PR2's Fine Motor Skills

Before making the final design revisions for our PR2 robot, we wanted to make sure that we had fully tested the capabilities of our PR2 alpha prototypes.  One of the things we needed to verify was if the robot can easily manipulate small objects and perform basic household tasks. Our first challenge in setting up this test was creating a teleoperation station that could control the many degrees of freedom of our robot, from the four caster wheels on the base to the position of the arms to the opening and closing of the grippers.

Last December we created our first rudimentary teleoperation rig, which used our Phasespace motion capture system to move around the arm of the robot. As you can see in the video of that first test, that setup required us to sit inside of a motion capture cage and didn't give us any control over the base or gripper -- and the robot only had one arm. After testing various setups with special gloves, we came up with a new, simplified rig: we shrunk the motion-capture cage down to a single, portable bar, and we glued the motion-capture LEDs onto two salad tongs, one for each arm. We found the cheap salad tongs to be precise, light, and easy to manipulate. In order to control the wheels and and the grippers, we added a set of flight simulator pedals in front of the operator.

With our new setup, we could now test the robot in various parts of our building.  First, we made sure that the robot could pick up and manipulate various office items, like pencils, pens, binders, and textbooks.  In our building's kitchenette, we made sure the robot could easily interact with cabinets and drawers, as well as common appliances like our refrigerator, microwave, and dishwasher.  We were even able to try some two-handed tasks, like folding a towel and opening a water bottle.

Although the PR2 did quite well with all the functional verification tests, there's still a lot of work to be done before the PR2 can perform these tasks without a human operator.  Hopefully, with help from our collaborators and the open-source community, we can make this a reality.

 --  Vijay Pradeep