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All robot systems operate in the physical world, and a robot controller
therefore must include some form of spatial representation, whether it is an
explicit description of object shapes and locations, or whether it is implicit
in a sequence of motions through space. The requirements of robot spatial
representations vary considerably in different applications, however - the
sophistication of spatial representations must increase as the robot
controller is required to perform more sophisticated tasks. The following list
presents the types of spatial representation facilities that are necessary to
carry out different levels of robot programming and control:
- Robot level programming does not assume that the robot has any
explicit knowledge about its surroundings. The shape of the objects
that the robot is operating on is, however, implicit (to some
extent) in the motions that the robot makes.
- Vision systems (those which perform object recognition, or scene
analysis) must have some explicit spatial representation, since all
visual processing operates on a two dimensional projection of the
physical subject.
- ``Hand-eye'' systems must be able to relate the description of an
object as it appears in the visual field to operations that the robot
will carry out in its workspace. This requires a spatial
representation which is more versatile than for vision alone.
- Systems in which object descriptions are directly created by a
programmer require that the description can be readily derived from
the programmer's own ``spatial representation'' - his concepts of
space and shape. At the same time, the robot controller must be
capable of relating the programmer's description both to features in
the visual field, and to actual movements. Representation facilities
like these are a requirement of task level programming.
- Where a robot is reasoning for itself in an environment that may
contain unknown objects, or unfamiliar arrangements of objects, it
must be able to use sensory data to construct a useful spatial
representation of its surroundings, so that it can plan and operate
in those surroundings.
- ``Robots'' that operate in a simulated world are of course particularly
dependent on the form in which the simulated world is represented,
since they do not interact with anything other than the
representation.
The remainder of this section discusses several approaches which have been
taken to space and shape representation in robotic systems. It includes
discussion of techniques that have been used in most of the above categories
of task, so that the capabilities of various general methods can be compared.
Next: Robot Motion Representation
Up: Spatial Representation and Reasoning
Previous: Survey of Robot Reasoning
Alan Blackwell
2000-11-17