Robust precision positioning control on linear ultrasonic motor

Ultrasonic motors used in high-precision mechatronics are characterized by strong frictional effects, which are among the main problems in precision motion control. The traditional methods apply model-based nonlinear feedforward to compensate the friction, thus requiring closed-loop stability and safety constraint considerations. Implementation of these methods requires computation power. This paper introduces a systematic approach using piecewise affine models to emulate the friction effect of the motor motion. The well-known model predictive control method is employed to deal with piecewise affine models. The increased complexity of the model offers a higher tracking precision on a simpler gain scheduling scheme.