Asymptotic decoupling control with active front steering and electronic differentials in four wheel steering vehicles

In this paper the integrated control of electronic differentials with active front steering is investigated in order to improve vehicle steering dynamics. An asymptotic decoupling feedback control law is presented based on a second order vehicle model which is obtained from a seventh order nonlinear model by linearization and singular perturbation. It is shown that the lateral speed dynamics and the yaw rate dynamics can be decoupled in a steady state only by feeding back of the yaw rate, and lateral velocity measurement is not required. The eigenvalues of the controlled systems can be arbitrarily placed at the given speed domain. Furthermore, to improve the transient responses, the H_∞ norm is performed with respect to the desired eigenvalues. Simulations show that the proposed controller can improve the vehicle steering dynamics since the corresponding eigenvalues can be placed to be all real at given speed domain to prevent oscillations.