Research On Traction Flutter Of A Bogie With A Linear Motor

With the development of the urbanization, the urban traffic plays a more and more important role in the urbanization development process. Since the urban transportation is closely linked to people’s works and lives, it is particularly important to develop an efficient, rapid urban transport system. Urban Rail Transit (Rail Transit) has many good advantages such as a large transportation volume, high speed, security, punctuality, environmental protection, energy conservation and saving land. Nowadays, it is widely recognized all over the world that the fundamental way to solve the traffic problems of the city is to give a priority to the development of rail transit as the backbone of urban public transportation system. Since the linear metro structure is simple, durable, low center of gravity of the body, less maintenance, good adaptability to small radius curves and large ramps, easily track line planning and flexible design, it has been applied widely in the field of city rail transits.When a vehicle using a linear motor as a driving unit runs, the stator of the linear motor is found to undergo a serious flutter. The flutter of the stator may not only change the air gap to cause a damage of the electric loop of the stator, but also aggravate failure of the rods of the stator and make noise. A more serious problem is that the flutter has a great impact on the safety of the vehicle structure. Therefore, researching linear motor flutter is of great significance.Referencing to the vehicle structure with linear motors used in Guangzhou Metro Line4, a finite element model of the stator system of the linear motor has been established. Modal analyses and dynamic transient analyses are performed using this model. The following conclusions can be drawn:(1)The modal analysis results show that one of the natural frequencies of the stator system of the linear motor is about57.7Hz, whose vibration mode corresponds to a local vibration of the sator system. Therefore, the linear motor has a tend to flutter when the linear motor is applied by an external excitation.(2)The negative slope of traction curve of the linear motor has a major impact on flutter of the linear motor. Based on the modal analysis, we know that the linear motor has a low natural frequency. When the absolute value of the negative slope of traction curve is enough to large, it becomes an excitation source to the linear motor. Under some cinditions, the negative slope of traction curve of the linear motor can cause a self-excited vibration of the stator system.(3) The constraints of the upper ends of the vertical rods of the linear motor have an important influence on the chatter of the linear motor. When the upper ends of the vertical rods are fully constrained with the frame of bogies as a whole, the flutter of the linear motor may be suppressed largely.(4) In this thesis, the flutter results measured in Guangzhou Metro Line4are compared with the simulation results. The conclusion has proven the feasibility of using the ABAQUS finite element software in the flutter analysis of the linear motor once again.