Mathematical optimisation of the suspension system of an off-road vehicle for ride comfort and handling

Abstract

This study aims to evaluate the use of mathematical optimisation algorithms for the optimisation of a vehicle’s spring and damper characteristics, with respect to ride comfort and handling. Traditionally the design of a vehicle’s suspension spring and damper characteristics are determined by a few simple planar model calculations, followed by extensive trial-and-error simulation or track testing. With the current advanced multi-body dynamics computer software packages available to the design engineer, the integration of traditional mathematical optimisation techniques with these packages, can lead to much faster product development. This, in turn results in a reduction of development costs. A sports utility vehicle is modelled by means of a general-purpose computer programme for the dynamic analysis of a multi-body mechanical system. This model is validated against measurements from road tests. The mathematical model is coupled to two gradient-based mathematical optimisation algorithms. The performance of the recently proposed Dynamic-Q optimisation algorithm, is compared with that of the industry-standard gradient based Sequential Quadratic Programming method. The use of different finite difference approximations for the gradient vector evaluation is also investigated. The results of this study indicate that gradient-based mathematical optimisation methods may indeed be successfully integrated with a multi-body dynamics analysis computer program for the optimisation of a vehicle’s suspension system. The results in a significant improvement in the ride comfort as well as handling of the vehicle.