Page 153 - Introduction to AI Robotics

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4 The Reactive Paradigm

Figure 4.19 Khepera in a box canyon a.) range readings and b.) vectors from each
instance of Runaway (gray) and the summed output vector.

The alternative to multiple instantiation is to have the perceptual schema
for RUNAWAY process all 8 range readings. One approach is to sum all 8 vec-
tors internally. (As an exercise show that the resulting vector is the same.)
This is not as elegant from a software engineering perspective because the
PROCEDURAL code is now specific to the robot (the function is said to have procedural co-
COHESION hesion), 122 and can be used only with a robot that has eight range sensors at
those locations. Another approach, which produces a different emergent be-
havior, is to have the perceptual schema return the direction and distance of
the single largest range reading. This makes the behavior more selective.

4.4.7 Pfields compared with subsumption
How can simple behaviors form a more complicated emergent behavior? The
same way more complicated potential fields are constructed from primitive
fields: combining multiple instantiations of primitive behaviors. This can be