Nonlinear disturbance rejection for magnetic levitation systems

In this paper, a position regulation control strategy is developed for a magnetic levitation system operating in the presence of a bounded, nonlinear, periodic disturbance. The proposed controller utilizes a saturated control force input in conjunction with a learning based disturbance estimator to asymptotically regulate the target mass to a desired set point position despite. the actuator´s unidirectional limitation of exerting only an attractive force on the target mass (i.e., the control input can only generate an attractive force while the earth´s gravitational field is utilized to produce the repulsive action). In addition, the control development only requires the disturbance input to be bounded and periodic in nature. Simulation results are included to illustrate the performance of the control strategy.