Disturbance Observer

TL;DR

This paper explains how disturbance observers work, their design conditions for robustness, and how they improve system stability and performance under uncertainties and disturbances.

Contribution

It provides a detailed analysis of disturbance observer design principles to ensure robust stability and performance in uncertain environments.

Findings

Disturbance observers can effectively reject external disturbances.

Proper design guarantees robustness and stability.

The approach improves transient and steady-state performance.

Abstract

Disturbance observer is an inner-loop output-feedback controller whose role is to reject external disturbances and to make the outer-loop baseline controller robust against plant's uncertainties. Therefore, the closed-loop system with the DOB approximates the nominal closed-loop by the baseline controller and the nominal plant model with no disturbances. This article presents how the disturbance observer works under what conditions, and how one can design a disturbance observer to guarantee robust stability and to recover the nominal performance not only in the steady-state but also for the transient response under large uncertainty and disturbance.