A robust speed control architecture for ultrasonic motor

Ultrasonic piezoelectric motor is an important system component in integrated mechatronics devices working on extreme operating conditions subjected to multi-disturbance. Due to these disturbance, robustness of the mechanics/electronics/control interfaces must be taken into account in the motor design. In this paper, a cascaded H_¿ controller for a travelling wave ultrasonic motor (TWUM) is considered for wave, torque and speed loop control. To eliminate the nonlinearity, a simple causal model of the TWUM is used. Then, an H_¿ synthesis procedure is implemented in order to obtain a good compromise between environmental robustness and motor´s performances. Finally, simulation results demonstrate the effectiveness of the proposed H_¿ robust controller in the presence of multi-disturbance.