半径方向運動誤差補正可能な非接触超音波モータの開発

概要

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Real-time motion error correction of a rotor driven by a non-contact ultrasonic motor (non-contact USM) was achieved. The rotor is installed in the cylindrical stator with a small gap designed to have a resonance frequency of 23.9kHz at the 8th flexural mode of vibration. The multi-layered piezoelectric actuators excite the flexural wave traveling in the circumference direction. The ultrasonic vibration produces a sound field to levitate the rotor and the traveling wave induces near-boundary streaming to rotate the rotor by viscous force. Herein, we report the experimental performance of the non-contact USM. When the amplitude of the flexural vibration was 0.3μm, the rotational speed was 4rpm. The rotational speed and starting torque were proportional to the vibration amplitude. The staring performance of rotational speed was consistent (time constant=2 sec) for various vibration amplitudes, hence the rotational torque is independent of the rotational speed and the resistance forced on the rotor is governed by viscosity. In addition, the non-contact USM allows contact-free micro positioning of the rotor by control of the deformations of the piezoelectric actuators. A PI controller was constructed to compensate the detected motion error of rotor in the radial direction. As a consequence, the motion error of 0.8μm for a rotor revolution was reduced to within ±0.1μm.
公益社団法人精密工学会の論文
2005-01-05