A sensory system that receives information about the
body and the surrounding environment
A power source to activate the muscles and sensors
system that processes sensory information and tells the
muscles what to do
Of course, we also have some intangible attributes, such as
intelligence and morality, but on the sheer physical level,
the list above about covers it.
A robot is made up of the very same components. A typical
robot has a movable physical structure, a motor of
some sort, a sensor system, a power supply and a computer
"brain" that controls all of these elements. Essentially,
robots are man-made versions of animal life -- they are
machines that replicate human and animal behavior.
In this edition of HowStuffWorks,
we'll explore the basic concept of robotics and find out how
robots do what they do.
What is a Robot? Joseph Engelberger, a
pioneer in industrial robotics, once remarked "I can't define
a robot, but I know one when I see one." If you consider all
the different machines people call robots, you can see that
it's nearly impossible to come up with a comprehensive
definition. Everybody has a different idea of what constitutes
You've probably heard of several of these famous robots:
R2D2 and C-3PO: The intelligent, speaking robots with
loads of personality in the Star
A robotic dog that learns through human interaction
A robot that can walk on two legs like a person
Industrial robots: Automated machines that work on
All of these things are considered robots, at least by some
people. The broadest definition around defines a robot as
anything that a lot of people recognize as a robot. Most
roboticists (people who build robots) use a more precise
definition. They specify that robots have a reprogrammable
brain (a computer) that moves a body.
By this definition, robots are distinct from other movable
machines, such as cars, because of their computer element.
Many new cars do have an onboard
computer, but it's only there to make small adjustments.
You control most elements in the car directly by way of
various mechanical devices. Robots are distinct from ordinary
computers in their physical nature -- normal computers don't
have a physical body attached to them.
In the next section, we'll look at the major elements found
in most robots today.
Robot Basics The vast majority of robots do
have several qualities in common. First of all, almost all
robots have a movable body. Some only have motorized wheels,
and others have dozens of movable segments, typically made of
metal or plastic. Like the bones in your body, the individual
segments are connected together with joints.
Photo courtesy NASA A robotic hand, developed by NASA, is made up
of metal segments moved by tiny motors. The hand is one
of the most difficult structures to replicate in
spin wheels and pivot jointed segments with some sort of
actuator. Some robots use electric
motors and solenoids
as actuators; some use a hydraulic
system; and some use a pneumatic system (a system driven
by compressed gases). Robots may use all these actuator types.
A robot needs a power source to drive these actuators. Most
robots either have a battery or
they plug into the wall. Hydraulic robots also need a pump to
pressurize the hydraulic fluid, and pneumatic robots need an
air compressor or compressed air tanks.
The actuators are all wired to an electrical
circuit. The circuit powers electrical motors and
solenoids directly, and it activates the hydraulic system by
manipulating electrical valves. The valves determine
the pressurized fluid's path through the machine. To move a
hydraulic leg, for example, the robot's controller would open
the valve leading from the fluid pump to a piston
cylinder attached to that leg. The pressurized fluid would
extend the piston, swiveling the leg forward. Typically, in
order to move their segments in two directions, robots use pistons
that can push both ways.
The robot's computer controls everything attached to the
circuit. To move the robot, the computer switches on all the
necessary motors and valves. Most robots are
reprogrammable -- to change the robot's behavior, you
simply write a new program to its computer.
Not all robots have sensory systems, and few have the
ability to see, hear, smell or taste. The most common robotic
sense is the sense of movement -- the robot's ability to
monitor its own motion. A standard design uses slotted wheels
attached to the robot's joints. An LED on one
side of the wheel shines a beam of light through the slots to
a light sensor on the other side of the wheel. When the robot
moves a particular joint, the slotted wheel turns. The slots
break the light beam as the wheel spins. The light sensor
reads the pattern of the flashing light and transmits the data
to the computer. The computer can tell exactly how far the
joint has swiveled based on this pattern. This is the same
basic system used in computer
These are the basic nuts and bolts of robotics. Roboticists
can combine these elements in an infinite number of ways to
create robots of unlimited complexity. In the next section,
we'll look at one of the most popular designs, the robotic
The Robotic Arm The term robot comes from
the Czech word robota, generally translated as
"forced labor." This describes the majority of robots fairly
well. Most robots in the world are designed for heavy,
repetitive manufacturing work. They handle tasks that are
difficult, dangerous or boring to human beings.
Robotic arms are an essential part of car
The most common manufacturing robot is the robotic
arm. A typical robotic arm is made up of seven metal
segments, joined by six joints. The computer controls the
robot by rotating individual step motors connected to
each joint (some larger arms use hydraulics or pneumatics).
Unlike ordinary motors, step motors move in exact increments
(check out this
site to find out how). This allows the computer to move
the arm very precisely, repeating exactly the same movement
over and over again. The robot uses motion sensors to make
sure it moves just the right amount.
An industrial robot with six joints closely resembles a
human arm -- it has the equivalent of a shoulder, an elbow and
a wrist. Typically, the shoulder is mounted to a stationary
base structure rather than to a movable body. This type of
robot has six degrees of freedom, meaning it can pivot
in six different ways. A human arm, by comparison, has seven
degrees of freedom.
Your arm's job is to move your hand from place to place.
Similarly, the robotic arm's job is to move an end
effector from place to place. You can outfit robotic arms
with all sorts of end effectors, which are suited to a
particular application. One common end effector is a
simplified version of the hand, which can grasp and carry
different objects. Robotic hands often have built-in
pressure sensors that tell the computer how hard the
robot is gripping a particular object. This keeps the robot
from dropping or breaking whatever it's carrying. Other end
effectors include blowtorches, drills and spray painters.
Industrial robots are designed to do exactly the same
thing, in a controlled environment, over and over again. For
example, a robot might twist the caps onto peanut butter jars
coming down an assembly line. To teach a robot how to do its
job, the programmer guides the arm through the motions using a
handheld controller. The robot stores the exact sequence of
movements in its memory, and does it again and again every
time a new unit comes down the assembly line.
Most industrial robots work in auto assembly lines, putting
cars together. Robots can do a lot of this work more
efficiently than human beings because they are so precise.
They always drill in the exactly the same place, and they
always tighten bolts with the same amount of force, no matter
how many hours they've been working. Manufacturing robots are
also very important in the computer industry. It takes an
incredibly precise hand to put together a tiny microchip.
The Czech playwright
Karel Capek originated the term robot in his 1920
play "R.U.R." In the play, machine workers overthrow
their human creators when a scientist gives them
emotions. Dozens of authors and filmmakers have
revisited this scenario over the years.
Isaac Asimov took a more optimistic view in several
novels and short stories. In his works, robots are
benign, helpful beings that adhere to a code of
nonviolence against humans -- the "Laws
Mobile Robots Robotic arms are relatively
easy to build and program because they only operate within a
confined area. Things get a bit trickier when you send a robot
out into the world.
Photo courtesy NASA NASA's FIDO
Rover is designed for exploration on
The first obstacle is to give the robot a working
locomotion system. If the robot will only need to move over
smooth ground, wheels or tracks are the best option. Wheels
and tracks can also work on rougher terrain if they are big
enough. But robot designers often look to legs instead,
because they are more adaptable. Building legged robots also
helps researchers understand natural locomotion -- it's a
useful exercise in biological research.
Typically, hydraulic or pneumatic pistons move robot legs
back and forth. The pistons attach to different leg segments
just like muscles
attach to different bones. It's a real trick getting all these
pistons to work together properly. As a baby, your brain had
to figure out exactly the right combination of muscle
contractions to walk upright without falling over. Similarly,
a robot designer has to figure out the right combination of
piston movements involved in walking and program this
information into the robot's computer. Many mobile robots have
a built-in balance system (a collection of gyroscopes,
for example) that tells the computer when it needs to correct
Photo courtesy NASA NASA's Frogbot uses springs, linkages and
motors to hop from place to
Bipedal locomotion (walking on two legs) is inherently
unstable, which makes it very difficult to implement in
robots. To create more stable robot walkers, designers
commonly look to the animal world, specifically insects.
Six-legged insects have exceptionally good balance, and they
adapt well to a wide variety of terrain.
Some mobile robots are controlled by remote -- a human
tells them what to do and when to do it. The remote control
might communicate with the robot through an attached wire, or
using radio or infrared
signals. Remote robots, often called puppet robots,
are useful for exploring dangerous or inaccessible
environments, such as the deep sea or inside a volcano.
Some robots are only partially controlled by remote. For
example, the operator might direct the robot to go to a
certain spot, but not steer it there -- the robot would find
its own way.
What is it Good
stand in for people in a number of ways. Some explore
other planets or inhospitable areas on Earth, collecting
geological samples. Others seek out landmines
in former battlefields. The police sometimes use mobile
robots to search for a bomb, or even to apprehend a
Mobile robots also work in homes and businesses.
Hospitals may use robots to transport medications. Some
museums use robots to patrol their galleries at night,
monitoring air quality and humidity levels. Several
companies have developed robots that will vacuum your
house while you sleep.
Autonomous Mobility Autonomous robots
can act on their own, independent of any controller. The basic
idea is to program the robot to respond a certain way to
outside stimuli. The very simple bump-and-go robot is a
good illustration of how this works.
This sort of robot has a bumper sensor to detect obstacles.
When you turn the robot on, it zips along in a straight line.
When it finally hits an obstacle, the impact pushes in its
bumper sensor. The robot's programming tells it to back up,
turn to the right and move forward again, in response to every
bump. In this way, the robot changes direction any time it
encounters an obstacle.
Photo courtesy NASA The Urbie
is an autonomous robot designed for various urban
operations, including military reconnaissance and
Advanced robots use more elaborate versions of this same
idea. Roboticists create new programs and sensor systems to
make robots smarter and more perceptive. Today, robots can
effectively navigate a variety of environments.
Simpler mobile robots use infrared or ultrasound sensors to
see obstacles. These sensors work the same way as animal
echolocation: The robot sends out a sound signal or a beam
of infrared light and detects the signal's reflection. The
robot locates the distance to obstacles based on how long it
takes the signal to bounce back.
More advanced robots use stereo vision to see the
world around them. Two cameras give these robots depth
perception, and image-recognition software gives them the
ability to locate and classify various objects. Robots might
also use microphones
sensors to analyze the world around them.
Some autonomous robots can only work in a familiar,
constrained environment. Lawn-mowing robots, for example,
depend on buried border markers to define the limits of their
yard. An office-cleaning robot might need a map of the
building in order to maneuver from point to point.
More advanced robots can analyze and adapt to
unfamiliar environments, even to areas with rough terrain.
These robots may associate certain terrain patterns with
certain actions. A rover robot, for example, might construct a
map of the land in front of it based on its visual sensors. If
the map shows a very bumpy terrain pattern, the robot knows to
travel another way. This sort of system is very useful for
exploratory robots that operate on other planets (check out this
page to learn more).
An alternative robot design takes a less structured
approach -- randomness. When this type of robot gets
stuck, it moves its appendages every which way until something
works. Force sensors work very closely with the actuators,
instead of the computer directing everything based on a
program. This is something like an ant trying to get over an
obstacle -- it doesn't seem to make a decision when it needs
to get over an obstacle, it just keeps trying things until it
gets over it.
Homebrew Robots In the last couple of
sections, we looked at the most prominent fields in the world
of robots -- industry robotics and research robotics.
Professionals in these fields have made most of the major
advancements in robotics over the years, but they aren't the
only ones making robots. For decades, a small but passionate
band of hobbyists has been creating robots in garages and
basements all over the world.
Homebrew robotics is a rapidly expanding subculture with a
sizable Web presence. Amateur roboticists cobble together
their creations using commercial robot kits, mail
order components, toys and even old VCRs.
Homebrew robots are as varied as professional robots. Some
weekend roboticists tinker with elaborate walking machines,
some design their own service bots and others create
competitive robots. The most familiar competitive robots are
remote control fighters like you might see on "BattleBots."
These machines aren't considered "true robots" because they
don't have reprogrammable computer brains. They're basically
souped-up remote control
More advanced competitive robots are controlled by
computer. Soccer robots, for example, play miniaturized soccer
with no human input at all. A standard soccer bot team
includes several individual robots that communicate with a
central computer. The computer "sees" the entire soccer field
with a video
camera and picks out its own team members, the opponent's
members, the ball and the goal based on their color. The
computer processes this information at every second and
decides how to direct its own team.
Adaptable and Universal The personal
computer revolution has been marked by extraordinary
adaptability. Standardized hardware and programming languages
let computer engineers and amateur programmers mold computers
to their own particular purposes. Computer components are sort
of like art supplies -- they have an infinite number of uses.
Most robots to date have been more like kitchen appliances.
Roboticists build them from the ground up for a fairly
specific purpose. They don't adapt well to radically new
This situation may be changing. A new company called Evolution
Robotics is pioneering the world of adaptable robotics
hardware and software. The company hopes to carve out a niche
for itself with easy-to-use "robot developer kits."
The kits come with an open software platform tailored to a
range of common robotic functions. For example, roboticists
can easily give their creations the ability to follow a
target, listen to voice commands and maneuver around
obstacles. None of these capabilities are revolutionary from a
technology standpoint, but it's unusual that you would find
them in one simple package.
The kits also come with common robotics hardware that
connects easily with the software. The standard kit comes with
infrared sensors, motors, a microphone and a video camera.
Roboticists put all these pieces together with a souped-up
erector set -- a collection of aluminum body pieces and sturdy
These kits aren't your run-of-the-mill construction sets,
of course. At upwards of $1,000, they're not cheap toys. But
they are a big step toward a new sort of robotics. In the near
future, creating a new robot to clean your house or take care
of your pets while you're away might be as simple as writing a
BASIC program to balance your checkbook.
The Future: AI Artificial
intelligence (AI) is arguably the most exciting field in
robotics. It's certainly the most controversial: Everybody
agrees that a robot can work in an assembly line, but there's
no consensus on whether a robot can ever be intelligent.
term "robot" itself, artificial intelligence is hard to
define. Ultimate AI would be a recreation of the human thought
process -- a man-made machine with our intellectual abilities.
This would include the ability to learn just about anything,
the ability to reason, the ability to use language and the
ability to formulate original ideas. Roboticists are nowhere
near achieving this level of artificial intelligence, but they
have had made a lot of progress with more limited AI. Today's
AI machines can replicate some specific elements of
Computers can already solve problems in limited
realms. The basic idea of AI problem-solving is very simple,
though its execution is complicated. First, the AI robot or
computer gathers facts about a situation through sensors or
human input. The computer compares this information to stored
data and decides what the information signifies. The computer
runs through various possible actions and predicts which
action will be most successful based on the collected
information. Of course, the computer can only solve problems
it's programmed to solve -- it doesn't have any generalized
analytical ability. Chess
computers are one example of this sort of machine.
Some modern robots also have the ability to learn in
a limited capacity. Learning robots recognize if a certain
action (moving its legs in a certain way, for instance)
achieved a desired result (navigating an obstacle). The robot
stores this information and attempts the successful action the
next time it encounters the same situation. Again, modern
computers can only do this in very limited situations. They
can't absorb any sort of information like a human can. Some
robots can learn by mimicking human actions. In Japan,
roboticists have taught a robot to dance by demonstrating the
Some robots can interact socially. Kismet, a robot
Artificial Intelligence Lab, recognizes human body
language and voice inflection and responds appropriately.
Kismet's creators are interested in how humans and babies
interact, based only on tone of speech and visual cue. This
low-level interaction could be the foundation of a human-like
Kismet and other humanoid robots at the M.I.T. AI Lab
operate using an unconventional control structure. Instead of
directing every action using a central computer, the robots
control lower-level actions with lower-level computers. The
program's director, Rodney Brooks, believes this is a more
accurate model of human intelligence. We do most things
automatically; we don't decide to do them at the highest level
The real challenge of AI is to understand how natural
intelligence works. Developing AI isn't like building an artificial
heart -- scientists don't have a simple, concrete model to
work from. We do know that the brain
contains billions and billions of neurons, and that we think
and learn by establishing electrical connections between
different neurons. But we don't know exactly how all of these
connections add up to higher reasoning, or even low-level
operations. The complex circuitry seems incomprehensible.
Because of this, AI research is largely theoretical.
Scientists hypothesize on how and why we learn and think, and
they experiment with their ideas using robots. Brooks and his
team focus on humanoid robots because they feel that being
able to experience the world like a human is essential to
developing human-like intelligence. It also makes it easier
for people to interact with the robots, which potentially
makes it easier for the robot to learn.
Just as physical robotic design is a handy tool for
understanding animal and human anatomy, AI research is useful
for understanding how natural intelligence works. For some
roboticists, this insight is the ultimate goal of designing
robots. Others envision a world where we live side by side
with intelligent machines and use a variety of lesser robots
for manual labor, health care and communication. A number of
robotics experts predict that robotic evolution will
ultimately turn us into cyborgs -- humans integrated with
machines. Conceivably, people in the future could load their
minds into a sturdy robot and live for thousands of years!
In any case, robots will certainly play a larger role in
our daily lives in the future. In the coming decades, robots
will gradually move out of the industrial and scientific
worlds and into daily life, in the same way that computers
spread to the home in the 1980s.
The best way to understand robots is to look at specific
designs. The links on the next page will show you a variety of
robot projects around the world.