1. 研究目的与意义（文献综述）

the car suspension is an important part of the connection between the body and the wheel, and it is the general name of all force transmission devices between the two. its function is described in the "automotive construction" textbook. the vertical reaction force, longitudinal reaction force, lateral force acting on the wheel, and the torque caused by these reaction forces are transmitted to the body to ensure normal driving of the vehicle. it is mainly composed of three parts: elastic element, shock absorber and guide mechanism. as far as the mid-size car market is concerned, the medium-sized cars represented by the mercedes-benz c-series, the bmw 3 series, and the audi a4l, without exception, chose the multi-link independent suspension as the rear suspension. we can see that in the medium-sized car sector, multi-link independent suspension has become the best choice.

the model bmw brilliance 3 in this design is a medium-sized vehicle launched by the brilliance bmw joint venture on the basis of the original bmw 3-series for the chinese market. the market price is between 300,000 and 400,000. its benchmark model is mercedes-benz c-class, audi. a4. undoubtedly, they collectively chose the multi-link independent suspension as the rear suspension of the model car. it is mainly composed of connecting rods, shock absorbers and damping springs. it’s connecting rods are larger than normal suspensions, and conventionally, they generally hang four-link or more link structures, and are therefore called multi-links. suspension structure and performance parameters will directly affect the dynamic performance of the car, including the three aspects of the ride comfort, handling stability and comfort of the vehicle. therefore, for the design of medium-sized vehicles, special attention should be paid to the structural selection of the car suspension along with parameter settings and suspension tuning. choosing a suitable suspension for a car can reduce the difficulty of vehicle, ramp;d and save the development cost while ensuring the performance of the car. it can find a balance between costs and function. previously, multi-link suspension was relatively complicated due to material cost and ramp;d. experimental costs and manufacturing costs are much higher than those of other types of suspensions, and they occupy a large space. this leads to generally large and medium-sized cars. luxury cars will usually assemble such suspensions. but, with technological innovation, the needs of the market, and with the increase of competition, major manufacturers have chosen to gradually lower the multi-link suspension to medium-sized cars and small cars. the functional characteristics of the multi-link suspension are: due to the large number of connecting rods, the verticality between the wheel and the ground can be ensured as much as possible to minimize the body tilt and ensure the tire's performance.

2. 研究的基本内容与方案

fundamental contents:

1. structural selection of the rear suspension of the bmw brilliance 3 series (structural analysis and alternatives).

2. design and calculation of rear suspension of bmw brilliance 3 series (determination of main parameters of macpherson suspension).

3. 研究计划与安排

4. 参考文献（12篇以上）

[1] he chao. a new level of multi-link independent suspension of the automobile suspension system[j]. contemporary cars, 2007(08):92-93.

[2] peng xuyang, dong yiliang. influence of twisted beam type and multi-link suspension characteristics on driving stability [c]. annual meeting of china society of automotive engineers. 2009.