Optimum pre-load of surface acoustic wave motor

We have examined the optimum pressing force, namely, pre-load for a slider to obtain a superior operation condition of a surface acoustic wave motor. We used steel balls for sliders. With a permanent magnet the pre-load was controlled. The steel balls that we used were 0.5, 1 and 2 mm diameter to change contact conditions such as contact pressure, contact area and deformation of a stator and the slider. The stator transducer was lithium niobate 128 degrees Y-rotated X-propagation substrate. The driving frequency of the Rayleigh wave was about 10 MHz. As a result, the deformation of the stator and the slider by the pre-load should be half of the particle vibration amplitude. This condition was independent of the ball diameter and particle vibration amplitude. An output thrust force of 50 N per square mm and a maximum speed of 0.8 m/s was achieved. The surface acoustic wave motor has a high potential for realizing high speed, quick response, long traveling distance, low profile micro linear actuators.