Adaptive tensegrity foot design for quadruped robots in unstructured terrains

Traditional quadruped robots are known for their agile movement and versatility across varied terrains. However, their foot structures struggle to navigate unstructured terrains such as pipes, slopes, and protrusions. This paper proposes a novel tensegrity foot structure consisting of a tensegrity ankle joint and an X-shaped adaptive tensegrity footpad, which enhances the terrain adaptability of legged robots. The equilibrium equation of the ankle joint is established, and the relationship between the translational stiffness of the ankle joint and the spring stiffness is derived. Additionally, a mathematical model for the number of X-shaped tensegrity footpad units and their relationship with the deformation height and length of the tensegrity footpad is established. A physical prototype of the tensegrity foot was fabricated using 3D printing. Experiments are conducted to validate the adaptability of both the ankle joint and the tensegrity footpad. The results indicate that the proposed adaptive tensegrity foot structure exhibits good adaptability on unstructured terrains with varying radii, slopes, steps, S-curves, and spherical surfaces. The tensegrity foot structure can enhance the environmental adaptability of quadruped robots and has excellent impact resistance effects.