  In this paper, we study the event-triggered global robust practical output
regulation problem for a class of nonlinear systems in output feedback form
with any relative degree. Our approach consists of the following three steps.
First, we design an internal model and an observer to form the so-called
extended augmented system. Second, we convert the original problem into the
event-triggered global robust practical stabilization problem of the extended
augmented system. Third, we design an output-based event-triggered control law
and a Zeno-free output-based event-triggered mechanism to solve the
stabilization problem, which in turn leads to the solvability of the original
problem. Finally, we apply our main result to the tracking problem of the
controlled hyper-chaotic Lorenz systems.
