Multi-Objective Optimization And Analysis Of Multi-link Suspension System

The suspension is the general term of the connecting device between the vehicle's frame and axle or wheels. In the process of the car, the wheel alignment parameters (the toe angle, the camber angel, the caster angle and the kinpin inclinnation) and the wheel track will be changed. The application of the multi-link suspension in intermediate and senior passenger vehicle is becoming more and more extensive. Multi-link suspension through various link distribution and constraints angle design of the connecting points with the movement,makes it possible that when suspension contracts it will take the initiative to adjust the wheel alignment, but also the great design freedom,and it is completely possible for the match and adjust against the diffirent models. The difference between the multi-link suspension and other kinds of suspension were characterized by that the muliti-link suspension has on real kinpin axis. The kinpin axis which was presented in the form of imaginary kingpin axis has brought enormous design flexibility. Therefore, the space of optimization is very large.According to the independent premium car's front suspension system structure and related data of Hunan University's'zhongqi plan', the mathematic model of the multi-link suspension was built in the software of Matlab using the attitude coordinate transformation technology of the spatial kinematics. The imaginary kingpin axis of the multi-link suspension was established basing on the instant screw axis method. The kinematics curve of the wheel alignment parameters was given in Matlab.The kinematic simulation model for the front multi-link suspension was developed using ADAMS/CAR module. The simulation results which were matched well between the mathematic model and the kinematic simulation model proved the reliability of the two models.On the basis of former, NSGA-Ⅱprogram for multi-link suspension was written by using Matlab. Combined with the NSGA-Ⅱalgorithm, the multi-objective optimization of the wheel alignment parameters which include the toe angle, the camber angel, and the caster angle was done. Therefore, the Pareto optimization solution set of three goals were obtained. Choosing one group of the data in the Pareto set, the comparative analysis between the mathematic model and the kinematic simulation model was attained. The results show the design method is a practical tool for the optimization design of the multi-link suspension.