Page 308 - Concise Encyclopedia of Robotics

Sound Transducer
What makes bats so adept at using sonar? For one thing, they have a
brain. It follows that artificial intelligence (AI) must be an important part
of any advanced robotic sonar system. The computer must analyze the
incoming pulses in terms of their phase, the distortion at the leading and
trailing edges, and whether or not the returned echoes are bogeys (illusions
or false echoes).
For good image resolution, the sonar beam must be as narrow as
possible, and it must be swept around in two or three dimensions. With
optimum direction resolution and distance resolution, a sonar can make a
computer map of a robot’s work environment. Compare LADAR and RADAR.
See also COMPUTER MAP, DIRECTION RESOLUTION, DISTANCE RESOLUTION, and RANGE
SENSING AND PLOTTING.
SOUND TRANSDUCER
A sound transducer, also called an acoustic transducer, is an electronic
component that converts acoustic waves into some other form of energy, or
vice versa.The other form of energy is usually an alternating-current (AC)
electrical signal. The waveforms of the acoustical and electrical signals are
identical, or nearly so.
Acoustic transducers are designed for various frequency ranges. The
human hearing spectrum extends from about 20 Hz to 20 kHz, but
acoustic energy can have frequencies lower than 20 Hz or higher than 20
kHz. Energy at frequencies below 20 Hz is called infrasound; if the fre-
quency is above 20 kHz, it is ultrasound. In acoustic wireless devices, ul-
trasound is generally used, because the wavelength is short and the
necessary transducers can be small. Also, ultrasound cannot be heard,
and therefore it does not distract or annoy people.
Sound transducers are used in security systems. They are also used in
robotics to help mobile machines navigate in their surroundings.
Acoustic transducers are employed in depth-finding apparatus commonly
found on boats.
See also DYNAMIC TRANSDUCER, ELECTROSTATIC TRANSDUCER, and PIEZOELECTRIC
TRANSDUCER.
SPATIAL RESOLUTION
Spatial resolution is a quantitative measure of the detail with which a robot
can define its work environment.It can be expressed in meters,centimeters,
millimeters, or micrometers (units of 10 6 m). In some precision robots,
it may be expressed in nanometers (units of 10 9 m). This measure can
refer to either of two quantities:
• The smallest linear distance between two points that the robot can
differentiate

