Validating Granular Scaling Laws for Wheel/Screw Geometries

Building and optimizing a design for deformable media can be extremely costly. However, granular scaling laws enable the ability to predict system velocity and mobility power consumption by testing at a smaller scale in the same environment. The validity of the granular scaling laws for arbitrarily shaped wheels and screws were evaluated in materials like silica sand and BP-1, a lunar simulant. Different wheel geometries, such as non-grousered and straight and bihelically grousered wheels were created and tested using 3D printed technologies. Using the granular scaling laws and the empirical data from initial experiments, power and velocity were predicted for a larger scaled version then experimentally validated on a dynamic mobility platform. Working with granular media has high variability in material properties depending on initial environmental conditions, so particular emphasis was placed on consistency in the testing methodology. Through experiments, these scaling laws have been validated with defined use cases and limitations.