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1. 研究目的与意义（文献综述）

Ⅰ. research objective and significance

asteering system is a series of devices used to change or keep a car moving orgoing backwards. the function of the steering system is to control thedirection of the car according to the driver's wishes. car steering system isvery important to the safety of the car, is the car safety must pay attentionto one of the two systems, so the car steering system parts are called securityparts.

automobilesteering systems are divided into two categories: mechanical steering systemsand power steering systems. the mechanical steering system takes the driver'sphysical strength as the steering energy, and the power steering system is asteering system that uses both the driver's physical strength and the engine(or motor) power as the steering energy. its emergence and development also hascertain process, the first is the traditional mechanical steering system, thenon the basis of the research and production of hydraulic power steering system,due to the demand of the market changes, system in updated and improvedcontinuously, the electronically controlled hydraulic power steering system,which implements the electronic control, and with the further research, and hasproduced the electric power steering system, which is what we call the epssystem.the traditional mechanical steering system is the foundation of thedevelopment of the whole steering system. at the beginning, this system mainlyrelies on human power, which is troublesome to use. moreover, it cannot play anauxiliary role for the heavy load vehicles, and it will cause damage to thewhole system due to the heavy load.then on the basis of the development of mechanical hydraulic booster andelectronically controlled hydraulic power steering system due to solve theproblem of the traditional mechanical steering system, widely used in thecurrent car market, but this kind of hydraulic power system need to use thevariation of hydraulic power, so the cars need to store large amounts of oil,if car storage system problems lead to oil leakage, damage to the environmentnot only, and may cause damage to cars and even explode.electric power steeringsystem this new type of steering system does not rely on oil pressure toprovide steering power, mainly relies on electricity, in the car to install thecorresponding power supply equipment, driving the motor to provide power to thesteering system.electric power steering system (eps), compared with thetraditional power steering system, has the advantages of energy saving andenvironmental protection, convenient installation and maintenance, the powercan be adjusted with the speed change, fast response, so that the driver alwayshas a good sense of "road" and other advantages, is widely used inmajor automobile brands.

inthe more than 30 years since the emergence of the electric power steeringsystem, the eps system has been rapidly developed, from the very beginning whenthe electric power steering system was only used when the car was parked at a lowspeed, to the development of the full-speed model, so that the car can beoperated and controlled at full speed.the application scope of eps system isalso more and more extensive, from the beginning of the medium - sized micro -car applications have been expanded to mid - and high-end cars.

2. 研究的基本内容与方案

1. Basic content and objectives

Objectives:

（1） Calculate wheel steering resistance;

（2） Design and calculation of steering trapezoid parameters;

（3） Ackermann Angle and theoretical error analysis;

（4） Select booster type; Power characteristic analysis;

（5） Booster motor design; Design of decelerating transmissionmechanism;

（6） Steering gear design;

（7） Design of torque sensor and speed sensor;

（8） EPS system transmission mechanism assembly design.

Basiccontents:

（1） According to the design parameters of the vehicle, the staticin-situ steering resisting moment, steering teaming angle transmission ratioand force transmission ratio can be calculated.

（2） The steering trapezoidis designed according to the design requirements of steering trapezoid when thepercentage design requirements of ackerman are met.

（3） Determine the powercharacteristic curve, according to the basic requirements of the powercharacteristic curve for the power characteristic curve matching design;

（4） According to the type ofsteering power, determine the steering motor parameters, motor selection, motorrated torque, rated voltage, rated power and rated speed determination;

（5） According to therequirements of the steering gear selection and design check.

2. Technical plans and measures

1. The vehicle parameters.
2. Wheel steering resistance calculation.
3. Design calculation of steering trapezoid.
4. Ackermann Angle and theoretical error analysis.(If the requirements are met, proceed to the next step.If not, go back to the previous step and start again)
5. Selection of booster motor and design of decelerating transmission mechanism.
6. Steering gear design and selection.
7. EPS power characteristic analysis.(If the requirements are met, proceed to the next step.If not, go back to the previous step and start again)
8. Design of torque sensor and speed sensor.
9. EPS transmission mechanism assembly design.

3. 研究计划与安排

1-2 (week 18-19 of the 7th semester) : determine thegraduation project topic, improve the graduation project task book (relatedparameters), and collect the materials inside and outside the school.

3-4 (week 1-2 of semester 8) : project design, literaturesearch, completion of proposal report.

5 (week 3 of semester 8) : foreign language translation,data collection.

4. 参考文献（12篇以上）

[1] li bing, wang lanhong. design ofdual-source electric power steering system for electric buses [j]. journal ofuniversity of science and technology. 2018, (06). 77-81.

[2] zhao wanzhong, wang chunyan. automotivepower steering technology [m]. beijing: tsinghua university press, 2018

[3] wang xiaofeng. automobile chassisdesign [m]. beijing: tsinghua university press, 2018