Equivalent-Input-Disturbance-Based Dynamic Tracking Control for Soft Robots via Reduced-Order Finite-Element Models

• Published in: IEEE/ASME transactions on mechatronics Vol. 27; no. 5; pp. 4078 - 4089
• Main Authors: Li, Shijie, Kruszewski, Alexandre, Guerra, Thierry-Marie, Nguyen, Anh-Tu
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.10.2022; The Institute of Electrical and Electronics Engineers, Inc. (IEEE); Institute of Electrical and Electronics Engineers
• Subjects: Adaptation models; Algorithms; Automatic Control Engineering; Comparative studies; Computer Science; Control methods; Control systems; Dynamic control; Dynamic controllers; Dynamic stability; Equivalence; Feedback control; Feedforward control; Finite element analysis; Finite element method; finite-element model; Heuristic algorithms; Kinematics; Linear matrix inequalities; Mathematical analysis; Mathematical models; model order reduction (MOR); Model reduction; motion control; Optimization; Proper Orthogonal Decomposition; Reduced order models; Robot control; Robots; Soft robotics; soft robots; State-of-the-art reviews; Structural stability; Symmetric matrices; Tracking control; Uncertainty; uncertainty compensation
• ISSN: 1083-4435; 1941-014X
• DOI: 10.1109/TMECH.2022.3144353

This article develops a systematic framework for dynamic tracking control of soft robots. To this end, we propose a new projector for the proper orthogonal decomposition algorithm to significantly reduce the large-scale robot models, obtained from finite-element methods (FEM), while preserving their structure and stability properties. Such a property preservation enables an effective equivalent-input-disturbance-based scheme for dynamic tracking control of elastic soft robots with various geometries and materials. The proposed control scheme is composed of three key components, i.e. , feedforward control, disturbance-estimator control, and feedback control. To account for the trajectory reference, the feedforward action is designed from the dynamic FEM reduced-order robot model. The disturbance-estimator control action is obtained from an unknown input observer, which also provides the estimates of the reduced states for the feedback control design. The feedback gains of the observer-based controller are computed from an optimization problem under linear matrix inequality constraints. The closed-loop tracking properties are guaranteed using the Lyapunov stability theory. The effectiveness of the proposed dynamic control framework has been demonstrated via both high-fidelity SOFA simulations and experimental validations, performed on two soft robots with different natures. In particular, comparative studies with state-of-the-art control methods have been also carried out to highlight the interests of the new soft robot control results. This article is complemented with a video: https://bit.ly/2VVwtLn .