Journal of Bionic Engineering (2025) 22:171–180https://doi.org/10.1007/s42235-024-00633-0

Mole-inspired Forepaw Design and Optimization Based on Resistive Force Theory

Tao Zhang1,2  · Zhaofeng Liang2  · Hongmin Zheng2  · Zibiao Chen2  · Kunquan Zheng2  · Ran Xu1  · Jiabin Liu2  · Haifei Zhu2  · Yisheng Guan2  · Kun Xu1  · Xilun Ding1

1 School of Mechanical Engineering and Automation, Beihang University, Beijing 100191, China 

2 School of Electro-mechanical Engineering, Guangdong University of Technology, Guangzhou 510006, China

Abstract 

Moles exhibit highly effective capabilities due to their unique body structures and digging techniques, making them ideal models for biomimetic research. However, a major challenge for mole-inspired robots lies in overcoming resistance in granular media when burrowing with forelimbs. In the absence of effective forepaw design strategies, most robotic designs rely on increased power to enhance performance. To address this issue, this paper employs Resistive Force Theory to optimize mole-inspired forepaws, aiming to enhance burrowing efficiency. By analyzing the relationship between geometric parameters and burrowing forces, we propose several forepaw design variations. Through granular resistance assessments, an effective forepaw configuration is identified and further refined using parameters such as longitudinal and transverse curvature. Subsequently, the Particle Swarm Optimization algorithm is applied to determine the optimal forepaw design. In force-loading tests, the optimized forepaw demonstrated a 79.44% reduction in granular lift force and a 22.55% increase in propulsive force compared with the control group. In robotic burrowing experiments, the optimized forepaw achieved the longest burrow displacement (179.528 mm) and the lowest burrowing lift force (0.9355 mm/s), verifying its effectiveness in reducing the lift force and enhancing the propulsive force. 

Keywords Resistive force theory · Mole-inspired forepaw design · Structural optimization · Bioinspired robot