I am working on a "design guide" on how to build your own Linux PC Robot and I think something needs to be stated up front. This is not a "small robot." I have nothing against small robots like Lego NXT and Roombas, they are cool.
But the Linux PC Robot is built around a full desktop PC — an ATX motherboard, ATX power supply, full-size drive wheels, and a chassis large enough to hold all of it. It is not something that fits on your desk or that you can toss in a backpack. It is a floor-roaming machine that you step aside for when it comes toward you.
Why Big?
Size was a consequence of the design goal, not a design goal in itself. The choice to use a recycled desktop PC as the computing platform — for cost and capability reasons — determined most of the size constraints. An ATX board is roughly 12 × 9.6 inches. The power supply is another brick. Add motor mounting, wheels large enough to roll over typical indoor obstacles, and a stable wheelbase, and the robot ends up at a size where it can hold its own in a real room.
There is an upside to this: a larger robot can carry real payload. Cameras, laptops, sensor arrays, speakers, additional computers — there is room and power budget for all of it. Small robots are charming, but their payload capacity limits what you can actually do with them beyond following lines and avoiding walls.
Why Not a Roomba?
Consumer robots like the Roomba are excellent at their intended task: vacuuming floors. They are not designed as open development platforms. Their firmware is proprietary, their sensing is optimized for obstacle avoidance rather than navigation, and their computational resources are minimal. Hacking a Roomba for real robotics research is possible but fighting against the design.
The LPCR is designed from the ground up to be hacked. Every component is documented, every software layer is open, and the hardware is built from parts that any hardware store and electronics supplier can provide.
The Design Guide
The design guide mentioned above is still in progress. When complete it will document the chassis construction, electronics wiring, software installation, and PID tuning process in enough detail for someone to build their own LPCR from scratch. See Design Guide and Source Bundle Coming for more background.