Page 96 - Introduction to AI Robotics

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3.3 Coordination and Control of Behaviors
with predator movement) or a group of neurons which do the equivalent of
a computer algorithm.
Another important point about IRMs is that the releaser can be a compound
COMPOUND RELEASERS of releasers. Furthermore, the releaser can be a combination of either external
(from the environment) or internal (motivation). If the releaser in the com-
pound isn’t satisfied, the behavior isn’t triggered. The pseudo-code below
shows a compound releaser.
enum Releaser={PRESENT, NOT_PRESENT};
Releaser food;
while (TRUE)
{
food = senseFood();
hungry = checkState();
if (food == PRESENT && hungry==PRESENT)
feed();
}

The next example below shows what happens in a sequence of behaviors,
where the agent eats, then nurses its young, then sleeps, and repeats the
IMPLICIT CHAINING sequence. The behaviors are implicitly chained together by their releasers.
Once the initial releaser is encountered, the first behavior occurs. It executes
for one second (one “movement” interval), then control passes to the next
statement. If the behavior isn’t finished, the releasers remain unchanged and
no other behavior is triggered. The program then loops to the top and the
original behavior executes again. When the original behavior has completed,
the internal state of the animal may have changed or the state of the environ-
ment may have been changed as a result of the action. When the motivation
and environment match the stimulus for the releaser, the second behavior is
triggered, and so on.

enum Releaser={PRESENT, NOT_PRESENT};
Releaser food, hungry, nursed;
while (TRUE) {
food = sense();
hungry = checkStateHunger();
child = checkStateChild();
if (hungry==PRESENT)
searchForFood(); //sets food = PRESENT when done
if (hungry==PRESENT && food==PRESENT)
feed(); // sets hungry = NOT_PRESENT when done