Accurate position tracking control of a moving stage using an electrorheological fluid clutch

Accurate position trajectory control of a moving stage is undertaken by utilizing an electrorheological (ER) fluid clutch. A new type of bi-directional ER clutch is devised and its field-dependent torque transmission is empirically evaluated. A sliding mode controller integrated with a full-order observer is formulated to achieve position tracking of the moving stage. In order to compensate for nonlinear friction components, the sliding mode controller is augmented with a feedback friction compensator. In the synthesis of the controller, the variation of moment of inertia of the moving stage is treated as a parameter variation to guarantee robustness of control. The proposed control system is experimentally realized, and tracking control responses for step and sinusoidal trajectories are evaluated in the time domain.