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4 The Reactive Paradigm

Figure 4.23 The a.) perpendical and b.) uniform fields combining into c.) a
follow-corridor field.

The follow-corridor behavior is interesting, because it requires a more
complex potential field. As shown in Fig. 4.23, it would be desirable for
the robot to stay in the middle of the corridor. This can be accomplished
using two potential fields: a uniform field perpendicular to the left boundary
and pointing to the middle, and a uniform field perpendicular to the right
boundary and pointing to the middle. Notice that both fields have a linear
decrease in magnitude as the field nears the center of the corridor. In practice,
this taper prevents the robot from see-sawing in the middle.
Also notice that the two uniform fields are not sufficient because they do
not permit the robot to move forward; the robot would move to the middle
of the corridor and just sit there. Therefore, a third uniform field is added
which is parallel to the corridor. All three fields combined yield a smooth
field which sharply pushes the robot back to the middle of the corridor as a
function of its proximity to a wall. In the meantime, the robot is constantly
making forward progress. The figure below shows the fields involved. Re-