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5.5 Assemblages of Behaviors
Recall also in the serial program implementations of IRMs in Ch. 3 that the
agent “noticed” releasers every second. At one iteration through the loop,
it might be hungry and “enter” the state of feeding. In the next iteration, it
might still be hungry and re-enter the state of feeding. This can be repre-
sented by having arrows starting at the feeding state and pointing back to
the feeding state.
For the example in Fig. 5.8, the robot starts in the state of following a line.
This means that the robot is not prepared to handle a visual distraction (range
near) until it has started following a line. If it does, the program may fail be-
cause the FSA clearly shows it won’t respond to the distraction for at least
one update cycle. By that time, the robot may be heading in the wrong direc-
tion. Starting in the following-line state fine for the UGR competition, where
it was known in advance that there were no bales of hay near the starting
line. A more general case is shown in Fig. 5.9, where the robot can start ei-
ther on a clear path or in the presence of a bale. The FSA doesn’t make it
clear that if the robot starts by a bale, it better be pointed straight down the
path!
The fourth piece of information that a designer needs to know is when the
robot has completed the task. Each state that the robot can reach that termi-
FINAL STATE nates the task is a member of the set of final state, F. In the UGR example,
the robot is never done and there is no final state—the robot runs until it is
turned off manually or runs out of power. Thus, both states are final states.
If the robot could recognize the finish line, then it could have a finish state.
The finish state could just be stopped or it could be another behavior, such
as a victory wag of the camera. Notice that this adds more rows to the FSA
table, since there must be one row for each unique state.
In many regards, the FSA table is an extension of the behavioral table.
The resulting table is known as a finite state machine and abbreviated M for
machine. The notation:

M = fK; ; ; g s ; F

is used as reminder that in order to use a FSA, the designer must know all
the q states (K), the inputs the transitions between the states ,the special
starting state q 0 , and the terminating state(s) (F). There must be one arrow
in the state diagram for every row in the table. The table below summarizes
the relationship of FSA to behaviors: