Study Of Steady State Tire Model

As the application of large-scale multi-body systematic dynamics softwarein vehicle dynamics simulation, the study of tire properties has been focused anddeveloped. All kinds of tire theoretical models, empirical models andsemi-empirical models have been applied in the simulation of vehicle dynamics.Especially, Magic Formula, which has been put up with by Prof. Pacejka inHolland, represents the automobile handling tire model broadly used in vehicledynamics simulation. But these tire models including theoretical models,empirical models and semi-empirical models must be validated by tire test data.However tire tests are restricted by test equipment. And there are so manyfactors that may have a big effect on the tire tests, such as tire and road types,longitudinal slip, slip angle, vertical load, tire traveling velocity, etc. It isimpossible to conduct all the tire tests considering all the factors. So the tiremodels with the function of prediction will reduce the cost of tire test, cut theexperimental condition restriction and shorten the automobile developmentcycle.Based on the previous work on the study of tire properties, this paperstudies the generalized brush model of cornering and camber property witharbitrary contact pressure distribution considering dynamics frictionalcharacteristics and camber effect and the generalized theoretical model oflongitudinal and cornering property with arbitrary contact pressure distributionconsidering dynamics frictional characteristics. On the basis of theoretical studyand experimental analysis, UniTire semi-empirical tire model is brought forward,which satisfied the high order theoretical boundary conditions. UniTire andMagic Formula tire models are compared in terms of the modeling mechanics,global identification precision and cornering stiffness. UniTire model has theability of predicting the combined slip tire forces from pure slip tire test data andpredicting the high speed performances from the low speed tire tests. These havemade a good foundation for the application of UniTire model in the automobilehandling tire models.First, in the previous generalized brush model of cornering and camberproperty with arbitrary contact pressure distribution, dynamics frictionalcharacteristics with camber effect is introduced, and the experiementalphenomenon of lateral forces with camber is explained. The effect of the camberon cornering stiffness is studied. The aligning moment modeling method isprovided.Second, in previous the generalized theoretical model of longitudinal andcornering property with arbitrary contact pressure distribution, dynamicsfrictional characteristics is introduced to make it perfect. The study of theoreticalmodel provides theoretical basis for the UniTire semi-empirical tire model.Because the theoretical study has certain simplification and assumptions thatmay bring some errors to the semi-empirical tire model, the shear force directionand longitudinal stiffness in combined slip condition have been revised.Third, The comparison of the two models has been made through modelingmechanics analysis, global identification precision and lateral stiffness testvalidation.Fourth, after the introduction of UniTire two prediction methods includingthe pure test data prediction and partial test data prediction, the precisioncomparison between the two prediction methods and the global identificationmethod. And after the introduction of Similarity method, COMBINAOTORmodel and Lund model, the comparison between these models and UniTire puretest data prediction method is presented separately.Finally, the abilities of predicting the high speed tire force and momentcharacteristics from the low speed tire tests is studied by means of the UniTiremodel using lateral tire test data under different speeds, including the effects ofthe speed on the dynamics frictional coefficient, on the lateral stiffness, and onthe pneumatic trail.