Steering of an Underactuated Legged Robot through Terrain Contact with an Active Tail

Abstract

This paper analyzes and implements two novel turning strategies for underactuated legged robots that leverage contact of an active tail against terrain. The first strategy produces a sustained turn with a tail dragging against the ground during forward locomotion. The second strategy produces a rapid point turn by impacting the tail against the ground. LoadRoACH, a 55 g palm-sized legged robot, is developed to carry the active tail payload used in turning experiments. A steady-state turning model predicts the achievable turn speed of the robot on carpet, and open-loop turning experiments characterize the performance of the two tail contact turning strategies. Tail drag turning provides comparable turning maneuverability to differential drive turning gaits on carpet and gravel surfaces. Tail impact turning can produce rapid point turns on carpet, tarp, and gravel, but has a large variability in turn angle and time to recover from the turn. Finally, tail drag and tail impact turning control methods are implemented in an aggressive closed-loop corner steering maneuver.