Journal of Bionic Engineering (2025) 22:65–82 https://doi.org/10.1007/s42235-024-00631-2

Topological Structure Design and Obstacle-climbing Capability Analysis of a Lizard-inspired Torso-leg-foot Biomimetic Robot

Yuting Du1  · Yan-an Yao1  · Qiang Ruan1  · Wenbo Mi2

1 School of Mechanical, Electronic and Control Engineering, Beijing Jiaotong University, Beijing 100044, China 

2 Beijing Institute of Aerospace Control Devices, Beijing 100039, China

Abstract 

Lizards are one of the most primitive reptiles in existence, with special limb structures that enable them to move quickly across diverse and complex terrains such as rock piles, shallow shoals, and deserts. A thorough exploration was conducted on the biomimetic mechanism and ground-touching mechanism of lizard limbs from both micro and macro perspectives. Inspired by the intricate torso and limb configurations of lizards, a novel Torso-leg-foot biomimetic robot has been conceptualized based on the design of the Big-Foot robot. This robot integrates a Torso-leg-foot system, featuring a parallel torso biomimetic structure with a 2-SPR/UPU/UPR(P) configuration. It utilizes the theory of finite screws to articulate the instantaneous movements of the parallel torso, and the inverse kinematics of this mechanism have been calculated. The reachable workspace of the 2-SPR/UPU/UPR parallel mechanism using FIS theory, which is closely related to the climbing height of the robot. A comprehensive dimension synthesis was conducted on the leg-foot system, and the adoption of the three-pair rod drive method was determined by investigating its Variable Rotating Velocity Characteristics (VRVC). Simulation tests have shown that with an integrated torso, the robot can climb vertical obstacles up to 600 mm in height. The experimental tests of climbing steps and slopes using physical prototypes have confirmed the robot’s obstacle-crossing capability. The potential applications of this Torso-leg-foot biomimetic robot is to carry heavy objects across obstacles to perform tasks such as planetary exploration and disaster relief. 

Keywords Torso-leg-foot · Lizard biomimetics · Topological structure · Variable Rotating Velocity Characteristics (VRVC) · Obstacle-climbing capability