Accurate Parking Control For Urban Rail Trains Via Robust Adaptive Backstepping Approach

In recent years,as the scale of China’s urban rail transit industry continues to expand,urban rail transit systems are also developing rapidly in the direction of more automation,intelligence and higher performance.Accurate parking on the platform is one of the important goals to realize the automatic control of urban rail trains,and the parking accuracy of the train platform is usually required to be within ±30 cm.If the train stops at the platform inaccurately,it will not only affect the passengers getting on and off,but in severe cases,the platform screen door will not be able to be opened,reducing the operation efficiency of urban rail transit.Therefore,the problem of precise parking control of urban rail transit trains is studied in this paper,the factors that affect the precise parking of trains are deeply analyzed,and a more refined dynamic model of urban rail train braking system is established.Based on this model,an operation controller that can ensure the precise parking of the train is designed.The main research contents of this paper are as follows:(1)Combined with the structure and composition of the automatic train operation control system,the automatic parking process of the train is described.At the same time,the factors affecting the precise parking of the train are analyzed in detail from the aspects of speed measurement and positioning accuracy,basic running resistance,and braking system characteristics.This part of the work provides the basis for the subsequent construction of the train braking system dynamics model.(2)First of all,combined with the analysis of train dynamics and dynamic characteristics of train braking system in the process of parking,comprehensively considering the first-order inertia characteristics of the braking system,the nonlinear characteristics of brake shoe friction coefficient and the uncertain running resistance of the train,a third-order braking system dynamic model with uncertain nonlinearity is proposed.Secondly,based on the model,a robust adaptive inverse parking controller is designed with backstepping technology.The controller compensates the system uncertainty caused by brake shoe with the robust term,and estimates the unknown parameters in the system model with parameter adaptive laws.Then,the convergence of tracking error and the stability of closed-loop system under the action of the proposed controller are analyzed and proved.Finally,based on the MATLAB simulation platform,the control effects of the proposed controller and the PID controller are compared and experimentally verified.The simulation results show that the ride comfort and parking accuracy of the vehicle are better under the action of the proposed controller.(3)First of all,the time-delay phenomenon in the train operation control system and the input saturation constraint of the train braking system are further studied,and the dynamic model of the braking system is optimized.On this basis,the Pade approximation method is used to deal with the input time-delay,and a new auxiliary system design method is introduced to construct the coordinate transformation form of the state variables.Then,combined with backstepping technology,a robust adaptive backstepping controller is designed.Then,the convergence of the tracking error and the stability of the closed-loop system under the action of the controller are analyzed and proved.Finally,based on the MATLAB simulation platform,the control effects of the proposed controller and ANN controller are compared and experimentally verified.The simulation results show that the proposed controller can keep good tracking accuracy and stability under the influence of input delay,and achieve the parking error control within 30 cm.This is of great significance for improving the operational efficiency of the urban rail transit system.