Exploiting Link Elasticity in a Conventional Industrial Robot Arm


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Exploiting Link Elasticity in a Conventional Industrial Robot Arm
Malzahn, Jörn
Bertram, Torsten
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TU Dortmund, Lehrstuhl für Regelungssystemtechnik
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Conventional industrial robots are intended for fast and precise manipulation of heavy payloads. The optimization of these objectives results in the bulky design of today's conventional industrial robots, aiming at the maximization of precision through structural rigidity. The video demonstrates that the question, whether a robot arm is rigid or not, basically depends on how close you wish to look at it. A human can deflect the endeffector of a typical conventional industrial robot by hand without major efforts. The video illustrates the structural oscillations and deflections in the order of 2 mm resulting from moderate manual pushes. The deflections and oscillations originate from a combination of the actually present joint as well as link elasticity. While the joint elasticity due to the harmonic drive gears as well as the drive belts are surely dominant, the link elasticity is also measurable. The presented work employs optical strain sensors -- so called Fiber-Bragg-Grating sensors -- for this purpose. The optical fibers are glued onto the links and their working principle is briefly sketched in the second part of the video. In the third part of the video the link elasticity is exploited to make the conventional industrial robot backdriveable. The demonstrated experiment is a physical interaction with the robot. The human touches the arm at arbitrary points along the structure in order to reconfigure the arm posture as desired. The techniques used in the video have been developed and investigated in previous works on the multi-elastic-link arm TUDOR (watch our previous video with TUDOR: http://youtu.be/kJPuenyxeps). The experiments shown in this video represent a straight forward transfer of these techniques to a conventional industrial robot. The strain dynamics modeling of elastic link robots is presented in: Malzahn, J., R. F. Reinhart and T. Bertram: Dynamics Identification of a Damped Multi Elastic Link Robot Arm under Gravity, IEEE International Conference on Robotics and Automation, Honkong, China, 2014 The usage of the strain dynamics model for interaction control is explained in: Malzahn, J. and T. Bertram: Collision Detection and Reaction for a Multi-Elastic-Link Robot Arm, IFAC World Congress, Cape Town (South Africa), 2014 Video outline: 00:10 Demonstration of elasticity in a conventional robot arm 00:33 Link deflection measurement principle 01:30 Experiment: physical interaction with a conventional robot arm Note: The experiments shown in the video have been conducted by professionals. For your own safety: NEVER STAY INSIDE THE WORKSPACE OF AN INDUSTRIAL ROBOT IN OPERATION! For more information on the project please visit: http://tinyurl.com/TUDORRobot
oscillation damping
collision detection
flexible robot
elastic link
flexible link
force control
reis robotics
fibre bragg grating
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Computer animation Chain
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Computer animation Chain Fiber Optics
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Computer animation


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