A Method For Calculating Dynamic Load Of Components Of Independent Suspension System

During the running of the vehicle,the components of suspension system bear and transmit a variety of dynamic loads from tire and body,which are indispensable boundary conditions for the structural strength and fatigue analysis of suspension system,as well as important parameters to guide the optimization of suspension and body structure.In this thesis,a method for calculating dynamic load of components of the independent suspension system based on the multi-body dynamics theory and the constraint treatment method of the Udwadia-Kalaba equation and its application are studied by taking the six-component force of wheel center as the input.The specific contents of this thesis are as follows:Firstly,taking the front double wishbone and rear five-link suspension system without bushing connection as the research objects,the dynamic model without constraint,the constraint equation and the complete dynamic models of front and rear suspension system are established respectively based on the basic idea of the Udwadia-Kalaba equation.The decomposition process of the total binding force of the system is deduced and the analytical expression of the load on each component is obtained.The above models are built in MATLAB and the simulation results are compared with those obtained by ADAMS/Car,which verify the correctness of the above-mentioned methods.Then,considering the connection mode of rubber bushing,a mathematical model is established to characterize the dynamic characteristics of the bushing.Aiming at the difference of the distribution positions of bushing and the similarities and differences of the modeling method of the front and rear suspension without bushing,the dynamic modeling and the calculation process of hard point load of the front and rear suspension are derived respectively.Similarly,the simulation results obtained by MATLAB and ADAMS/Car verify the correctness of the above-mentioned methods.Furthermore,the six-component force test of a SUV is carried out to collect the force signals under two road conditions,taking the force signals as inputs and combining with the suspension model built above,the dynamic loads of the front suspension control arm are predicted.Then the fatigue lives of the control arm under two conditions are analyzed by using the predicted loads as the boundary conditions.Finally,in order to facilitate the use of the above methods,the modeling and calculation process of other independent suspensions,such as McPherson,four-link suspension system are built respectively,and a simulation platform for modeling and load calculation of independent suspension system is designed in MATLAB/GUI,which realizes the parametric modeling of various independent suspension system.In this thesis,the Udwadia-Kalaba equation is applied to the research field of independent suspension,and combined with the multi-body dynamics theory,the dynamic modeling and the calculation process of dynamic load of components of independent suspension are derived in detail.The combination of theory and practice in the process of research can provide a new idea for modeling and calculation of this kind of complex mechanical system with constraints.