Global Practical Output Tracking for a Class of Uncertain Nonlinear Systems

This paper addresses the problem of global practical output control using output feedback for a class of uncertain nonlinear systems with time-varying delay. First, a homogeneous output feedback controller is designed for a nominally uncertain system by adding power integrator technology. Then, with the help of an appropriate Lyapunov-Krasovsky functional and a reduced-order observer, using the homogeneous dominance approach and adding a power integrator method, an output feedback controller is successfully designed to ensure that all states of the closed-loop system remain constrained while simultaneously making the tracking error arbitrarily small.