This paper presents the implementation of a two degree-of-freedom magnetic levitation system employing one permanent magnet linear synchronous motor, and the experimental validation of a mathematical model previously derived. The paper focuses on showing the development of a calibration procedure to estimate model parameters and its subsequent use for model verification. Experimental results show that the proposed mathematical model accurately describes the dynamics of the system over a wide operating range showing promise for the future implementation of nonlinear controllers.
We investigate the utility of digital holographic interferometry for analyzing gravity-dependent mass transport phenomena as applicable to materials and life science research topics. Digital holography is useful for measurement of parameters that introduce phase changes in light traversing the material of interest, such as temperature or concentration variations in an aqueous environment. We have constructed, tested, and verified a compact, portable digital holographic monitor (DHM) suitable for characterization of transparent samples. It has proved useful for the study of systems such as protein crystal growth solutions and has been proposed for further application into studies involving microbial metabolism. The DHM is also sufficiently rugged for field operation in challenging environments a s may be encountered in a spacecraft or industrial setting. We discuss some system capabilities and limitations.
This article addresses the use of electro-mechanical impedancebased structural health monitoring for assessing damage in a woven ceramic matrix composite consisting of a silicon carbide fibers and silicon carbide matrix. Controlled levels of damage were induced by conducting quasi-static, load/unload/reload tensile tests. The specimen's localized mechanical impedance was assessed using piezoelectricceramic patches that act as both actuator and sensor. The impedance results were correlated to damage and compared to acoustic emissions data, stress-strain response, and data from previous studies concerning the material system. The impedance data was shown to correlate well with the progressive damage mechanisms within the composite material system.
This work focuses on investigating the effects of thermal cycles in the impedance-based damage detection performance of Macro-Fiber Composites (MFC). A host structure with an MFC bonded to its surface is submitted to a 90 minutes temperature cycle that varies from -20ºC to 65º C. After each cycle the electrical impedance of the test sample is measured with and without the presence of a representative damage (an added mass). The results indicate that the thermal cycling affects the smart device by changing its impedance profile, a phenomenon that should be taken into account in damage detection algorithms.
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