P3M-2 Dynamic Analysis and Optimal Design of a Novel Small 2-D Planar Ultrasonic Motor

The application of small planar moving motors with compact configuration and accurate movement to the field of precision machine is to be expected. The present motors and actuators for these purposes are mainly rotary electromagnetic motors with leading screw or linear electromagnetic motors. However the structures of these kinds of motors are usually complicated and it is difficult for miniaturization. This paper deals with the principle, optimization, and performance testing of a novel small X-Y multi-DOF ultrasonic piezoelectric planar motor which is composed of a square metal framework and six sets of piezoelectric ceramics plate affixed to it. Two useful natural modes of square structure were selected - the first contour mode and the second flexural mode to form the elliptical motion required by ultrasonic piezoelectric motors operating. The desired driving frequency of the motor is 20 kHz~40 kHz, while the two vibration mode frequencies were only 9.48 kHz and 11.98 kHz respectively in the initial model. Thus, the purpose of this paper is to improve the structure to get higher natural frequencies and ensure the two mode vibration frequencies equal or close so as to achieve fine driving action. The sensitivity analyses on each major parameter are conducted via FEA with ALGOR, and the geometry is optimized. As the results of the resonant frequencies and the associated modes of the final design chosen for prototype, the two modes are very close together near 25 kHz. The geometry is 27 mm length, 27 mm width, and 4.5 mm height. The prototype has been fabricated for performance experiment. Results from measuring the motor demonstrate the 2-D actuation characteristics and moving stability are improved greatly than the early one