Inflated Bendable Eversion Cantilever Mechanism With Inner Skeleton for Increased Stiffness

Inflatable structures used in soft robotics applications have unique characteristics. In particular, the tip-extension structure, which extends the structure from its tip, can grow without creating friction with the environment. However, these inflatable structures need high pressure to maintain their stiffness under various conditions. Excessive inner pressure limits their application in that it prevents the structure from maintaining its curved shape and from complying with specifications. This study aimed to simultaneously lower the pressure and increase the rigidity of the structure. Our work resulted in the proposal of a mechanism that combines a skeleton structure consisting of multi-joint links with functions to increase the rigidity. Insertion of this mechanism into an inflatable structure obviates the need for high inner pressure, yet enables the structure to bend and maintain the intended shape. We devised a design based on rigid articulated links and combined it with a membrane structure that utilizes the advantages of the tip-extension structure. The experimental results show that the payload of the structure designed to operate at low pressure increases compared to that of the membrane-only structure. The findings of this research can be applied to long robots that can be extended into open space without drooping and to mechanisms that enable structures to wrap around the human body.