Kinematic Design and Simulation of a Rigid–Flexible Caterpillar Robot with Opposite-Handed Kresling Cell Pairs

Abstract

Inspection in confined and unstructured environments requires compact crawling robots to coordinate large axial deformation, foot orientation, and multiple anchoring sites within a limited body length. The intrinsic axial–torsional coupling of Kresling cells, however, makes it difficult to map rotational inputs directly to phase-wise whole-body displacement. We present a rigid–flexible caterpillar robot comprising three rigid sections and two flexible sections, each formed by an opposite-handed pair of Kresling cells, together with a hierarchical kinematic model that links cell geometry and flexible-section configuration to a twelve-phase gait under ideal anchoring. For $n=8, r=3 \text{cm}$, $h_{0}=\text{4 cm}$, and $h_{\min }=1 \text{cm}$, increasing the cell twist from 0° to 52.77° produces an axial displacement of 3 cm, while opposite-handed cells exhibit equal-magnitude, opposite-direction responses under identical prescribed rotations. The length of each flexible section increases from 2 to 8 cm and then returns to 2 cm. Transferring this axial deformation from $F_{1}$ to $F_{2}$ moves each rigid section forward by 6 cm over one twelve-phase cycle while restoring the module rotations, flexible-section lengths, and rigidsection orientations to their initial states. These results establish the kinematic feasibility of the proposed configuration-to-gait mapping under quasi-static, idealized anchoring and provide a model basis for future prototype tests of microspine anchoring and slip.