Proceedings of JSPE Semestrial Meeting

Wide-gap semiconductor material substrates (i.e. SiC and GaN), which have been attracted attention as a future high-performance and multi-functions semiconductor, are being developed as a part of the high-efficiency and high-quality polishing process development. In this paper, I describe the research and development of the polishing process using the originally developed high rigidity high rotational speed/ pressure polishing equipment and the innovative special dilatancy pad in which is aiming to achieve for both a high efficiency and high quality polishing.

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Hard-type piezoelectric materials have been utilized in various high power applications, in which usually requires to be driven under high vibration level. However, under high stress piezoelectrics show significant nonlinear behavior, which should be taken as one of the criteria. In this study, nonlinearity in lead-free CuO-(K,Na)NbO3 transducers was investigated. The CuO-(K,Na)NbO3 transducers were cut from ceramics, which were fabricated via hydrothermal method. In the burst mode measurement, the transducers after excited by a burst excitation began free vibration. The equivalent mechanical loss and the reciprocal of equivalent stiffness were determined by velocity decay rate and resonance frequency, which were given by the velocity-time curve. The admittance curves of the transducer under high voltage were also measured via a frequency response analyzer. In the admittance curve, around the resonant frequency the values are not consecutive (jumping phenomenon); also a hysteresis appears between upward and downward sweeps, indicating the existence of nonlinearity. A model containing the nonlinear terms was proposed and adopted to fit the admittance curves. From the curve fitting the nonlinear coefficients and force factor could be determined and compared with those of Pb(Zr,Ti)O3 transducers.

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This research targets to develop a new type of high power piezoelectric actuators. We employ a new type of displacement amplifier mechanism named "buckling" which has more than 50 times of the amplification ratio with 0.7 of the energy coupling ratio. 5 mm of the amplified displacement allows to drive a rack continuously with an orchestration among several units of them. We employ a sinusoidal track on the rack and rolling contacts to every single joints in the motor. A static motion analysis shows the motor has a linear force/torque controllability with sinusoidal voltage inputs with zero ripple theoretically. This feature differentiates the motor notably from ultrasonic motors which has a discontinuous motion property relying on the small piezoelectric displacement and friction.

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