Simulating Research On Small Hunting Of High-speed Train Based On SIMPACK

With the vigorous development of China’s high-speed railway,the increasing density of track and traffic flow,and the increasing speed of vehicles,the stability of train operation caused by the structure of vehicles and the excitation of track lines is increasing and threatening the safety of train operation at any time.Therefore,while the train continues to speed up,we also need to pay more attention to the safety of the operation of vehicles,and explore the factors affecting the stability of the train operation,in order to ensure the highspeed and safe operation of the train.The stability of hunting is an important factor affecting the safe operation of high-speed trains.Hunting not only limits the running speed of rail vehicles,but also damages track lines,which may lead to derailment in serious cases.The existing hunting detection standard is that when the lateral acceleration of the frame reaches a larger threshold,the alarm of hunting instability will occur.The small hunting instability can not respond to the small hunting instability when the standard threshold is not reached.Although the standard hunting instability is not reached at this time,the small hunting instability will affect ride comfort,aggravate wheel-rail wear,and may become standard hunting instability at any time.Real-time monitoring of small hunting movement and studying what factors influence small hunting movement to evolve into standard Hunting Movement instability can early warn standard Hunting Movement instability and avoid the risk of train derailment.Mass scholars have done relevant research on the real-time monitoring of small hunting.The purpose of this paper is to study the influence of external factors on the evolution of small hunting motion of high-speed train into standard hunting motion instability from the aspect of vehicle system dynamics.The main research contents are as follows:(1)According to the structure of a high-speed electric car bogie and the detailed parameters of the vehicle in China,the vehicle dynamics simulation model is established in the multi-body system dynamics software SIMPACK,and the wheel-rail contact nonlinearity and suspension system nonlinearity in the vehicle system are in software.Corresponding processing has been done to ensure the integrity of the system to the utmost extent.In addition to the vehicle system dynamics model,a track random irregular disturbance model is established to simulate the state of the actual track circuit.The experimental data and simulation data were used for comparative analysis to verify the accuracy and completeness of the model.(2)The influence of the initial conditions of small hunting motion on the nonlinear system of the vehicle is preliminarily studied.Firstly,the initial amplitude of the small hunting is characterized by the initial wheel-to-transverse amount,and the initial condition of the small hunting is set for the system.Then the vehicle dynamics simulation model and the orbit random disturbance model are used for simulation calculation.The relationship between the initial amplitude of the small hunting line and the critical speed of the snake’s line is analyzed by the calculation of the system’s limit cycle amplitude under the initial condition of the small hunting.The simulation experiment shows that the critical speed of the hunting is unstable when the initial amplitude of the small hunting does not exceed 2mm.The critical speed of hunting instability of the system is basically the same.At this time,the change of initial condition of the small hunting has little effect on the vehicle system.When the initial amplitude of the small hunting is 3-9mm,the critical speed of the hunting instability is decreasing with the increase of the amplitude.Both are high the nonlinear critical speed of the system.Through the calculation of the wheel-to-transverse displacement under small initial conditions,the variation process of the convergence and divergence of small hunting motion is analyzed.The simulation experiment shows that the initial amplitude of the small hunting will affect its own convergence or divergence speed,ie amplitude.The larger,the slower the convergence or the faster divergence.(3)The influence of the orbital geometry on the vehicle system under the initial conditions of small hunting motion of high-speed trains is studied.The random irregularity model of the orbit is established.The geometric irregularity in the model has four kinds of irregularities: direction,level,height,and gauge.These four kinds of track irregularities are applied to the track line respectively,and four types are set.The working conditions are simulated.The influence of the orbital geometry on the critical speed of the system’s hunting instability is analyzed by the calculation of the system’s limit cycle amplitude under different orbital excitation conditions.The simulation results show that the track geometry irregularity will affect the critical speed of the system’s hunting instability under small initial conditions.The critical speed of the hunting movement is higher than the nonlinear critical speed of the vehicle;in the four track irregularities,the direction irregularity has the greatest influence on the critical speed of the hunting instability,and the influence of the unevenness is the least.