Discrete Disturbance Observer Design, Analysis and Evaluation for Servo Drive Systems

Shakhin Y. Alhassan A.B. Thao N.G.M. Do T.D.
2025 Institute of Electrical and Electronics Engineers Inc.

IEEE Open Journal of Industry Applications
2025 #6 877 - 891 pp.

Although continuous-time analyzes offer valuable theoretical insights into improving robustness, they often fail to incorporate critical sampling effects and other discrete-time (DT) dynamics essential for practical implementations. Consequently, DT analyzes are required to comprehensively evaluate how various discretization approaches influence system performance and robustness in servo-drive applications. This study investigates a discrete disturbance observer (DOB) framework for servo-drive systems, examining both differentiator- and estimator-based DOB designs implemented via Euler and Tustin discretization methods. By analyzing the impact of these designs on sensitivity peaks, noise sensitivity, and disturbance rejection, the study derives design constraints for the nominal plant model and observer bandwidth using DT sensitivity analyses and the Bode integral theorem. Theoretical evaluations and experimental results consistently demonstrate that the Tustin method, particularly when applied to differentiator-based DOB, delivers better disturbance attenuation and control performance. This systematic approach not only provides practical guidelines for tuning DOB parameters, but also assists in choosing discretization techniques most suitable for optimizing practical servo drive systems in real-world applications.

differentiator-based DOB , discrete-time (DT) analyses , Disturbance observer (DOB) , estimator-based DOB , waterbed effect

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Nazarbayev University, School of Engineering and Digital Sciences, Department of Robotics, Astana, 010000, Kazakhstan
Shimane University, Division of Mechanical, Electrical and Electronic Engineering, Interdisciplinary Faculty of Science and Engineering, Matsue, 690-8504, Japan

Nazarbayev University
Shimane University

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