Bio-inspired design of alternate rigid-flexible segments to improve the stiffness of a continuum manipulator

Intrinsic flexible structures enable a continuum manipulator to exhibit attractive dexterity and intrinsic compliance over traditional hyper-redundant robots. However, its insufficient stiffness makes the performance of continuum manipulators unsatisfactory and thus limits the applications in many fields. A significant challenge is how to make a trade-off among dexterity, compliance and stiffness. From an evolutionary perspective, this paper compares several biological structures that enable the continuum manipulator function, and intends to reveal the mechanism on how the biological structures can improve the stiffness. The notochord and the vertebral column with acoelous centra are abstracted and physically implemented. A fundamental rod-driven continuum manipulator is also introduced as a comparison. The stiffness models of these three continuum manipulators are proposed, and comparative experiments are conducted to verify their stiffness properties. Our results demonstrate that the rigid-flexible segmental structure can improve the stiffness properties of a continuum manipulator.