Research On Dynamics Of Flexible Car Body And Semi-active Control Of Suspension System Of High Speed Railway Vehicle

High speed and lightweight have become the main direction of the development of high-speed trains in China, which is of advantages such as shortening the running time, making more economic benefits and saving resources. But high speed leads to the increase of the vibration frequency of the vehicle, and the light weight not only causes the decrease of the stiffness of the vehicle structure, but also leads to the obvious structural deformation, the decrease of the natural frequency, and the increase of the elastic vibration and resonate with the high frequency induced by the high speed. At the same time, the effect of elastic deformation on the dynamic performance of the vehicle system can't be ignored, especially the impact on the vehicle body made by hollow light aluminum alloy material. Therefore, if the flexibility of the vehicle body is taken into account, it should be more reasonable to reveal the dynamic characteristics of the vehicle and avoid resonance.In this dissertation, two kinds of models are compared and analyzed by establishing the multi rigid body model and the rigid flexible coupling model, and the dynamic characteristics of the flexible body are obtained. And the continuous semi-active control system is set up with the horizontal and vertical vibration damper of the suspension system of the two series vehicle in order to optimize the horizontal and vertical vibration of the vehicle. The detailed discussion is as follows:Firstly, multi rigid body model of a certain type of vehicle is established. Vehicle is considered as a multi rigid body with 31 freedom degrees. Vehicle operation is simulated and calculated in the linear orbit and the curve orbit with the German low interference spectrum as the excitation. On linear track the acceleration characteristics of lateral and vertical vibration of vehicle mainly including the vehicle running stability sperling index, the acceleration mean square value RMS index and the maximum acceleration amplitude is analyzed. Running stability index of vehicle body is obtained under the speed of 350km/h, 300km/h, 250km/h and 200km/h. And the vehicle curve passing ability, safety characteristics, and vehicle derailment coefficient under different circle curve radius are also obtained.Secondly, the rigid flexible coupling model is established. At first, the 3D model of the vehicle body is established under the consideration of the body boxes as thin-walled beam structure with the three-dimensional entity for FE, then, the material attributes are defined and the coupling points are created, and in the next, the body free mode and the sub structure are calculated and analyzed, and the data are outputed into the file(*.FBI) for corresponding input, finally the rigid flexible coupling dynamics model is set up. Comparison of the dynamic characteristics of two models, the results show that the rigid flexible coupling model of the vertical and horizontal vibration are greater than the multi rigid body model, and on straight track elastic vibration of flexible car body under the specific frequency influences running stability obviously and worsens ride comfort, and in the curve track it also has a certain influence on the running safety of the vehicle. In order to improve the ride comfort and the safety of the vehicle, a continuous semi active control system is established for vehicle dynamics performance optimization.Finally, Continuous semi active control of flexible body is done as following steps.(1) A fuzzy logic controller is established in MATLAB/SIMULINK.(2) Vibration velocity at the position of the front and rear shock absorber of vehicle body and the relative speed between the vehicle body and the frame at the corresponding position are considered as the control quantity. Damping of controller output is considered as the output. The relative velocity of the vehicle body and the frame is used as a multiplication operation and the result is used as the vertical and horizontal damping force of the two series suspension.(3) The lateral and vertical vibrations of the vehicle body are controlled in the rigid flexible coupling model. The results of semi-active control and passive control are compared, which shows that the former has obvious improvement.