Compliant Beaded-String Jamming For Variable Stiffness Anthropomorphic Fingers

2025-02-06

AI Summary

To address the challenge of simultaneously achieving precision, pose stability, compliance, and tunable stiffness in robotic grippers under uncertain environments, this paper proposes a human-finger-inspired variable-stiffness joint mechanism. Its core innovation is a compact granular jamming-based “bead-chain” joint—the first of its kind—comprising a flexible bead-chain structure leveraging granular jamming physics, integrated with a pneumatic–mechanical hybrid stiffness modulation scheme. This design enables a fourfold stiffness adjustment range (0.48–1.95 Nm/rad) with low hysteresis and high repeatability, while preserving substantial residual compliance and human-like interphalangeal joint motion range. Joint-level mechanical modeling and dynamic peg-in-hole experiments validate the approach, demonstrating a 60% improvement in task success rate and significantly enhanced robust manipulation capability.

Technology Category

• Intelligent Robots: Manipulation
• Humans and AI: Interaction Techniques and Devices
• Cognitive Modeling & Cognitive Systems: Simulating Human Behavior

Application Category

• Responsible Web: Machine-in-the-loop, human agency and autonomy
• Economics, Online Markets and Human Computation: Trust and reliance of crowd workers and data experts on GenAI
• User Modeling, Personalization and Recommendation: On-Device user modeling, personalization, and recommendation

Abstract

Achieving human-like dexterity in robotic grippers remains an open challenge, particularly in ensuring robust manipulation in uncertain environments. Soft robotic hands try to address this by leveraging passive compliance, a characteristic that is crucial to the adaptability of the human hand, to achieve more robust manipulation while reducing reliance on high-resolution sensing and complex control. Further improvements in terms of precision and postural stability in manipulation tasks are achieved through the integration of variable stiffness mechanisms, but these tend to lack residual compliance, be bulky and have slow response times. To address these limitations, this work introduces a Compliant Joint Jamming mechanism for anthropomorphic fingers that exhibits passive residual compliance and adjustable stiffness, while achieving a range of motion in line with that of human interphalangeal joints. The stiffness range provided by the mechanism is controllable from 0.48 Nm/rad to 1.95 Nm/rad (a 4x increase). Repeatability, hysteresis and stiffness were also characterized as a function of the jamming force. To demonstrate the importance of the passive residual compliance afforded by the proposed system, a peg-in-hole task was conducted, which showed a 60% higher success rate for a gripper integrating our joint design when compared to a rigid one.

Problem

• Achieving human-like dexterity in robotic grippers
• Integrating variable stiffness mechanisms for precision
• Introducing Compliant Joint Jamming for adjustable stiffness

Innovation

• Compliant Joint Jamming mechanism
• Passive residual compliance
• Adjustable stiffness control