Amplifying Laminar Jamming for Soft Robots by Geometry-Induced Rigidity

Variable stiffness technology is an extensively discussed topic in soft robotics, which can bridge the traditional fast, precise and high-force rigid robots with compliant, agile, and safe soft robots. In this paper, we introduce the concept of geometry-induced rigidity and propose a variable curvature jamming (VCJ) mechanism for amplifying the laminar jamming structures which are fast, efficient, low cost, easy control, and very versatile in stiffness modulation applications. By adjusting the cross sectional curvature of the laminar jamming structures, and coupling with the vacuum jamming, the initial compliant laminar structures can stiffen notably. The bidirectional stiffness behaviors of the VCJ actuators with different design parameters are experimentally studied and analyzed. The results show that the transverse curvature can remarkably enhance the stiffness and load capacity of the actuators, about 3 folds in stiffness change than the laminar jamming mechanism. The VCJ actuator can even bear 10.85-kg weight which is about 1700 times of its own weight at its rigid state. And it can be operated in three stiffening modes with different degrees of variable stiffness performance. Moreover, the proposed VCJ mechanism is compatible with all existing laminar jamming designs, which provide an effective design method for building soft actuators and soft robots with excellent variable stiffness performance and load capacity.