Granular jamming for soft robotics: experiments and modelling of cyclic loading

Abstract The rapid development of research on innovative soft robots has been observed in recent years. Most of these robots are equipped with mechanisms that enable adaptive stiffness changes. Although various physical effects facilitate this capability, one of the most intriguing is undoubtedly the granular jamming phenomenon. Structures based on this effect consist of granules enclosed within an elastomer sleeve, with stiffness controlled by vacuum pressure. This work focuses on investigating the properties of such structures subjected to cyclic loading under different stress states. We conducted a wide range of empirical tests under various loading conditions, including compression, tension, and bending. Based on this research, a constitutive equation was proposed to describe this phenomenon. The model was implemented into commercial finite element (FE) software, and numerical predictions were validated with empirical results. Finally, a new concept for a soft robotic gripper utilizing granular jamming as a stiffening mechanism was proposed and tested.