Observation of elliptical motion in the torsion coupler of ultrasonic motor using optical heterodyne interferometer

Abstract

AbstractAn elliptical motion in the torsion coupler of an oscillator‐type ultrasonic motor has been observed noninvasively by means of an optical heterodyne interferometer. Studies of the elliptical motion in the torsion coupler are important for the research on improvement of the efficiency and optimum design of an ultrasonic motor. However, to date, only microscope observation has been carried out and hence accuracy is not as high as desired. In this paper, an optical heterodyne interferometer based on a frequency‐stabilized transverse Zeeman laser is used for detection of the Doppler shift frequency by an ultrasonic vibration so that the vibration waveform of the torsion coupler has been regenerated. The oscillations of the rotor contact plane and side plane of the end of the beam have been measured individually by an identical optical system. From their amplitudes and the phases, the elliptical loci have been computed. In another method, the oscillations of the two surfaces have been measured simultaneously with two interferometer systems and their elliptical relations have been displayed in real time on an XY oscilloscope. Oscillations at each point on the beam and the variations of the elliptical shape versus the driving frequency of the ultrasonic motor have been observed successfully by the second method.