Using active caster for the enhancement of vehicle handling dynamics

In this paper, an active caster mechanism has been introduced for the purpose of vehicle handling enhancement. To this end, a 9-DOF nonlinear vehicle model, consisting of steering system dynamic equations, derived by using Kane dynamics method, and Magic Formula tyre model, is used for the simulation purposes. The effect of caster angle variations on the steady state response of the vehicle, was investigated in the next step. Based on the knowledge, extracted by the mentioned approach, a fuzzy logic controller (FLC) is designed for controlling caster angle. According to the yaw rate error, between actual and desired values, and the vehicle lateral acceleration, the controller produces the required caster angle in order to reach to stable state of the vehicle. The desired vehicle dynamics motion is assumed in the form of the steady motion of the bicycle model. Also the variation of caster angle was limited in a conventional range. During some critical maneuvers, the performance of the caster angle controller was tested and compared with the uncontrolled vehicle. Simulation results show that the caster variation control has a high capability to enhance vehicle handling dynamics.