Design of a pneumatic growing robot inspired to plants' roots

Although plants are usually seen as static organisms, they exhibit a wide range of movements that only in recent years have been considered as a source of inspiration for robots. The motion of roots is one of the most interesting, because they are extraordinary diggers, able to navigate in unstructured environments, finding their way around obstacles. Moreover, root growth is featured by high energy efficiency because they penetrate the soil adding new material at their tip, without moving the already grown part, preventing friction from dissipating energy and reducing the inertia. A robot inspired to roots' growth could be employed in search and rescue operations or in environmental monitoring. In this work the design of a soft robot inspired to root's growth is presented. The body of the robot consists of a cylindrical plastic membrane folded inside itself. When air is blown from the base, the body of the robot is inflated, and its tip is everted increasing its length. On the external surface some Velcro stripes are mounted, which keep the membrane folded. Inside the tip a head is mounted, where the mechanism controlling the direction of growth is placed. It consists of a housing for some balloons, which can be inflated selectively, and their expansion exerts a pressure on the external surface able to open the Velcro stripes. The direction of growth is controlled by selecting which balloon to inflate. The robot has been built and a kinematic model of its motion in the plane has been developed and compared with experimental results.