Layer jamming: Modeling and experimental validation

Abstract

The ability to control and tune the stiffness of soft structures is one of the most important challenges in soft robotics. This is crucial in applications that require both compliance and the ability to withstand high forces. Among the various techniques, layer jamming represents a promising solution. Despite the increasing interest, the existing analytical models are not able to describe the behavior of these structures beyond the initial deformation phase. In this work, we propose an analytical model that predicts the behavior of these structures in all deformation phases, overcoming the limitations of existing models. Our previous approach is extended by explicitly taking into account the increase in stiffness due to the overhangs of the structure outside the constraining supports. We conduct experimental tests and finite element simulations to validate the predictions of the proposed model. The experimental and finite element results are in good agreement with theoretical predictions, especially considering that no fitting parameters have been used. Additionally, we analyze the effect of the main design parameters, including the number of layers, vacuum pressure and coefficient of friction, as well as the energy dissipated by friction during a load–unload cycle. We believe that this work represents a significant step forward in understanding the complex mechanisms underlying the mechanics of layer jamming structures that could be useful in helping researchers design more advanced variable stiffness applications in soft robotics.