Yet Another Tutorial of Disturbance Observer: Robust Stabilization and Recovery of Nominal Performance

TL;DR

This paper provides a tutorial review of disturbance observers (DOBs), explaining their role in robust stabilization and performance recovery for uncertain plants, with insights into their analysis, limitations, and extensions.

Contribution

It offers a new perspective on conventional DOBs, discussing their restrictions and potential extensions for improved robustness.

Findings

DOB can make uncertain plants behave like nominal systems in transient and steady-state.

Large Q-filter bandwidth enhances disturbance rejection and robustness.

The paper clarifies the theoretical basis and practical implications of DOB design.

Abstract

This paper presents a tutorial-style review on the recent results about the disturbance observer (DOB) in view of robust stabilization and recovery of the nominal performance. The analysis is based on the case when the bandwidth of Q-filter is large, and it is explained in a pedagogical manner that, even in the presence of plant uncertainties and disturbances, the behavior of real uncertain plant can be made almost similar to that of disturbance-free nominal system both in the transient and in the steady-state. The conventional DOB is interpreted in a new perspective, and its restrictions and extensions are discussed.