The picture above is an AARM Motion control system.
AARM stands for Advanced Architecture Robot and Machine Motion and it's
a commercial product from American Robot for industrial machine motion
control. Industrial controllers are either non-servos, point-to-point
servos or continuous path servos. A non-servo robot usually moves parts
from one area to another and is called a "pick and place" robot. The
non-servo robot motion is started by the controller and stopped by a
mechanical stop switch. The stop switch sends a signal back to the
controller which starts the next motion. A point-to-point servo moves to
exact points so only the stops in the path are programmed. A continuous
path servo is appropriate when a robot must proceed on a specified path
in a smooth, constant motion.
More sophisticated robots have more sophisticated
control systems. The brain of the Mars Sojourner rover was made of two
electronics boards that were interconnected to each other with Flex
cables. One board was called the "CPU" board and the other the "Power"
board and each contained items responsible for power generation, power
conditioning, power distribution and control, analog and digital I/O
control and processing, computing (i.e., the CPU), and data storage
(i.e., memory). The control boards for Sojourner are shown below. For
more info, visitRover Control and Navigation at
Mobile robots can operate by remote control or
autonomously. A remote control robot receives instructions from a human
operator. In a direct remote control situation, the robot relays
information to the operator about the remote environment and the
operator then sends the robot instructions based on the information
received. This sequence can occur immediately (real-time) or with a time
delay. Autonomous robots are programmed to understand their environment
and take independent action based on the knowledge they posess. Some
autonomous robots are able to "learn" from their past encounters. This
means they can identify a situation, process actions which have produced
successful/unsuccessful results and modify their behavior to optimize
success. This activity takes place in the robot controller.
The body of a robot is related to the job it must perform. Industrial
robots often take the shape of a bodyless arm since it's job requires it
to remain stationary relative to its task. Space robots have many
different body shapes such as a sphere, a platform with wheels or legs,
or a ballon, depending on it's job. The free-flying rover, Sprint
Aercam is a sphere to
minimize damage if it were to bump into the shuttle or an astronaut.
Some planetary rovers have
solar platforms driven by wheels to traverse terrestrial environments. Aerobot bodies
are balloons that will float through the atmosphere of other worlds
collecting data. When evaluating what body type is right for a robot,
remember that form follows function.
How do robots move? It all depends on the job they have to do and the
environment they operate in.
In the Water: Conventional
unmanned, submersible robots are used in science and industry throughout
the oceans of the world. You probably saw the Jason AUV
at work when pictures of the Titanic discovery
were broadcast. To get around, automated underwater vehicles (AUV's) use
propellers and rudders to control their direction of travel. One area of
research suggests that an underwater robot like RoboTuna could
propel itself as a fish does using it's natural undulatory motion. It's
thought that robots that move like fish would be quieter, more
maneuverable and more energy efficient.
Land based rovers can move around on legs, tracks or wheels. Dante
II is a
frame walking robot that is able to descend into volcano craters by
rapelling down the crater. Dante has eight legs; four legs on each of
two frames. The frames are separated by a track along which the frames
slide relative to each other. In most cases Dante II has at least one
frame (four legs) touching the ground. An example of a track driven
robot is Pioneer, a robot
developed to clear
rubble, make maps and acquire samples at the Chornobyl Nuclear Reactor
site. Pioneer is track-driven like a small bulldozer which makes it
suitable for driving over and through rubble. The wide track footprint
gives good stability and platform capacity to deploy payloads.
Many robots use wheels for locomotion. One of the
first US roving vehicles used for space exploration went to the moon on Apollo
15 (July 30, 1971) and was
driven by astronauts David R. Scott and James B. Irwin. Two other
Lunar Roving Vehicles (LRV) also went to the moon on Apollo 16 and 17.
These rovers were battery powered and had radios and antenna's just like
the Mars Pathfinder rover Sojourner. But unlike Sojourner, these rovers
were designed to seat two astronauts and be driven like a dune buggy.
The Sojourner rover's
wheels and suspension use a rocker-bogie system that is unique in that
it does not use springs. Rather, its joints rotate and conform to the
contour of the ground, which helps it traverse rocky, uneven surfaces.
Six-wheeled vehicles can overcome obstacles three times larger than
those crossable by four-wheeled vehicles. For example, one
side of Sojourner could tip as much as 45 degrees as it climbed over a
rock without tipping over. The wheels are 13 centimeters (5 inches) in
diameter and made of aluminum. Stainless steel treads and cleats on the
wheels provide traction and each wheel can move up and down
independently of all the others.
In the Air/Space:
Robots that operate in the air use engines and thrusters to get around.
One example is the Cassini,
an orbiter on it's way to Saturn. Movement
and positioning is accomplished by either firing small thrusters or by
applying a force to speed up or slow down one or more of three "reaction
wheels." The thrusters and reaction wheels orient the spacecraft in
three axes which are maintained with great precision. The propulsion
system carries approximately 3000 kilograms (6600 lbs) of propellant
that is used by the main rocket engine to change the spacecraft's
velocity, and hence its course. A total velocity change of over 2000
meters per second (6560 ft/s) is possible. In addition, Cassini will be
propelled on its way by two "gravity assist" flybys of Venus, one each
of Earth and Jupiter, and three dozen of Saturn's moon Titan. These
planetary flybys will provide twenty times the propulsion provided by
the main engine.
Deep Space 1 is
an experimental spacecraft of the future sent into deep space
to analyze comets and demonstrate new technologies in space. One of it's
new technologies is a solar electric (ion) propulsion engine that
provides about 10 times the specific impulse of chemical propulsion. The
ion engine works by giving an electrical charge, or ionizing, a gas
called xenon. The xenon is electrically accelerated to the speed of
about 30 km/second. When the xenon ions are emitted at such a high speed
as exhaust from the spacecraft, they push the spacecraft in the opposite
direction. The ion propulsion system requires a source of energy and for
DS1 the energy comes from electrical power generated by it's solar
Power for industrial robots can be electric, pneumatic or hydraulic.
Electric motors are efficient, require little maintenance, and aren't
very noisy. Pneumatic robots use compressed air and come in a wide
variety of sizes.
A pneumatic robot requires another source of energy such as electricity,
propane or gasoline to provide the compressed air. Hydraulic robots use
oil under pressure and generally perform heavy duty jobs. This power
type is noisy, large and heavier than the other power sources. A
hydraulic robot also needs another source of energy to move the fluids
through its components. Pneumatic and hydraulic robots require
maintenance of the tubes, fittings and hoses that connect the components
and distribute the energy.
Two important sources of electric power for mobile robots are solar
cells and batteries.
There are lots of types of batteries like carbon-zinc, lithium-ion, lead-acid,
nickel-cadmium, nickel-hydrogen, silver zinc and alkaline to name a few.
Battery power is measured in amp-hours which is the current (amp)
multiplied by the time in hours that current is flowing from the
battery. For example, a two amp hour battery can supply 2 amps of
current for one hour. Solar cells make electrical power from sunlight.
If you hook enough solar cells together in a solar panel you can
generate enough power to run a robot. Solar cells are also used as a
power source to recharge batteries.
space probes must use alternate power sources because beyond Mars
existing solar arrays would have to be so large as to be infeasible. The
lifespan of batteries is exceeded at these distances also. Power for
deep space probes is traditionally generated by radioisotope
thermoelectric generators or
RTGs, which use heat from the natural decay of plutonium to generate
direct current electricity. RTGs have been used on 25 space missions
Sensors are the perceptual
system of a robot and measure
physical quantities like contact, distance, light, sound, strain,
rotation, magnetism, smell, temperature, inclination, pressure, or
altitude. Sensors provide the raw information or signals that
must be processed through the robot's computer brain to provide
meaningful information. Robots are equipped with sensors so they can
have an understanding of their surrounding environment and make changes
in their behavior based on the information they have gathered.
Sensors can permit a robot to have an adequate field
of view, a range of detection and the ability to detect objects while
operating in real or near-real time within it's power and size limits.
Additionally, a robot might have an acoustic sensor to detect sound,
motion or location, infrared sensors to detect heat sources, contact
sensors, tactile sensors to give a sense of touch, or optical/vision
sensors. For most any environmental situation, a robot can be equipped
with an appropriate sensor. A robot can also monitor itself with
Big Signal robot NOMAD uses
sensing instruments like a camera, a spectrometer and a metal-detector.
The high resolution video camera can identify dark objects (rocks,
meterorites) against the white background of the Antarctic snow. The
variations in color and shade allow the robot to tell the difference
between dark grey rocks and shadows. Nomad uses a laser range finder to
measure the distance to objects and a metal detector to help determine
the composition of the objects if finds.
Very complex robots like Cassini have
full sets of sensing equipment much like human senses. It's skeleton
must be light and sturdy, able to withstand extreme temperatures and
monitor those temperatures. Cassini determines it's location by using
three hemisperical resonant gyroscopes or HRG's which measures quartz
crystal vibrations. The eyes of Cassini are the Imaging Science
Subsystem (ISS) which can take pictures in the visible range, the
near-ultraviolet and near-infrared ranges of the electromagnetic
As working machines, robots have defined job duties and carry all the
tools they need to accomplish their tasks onboard their bodies. Many
robots carry their tools at the end of a manipulator. The manipulator
contains a series of segments, jointed or sliding relative to one
another for the purpose of moving objects. The manipulator includes the
arm, wrist and end-effector. An end-effector is a tool or gripping
mechanism attached to the end of a robot arm to accomplish some task. It
often encompasses a motor or a driven mechanical device. An end-effector
can be a sensor, a gripping device, a paint gun, a drill, an arc welding
device, etc. There are many examples of robot tools that you will
discover as you examine the literature associated with this site. To get
you going, two good examples are listed below.
Tools are unique to the task the robot must perform. The
goal of the robot mission Stardust is to capture both cometary samples
and interstellar dust. The trick is to capture the high velocity comet
and dust particles without physically changing them. Scientists
developed aerogel, a silicon-based solid with a porous, sponge-like
structure in which 99.8 percent of the volume is empty space. When a
particle hits the aerogel, it buries itself in the material, creating a
carrot-shaped track up to 200 times its own length. This slows it down
and brings the sample to a relatively gradual stop. Since aerogel is
mostly transparent - with a distinctive smoky blue cast - scientists
will use these tracks to find the tiny particles.