Planar Rotary Motor Using Ultrasonic Horns

One of the first piezoelectric motor designs with significant rotational speeds was outlined by Barth. This device used extensional piezoelectric elements to produce a time varying force at a distance r from the center of a centrally supported disk. These extensional actuators produced micro-steps at a high frequency with the end result being macroscopic rotation of the disk and high torque. The rotation direction is controlled by the choice of the actuators and the direction of the extension about the rotor center. A recent advancement in producing pre-stressed power ultrasonic horns using flexures allows for the development of high torque ultrasonic motors based on the Barth's idea that can be fabricated in a 2D plate or in more complicated 3D structures. In addition to the pre-stress flexures the design also allows for the use of flexures to produce the rotor/horn normal force. The torque can be controlled by the number of actuators in the plane and the amplitude of the normal force. This paper will present analytical and experimental results obtained from testing prototype planar motors.