The Matching Research Between Tire Nonuniformities And The Dynamic Characteristics Of The Chassis

As a multi-degree-of-freedom vibration system, vehicle is composed of multiple subsystems with natural vibration properties. There are many factors to consider when analyzing the abnormal vibration problems, and it is complicated to solve. Tire nonuniformities, because of its wide range of excitation frequencies, results in abnormal vibration of the vehicle. Taking the coach as the research object, the impacts of all exciting sources on the vehicle vibration are analyzed. According to the reason for the abnormal vibration, specific matching scheme is proposed, which lays a foundation for the improvement of vehicle quality.Based on investigation on analysis and solution of abnormal vibration at home and abroad and the vibration mechanism of various excitation source, the basic idea of this paper is determined. First of all, the modal frequencies and modes obtained from the modal analysis in the module of OptiStruct are compared with the experimental data, thus confirming the accuracy of the finite element model of the frame which is established in the first step. Secondly, time domain and frequency domain analysis are carried out for response signals from all the measuring points which are arranged in the road test. The frequencies, corresponding to the maximum acceleration peak values of auto power spectrum at the speed when the coach has intense vibration, are compared with the vehicle excitation frequencies and inherent frequencies of all the components, which shows the reasons of the vibration. Finally, the direction of frame optimization is determined according to the principles of modal matching. The research model of the frame is built to investigate the relations between the structure of the frame and the modal frequency. Integrate all the results together and draw the conclusion that structure characteristic determines the modal frequency most. Upon the analysis results, optimization is done on the frame. The inherent frequencies of the improved design for the frame is far from the excitation frequencies of the tire and the engine at idle speed. The results show that the ride comfort of the coach is greatly improved.