Robustness of Magnetic Levitation by Using Feedback Linearization Back-Stepping and Nonlinear Disturbance Observer

In this paper, the position tracking problem of a magnetic levitation system with the external disturbance and uncertainties is investigated. The dynamic of a magnetic levitation is governed by a SISO third-order nonlinear differential equation and only the position measurement is available for control. In this paper, the combination of the feedback linearization and Back-stepping techniques is used as a new control method for this system. Feedback linearization and back-stepping techniques are introduced as methods for linearization of a system with coordinate transformation and nonlinear designing, respectively. In other hand, nonlinear disturbance observer has a good ability to estimate disturbances and nonlinear dynamics, so it is combined with designed controller to increase performance of the controller, reducing the effects of disturbances and system uncertainties by estimating them. Simulation results show that the proposed method has a good ability in the position tracking and a good performance in elimination of the external disturbance and uncertainties.