| Being an important component of the high-speed EMU unsprung unit, the drive system includes some significant elements, like the motor and the gearbox, between which the elastic coupling is usually adopted. The previous research on the vehicle system dynamics tends to utilize a constant speed, without attaching importance to the influence of the drive system. In fact, based on the most fundamental relation of the vehicle system—the wheel-rail nonlinearity, which embodies the nonlinearity of the wheel-rail contact geometry and of the wheel-rail power, the vehicle system is a very complex nonlinear system. Also, a number of the elastic units in the drive system may pose an impact to the stability of the whole system. Traditionally, studies relating to the drive system were primarily based on simulation and a simplified drive system model, instead of unifying the drive system and the vehicle system.The wheel-rail contact theory, one basic theory of the vehicle system dynamics, has been widely applied to various scientific studies and engineering practice. However, in a large creep working condition, there is a phenomenon that the creep force decreases as the creep rate increases, which cannot be clearly explained by the existing wheel-rail contact theory. Based on the current theory, this thesis aims to modify the simplification theory procedure FASTSIM, making it suitable for the calculation of the wheel-rail force in such working condition with large creep.The stick-slip vibration between wheel and rail, such as rail corrugation, wheel wear, and the zing made when the vehicle passes a small radius curve, can have a significant effect on the vehicle engineering field. Thereby, here are the questions to be answered. That is, how is on earth the wheel-rail stick-slip vibration produced and what are those factors? In addition, how can we reasonably optimize and design the parameters to suppress the wheel-rail stick-slip vibration? This current study attempts to answer the above questions from the perspective of the coupling dynamics unifying the drive and the vehicle systems, and presents the matching results of the optimized parameters.This thesis involves four main aspects of work.(1) A couple of theories have been introduced to modify Kalker’s simplification theory procedure FASTSIM, and to make it applicable for the calculation and simulation of the wheel-rail force in a large creep working condition.(2) A detailed model of the drive system dynamics has been established. Through the linearization of the wheel-rail contact nonlinear factors—creep rate and adhesion coefficient, a linearized model is obtained. Then by analyzing the eigenvalues of this model, an initial judgment can be made about the effects of the parameters on the system stability.(3) The coupling dynamics model with a total of 24 degrees of freedom has been established, which contains 8 degrees of freedom from the drive system, and 16 from the nonlinear wheel-rail contact relationship, the nonlinear wheel-rail power wheelsets as well as the single frame. Meanwhile, a comparison has been made between the simulation results of MATLAB and SIMPACK, verifying the correctness of the dynamic model mentioned above.(4) According to the new model, the effects, in two working conditions—the constant torque and constant power traction, which the correlation parameters of the drive system perform on the wheel-rail stick-slip vibration, are analyzed. What’s more, the research reveals the resonance between the drive system and the wheel longitudinal movement, together with the bifurcation of the drive system.(5)Besides, the stability of comprehensive wheelset nod and longitudinal movem ent results in a parameter matching figure with a series of longitudinal rigidity and ge arbox hanging vertical stiffness. |
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