Analysis Of Hunting Stability And Research On Semi-Active Control Of High-Speed Trains

High-speed trains in China have the characteristics of fast running speed,long mileage,and complex routes,which once again pose a huge challenge to the hunting stability of trains.A series of problems including carbody shaking and frame alarms caused by hunting instability have appeared one after another,becoming one of the primary problems affecting the safety of train operation and riding comfort.Hunting stability determines the maximum allowable operating speed of rail vehicles and is an important factor affecting the safe and stable operation of vehicles.Therefore,in-depth research on hunting stability of high-speed trains and exploration of suspension control methods to meet the requirements of excellent vehicle dynamics performance on suspension parameters under complex operating conditions have important theoretical significance and engineering application value for continuous speed increase and safe and stable operation of high-speed trains.Taking "mechanism analysis-suspension control" as the main line of research,this thesis has carried out comprehensive and in-depth research work around the hunting stability of high-speed trains and the application of lateral semi-active control by combining theoretical derivation,numerical simulation,and experimental research.The details are as follows(1)The nonlinear system dynamics model of the wheelset was established,and the hunting stability,Hopf bifurcation characteristics,and evolution mechanism of the wheelset system were investigated.The center manifold theorem and canonical method were used to simplify the equation of the wheelset system.The first Lyapunov coefficient expression of the wheelset system was theoretically derived,and the Hopf bifurcation type of the wheelset system can be determined based on its symbol.The influence of different parameters on the critical speed of Hopf bifurcation in wheelset systems was discussed,and the distribution patterns of supercritical and subcritical Hopf bifurcation domains in the two-dimensional parameter space of wheelset systems were explored.The correctness of the distribution patterns of Hopf bifurcation domains was verified using simulation results.(2)A nonlinear stochastic dynamic model of a wheelset system with gyroscopic effect was established based on the stochastic excitation of equivalent conicity and suspension stiffness,and the stochastic stability and stochastic Hopf bifurcation characteristics of the wheelset system were investigated.The stochastic average method was used to transform the stochastic differential equation of the wheelset into a one-dimensional energy diffusion process.The stochastic instability condition and critical speed of the wheelset system were determined by judging the behavior of the singular boundary.The stationary probability density function of the wheelset stochastic system was derived theoretically,and the evolution law of the topological structure of the probability density function was analyzed.Explored the influence of stochastic factors on the critical speed of instability and Hopf bifurcation domain,and verified the correctness of the theoretical analysis method through numerical simulation.(3)The industrial rubber refining method prepared a new type of magnetic sensitive material,magnetorheological elastomers,suitable for semi-active suspension control of high-speed trains.The effects of strain amplitude,excitation frequency,and magnetic field strength on the dynamic viscoelasticity of magnetorheological elastomer were tested and analyzed.The viscoelastic fractional derivative was introduced,and a modified Bouc-Wen model based on fractional derivative was proposed to describe hysteresis characteristics of magnetorheological elastomers.The fractional derivative part of the modified model was approximately calculated by using the Oustaloup filter algorithm,a method of parameter identification under multi-loading conditions was proposed,and the parameters of the modified model were identified.The effectiveness of the modified Bouc-Wen model was verified by selecting test data of different conditions.(4)By analyzing the energy distribution characteristics of the carbody and frame in different frequency bands under three typical motion states,a high-speed train hunting stability monitoring index was proposed,and the threshold of the online monitoring index for hunting instability operation state was investigated.The influence of suspension parameters on vehicle dynamics response in an unstable state was discussed,and the control parameters to effectively restrain hunting instability were obtained.Combined with the hunting stability monitoring index,a semi-active control strategy to restrain the hunting instability of high-speed trains was designed.A joint simulation model for the semi-active suspension control system of high-speed trains was established,and the control effects of the semi-active control strategy under primary and secondary hunting instability were analyzed through simulation.(5)A modified extended hyperbolic tangent model for magnetorheological dampers(MRD)was established by introducing a correction function with current saturation characteristics.A new mixed semi-active control strategy was proposed to improve the running stability of the train,and the vibration transmission characteristics of different control strategies in the frequency domain were analyzed.Furthermore,the control advantages of the new mixed control strategy in the full frequency domain were explained from the perspective of phase frequency characteristics.The modified MRD model was applied to the suspension control,and the joint simulation model of the vehicle magnetorheological semi-active suspension control system was established using UM and Simulink software to analyze the influence of different control strategies on the vehicle’s dynamic performance.A hardware-in-the-loop experimental table of the vehicle suspension system based on MRD was constructed,and the carbody response under different control strategies was analyzed through the hardware-in-the-loop experimental.