Micro-Nanometer Positioning Control of Bimodal Ultrasonic Motor Based on Wavelet Differential Actuation Pattern

This paper has developed the bimodal USM a novel actuation pattern, which can actuate the bimodal USM in nanometer magnitude with single actuation pattern instead of combination control of AC actuation pattern, pulse actuation pattern and DC actuation pattern. The novel actuation pattern utilizes a single chip micro-computer to produce a kind of wavelet actuation unit which contains several sine voltage waves with different amplitudes, each wavelet actuation unit is exerted on bimodal USM according to the instruction, by which the step control is obtained. Across the two electrodes of bimodal USM, the differential wavelet actuation voltages are applied to reduce the moving distance of each actuation step, thus the nanometer magnitude actuation sensitivity is achieved. The grating is used as position sensor and the subdivision formulae of mutual compensation functions are adopted to promote the real-time response. The experiment indicated that, with the novel wavelet differential actuation pattern, the actuation characteristic of bimodal USM was improved, the micro-nanometer positioning control was easy to be implemented and the important positioning control parameters under every different actuation conditions could be obtained through the study in the process of actuation.