Vehicle Handling Responses Using Stability Derivatives

Linearized three degree-of-freedom equations for the handling responses of an automobile are derived using the concept of stability derivatives so that steer and camber compliances can be included. Resulting calculations apply when lateral accelerations are less than about 0.35 g, but high enough so that on-center nonlinearities are unimportant. Calculations are compared with measurements on a small front-drive car for the following steady-state parameters: understeer gradient; steering sensitivity, and roll and sideslip gradients. Comparisons are also presented between calculated and measured step-steer transients and summary comparisons are given for response time and percent overshoot Differences between calculated and measured responses are explained.