| Many vehicle dynamic research efforts in the last ten years have been concentrated in two important areas: traction/braking control and four wheel steering. No attempt has been carried out to combine these interdependence aspects of vehicle controls and investigate the potential benefits of integrated torque/braking and steering controls. In this study it is proposed that an integrated torque and steering control can significantly improve the safety and performance of the automobile. The proposed automobile possesses the hardware necessary to control the torque at each wheel and to augment the steering a small amount from a normally commanded steer angle.; A model of the vehicle was developed including complex tire dynamics and normal force variations due to weight shifts during vehicle maneuvers. This model is then linearized to determine whether modern control theory can be beneficial. Since the linearized model does not contain the nonlinearities of actual vehicle system the controller designed from this model must be robust, that is it must be able to handle external disturbances, parameter variations, and system nonlinearities. The Reverse Frame Normalization Controller Design Method was chosen since its designed controllers are very robust. The bandwidth of the control is realistically limited. Controllers are developed for integrated torque and steering with primary intent of providing prescribed vehicle handling characteristics. Only realistic measurements are hypothesized. The results indicate that significant improvements are possible over conventional front wheel, rear wheel, and all wheel drive, especially over poor road conditions. |
