Abstract: To address the difficulties in realizing both functions and high accuracy of an active direction control scheme for self-growing soft robots, an asymmetric fold structure inspired by the abdominal segment structure of marine benthos of the Malacostraca is proposed. The asymmetric fold structure is deployed outside the control chambers to realize asymmetric expansion under inflation pressure. High-precision reversible active direction control of capsules can be realized using this scheme. The manufacturing of a self-growing soft robot prototype is completed based on this scheme. The mathematical model for the relationship between the design parameters such as fold width and fold spacing and performance such as steering radius and angle is proposed, which is then analyzed by theoretical studies and numerical simulation, and further verified by experiments. Results show that the proposed scheme can effectively realize large-angle and high-precision reversible direction control without interfering with the moving ability of the capsule, and a high degree of design freedom can be achieved. The theoretical model can accurately predict the capsule's kinematic performance. The designed self-growing soft robot can be applied to missions such as the investigation of and guidance in narrow non-intervisibility spaces in future urban operations.

Key words: softrobot, bionics, self-growingtip, asymmetricfold, kinematiccharacteristics