Research And Optimization Of Bushing Stiffness Of Front Double-Arm Suspension

There had more and more bushing in the suspension of modern car.Many researches showed that compositive dynamic character affectsteering smooth, operative stability and braking observably. Therefore, it isimportant to research the effect of suspension bushing stiffness to elastickinematics rules. The effect of bushing stiffness of double-arm suspension to elastickinematics was researched in connection arm with body-frame. With thehelp of ADAM/Car Template Builder and CATIA, the dynamic simulationmodel of the front double-arm suspension was made. During the course ofmaking model, the way of making model was introduced by ADAMS/CarTemplate Builder. ADAMS/Car and CATIA was combined by interface.The main aim of research is that the effect of bushing stiffness to wheelalignment parameters and wheel rate. Firstly, the basic suspension conceptand basic configuration of double-arm suspension was introduced;then thebasic principle of elastic part-bushing and configuration was also introduced,and the calculation of bushing stiffness in ADAMS/Car was showed. Finally,the original bushing stiffness was given by editing bushing files inADAMS/Car.Ran the parallel wheel travel test, compared the results of wheelalignment parameters and wheel rate in rigid body model and flexible bodymodel, it can be showed that the suspension bushing have obvious effect towheel alignment parameters, the value of wheel rate have also obviouschanges without preload. So the effect of wheel rate should be consideredwhen wheel rate was researched. Compared with the rigid body models withrigid constraint, the flexible body models can reflect the same variationaltrend as real car.In ADAMS/Car, ran the parallel wheel travel test respectively whenbushing stiffness was different numerical value. The result of thesesimulation tests was compared, which can show that the variational rules ofwheel alignment parameters and wheel rate along with the changing ofbushing stiffness. For this suspension, the bushing stiffness values arebigger, the suspension kinematics characters have a little change;thebushing stiffness values are smaller, the suspension kinematics charactershave more change;The conclusion by analyzing can be used to adjust thebushing stiffness of the suspension in order to meet to the requirement.During the real course of research, the simulating models should beanalyzed deeply after making models, simulation analysis and processingthe dates. The simulating models can be modified by manpower again andagain and draw the satisfying conclusions. But, this way should do muchrepeated work, and the conclusion is not always best. In fact, the optimizingfunction of ADAMS/Insight can improve the optimizing efficiency. Afteranalyzing the variational rules of wheel alignment and wheel rate along withthe changing of bushing stiffness, we begin to optimize the model of thefront double-arm suspension with help of ADAMS/Insight designoptimization software.There are three methods to optimize the parameters:?Design research: consider the effect of one design parameter to thesimulating models;?Design of experiment (DOE): consider the effect of many designparameters to the simulating models at the same time;?Optimization: get the parameter configuration the responses is the bestin the range of design parametersADAMS/Insight combined the DOE with the optimization. In the paper,the bushing forces scaling more change the wheel alignment parameterswere as design parameters. Camber angel, kingpin incline angel, wheeltrack and wheel rate were as optimizing aim. The changing rang of thecamber angel is smaller, the optimization result is better. The camber angelis both positive and negative during the simulation, so the aim responsesshould be absolute value maximum. The changing rang of the kingpinincline angel is smaller, the optimization result is better. Kingpin inclineangel is positive during the simulation. The graph is parabola and minimumvalue is near freeload value. So the aim responses should be maximumvalue. The changing rang of the wheel track is smaller, the optimizationresult is better. Wheel track is positive during the simulation. The graph isparabola and maximum value is near freeload value. So the aim responsesshould be minimum value. The changing rang of the wheel rate is smaller,the optimization result is better. Wheel rate is positive during the simulation.The aim responses should be near the freeload value.Firstly, the bushing force scaling takes different values, then, the workspaces were done automatically by ADAMS/Insight and begin the simulationcalculation. Finally, the calculating results were optimized by filtering thework spaces. Compared the original model with optimizing model, it can beshowed that the changing range of camber angel and Kingpin incline angelbecame small obviously so that steering smooth and operative stability ofsuspension in the optimizing model become better. But the changing rangeof wheel track became big, which increase the tire abrasion.Mathematical formulation and solution of vehicle multi-body dynamicsequations are also not feasible, so building and testing of physicalprototypes for optimization purposes consume significant amount of time,manpower and financial resources. The proposed method is fast, costeffective, saves considerable manpower and has a flexible architecture toexplore large design spaces, so this optimizing method is beneficial to directthe optimization design of vehicle.Suspension elastic kinematics model have also some limitation, suchas the metal parts work as rigid part in simulating model, without consideringthe elastic transformation pressed to affect wheel alignment parameters,which can make mistaken. For time and research equipment were limited,the design parameter was reduced during optimization. So ADAMS/Insightwork space matrix was reduced and the better optimizing results can't begot.