Description and execution of manipulation and locomotion by a humanoid robot using cascaded contact states graph

For a humanoid robot, both locomotion and object manipulation include contact state changes between the robot, an object, and an environment. It is important for the humanoid's controller system to know the actual contact states. In this paper, we propose a method to describe and execute humanoid's behavior including both object manipulation and locomotion by focusing on contact states. We represent contact states transition as a graph. We utilize Robot-Environment (RE) contact states for locomotion graph and Robot-Object (RO) and Object-Environment (OE) contact states for object manipulation graph. We construct humanoid's behavior by cascading a locomotion graph and a manipulation graph. By using cascaded graph description, we can use the same methods to observe contact states, execute motions autonomously, and recover from errors regardless of whether the current behavior is locomotion or object manipulation. Finally, we evaluate our proposed system through the experiments in which a life-sized humanoid performs 3D climbing and manipulation of an object with an unknown mass.