Robust disturbance observer based control for multi-variable systems

A robust disturbance observer (DOB) based control method for multi-variable systems called multi-variable disturbance observer (MVDOB) is proposed. The nominal model in MVDOB is chosen to be a multi-variable linear time-invariant (LTI) one to simplify the design of outer-loop controller and to avoid the huge mismatch caused by decoupling at the same time. The low-pass filter, which is often called the Q-filter, in MVDOB is designed utilizing H∞ control theory and the robust stability of the closed-loop system is thus guaranteed. Simulations on a three-link manipulator are presented to illustrate the performance of the proposed DOB method.