Output Regulation for Linear Minimum Phase Systems with Unknown Order Exosystem

Under the assumption that the regulation error is the only feedback signal, it is shown how to design a regulator capable of rejecting and/or tracking signals made of at most m sinusoidal terms with unknown frequencies, magnitudes and phases, for linear observable and controllable minimum phase systems. The asymptotic convergence of the tracking error to zero is guaranteed provided that an upper bound is known on the number of sinusoidal terms, even though the values of the unknown frequencies may not be recovered.