An invention has been developed by South Korean scientists that will literally expand the reach of drones – a lightweight, foldable robotic arm.
Inspired by the traditional Japanese folding technique origami, the arm can be equipped with a grab or a camera and allows access to tubes, chimneys or other narrow places. A team of scientists led by Kyu-Jin Cho from Seoul National University in Seoul (South Korea) presented the device in the journal “Science Robotics“.
“The lack of structural rigidity has been a major limitation in the practical use of designs inspired by origami,” the researchers write. They solved the problem with an additional element in their foldable boxes, a stiffening mechanism that uses the perpendicular folding principle of origami.
The simple mechanism retracts into the robotic arm in its extended form, between the bottom and lid of the box and thus ensures rigidity. According to the scientists, this system is five times more resistant to bending and 200 times more compressible than with no stiffening mechanism. When folded, the robotic arm is only four centimetres long, and when extended, 70 centimetres.
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To save weight, Cho and colleagues planned only a single electric motor. This is connected via a cord to the seven stacked boxes and the stiffening mechanism. When deployed, elastic bands pull the individual parts of the arm into their box shape. Contacts are brought into their position by small magnets, causing the arm to stiffen. When retracting the arm, the electric motor folds the boxes together by rolling up the cord against the resistance of the elastic bands and magnets.
The walls of the boxes are made of polyethylene terephthalate (PET) and a ripstop fabric, as used in parachutes. During production, two PET films are joined together with the intermediate ripstop fabric by means of a hot press. This lightweight design means that the 70-centimeter-long robot arm including the electric motor weighs no more than 260 grams. This is important because the payload is very limited on most drones.
The researchers identify one weakness of in the design, that is that the robotic arm becomes unstable when the drone flies at speed with the arm extended. Also, currently the robotic arm is only designed in a rigid state, but they are confident that another version of the foldable arm can be designed with joints.