The global robust output regulation problem for output feedback systems with unknown exosystems was studied some years ago using the adaptive control technique. However, a critical issue concerning the convergence of an estimated parameter vector to the true parameter vector has not been addressed. In this paper, we will address this issue and show that the estimated parameter vector converges to the true parameter vector if the dimension of the internal model is minimal in certain sense.
American Control Conference 2008. Proceedings of the American Control Conference 2008 (Seattle, WA 11-13 June, 2008) p. 4827-4832