Proposition of an Er Microactuator with Inherent Position Feedback Mechanism

The paper proposes and develops a novel smart ER microactuator with inherent position feedback mechanism. The microactuator consists of a pair of movable and fixed parallel plate electrodes with variable gap length and an upstream restrictor, and ERF (electro-rheological fluid) is supplied as a working fluid. By applying voltage to the electrodes, with the increased pressure drop due to ERF viscosity increase, the electrode gap length i.e. the output displacement increases. Also the microactuator can suppress the displacement due to external force by the inherent position feedback mechanism. The mechanism utilizes increase of the flow resistance between the electrodes for decrease of the electrode gap length. In this paper, the structure and working principle are revealed and the mathematical model is derived. Then, a microactuator is fabricated and the characteristics are experimentally clarified. Furthermore, a mechanism to magnify the output displacement is proposed and the validity is confirmed through experiments.