Influence of ride motions on the handling behaviour of a passenger vehicle

Abstract

A vehicle model was developed for the investigation of the influence of ride motions on handling dynamics of passenger vehicles. The inputs to the vehicle model are the steering wheel angle and a road profile at each wheel. The outputs were first compared with the results of independent handling and ride models, and good agreement was shown to exist. The combined motion of the vehicle was investigated by the application of step steering wheel angle inputs while travelling on a rough road surface. It was seen that the cornering ability at low and moderate levels of lateral acceleration on the roads with moderate roughness was similar to that on the smooth road, but larger body side-slip angles and tyre slip angles occurred over the rough road surfaces for similar steering inputs. The maximum achievable lateral acceleration was reduced on roads with moderate roughness owing to the earlier saturation of tyre slip angles compared with those on smooth roads. Over very rough roads and at high lateral accelerations, because of the large fluctuations of normal loads and the rapid drop in available lateral force, the body side-slip angle dramatically increased, which led to instability characterized by the oversteering behaviour. At high lateral accelerations close to the limit, the vehicle that understeered over the smooth road surface exhibited oversteering behaviour over rough road surfaces.