The Study Of Ring-Type Travelling-Wave Ultrasonic Motor With Multi-Electrodebased On Space Phase Shift

The ultrasonic motor (USM) that appeared in 80th of last century is a novel micro motor, who utilizes the converse piezoelectric effect and the friction coupling operation between stator and rotor to drive, that is quite different from traditional electro-magnetic motor. With the study of traditional ring-type travelling-wave USM (RTWUSM), a novel RTWUSM based on space phase modulation (SPC-RTWUSM) is designed, the optimized structure and control method of SPC-RTWUSM is also applied. As the help of multi-electrode, frequency-tracing of RTWUSM is studied. According to the structure errors of SPC-RTWUSM, correction methods based on double reaction theory is discussed. The main content of this paper is summarized as follow:Based on the principle of waveform superposition, with new piezoelectric ceramic electrode configuration and power supply, the initial scheme of SPC-RTWUSM is obtained. The ceramic electrode configuration and the link of powers are complex in the initial scheme. With the position optimization of ceramic electrode, a utility of scheme who can simplify the configuration of ceramic electrode and the link of powers comes into being. In order to reduce the number of powers, three powers scheme for SPC-RTWUSM is introduced too, and the new control methods and the new ceramic electrode configuration is applied to perfect the positive and negative rotation control. With the study of amplitude control and space phase control, the phase-amplitude control of SPC-RTWUSM is developed. Simulation and experiment results confirm the theory of SPC-RTWUSM and the theory of phase-amplitude control.The non-working mode of stator is used, and the RTWUSM frequency tracking scheme based on the multi-electrode signals is studied. Modal analysis of three-dimensional finite element around the working frequency is adopted. The analysis shows the vibration amplitude is not the same in different space phase, which is due to the different modal shape. Theoretical analysis and harmonic analysis show that the difference-signal between multi electrodes changes linearly with the change of power frequency in a certain range. The influence of electrodes configuration, structure errors of stator, temperature, pre-pressure is also analyzed. Experiment results confirm the scheme of RTWUSM frequency tracking.As the ability of "moving" standing wave, the correction methods of structure errors for SPC-RTWUSM are designed. The wave form influenced by the structure errors in stator is analyzed. With the help of two axes stationary reference frame and the help of double reaction theory, theory of elimination-correction and theory of compensation-correction for structure errors are derived. In order to ensure the consistency of correction effect, selection criteria of the correction scheme, expression of standing wave due to structure errors, and the correction flow of SPC-RTWUSM’s structure errors are derived too. Harmonic analysis and experiment results confirm the correction scheme for SPC-RTWUSM’s structure errors.