Woodpecker-inspired Arm

Woodpeckers have flexible and extendable tongues that they use to reach their prey through tiny openings in trees and insect burrows. A robotic manipulator with these capabilities would be advantageous. For example, this kind of manipulator would be able reach a product on the back of a cluttered shelf. Such a concept is promising for applications which require picking and handling actions in unstructured environments, but to-date only exists in science fiction and fantasy (e.g., Doctor Octopus from Spider-Man).

  Although continuum robots can produce dexterous movements because of their few shape constraints, the lack of structural stiffness has restricted their deployment in real-world environments. For example, soft continuum manipulators have a stretchable backbone, including springs, origami, and telescopic pipes to extend their lengths. They can turn in any direction but at the cost of the extension distance due to design limitations of the elasticity of springs and origami or the diameter of telescopic pipes. They also lack structural stiffness, making it challenging to use them in many applications, particularly those which require the grabbing and carrying of objects. 

  Inspired by the characteristics of woodpeckers, we designed a robot manipulator that can substantially extend its length and bend its shape in 2D space. This behavior is enabled by a backbone consisting of a chain of rigid joints and two flexible rack gears. The joints increase the payload by structurally supporting the robot. The proposed structure is 4.7 times stronger in vertical bending and 6.2 times stronger in torsion than without rigid links. Feeding the rack gears at the same and different speeds allows the robot to elongate and bend, respectively.