On independent position/gap control of a spiral motor

This paper presents a full direct-drive motion of a spiral motor. Spiral motor, is a novel high thrust force actuator with high backdrivability, consists of a spiral structure mover and stator. The mover moves spirally in the stator, and the linear motion is extracted to drive the load. A proper gap control against the load fluctuation is needed to achieve full direct drive motion. In this paper, an exact feedback linearization engaged with DOB is used to achieve independent position/gap control of a spiral motor. Through the use of high gain feedback time scale separation is artificially introduced and the overall closed-loop system is transformed into a singular perturbation one. Then, using tools from singular perturbation theory, the proposed method ensures arbitrary disturbance attenuation, small tracking error, and boundness of all closed loop signals. Finally, simulation results are given to verify the theoretical one.