Analysis and design of H∞ robust disturbance observer based on LMI

Disturbance observer (DOB)-based controller design is one of the most popular methods in the field of motion control. This paper presents a design method for the disturbance observers to satisfy closed loop performance specifications, provided that the main feedback controller is known. Unlike the conventional methods, the proposed DOB design method takes into account the influence from not only disturbance and noise but also model uncertainty to the systempsilas stability and performance. Utilizing the LMI method, the H_infin optimal disturbance observer can be obtained by solving a series of convex optimization problems. Furthermore, by introducing the weighted transfer functions, the proposed method can guarantee the robust stability as well as robust performance of the system.