Design of a Nested Observer for Composite Disturbances Based on Characteristic Extraction

To address composite disturbances in the system, this paper proposes a disturbance rejection method. The considered disturbances include both regular and irregular components. First, by extracting the characteristics of the frequency components, a frequency compensation observer(FCO) is designed to fully utilize the disturbance characteristics, processing only the regular disturbances. Next, the remaining irregular components and the errors of the regular disturbances are estimated and compensated using a nonlinear extended state observer (NESO). In the proposed method, the multi-loops are independent of each other, which reduces the computational complexity to a large extend. The two types of observers form a nested structure, handling disturbances more targetedly, making the method more suitable for addressing composite disturbances in the system.Finally, the effectiveness of the proposed method is verified through simulations.