The word robot comes from the
Czech word for forced labor, or serf. It was introduced
by playwright Karel Capek, whose fictional robotic
inventions were created by chemical and biological,
rather than mechanical, methods. Basically a robots
A mechanical structure, such
as a wheeled platform, arm, or other construction,
capable of interacting with its environment.
Sensors to sense the
environment and give useful feedback to the device.
Systems to process sensory
input in the context of the current situation and
instruct the device to perform actions in response
to the situation.
The robot structure consists basically of
the robot body that includes arms and wheels. Some force
such as electricity is required to make the arms and wheels
turn under command. One of the most interesting aspects
of robot in general is its behavior, which requires a
form of intelligence.
A variety of electric motors provide
power to robots, making them move with various
programmed motions. The efficiency rating of a motor
describes how much of the electricity consumed is
converted to mechanical energy.
DC motors. Permanent-magnet DC
motors require only two leads, and use an arrangement of
fixed- and electro-magnets (stator and rotor) and
switches. These form a commutator to create motion
through a spinning magnetic field.
AC motors. These motors cycle the
power at the input-leads, to continuously move the
Stepping motors. They are like a
brushless DC or AC motor. They move the rotor by
applying power to different magnets in the motor in
sequence (stepped). Stepping motors are designed for
fine control and will not only spin on command, but can
spin at any number of steps-per-second (up to their
Servomotors. Servos are simple DC
motors with gearing and a feedback control system. They
adjust themselves until they match the signal. Servos
are used in radio control airplanes and cars.
More About Motors
Gears and chains.
Gears and chains are mechanical parts that provide a
mechanism to transmit rotational motion from one place to another
possibly of changing it along the way. The speed change
between two gears depends on the number of teeth on
belts. Pulleys and belts, two other simple machines
used in robots, work the same way as gears and chains.
Pulleys are wheels with a groove around the edge, and
belts are the rubber loops that fit in that groove.
A gearbox operates on the same principles as the
gear and chain, without the chain. Examples of
gearboxes are found on the transmission in a car and the
paper-feed of a printer.
Robots operate according to a basic
measurement, requiring different kinds of sensors. A
sense of time is usually built-in through perceptual
hardware and software, which updates quickly.
Sensors interact with external environment and
transforms the energy associated with what is being
measured (sound, light, pressure, temperature, etc.)
into another form of energy. Common sensors used in
robotics include light sensors, touch sensors,
sound sensors, and acceleration sensor.
sound sensor is installed at the ear position of the
robot in order to detect the voice of a subject. An
acceleration sensor is installed in the body to
detect shaking. A touch sensor is installed in the
forehead of the robot to detect touch
In general, power supply is provided by
two types of sources: batteries that are used once only
and then discarded; and rechargeable batteries that
operate from a reversible chemical reaction and can be
recharged thousand times. The first use of a
rechargeable battery gives up to 4 hours of continuous
operation in an application.
There are two main systems to control
robots: logic circuit and a microcontroller.
A digital logic circuit controls the
mechanical system. The circuit is usually coupled to the
mechanical structure through a bridge relay. A
control signal generates a magnetic field in the relay's
coil that mechanically closes a switch. transistors, for
example, are good silicon switches, available in many
technologies to control the mechanical systems.
Microcontrollers are intelligent
electronic devices that are used inside robots. They
deliver functions similar to those performed by a
microprocessor (CPU) inside a personal computer.
Microcontrollers are slower and have less memory than
CPUs, but are designed for real-world control problems.
One of the major differences between CPUs and
microcontrollers is the number of external components
needed to operate them. Microcontrollers may run with no
external parts, and typically need only an external
crystal or oscillator.
There are three main characteristics of a
microcontroller for consideration: speed, size, and
memory. Speed is designated in clock cycles, and
is usually measured in millions of cycles per second
(Megahertz, MHz). Size specifies the number of
bits of information the Microcontroller can process in
one step (for example, 4-, 8-, 16-, and 32-bits).
Microcontrollers count most of their read-only memory
in thousands of bytes (kB) and random access memory
in single bytes.
Connection to Math