An optimal approach to non-linear control of vehicle yaw dynamics

Direct yaw moment control (DYC) is a recent active safety method introduced to control vehicle handling dynamics in non-linear regimes. The external yaw moment is considered as an important control input for DYC, which should be kept as low as possible. In the current paper, to achieve this aim, an optimal yaw rate tracking law is developed for DYC by the response prediction of a continuous non-linear vehicle dynamics model. A linear yaw rate model limited by tyre/road conditions is proposed as a desired model to be tracked by the controller. The derived control law is evaluated and its main features are discussed. The performed analysis gives an insight into the regulation of free parameters of the control law to make a compromise between tracking accuracy and control energy. The effectiveness of the designed controller is compared with a sliding mode controller, reported in literature, through simulations of various manoeuvres using a developed non-linear full vehicle dynamics model. The simulation results indicate that a satisfactory handling performance through a reduced external yaw moment can be achieved when the proposed optimal controller is engaged with the model.