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Research Papers

Preferable Workspace for Fatigue Life Improvement of Flexible-Joint Robots Under Percussive Riveting

[+] Author and Article Information
Yuwen Li

Professor
School of Mechatronic Engineering and Automation,
Shanghai University,
Shanghai 200444, China
e-mail: yuwen.li@mail.mcgill.ca

Shuai Guo

Associate Professor
School of Mechatronic Engineering and Automation,
Shanghai University,
Shanghai 200444, China
e-mail: guoshuai@shu.edu.cn

Fengfeng (Jeff) Xi

Professor
Department of Aerospace Engineering,
Ryerson University,
Toronto, ON M5B 2K3, Canada
e-mail: fengxi@ryerson.ca

1Corresponding author.

Contributed by the Dynamic Systems Division of ASME for publication in the JOURNAL OF DYNAMIC SYSTEMS, MEASUREMENT, AND CONTROL. Manuscript received November 8, 2015; final manuscript received October 7, 2016; published online February 13, 2017. Assoc. Editor: Douglas Bristow.

J. Dyn. Sys., Meas., Control 139(4), 041012 (Feb 13, 2017) (7 pages) Paper No: DS-15-1560; doi: 10.1115/1.4035164 History: Received November 08, 2015; Revised October 07, 2016

This paper proposes a method to find the preferable workspace for fatigue life improvement of robots with flexible joints under percussive riveting. The development is motivated by the growing interest in using industrial robots to replace human operators for percussive riveting operations in aerospace assembly. A most important characteristic of robotic percussive riveting is the repetitive impacts generated by the percussive rivet gun. These impacts induce forced vibrations to the robot, and the joint shaft fatigue due to the resulting stress cycles must be prevented. This paper aims at finding the preferable workspace for fatigue life improvement of the robot, that is, the end-effector positions where the joint stresses are below the endurance limit. For this purpose, a structural dynamic model is established for the robot under percussive riveting. Then, an approximate analytical solution is formulated for the torsional stresses of the robot joints. Once the distributions of the stresses are obtained over the workspace, the preferable workspace for fatigue life improvement can be found by comparing the stresses with the endurance limit. Simulation studies are carried out for a mobile robot under percussive riveting. It is found that the dynamic response of the robot to the percussive riveting varies dramatically over the workspace. The method is then used to obtain the preferable positions of the robot end-effector for fatigue resistance.

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Figures

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Fig. 1

Mobile industrial robot

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Fig. 2

Robotic percussive riveting for fuselage panels

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Fig. 3

A typical S–N diagram from fatigue test [21]

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Fig. 5

Reference frames for riveting flat panels

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Fig. 6

Maximum joint stresses over potential workspace with force direction n=[−1,0,0]T: (a) joint 1, (b) joint 2, and (c) joint3

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Fig. 7

Preferable workspace with force direction constraint WP1 with n=[−1,0,0]T

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Fig. 8

Maximum stresses in different planes with force direction n=[−1,0,0]T

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Fig. 9

Preferable workspace without force direction constraint WP2

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