Research On Driving System Dynamics For High Speed Motor Car With Bogie Frame-suspended Motors

Traction motor is a power component of high-speed trains,its suspension mode and suspension parameter determine the distribution of the unsprung and the interspring masses,which will change the vibration isolation performance of motors under track irregularity excitations,and then affect the lateral stability of the bogie.The drive system including the traction motoris a multi-degree-of-freedom system,and its torsional vibration is a self-excited vibration,which is an important vibration form of vehicle vibration.When the adhesion coefficient between wheel and rail of high-speed trains decreases,the wheel may be idling and the drive system may have torsional self-excited vibration.When traction motors are mounted on bogie frame,in order to adapt to the relative motion of motor and wheelset,the structure of drive system needs elastic connection,thus the torsional vibration stability of drive system is worse than the case that when traction motors are mounted on wheel-axles.When the internal structural parameters of the drive system are not properly selected or when the mechanical and electrical control systems are not matched well,the torsional vibration instability of the drive system will easily appears,which will not only reduce the reliability and service life of the driving parts,but also affect the ride comfort and safety of the vehicle.It will also produce periodic wear and abrasion on the wheels and rails.When asynchronous traction motors on the high speed trains work,since the output voltage and current from inverters contain harmonics,there are pulses in electromagnetic torque,and finally produce the action force on the vehicle system,which will further affect the dynamic performance of the whole vehicle.In this paper,a high speed train with bogie frame-suspended motors is taken as the research object,and the dynamics of its drive system are intensively studied.The detailed research works are as below:(1)A simple lateral vibration model with three rigid bodies has been built according to the elastic frame-suspended mode for high-speed motor cars in China.The influence of the motor suspension parameters on the natural frequency of the vibration isolation system is discussed,and the dynamic responses of the vibration isolation system under harmonic and random excitations are analyzed.(2)The lateral motor bogie model with 8 DOF is established,and the bifurcation diagrams of bogie hunting motion with different motor suspension parameters are obtained by using the continuation algorithm.The linear and nonlinear critical speeds are determined,and the influence of motor suspension parameters on the critical speeds is studied,then the root locus method and Hopf bifurcation normal form theory are used to explain the influence law.(3)A simplified torsional vibration model of drive system with 3 DOF is established,in which the elasticity of wheelset is considered.In addition to the same wheel-rail adhesion condition for the two wheels,the vibration behaviour under different adhesion conditions for the two wheels are also discussed,which is explained from the point of view of energy.The nonlinear system is linearized at the origin(equilibrium position),and the influences of key parameters on the stability of the linearized system are analyzed.(4)A dynamic equation of a 7 DOF drive system is established,the influence of motor output shaft stiffness on adhesion performance is studied,the nonlinear torsional system is linearized,and the influence of the suspension parameters of coupling and gearbox on the stability of relative torsional vibration under the hollow shaft and solid shaft of the motor is studied.(5)The effects of the length of motor Hanging Beams,the coupling parameters(torsional stiffness,damping)and the gearbox hanging parameters(stiffness,damping)on the dynamic performance of the motor vehicle are studied.(6)The fundamental torque and the first four harmonic torques of the motor for a high speed train are calculated,and the results of which are added to the motor driving torque of the multi-body system dynamics model.Not only the influences of harmonic torque on the dynamic performance of high-speed trains are analyzed,but also the influences of harmonic torque on the vibration of gearbox and motor are studied.