A peg-in-hole controller for cable-driven serial robots with compliant wrist based on cable tensions and joint positions

• Published in: Assembly automation Vol. 42; no. 1; pp. 67 - 79
• Main Authors: Lou, Ya'nan, Quan, Pengkun, Lin, Haoyu, Liang, Zhuo, Wei, Dongbo, Di, Shichun
• Format: Journal Article
• Language: English
• Published: Bingley Emerald Publishing Limited 11.01.2022; Emerald Group Publishing Limited
• Subjects: Accuracy; Algorithms; Assembly; Compliance; Control algorithms; Control systems design; Controllers; Hybrid control; Modulus of elasticity; Robots; Sensors; Wrist; Automatic assembly; Peg-in-hole; Control; No F/T sensor; Compliant wrist; Cable-driven serial robot; Cable tensions; Compliant mechanisms; Robotics
• ISSN: 0144-5154; 2754-6969; 1758-4078; 2754-6977
• DOI: 10.1108/AA-04-2021-0043

Purpose This purpose of this paper is to design a peg-in-hole controller for a cable-driven serial robot with compliant wrist (CDSR-CW) using cable tensions and joint positions. The peg is connected to the robot link through a CW. It is required that the controller does not rely on any external sensors such as 6-axis wrist force/torque (F/T) sensor, and only the compliance matrix’s estimated value of the CW is known. Design/methodology/approach First, the peg-in-hole assembly system based on a CDSR-CW is analyzed. Second, a characterization algorithm using micro cable tensions and joint positions to express the elastic F/T at the CW is established. Next, under the premise of only knowing the compliance matrix’s estimate, a peg-in-hole controller based on force/position hybrid control is proposed. Findings The experiment results show that the plug contact F/T can be tracked well. This verifies the validity and correctness of the characterization algorithm and peg-in-hole controller for CDSR-CWs in this paper. Originality/value First, to the authors’ knowledge, there is no relevant work about the peg-in-hole assembly task using a CDSR-CW. Besides, the proposed characterization algorithm for the elastic F/T makes the peg-in-hole controller get rid of the dependence on the F/T sensor, which expands the application scenarios of the peg-in-hole controller. Finally, the controller does not require an accurate compliance matrix, which also increases its applicability.