Modeling and sliding-mode control of friction-based object transport using two-mode ultrasonic excitation

This paper introduces a magnetic-free object transport system driven by a friction force on an ultrasonic flexural vibrating beam. This driving mechanism offers unique advantages of silent operation and lubricant-free structure. The characteristics are ideal for a transport system in a clean-room environment. However, the friction drive described by Hertzian contact and Coulomb friction theories is highly nonlinear. The transport system needs a sophisticated control design to deliver a load to a precise location. A traditional feedback controller and sliding-mode control were implemented in the presence of sensor noise and hardware limitation. It is experimentally shown that the tracking performance of the proposed control scheme is superior to the traditional control design.