Optimal Control of Electromagnetic Suspension EMS System

Abstract

This paper presents the controller design of magnetic levitation application. The highly nonlinear electromag- netic suspension EMS system is hard and limited system control subjected to prescribed stability of system. Due to the nonlinear dynamics of system, the linearization of the nonlinear EMS plant is described by linear model. An attraction force about the prescribed nominal operating point of current and air gap positioning is chosen for linearization by a nominal operating point. Optimal control is applied for controlling nonlinear dynamics of EMS plant. Linear quadratic regulator (LQR) controller applies for this control objective. The system stability is proofed by using Lyapunov's method. From the results the reference of air gap position can be tracked with the desired nominal operating control as shown in simulation and practical manner. Electromagnetic suspension EMS system is significantly applied in advanced technology such as ground transporta- tion, magnetic bearing and other applications. Control of electromagnetic suspension EMS system is a key technology but has some difficulties due to its nonlinearity, instability, and uncertainty. To overcome the problems mentiond. This research focuses on designing the control system for increas- ing the performance of EMS system. Normally many re- searchers applied the nonlinear control for EMS system. From references (1) proposed nonlinear state and output- feedback H ! controllers to suppress guide way induced dis- turbances. From experiment result, air-gap position can be controlled at 4 mm at nominal operating point. (2) also pro- posed the designed linear quadratic state feedback regulator. It can maintain the closed-loop stability in the presence of some certain actuator failures. The control of such a system is applied to fault control application of electromagnets sus- pension model of maglev train. The simulation study of the design is done by numerical study of magnetic levitation model in linear model. (3) presented the results on the robust stabilization of a class of feedback linearized nonlinear sin- gle-input/single-output (SISO) systems with parametric un- certainty. They implemented of nonlinear feedback lineariz- ing control for an electromagnetic suspension EMS system. Comparison on the technique of feedback linearization and classical state feedback control by using linearization with small perturbation is demonstrated by practical experiment. They concluded that feedback linearization control yielded the stable control of tracking at air gap reference, while the classical state feedback control using linearization at small perturbation could not keep system stable. The model of dy- namics and control of electromagnetic suspension is de- scribed by (4). And (5) also proposed the applied magnetic levitation for educational purpose. They described the opera- tion of a pulse width modulation converter in a magnetic suspension system. The pulse width-modulated (PWM) con- verter illustrates modern principles of power electronics, such as PWM control, current-mode control, averaged and linearized models of switched-mode converters, and power supply design. The experimental system shown the levitation control with diameter 6 cm and weight 0.8 kg of a metallic sphere. (6) applied the laser displacement measurement for the feedback control of air gap of magnetic levitation and suspension system. Then system is increased the accuracy and smoothness of control output signal due to the high reso- lution of feedback measurement device.