A Humanoid Soft Robotic Joint with Variable Stiffness

To meet the demand of human-robot interaction, a novel humanoid soft robotic joint was proposed by imitating the antagonistic structure of human elbow joint. The soft robotic joint consists of a serial elastic actuator (SEA) and a symmetrically-arranged elastic bands. The stiffness of the robotic joint can be adjusted actively by changing the length of the elastic bands, so as to achieve better compliance. The joint stiffness model is established to find out how the joint structure parameters affect the joint stiffness and how to adjust the joint stiffness to improve the compliance during human-robot interactions. The stiffness model is verified by conducting experiments on the soft robotic joint prototype. The results show that the soft robotic joint has a good position tracking performance and rapid response to stiffness step.