| Recent years in the automotive technology development, with the increasing ofautomobile speed, the ride comfort, handling stability and NVH (Noise, Vibration&Harshness) characteristics of high speed vehicle has attracted more and more attention.Rubber bushing components have been widely used in automotive suspension system and itsmain purpose is to use the superior noise and vibration reduction function of rubber elasticelement. At the same time, the nonlinear characteristics of the rubber itself will affect theelastic kinematics of suspension system, which affects the handling stability of vehicle.Rubber bushings used in the suspension system is conducive to attenuate the vibration andshock of the road excitation on vehicle body, especially the high frequency excitation fromthe road, and be able to improve vehicle NVH performance significantly. However, therubber bushings also cause changes in the suspension system stiffness, and make thesuspension showing a certain nonlinear properties, such as system response lag. Thenonlinear properties cause the negative effects of the automobile steering characteristics,which reduces the handling stability of vehicle. The problems above cause the contradictionsof vehicle ride comfort, handling stability and NVH characteristics in suspension matchprocess. Furthermore, the increasing speed of car makes this contradiction more significantand the impact of factors that not reflected in low speed becomes more prominent in highspeed. In view of the complexity of rubber bushing mathematical modeling andmulti-objective optimization algorithm, the optimal matching of suspension bushings,considering the vehicle ride comfort, handling stability and NVH performances, becamedifficult problem in the development process of the suspension system.A domestic light bus had been studied in this paper and with the method of combiningfinite element and multi-body dynamics, the influence of vehicle ride comfort, handing stability and in-car noise affected by rubber bushing stiffness parameters were analyzed inthis paper. A multi-objective optimization of rubber bushing parameters was carried out byconsidered the performance indexes of the above three. The multi-objective optimizationproposed in this paper established an effective matching optimization design process forrubber bushing of suspension systems. This paper focuses on the influence of vehicleperformance affected by rubber bushing stiffness and the matching optimization study ofrubber bushing, and its main contents include the following five parts:In the first part of this paper, the purpose of this research project was proposed, and thesignificance of rubber bushing matching optimization for suspension systems developmentwas also illustrated. Then, the research status of the rubber bushings and multi-objectiveoptimization method was introduced and summarized, which described the rubber bushingstatic and dynamic characteristics of the calculation method and genetic algorithmmulti-objective optimization development overview. Finally, the main content andsignificance of this study have been proposed.In the second part, for the purpose of solving the difficult problem of rubber bushingmathematical modeling in suspension research areas, the paper carried out the research work.The rubber bushing mathematical models in the traditional vehicle dynamics studies weresimplified into elastic elements with nonlinear characteristics, which caused the lowprecision of suspension dynamics. In response to these problems, on the basis of existinglinear friction rubber bushing model, elastic lag rubber bushing model and elastic-plasticsuperposition rubber bushing model, a high-precision rubber bushing model based onsuperimposed hyperelastic unit, fractional derivative unit and friction unit is established inthis paper. The test modeling process has also been introduced in detail. The experimentalresults showed that the high-precision rubber bushing model could correctly describe thenonlinear dynamic characteristics of rubber bushing.In the third part, a rigid-elastic coupling vehicle model was established by usingSIMPACK and NASTRAN software. By using the user-defined force interface in SIMPACK,the rubber bushing model established by the programming language was imported to rigid-elastic coupling vehicle model. In this paper, the finite element method was used togenerate the flexible body model of bus frame and body. The real vehicle test data were usedto validate the rigid-elastic coupling simulation model. The results showed that the vehiclesimulation model could be used to simulate the linear and nonlinear dynamic characteristicsof suspension systems. The rigid-elastic coupling model established in this paper can providea good simulation model for multi-objective optimization of rubber bushing, and laid thefoundation for future research.In the fourth part, the influence of vehicle ride comfort, handing stability and in-carnoise affected by rubber bushing stiffness parameters were analyzed. In order to study thecab noise caused by road excitation, the dynamic load spectrum of suspension rubberbushings was calculated by the simulation of rigid-elastic coupling vehicle model. Theacoustic-structure coupling method was used to calculate the sound pressure value of driver'sright ear, which was used to evaluate vehicle structure-borne noise caused by road excitation.From the perspective of sensitivity analysis, the relationship between rubber bushingstiffness and sensitivity value of suspension characteristic was also studied. The sensitivityanalysis results can be used to determine the optimization objectives, thus avoiding theblindness of the optimization and exponentially reducing workload of optimization.In the fifth part, vehicle dynamics model and MATLAB co-simulation method was usedto carry out the multi-objective optimization of rubber bushing parameters. In theoptimization process, the RMS value of vibration acceleration of driver's seat track, the rollangle of vehicle body and the sound pressure level of driver's right ear were treated asobjective functions, and the rubber bushing stiffness parameters were selected asoptimization objectives. NSGA-II genetic algorithm was used to carry out themulti-objective optimization of vehicle ride comfort, handling stability and NVHperformance. According to the results of optimization, new rubber bushings were producedfor the vehicle test validation. The verification results showed that, the re-match suspensionrubber bushings could improve the ride comfort and handing stability of vehicle, and reducethe interior noise in the body at high speed. The paper uses simulation analysis and experimental methods to research the optimalmatching of the suspension system of rubber bushing, and elaborates on the matching designof bus suspension rubber bushings to form a more complete technical processes and researchideas. The research results of this article are significance for improving the performance ofexisting models' suspension systems, and it also has a guidance function for matchingoptimization of the other vehicle subsystems.
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