Finite Time Tracking Control For Nonlinear System Of High-speed Train

The healthy and sustainable development of high-speed railways is an important foundation for the implementation of Chinese “One Belt One Road ” and “Going Global” national strategies,and it is also the core force driving the rapid development of Chinese economy.The safe operation of trains is the fundamental premise for the construction and development of high-speed railways.One of the key points to ensure the safe and reliable operation of high-speed trains(HST)is whether the automatic train operation(ATO)system can generate reliable traction/braking control signals in time.That is,a reliable traction/braking control method needs to be established for ATO system.Nowadays,although some scholars have established many control methods for HST to achieve stable tracking control with considering the nonlinear and uncertain characteristics of HST,most of the research results focus on the steady-state performance of the system,which means the velocity and position tracking control system of HST is Lyapunov asymptotically stable,while the transient performance of the system is rarely studied.As a matter of fact,the ATO system of HST,which is concerning the safety of life and property,is a real-time control system that requires rapid response.The Lyapunov asymptotical stability often fails to achieve the desired control effect,and even the phenomenon(excessive overshoot and slow response)that affect the safety of train operation will occur with various disturbances and uncertainties.Therefore,considering the steady-state performance and transient performance of the system,the finite-time tracking control system for HST is constructed based on the finite-time control and fractional order control theory in this paper,which can enable HST to achieve high-precision tracking control in finite time,and further to ensure driving safety and accurate parking.The specific research is as follows:1.Considering the time-varying system parameters,the uncertain aerodynamic resistance,unknown in-train force,unexpected actuator failures,internal or external interference and the input nonlinearity caused by the different notches of tracking/braking forces in the operation of HST,in according with the Newton's law,the geometric relationship between the adjacent vehicle and the principle of "action force and reaction force",an improved multi-point-mass and single-coordinate model of HST is established based on the existing model.This model not only clearly describes the multi-point-mass characteristics and the influence of in-train force,but also has the advantages of low model dimensions and simple structure.2.Based on the dynamics model of HST and finite-time control theory,the control method that can improve the transient performance of the system is studied.An integerorder finite-time controller(IO-FTC)that can ensure the stable tracking control of HST in finite time is designed.3.Based on the theory of fractional order control theory and the design ideas of IOFTC,the thesis designs a fractional-order finite time controller(FO-FTC)to achieve higher precision tracking control of HST in finite time.Furthermore,from a theoretical point of view,the superiority of the fractional-order finite-time controller is proved.4.The two controllers designed in the thesis can compensate for actuator failure and system uncertainties in real time and effectively,and achieve the finite time tracking control of HST with active prevention before failure;Both controllers are independent of the model,only need to know the velocity/position of the reference vehicle,which is easy to apply and low cost;Additionally,the stability time can be adjusted to a certain extent by different choices of parameters.The simulation results shows that the settling time of IO-FTC,FO-FTC and PID is 0.6s,0.55 s and 2.5s in turn.Therefore,both theoretical analysis and simulation studies have verified the effectiveness and superiority of the designed controllers.