IEEE_TIE25: Analysis and Synthesis of DOb-based Robust Motion Controllers

TL;DR

This paper introduces a unified framework for analyzing and synthesizing digital disturbance observers (DObs) in motion control, improving robustness and stability through advanced design and validation.

Contribution

It presents a systematic design method for both conventional and high-order DObs, including stability analysis and practical synthesis tools validated experimentally.

Findings

DObs are stable with bounded estimation error under disturbances

High-performance DObs improve disturbance estimation accuracy

Experimental results confirm the effectiveness of the proposed methods

Abstract

By employing a unified state-space design framework, this paper proposes a novel systematic analysis and synthesis method that facilitates the implementation of both conventional zero-order (ZO) and high-order (HO) DObs. Furthermore, this design method supports the development of advanced DObs (e.g., the proposed High-Performance (HP) DOb in this paper), enabling more accurate disturbance estimation and, consequently, enhancing the robust stability and performance of motion control systems. Lyapunov direct method is employed in the discrete-time domain to analyse the stability of the proposed digital robust motion controllers. The analysis demonstrates that the proposed DObs are stable in the sense that the estimation error is uniformly ultimately bounded when subjected to bounded disturbances. Additionally, they are proven to be asymptotically stable under specific disturbance conditions, such as constant disturbances for the ZO and HP DObs. Stability constraints on the design parameters of the DObs are analytically derived, providing effective synthesis tools for the implementation of the digital robust motion controllers. The discrete-time analysis facilitates the derivation of more practical design constraints. The proposed analysis and synthesis methods have been rigorously validated through experimental evaluations, confirming their effectiveness.