Friction and damping of a compliant foot based on granular jamming for legged robots

Moving away from simple foot designs of current quadruped robots towards a more bio-inspired approach, a novel foot design was implemented on the quadruped robot Oncilla. These feet mimic soft paw-pads of dogs and cats with high traction and soft underlying tissue. Consisting of a granular medium enclosed in a flexible membrane, they can be set to different pressure/vacuum conditions. Tests of general properties such as friction force, damping and deformation were completed by proof of concept tests on the robot. These included flat ground locomotion as well as ascending a slope with different inclination. Comparison tests with the previous feet were performed as well, showing that the new feet have a high friction and strong damping properties. Additionally, the speed of flat ground locomotion is comparable to the maximum speed of the robot with the previous feet while retaining the desired trotting gait. These are promising aspects for legged locomotion. The jamming of granular media previously has been used to create a universal gripper which in the future also opens up opportunities to use the feet both in locomotion and simple object manipulation (although the manipulation is not tested here).