Global Regulation of Flexible Joint Robots With Input Saturation by Nonlinear I-PID-Type Control

• Published in: IEEE transactions on control systems technology Vol. 32; no. 6; pp. 2385 - 2393
• Main Authors: Moyron, Jeronimo, Moreno-Valenzuela, Javier, Sandoval, Jesus
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.11.2024; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Actuators; Algorithms; Asymptotic methods; Asymptotic properties; Control algorithms; Control stability; Control systems design; Controllers; Deflection; Flexible joint robot; global asymptotic stability; input saturation; Lyapunov theory; Motors; Nonlinear control; Proportional integral derivative; proportional-integral-derivative (PID) control; Regulation; Regulators; Robot control; Robots; Stability; Symmetric matrices; Vectors
• ISSN: 1063-6536; 1558-0865
• DOI: 10.1109/TCST.2024.3391129

This brief addresses the global regulation of torque-driven flexible joint robots with input constraints. It is reported a nonlinear control scheme with bounded actions that guarantees global asymptotic stability despite input saturation, matched and unmatched disturbances, and parametric uncertainties. The control system has a double loop in a cascade configuration, where the outer loop has an integral (I) action driven by the joint deflection error. In addition, the inner loop has a nonlinear proportional-integral-derivative (PID-type) structure. Hence, an I-PID-type controller is obtained. The design methodology is based on a linear change of coordinates of the joint deflection and motor errors that allows the conclusion of global asymptotic stability via Lyapunov theory and the Barbashin-Krasovskii theorem. Sufficient conditions are explicitly stated and given in the form of matrix inequalities. Real-time experiments on a two-degrees-of-freedom flexible joint manipulator confirm the viability of the proposed controller, which exhibits better performance than the other two control algorithms.