Robust Nonlinear Control of a Voltage-Controlled Magnetic Levitation System with Disturbance Observer

This paper considers the control problem of a popular magnetic levitation system, which is open-loop unstable and strongly nonlinear associated with the electromechanical dynamics. The system dynamics is governed by a third-order nonlinear differential equation. The overall controller is designed through a backstepping manner by combining both the robust control and disturbance observer techniques. With the help of nonlinear damping terms, the input-to-state stability (ISS) property of the overall nonlinear control system is proved. Rigorous analysis of the ISS property is given, and experimental results are included to show the excellent position tracking performance of the designed control system.