Suspension Characteristic Analysis And Optimization Based On The Rigid-flexiblecoupling Model Of Vehicle

The suspension system is a critical important part in chassis. In the research and design processes of modern vichle chassis, rubber bushings have been widely used in each connections of chassis. Its main purpose is that applying the vibration isolation and noise reduction performance to reduce the vibration and impact of body, caused by the road excitation, especially improving the transfer characteristics and NVH(noise、vibaration、harshness) performances of automobile effectively in the middle-high frequency vibration range. In this paper, a rigid-flexible coupling model is established by the ADAMS software. With the four post riding smoothness test the accuracy of model is verified in low frequency(below 20 Hz) excitations, and rubber bushing stiffness is optimized in middle-high frequency(20 to 100 Hz) eventually.This article expounds the multi-body system dynamics firstly. The module of ADAMS/Car is used in the processes of full vehicle modeling according to the parameters of a car. In order to conform to the real driving situation, modal analysis has been applied in this process, then flexible structures have replaced the front sub-frame and the rear torsion beam so as to establish the rigid-flexible coupling model of the vehicle.After the full vehicle modeling, the accuracy of the model is necessary. This paper mainly focus on the verification of the four-post ride comfort test in a low frequency(below 20 Hz). To make the simulation results closer to the true value, there is corresponding verification by adjusting the rubber bushing stiffness, shock absorber damping, spring stiffness parameters. This paper following analyzes the suspension vibration transfer characteristics in the middle-high frequency(20 to 100 hz) excitation.Through adopting the ADAMS/Insight module, the author optimizes all the key rubber bushings in chassis to improve the transfer characteristics. Then taking the vertical acceleration root mean square(RMS) of front-left damper and body connection point as the optimization abjective, and taking the bushing stiffness which make more difference to the suspension performanes as the optimization variables, choosing the optimization algorithm appropriately. The simulation results indicates that the vibration transfer characteristics of the suspension has been improved in the middle-high frequency spectrum.In addition, to recerive the bushing stiffness and damping characteristics, this thesis divides the rubber bushings into three categories on the basis of the different bushing features, such as normal bushings, abnormal bushings and engine mounts. It is meaningful for engineering application in a way through summarizing briefly the fixture design processes and rubber bushings stiffness test methods.