Research On Stiffness Modeling And Optimization Of Vehicle Fatigue Durability Test Platform

In this paper,the performance analysis and optimization of the vehicle fatigue and durability test platform based on high stiffness and excellent dynamic characteristics were carried out to meet the strategic needs of the development of high-end intelligent equipment in the field of vehicle fatigue and durability test,so as to achieve the accuracy requirements of road spectrum recurrence of the vehicle fatigue and durability test platform.The results can also provide theoretical guidance for the application of parallel mechanism in the field of high stiffness.The main research contents are as follows:In terms of the static stiffness of the vehicle fatigue durability test platform,the stiffness matrix of the branch was derived by using strain energy and Casserolli’s second theorem.The stiffness matrix and the binding force of each branch were derived by combining the deformation coordination equation of the ideal joint of the mechanism(driving stiffness,branch deformation and redundant driving).Based on the principle of virtual work,a stiffness modeling method of the overconstrained mechanism was proposed,which considered the joint clearance and joint contact deformation.The modeling error caused by the coupling binding force was solved by combining the probabilistic statistical model,and the stiffness variation interval was estimated approximately,and verified by the finite element method.The proposed method can comprehensively evaluate the influence of multiple factors on the static stiffness of overconstrained redundant mechanisms and establish a high precision static stiffness model.In terms of dynamic stiffness of vehicle fatigue durability test platform,the dynamic model of ideal joint was established by virtual work principle,then the vibration differential equation was derived to solve the natural frequency,and the output vibration response characteristics were analyzed by Newmark-β method.A method to identify the modal parameters of vehicle fatigue and durability test platform based on Adams virtual experiment simulation was proposed to illustrate the influence of flexible and clearance nonlinear factors on dynamic stiffness performance.Finally,the Isight optimization model is built,sample points are generated by the optimal Latin hypertropy method,and the approximate model is constructed by the response surface.A particle swarm multi-objective optimization algorithm based on the response surface fitting design of the optimal Latin hypertropy method is proposed,and the correlation matrix and effect diagram of the design variables and the objective function are drawn to reveal the internal relationship between them.The Pareto optimal solution set is obtained by multi-objective optimization of the mechanism.The overall mass of the mechanism is reduced by 31.08%,and the first-order natural frequency,static stiffness and working space of the mechanism are increased by 59.14%,12.64% and 41.67%,respectively,which provides a valuable reference for the performance improvement of the vehicle fatigue durability test platform.