This paper investigates the effects of tire cornering stiffness on vehicle frequency responses. The high speed force and moment test data of four different groups of tires were collected. These tires had different constructions and wide ranges of cornering stiffness. The tire nonlinear lateral force and aligning moment were modeled using the Pacejka Magic Formula tire model. Based on a full nonlinear vehicle model, vehicle linear handling performance was simulated with the tires during pulse steer and step steer manoeuvres. The following vehicle dynamic parameters were selected in order to evaluate the vehicle linear handling performance: (a) sideslip angle; (b) yaw rate peak time; (c) phase lags of yaw rate and lateral acceleration; (d) yaw rate gain; (e) yaw damping ratio; and (f) natural frequency. The sideslip angle and yaw rate peak time were obtained from the vehicle responses to a step steer input. The other parameters were derived by fitting the frequency response functions of yaw rate and lateral acceleration during a pulse manoeuvre to a two degrees of freedom linear "bicycle model". Two main conclusions drawn from this preliminary study are: (1) higher tire cornering stiffness results in better vehicle linear handling performance; and (2) different methods of evaluation give similar rating of the tires. (A)
Abstract