Page 23 - Introduction to AI Robotics

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ROBOT PRIMITIVES INPUT OUTPUT Part I

SENSE Sensor data Sensed information

Information (sensed
PLAN Directives
and/or cognitive)

Sensed information Actuator commands
ACT
or directives

Figure I.2 Robot primitives defined in terms of inputs and outputs.

SENSING in that case processing is local to each function. Other paradigms expect
ORGANIZATION IN all sensor information to be first processed into one global world model
ROBOT PARADIGMS
and then subsets of the model distributed to other functions as needed.

Overview of the Three Paradigms
In order to set the stage for learning details, it may be helpful to begin with
a general overview of the robot paradigms. Fig. I.3 shows the differences
between the three paradigms in terms of the SENSE, PLAN, ACT primitives.
HIERARCHICAL The Hierarchical Paradigm is the oldest paradigm, and was prevalent from
PARADIGM 1967–1990. Under it, the robot operates in a top-down fashion, heavy on
planning (see Fig. I.3). This was based on an introspective view of how peo-
ple think. “I see a door, I decide to head toward it, and I plot a course around
the chairs.” (Unfortunately, as many cognitive psychologists now know, in-
trospection is not always a good way of getting an accurate assessment of
a thought process. We now suspect no one actually plans how they get out
of a room; they have default schemas or behaviors.) Under the Hierarchical
Paradigm, the robot senses the world, plans the next action, and then acts
(SENSE, PLAN, ACT). Then it senses the world, plans, acts. At each step,
the robot explicitly plans the next move. The other distinguishing feature of
the Hierarchical paradigm is that all the sensing data tends to be gathered
into one global world model, a single representation that the planner can use
and can be routed to the actions. Constructing generic global world models