Research On The Assist Characteristic Of Electric-hydraulic Power Steering System

Automotive power steering gear is a key element to decide the overall quality ofvehicle. As vital for the vehicle as the engine and the wheels, as important for safety as thebrake, the power steering system is at the heart ofevery vehicle. It directly affects the car’shanding and stability, safety and ride comfort.This paper is mainly based on a type of Electronically controlled Hydraulic PowerSteering gear as the research object, and the assist characteristic of the EHPS powersteering is studied. It can provide different steering according to the different conditions, soit can improve the low-speed steering portability, and can guarantee the steering”feel” athigh speed. The main contents of this contents of this subject include:Firstly, this paper introduces the research status and development trend of the existingautomobile power steering, summarizes the classification and work principle of steer ingsystem, and expatiates on its strengths and weaknesses.Secondly, discusses the structure, function and characteristic of the Electronicallycontrolled Hydraulic power steering, then starting from the oil circulation perspective, weanalysis the power principle in different speed.Then the power steering valve characteristics were studied. Through the establishmentof mathematical model of power steering relay valve, the theoretical formulas at low speedbetween the steering wheel torque and hydraulic cylinder at both ends of the pressure werederived. The theoretical curves of assistance characteristics can be obtained by computersimulation. Through the computer simulation, we analyze the influence of structureparameters of rotary valve power characteristics at low speed.And then based on the reasonably simplified of the power steering system, weestablished the mathematical model of by-pass, through orifice flow formula, systempressure and flow equation, the power characteristic curve at different speeds are obtained.Finally, on the basis of the relevant laws and regulations，we set the power assistedsteering gearbox, and get the steering assist curve under different conditions. Throughanalysis and summary of the test data, we compared it with the simulation of dynamicalcharacteristics, the experimental results showed that and verify the validity of the model.