Nonlinear Control of a Magnetic Levitation System Based on Coordinate Transformations

In this paper, a novel concept of nonlinear controller design is proposed, which is applicable to nonlinear systems subject to external periodic disturbances. At first, by employing a pioneering nonlinear coordinate transformation, a new nonlinear system model with expected dynamic characteristics is derived. Then, a corresponding linear system is achieved by means of linearization techniques at equilibrium points. Next, based on the results of classical linear control theory, a linear quadratic regulator is applied to the resulted linear system. Finally, the nonlinear controller can be obtained through the inverse nonlinear coordinate transformation of the linear feedback controller. The performance of the proposed method is validated on a magnetic levitation system and is compared with the classical linearization feedback control. Simulation results show that the proposed controller design assures enhanced performance in terms of both system stabilization and disturbance attenuation.