The Kinematic Characteristics Analysis And Optimization Of Five-link Suspension

The suspension is the general term of the connecting device between the vehicle’s frame and axle or wheels. In the process of the wheel up and down, the wheel alignment parameters and wheel track will be changed. The kinematic characteristics of suspension plays a vital role in full-vehicle handling stability and it also affects vehicle ride comfort performance, braking, tire wearing as well. Because of its good handling stability and ride comfort of comprehensive performance, five-link suspension get a wide range of applications in intermediate and senior vehicle. But five-link suspension bar system is complicated, the design of suspension K&C characteristics is difficult. So it is very important to study the kinematics characteristics of the five-link suspension, analyze the vehicle handling stability, and optimize the suspension structure for improving the vehicle performance. Based on the structure and related data of the rear suspension of a passenger car, this dissertation focuses on the analysis and optimization of five-link suspension kinematics characteristics and vehicle handling stability, considering the uncertainty of the suspension hard point.Firstly, from the theoretical point of view, based on the rigid body kinematics, the spatial attitude-coordinate used in mathematic model is derived. The mathematic model of the five-link suspension is established using the DOF theory. The imaginary kingpin axis of the five-link suspension is established basing on the instant screw axis method,and the kinematics curve of wheel alignment parameters is solved in Matlab. Then, the multi-body dynamics simulation model of the five-link suspension is established by ADAMS, which verifies the accuracy of the mathematical model. Based on the K&C experimental data of a variety of cars, the reasonable range of the characteristics of K&C is summarized, and the K&C characteristics of five-link suspension are evaluated.Secondly, based on the dynamic model of the five-link suspension, the vehicle dynamics simulation model is established. According to GB, the typical test of handling stability is done, and the analysis results show that the vehicle has a large space for optimization. Subsequently, fuzzy grey correlation algorithm is used to analyze the sensitivity of suspension hard points. Taking into account the uncertainty of the suspension hard point, the NSGA-II algorithm and IP-GA algorithm are used to solve the multi-objective uncertain optimization problem. At the same time, the NSGA-II algorithm is used to solve the certain optimization problem. In the optimization process, the mathematical model of the five-link suspension is used, which not only ensures the accuracy of the model, but also avoids the repeated calls of the ADAMS multi-body dynamics model, and then improve the efficiency of optimization. After optimization, the vehicle handling stability is improved, but compared with certain optimization, the uncertain optimization has better robustness.