Disturbance Rejection for a Class of Nonlinear Systems with Input Time-delay

Disturbance-observer-based control (DOBC) has been considered as a robust control scheme against the various unknown disturbances in many applications The existing DOBC methods were only applicable for the case where disturbances satisfy time matching condition, i.e., they enter the system in the same time as the control inputs. By appropriately designing a auxiliary observer, the disturbance of future time is predicted after appropriate coordinate transformation, new disturbance estimation and rejection law are designed in this paper. One novel feature of the proposed method is that the merits of DOBC can be inherited for a class of nonlinear systems with input time-delay. By integrating the disturbance observers with conventional robust control laws, the disturbances can be rejected and the desired dynamic performances can be guaranteed. Simulations demonstrate the advantages of the proposed scheme.