Prophetic goal-space planning for human-in-the-loop mobile manipulation

This paper introduces the Prophetic Goal-Space Planner (PGP) system developed to accomplish mobile manipulation tasks. Goal-space planning exploits the under-constrained and variable nature of many real-world tasks by defining Cartesian goals in terms of intuitive solution manifolds (e.g., the principal axis of a cylindrical handle, the rim of a valve, the surface of a step) rather than precise points in 6-dimensional space. The PGP system combines 1) a goal-space planner, 2) a kinematic planner and visualizer called the prophet, and 3) user interface tools. The prophet determines appropriate stance locations for the robot to reach its goals and animates the result. The UI tools allow a human operator to either approve or reject the planner's output (the "prophecy"), request new plans, or adjust the goal-space target regions to better match the robot's perceived environment. The PGP system thus enables a level of shared autonomy between the robot and operator that can ensure task completion with only limited, corrective operator input. PGP was employed by Team TRACLabs on the Boston Dynamics Atlas robot for the DARPA Robotics Challenge (DRC) 2015 Finals. PGP enabled the efficient completion of multiple manipulation tasks, including opening and walking through a door, walking up to and turning a valve, and throwing a lever - despite degraded network communication channels - and contributed to TRACLabs' placing 9th out of 23 teams in the competition.