A tensegrity robot inspired from the bird neck

Today's industrial robots are built around rigid, articulated components driven by a set of motors and transmission systems. This mechanical architecture gives them a high mass, which limits their dynamics and dexterity. It also makes physical interaction with the environment dangerous. On the other hand, some animals have exceptionally powerful, flexible organs that enable them to perform a wide range of difficult tasks with ease. The octopus's tentacle and the elephant's trunk, for example, have fascinated roboticists for many years. These organs, which are totally soft because they have no bones, have inspired some roboticists and given rise to a community called "soft robotics" , which aims to design deformable robots without rigid parts. However, such architectures are very difficult to implement, both in terms of construction and control. There are organs which also offer remarkable performance, but which, unlike their predecessors, are not totally soft, as they are made up of articulated bones or vertebrae. This is the case, for example, of a bird's neck. Birds use their necks as dexter arms for everyday or more specialized tasks. A vulture's neck can be contorted to penetrate carcasses, while exerting great effort to remove food scraps. The parrot is able to suspend itself by its beak, using its neck as a third leg to move around. Finally, other birds use their necks as catapults to catch fish or pierce tree trunks. These remarkable performances prompted the roboticist to use the bird's neck as a model to inspire the design of an innovative robot. The neck is built around a cervical column of articulated vertebrae, moved by a set of muscles and tendons. In mechanics, there are structures that are particularly well-suited to modeling musculoskeletal systems: tensegrity (see definition below). Made up of rigid bars, springs and cables, a tensegrity can feature controlled mobilities; this is referred to as a "tensegrity mechanism".

This article describes the scientific approach that led to the development of a robot prototype inspired by the neck of a bird, and more specifically the neck of a woodpecker. Based on morphological and functional analyses derived from biology, we show how a simplified biomechanical model can be developed that is sufficiently realistic to enable the simulation and subsequent design of a functional prototype. Figure