Adaptive Current-Loop Design for an ElectroMagnetic Suspension System

Abstract

In this paper, the performance of the traditional linear current-loop strategy of a single-point Electromagnetic suspension system is analyzed and its disadvantages in application is pointed out. It is concluded that the time constant of the resultant voltage-current subsystem varies as the changes of the suspension states, which will destroy the condition of implementing model reduction by the method of current-loop and bad performance of the suspension system occurs in return. To guarantee the performance of the currentloop strategy, an adaptive current-loop is designed, the parameters of which can be adjusted automatically according to the suspension states of the system. Experimental results verify disadvantages of traditional current-loop strategy. And simulation is conducted to evaluate the performance of the proposed adaptive current-loop algorithm, the results of which illustrate that consistent performance can be obtained under different conditions of the suspension states, and it has better robustness compared with the traditional current-loop strategy. Keywords-adaptive control; current-loop; EMS maglev train I.INTRODUCTION ElectroMagnetic Suspension (EMS) is a kind of maglev techniques, utilizing the attractive force between the electromagnets on the vehicle and the ferromagnetic guideway for suspension. As it is proverbial, EMS system is inherently unstable. Suspension control is indispensable in this kind of maglev system. Also it is well-known that the model of EMS system is complicated and highly nonlinear, which makes the design of suspension controller for EMS system quite challenging [1].As a kind of transportation, there are strict performance requirements for the suspension controller of EMS system. To obtain a satisfying controller, more and more control strategies have been introduced, such as PID control, state feedback, optimal control, robust control, feedback linearization, and so on. However, some algorithms will results in a quite complex controller when applied to the original full-state mathematical model of the suspension system. For control implementation, methods of model reduction should be introduced to simplify the mathematical model of maglev suspension system. Hereinto current-loop strategy is an effective method of model reduction for maglev suspension system, and it has been widely utilized [1] [2]. The mathematical model of a maglev suspension system is usually described as the combination of electric dynamics and Kinematic dynamics. By using current-loop strategy, the response speed of the electric dynamics can be greatly

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“…To obtain a stable controller of EMS Maglev system, many control methods such as PID control, state feedback, optimal control, robust control, feedback linearization have been introduced. However, some control methods show the poor performance of suspension control [6][7][8][9][10].…”