Study On Active Control And Bifurcation Characteristics Of Hunting Motion For High-speed Railway Vehicle

Chinese high-speed EMUs have significant characteristics,including high operation speed,wide operation area,and extensive line number.The long-term dynamic performance of high-speed trains directly affects the operation safety,operation efficiency,and operation and maintenance cost of high-speed railways.The continuous high-speed operation of the train will accelerate the evolution of wheel wear and wheel/rail relationship,and the wheel/rail interaction would experience a sudden change during cross line operation caused by the discreteness of rail profile,which will exceed the adaptive range of suspension parameters.The different lines’ track irregularity and rail profile dispersion lead to significant dynamic performance differences.Low-temperature ice and snow environment will affect the wheel/rail contact interface’s state and cause dynamic suspension parameters and track stiffness changes.Under the influence of the above factors,the high-speed train’s line operation adaptability becomes more prominent,resulting in an insufficient hunting motion stability margin.It is necessary to deeply study the evolution law of dynamic behavior,deterioration mechanism,and regulation methods.However,the conventional passive suspension can hardly balance different dynamic performance requirements and can not adapt to the harsh operation boundary conditions.At present,it can only be alleviated by frequent wheel reprofiling,rail grinding,and suspension element replacement,which significantly affects the operation efficiency,shortens the service life of wheel and rail and increases the operation and maintenance cost.In the future,the train running speed will be further improved(≥ 400 km/h),and these problems will be more prominent.Therefore,active suspension technology is the future development trend,significantly improving the wide-area adaptability,driving safety,and operation and maintenance economy.At present,there is still a need to investigate the active control of hunting motion stability of high-speed vehicles under the condition of the dynamic evolution of the wheel/rail relationship.The research theory of active control of hunting motion needs to be improved,and investigation on active control concerning primary hunting and secondary hunting is scarce.It is necessary to break through the existing dynamic performance optimization design method based on passive suspension parameters and put forward the hunting stability control method suitable for higher speed levels and extreme wheel/rail matching conditions.This has important engineering application value for ensuring the longterm dynamic performance,speed improvement,and operation and maintenance economy of high-speed EMUs in China.It can also vigorously promote the development of the research field of railway vehicle dynamics and control.Therefore,the main research work of this thesis is as follows:(1)A constraint wheelset model and a simplified lateral-intended dynamic vehicle model are established with the nonlinear geometry of wheel/rail interaction considered,and an improvement is made to the polynomial flange force expression.The dynamics and active control simulation platform for high-speed vehicles include the electro-hydraulic actuator model,control algorithm,and the three-dimensional dynamic model of the whole vehicle.(2)The evolution process of wheel/rail contact geometry parameters against the accumulated mileage is studied using the measured wheel profile of high-speed EMUs.The wheel/rail contact geometry parameters include rolling radius,contact angle,and curvature radius.The influence of the wheel/rail contact geometry parameters on Hopf and LPC bifurcation of the constraint wheelset is investigated.Furtherly,the influence of linear and linear control law gains on Hopf/LPC bifurcation,the magnitude,and the period of limit circles are discussed.(3)The bifurcation diagrams of carbody hunting and bogie hunting are obtained using the simplified lateral dynamic vehicle model.The effects of wheel/rail geometry contact parameters and suspension parameters on Hopf bifurcation characteristics are invesigated.The vehicle bifurcation behavior under active control of anti-yaw dampers is studied,and the BP bifurcation under the active control of displacement feedback is observed.A uniform expression of control method is built,including the skyhook damping/stiffness,groundhook damping/stiffness,blended control,model control,etc.The influences of the active control method and gains on the stability of equilibrium are revealed through the indirect Lyapunov method and double-parameter Hopf bifurcation analysis.The control method based on displacement and velocity feedback is proposed for primary and secondary hunting stability improvement.(4)Based on the electromechanical coupling dynamics and control 3D model of the vehicle system,the effectiveness of the proposed control strategies is verified in both carbody hunting and bogie hunting cases through simulation.Its adaptability to speed,curved tracks,and equivalent conicity are also discussed.The adaptive adjustment criterion and control logic of hunting stability are proposed based on hunting instability state identification,and the vehicle dynamic performance after active control is simulated.