Robust Control of Magnetic Levitation Systems Considering Disturbance Force by LSM Propulsion Systems

In this paper, the robust control method is proposed for air-gap positioning of magnetic levitation systems considering levitation disturbance forces caused by propulsion systems. Even though the disturbance effect occurs inevitably by propulsion systems, it is very difficult or impossible to be measured by sensors in real time. In order to maintain the constant air-gap position according to the reference command in the propulsion state of the vehicle, robust control for electromagnetic suspension against levitation disturbance force is highly required. The disturbance force caused by propulsion systems is predicted by the finite-element method analysis of the magnetic flux distribution. Based on the analyzed result, the robust and optimal levitation controller is designed by the convex optimization method for the proposed proportional integral derivative controller with the inner feedback compensator stabilizing the nonlinear plant. The proposed controller has the formulation of the conventional full-state feedback optimal controller based on state-output matching for the unmeasured state. The effectiveness of the proposed controller is verified by simulation and finite-element method analysis.