Comparison Of Typical Vehicle Steering System Models

To further improve the laboratory ASCL steering system model, building a completedynamical model that has high simulation accuracy and can be used in pre-developmentstage of vehicle products, promoting industrial applications of driving simulators, sometypical steering system models are studied, including the steering system used in theNational Advanced Driving Simulator (NADS model), the steering system model usingsteering characteristic functions (SCFs model) and the steering system model developed byWarsaw University (Warsaw model). Through the contrasts of the modeling method, modelparameters and the simulation of working conditions of the typical steering system models,summing up the advantages and disadvantages of these typical steering system models, anew version of the ASCL steering system model has been established based on the2008ASCL steering system model. The main work and conclusions of this paper are as followsThrough the contrasts of the modeling mechanisms of the typical steering systemmodels, the different modeling methods are summarized. For the description of theAckerman steering mechanism, the NADS model and SCFs model don t build the mechaniccontacts of the left and right wheels; the2008ASCL model and the Warsaw model build thedynamical connection of the left and right wheels through the rack (gear) dynamic and thewheel dynamics around the left and right kingpins. The NADS model and SCFs modeldescribe the elastic properties of the steering column, while the2008ASCL model and theWarsaw model describe the elastic properties of the steering column and the tie rods. Todescribe the steering dry friction, the SCFs model builds a dry friction model based on theCoulomb model, the2008ASCL model establishes a static-dynamic separation frictionmodel based on the Karnopp’s model, the Warsaw model establishes the Stribeck dynamicfriction model. In addition, the NADS model and the Warsaw model describe the steering clearance. Therefore, the new version ASCL steering system model should describe themechanical properties of the Ackerman steering mechanism, the steering system flexibilitycharacteristics and the nonlinear characteristics of dry friction and the steering clearance.Through rebuilding the NADS, SCFs and Warsaw models, and the discussions of theacquisition of the model parameters, the modeling features and the complexity of the typicalsteering system models are summarized. The NADS model and SCFs model ignore the highfrequency characteristics of the steering system, so the models have low complexity, and themodel parameters are easy to obtain. The2008ASCL model and the Warsaw model candescribe the high-frequency characteristics of the steering system. The2008ASCL model isestablished based on the detailed Ackerman steering mechanism structure. The depending onthe specific structural parameters of the Ackerman steering mechanism determines that themodel cannot be used in the pre-development of the vehicle products. The Warsaw modelsubstitutes the mechanical structure of the steering system model by its equivalent physicalmodel consisting only of rotating plane elements. So the model does not have to rely on thespecific structure of the Ackerman steering mechanism. Therefore, the new ASCL steeringsystem simplifies the mechanical structure of the steering system into equivalent physicalmodel consisting only plane rotation components, reducing the complexity of the model andensuring the parameters easy to obtain in the vehicle pre-development stage.In order to compare the typical steering system models in the simulation of workingconditions, a vehicle dynamic model has been established, with the typical steering systemmodels embedded in the vehicle dynamic model through interface setting. Select the anglestep input, small-angle perturbation input, sinusoidal input, and the steering wheel input inthe road-like and parking-like conditions as the model input in simulation. Throughsimulation comparison, we can find that the NADS model and SCFs model can behave wellin the steady-state condition, while its transient simulation capability is poor. And the NADSmodel and SCFs model cannot resist outside interference input. The2008ASCL model andWarsaw model can behave well in the steady and transient conditions. And the2008ASCLmodel and Warsaw model can resist the outside interface input.The new ASCL model has been established based on the comparative study on thetypical steering system models. The new ASCL model builds the pinion rotation dynamicsand the wheel dynamics around the left and right kingpins. It describes both the elasticproperties of the tie rod and the steering column. A static-dynamic separation friction modelis built in the new ASCL model. And the new ASCL model describes the nonlinear characteristics of steering clearance. The real vehicle tests verify that the new ASCL steeringsystem model does very well in the simulation of vehicle resistance to steering wheel inputand the disturbance of the uneven roads. The new ASCL model can calculate the steeringwheel torque precisely.Through the research of this paper, a steering system model that can be used in thepre-development of the automobile products has been established. The steering system thathas been built is a complete steering system model with low complexity. And the modelparameters are easy to obtain. At the same time, the laboratory model database is enrichedthrough rebuilding the typical steering system models. The appropriate steering systemmodel with different research purposes can be selected.