Mathematical model of ultrasonic motors for speed control

In this paper, a mathematical model of ultrasonic motors for speed control, which includes the nonlinearity and approximation of the dead-zone in control input, has been presented. Intrinsic property of ultrasonic motor (high torque for low speed, high static torque, compact in size, etc.) offers great advantages for industrial applications. However, speed property of ultrasonic motor has strong nonlinear property as well as the dead-zone effect in control input associated with load torque. These properties are serious problems for accurate speed control. This paper presents a mathematical model represented by sinusoidal function, which is including these properties. This model is simple and has good approximation of the nonlinearity and time varying properties. The proposed speed model has been validated by experimental results