Global robust output regulation for output feedback systems

A fundamental limitation to the solvability of the nonlinear robust output regulation problem is the polynomial assumption imposed on the solution of the regulator equations. This assumption is due to the failure of finding an internal model to account for more complex nonlinearities than polynomials. Very recently, it was discovered that a nonlinear internal model could be constructed under some assumption much milder than the polynomial assumption. In this paper, we will show that this kind of internal 'model can be used, to solve the global robust output regulation problem for a, class of nonlinear systems in output feedback form.