Adaptive Lane Keeping Controller for Four-Wheel-Steering Vehicles

In n-input n-output systems such as x(t) = Ax(t) + Bu(t), x(t) isin Rⁿ, let the driving matrix B be described as B = QK where Q is a positive definite matrix and K is a diagonal positive definite matrix. Then, it can be shown that a stable adaptive controller can be easily designed. Based on the fact, we propose a new adaptive lane keeping controller with front and rear wheel steering. First of all, a method to estimate unknown curvatures of target lanes is shown. The estimator doesn´t require lateral velocity of vehicles. Next, we show a method to design ideal transient trajectories for relative lateral distance and relative yaw angle between vehicles and target lanes, and then, an adaptive steering controller is developed. The developed controller doesn´t require the measurement of lateral velocity of vehicles, the accurate knowledge of vehicle parameters and road curvatures. Moreover, it is shown that good robust lane tracking performance can be easily achieved by setting only one design parameter.