Design of a Hyper-Redundant Manipulator With Zigzag Mechanism Doublet

Continuum and snake-like hyper-redundant robots perform circular bending motions, enable them to navigate obstacles and operate in confined spaces, making them ideal for applications such as industrial inspection and minimally invasive surgery. However, their performance often diminishes at the distal end, particularly in terms of positioning accuracy and output force during high-curvature tasks, which are considered their specialty. This letter introduces a novel hyper-redundant manipulator composed of zigzag-jointed folding links and intermediary connecting links. Each basic unit, termed a zigzag mechanism doublet (ZMD), consists of two folding links and their interacting connecting links, providing symmetric kinematic inputs and outputs. The output of one ZMD unit serves as the input for the next, enabling the entire manipulator to be actuated by the initial unit. By connecting multiple ZMD units, the manipulator approximates circular bending motion. This design outperforms traditional snake-like hyper-redundant manipulators in three aspects. First, it achieves bending motion through structural constraints, eliminating the need for tendons or other appendages to actuate multiple joints. Second, each unit extends the manipulator's motion range, rather than distributing a limited bending range across the entire structure. Third, the ZMD chain achieves constant curvature in discrete form, enhancing the manipulator's payload capability throughout its full motion range, even in extreme bending configurations. Experimental evaluations were conducted on a 3D-printed prototype and compared with typical articulated and continuum manipulators. The ZMD-based manipulator demonstrated a mean repeatability of 0.32 mm and a payload of 200 g, offering a promising solution for operations in constrained environments.