  In this paper, the optimum linear/nonlinear spring and linear/nonlinear
damper force versus displacement and force versus velocity characteristic
functions, respectively, are determined using simple lumped parameter models of
a quarter car front independent suspension and a half car rear solid axle
suspension of a light commercial vehicle. The complexity of a nonlinear
function optimisation problem is reduced by determining the shape a priori
based on typical shapes supplied by the car manufacturer and then scaling it up
or down in the optimisation process. The vehicle ride and handling responses
are investigated considering models of increased complexity. The linear and
nonlinear optimised spring characteristics are first obtained using lower
complexity lumped parameter models. The commercial vehicle dynamics software
Carmaker is then used in the optimisation as the higher complexity, more
realistic model. The performance of the optimised suspension units are also
verified using this more realistic Carmaker model.
