Congyu Xu

Novel control method of bimodal ultrasonic motor based on wavelet differential pattern

In view of bimodal piezoelectricity ceramics ultrasonic motor (USM), which is excited by the first order longitudinal vibrations modality and the first order bending vibrations modality, can not be actuated at a slower speed and its actuation sensitivity can not reach nanometers magnitude under the AC actuation pattern of USM, this paper proposes a novel control technology, which realizes the functions of the step-by-step control and differential control of USM under the original AC actuation pattern through the synthesis of wavelet actuation wave composed of several periods of sine voltage waves whose amplitudes are altered according to a certain regularity. The experiment shows that the speed of USM could be smoothly lowered by reducing the output numbers of wavelet actuation waves within a period of time combined with adopting the differential control pattern of USM, the elliptical trajectory of the actuation head of USM was altered by changing the synchronized control voltages difference across the two electrodes of USM, by which the actuation sensitivity of USM was improved greatly and therefore the actuation of nanometers magnitude was achieved .