Study On Integrated Optimization Of Vehicle Suspension Hard-points And Bushing Stiffness

As the key component of vehicle chassis system, suspension system directly affects the vehicle handling and stability because of its K&C characteristics. In a great extent, hard-point coordinates and bushing stiffness determine suspension K&C properties, so it is the key to chassis development work to design and optimize them to make sure the suspension with reasonable K&C characteristics which are good for vehicle’s handling and stability.Taking an advantage of a homemade car research and development project, to target this model, a sino-foreign joint venture high-end car was selected as the standard vehicle. Both of the target and the standard car had a double wishbone matched by a five-link rear suspension. According to the actual project, the elements and test methods of suspension K&C characteristics analysis were proposed. With the dual-shaft suspension K&C characteristics test bench, the suspension K&C performance test result data of the front and rear suspension were got. With the theory of multi-body dynamics, something as structural analysis, rationality assumptions, movement geometric analysis, established the motion equation and the dynamics model for the target vehicle suspension were done. Through dynamics simulations, the target vehicle suspension K&C characteristic data were got.A data processing method for suspension K&C characteristic result was proposed. With this method, comparisons of the K&C characteristic curves and values of the target and standard vehicles were got. Based on the research of suspension structure and movement principle, effects of hard-point coordinates movement and bush deformation on suspension K&C characteristics and performance of the vehicle were discussed qualitatively. A sensitivity analysis which used the K&C characteristic values of the standard vehicle as the design objects was presented to analyses the sensitivity of the front and rear suspension hard-points and bushes of the of the target vehicle. With the multi-island GA preliminarily, the suspensions were optimized firstly, then the design variables which had larger affects on design goals were adjusted according to the results of the sensitivity analysis. Eventually, the suspension K&C characteristic curves of the optimized target vehicle had a better match. Target vehicle models before and after optimized for dynamic simulation were established. Angle gradients of steering, roll and pitch were analyzed in vehicle stability simulations, so were the maximum lateral accelerations. Characteristics of the understeering and pitch angle had different degrees of modifications after been optimized. Research shows that methods of modeling, data processing of K&C characteristics and optimization for suspension are reasonable and effective. With these methods, the suspension performance could reach the design goals after being optimized. This paper has positive reference meanings to the research and design of suspensions.