Humans possess a remarkable ability to react to unpredictable perturbations through immediate mechanical responses, which harness the visco-elastic properties of muscles to maintain balance. Inspired by this behavior, we propose a novel design of a robotic leg utilizing fibre jamming. The research highlights the potential of these structures for enhancing legged locomotion and adaptability in unpredictable environments.

Humans possess a remarkable ability to react to unpredictable perturbations through immediate mechanical responses, which harness the visco-elastic properties of muscles to maintain balance. Inspired by this behavior, we propose a novel design of a robotic leg utilizing fibre jammed structures as passive compliant mechanisms to achieve variable joint stiffness and damping. We developed multimaterial fibre jammed tendons with tunable mechanical properties, which can be 3-D printed in one-go without need for assembly. Through extensive numerical simulations and experimentation, we demonstrate the usefulness of these tendons for shock absorbance and maintaining joint stability. We investigate how they could be used effectively in a multijoint robotic leg by evaluating the relative contribution of each tendon to the overall stiffness of the leg. Further, we showcase the potential of these jammed structures for legged locomotion, highlighting how morphological properties of the tendons can be used to enhance stability in robotic legs.

Fibre jamming is a new and understudied soft robotic mechanism that has previously found success in stiffness-tunable arms and fingers. However, to date researchers have not fully taken advantage of the freedom offered by contemporary fabrication techniques including multi-material 3D printing in the creation of fibre jamming structures. In this research, we present a novel, modular, multi-material, 3D printed, fibre jamming tendon unit for use in a stiffness-tunable compliant robotic ankle, or Jammkle. Its multimaterial printed design offers unparalleled design freedom, enabling application specific tendon design. We develop analytical and finite element models of the tendon unit, showing good agreement with experimental data and numerically explore the design space. Finally, we demonstrate a practical application by integrating multiple tendon units into a robotic ankle and perform extensive testing and characterisation. We show that the Jammkle outperforms comparative leg structures in terms of compliance, damping, and slip prevention.