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This paper concerns laminates made of composite plies with piezoelectric actuators. The subject of the paper is the research of laminates having, in some directions, null expansion coefficients in extension or having the same expansion coefficient in each direction (isotropic behavior). The general equations for the problem are given in the theoretical framework of the so-called polar method for the representation of plane tensors. Some simple formulas are given for the case of expansion coefficients of a standard plate introduced in the paper. Some numerical examples close the paper. [ABSTRACT FROM AUTHOR]

Copyright of Science: Future of Lithuania / Mokslas: Lietuvos Ateitis is the property of Vilnius Gediminas Technical University 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.)

Pneumatic servo drives often demonstrate significant non-linearities and low natural frequency. This paper studies the feasibility in employing such drives to achieve simple motion profile following through adopting a high-gain control approach. A new design model is presented, which differs from previous research studies and provides the basis for formulating the control approach. A vane-type reciprocating actuator has been chosen for this study. The effects of various controller gain terms on dynamic responses and system stability are illustrated. A tuning procedure is thus identified on the basis of analytical and experimental observations. [ABSTRACT FROM AUTHOR]

Usually when piezoelectric membrane actuators are mentioned, one classically thinks of a passive membrane with a piezoelectric actuator on top. In this paper omitting the passive membrane will be suggested. Therefore, the piezoelectric actuator will not be commonly designed as plate capacitor structure, such as that the piezoelectric material sitting between two plate electrodes. Rather will the actuation be caused by structured surface electrodes on only one side of the piezoelectric material, leaving the opposite side free of potential. Several surface electrode designs, starting with interdigital parallel structures, known from surface acoustic wave transducers, spiral and ring structures, ending with star-shaped structures, are tested. The main advantage of this actuation principle is that with the varying electrode design it became possible to also generate an upward movement, i.e., in the direction of electrode side of the membrane. This upward movement has not been achieved with any piezoelectric membrane actuator so far. [ABSTRACT FROM AUTHOR]

In the nearly six decades since researchers began to explore methods of creating them, exoskeletons have progressed from the stuff of science fiction to nearly commercialized products. While there are still many challenges associated with exoskeleton development that have yet to be perfected, the advances in the field have been enormous. In this paper, were review the history and discuss the state-of-the-art of lower limb exoskeletons and active orthoses. We provide a design overview of hardware, actuation, sensory, and control systems for most of the devices that have been described in the literature, and end with a discussion of the major advances that have been made and hurdles yet to be overcome. [ABSTRACT FROM AUTHOR]

We demonstrate how to use feedback control of microflows to steer multiple particles independently in planar microfluidic systems driven by electro-osmotic actuation. This technique enables the handling of biological materials, such as cells, bacteria, DNA, and drug packets, in a hand-held format using simple and easy-to-fabricate actuators. The feedback loop consists of a vision system which identifies the positions of the particles in real-time, a control algorithm that computes the actuator (electrode) inputs based on information received from the vision system, and a set of electrodes (actuators) that create the required flow through electro-osmotic forces to steer all the particles along their desired trajectories and correct for particle position errors and thermal noise. Here, we focus on the development of control algorithms to achieve the steering of particles: vision system implementation, fabrication of devices, and experimental validation is addressed in other publications. In particular, steering of a single (yeast cell) particle has been demonstrated experimentally in our prior research and we have recently demonstrated experimental steering of three particles independently. In this paper, we develop the control algorithms for steering multiple particles independently and we validate our control techniques using simulations with realistic sources of initial position errors and thermal noise. In this study, we assume perfect measurement and actuation. [ABSTRACT FROM AUTHOR]

Several studies have been conducted in order to find the optimal location of actuators and sensors in the active vibration control of structures. In this paper, a modified optimization criterion is proposed for these two optimization problems, ensuring good observability or good controllability of the structure, and considering residual modes to limit the spill-over effects. Its efficiency is shown by the comparison with the classical criteria, illustrated for a simply supported beam and a rectangular plate. In these two applications, the number of active elements is discussed, using or neglecting the residual modes. [ABSTRACT FROM AUTHOR]

Engine adaptation for alternative fueling may generate certain difficulties in terms of configuration or quality of the subassemblies. The main actuator of a modern LPG (Liquefied Petroleum Gas) system is the vapor phase injector. These systems are commonplace because of the possibility of a modification of the mixture composition in order to meet the emission standards. Multitude of injector design solutions and quality of their workmanship frequently make them the main reason for system malfunction, hence, the need to apply simplified research methods in the course of operation that would allow an assessment of their technical condition. The paper directly compares selected research procedures evaluating their applicability. The proposed method of pressure measurement at the outlet of the injector nozzle turned out to be sufficient for a non-invasive assessment of the technical condition of the injector, which was confirmed by the measurement of the injector piston lift by the displacement sensor. The current on the power line and the vibrations of the injector housing have been sufficient to diagnose the subassembly, thus supporting the decision on the extent of the repair. [ABSTRACT FROM AUTHOR]

In this work, amplification units made of robust metallic nickel titanium (NiTi) and single crystal silicon are compared and evaluated for the application in miniaturized piezoelectric actuators for flow control purposes. The amplification mechanism with a sliced membrane structure is based on a mechanical lever in order to amplify the low piezoelectrically induced deformation. Therefore, an enhanced output stroke can be provided up to high frequencies. The different membrane fabrication processes using laser ablation for the NiTi alloy and deep reactive ion etching for the silicon substrate, as well as the results of finite element simulations and experimental measurements are reported. An amplification factor of 9 has been achieved for an optimized load transmission point position. The dynamic response shows a quality factor of 25 and 494 at the first fundamental mode for NiTi and silicon membranes, respectively. Compared to silicon, NiTi shows enhanced properties against failure and facilitates the integration process. [ABSTRACT FROM AUTHOR]

Copyright of Mechanika is the property of Mechanika 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.)