Page 285 - Introduction to AI Robotics

268
The Hybrid Deliberative/Reactive Paradigm
7
The table below summarizes AuRA in terms of the common components
and style of emergent behavior:
AuRA Summary
Sequencer Agent Navigator, Pilot
Resource Manager Motor Schema Manager
Cartographer Cartographer
Mission Planner Mission Planner
Performance Monitoring Agent Pilot, Navigator, Mission Planner
Emergent behavior Vector summation, spreading activation
of behaviors, homeostatic control

7.4.2 Sensor Fusion Effects (SFX)

Another managerial style of architecture is the Sensor Fusion Effects (SFX)
architecture, which started out as an extension to AuRA by Murphy to in-
corporate pathways for sensing. The extension was to add modules to spec-
ify how sensing, including sensor fusion and handling sensor failures, are
handled. Over time, SFX has reorganized both the reactive and deliberative
components of AuRA although the two architectures remain philosophically
identical. SFX is an example of how robustness can be built into an architec-
ture. SFX has been used on eight robots for indoor office navigation, outdoor
road following, and urban search and rescue.
Fig. 7.4 shows a neurophysiological model of sensing based on studies
with sensing in cats. The model suggests that sensory processing is initially
local to each sensor, and may have its own sensor-dependent receptive field.
This is consistent with reactive robot behaviors, and at least with the mo-
tivation for sensor fission. Sensor processing then appears to branch, with
duplicates going to the superior colliculus (a mid-brain structure responsible
for motor behaviors) and the other to the cerebral cortex (responsible for more
cognitive functions). The branching allows the same sensor stream to be
used simultaneously in multiple ways. In SFX, the equivalent superior col-
liculus functions are implemented in the reactive layer, and cortical activities
in the deliberative layer. Branching of perception is done through the use
of whiteboards, common in numerous AI systems as global cognitive data
structures.
The deliberative component is divided into modules or object classes, each
of which is actually a software agent, a self-contained software program
which specializes in some area of competence and can interact with other