Study Of The Matching Analysis And The Performance Evaluation Of Electric Power-Assisted Steering

PrefaceEPAS (Electric Power-Assisted Steering) adopts motor to provide assist torque, which is controlled by ECU (Electric Control Unit), according to the velocity of the vehicle and the torque of the steering wheel. Because EPAS can save energy, improve vehicle active safety and conduce to environment protection, it is considered as a new high-tech which closely follows the modern vehicle development topic and has been paid close attention as soon as it's appearance. Almost all the famous automobile company abroad have developed their own EPAS and have the ability to volume-produce EPAS by now. EPAS has been also applied to some car as a elective product. Only in the recent years, the research on EPAS is carried out in china, for many reasons. But it springs up like mushrooms. There are Jilin University, Tsinghua University and some other University and company engaging in the research and development of EPAS.This paper is based on the project of Automobile electric power-assisted steering system control strategy and matching with the vehicle sponsored by Natural Science Foundation of Jilin province. The author constructs a EPAS dynamic model, and carries out the study on the EPAS focuses on the matching design and the performance evaluation, by means of simulation technology.Main ContentsIn chapter one, the merits and defects of the conventional Hydraulic Power Steering and Electric Hydraulic Power Steering are summarized based on investigating in mass reference paper. Development status quo, principle, structure, key parts, classification of the EPAS are introduced By contrast EPAS to HPS and EHPS, the author points out that EPAS have the merits of saving energy, improving vehicle active safety and conducing to environment protection, it is one of the future development direction of power steering.In chapter two, a EPAS of column type and a whole vehicle of two degree dynamic model are built up. The EPAS dynamic model of column type, pinion type and rack type are unified. Steering resisting moment is calculated. The output torque of the motor is determined by given the feature parameters of straight-line type assist characteristic. The EPAS and the whole vehicle dynamic model is analyzed and calculated by means of state-space and by contrast simulation resultto road test data, the model is proved to be valid.In chapter three, the matching design of the assist characteristic is studied. Straight-line type, broken-line type and curve-line type assist characteristic are discussed systematically. The influence of the straight-line type assist coefficient to the steering maneuverability, the road sense and the transient response of the steering are simulated respectively. The results show that increasing the straight-line type assist coefficient can improve the steering maneuverability and enhance the transient response of the steering. But the road sense in high speed is reduced. The author also gives the method to determine the coefficient of vehicle velocity of the assist characteristic. By varying the coefficient of vehicle velocity to make the steering wheel torque at 0.3g lateral acceleration the same as the conclusion of the paper [24], the coefficient of vehicle velocity can be determined. Then the straight-line type assist characteristic is determined completely.In chapter four, the matching design of EPAS key parts such as motor, torque sensor, gear box with the whole vehicle is carried out. The characteristic of four types of motor is compared. Because the permanent-magnet brushless direct current motor can provide more torque and has higher efficiency and simple controller, it is more suitable for EPAS than the other type of motor. It is summarized that the position of the motor is decided by the space of the front of the vehicle, load of the front axes and the motor characteristic, the maximal output torque of the motor should be matched with the load of the front axes, the gear box of the EPAS and the steering gear angle ratio. The rotation speed of the motor ought to mach with the rotat...