A vibro-impact approach to PILine® ultrasonic motors

Inhalt:
Using the inverse piezoelectric effect in combination with various driving principles, several kinds of piezoelectric motors have been realised in the past. Focussing on ultrasonic motors, travelling wave and standing wave type motors can be distinguished. PILine(r) ultrasonic motors belong to the latter group and, as common for this kind of motors, use certain eigenmodes of the piezoelectric actuator to generate an oblique or elliptical motion, which is transmitted via a coupling element to a moving slider. Possible applications of PILine(r) ultrasonic motors are motion and positioning devices with good accuracy, long travel distance and a large range of driving velocities, e. g. in microscopy or medical engineering. Within this contribution, a simple mechanical model for standing wave ultrasonic motors is presented and evaluated regarding the effective driving characteristics of the motor. Subsequently, the model is extended in order to account for vibro-impact dynamics originating from the contact between coupling element and slider. Separating normal and tangential motion gives insight into relevant dynamic processes and their impact on the overall system characteristics.