Symplectic Discrete-Time Control of Flexible-Joint Robots: Experiments with Two Links⁎This paper was not presented at any IFAC meeting. Issue 19 (2021)

• Record Type: Journal Article
• Authors: Thoma, Tobias; Wu, Xuwei; Dietrich, Alexander; Kotyczka, Paul
• Is Part Of: IFAC-PapersOnLine. Volume 54:Issue 19(2021)
• Page Start: 1
• Page End: 7
• Publication Date: 2021
• Subjects: Sampled-data systems -- discrete-time control -- symplectic integration -- nonlinear mechanical systems -- flexible-joint robots -- serial elastic actuators -- KUKA LWR; Automatic control -- Periodicals; 629.805
• DOI: 10.1016/j.ifacol.2021.11.046
• Languages: English
• ISSNs: 2405-8963

Abstract

Abstract: We present the application and experimental validation of discrete-time control implementation based on symplectic integration - in short referred to as symplectic discrete-time control - to a serial robot manipulator with flexible-joints. Applying the implicit midpoint rule as a simple and popular symplectic integration scheme to both the model of the sampled system and the desired target dynamics, yields a discrete-time control law with the same structure as in continuous time. The arguments are, however, predicted stage values on the subsequent sampling interval resulting from a half implicit Euler step for the target system. The approach can be easily extended to a purely position-based feedback law. The experimental validation on a lightweight robot (KUKA LWR IV+) confirms the expected improvements at low sampling rates, with an increase in the assignable closed-loop stiffness of up to 29 %.