A piezoelectric spherical motor with two degree-of-freedom

A novel ultrasonic spherical motor is presented in this paper. With only a single moving part (rotor), the spherical motor is capable of providing two-DOF (degree-of-freedom) motions required for micro-satellite and space robot actuation. The operating principle of the motor is elaborated and an initial prototype was fabricated and tested. The elliptical trajectories of the rotor tip were demonstrated by making use of two MTI Fotonic 2000 displacement probes. The feasibility of the operating principle was verified using a normal ball bearing held on to the top of the rotor, and a fast spinning of the ball-bearing occurs at resonance frequencies of 10.67, 18.9 and 29.9 kHz, respectively. Finally, further improvement issues of the motor are briefly discussed. (C) 2001 Elsevier Science B.V. All rights reserved.