Global robust output regulation for a class of nonlinear output feedback systems

This paper considers the global robust output regulation problem of nonlinear output feedback systems in the case that both exosystem and high-frequency gain sign are unknown. The unavailability of these information poses challenges in the control law design. To solve the output regulation problem, a feedback controller is proposed by integrating the internal model principle, certainty equivalence adaptive control scheme and the Nussbaum gain technique.