Effect of Rotational Cone on Penetration Resistance and Its Implication to the Design of a Bio-Inspired Self-Burrowing Robots

Abstract

A previous study by the authors showed that the rotational movement of a penetrating rod could reduce the penetration resistance. In this study, the effect of rotation on penetration is further studied to shed light on the design of a seed-inspired self-burrowing robot. Three penetration strategies were modeled using the discrete element method: (1) control case, (2) whole-body-rotation (WBR) case, and (3) cone-rotation (CR) case. It was observed that the cone penetration resistance could be reduced to similar levels due to WBR and CR at the same rotational speed. Further analysis of particle–penetrator contact data unveils that rotation of the cone reduces the contact number, and the magnitude of the contact forces. A slight reduction of the shaft friction is also observed in WBR cases, yet with a cost of much higher energy consumption to induce the rotation of the shaft. Comparing the three penetration strategies, the CR strategy is considered the most suitable for a self-burrowing robot as it reduces penetration resistance with the lowest energy consumption.