The Parameterization of All Disturbance Observers for Discrete-Time Plants with Input Disturbance

Disturbance observers have been used to estimate the disturbance in the plant. Several paperson design methods of disturbance observers have been published. Recently, the parameterizationof all disturbance observers for discrete-time plants with any output disturbance was clarified. However,no paper examines the parameterization of all disturbance observers for discrete-time plants withany input disturbance. In this paper, we clarify existance conditions of a disturbance observer and ofa linear functional disturbance observer for discrete-time plants with any input disturbance. Underthese conditions, we propose parameterizations of all disturbance observers and all linear functionaldisturbance observers for discrete-time plants with any input disturbance.