Position control method for ultrasonic motors based on beat traveling wave theory

Focusing on the application demand of ultrasonic motors in the field of space laser communication, a position control method is proposed in this study. Unlike other existing localization methods, this method is based on beat traveling wave theory, which possesses a particular performance in ultrasonic motors. In order to make the speed predictably drop to zero, the frequency difference of the two-phase drive signals is changed during normal operation. This motor deceleration stage is used to establish the positioning scheme. According to this scheme, the finite element analysis with commercial software ADINA is utilized to study the positioning characteristics and support the feasibility, adding details to the scheme. An experimental setup that depends on a DDS signal generator is built to validate this method. The data proves that it can achieve effective average results of about 15 arc-sec under open-loop control at low speed and fluctuate within 0.5 mrad, which can meet the requirement for engineering. Compared to conventional position control methods, it has attractive features of short positioning time, noiseless operation and simple control. This method provides selectivity for engineering applications of ultrasonic motors.