Page 89 - Concise Encyclopedia of Robotics

Direction Finding
fool the circuit into thinking the signal is high when it is actually low; but
overall, errors are less frequent with DSP than without it.
In computers and robots
A DSP system can be etched onto a single integrated circuit (IC), similar
in size to a memory chip. Some DSP circuits serve multiple functions in
a computer or robotic system, so the controller can devote itself to doing
its primary work without having to bother with extraneous tasks.
A DSP chip can compress and decompress data, help a computer
recognize and generate speech, translate from one spoken language to
another (such as from English to Chinese or vice versa), and recognize
and compare patterns.
See also DATA CONVERSION.
DIRECTIONAL TRANSDUCER
A directional transducer is a device that senses some effect or disturbance,
and produces an output signal that varies in amplitude depending on the
direction from which the effect or disturbance arrives. Directional trans-
ducers are used extensively in robotic sensing and guidance systems.
A simple example of a directional transducer is a common microphone.
Microphones are almost always unidirectional, that is, they respond best
in one direction. An example of a bidirectional transducer is a horizontal
radio antenna known as a dipole. Some transducers are omnidirectional in
a specified plane. A vertical radio antenna is an example. It works equally
well in all horizontal directions. However, its sensitivity varies in vertical
planes.Some transducers are equally sensitive in all possible directions; the
directional pattern for such a device is a sphere in three dimensions. This
is a truly omnidirectional transducer.
DIRECTION FINDING
Direction finding is a means of location and/or navigation, usually employ-
ing radio or acoustic waves. At radio frequencies (RF), location and
navigation systems operate between a few kilohertz and the microwave
region. Acoustic systems use frequencies between a few hundred hertz
and a few hundred kilohertz.
Signal comparison
A mobile robot can find its position by comparing the signals from two
fixed stations whose positions are known,as shown in Fig.1.By adding 180°
to the bearings of the sources X and Y, the robot (square) obtains its bear-
ings as “seen”from the sources (dots).The robot can determine its direction
and speed by taking two readings separated by a certain amount of time.
Computers can assist in precisely determining,and displaying,the position
and the velocity vector.

