Abstract
The proposed disc-type ultrasonic actuator is made of a piezo buzzer element (diameter is 41 mm, thickness is 0.2 mm). It can be made as “4 bolts -θ-structure mode” actuator by fixing four bolts arranged in “90°- 90°-θ- (180°-θ)”along the border of actuator. The driving performance of different structure mode actuators will be different corresponding to angleθ. The angle 45° structure mode actuator whose driving abilities in both directions are getting close significantly is very suitable to be used as linear stage’s actuator.This research also investigates the relationship between wear and driving ability through experiments. The driving ability of ultrasonic actuator will be affected by wear, especially on the transient response. The wearing influence can be compensated by closed-loop controller, but the more wear the more accuracy reducing.An adaptive fuzzy sliding mode controller is designed for ultrasonic actuator stage through the following two steps: first, derive a new variable (sliding surface) instead of two variables ( & ) to simply fuzzy system; then, develop an adaptive law based on Lyapunove theory to adjust the control parameters corresponding to membership functions of output part. Applying this adaptive fuzzy sliding mode controller to actuator stage, the accuracy can reach 1μm for position control, errors can be limited within 25μm for tracking. While wear reaches 1.5 mm, the accuracy will be about 2.5μm for position control, errors will be limited within 40μm for tracking. The results of experiments show that adaptive fuzzy sliding mode controller is able to compensate the effects caused by both wear and varying load, and suitable for ultrasonic actuator stage.Another way, this study makes difference on driving circuit by designing one-power-driving instead of three-power-driving. This will improve whole driving performance as well.