A granular jamming based hollow variable stiffness structure with adjustable local hardness

Abstract

As an effective variable stiffness method, jamming structures are widely used in soft robots. Based on the principle of granular jamming, a hollow variable stiffness bellows structure with adjustable local hardness is proposed in this paper. It is prepared by wax-lost casting with Ecoflex 0030 silica gel material, and glass balls with different diameters are used as filling particles. We make use of the Ogden model to simulate the silica gel and establish a finite element model for simulation experiments. The results show that the mechanism has a good effect on variable stiffness while the stiffness of the mechanism can be increased by 380% by applying negative pressure. Also, the integral stiffness can be significantly adjusted, while the local surface remains soft. In addition, the influence of structural parameters on the stiffness variation performance of the jamming mechanism is investigated.