LPV/Hinf controller for vehicle handling and stability enhancement

Overview & Synopsis

The intent of this article is to present a methodology that deals with steering/braking coordination task, for automotive vehicle yaw control scheme. Because of the tire nonlinearity that is mainly due to the saturation of cornering forces, vehicle handling performance is improved but limited to a certain extent only by steering control. Direct yaw moment control using braking forces is effective not only in the linear region but also in the nonlinear ranges of the tire friction circle. However, braking effect is not desirable in normal driving situations. Consequently, the maximum benefit is gained through the coordinated and combined use of both steering and braking control methods. In this study, the coordination task is achieved through a suitable gain scheduled LPV (Linear Parameter Varying) controller, where braking control is activated only when the vehicle reaches the handling limits. The controller is synthetized within the LMI framework, while ensuring linear optimal Hinf performances. Computer simulations, carried out on a complex full vehicle model subject to critical driving situations, show that the vehicle handling is much improved by the integrated control system compared against an uncontrolled vehicle.