1. Purpose and significance (including analysis of research status at home and abroad)
1.1 The suspension is a general term for all force transmission devices between a frame (or a load-bearing body) of a car and an axle (or a wheel), and its function is to transmit a force and moment acting between the wheel and the frame, and damping the impact force transmitted from the uneven road surface to the frame or the body, and reducing the vibration caused thereby to ensure that the car can ride smoothly.
The Dongfeng Logo 308, with respect to design, is a new strategic model developed by the automobile group to face the global automobile market. The 308 front suspension system adopts the McPherson suspension which is more common in the market. It usually consists of two basic parts: the strut damper and the A-shaped arm, which is a commonly used configuration of the front suspension in cars under $200,000. The choice of suspension configuration and performance specifications will affect the dynamic performance of the car. These criteria are mainly reflected in the three aspects of vehicle ride i.e. road handling, steering stability and ride quality.Special attention should be paid to the structure selection and parameter setting of the car suspension. Choosing a suitable suspension for the car can reduce the difficulty of car manufacturing and save manufacturing costs while ensuring the performance of the car. The MacPherson suspension is adapted to the needs of such research and development. Relatively speaking, its structure is simple. The biggest benefit of this system is that the weight is relatively light, and the volume is relatively small, which is very suitable for the front-wheel drive model. This is because the engine part and the gearbox are installed in the front part, leaving little space for the suspension. This advantage of McPherson has been exploited by the most car manufacturers when developing such models. But I have to admit that the MacPherson suspension also have certain disadvantages. Because the lateral force does not have much support, the vehicle cannot control the roll well when turning, and it is more sturdy. However, the only way to solve this issue while keeping the cost in control is to use optimization methods for the the optimal design of MacPherson suspension.

1.2 Status of International Research:
In the foreign automotive industry, the McPherson suspension is universally used as a front suspension. Many foreign researchers have made great contributions to the design and optimization of the MacPherson suspension.
D. Colombo.[1] et al. analyzed an invalid form of the McPherson front suspension, and the final result showed that the failure of the upper strut installation caused the failure. This failure mode was present in the previous McPherson. In the article, the experimental and numerical analysis of the component is performed to obtain the service life of the component. According to the authors if their proposed design is followed, the similar situation can be avoided.
The roll steering problem should also be avoided in the McPherson suspension design. In order to minimize the roll steering, in 2008 Hosein Habibi [2] et al., based on the genetic algorithm optimization method for kinematics analysis obtained the most suitable suspension length and suspension mounting orientation to reduce the change of toe angle, camber angle and caster angle in the dynamic process, hence optimizing the dynamics performance of MacPherson suspension in motion.
The MacPherson suspension is generally used as the front suspension of the car, which necessitates that its performance must be combined with the steering, so the design of the MacPherson suspension also has to make some compromises for the steering mechanism. Daniel A [3], et al. have addressed this using 3D simulation and analysis. Using the function method , the output result is obtained from the input parameters, and an optimized McPherson suspension model is obtained.
Hee G. [4] designed and analyzed the McPherson suspension system model, and used the constraint equations of velocity, displacement and acceleration to obtain the best sensitivity factor, and verified the early design of the McPherson suspension. The validity of the theoretical hypothesis also expresses the three stages of processing of the McPherson suspension design.
Qinwen Yang [5] and so on optimized the vehicle suspension system, using the adaptive model to find the best suspension point, the process of each iteration parameter is automatic, and using the weighting factor calculation, which makes the result effective. This paper also obtained an optimized performance of the MacPherson suspension system by optimizing the design.
S Para; A Kuranowski [6] proposed a method for determining the range of ball joint rotation capabilities used in the passenger car's MacPherson suspension. The portable measuring arm is used to measure the suspension geometry of some vehicles and the geometry of the suspension components. Based on the initial measurement data, a simulation model is used to estimate the actual geometric parameters of the attachment points on the suspension and the chassis. The top mounting motion of the damper module and the stiffness characteristics of the control arm bushing allow for the simulation of the range of motion of the ball joint due to suspension motion under external loads. These loads may be caused by collision or turning motion. By using the FEM software, the rotation ability of the ball joint and its applied load can be input for further stiffness analysis.
Jingjun Zhang [7] established a virtual prototype model of the McPherson front suspension, which was simulated in ADAMS / Car and based on multi-body system dynamics and parallel wheel travel simulation. After using ADAMS / Insight to analyze the sensitivity and multi-iteration optimization of the suspension design factor, the design factor parameters that have a great influence on the sensitivity of the optimization target are found under the optimization constraints. By optimizing the design factor parameters, the problem of suspension positioning parameter optimization can be better solved.

1.3 Status of domestic research:
In "McPherson Suspension Simulation Analysis", Mao Jinming [8] has researched and found that the computer hardware, processing power, simulation software and optimization analysis technology have also been advanced a lot over the course of history. The new McPherson suspension simulation analysis approach facilitates the development of such components.
In 2009, Chen Yongyao of Zhejiang University [9] used UG and ADAMS to explore the relationship between McPherson suspension parameters and vehicle ride comfort. Through software modeling and simulation analysis of the whole vehicle, the optimized model was obtained. The parameters obtained from this model have also become the original reference data for the McPherson suspension design.
Liao Licheng [10]'s "Krafting Simulation and Optimization Design of MacPherson Suspension Based on Multi-body System Dynamics" is based on the front suspension of minibuses. In order to solve the problem of severe wear of tires, ADAMS are used. By changing the wheel positioning parameters and reducing the roll, the related problems are solved and the steering stability of the vehicle is improved.
In April 2010, Wang Chaoyang [11] introduced his own ADAMS-based EVMS front suspension design and optimization in his graduation thesis. He not only introduced the development of electric vehicles, but also introduced the McPherson suspension in more detail. The design and optimization results of electric vehicles based on traditional cars, in the face of the parameter matching problem of the Jinan BY-2 electric vehicle after modification, the shape and parameters of the MacPherson suspension components must be redesigned to make the wheat The Ferson suspension has excellent performance and excellent fatigue life in electric vehicles. Comparing the results of the optimization of the positioning parameters, it is verified that the optimization theory is correct.
Xia Changgao [12] et al. in the "Kevson Suspension Kinematics Analysis and Structural Parameter Optimization" pointed out that the genetic algorithm has certain advantages as compared to the traditional optimization algorithm, if the genetic algorithm is used to the structural parameters of the MacPherson suspension one can get the overall optimal solution.
In 2011, Jing Lixin [13] of the State Key Laboratory of Dynamic Simulation of Automobile Vehicles of Jilin University studied the lateral force of the damper of the MacPherson suspension, so the lateral force will affect the performance of the suspension. To this end, they establish the spring flexible body and use the multi-body dynamics software to obtain the force between the spring seat and the spring, which can provide simulation means for optimizing the research of the lateral force of the damper, and the optimization efficiency is improved. .
Yu Lianghao [14] et al., in the calculation of the lateral force of the MacPherson suspension damper based on the space structure, through the study of the MacPherson suspension, the suspension structure is simplified first, and the space structure and suspension are utilized.The force theory calculates the lateral force, and finally uses EXCEL to get the layout of the optimized lateral force.
Geng Xuexiao[15] et al. performed optimization of the system damping matching problem of the McPherson suspension, using the performance frequency domain analysis method to analyze the suspension performance, using the MATLAB software to obtain the Bode diagram, and changing the suspension structure parameters to obtain the suspension. The performance and overall performance of the car and comfort, get the best damping ratio.
Torque steering has an impact on the predecessor models that use the MacPherson suspension, especially as the engine torque of the front-drive models is getting bigger and bigger, and the problem is becoming more and more prominent. Li Jincan [16] studied the causes of the torque steering and the impact on the performance of the suspension, and reached his own conclusions, which has great enlightenment for the future Ramp;D personnel.
Zhu Gexiao [17] Yu used the CATIA and ADAMS software to analyze the motion performance of the MacPherson suspension in the "CATIA/ADAMS based McPherson suspension motion analysis". He built a three-dimensional model in CATIA and carried out simulation in ADAMS.This method is more accurate and can save more time and cost.
Shao Zhaohui [18] in the "Three-dimensional design and motion analysis of the car MacPherson suspension",used the pre-Muffled suspension system of a car as a reference object, using PRO/E software to establish a three-dimensional model of MacPherson suspension.The simulation software ADAMS has been used to perform kinematics simulation analysis on the MacPherson suspension model,analyzing the variation characteristics of the McPherson suspension wheel positioning parameters with the ups and downs of the wheel and finding out the problems in the suspension system. A series of experimental designs further analyzed the effects of improvements in certain critical hard points in the suspension structure on wheel positioning parameters. Based on the above research, the key hard point coordinates of the established MacPherson suspension model are optimized and analyzed, and the optimized hard point coordinates are obtained, which solves the existing problems.
Xu Chengyin [19] in the ADAMS-based vehicle front suspension simulation analysis and optimization [" to analyze the McPherson suspension structure in detail, obtain the parameters of each component of the suspension, create a virtual prototype based on ADAMS/CAR. The McPherson front suspension model and test bench are used to simulate the two-wheel synchronous runout excitation test, and the ADAMS/PostProcessor module is used to draw the curve of the wheel positioning parameters. Through detailed and in-depth analysis of the positioning parameter change curve, the inadequacies of the built suspension model have been found and addressed for the preparation for further optimization of the suspension. Finally, the virtual simulation model is optimized by using the ADAMS/CAR Insight module. The suspension guiding mechanism is designed and tested to find out the test factors that have a great influence on the wheel positioning parameters. These test factors are used as design variables and finally suspended. The guiding mechanism of the frame is optimized.
Qian Nijun [20] carried out an analysis of the dynamic characteristics and fatigue life of the suspension system with a model of the McPherson suspension system. The main contents include: (1) the quality of the finished vehicle, Axle load mass, height of the center of gravity, coil spring stiffness, tire stiffness, damping and damper resistance as a function of displacement; (2) The MacPherson suspension system dynamics model was established in ADAMS/Car. Through simulation, the influence of front wheel positioning parameters and several other important parameters on the dynamic performance of the suspension system is analyzed, and the parameters are optimized to meet the requirements of suspension and vehicle design: (3) combined with three-dimensional modeling software UG, finite element analysis software PATRAN/NASTRAN and dynamics simulation software ADAMS/VIEW completed the establishment of the rigid body model of the MacPherson suspension system and the flexible body model of the hem arm. On this basis, the rigid coupling model of the MacPherson suspension system is established and the dynamic simulation is successfully carried out. (4) The fatigue life prediction of the MacPherson suspension system is predicted by the fatigue life analysis software MSC Fatigue. The influence of the swing arm material and the roughness of the surface of the swing arm on the fatigue life can be evaluated, which can provide guidelines for the suspension swing arm design and fatigue life prediction.

2. 研究的基本内容与方案

2.Research basic content and technical solutions

2.1 Basic content:

2.1.1. Structure selection (structure form analysis and scheme selection) of the McPherson suspension in the front of the Dongfeng logo 308.

2.1.2. Design and calculation of the McPherson suspension in front of the Dongfeng Peugeot 308 car (determination of the main parameters of the MacPherson suspension).

(1) Design of coil spring: selection of spring material; force and deformation of spring; calculation of spring geometric parameters; processing of calculation results.

(2) Design calculation of the stabilizer bar: the role of the stabilizer bar; the design calculation of the stabilizer bar.

(3) Design and selection of damper: selection of damper type; selection of main performance parameters; determination of main dimensions; calculation of calculation results.