Vehicle Suspension K&C Characteristic Simulation Analysis And Hardpoints Optimization Based On Virtual Prototyping Technology

Vehicle suspension system as an important part of vehicle chassis system plays an important role in the influence of whole vehicle handling and riding characteristic, as a result the research of vehicle suspension system becomes an important field in the study of vehicle. Suspension K&C characteristic as an important research direction of suspension system, plays a decisive role in the influence of vehicle handling characteristic. The paper mainly does the research on the model building of suspension system and simulation while making optimization of suspension hardpoints based on a vehicle chassis system developing project.Traditional chassis developing process does not consider the influence of hardpoints on the suspension K&C characteristic at the beginning while solely considering whole vehicle assemble based on which make car models, and then making adjustment and whole vehicle tuning. This flow not only costs much time and money but also tolerates small changes in the hardpoints coordinates, as a result we mainly adjust suspension characteristic through bushing tuning and the effect is not so well. With the development of computer tech and virtual prototyping tech, vehicle companies try to develop new chassis development flow, building suspension virtual prototype based on vehicle assemble firstly and then making simulation. Comparing the difference between prototype and target vehicle and making optimization of suspension hardpoints can guarantee the characteristic of suspension system before car model building and decrease the period of chassis development. The main contents of the paper are as following:Firstly, build the front and rear suspension system of prototype vehicle while building flexible bodies of stabilizing bar and longitudinal arm for the purpose of guaranteeing the model precision. And confirm the stiffness of springs in the front and rear suspension system based on designed frequency of prototype vehicle.Secondly, evaluation guide lines and simulation analysis means of vehicle suspension K&C characteristic are proposed. The target vehicle K&C characteristic is made on the Lotus suspension testrig and then a comparison is made between prototype vehicle simulation results and target vehicle experiment results which help find the difference between both vehicles such as the characteristic of toe angle in the front suspension under wheel parallel travel circumstance.Thirdly, key hardpoints which have great influence on the front and rear suspension K&C characteristic are obtained by using a sensitivity calculation mean developed by the author and the paper prove the exactness of the mean through geometry analysis.Fourthly, using front suspension toe angle characteristic as an example, single target optimization is made utilizing the key hardpoints obtained by sensitivity analysis. A regression model is obtained through using RSM mean which is optimized in hard points adjustable scope. By optimization, the toe angle of prototype vehicle is about the same as target vehicle while the other characteristic changes a little, which proves the feasibility of single target optimization.Fifthly, the paper obtains the regression model between toe angle, base change, track change and suspension key hardpoints aiming at solving the problem of multi objective optimization in the tuning of vehicle. A comparison is made between prototype vehicle and target vehicle suspension characteristic, though not all the characteristic of prototype vehicle is the same as that of target vehicle, but a great improvement is obtained after optimization which proves multi objective optimization mean usable for the improvement of suspension K&C characteristic.Finally, the paper probes into the confirmation of power coefficient used in multi objective optimization for the purpose of decreasing the complexity of multi objective optimization. A radar picture is made based on multi objective optimization feasible scope according to engineering practice, which facilitates engineers making suspension characteristic matches. The paper proposeαsuper plane based mean to help confirm the power coefficients according to engineering practice.Suspension K&C characteristic is not only influenced by hard points but also influenced by bushing stiffness, especially the C characteristic of suspension is always adjusted by bushing tuning. The paper does not do research on the influence of bushing, and also as a result of the chassis long development period, the paper does not make a comparison between prototype practical vehicle characteristic and the simulation results. In multi objective optimization, the confirmation of the power coefficients is need to be studied deeper, how to obtain favorable results which are much nearer to engineering practice will be the pivot of the next period of research. The sensitivity analysis mean, optimization mean, the confirmation of multi objective optimization power coefficients and radar picture of multi objective optimization feasible scope are achievements in practical vehicle chassis development which can be the reference of chassis development.