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4 The Reactive Paradigm

Figure 4.24 Selective attraction field, width of 45 .

An interesting aspect of the docking behavior is that the robot is operating
in close proximity to the dock. The dock will also release an instance of avoid,
which would prevent the robot from getting near the desired position. In this
case, the docking behavior would lower the magnitude (gain) of the output
vector from an avoid instantiated in the dock area. Essentially, this partially
inhibits the avoid behavior in selected regions. Also, the magnitude or gain
can define the correct distance: the robot stops where the selective attraction
of the dock balances with the repulsion.
The selective and tangential fields are not sufficient in practice, because of
the limitations of perception. If the robot can’t see the dock, it can’t deploy
the fields. But an industrial robot might know the relative direction of a dock,
much as a bee recalls the direction to its hive. Therefore an attractive force
attracts the robot to the vicinity of the dock, and then when the robot sees
the dock, it begins the funnel effect into the correct position and orientation,
even in the presence of obstacles, as seen in Fig. 4.26.
At least three perceptual schemas are needed for the docking behavior.
One is needed to extract the relative direction of the dock for the regular
attraction. Another is a perceptual schema capable of recognizing the dock
in general, even from behind or the sides, in order to support the tangential
field. The third perceptual schema is needed for the selective attention field;
it has to be able to respond to the front of the dock and extract the robot’s
relative distance and orientation.
The docking behavior is now defined as having three perceptual schemas
and three motor schemas (they could be grouped into 3 primitive behaviors).
A schema-theoretic representation indicates that the behavior has some co-