Zero Power Control Based on External Force Feedback for Helical Motor

Abstract

For an assist device, a safe and compact high output actuator is desired. The authors have proposed a helical motor that consists of a helical mover and stator. In the gap control of this motor, zero power control is applied to save power for magnetic levitation. However, when a disturbance force is imposed upon the motor, the gap response with the zero power controller has an inverse response. To solve this problem, a new zero power control based on external force feedback is proposed, which is used to generate both the gap displacement and gap velocity references. Experimental results and a mathematical analysis show that the proposed method suppresses the inverse response well in position control and force control.