Study On The Dynamics And Control Of High Speed Train Under Traction And Braking

China's economy has been developed rapidly since the new century. In order to solve the bottleneck problems caused by the railway passenger transportation, China has adopted the strategy of introducing digesting absorbing and re-innovating foreign advanced high-speed train technologies. This leads to the leap-forward development of China railways, and creates the highest commercial operating speed with 350km/h for the high speed trains in the world. With the speed increases, the dynamic characteristics of the train will change greatly in high-speed state compared to the low-speed, such as the wheel-rail interaction force, traction motor vibration, high-speed meshing vibration of gears, aerodynamics and so on. These will bring more uncertainties for the high speed trains on the running behaviour, effectiveness and safety of traction and braking. In traditional studies on the vehicle traction and braking dynamics in the erarly days, usually single wheelset model with two degrees of freedom was used and only traction and braking and their related dynamic effects in the longitudinal derection was considered. The model is relatively simple and is only suitable for the theoretic discussions. Later on, the dynamic model with considering the coupling between the carbody, bogie frames and wheelsets was established for evaluating the effectiveness and safety under traction and. braking and the influence of longitudinal vibrations on the vehicle dynamic performance. Although these dynamic studies took into account the effects of traction and braking on the vehicle dynamics, the analysis done for the vehicle system was not from a holistic point of view (single vehicle, whole train or mechatronic coupled system). It was still not enough. Therefore, this article will study the dynamics and control strategy of vehicle traction and braking systematically by considering the transmission system and the electromechanical coupling relations.The main works of this thesis are:(1) The equivalent mathematical models of the asynchronous traction motor and inverter are established, and the direct torque control technology which uses the circular and hexagonal flux combining method, is used to control the motor output torque.(2) The wheel/rail adhesion characteristics is analyzed, and the method for the estimation of wheel/rail adhesion coefficient is given. The equivalent simplified model of the transmission system based on the fast algorithm of Polach creep force law is established.. The influence of wheel/rail creepage on the transmission system vibration and the effect of the adhesion coefficient on the wheelset lognitudinal vibration are discussed.(3) The slope of stick-slip curve is predicted by using the recursive least squares method and the reference wheelset speed is estimated by using Kalman filter. Thus the optimal usage of adhesion coefficient for anti-idling in driving and anti-slip in braking is obtained.(4) The nonlinear model of brake cylinder based on Sanville flow formula is set up and the characteristics of cylinder pressure is analzed. The sliding mode and logic threshold control methods are adopted to control the asynchronous traction motor and brake cylinder. The wheel-slip prevention control under electric-pneumatic brake is simulated and the results obtained by the two control methods are compared.(5) The effect of rotor vibration of traction motor on dynamic behavior of the vehicle system is analyzed. The model of motor car including the transmission system is built and the non-linear force of rotor-bearing system is considered in the model. By using the numerical simulation, the effect of non-linear reaction force of rotor-bearing system on traction motor is studied. The dynamic performance of the motor car in the case of traction, constant moving and idling with or without considering the non-linear reaction force are analyzed and compared.(6) The vehicle dynamic performance with or without considering the transmission system is analyzed. The influence of bogie frame flexibility on the longitudinal dynamic performance of vehicle system is studied, and the effect of longitudinal damper between vehicles under the conditions of two kinds of marshalling on the longitudinal train dynamics is investigated.