The Optimal Design Of Suspension For A School Bus Based On Multi-Approximation Model

Handling stability is regarded as the main index that used to evaluate handling performance of vehicle, which determines driving safety to a great extent. As the main connection system between bridge and frame, suspension system determines vehicle's handling performance, and its' motion character largely depends on the position of hard points. In order to promote the handling performance of vehicle, it 's essential to optimize suspension's design parameters to reasonable scope.Based on the front double wishbone indepe ndent suspension with torsion bar spring of a school bus, the author carries out a lot of research work. The multi-objective particle swarm optimization(MOPSO) is employed to optimize this suspension, the main work includes:(1) Carrying out theoretical research and finding out reasons that caused tire wear seriously and poor handling stability, providing theoretical guidance for the optimization of suspension in the next work;(2) In order to improve vehicle's handling performance and reduce tire wear, reasonable optimization of suspension's design parameters are carried out. Firstly, design parameters of suspension that affect vehicle 's handling performance mostly are selected as objectives to optimize. In this paper, three parameters are selected as objectives, including the range of toe angle ?camber angle and wheel track. Through the analysis of sensitivity, factors that impact objectives most are chosen as design variables. Multiple approximation models, such as kriging model and the quadratic polynomial response surface model are implemented to construct the objective function, the accuracy of approximation models are calculated and the more accurate one is selected to be optimized by multi-objective particle swarm optimization. At last, the required hard point coordinates of suspension are gained and the vehicle 's handling performance is improved.(3) According to the requirements of vehicle' s general arrangement, the suspension's torsion bar spring can be placed up?down or design into the form of double torsion bar to meet the needs of large tonnage. As for the suspension's torsion bar, different style of installation determines different calculation of liner stiffness of suspension and have different impact on th e change of suspension's design parameters. Based on different kinds of torsion bar spring 's installation, the liner stiffness of suspension is calculated respectively and the change of suspension 's design parameters are compared in the process of driving.Applying the method described in this article, the author succeeded in solving the problems of suspension design. This article provides a selectable technical method that can be used to design our nation 's special school bus. It has great research value and practice meaning to combine the basic theory of vehicle design and engineering practice of suspension's optimal design to cater the need of production.