Drive circuit for a mode conversion rotary ultrasonic motor

Abstract

A mode conversion rotary ultrasonic motor (USM) has potential applications in miniature robotics. However, its electrical drive circuit presents some unique challenges, particularly in producing a high frequency (~40kHz), high voltage (~200V peak-to-peak) signal into a low impedance (~100Ω) capacitive motor, while achieving high efficiency. This paper describes the design of such a drive circuit, intended for use with a 12V battery. The drive circuit consists of a switch-mode power converter driving the USM via a step-up planar transformer. Compensation and resonant elements are added to improve the power efficiency. While the peak efficiency of this circuit is 45%, in practice the equivalent impedance of the USM changes with mechanical load and temperature, resulting in an average efficiency of 16%. The admittance vs. frequency characteristic and the equivalent electrical model for a USM prototype are also presented in this paper. The circuit simulations and loaded testing of a fullbridge DC-AC resonant converter with DC-offset module were performed. A load-adapted frequency tracking method has also been proposed to improve the efficiency and stability of the drive circuit.

Modeling and preliminary analysis of a miniaturized rotary motor driven by single piezoelectric stack actuator

“…In order to get rid of irrelevant details of the drive electronics and concentrate on the main purpose of current prototype development stage, the authors choose a commercial drive system for the experiment setup, as shown in Figure 6, which is large and not compatible with small-scale applications. Nevertheless, the authors believe that it would not be a real obstacle to devise a small-sized driver, because an offset sinusoidal waveform driving has been accomplished in a number of ways by other researchers (Bal and Bekirog˘lu, 2005;Chen and Lin, 2002;Manuspiya et al, 2003;Xu et al, 2005) through electronic chips such as FPGA and DSP.…”