Robust control for ultrasonic motor operating within harsh environments

Ultrasonic motor technology is a key system component in integrated mechatronics devices working on extreme operating conditions subjected to thermal cyclings or large thermal variations, EM disturbances, radiations, corrosion, or strong vibrations. Due to these constraints, robustness of the mechanics/electronics/control interfaces should be taken into account in the motor design. A robust controller for a travelling wave ultrasonic motor (TWUM) is considered in this study for operation in extreme environmental conditions. A simple causal model of the TWUM is introduced for identification of motor parameters. Then, an H_infin loop shaping 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 robust controller in extreme operating conditions.