Disturbance Observer Based Control for Nonlinear Systems

TLDR

This paper introduces a general framework for disturbance observer–based control of nonlinear systems, proposing a two‑stage design that separates observer synthesis from controller synthesis to enhance disturbance attenuation. The method develops a nonlinear disturbance observer for exogenous disturbances, establishes global exponential stability, and demonstrates the approach on a two‑link robotic manipulator. The composite controller achieves global exponential stability under specified conditions and satisfies a semiglobal stability criterion.

Abstract

This work presents a general framework for nonlinear systems subject to disturbances using disturbance observer based control (DOBC) techniques. A two-stage design procedure to improve disturbance attenuation ability of current linear/nonlinear controllers is proposed where the disturbance observer design is separated from the controller design. To facilitate this concept, a nonlinear disturbance observer is developed for disturbances generated by an exogenous system, and global exponential stability is established under certain condition. Furthermore, semiglobal stability condition of the composite controller consisting of a nonlinear controller and the nonlinear disturbance observer is established. The developed method is illustrated by the application to control of a two-link robotic manipulator.