Study On Steering Performance Development Process For Passenger Car

As consumption upgrading,domestic automobile consumer groups are also increasingly mature,people are no longer just focus on the styling and quality of Cars,excellent driving experience becomes a significant factor in purchase decisions.Handling performance deals mainly with the vehicle's responses to high steer rate and larger amplitudes steering wheel angle,and is focus on the extreme conditions,which can hardly be experienced by normal drivers in daily driving.On the other hand,steering performance deals mainly with vehicle's low to mid-range lateral acceleration response to steering wheel angular and torque inputs,which can be directly experienced by normal driver.Therefore,improving the steering performance is critical to driving experience.At present,steering performance development process is not mature enough.Lacking of reasonable steering performance evaluation metrics,causes the setting targets are mutual dependence or mutual contradictory,and therefore these steering performance targets are hard to be cascaded into systems and subsystems in concept design phase,all the goals need to be reached by tuning,and the final results may be a compromise.This paper is mainly focus in establishing a reasonable,irredundant objective evaluation system for steering performance.Accurate models for steering system,suspension,tire and full vehicle are built.This makes steering performance simulation becoming possible in concept design phase.The main contents of this paper are as follows:First,axiomatic design theory is studied.The two basic axioms of axiomatic design,namely independent axiom and information axiom,establish the screening criteria of steering performance,objective evaluation index and working condition,that is,the indexes and working conditions should be independent of each other.Through the axiomatic design flow,namely the user domain,the function domain,the physical domain and the process domain four domains mapping in sequence,has established the steering performance positive development direction.The General Motor's "user routine driving" model has been analyzed,and combined with the actual situation in China,the scope of steering performance has been determined.Steering performance can split into on-center range and linear range.It also can be divided into high speed and low speed.Through investigating the needs of the users,and analyzing existing performance evaluation index system,a set of objective evaluation indexes one to one corresponding to the user's needs are been found out.With analysis of the selected objective evaluation index,design parameters which have influence on these indexes are selected.Design matrix of function domain to physical domain has been analyzed,and finally the steering performance is decoupled.Secondly,the characteristics of the steering system are studied and modeled.The stiffness,clearance,damping,friction and assistant characteristics of the steering system have an important influence on the steering performance.In this paper,the stiffness characteristics and friction characteristics of the steering system are studied,and the stiffness and friction composition and distribution of the steering system are defined.The e index model is adopted to unify the stiffness characteristics and the clearance,so that the modeling of the gap characteristics is avoided.The friction model is studied,and the friction of steering system is established by using Dahl friction model.The model can well represent the characteristics of friction memory.Finally,Advanced modeling research is carried out for a specific A-Class passenger car in ADAMS/Car.Based on the study of the characteristics of the steering system,a mechanical model of the high accurate steering system is built.The Simulink model of the EPS control system is integrated into the ADAMS/Car through ADAMS/Controls.A high accurate model of suspension system is established.The tire model was studied,and the mechanical properties of the tire were tested at high speed tire test rig.The PAC2002 tire model was obtained by ADAMS/Car Tire tool identify the test data.On this basis,a vehicle model is built.The accuracy of the model is verified by comparing the K&C characteristics of the suspension and the vehicle steering performance simulation and test results.