Adaptive Levitation Control Of High Speed Maglev Train Based On Cascade Transformation

The electromagnetic levitation system is a key subsystem to ensure the safe and reliable operation of high-speed maglev trains.As everyone knows,the electromagnetic levitation system of a high-speed maglev train is an open-loop unstable system,the allowable suspension distance is extremely small,and the requirements for the controller are relatively strict.We notice that the electromagnetic suspension system has characteristics of non-cascading and high nonlinearity.It is difficult to analyze stability by combining the motion loop and the control current loop dynamics of a suspension system,and the analysis method of a linear system cannot be used to this system.Therefore,it is challenging to design a highly reliable suspension controller to maintain stability of the electromagnetic suspension system.In addition,many suspension controllers designed by previous studies are relatively complex.In view of this,the main work of this thesis includes the following four aspects:(1)Based on a single electromagnet suspension model,this thesis adopts a new type of cascade transformation to convert a complex non-cascade nonlinear model of the electromagnet suspension system into a standard cascade model,which lays the foundation for research on this work,and reduces complexity of the suspension controller design.(2)Considering that uncertain variation,such as mass,electromagnetic load and electromagnetic parameters of high-speed reluctance motor,might cause severe change of suspension gap,several parameter adaptive laws are designed in this thesis to estimate unknown parameters online.In order to reduce complexity of the suspension controller design,this thesis adopts a backstepping design method to design an adaptive suspension controller to ensure stability of each link of this system under a unified architecture,so that this suspension system is always asymptotically stable.(3)In view of the problem that it is difficult to get air gap change speed of a highspeed maglev train,an adaptive high-gain observer is used in this thesis to estimate the vertical speed of levitation distance,while considering parameter uncertainty,combined with a backstepping design method,a speed-sensorless adaptive backstepping suspension control scheme is established,which further verifies feasibility of this design of the suspension controller based on a cascade system.(4)Consider that the high-speed maglev trains might suffer from severe external disturbances,this thesis considers the existence of external disturbances and the uncertainty of parameters,and combines a backstepping design method to establish an adaptive backstepping suspension control scheme based on the disturbance upper bound method.Through this scheme,the adverse effects of external disturbances on the suspension control system are effectively reduced,and bounded stability of this system is ensured.Finally,based on the Matlab simulation platform,the performance of the above three adaptive backstep suspension controllers is validated through simulation experiments under different conditions.Even if large step change of the electromagnetic levitation system parameters or severe impact on the track surface appears,the proposed controller can still ensure that this electromagnetic levitation system has a strong selfrecovery ability.20 figures,3 tables,and 52 references.