Full state tracking of a four-wheel-steering vehicle based on output tracking control strategies

In this paper, the stable full-state tracking problem of a four-wheel-steering vehicle based on the output tracking strategies are investigated. Dynamics of such vehicle is nonholonomic and pose challenging problems for control design and the stability analysis. The dynamics formulated in terms of full state tracking errors offer some properties that allow better understanding of internal and zero dynamics of the tracking error system. Sufficient conditions are derived to ensure the stability of the internal dynamics. We show that the stability of the internal dynamics is mainly guaranteed by suitably defining output function and by suitably confining the behavior of the desired trajectory. Since sufficient conditions to confine the desired trajectory behavior are rather mild, we conclude that the output tracking control laws can be applied very well to solve the full-state tracking problem of a nonholonomic four-wheel-steering vehicle.