Enhanced Aerial Reorientation Performance Using a 3-DoF Morphable Inertial Tail Inspired by Kangaroo Rats

Animal motion has been a source of inspiration for enhancing robot maneuverability. Kangaroo rats rely on aerial reorientation during evasive leaps to evade snake predation. They rapidly swing their tails to reorient their bodies over two full rotations around the yaw direction. Robotic tails for aerial reorientation have been widely researched. However, their aerial reorientation performances remained constrained by the tail's limited range of motion (RoM). Here, we take inspiration from kangaroo rat tail motion during evasive jumps, where the rat bends and twists its tail to bypass the body on the ventral side, accompanied by a large change in the distance between the tail's center of mass and the tail base. This behavior enables continuous tail swings, making larger changes in body yaw direction than possible with a single tail stroke. We propose utilizing the tail's spatial morphable inertia property (adjustable tail length) in two tail motion patterns (tail bypass barrier motion pattern (TBBMP) and tail reposition motion pattern (TRMP)) to enable a larger robot reorientation angle. We proposed a novel 3-DoF morphable inertial tail with rapid response and integrated it into a robot platform for experimental validation. Analysis, simulation, and experimental results validated that the proposed approach effectively enhanced the robot's aerial reorientation capabilities.