Cornering on Uneven Roads

SUMMARY The cornering behaviour of the tyre and the vehicle on uneven roads has been studied both experimentally and theoretically. A simple pragmatic tyre model which is especially suitable to be used in vehicle simulation studies has been developed and compared with the adapted bare string tyre model. Both models show good agreement and also the models agree well with experimental results in the range of wavelengths not less than about two meters (i.e. about ten times the tyre contact length). Moreover, full vehicle simulations have been conducted in which the simple tyre model has been used and also road experiments with Volvo's experimental computer controlled suspension car where each suspension is excited to simulate road uneveness. It is concluded that a change may occur in understeer/oversteer nature on roads having short wavelength undulations through the decrease of average tyre side force. In case of undulations of rather long wavelength, the periodic variation of yaw rate appears to become rather large in contrast to the change in average yaw rate which remains relatively small.