Research On Braking Method Of High Speed Trains Based On Adhesion And Sliding Mode Control

With the increasing speed of high-speed trains,the safety of high-speed trains has been paid more and more attention.A good and stable braking system is an important guarantee for the safe operation of high-speed trains.At present,electric brake and air brake are mainly used in high-speed trains.Reasonable and effective distribution of electricpneumatic braking force is of great significance to the improvement of train brake system performance.On the other hand,the train braking force mainly based on the adhesion between the wheel and rail.However,the train operating conditions are complex and variable,and the adhesion between the wheel and rail is not easy to detect.The braking force exerted by each car is also closely related to the adhesion between the wheel and rail.Therefore,a good adhesion control method and a reasonable and effective braking force allocation strategy are very important for the safe operation of high-speed trains.Based on the existing braking force distribution strategies and adhesion control methods,the following research is carried out in this paper.For the problem that the high-speed trains electro-pneumatic braking force distribution control strategy has less considered there are differences in the adhesion limit of each vehicle,so that it is difficult to effectively exert the problem of the available braking force of each vehicle.Based on the priority of electric braking control,an optimization control algorithm of air braking force distribution with the total maximum utilization ratio of adhesion as the objective function was proposed.Firstly,based on the basic theory of adhesion,the optimal distribution requirements were given,and the objective function of optimal allocation of air braking force was established.In order to improve the efficiency of allocation algorithm,allocation constraint conditions were introduced and transformed into quadratic programming solution according to the characteristics of objective function.The Matlab/Simulink software was used to simulate the distribution of air brake force under the two braking conditions of high-speed trains.The results show that compared with the traditional load allocation method,the optimal allocation strategy can make full use of the different adhesion restrictions of each trailer,and reduce the total braking force borne by the motor car,and effectively reduce the skidding phenomenon of the motor car in the braking process.Thus,the train braking stability can be improved.Aiming at the problem that the braking force is difficult to play effectively during the train braking process and the unknown disturbance controller is difficult to design,an optimal adhesion braking control algorithm in non-singular terminal sliding mode with parameter estimation and sliding mode observer was proposed in this paper.Firstly,based on the single-wheel force model,the train braking dynamics model with unknown viscous friction coefficient and disturbance was established.In order to deal with the inescapable unknowns in train braking operation,two sliding mode observers were designed to observe the unknowns,and the observed values were fed back to the design of the non-singular terminal sliding mode controller,so as to improve the robustness of the system.The effect of the sliding mode observer and controller designed in this paper was verified by Matlab/Simulink simulation platform.Simulation results show that the proposed control algorithm has good adaptability to the time-varying orbital conditions.Compared with the PI control method,it shows better superiority.