AN ESTIMATION OF LOAD CHARACTERISTICS OF AN ULTRASONIC MOTOR BY MEASURING TRANSIENT RESPONSES

To measure the characteristics of ultrasonic motors, such as the maximum torque, torque-speed relationship and the frictional coefficient at the contact surface, a method in which the torque is calculated from the transient responses is proposed. The rise curve that is the transitional change in the rotor speed soon after turning on the motor gives the load characteristics, while the fall curve that is the decay of the rotor speed after turning off the motor yields the frictional coefficient of the contact surface. This method requires only a short time (the transient time of the motor) to complete the measurement. After analyzing the relations between the transient responses, the load characteristics and the frictional force, this method is applied to a hybrid transducer type rotary motor and a traveling wave type linear motor. The load characteristics of the rotary motor is given by the present method and various kinds of frictional materials for the linear motor are examined.