Robophysical study of jumping dynamics on granular media

Fast locomotion is comprised of impulsive limb movements. In deformable media like water and sand, the forces generated from the material response to these movements greatly a↵ect locomotor performance of fast moving an-imals and robots. For example, when basilisk lizards run on water, reaction forces arise resulting from combinations of hydrostatic pressure, drag forces with quadratic velocity dependence and virtual mass forces that allow the lizard to stay afloat and propel forward. We are interested in understanding how such forces a↵ect fast movement on flowable terrestrial substrates like granular media. Characterization of these forces requires an understanding of the solid and fluid-like response of granular media. The most detailed studies of intrusion in dry granular media have revealed that interactions of fixed-shape objects during free vertical impact (e.g. cannonballs) [4, 9, 11, 3, 2, 5] and forced slow penetration [8] can be described by simple equations con-taining hydrostatic-like and hydrodynamic-like forces [7, 12, 13]. Here we investigate a new class of biologically [1] and robotically [10] relevant granu