THE DYNAMIC EFFECT OF TIRE LAG ON SIMULATION YAW RATE PREDICTIONS

Two vehicle stability and control simulations, IDSFC and VDANL, are shown to have substantial discrepancies in predicted yaw rate transient response. J-turn and sinusoidal sweep steering maneuvers, at 25 and 50 miles per hour, were used to study simulated vehicle behavior. Comparisons of predicted yaw rates with experimental measurements are made in both frequency and time domains. Differing predictions for transient yaw rate are shown to be strongly influenced by differences in the tire models used in the simulations, specifically the dynamics portion of these tire models. A modified tire dynamics model, consisting of a second-order system lag in slip angle, was implemented into one of the simulations. Lagging slip angle causes all force and moment outputs to be lagged, better representing the actual physical system. Modified tire dynamics are shown to improve yaw rate predictions at handwheel frequencies above six radians per second.