A robot arm that provides a unique approach to lifting and pulling actions.

Gummi Arm

<p>The GummiArm is a 7+1 DOF robot arm. The structure of the arm consists of plastic parts connected to digital servos. The servos are joined by PLA-based plastic parts that can be printed on hobby-grade 3D printers.</p><p>A key element is the agonist-antagonist joints driven by accurate digital servos, and with viscoelastic composite tendons. The inherent damping and the ability to adjust stiffness in real-time helps simplify joint control.</p><h1><strong>Design</strong></h1><p>The arm structure is made of PLA plastic, and is printable on hobby-grade 3D printers. The first prototype was printed on a BQ (Madrid, Spain) Prusa i3 Hephestos printer with 20% infill.</p><p>The Dynamixel servos are controlled using the USB2Dynamixel device, and the corresponding ROS package. The arm is actuated by Dynamixel servos from Robotis Inc (Irvine, CA, USA). There are 5 agonist-antagonist joints, each with 2 Dynamixel servos pulling on tendons that work against each other. For example the biceps and triceps actuating on the elbow joint. 2 joints are directly driven by servos, and 1 servo is included in the forearm to drive a hand.</p><h3><strong>Elbow Design Process</strong></h3><p>A quasi-static loading setup was created for the elbow joint. The upper arm was locked in place, while the lower arm was replaced with a rigid beam with multiple attachment points for weights, from 70 mm to 200 mm from the joint axis, and at 10 mm intervals.</p><p>The actuator was commanded to a passive</p><p>horizontal pose. Three different weights (0.1 kg, 0.5 kg, and 1.5 kg) were then attached at different distances from the joint axis to generate a set of torques up to almost 3 Nm. The passive deflection of the joint was then recorded with the AX-12A encoder. This process was repeated three times for the 3 weights and the 14 distances. The same procedure was repeated for 5 different stiffness levels,</p><p>from 0% to 100%.</p><p><img data-fr-image-pasted="true" src="https://projects.wevolver.com/wevolver.staff/Gummi%20Arm/readfile?path=Images/Gummi%20(8%2529.png&amp;permissions=eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1NiJ9.eyJleHAiOjE2MDQ1MTEwMjYsImlzcyI6Indldm9sdmVyIiwidXNlciI6IjVjZWNiZjA4YjQyY2JhMTM2ZWMyZWM3ZiIsInByb2plY3QiOiJHdW1taSBBcm0iLCJwZXJtaXNzaW9ucyI6IlsncmVhZCcsICd3cml0ZScsICdjcmVhdGUnXSJ9.nWzpIm6RYCdLE0414rC2v3hIAZEYnkmgb_lDAQl1Ww035RIFFjwzIBOSKDSlrdap-Uw8MtNgOAXwINIDYPx42voG-g7P_RC6sDLCtUnbY_DnoHfq6VNUze38gyzEDySP0JIaS_HZTKpFQYIMWacwCe4mV08Nq3kW5c7b-JT5zIRlioUXiC31mroEpb4v7tt25_BfA4cyK2bz2WmBLsqw6wpjzmjTDYaofk6VPMZRKPDZDmjfll5TFAL7ExMaOY_CR7tCrtlsqh4CkYbUeWjDVPQwp26AHZgZenBC_yJBQ4UI-GTjtfVb1hFMaiE5TJF5LUkblU0O2RdkEpYRcMhzvVFx92wFPhe7BBLgLsYNnq1kBXzoKFGjkuJcKEyZ_GMWaNmGOv7L61WsAKlFYQeSyyF2aHWEZefv85aCRY1pBvDZddA4JX7Uan1nEPks7tqODfM37xmEgR8JngPQ55u-5q1Jej7bQGmNLp43DvBLdoD5wvHXugkqm7VlwfSVksMarOOE6kWWgSjQvs6vXlW8ZA6RELnmtdzv04oiXVRO5x6XxESkNGhiPpsQU5YB3SoMY8ZxYJjC9pl2yqyNk8kSduVdrAsCQDNaloBBGe5mq6ZFjONHVnuFu2wpFDW6knLfjvafgIqht4-xdYiq7pMc6CdPA84dqfCsx1aJ7WxOmLU" alt="" class="fr-fic fr-dii"></p><h3><strong>Specifications</strong></h3><ul><li>Structure is 3D printable</li><li>Various attachments available for customization</li><li>Modular build for size increase or reduction according to the users' needs</li><li>Twisted tendon-driven design</li></ul>

https://github.com/mstoelen/GummiArm/wiki

https://plus.google.com/collection/oGXbV

https://www.researchgate.net/publication/303881123_Co-Exploring_Actuator_Antagonism_and_Bio-Inspired_Control_in_a_Printable_Robot_Arm

A 3D printed robot arm that provides a unique approach to lifting and pulling actions by using a tendon-driven method.

