Analysis And Optimization Design Of Front Wheel Alignment Parameters

This paper was completed based on the project that "Optimization of FrontWheel Alignment for Light-truck Vehicle" supported by a domestic automanufacturer in Shandong province. In this paper, an optimization theoryfor the relation between steering force, rudimental yaw rate and the casterand kingpin inclination is got by way of function. In virtual of multi-bodysystem dynamics and virtual prototyping technology, all kinds ofthree-dimensions solid models and structure specifications of the light-truckvehicle were imported into ADAMS software after those were redefined inreason, and the virtual prototype of full vehicle was assembled based on allkinds of aforementioned virtual prototype subsystems created. Theexperiment validation were made focus on the Pylon course slalom test,Steering transient response test, Steady static circular test procedure,Returnability test and Steering efforts test procedure. At last, theoptimization theory is logically used on the vehicle. It is proved by test resultthat the returnability and the handiness of the vehicle with optimizedalignment parameters is more perfect.The whole article included six chapters:In chapter one, we itemized the growing history and future trend of the frontwheel alignment parameters, the influence of the front wheel alignmentparameters to handing stability. We reviewed the relationship of handingstability and the drive safety, the growing history of handing stabilityresearch, the evaluation of handing stability. At last, a brief described theresearch content and significance.In chapter two, Analyzed the steering moment on the vehicle front wheelsand a calculation model of self-turning moment and steering resistingtorque is introduced. Based on this model, the relation between steeringforce, rudimental yaw rate and the caster and kingpin inclination is got byway of function. Based on these function, a theory for optimization of thekingpin inclination and caster is brought out.In chapter three, by the theory of multi-body system dynamics and virtualprototyping technology, all kinds of three-dimensions solid models andstructure specifications of the light-truck vehicle were imported into ADAMSsoftware after those were redefined in reason. The virtual prototypes offront and rear leaf-spring dependent suspension were created in ADAMSaccording to spring , damper and bushing characteristics and dealing withthe restriction relations and boundary conditions among of parts. The tire,steer and power system models were established also. Finally, the virtualprototype of full vehicle was assembled based on all kinds of afore-mentioned virtual prototype subsystems created. The kinetic motions of thevirtual prototypes of dependent suspension were simulated and analyzed inADAMS/Car. Therefore, the changes of wheel alignments that areinclination angle, caster angle, camber angle, toe angle and wheel rate,wheel tack were presented when wheels bumped and rebounded in thispaper.In chapter four, the Driver Control Files for the simulation analyses ofcontrollability and stability of full vehicle were defined based on "GB/T6323.1-94~GB/T6323.6-94 controllability and stability test procedure forautomobiles". Pylon course slalom test, Steering transient response test,Steady static circular test procedure, Returnability test and Steering effortstest procedure. The simulation results were evaluated for the full vehiclemodel based on "QC/T 480—1999 Criterion thresholds and evaluation ofcontrollability and stability for automobiles". The validation results indicatethat the model has relative high accuracy, so it can be used to prove theresult of optimization design.In chapter five, based on the optimization theory, a reasonable optimizationdesign of the vehicle was brought out. It is proved by test result that thereturnability and the handiness of the vehicle with optimized alignmentparameters are more perfect. Finally, it is proved that the optimizationtheory is rational.Chapter seven is the summarization of the article. Depicted the mainresearch work, related conclusion and meaning of this dissertation, andlisted some of the future research fields.In conclusion, the front alignment parameters have critical effect on thehanding stability and driving safety of vehicles. At the same time, we canimprove the driving performance by reasonably optimization design of thefront alignment parameters. In this article, a new optimization theory forfront wheel alignments is analyzed, and several tests on the vehicle showthat the optimization theory is reasonable and for reference of this kind ofvehicle's improvement. In addition, the analysis of the vehicle's dynamicsby virtue of computer simulation also has reference value.