Position control of ultrasonic motors using two-control inputs H∞ controller

The ultrasonic motor has nonlinearity characteristics, which varies with driving conditions associated the variations of temperature and applied load torque of USM. The nonlinearity characteristics for actuators are problem in accurate position control. To improve the control performance of the ultrasonic motor, we apply two-control inputs H_∞ controller for position control of the USM. Applying an H_∞ methodology we derive a stabilizing controller to meet design objectives and robust stability and performance against such variations. Using two-control inputs improve the position tracking ability of USM. The validity of the proposed method is confirmed by experimental results.