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The big robot people believe that the robot should understand its environment and "think," more or less the same way that a human does. This is the traditional Artificial Intelligence (AI) approach
to robotics. In this approach, the robot takes input from its sensors and tries to build a map of its surroundings. This process alone is very complicated: the robot might use a pair of video cameras
or some more exotic sensors to examine its surroundings, while heavy-duty computers analyze all the sensor data and attempt to build a map. Finally, in a process called task planning, the robot
tries to figure out how it will accomplish an objective—getting from one point to another, or picking up an object, or some other simple task. In this respect, again, the robot is expected to think
like a human being. The heavy computing requirements of the AI approach consume a lot of power, which
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implies a bulky, heavy power supply. Hence, the robot can be pretty big—and expensive, too.
He Ain't Heavy, He's My Robot
A good example of the "big iron" approach to mobile robots is Ambler, developed by
Carnegie Mellon University and the Jet Propulsion Laboratory. This behemoth stands about
5m (16.4ft) tall, is up to 7m (23.0ft) wide, and weights 2500 kg (5512 lb). It moves at a
blistering 35 cm (13.8 in) per minute. Just sitting still, it consumes 1400 W of power. Ask it
to walk and it sucks up just about 4000 W. You can see a photograph of Ambler at
http://
ranier.oact.hq.nasa.gov/telerobotics_page/Photos/Ambler.jpg.
Small Is Beautiful
Little robot people like to tease the big robot people for building tremendously large, tremendously expensive machines that don't have the dexterity of a six-month-old baby. The little robot
people make small mobile robots based around inexpensive, off-the-shelf parts. They like to see themselves as mavericks, achieving decent results at a fraction of the cost and complexity of big
robotics.
One of the interesting ideas behind small robot research is the idea that quantity might get the job done rather than quality. Instead of building a single bulky, complex robot to explore the surface
of Mars, why not send a thousand robots the size of mice to do the same job? So what if a few of them fail? Small robots offer a new and innovative way to approach big problems.
The small robotics approach reduces the number of engineers you need in your basement. It makes robotics accessible to sophisticated hobbyists—people with technical knowledge and some extra
time and money. If you take the small robot approach, you'll probably use standard batteries for power, which eliminates the need for a chemical engineer to design a power supply. Small robots
are usually based on an existing, cheap microprocessor, which makes the electrical engineer's job a little easier. But you still need quite a bit of expertise:
• The electrical engineer still has to select sensors and actuators and wire them to the microprocessor. These parts are inexpensive and can be bought from hobby stores or electronics part stores.
• The computer programmer still needs a pretty low-level understanding of the microprocessor and the attached sensors and actuators.
• You still need a mechanical engineer to design the robot's body.
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The sophisticated hobbyist can do all of these things alone. But you have to be determined and have a lot of free time and money. There are a couple of ways to make things easier:
• You could buy a prebuilt robot brain. Some companies sell kits that are designed specifically to be used as robot brains. This approach saves you the trouble of selecting a microprocessor and
getting it running, but you still have to select sensors and actuators and attach them to the brain somehow.
• You could use a modular construction kit to build the robot's body. LEGO
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bricks are one possibility—in fact, researchers and students at the Massachusetts Institute of Technology (MIT) have
been using LEGO bricks for mechanical prototyping for over a decade.
An even better simplication, of course, is the MINDSTORMS

Robotics Invention System itself.
What Is Mindstorms?