Hybrid Jamming Variable-Stiffness Link for Safe Co-Robots

Abstract

Stiff robots lead to high injury severity when there is an impact between a robot and an operator. Introducing controllable compliance into robotic links reduces the severity of impact and enables safe human-robot interaction. Layer jamming, airtight chamber, and shape morphing are effective variable-stiffness mechanisms. This paper proposes a hybrid jamming mechanism for safe human-robot interaction that combines the above three mechanisms to further improve stiffness changing performance. The hybrid jamming mechanism is composed of two thin sheets which can be multilayered and an air bladder is placed in between the two sheets; inflating the air bladder increases the curvature of the layers and the cross-section area, hence increasing the stiffness. System stiffness is further increased by increasing the pressure since all layers are compressed firmly. The concept is validated by quasi-static cantilever bending experiments. The measurements show that a maximum stiffness ratio of 66 can be achieved.