Collision Detecting and Arm Planning

Ioan Sucan is headed back to Rice University after his third stay here at Willow Garage. Ioan is a motion planning researcher and is the author of Open Motion Planning Library (OMPL), a library of sampling-based motion planning algorithms. These algorithms are important for the PR2 because they enable the arm to grasp and manipulate objects, while simultaneously avoiding collisions with people and other still or moving objects.

This past winter, Ioan and Radu Rusu used OMPL to do dynamic collision avoidance. This summer, Ioan was able to make many improvements to OMPL so that the PR2 can grasp and manipulate objects in cluttered indoor environments. In the video, you can see how the PR2 is able to grasp objects while moving its arm through complex obstacle courses. Data from the tilting laser scanner is used to construct and update a 3D-representation of the environment, allowing the arm to avoid even moving obstacles.

Ioan also improved the robot_self_filter and the collision_map. When the PR2's arm moves in front of the sensors, two problems occur: the arm looks like an obstacle in the environment, and the arm blocks the robot's view of the environment behind the arm. The robot_self_filter, in combination with the collision_map, allows the PR2 to disregard its arm as an obstacle, and "remember" objects behind the arm.

Here are the slides from Ioan's end-of-summer presentation describing his work on OMPL and other projects.

Ioan Sucan: Motion Planning for the PR2 Arm on Scribd (Download PDF from