Stable Levitation of Single-point Levitation Systemsfor Maglev Trains by Improved Cascade Control

The stable levitation of single-point levitation systems for electromagnetic suspension (EMS) maglev trains, which belongs to the control task of nonlinear and unstable systems, is investigated in this paper. Considering the simplicity and convenience of the control application, we dedicate ourselves to combining and applying common control methods to achieve the stable levitation rather than designing complex controls or using advanced control methods. For this goal, the single-point levitation system is divided into an electromagnetic system and a motion system first. On this basis, we design the Lyapunov controller and sliding mode controller as Controller I, while another Lyapunov controller and the standard Proportional Integral Derivative (PID) controller are designed as Controller II, which are used to control the electromagnetic system and motion system respectively and constitute the improved cascade control to achieve the stable levitation. Furthermore, the switching controller consisting of the standard PID controller and the designed Lyapunov controller is used as Controller II for the improvement of both stability and robustness.