DESIGN IDEAS
❱❱ Drone fitted with the light weight robotic arm could be used to retrieve objects, below; the Seoul research team, bottom
ORIGAMI-INSPIRED SELF-LOCKING FOLDABLE ROBOTIC ARM
A research team at Seoul National University has developed an origami-inspired robotic arm that is foldable, self-assembling and also highly-rigid. This novel robotic arm has variable stiffness
— it is light and can fold flat, yet can extend like an automatic umbrella and become stiff in an instant by changing the shape with a single wire, a practical use of origami. The key principle is a collapsible locking
device, which enables the robotic arm to overcome the drawbacks of origami-inspired structures, which don’t easily withstand external forces and which are hard to be easily actuated. In the origami principle of perpendicular
folding, two perpendicular fold lines constrain each other’s movement. By using this principle, a hexagonal structure (40 x 40 x 100mm), which weighs less than 30g, can withstand more than 12kg of compressive load. The locking devices can be easily deactivated, whereby the structure is folded flat by pulling a single wire with a small force. Benefits of the foldable robotic arm are
maximised when it is attached to drones, where the weight and size constraints are stringent. When the robotic arm is not in use, it folds flat for manoeuvring, take-off and landing. But variable stiffness can be applied to other types of robots and structures in hostile environments, such as in extreme temperatures, underwater and space. “Soft robots have great advantages in their
flexible movement, but they have a limitation in that they cannot support high loads without deformation,” says Professor Kyu-Jin Cho. “This robotic arm uses the variable stiffness technology which combines the advantages of both rigid and soft robots. With this capability, the robotic arm can be folded flat when not in use and can be stiff when necessary. In addition, the arm is made of a composite of tough ripstop fabric and specially handled strong PET film.” When the wire is pulled using a motor, the
force to both unlock the variable stiffness mechanism and fold the arm occur simultaneously. When lockers are wedged inside the module, the variable stiffness mechanism moves and unlocks the structure. Then the robotic arm folds. This wire-driven actuation mechanism is also scalable. ❱❱ Suk-Jun Kim, Dae-Young Lee, Gwang-Pil Jung, Kyu-Jin Cho. Origami-inspired lightweight self-locking foldable manipulator, Science Robotics, 14 March 2018.
June 2018 /// Environmental Engineering /// 7
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