Maker Faire 2013
At the 2013 Bay Area Maker Faire, PR2Lite took on
Maxwell and Michael Ferguson in a robot vs. robot battle
of chess (Figure 9). Michael and Maxwell are the 2011
champions of the AAAI small manipulator chess challenge.
Michael also wrote a series on Maxwell in the April,
May, and June 2012 issues of SERVO Magazine. Both
robots were running different variations of the same code.
The Kinect was used to identify where black or white
pieces were located and whether the pieces were moved.
GNUChess was used to implement the rules of chess,
validate legal moves, and track which pieces were where.
Finally, PR2Lite used ROS Electric-based arm navigation
while Maxwell used the recently released MoveIt! for ROS
Maxwell was a formidable opponent, and played an
excellent game of chess. PR2Lite tried hard, and provided
entertainment when it didn’t work. One time, it accidentally
picked up its king on its first move, and mistakenly resigned
by dropping the king off the table.
FIGURE 8. A screenshot of the GUI, meant to be compatible with
tablets and laptops. Thanks Patrick Goebel (Pi Robot)!
PR2Lite continues to evolve. Powerful MX64 and
MX106 servos and a Velo gripper courtesy of Willow
Garage will soon replace the AX-12s in one of its arms
(Figure 10). In addition, the arm planning will eventually
use MoveIt!. To extend mobility time, we plan to replace its
current battery-draining computer and its DC to AC
converter with powerful laptops.
PR2Lite has now reached the level of maturity that
applications developed for PR2 can be adapted for its own
use. Prior PR2 hackathons have demonstrated keyboard
playing and drawing capabilities that look like good
potential initial candidates. Also, the new HBRC floorbot
challenge is intriguing. Information and the latest updates
are available at http://mattdowning.wordpress.
Only five years ago, it was inconceivable that a hobbyist
robot this advanced could be built mainly by high school
students for price tag significantly lower than a Nao or
Darwin humanoid robots. Now, you can build your own
PR2 too! SV
FIGURE 9. PR2Lite (right) plays Michael
Ferguson's Maxwell (left) in chess at the
2013 Bay Area Maker Faire in San Mateo, CA.
FIGURE 10. A Velo
courtesy of Willow
Garage next to our
(right). The Velo is
already larger than
the current gripper,
and it will be even
bigger and heavier
38 SERVO 08.2013