Robust Global Practical Output Tracking of Uncertain Nonlinear Systems by Smooth Output Feedback

This paper considers a robust global practical output tracking problem for a family of uncertain nonlinear systems with uncontrollable and unobservable linearization. It is shown that under some mild conditions on such a system there is a smooth output feedback achieving global practical output tracking and such a smooth output controller is explicitly constructed by a new design method proposed. The design of smooth output feedback controllers does not require the precise information of the uncertain system and depends only on the knowledge of the bounding system. The usefulness of our result is illustrated by a numerical example.