Evaluation of spherical ultrasonic motor for space in low temperature condition

Abstract

A spherical ultrasonic motor for space has been developed by this investigation. Development results of the spherical ultrasonic motor which can be driven under the high temperature environment of the atmospheric pressure were described by previous paper. The results about developed spherical ultrasonic motor which was investigated in the environment of low temperature and temperature cycle are described by this paper. First, it was confirmed that the spherical ultrasonic motor drives in low temperature environment of −120 °C. When durability tests for the spherical ultrasonic motor were carried out in temperature of −80 °C, approximately 60 minutes as accumulated drive time was achieved. Further, freezing phenomenon occurred on a sliding surface between stator and spherical rotor of the spherical ultrasonic motor, and drive of the spherical ultrasonic motor was disturbed. Next, when a drive experiments about the temperature cycle were carried out, influence of the temperature cycle to a torque was small. It was confirmed that the rotational speed decreases by the decline of piezoelectric of a piezoelectric element and the decline of the hardness of the adhesive to which a piezoelectric element and an elastic body are attached in high temperature environment. On the other hand, it was confirmed that the rotational speed decreases by the freezing which occurs on the sliding surface and the influence of the characteristic of the piezoelectric element in low temperature environment.