Vibration isolation of an electromagnetic actuatorwith passive gravity compensation

A control strategy of combining H_¿ control and feedback linearization was applied to the model of a highly nonlinear, three Degrees-Of-Freedom (DOF) electromagnetic actuator, which was recently designed for non-contact suspension of a large payload. The new electromagnetic actuator has the advantage of passive gravity compensation based on permanent magnets with low stiffness and high force density. But the nonlinearity is so high that the stability status along each DOF changes while the translator is traveling within the working range. Feedback linearization method was used to compensate the nonlinearity, a stabilizing controller was employed to eliminate the slow-varying calculation error of the passive force, and an H_¿ controller was designed for vibration isolation. Simulation results show that the proposed control strategy has robust vibration isolation performance within a working range in which the relation between the magnetic force and the relative position is highly nonlinear.