An Cascade Transformation Based Adaptive Electromagnetic Suspension Control of Maglev Trains without Speed Measurement

Open-loop instability of electromagnetic levitation systems requires a highly reliable controller to maintain a constant air-gap position. It is fairly challenging to develop such controller since the electromagnetic suspension (EMS) inherently involves nonlinear system dynamics and intercoupling among its motion-loop and current-loop dynamics. In this work, firstly a cascade transformation is introduced into dynamic equations of electromagnetic suspension, which allows the backstepping method can be directly applied to design a feasible levitation controller. Then, a speed-sensorless levitation control scheme is established by utilizing a high-gain adaptive observer to estimate the vertical speed of air-gap. It is shown that globally stable levitation control is always achieved under consideration of system uncertainty, nonlinearity, and unmeasurable state. The numerical simulations show effectiveness of the proposed control scheme.