Research Of Assist Characteristics For Vehicle Electro-hydraulic Power Steering System

Subject in the study is concerned above all else with electro-hydraulic power steeringsystem (EHPS), assistance characteristics is studied according to research and improve ofassistance characteristic curves. As the electro-hydraulic power steering system uses amotor to driven hydraulic pump, motor speed is processed and regulated by the controlleron the basis of the velocity and torque, namely, providing power is also variable finally.This characteristics that the steering assist torque of EHPS changes along with the vehiclespeed and steering torque called steering assistance characteristics, and its associated curveis assistance characteristic curve, which determines vehicle’s steering maneuverability,steering road feel and driving stability.This paper describes detailedly electro-hydraulic power steering system structures,types of hydraulic systems, steering systems working principle and features, proposes thatassistance characteristics take one of the major considerations for this research, anddetermines the significance of the characteristic curve of the study. Describing the content,concept, classification, design principles and design methods of assistance characteristiccurves, fitting function expression of assist characteristic curve using data fitting functionof MATLAB. In the light of the feature of the assisted characteristic curve analysis,presented to characteristic curve of improvements to improve the vehicles assistancecharacteristics. Analyzing the performance and principle of the motor, pump, the rotaryvalve, the steering wheel, the torsion bar, rack and pinion steering, hydraulic cylinders andthe tire, submodels of the various components are built by AMESim, the system is built upfinally. Therefore, this article have a serious study of assistance characteristics focusing oncharacteristic curve, and an improved method of power characteristic curve is proposed.How to get steering maneuverability at low speed and clear steering road feel at highspeed is the main problem of vehicle hydraulic power steering system. Assistancecharacteristics of electro-hydraulic power steering system is studied in order to get a good steering performance, because the steering torque and system performance characteristicshave a direct relationship, so the steering wheel torque should be analysed. Consequently,analysing the relationship among the steering wheel torque, power torque and lateralacceleration through simulation can obtain simulation analysis results about assistcharacteristic curve before and after improvement. Setting the parameters in the modelparameters of AMESim model, vehicle speed parameters were set to10km/h,40km/h and80km/h, module function curve’s arcradius were respectively0.5,3.0and8.0, simulationanalysis of maneuverability and road feel test can be done. From the simulation results ofthe study, in a word, may also prove that studying assistance characteristics is necessaryand characteristics curve design method is right, this study make to get a better steeringperformance, and improve vehicle handling, safety and stability.