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2: Saphira System Overview
TCP/IP link to
other agents
Agent
Interface
Display
routines
Global Map
Registration
routines
Local
Perceptual
Space
Procedural
Reasoning
System
Fuzzy control
Direct motion
control
Sensor interp
routines
State Reflector
Figure 2-2 Saphira Control Architecture.
The control architecture is a set of routines that interpret sensor readings
relative to a geometric world model, and a set of action routines that map
robot states to control actions. Registration routines link the robot’s local
sensor readings to its map of the world, and the Procedural Reasoning
System sequences actions to achieve specific goals. The agent interface links
the robot to other agents in the Open Agent Architecture.
2.2.1. Representation of Space
Mobile robots operate in a geometric space, and the representation of that space is critical to their
performance. There are two main geometrical representations in Saphira. The Local Perceptual Space
(LPS) is an egocentric coordinate system a few meters in radius centered on the robot. For a larger
perspective, Saphira uses a Global Map Space (GMS) to represent objects that are part of the robot’s
environment, in absolute (global) coordinates.
The LPS is useful for keeping track of the robot's motion over short space-time intervals, fusing sensor
readings, and for registering obstacles to be avoided. The LPS gives the robot a sense of its local
surroundings. The main Saphira interface window (Figure 2-2) displays the robot’s LPS. In local mode
(from the Display menu), the robot stays centered in the window, pointing up, and the world revolves
around it. Keeping the robot fixed in position makes it easy to describe strategies for avoiding obstacles,
going to goal positions, and so on.
Structures in the GMS are called artifacts, and represent objects in the environment or internal
structures, such as paths. A collection of objects, such as corridors, doors, and rooms, can be grouped
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