Dynamics Analysis And Optimization Design Of Suspension System Considering Flexible Body

With the development of society and science, automobiles are need to be more and more better. The contradiction between the riding comfort and handling safety of automobiles becomes obvious in the case of the improvement of road surface and automobile's velocity. In the vehicle engineering, people are paying more and more attention to the riding comfort and the handling safety of the vehicle. The suspension system is one of important part in modern automobile which can insure that the wheels have elastic relation to the body and can transfer loads, abate impact, decrease vibration and adjust moving body. The suspension system is the key component to improve the riding comfort and the handling safety, and reduce the components' fatigue damage. The suspension system should not only isolate higher frequency roadway inputs, which influence the riding comfort, but also make the body and wheel closely follow the lower frequency vertical roadway inputs, which influence the handling safety.The vehicle suspension system is classified into the passive suspension system, semi-active suspension system and active suspension system. Currently, the popular suspension systems used in automobiles are passive suspensions consisted of a combination of elastic elements and absorbers. In this thesis, a mathematical model of Suspension system of half rigid-flexible vehicle under excitations of random road surface is mathematically modeled. The vehicle system is consisted of the seat subsystem, the sprung mass subsystem and the suspension subsystem, the unsprung mass subsystem. Frequency responses of the system are obtained used the substructure conductance method.Power spectrum matrices are obtained under the double excitation from multi-roughness road surface and then gets frequency response characteristics of the vibration system in frequency domain of the seat and the body's vertical acceleration and the wheel's force. And simulate the suspension system of half-flexible vehicle using Matlab. According to the analysis of the seat and the wheel force's response curves in the case of the vehicle system excited by the road stochastic excitation, we can conclude that the seat vibration and the destruction to road increase along the autocar's velocity. The road surface should be improved to improve the riding comfort.On the above-mentioned study results bases, a mathematical model, which adopts the first three modes' acceleration power spectrum density of the prototype's seat as objective function, and takes the three aspects of performance associated with suspension parameters as constraint, is found for analyzing the optimization of suspension parameters. The calculating program combined with stochastic direction exploring method is used to search for the optimum solution and finally we got a better result. The simulation results show that the optimization results can improve the comfortable performance of the prototype. The results will give a basis for free design of shock absorber and vehicle ride dynamics system and lay solid foundation for investigation of suspension controlling and ground characteristic of passive hanging damage systematically.