An output regulation problem can be converted into a stabilization problem thanks to an appropriately designed internal model. In literature, the successful construction of an internal model relies on the linear observability condition of the steady state generator. This paper defines the global observability property of the steady state generator, under which the output regulation problem is solved for a more general class of systems.
American Control Conference 2008. Proceedings of the American Control Conference 2008 (Seattle, WA 11-13 June, 2008) p. 3034-3039