Abstract:
A methodology is proposed for the efficient determination of gradient information, when
performing gradient based optimisation of an off-road vehicle’s suspension system. The methodology is
applied to a computationally expensive, non-linear vehicle model, that exhibits severe numerical noise. A
recreational off-road vehicle is modelled in MSC.ADAMS, and coupled to MATLAB for the execution of
the optimisation. The successive approximation method, Dynamic-Q, is used for the optimisation of the
spring and damper characteristics. Optimisation is performed for both ride comfort and handling. The
determination of the objective function value is performed using computationally expensive numerical
simulations.
This paper proposes a non-linear pitch-plane model, to be used for the gradient information, when
optimising ride comfort. When optimising for handling, a non-linear four wheel model, that includes roll, is
used. The gradients of the objective function and constraint functions are obtained through the use of central
finite differences, within Dynamic-Q, via numerical simulation using the proposed simplified models. The
importance of correctly scaling these simplified models is emphasised. The models are validated against
experimental results. The simplified vehicle models exhibit significantly less numerical noise than the full
vehicle simulation model, and solve in significantly less computational time.
