Animal and Robotic Locomotion on Dry and Wet Granular Media

Traditional wheeled robots struggle to traverse granular media such as sand or mud which has inspired the use of continuous tracks, legged, and various bio-inspired designs in recent robotics research. Animals can navigate the natural world with relative ease and one animal, the Basilisk lizard, can perform the amazing feat of bipedal water and land running. Through the observation and study of basilisk lizards of the common and plumed variety, inspiration and development of a robotic platform was completed. After fabricating the bio-inspired robot, parameters unchanged by the animals were varied to characterize the combined effects of stride length and frequency on average velocity. It was found that animals increased stride length at higher saturation levels of sand to increase their velocity rather than increase their step frequency. The BasiliskBot version one was unable to change its stride length as the wheel-legs or "whegs" of this version were set at four spokes. Bipedal running of the robot was slower than quadrupedal running due to sand reaction forces and tail drag. BasiliskBot version two was lighter than the first version and had a range of stride lengths tested with increasing spoke numbers from 3-7. At lower step frequencies and lower wheg numbers, higher average velocity could be achieved compared to higher wheg numbers despite the highest maximum velocity being achieved by the highest number of spokes. A comparison of transition strategies for common and plumed basilisks showed both species chose to jump and swim through water more often than jump and run across water which achieved the highest average velocity. Results of transition strategies study pertain to future developments of the robot for amphibious purposes. Weight experiments were performed to assess the ability of the robot to carry sensors and other payloads. Added weight increased the highest frequency allowable before failure, but also caused failure at low step frequencies that had not displayed failure previously.