Disturbance Rejection Control Using a Novel Velocity Fusion Estimation Method for Levitation Control Systems

Abstract

Magnetic levitation has been applied to maglev trains and magnetic suspension wind tunnel. However, there are some problems with the existing levitation control. For example, it is difficult to extract smooth velocity signals from the gap sensor with noise. The classical differentiator is susceptible to noise, which makes the levitation system sometimes vibrate. The accuracy and stability of levitation control need to be improved. The velocity fusion estimation method (VFE) is proposed to extract the velocity signal from the gap and acceleration sensor, which is theoretically derived to prove that it reduced the noise of the velocity signal. Then disturbance rejection control(DRC) is proposed that add VFE into classical levitation control. Because of the high-quality velocity signal and accelerometer's fast responsiveness, it makes DRC have many advantages. The advantages of using the proposed control structure are that it improved the control accuracy of the target gap and resisted disturbance effectively. Air-gap fluctuations in levitation systems can be reduced in transient pulse disturbance test, white noise disturbance test, and external force disturbance test when it applies the proposed control method. The effectiveness and advantages of the proposed control method are verified by the simulation and experiments.

A Review of Levitation Control Methods for Low- and Medium-Speed Maglev Systems

“…These methods are generally based on the single-point levitation model and assume that the levitation electromagnet and guideway are in a stable position [6]. Based on the linearized system model, this section introduces typical control methods, such as the proportional-integral-differential (PID) control [6,7,63,64], linear quadratic regulator control (LQR) [8][9][10], and state feedback control [2,37,38].…”

“…Secondly, it successfully eliminates the vibrations present in the guideway. Xia et al [37] employed the velocity fusion estimation method (VFE) in conjunction with state feedback control. The proposed controller can precisely control the air gap and effectively counteract disturbances.…”

“…In the single-point levitation model, it is assumed that (a) the magnetic field distribution in the air gap is uniform, and (b) both the iron core and the F-type rail act as ideal magnetic conductors. Based on these assumptions, a fundamental single electromagnet levitation model can be derived using Newton's law and Kirchhoff's law [34][35][36][37][38].…”

“…In the single-point levitation model, it is assumed that (a) the magnetic field distribution in the air gap is uniform, and (b) both the iron core and the F-type rail act as ideal magnetic conductors. Based on these assumptions, a fundamental single electromagnet levitation model can be derived using Newton's law and Kirchhoff's law [34][35][36][37][38].  Multi-point levitation system modeling Although we attempted to decouple the levitation system in the structure by using mechanical decoupling, it was found in a series of experiments that the coupling effect between the two levitation points in a module is too strong to be ignored [39].…”

Sliding Mode Control Design for Magnetic Levitation System

“…Due to its nature, MLS has nonlinear [24], unstable [25], and fast dynamics characteristics [26]. Thus, a suitable controller is needed to control MLS [27].…”