Extended Disturbance Observer for Nonlinear Systems based on Sliding-Mode Theory

Model mismatch and external disturbances is wildly existed in control practice of nonlinear systems, which badly influenced the control effect. To handle such a situation, we proposed a sliding-mode based extended disturbance observer (SMEDO) in this paper. The brief idea is to combine a traditional nonlinear extended disturbance observer with the principle of sliding-mode. By well-designed sliding mode surface, the robustness of modified disturbance observer can be enhanced. The stability proof and the principle of the parameter design of modified observer are also given. Finally the performance of traditional NDOB, EDOB and proposed SMEDOB is compared. Simulations reveal that the proposed method has higher estimation precision, speed, and stronger robustness.