Two-Phase Stator Vibration Amplitude Compensation of Traveling-Wave Ultrasonic Motor

Abstract

The consistency of the two-phase mode responses is essential to ensure the mechanical performance and stability of traveling-wave ultrasonic motors. Due to the asymmetry of the stator, inevitable manufacturing errors, or imbalance of the excitation voltages, the amplitudes of the two-phase standing waves cannot be exactly the same, resulting in unstable operating of USM. To improve the stability of the motor and decrease the velocity fluctuation, a closed-loop velocity control scheme considering two-phase consistency compensation based on the vibration amplitude of the stator is proposed. This scheme is implemented under the framework of the stator vibration amplitude-based velocity control and parallel resonance frequency tracking (VCBVF). Based on the relationship between the velocity and stator vibration amplitude (SVA), two-phase excitation signals are adjusted individually and simultaneously. Compared with the single-phase feedback VCBVF control scheme, experimental results show that the proposed scheme can reduce the overshoot from 17.50% to 6.90% and velocity fluctuations from 7.69 rpm to 2.40 rpm, under different load torques. The proposed scheme can compensate for the two-phase electrical inconsistency and improve the velocity stability and output power of motor operation under various conditions.