To read the full version of this content please select one of the options below:

Research on the forcefree control of cooperative robots based on dynamic parameters identification

Juliang Xiao (Key Laboratory of Mechanism Theory and Equipment Design of Ministry of Education, Tianjin University, Tianjin, China)
Fan Zeng (Key Laboratory of Mechanism Theory and Equipment Design of Ministry of Education, Tianjin University, Tianjin, China)
Qiulong Zhang (Key Laboratory of Mechanism Theory and Equipment Design of Ministry of Education, Tianjin University, Tianjin, China)
Haitao Liu (Key Laboratory of Mechanism Theory and Equipment Design of Ministry of Education, Tianjin University, Tianjin, China)

Industrial Robot

ISSN: 0143-991x

Article publication date: 20 June 2019

Issue publication date: 5 August 2019

Abstract

Purpose

This paper aims to propose a forcefree control algorithm that is based on a dynamic model with full torque compensation is proposed to improve the compliance and flexibility of the direct teaching of cooperative robots.

Design/methodology/approach

Dynamic parameters identification is performed first to obtain an accurate dynamic model. The identification process is divided into two steps to reduce the complexity of trajectory simplification, and each step contains two excitation trajectories for higher identification precision. A nonlinear friction model that considers the angular displacement and angular velocity of joints is proposed as a secondary compensation for identification. A torque compensation algorithm that is based on the Hogan impedance model is proposed, and the torque obtained by an impedance equation is regarded as the command torque, which can be adjusted. The compensatory torque, including gravity torque, inertia torque, friction torque and Coriolis torque, is added to the compensation to improve the effect of forcefree control.

Findings

The model improves the total accuracy of the dynamic model by approximately 20% after compensation. Compared with the traditional method, the results prove that the forcefree control algorithm can effectively reduce the drag force approximately 50% for direct teaching and realize a flexible and smooth drag.

Practical implications

The entire algorithm is verified by the laboratory-developed six degrees-of-freedom cooperative robot, and it can be applied to other robots as well.

Originality/value

A full torque compensation is performed after parameters identification, and a more accurate forcefree control is guaranteed. This allows the cooperative robot to be dragged more smoothly without external sensors.

Keywords

Acknowledgements

This work was supported in part by the National Natural Science Foundation of China under Grant 51721003, 51622508, and 91648202.

Conflict of interest. The author(s) declared no potential conflicts of interest with respect to the research, authorship and/or publication of this article.

Funding: This work was supported in part by the National Natural Science Foundation of China under Grant 51721003, 51622508, and 91648202.

Citation

Xiao, J., Zeng, F., Zhang, Q. and Liu, H. (2019), "Research on the forcefree control of cooperative robots based on dynamic parameters identification", Industrial Robot, Vol. 46 No. 4, pp. 499-509. https://doi.org/10.1108/IR-01-2019-0007

Publisher

:

Emerald Publishing Limited

Copyright © 2019, Emerald Publishing Limited