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1. 研究目的与意义（文献综述）

1.1 purpose and meaning of the study

with the development ofthe economy, the number of vehicles is constantly increasing, and the world ’soil resources are reducing. new energy vehicles, which are compared withtraditional internal combustion engines, have become the future direction ofthe automotive industry. on october 26, 2016, the chinese society of automotiveengineers released the technology roadmap for energy-saving and new energyvehicles. roadmap planning: in 2020, sales of pure electric vehicles andplug-in hybrid vehicles will account for 7% -10% of total vehicle sales; 2025,15% -20%; and 2030, 40% -50 %^[1]. battery electric vehicles(bev) are new energy vehicles that are powered entirely by rechargeablebatteries, with electric motors as the drive system. due to the use of electricenergy, no exhaust gas is emitted during the driving process of the pureelectric vehicle, which does not pollute the environment and can achieve zeroemissions. in addition, pure electric vehicles can also achieve energy recoveryand have the advantages of low noise ^[2]. after ten years ofchanging, china's auto industry has entered a period with the smallest gap withthe international level. in the field of electric vehicles, china has thesmallest gap compared with its international counterparts, and even in someaspects, china is already in a leading position^[3].

the steering system is aspecial mechanism used to change and restore the direction of the car. theearliest automobile steering gear was a purely mechanical steering system. itwas divided into a rack and pinion steering gear, worm crank pin steeringgear, recirculating ball steering gear, worm roller steering gear, etc. although a purelymechanical steering system can achieve basic steering functions, it is neitherportable nor sensitive. to solve this problem, hydraulic power steering systemand electronically controlled hydraulic power steering system were created. bythe end of the 1980s, the electric power steering system was created, and sincethen the automotive steering system has developed rapidly. the electric powersteering system is in line with the idea of mechatronics in modern automobiles.it uses the power generated by the motor to assist the driver in powersteering, and the ecu control can take into account the portability and comfortof the car^[4]. in addition, technologies such as active steeringand 4w steer-by-wire system have also been developed.

2. 研究的基本内容与方案

the purpose of thisarticle is to design a steering gear that matches a pure electric four-wheeldrive passenger car, including completing comparisons of various types ofsteering gears, selecting steering gears, determining parameters, makingthree-dimensional models, checking simulations, etc.

the main contents of thispaper include the following five parts:

(1) explain the background and significance ofthe research in this article, explain the development status of pure electricvehicles and steering gear at home and abroad, and introduce the researchtopics;

3. 研究计划与安排

week 19 of the 7th semester: determine graduationproject topics, graduation project assignments (relevant parameters), andcollection of school materials

week 1 of the 8th semester:：scheme idea, literature search, and opening report;

week 2-3 of the 8th semester: foreign literaturetranslation and data collection;

4. 参考文献（12篇以上）

[1]song yejian, gao haoqiang. analysis of technologystatus and development trend of electric vehicle [j]. automobile appliedtechnology, 2019(21):21-23.

[2]qiu xianwen. study on technical statusand development trend of battery electric vehicle [j].small internal combustionengine and vehicle technique, 2019,48(06):74-79.

[3]chen xiujuan. academician comment on newenergy vehicles’ trend [j]. automobile observation, 2020(01):111-113.