Slip-Free Driving Method for Nonresonant Piezoelectric Actuator

It is generally considered that in the ultrasonic motor the motion always slips and scratches. The nonresonant ultrasonic motor (NRUSM) expected for future precision stage systems should, however, overcome the difficulties of the wear of friction materials, which has been encountered in the use of conventional ultrasonic motors. The wear occurs by slipping and may be reduced by material selection. In this paper, we focus on the control method at actuation to prevent slipping. The advantages of NRUSM in the ability to control the drive frequency as well as the drive amplitude are shown, and this is effective in reducing wear and obtaining long-term stability. The drive frequency condition for no slippage under sinusoidal waveforms was calculated. The experimental results correspond to the theoretical calculated drive frequency. Because the resultant values of the frequencies are low for practical applications, we present the slip-free actuation method of using the new actuator's driving waveform and time chart in order to drive the stage at constant accelerated motion.