Modeling, Simulation And Optimization For Longitudinal Impact Vibration Of Minibus

With the development of the reform and opening-up policy, and the improvement of people’smaterial conditions, China minicar market is booming. Minicars are very suitable forcommon people’s requirement, and its development represent common people’s livingstandard in the Chinese characteristic market conditions. Now, the minicar market is accountfor31.65%of the whole market. But its longitudinal ride comfort is not very good and bigvibration exists.The ride comfort has been researched frequently at home and abroad, most of them are aboutvertical random vibration, few are about longitudinal vibration and impact vibration.Passengers are made uncomfortable and vehicle performance is dropped by the longitudinalvibration as well as vertical vibration. Human’s sensitive frequency range to longitudinalvibration is0.5～2Hz, longitudinal vibration is more sensitive than vertical vibration under3Hz. Impact is the system transient dynamic change process caused by sudden change of theforce, displacement, speed etc. Ride comfort is also seriously affected by impact vibration.So, it’s very important to research the longitudinal vibration and impact vibration.The purpose of this paper is to study the longitudinal impact vibration of a minibus and toimprove its longitudinal ride comfort, using the provided date and basing on parametricvehicle dynamics software Carsim. The main contents are as follows:(1) Description and determination of a minibus’s dynamic model parametersThe parameters of six modules were described in detail based on the understanding ofmodeling theory, the six modules of Carsim includes body, axle and suspension, tire,powertrain, braking and steering systems. The parameters were confirmed based on the dataprovided by company, and the model was examined to test model accuracy.(2) Analysis of the longitudinal impact vibration operating conditionsThere are three operating conditions in this paper such as start, gear-shift and road impactexcitation. For the start and gear-shift conditions, the cause of the longitudinal impactvibration is the clutch operation, so the engaging process of clutch and throttle opening inkeeping with clutch engagement is analyzed in detial. For the road impact excitationcondition, add triangle bump to the level road as the impact excitation input, the same as theride comfort impact input running test.(3) Simulation of three longitudinal impact vibration conditionsThe analysis of the longitudinal impact vibration conditions was reflected in Carsim, andthen the longitudinal impact vibration conditions were simulated. Vehicle start was divided into three forms, slow start, normal start and fast start; Gear-shift condition included upshift,downshift, downshift and rapid acceleration, leapfrog downshift; Road impact excitationcondition had six simulations of different speed, includes10,20,30,40,50,60km/h.Furthermore, the correctness of the model was verified through simple impact vibrationconditions simulation.(4) Analysis of influencing factors to longitudinal impact vibration conditionsThe sensitivity analysis of parameters is significant to improve longitudinal impact vibrationperformance. The influence of parameters was analyzed using single factor analysis method.Firstly, the parameters were chosen to analyze for every condition. There were usageparameters, vehicle parameters in impact formula, vehicle longitudinal parameters andsuspension parameters for the start; there were usage parameters and vehicle parameters forgear-shift; there were spring rate and absorber damping for road impact excitation. Then, theinfluence of every parameter was analyzed through single factor analysis method.(5) Optimization of the longitudinal impact vibration conditionsThe method of optimization is Orthogonal Design. The parameters which have significantinfluence were chosen as the experimental factor. Designed orthogonal pilot program, andanalyzed experimental index using the extreme difference analysis to get the best levelcombination for the longitudinal ride comfort improvment.Combining with “Transient Vibration Comfort of Vehicle Impact Study” of ChongqingChangan Automobile Corporation, basing on the provided data, simulated the start, gear-shift,road impact excitation condition through Carsim dynamic software. Then analyzed andoptimized the parameters influence to lower the longitudinal impact vibration.