A standing wave-type noncontact linear ultrasonic motor

In this study, a novel standing wave-type noncontact linear ultrasonic moto r is proposed and analyzed. This linear ultrasonic motor uses a properly co ntrolled ultrasonic standing wave to levitate and drive a slider. A prototy pe of the motor was constructed by using a wedge-shaped aluminum stator, wh ich was placed horizontally and driven by a multilayer PZT vibrator. The le vitation and motion of the slider were observed. Assuming that the driving force was generated by the turbulent acoustic streaming in the boundary air layer next to the bottom surface of the slider, a theoretical model was de veloped. The calculated characteristics of this motor were found to agree q uite well with the experimental results. Based on the experimental and theo retical results, guidelines for increasing the displacement and speed of th e slider were obtained. It was found that increasing the stator vibration d isplacement, or decreasing the gradient of the stator vibration velocity an d the weight per unit area of the slider, led to an increase of the slider displacement. It was also found that increasing the amplitude and gradient of the stator vibration velocity, or decreasing the weight per unit area of the slider and the driving frequency, gave rise to an increase of the slid er speed. There exists an optimum roughness of the bottom surface of the sl ider at which the slider speed has a maximum.