A Finite-Time Disturbance Observer for Tracking Control of Nonlinear Systems Subject to Model Uncertainties and Disturbances

Manh Hung Nguyen and Kyoung Kwan Ahn ()
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Manh Hung Nguyen: Institute of Control Engineering, Le Quy Don Technical University, 236 Hoang Quoc Viet, Hanoi 11917, Vietnam
Kyoung Kwan Ahn: School of Mechanical and Automotive Engineering, University of Ulsan, Daehakro 93, Namgu, Ulsan 44610, Republic of Korea

Mathematics, 2024, vol. 12, issue 22, 1-16

Abstract: In this study, a finite-time disturbance observer (FTDOB) with a new structure is originally put forward for the motion tracking problem of a class of nonlinear systems subject to model uncertainties and exogenous disturbances. Compared to existing disturbance estimator designs in the literature, in which the estimation error only converges to the origin asymptotically under assumptions that the first and/or second derivatives are vanishing, the suggested DOB is able to estimate the disturbance exactly in finite time. Firstly, uncertainties (parametric and unstructured uncertainties), unknown dynamics, and external disturbances in system dynamics are lumped into a generalized disturbance term that is subsequently estimated by the proposed DOB. Based on this, a DOB-based backstepping controller is synthesized to ensure high-accuracy tracking performance under various working conditions. The stability analysis of not only the DOB but also the overall closed-loop system is theoretically confirmed by the Lyapunov stability theory. Finally, the advantages of the proposed FTDOB and the FTDOB-based controller over other DOBs and existing DOB-based controllers are explicitly simultaneously demonstrated by a series of numerical simulations on a second-order mechanical system and comparative experiments on an actual DC motor system.

Keywords: disturbance observer; finite-time convergence; tracking control; disturbances and uncertainties (search for similar items in EconPapers)
JEL-codes: C (search for similar items in EconPapers)
Date: 2024
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