We built a few add-ons for the iRobot Create to allow it be used as a drop-in replacement for more expensive robots in the ROS framework.
The iRobot Create has a few mounting holes on the back side of it. I designed a lasercut wooden box that bolts to these holes, and has mount points for the other stuff we need.
There are just a few parts to lasercut:
The forward-facing webcam mount needs to be fixed (see photo above), but would be easy to do. CAD for Solidworks 2008, as well as a DXF of the layout, are here: irobot-create-fitpc2.zip.
I made a silly little PCB which plugs directly into the iRobot Create's DB25 “open interface” connector. It holds a 15-watt +12V DC-DC module and does USB-serial conversion (using the great FTDI 232R chip). This just saves space and cleans things up a bit.
(Joint work with Jim Lin.) The idea is for the robot to be cheap. As a result, we are using the ARToolKit package to recognize fiducials (letter-size printouts of Chinese characters) taped to the ceiling of our lab.
However, robots with only ceiling cameras can't sense obstacles until they hit them with their bumpers. So, we are using a two-phase approach: first, a robot equipped with both a ceiling-mounted camera and a laser scanner creates a map of obstacles and walls in the environment, annotated with the positions of the ceiling-mounted fiducials. Then, this map can be used to localize robots equipped only with ceiling-mounted cameras.
The robot carries around a Fit-PC2 computer, which runs the Intel Atom (netbook) processor in a single-board form factor. It runs Ubuntu with no problems. You can buy it from Amazon; they're $350 or so.