Robot Replugged

Eight months ago, we were excited to share with you Milestone 2 footage of our PR2 Alpha plugging itself into a wall outlet to charge. The one-armed robot used a spiraling technique to slowly locate the outlet before plugging into the wall. With the completion of Milestone 3, the release of ROS 1.0, and the production of our first Beta robots, we realized that we could greatly improve the robot's plugging capabilities.

A team of five engineers spent the first two weeks of February improving the plugging-in software, enabling the PR2 to perform more efficiently and gracefully.  Instead of spiraling to find the outlet, the PR2 can now reliably locate the outlet with its cameras and plug in directly.

Numerous improvements to ROS made this possible in such a short timeframe and with so few people. During Milestone 3, we released 29 ROS stacks at 1.0 status, which gave the team a more stable and capable platform. These stacks included improved action, controller, and image libraries that were important for this effort. Milestone 3 also yielded easy-to-use, system-wide calibration, which provided the extra accuracy needed to eliminate the spiraling technique.

The new PR2 Betas are also much improved over their one-armed, Milestone 2 predecessors. During Milestone 2, we used the PR2's head-mounted camera and tilting laser to detect the outlet and plug. The PR2s now have a complete sensor package, including a head-mounted texture projector and two forearm cameras.

With these upgrades, the PR2 can find the wall using the texture projector, detect its plug using the left forearm camera, detect the outlet using the right forearm camera, and plug straight into the wall using the right gripper. Milestone 3 kept us pretty busy these past eight months, and we're glad to see how much of a difference this work has made.