Resonant booster for driving ultrasonic motors

Ultrasonic motors have attracted considerable attention as a new type of actuator in servo-system and the on-off controlling field, but the widely-use of USMs are limited by the control circuits with transformers. Accompanying with the equivalent circuit of the ultrasonic motors, this paper has established a driving circuit using the resonant booster, which has no transformer included. The circuit, which was named resonant booster composed of inductance and capacitance, was analyzed on the theory and validated by the simulation through the software named PSPICE, and so did the experiments. Through the experiments and the analysis results we knew that the output voltage was almost linearly proportional to the driving duty ratio and inversely proportional to the square root of the series inductance. It was proved that this circuit was both feasible and reliable in the drive and control of small-power USM, for it was not necessary to track the change of the temperature of the USM inside and it was easy to feed the frequency of the USM back to the control circuit and no other feedback circuit. The driving device can be reduced one-third in the volume, one-second in the weight and one-fifth in the cost at least, when compared with the traditional controller of USM that had transformers.