Multivariable bilinear vehicle control using steering and individual wheel torques

This paper is concerned with the stabilization of the lateral motion dynamics of an automobile. A planar vehicle model is used which includes yawing velocity and lateral velocity degrees of freedom. The controllable system inputs are the front and rear wheel steer angles as well the torque input at each wheel. The model presents two departures from earlier work in this field. The first of these is that the wheel torques may assume both positive or negative values, as would be the case for an electric vehicle with a motor at each of it's wheels. The second of these is the inclusion of bilinear terms involving steer angles and wheel torques in the model formulation. The bilinear terms are used to model the effect of steer angles on the effective moment arm associated with brake or drive torques applied at the relevant wheel. A state feedback controller which minimizes a quadratic performance index is developed and simulations are used to evaluate the performance of the proposed controller on a more detailed vehicle model which includes nonlinear tire characteristics.