Study On Modeling Of Vehicle Load-Carrying System Dynamic Behavior

The accurate simulation of vehicle dynamic load lays the foundation of automobile parts de-sign for reliability and durability. The existing dynamic models based on assembly characte-ristics adopt only linear or non-linear stiffness and damping to describe the characteristics ofload-carrying system. There is no detailed modeling of hysteresis characteristics that affectthe dynamic load. Therefore, in the development process of the vehicle performance targetdecomposing into assembly performance targets, the vehicle manufacturers provide onlyperformance parameters for parts manufacturers. Without dynamic load parameters provided,parts design for reliability and durability would be much more challenging for parts manu-facturers.This paper mainly analyses dynamic modeling of the hysteresis characteristics ofload-carrying system in order to improve the model of load-carrying characteristics of sus-pension and carcass. Meanwhile, the method of identifying all the model parameters fromcomplex test data is studied, thus providing support for accurate simulation of vehicle dy-namic load.The structure of the paper is as follows:First, the modeling method of the load-carrying system hysteresis characteristics is stu-died. The load-carrying system model in this paper mainly includes suspension load-carryingcharacteristics model and carcass load-carrying characteristics model. Based on traditionalmodels of suspension stiffness characteristics and absorber damping characteristics, the sus-pension load-carrying characteristics model in this paper mainly adds friction characteristicsmodeling and viscoelastic properties modeling. ASCL friction model is adopted to describesuspension friction characteristics, while Maxwell element is adopted to describe the viscoe-lastic properties. Based on traditional models of carcass stiffness characteristics, the carcassload-carrying characteristics model in this paper mainly adds frequency-dependent proper-ties modeling and friction characteristics modeling. A damper in parallel with a Maxwellelement is adopted to describe the dynamic stiffness changes in higher frequency excitation,while ASCL friction model is also adopted to carcass model.The vehicle load-carrying characteristics tests are studied. Based on systematic study ofmeasurement principles and suspension test rig, quasi-static, sinusoidal and continuous step tests are done to measure the vertical displacement and force of the test rig and of the wheelcenter. This provides data support for model parameter identification.This paper mainly discusses the parameter identification of the suspension load-carry-ing characteristics model. Since one-time identification of all parameters would bring aboutlow identification efficiency and parameter confusion, a parameter separation method isadopted. Static parameters are first identified from the quasi-static test data, using leastsquares method. Then the dynamic parameters are identified from the sinusoidal test data,using complex stiffness method. Since carcass load-carrying characteristics model is similarto suspension load-carrying characteristics model, the identification method of the former, inthis paper, could be tried to adopt a similar method of the latter.Validation and verification of the model are studied. With vertical displacement of testrig in the continuous step test being set as input, the simulation of the vertical force at thewheel center is compared with experimental data. Results validate the reliability of the mod-el in simulating dynamic working conditions. The model in this paper and the traditionalmodel are both simulated with pulse excitation and random excitation. Results verify the re-liability of the model in reflecting the impact of the hysteresis characteristics ofload-carrying system to dynamic load.