Squirrel-inspired Tendon-driven Passive Gripper for Agile Landing

Squirrels exhibit agile leaping between tree branches, often using non-prehensile gripping with compliant and passively adaptive fingers. We aim to test the utility of such gripping in agile robotic maneuvering. In the present study, we first examine the parametric design of a squirrel-inspired underactuated gripper for passive landing on impact. We fix the geometry of the gripper and vary the joint stiffness and contact conditions. We find that stiffer fingers with soft foam pads enlarge the landing sufficiency region. Specifically, friction appears to enlarge horizontal error tolerance, while joint stiffness and pad damping allow for higher impact speeds. Thus, these features should be considered in the design of future agile robot hands and feet that include high impact landings on rods with pose inaccuracy.