Kiju Lee, with Twister robotics device (Russell Lee, Case Western Reserve University)
28 September 2017. An engineering lab at Case Western Reserve University developed a soft robotic arm that grips and manipulates fragile objects, such as in surgery. Researchers led by mechanical and aerospace engineering professor Kiju Lee described their device in a paper presented yesterday at the International Conference on Intelligent Robots and Systems in Vancouver, British Columbia.
Lee and colleagues designed the robotics arm they call Twister, short for twisted tower robot, to offer a highly compact device that can expand, bend, and manipulate fragile objects. Robotics with these features could meet various needs in manufacturing, space exploration, and medicine, particularly in minimally invasive surgery. The team from the university’s Distributed Intelligence and Robotics Lab in Cleveland based its work on origami, a Japanese art form that creates elegant designs folded from single sheets of paper.
The researchers designed Twister as a series of shapes — triangles, hexagons, and octagons — built into a tube, inspired by the work of artist Mihoko Tachibana, who built an origami tower in multiple modular segments. While the team used paper for earlier origami-based robotics, the researchers found constructing a detailed and complex device like Twister would require 3-D printing, following a computer-assisted design.
The device itself uses two types of materials, rigid materials for the surfaces and soft flexible materials for the hinges and splines connecting the modules. The team printed Twister on a Stratasys Connex3 printer, using transparent VeroClear filaments for the surfaces and TangoBlackPlus for the flexible components. Printing the device took about 8.5 hours, with another 8 hours needed for cleaning off excess materials. The researchers estimate hand-folding paper for the device would require up to 20 hours of tedious labor.
The team’s Twister prototype with 10 modules is 62.5 millimeters (2.5 inches) long when compressed, but extends to 255.5 millimeters (10.0 inches). Plastic filament cables connect the modules, with motor-driven pulleys. The researchers fitted Twister with a simple gripper at the end, along with a gyroscope sensor and miniature camera. The system uses an Arduino microcontroller for the motors and a Raspberry Pi controller for the camera.
The researchers tested Twister on two different objects, a cubic block and egg shell. The team ran 40 trials with the arm finding and grasping each object, bending and twisting in different directions, then returning the object to its original spot. The results show a 95 percent success rate with the egg shell, and 78 percent success with the block. The researchers say the unsuccessful attempts were largely due to the simple gripping device with a limited range of motion.
In addition to minimally-invasive surgery, the researchers foresee their robotic arm used in space exploration and manufacturing. In space, its compact size and collapsible design would let it be stored away, then deployed for tasks requiring precise movements of fragile objects. In manufacturing, Twister could help solve a problem of safety in having robotic devices in close proximity to workers. “Because this robot can be made with soft materials,” says Lee in a university statement, “it could be safe to use on an assembly line right next to people.”
The Twister prototype is demonstrated in this video.
More from Science & Enterprise:
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- University Spins Off Educational Robot Start-Up
- Robot Designed to Grow into Shapes, Spaces
- Computer Vision, Deep Learning Aid Prosthetic Hands
- Algorithms Simplify, Improve Robot Grasping
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