Nonlinear Dynamics Of Locomotive Traction Motor With Rub-Impact

As the dynamic system of locomotive, drive system is a complex flexible transmission system consisting of traction motor, gear box and a driving mechanism. Due to being arranged in the bottom of the locomotive, working in poor condition and undergoing strong impact from the rail while supplying power, the drive system has an important influence on dynamic performance of the train. The traction motor is the core component of train driving system, and rotor rub-impact is not only a common fault, but also the main reason causing instability of the system. With increasing speed of the locomotive, deteriorating working condition and aggravating vibration, higher requirement on the speed and stability of traction motor has been put forward.Research on the motor rotor rub-impact is of significance to ensure the train operation safety and reliability. The nonlinear dynamical behavior in rub-impact of rotor is studied to analyze the rotor system of train traction.First of all, rub-impact conditions of normal Jeffcott model of rotor system is deduced and a local rub-impact rotor dynamics model with nonlinear stiffness is established considering the linear and nonlinear stiffness of the shaft material.Secondly, MATLAB and VC are combined to build a co-simulation platform.A graphical user interface is designed by MTALAB, while the algorithm is programmed by VC and then compiled into MEX files to be called by MATLAB. Hence, the platform is verified through Vanderpol equation.Finally, Four-order Runge Kutta Fehlberg method is adopted to solve differential equation of the rotor system and the rub-impact simulation is implemented under the platform. Taking the frequency ratio and damping ratio as the bifurcation parameter, the paper studies the steady-state response under the specific rotor eccentricity, discovers the existence of periodic solutions, quasi periodic solutions and chaotic motion from the bifurcation diagram, and makes further verification by a series of dynamic characteristic curves.The results show that the response undergoes frequency alternating vibration and chaotic motion through the cycle of K along with changes of the frequency ratio, when the rotor rub-impact occurs. In the periodic and quasi periodic motion cycle, the 1 and 1.5 frequency spectrums can be used as the basis to identify rub-impact fault.Response experiences the process from quasi periodic to periodic motion with damping ratio changing. With the increase of damping, rotor response has not experienced chaos, but directly evolved into single cycle motion.Therefore, heightening the damping can enhance the stability of the periodic motion of the locomotive rotor system to avoid chaos.