Output Regulation and Active Disturbance Rejection Control: Unified Formulation and Comparison

Abstract

Output regulation theory aims to design a controller for achieving reference tracking and disturbance rejection while maintaining system stability. Different from the stabilization problem about an equilibrium point, the output regulation problem is capable of characterizing more complicated steady-state trajectories induced by reference and/or disturbance. Many efforts have been made to reveal how a steady-state trajectory can be characterized, estimated, and hence compensated by a controller such that output regulation can be asymptotically achieved. When the steady-state trajectory is approximately treated as a constant “quantity”, the standard output regulation implies an approximate version within which output regulation is practically achieved. It is revealed in this paper that such an approximate version of output regulation includes the later developed active disturbance rejection control (ADRC) method as a special case.