Jammkle: Fibre jamming 3D printed multi-material tendons and their application in a robotic ankle

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.