Can Collecting Module
for the DPRG
CanCan Competition

David P. Anderson

LegoBot with Arm and Cow-catcher, for collecting empty soda cans
Click on images to enlarge.

The Dallas Personal Robotics Group (DPRG) have a contest in which a robot must identify and collect 6 randomly placed empty soda cans. My SR04 robot has won this contest a number of times by identifying the cans with sonar, navigating to each can, grasping it with a gripper, and returning it to the starting place (15 Mb mpg). For the legobot to accomplish the same tasks, I utilized the robot's wall-following behavior. (See the legobot homepage for more on wall and perimeter following behavior). A lightweight styrofoam "sweeper arm" was added to the left side of the robot. It is attached with a lego block and suspended from the far end with a guy-wire, and sweeps the floor. The sweeper arm is 32 inches long and legobot is 9 wide inches, making a total "robot width" of 41 inches, well within the DPRG 48 inch limit.

The strategy is just to follow the right wall around the perimeter of the DPRG "T" course and try to drag along any cans we can sweep up (this doesn't get any contest points for identifying or counting the cans). After some experimentation, two further refinements were added. A diagonal cardboard "cow-catcher" was added to the front of the robot to scrape cans over toward the arm. And double-side-sticky-tape was added to the front of the arm, to restrain the captured cans when the robot turns the corners.

Here is a video of legobot collecting all six randomly placed cans. The method for placing the cans is to toss them in the air and set them up where they land. At the contest they sometimes have a child from the audience do this. In this video the arrangement of cans was such that the cardboard "cow-catcher" on the front of the robot did not come into play until the very end of the contest course.

You get extra points if the robot can stop when it finishes the contest. Legobot can normally do this by using it's odometry (location) to tell it when it is back at the start. For some reason this won't work with the sweeper arm attached. I think the drag of the arm and cans, while it is neatly compensated for by the wall-following servo behavior, is nonetheless causing the odometry to get off. So the robot doesn't know when it is back at the starting place, and so it keeps going. At any rate, in this video, the hand of the creator reaches in and shuts the robot off when the contest is completed.
Legobot running the DPRG CanCan contest

full res mpeg (20 Mb)
real media .rm (9.6 Mb)
low res mpeg (6.5 Mb)
widows wmv (1,5 Mb)

Legobot won 2nd Place at the DPRG RoboRama CanCan Competition held at The Science Place in Fair Park in downtown Dallas, April 3rd, 2004.

Return to LegoBot's Homepage
Return to My Robot's Homepage

04 April 2004