General-structured unknown input observers

Using the framework of the general structured observer, we present a straightforward procedure for designing an unknown input observer (UIO) for a linear system subject to unknown inputs or uncertain disturbances. Necessary and sufficient conditions in terms of the transmission zeros are provided for the existence of a full-order UIO capable of producing an asymptotic estimate of the state. Moreover, an extension of the UIO, called the extended UIO, is developed to estimate both the system state and the unknown input simultaneously. Experimental results for a DC servo motor system demonstrate the applicability of the proposed methodologies.