Advanced design of disturbance observer for high performance motion control systems

Disturbance observer (DOB) based controller design is one of the most popular methods in the field of motion control. In this paper, a generalized disturbance compensation framework, named robust internal-loop compensator (RIC), is introduced and an advanced design method of DOB is proposed based on the RIC. The mixed sensitivity optimization problem, which is the main issue of DOB design, is also solved through the parameterization of DOB in the RIC framework. Different from conventional methods, the Q-filter is separated in the mixed sensitivity optimization problem and the systematic design law for the DOB is proposed. This guarantees the robustness and optimality of the DOB and enables the design for unstable plants.