Page 41 - Concise Encyclopedia of Robotics

Biased Search
such as a photocell. The distance to each mirror can be determined by the
time required for the flash to travel to the mirror and return to the robot.
Because this delay is an extremely short interval of time, high-speed
measuring apparatus is needed.
An example of an active beacon is a radio transmitter. Several trans-
mitters can be put in various places, and their signals synchronized so that
they are all exactly in phase.As the robot moves around, the relative phase
of the signals varies. Using an internal computer, the robot can determine
its position by comparing the phases of the signals from the beacons.
With active beacons, the robot does not need a transmitter, but the
beacons must have a source of power and be properly aligned.
See also ARTIFICIAL STIMULUS.
BEHAVIOR
In robotics, behavior refers to the processing of sensor data into specific
motions, sequences of motions, or tasks. There are three main types:
reflexive behavior, reactive behavior, and conscious behavior.
Reflexive behavior is the simplest and fastest form of robotic behavior.
Sensors can be, and often are, connected directly to manipulators, propul-
sion systems, or other mechanical devices. An electric eye that triggers an
intrusion alarm is a good example of a device that employs reflexive behav-
ior. When the light beam is broken, an electric current is interrupted, and
this actuates an electronic switch that applies power to an acoustic emitter.
Reactive behavior involves a primitive sort of machine intelligence;
the extent or nature of the action varies over a range that depends on one
or more parameters in the work environment. An example of reactive
behavior is the operation of a back pressure sensor, in which the amount
of torque applied by a robotic arm or end effector varies depending on
the mechanical resistance offered by the manipulated object.
Conscious behavior involves artificial intelligence (AI), in which a
robot controller performs complex tasks such as playing chess or making
choices that depend on multiple factors that cannot be predicted.
BIASED SEARCH
A biased search is an analog method by which a mobile robot can find a
destination or target, by first looking off to one side and then “zeroing in.”
The illustration shows a biased-search scheme that a boater might use
on a foggy day. At some distance from the shoreline, the boater cannot
see the dock, but has a reasonably good idea of where it is. Therefore, an
approach is deliberately made well off to one side (in this case, to the left)
of the dock.When the shore comes into view, the boater turns to the right
and follows it until the dock is found.

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