New control method of contact force between rotor and stator on rod-type ultrasonic motor

The performance of the rod-type ultrasonic motor can be improved by controlling the contact force between the rotor and stator. In a conventional rod-type motor, the contact surfaces of the rotor and stator move in the same direction. The authors propose a new method in which the contact surfaces repulsively collide with each other. We observed the electric current passing through the contact surfaces and measured the input electric power and revolution characteristics and found that the new method offers a 50% saving on input electric power compared to the conventional type of contact force.