Robust two degree of freedom vehicle steering control satisfying mixed sensitivity constraint

Robust steering control is used here for improving the yaw dynamics of a passenger car. A specific two degree of freedom control structure is adapted to the vehicle yaw dynamics problem and shown to robustly improve performance. The design study is based on six operating conditions for vehicle speed and the coefficient of friction between the tires and the road representing the operating domain of the vehicle. The relevant design specifications are formulated as attaining Hurwitz stability and a mixed sensitivity frequency domain bound. Simple, and therefore, easily implementable controller transfer functions with two design parameters are chosen for the two steering controller degrees of freedom. Using the parameter space method, the design specifications are mapped into the plane of controller parameters. The effectiveness of the final design is demonstrated using simulations.