Design of a disturbance observer for discrete-time linear systems

This paper presents a design method of a disturbance observer for discrete-time linear systems. In order to estimate the unknown disturbance, an augmented model is constructed by supposing the estimated disturbance to be an auxiliary state variable. The sufficient condition for the existence and convergence of the robust observer is proposed in terms of linear matrix inequality (LMI). Numerical examples are given to show the effectiveness of the proposed method.