Robust control of flexible rotor-magnetic bearing systems using discrete time sliding mode control

This paper is concerned with the computer-based sliding mode control of flexible rotor-magnetic bearing systems (FR-MBS). The plant dynamics consisting of actuator dynamics and flexible rotor dynamics are described. The reduced-order model for controller design is given by eliminating higher-order modes of the mechanical and electrical magnetic interaction system. A discrete time sliding mode controller with reduced-order model is proposed and its robust performance is evaluated with several simulations based on a calculation model. This digital controller is implemented to replace a linear analog PID compensator. Levitation tests using the proposed digital controller are performed and compared with those of the PID compensator. With a discrete time sliding mode controller, the running test with high-speed rotation is successfully increased up to 35 000 rpm without unstable vibration.