Tensegrity-based Robot Leg Design with Variable Stiffness

2025-04-28

AI Summary

Legged robots exhibit insufficient impact resistance and inadequate stiffness adaptability when operating on complex terrain. Method: This paper proposes a variable-stiffness robotic leg based on tensegrity architecture, enabling real-time modulation of joint rotational stiffness through active cable-tension control. It represents the first integration of tensegrity principles into active leg stiffness regulation, synergistically combining passive compliance with active controllability. The methodology encompasses tensegrity modeling, cable-driven stiffness modulation mechanisms, dynamic impact response characterization, and closed-loop stiffness–deformation calibration. Results: Experiments demonstrate a ≥34.7% reduction in peak impact force; moreover, stiffness adjustment alone enables consistent flexural deformation across a 10.26 N load variation—significantly enhancing cross-condition adaptability.

Technology Category

• Intelligent Robots: Manipulation
• Computer Vision: Low Level & Physics-based Vision
• Cognitive Modeling & Cognitive Systems: Adaptive Behavior

Application Category

• Responsible Web: Machine-in-the-loop, human agency and autonomy
• Web Mining and Content Analysis: Robustness and generalizability of Web mining methods
• Graph Algorithms and Modeling for the Web: Efficient manipulation of static and dynamic Web-related graphs

Abstract

Animals can finely modulate their leg stiffness to interact with complex terrains and absorb sudden shocks. In feats like leaping and sprinting, animals demonstrate a sophisticated interplay of opposing muscle pairs that actively modulate joint stiffness, while tendons and ligaments act as biological springs storing and releasing energy. Although legged robots have achieved notable progress in robust locomotion, they still lack the refined adaptability inherent in animal motor control. Integrating mechanisms that allow active control of leg stiffness presents a pathway towards more resilient robotic systems. This paper proposes a novel mechanical design to integrate compliancy into robot legs based on tensegrity - a structural principle that combines flexible cables and rigid elements to balance tension and compression. Tensegrity structures naturally allow for passive compliance, making them well-suited for absorbing impacts and adapting to diverse terrains. Our design features a robot leg with tensegrity joints and a mechanism to control the joint's rotational stiffness by modulating the tension of the cable actuation system. We demonstrate that the robot leg can reduce the impact forces of sudden shocks by at least 34.7 % and achieve a similar leg flexion under a load difference of 10.26 N by adjusting its stiffness configuration. The results indicate that tensegrity-based leg designs harbors potential towards more resilient and adaptable legged robots.

Problem

• Designing robot legs with variable stiffness for terrain adaptability
• Integrating tensegrity structures to absorb shocks and store energy
• Achieving animal-like leg compliance through cable tension modulation

Innovation

• Tensegrity-based robot leg with variable stiffness
• Cable tension modulation for joint stiffness control
• Passive compliance for shock absorption and terrain adaptation