CHARACTERISTICS ESTIMATION OF A TRAVELING-WAVE TYPE ULTRASONIC MOTOR

The purpose of the present paper is to propose a method of calculation of load characteristics for a traveling wave type ultrasonic motor (TWUM). A method using an equivalent circuit is proposed for estimating the performance of the motor. Using this method, a systematic approach is achieved for estimating the performance, including the electrical and the mechanical parts of the motor. In the proposed method, a governing equation of the motor is derived to describe the relation between the applied voltage at an electrical terminal, vibration velocities, and the external forces at mechanical terminals of a vibrator. An estimation method of the forces between the rotor and the vibrator of the motor is revealed to calculate the load characteristics. On the basis of the proposed method, the load characteristics are numerically calculated and compared with the measured ones. Since the calculated load characteristic curves agree well with the measured ones, the validity of the proposed method for estimating the load characteristics is confirmed.