Structural Equivalence between Minimum-order and Inverse-model-based Disturbance Observers

Abstract

This paper considers strictly proper SISO systems that may have zeros and derives the input-output representation of a minimal-order disturbance observer (DOB) under the assumption of constant disturbances. Furthermore, it is shown that the obtained representation is structurally equivalent to an inverse-model-based DOB with a specific filter, and an interpretation of this equivalence for systems with unstable zeros is provided.