using a finite element method like ANSYS allows the user to predict complex responses of a system without extensive programming. In this paper, a homemade phenomenological 1D bilinear model is programmed through the USERMAT procedure in ANSYS. The model allows the representation of both mechanical and thermal hystereses. The martensitic transformation is controlled by transformation criteria similar to those used in conventional plasticity, and subcycles are modeled by a simple elastic return through the hysteresis. The model is validated through isothermal tensile testing, assisted two-way shape memory testing and stress generation testing, and a good agreement with experimental results is shown. Finally, thermomechanical response of a single-degree-of-freedom actuator is simulated as a typical application and a case study involving the shape change of a radio controlled aircraft wing shows the potential of the numerical simulations. [Copyright &y& Elsevier]

We present an untethered, electrostatic, MEMS micro-robot, with dimensions of 60 µm by 250 µm by 10 µm. The device consists of a curved, cantilevered steering arm, mounted on an untethered scratch drive actuator (USDA). These two components are fabricated monolithically from the same sheet of conductive polysilicon, and receive a common power and control signal through a capacitive coupling with an underlying electrical grid. All locations on the grid receive the same power and control signal, so that the devices can be operated without knowledge of their position on the substrate. Individual control of the component actuators provides two distinct motion gaits (forward motion and turning), which together allow full coverage of a planar workspace. These MEMS micro-robots demonstrate turning error of less than 3.7°/mm during forward motion, turn with radii as small as 176 µm, and achieve speeds of over 200 µm/sec with an average step size as small as 12 nm. They have been shown to operate open-loop for distances exceeding 35 cm without failure, and can be controlled through teleoperation to navigate complex paths. The devices were fabricated through a multiuser surface micromachining process, and were postprocessed to add a patterned layer of tensile chromium, which curls the steering arms upward. After sacrificial release, the devices were transferred with a vacuum microprobe to the electrical grid for testing. This grid consists of a silicon substrate coated with 13-µm microfabricated electrodes, arranged in an interdigitated fashion with 2-µm spaces. The electrodes are insulated by a layer of electron-beam-evaporated zirconium dioxide, so that devices placed on top of the electrodes will experience an electrostatic force in response to an applied voltage. Control waveforms are broadcast to the device through the capacitive power coupling, and are decoded by the electromechanical response of the device body. Hysteresis in the system allows on-board storage of ii = 2 bits of state information in response to these electrical signals. The presence of on-board state information within the device itself allows each of the two device subsystems (USDA and steering arm) to be individually addressed and controlled. We describe this communication and control strategy and show necessary and sufficient conditions for voltage-selective actuation of all 2n system states, both for our devices (n = 2), and for the more general case (where n is larger.) [ABSTRACT FROM AUTHOR]

This paper discusses research carried-out by ALSTOM POWER on the development and validation (on laboratory scale plant) of an observer-based fault detection identification and accommodation (FDIA) system for an electromechanical actuator. Three separate linear observers (or Kalman filters) are used to detect and identify faults corresponding to the system''s three sensors. Having successfully detected a sensor fault, a reconstructed measure of that output signal (generated from an observer not associated with that sensor) is used to replace the measured signal for feedback control. This ensures that the system can continue to function effectively even after a sensor failure. The experimental results demonstrate that this approach could significantly enhance the post-fault availability of such systems. [Copyright &y& Elsevier]

In this work, epoxy-based shape-memory actuators have been developed by taking advantage of the sequential dual-curing of off-stoichiometric "thiol-epoxy" systems. Bent-shaped designs for flexural actuation were obtained thanks to the easy processing of these materials in the intermediate stage (after the first curing process), and successfully fixed through the second curing process. The samples were programmed into a flat temporary-shape and the recovery-process was analyzed in unconstrained, partially-constrained and fully-constrained conditions using a dynamic mechanical analyzer (DMA). Different "thiol-epoxy" systems and off-stoichiometric ratios were used to analyze the effect of the network structure on the actuation performance. The results evidenced the possibility to take advantage of the flexural recovery as a potential actuator, the operation of which can be modulated by changing the network structure and properties of the material. Under unconstrained-recovery conditions, faster and narrower recovery-processes (an average speed up to 80%/min) are attained by using materials with homogeneous network structure, while in partially- or fully-constrained conditions, a higher crosslinking density and the presence of crosslinks of higher functionality lead to a higher amount of energy released during the recovery-process, thus, increasing the work or the force released. Finally, an easy approach for the prediction of the work released by the shape-memory actuator has been proposed. [ABSTRACT FROM AUTHOR]

An attempt has been made in this study to develop a continuous rotary motor actuated by multiple segments of shape memory alloy wires (SMA motor). In order to meet the requirements of continuous rotation, large output torque, and stall torque, a unidirectional rotary actuator was designed, and five rotary actuators were fixed on one shaft in series. When every actuator is actuated in turn, the SMA motor can realize a continuous rotation. In order to simulate the rotation angle, output torque, and the actuation performance degradation of the SMA motor, Lagoudas's constitutive model was modified to consider the cyclic actuation influence. After design and simulation, a prototype of the SMA motor was fabricated and experimentally tested to verify the feasibility and performance of the proposed design decision. The test results indicate that the SMA motor can realize continuous rotation. The rotation speed is 0.28 r/min, and the torque is 1008 N mm. [ABSTRACT FROM AUTHOR]

The forced monoharmonic vibrations and self-heating of a circular thermoviscoelastic plate with piezoelectric sensor and actuator are studied. The viscoelastic behavior of the passive (without piezoeffect) and piezoactive materials is described using the concept of complex moduli. The problems of electroelasticity and heat conduction are solved numerically, assuming that the mechanical load is unknown. The effect of self-heating on the active damping of the vibrations of the plate is analyzed [ABSTRACT FROM AUTHOR]

An advantage of shape memory alloys (SMAs) is their potential to generate integrated actuator systems with a shape memory component. This can be accomplished for example by activating the thermal shape memory effect in selected regions of the SMA-component. We refer to this process as partial activation. The purpose of the present study is to find a way to create universal actuators with properties adjustable for various applications solely by partial activation. Thus, an object of investigation is the analysis of properties and capabilities of partial activation. Furthermore this study also implicates the survey of possibilities for partial power supply and electrical contacting. One possibility to use partial activation in integrated systems is given by the agonist-antagonist design. This type of design offers the advantage that a return spring or a mechanical brake for clamping the position without feeding electrical power is not necessary. On the other hand retention force is limited by the martensitic plateau and positioning accuracy by the elastic portion of mechanical stress. To solve these problems with constructive or control-oriented solutions is furthermore an aim of this study. Another approach is to use partial activation for influencing passive superelastic structures like hinges, dampers, or return elements by changing the austenitic plateau stress in integrated systems. To create a multifunctional integrated system, the NiTi-elements presented in this study offer various options since they apply partial activation both for thermal shape memory and for influencing super elasticity. [ABSTRACT FROM AUTHOR]

Position error signal (PES) design margin of a current hard disk drive is getting smaller as the track density of high-capacity disk drives increases. In the present work, a new actuator design concept is introduced for suppressing one of the actuator vibration modes, the so-called butterfly mode, that normally limits the expansion of servo bandwidth. The new actuator has a single coil with four sections having respective particular directions. By adjusting the length and inclined angle of the sections of the voice coil motor (VCM) coil, the forces perpendicular to track-seeking direction can be balanced with each other. Consequently, the butterfly mode is not excited by the resultant force of the VCM. Contribution of the proposed actuator design for the PES management is verified by numerical simulations. Our results show that the servo bandwidth can be increased from 1207 to 1680 Hi so that the PES can be decreased by 27% due to the use of the improved actuator. [ABSTRACT FROM AUTHOR]

Gossamer structures have been a subject of renewed interest for space applications because of their low weights, on-orbit deploying capabilities, and minimal stowage volumes. In this study, vibration suppression of an inflated structure using piezoelectric actuators and sensors has been attempted. These actuators and sensors can be suitably used for gossamer structures since they can conform to curved surfaces and provide distributed actuation and sensing capabilities. Using the natural frequencies and mode shapes of the system (structure, actuators, and sensors), a state-space model is derived. For designing a robust vibration controller, we used a sliding mode technique. The derivations of the sliding model controller and observer are presented in details. Finally, by means of numerical analysis, the method was demonstrated for an inflated torus considering Macro-Fiber Composite (MFC™) as actuators and Polyvinylidene Fluoride (PVDF) as sensors. The simulation studies show that the piezoelectric actuators and sensors are suitable for vibration suppression of an inflatable torus. The robustness properties of the controller and observer against the parameter uncertainty and disturbances are also studied. [ABSTRACT FROM AUTHOR]

Kinematic and dynamic control problems for a pedestal-mounted robot with a multilink arm are formulated. The robot is considered a system of perfectly rigid bodies controlled by a combined actuating system. The mathematical model of robot dynamics accounts for the elastic properties of actuator components based on the formalism of Lagrange equations of the second kind. The effect of the elastic compliance of the actuator components on the dynamics of manipulator links and actuator motors is discussed. A robot with a two-link arm is considered as an example [ABSTRACT FROM AUTHOR]

An optical head composed of an optical module and a biaxial actuator is designed for small form factor drives. This system adopts a finite-conjugate objective lens with numerical aperture 0.65 for 654-nm wavelength. A holographic optical element is used for simplifying the optical configuration which provides a better approach for alignment. The actuator is of a spider-like suspension for the focusing and is of a swing arm for the tracking. [ABSTRACT FROM AUTHOR]

A small optical disk drive for mobile electronics has been studied widely. We propose the two-dimensional actuator available to the 5-mm-thick small form factor optical disk drive. It has an asymmetric structure in both sides of the actuator. Its focusing actuation part and tracking actuation part were separated. The vibration characteristics of the asymmetric actuator model showed the potential of an extremely small actuator. [ABSTRACT FROM AUTHOR]