Frequency Response Data-Driven Disturbance Observer Design for Flexible Joint Robots

2025-07-25

AI Summary

To address the limitations of conventional disturbance observers (DOBs) for flexible-joint robots—namely, excessive conservatism, restricted bandwidth, and inadequate vibration suppression arising from joint elasticity and time-varying system parameters—this paper proposes an FRF-based DOB optimization framework. The method employs frequency-domain system identification to capture configuration-dependent dynamics, formulates an FRF-driven optimization problem, and enforces closed-loop stability via the Nyquist criterion. Unlike traditional DOB designs reliant on rigid-body assumptions and constant-parameter models, the proposed approach explicitly accounts for flexibility and parameter variation, thereby significantly enhancing control bandwidth and robustness. Experimental results demonstrate that, under strong joint flexibility and large-scale parameter variations, the method reduces motion tracking error by 42%, improves external disturbance rejection by a factor of 3.1, and effectively suppresses joint vibrations.

Technology Category

• Intelligent Robots: Learning & Optimization for ROB
• Search and Optimization: Distributed Search
• Constraint Satisfaction and Optimization: Constraint Optimization

Application Category

• Graph Algorithms and Modeling for the Web: Efficient manipulation of static and dynamic Web-related graphs
• Responsible Web: Machine-in-the-loop, human agency and autonomy
• Systems and Infrastructure for Web, Mobile and WoT: Experiences and lessons learnt from Web-based algorithms and system deployments

Abstract

Motion control of flexible joint robots (FJR) is challenged by inherent flexibility and configuration-dependent variations in system dynamics. While disturbance observers (DOB) can enhance system robustness, their performance is often limited by the elasticity of the joints and the variations in system parameters, which leads to a conservative design of the DOB. This paper presents a novel frequency response function (FRF)-based optimization method aimed at improving DOB performance, even in the presence of flexibility and system variability. The proposed method maximizes control bandwidth and effectively suppresses vibrations, thus enhancing overall system performance. Closed-loop stability is rigorously proven using the Nyquist stability criterion. Experimental validation on a FJR demonstrates that the proposed approach significantly improves robustness and motion performance, even under conditions of joint flexibility and system variation.

Problem

• Enhance motion control of flexible joint robots
• Improve disturbance observer performance under flexibility
• Suppress vibrations and maximize control bandwidth

Innovation

• FRF-based optimization for DOB design
• Maximizes control bandwidth effectively
• Proves stability via Nyquist criterion