Global robust output regulation for Lur'e systems

In this paper, we consider the global output regulation problem for systems with an output depending nonlinearity. If the system model is known and the corresponding regulator equations are solvable, an observer-based controller solving the global output regulation problem is presented. Sufficient conditions for the existence of such a controller are formulated in terms of an LMI. If the system parameters are not exactly known and the nonlinearity can vary over a given class, we show that there exists a robust controller provided that the robust output regulation problem for the system without the nonlinearity is solvable and that there exists a suboptimal solution to a certain H_inf optimization problem