Using Discrete Element Method for Simulating Robotic Structures with Particle Jamming Characteristics

In this paper, we use the Discrete Element Method (DEM) to model the switchable stiffness behavior of components for robotic structures. These components are built-up with an elastic cover and a granular medium. By means of vacuum pressure, the jamming of the particles, and therefore the stiffness be-havior, can be adjusted. Aim of the model is to predict the structural behavior of such components considering size scaling effects. The model is compared to ex-perimental results of a bending test. Main challenges of using the DEM for such a configuration is the mapping of the elastic cover and the load application. The load application can be realized by coupling with a multibody dynamics system using the Functional Mock-up Interface. For mapping the cover, the elasticity has to be adjusted because of numerical discrepancies. The comparison with the ex-perimental results shows that the influence of the cover elasticity is negligibly small. The differences between simulation and experiment can be explained by the particle shape. To save computing time, sphere shapes are considered for the model, but the real particle shapes are sharp-edged polyhedrons. With the model the influence of parameters such as dimensions, filling degree and vacuum pres-sure can be determined.