The fundamental understeer/oversteer signature of a vehicle has historically been evaluated through steady state circular skid pad testing done according to one of the four methodologies outlined in SAE J266. These tests evaluate a vehicle's fundamental handling behavior but are insufficient to fully establish its yaw stability and control characteristics and performance envelope. Transient testing of the vehicle is also necessary because vehicles are not operated under steady state conditions. This becomes of greatest importance in an emergency situation where a driver must respond quickly. For good handling and control, it is necessary for a vehicle to understeer in circular skid pad testing. Additionally, the vehicle must not become yaw-unstable in a J-turn. In the present work, full-scale handling tests were conducted on a 15-passenger van configured in a variety of loading and design conditions. The test results showed substantial differences in vehicle performance when comparing steady state tests (constant radius tests per SAE J266) and transient tests (J-turns). The tests revealed some undesirable handling characteristics during the transient maneuvers that were not uncovered by steady state tests alone. Design changes were tested and found to substantially improve the dynamic handling characteristics of the vehicle. For the covering abstract see ITRD E825082.
Abstract