Modeling Analysis And Parameter Design Of The Body Isolation System Of A Commercial Vehicle

When a vehicle is running, the frame can been excited via wheels, suspensions and shockabsorbers by road surface roughness. Meanwhile the engine vibration can also excite the frame via itsmounting system. The frame can perform rigid motion and elastic deformation under multi-excitations.Because of the body isolated on the frame, body and isolated rubber elements constitute a vibrationsystem with a complex basement excitation in high demand for the performance of the body isolationsystem. The analysis and design for the body isolation system of a commercial vehicle has been donein the paper.Firstly, based on multi-body dynamics theory, the body isolation system and vehicle model areestablished with ADAMS. The characteristics of the vehicle vibration system can mainly beenanalyzed with the model, which includes body, isolation systems, frame, suspension, shock absorbers,power train, axles, wheels and road. The mechanical parameters of body isolation system, three-linkspring stiffness, the significance of frame elasticity for accurate modeling are considered in modeling.Then, the frequency distribution of vehicle vibration system is studied when the stiffness of bodyisolation and suspension spring are changed. By studying and compring the frequency distributionwhen every single variable changes, body isolation stiffness has a greater impact on the frequencydistribution than the suspension system. Furthermore an objective function to evaluate the frequencydistribution is built and design of experiments is employed to study the influence of the four variableson the body first-order modal frequencies of six directions. The study shows that the front bodyisolation stiffness has a greater impact on the objective function than the others. Meanwhile a set ofmatching stiffness are selected and verified to study the significance of the vehicle frequencydistribution.Finally, the body isolation stiffness in three directions are optimized with design of experimentswhen root mean square of weighted acceleration at the body floor works as an objective functionbased on the vehicle ride comfort evaluation index. In the end, the structure of rubber isolator isredesigned according to the previous optimal stiffness.The research results, which are achieved in this thesis, possess certain value to serve as areference for the design of body isolation system.