Design and Modeling of a Nested Bi-cavity-based Soft Growing Robot for Grasping in Constrained Environments

Soft growing robots with unique navigation (tip extension by eversion) hold great promise in rescue, medical, and industrial applications. Equipping them with grasping capability would enhance their usefulness in constrained environments for various applications. However, in traditional designs, the tip’s eversion naturally conflicts with grasping, and the addition of grippers at the tip would limit navigation inevitably in constrained environments. To realize grasping in such scenes without extra devices, we propose a nested bi-cavity-based growing soft robot (BIBOT). The new design consists of two coaxially nested cavities, where the inner and outer cavities extend synchronously by inversion and eversion of the film rolls. Such a bi-cavity design enables the BIBOT to navigate and grasp without relative movements between the body and environment, and avoids contact between the object and its surroundings as well. Further, a kinematics model is established and verified to precisely control its lengthening and steering by a feed mechanism. Finally, its capability in a constrained environment is demonstrated by navigating and grasping an object in a curved pipe with a variable internal diameter.