One of the best known robots in the consumer space is iRobot's Roomba carpet and floor cleaner. It uses brushes instead of a vacuum to clean, but it does so automatically. The Roomba has been joined by the Scooba floor washer and the Dirty Dog, which has more powerful motors and better brushes that can even pick up small nuts and bolts. The Dirty Dog is designed for cleaning up workshops.
The Roomba platform is now available to robotic developers as well. The Roomba does have a serial interface, but the new iRobot Create (Fig. 1) provides an even better development platform, with space for custom peripherals and hardware. It definitely beats duct tape and Dremel tools. The Create also provides access to the on-board micrcontroller.
The Create retains the omnidirectional infrared sensor (Fig. 2) located at the front of the robot. This is used to detect its charging station (an optional item) and virtual walls, infrared transmitters that mark boundaries for the robot. A closeup look (Fig. 3) reveals the sensor's simplicity. Multiple sensors are located inside the robot, and this plastic light guide reflects infrared light from all around. This allows the robot to identify the direction of the light.
The infrared sensor is just one of 32 sensors built into the Create platform. The front cowl is actually a bump sensor that can indicate on which side a collision has occurred. This sensor only handles the front half of the round robot, but this is usually sufficient since the robot normally pivots or turns in a forward direction. It can move backwards, but most algorithms assume that the robot has moved forward into a collision, so it can usually back up a short distance and pivot to its heart's content.
The other sensors include downward-looking infrared sensors to detect a falloff — typically steps leading down, or very steep inclines. Internal sensors include support for detecting battery charge levels and motor control.
The Create has a more robust traction system than the typical Roomba (Fig. 4). This helps the robot navigate over rougher terrain, but it is still an indoor robot that requires a relatively flat surface. It can handle surfaces such as concrete or even short grass, but the low clearance limits its mobility in more rugged environments. The wheel drive mechanisms are hinged, so there is some movement available should the robot navigate into an area that is not quite flat.
There is a non-traction balance wheel under the front of the Create (Fig. 5), and a slightly smaller one can be added to the back. These wheels simply turn and pivot in response to movements initiated by the pair of drive wheels.
The first major change to the Create, as compared to the Roomba, is the cargo area in the rear of the robot (Fig. 6). It has removable panels and numerous threaded mounting holes for adding custom equipment. About a third of the volume in the Create is available for flush mounting of external hardware. Of course, rising above the Create is an option, but it can often be a requirement. Limits tend to be power, weight, and center of gravity.