Abstract
Since a voltage-controlled magnetic levitation system is open-loop unstable and strongly nonlinear associated with the electromechanical dynamics, it is quite challenging to apply an adaptive controller for position tracking problem mainly due to its poor transient performance. This paper proposes a combined robust and adaptive approach to a popular magnetic levitation system. The overall controller is designed through a backstepping manner by combining both the adaptive control and robust control techniques. The input-to-state-stability is ensured by the robust nonlinear damping terms whereas the ultimate control error bounds are made sufficiently small by the adaptive laws. The combined approach proposed here helps to overcome some well-known practical problems such as high-gain feedback of the robust controller, and poor transient performance of the adaptive controller. Experimental results are included to show the excellent position tracking performance of the designed control system.
