  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 complex
designed experiments. 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.
