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Robotics Via
Remote Control
The typical amateur robot is
completely autonomous; its own
circuitry controls what it does and
where it goes. That circuitry can be as
simple as moving toward a light in the
room, or as complex as carefully
mapping and navigating the room
using vision and other sensors.
Yet, there is also plenty of call for
the remotely controlled robot. Such
“telerobotics” are commonly used for
police and military functions, and the vast
majority of combat robots are, in fact,
controlled directly by human operators.
The remote control link is typically via
radio frequency, but other means of
communications are used as well, such
as infrared pulses and even hard-wiring.
We’ll look at several popular
remote control techniques in this
installment of “Robotics Resources.”
Robot Radio Control
Radio control uses the airwaves to
send and receive a signal. Though
among the most expensive remote
control technologies to use, radio control
is perhaps the most flexible in terms
of range and the number of channels
that can be operated in one signal.
With the use of digital radio signals, for
example, it’s possible to communicate
a nearly unlimited set of instructions
between you and your robot.
Radio communications can be used
in robotics for two primary purposes:
1) To command the robot, either completely for all its discrete functions, or
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to provide general commands for
basic operations, such as Run or Stop.
General commands may also be used
to select and activate programs already
resident in the robot’s computer.
2) To receive data from the robot;
usually either a video signal or some
form of telemetry.
Radio links are common for
discrete function control in combat
robotics. The operator of the robot
uses a radio control (R/C) transmitter
of a type similar to those for model
airplanes and cars (most such transmitters are outfitted with a frequency
crystal for land use, rather than airplane
use). The operator controls joysticks
and/or switches in order to steer or
otherwise maneuver the robot.
Typical transmitters for model R/C
applications have four to six channels,
with each channel operated by the twin
joysticks, a switch, or other knob on the
transmitter. At a minimum, three channels are used: one each for the right and
left motors; and one for the weapon.
In some cases, it’s necessary to
receive signals from a robot. Video is
a typical application for receiving a
radio signal from a robot. Video
transmitters and receivers that operate
in the 2.4 GHz microwave range (such
as Bluetooth) are common and fairly
inexpensive. Range is limited to under
200 feet outdoors, or from 20 to 50
feet when used indoors.
When selecting a receiver and
transmitter for wireless data between
you and your robot, consider the
following:
• Power output determines range.
Depending on your country’s laws,
higher power outputs may require
certification of the device, or even
licensing. In the US, most wireless
data modems operate at a power
output that does not require licensing.
• Range contributes to maximum
data rate. Data rates can be fastest
over shorter distances, because the
received signal is clearer. Over longer
distances, the data rate must be
decreased in order to reduce or
eliminate errors.
• The right antenna can greatly
increase range. Radio frequency
signals radiating from a properly
designed and mounted antenna will
travel further than signals from a
transmitter without an antenna. Be
sure to use an antenna properly
matched for the transmitter you are
using — sometimes, it’s just a simple
wire, but consult the documentation
on how to position or wrap the wire.
• Use a compatible antenna on the
receiver. The same rules apply to the
receiver as to the transmitter. Be sure
to consider the orientation of the
antennas on the receiver and the
transmitter — if the units have stick
antennas, avoid having one point up
while the other points sideways.
