An Observation of Granular Locomotion with Bipedal Systems

Overview

Survey robots have become ever prominent in exploring extreme environments; however, limitations arise as they come across unpredictable granular terrains. Current literature examines granular intrusion forces; however, drag forces have yet to be studied. To address this issue, geometric intruders, similar to cleats, were intruded and dragged through a fluidized testing bed filled with poppy seeds to see if at least one variable had a significant impact in optimizing granular locomotion by reducing terrain disruption and granular forces. The variables tested were multi -body intruders with spacings of 1, 3, 5 centimeters (cm), time delays between intrusion and drag movements of 1, 3, 4, 30 seconds (s), and intruder materials of acrylonitrile butadiene styrene (ABS) and aluminum. All variable permutations had three trials, and the maximum intrusion and drag forces were recorded in Newtons (N). Results showed that ABS was preferred for reducing forces over aluminum in all scenarios, a 1-second delay was preferred for drag but a 4-second delay for intrusion, 5 cm spacings were preferred during intrusion, and 1 cm spacings during drag. All the variables tested had p-values of <0.001, suggesting all variables made statistically significant contributions to optimizing granular locomotion. Dur ing drag experimentation, hysteresis was observed as the first segment of the multi -body intruders left behind disturbed terrain for the second half to interact with, increasing the exerted forces. This suggests that smaller spacing intruders are ideal for drag movements as they reduce granular disruptions that could limit the applicability of previously developed predictive force models.