Java Reference
In-Depth Information
The robot maintains an internal representation of the operational envi-
ronment in the form of a spatial lattice as depicted in Figure 10.4. In the
robotics literature this is called an “occupancy grid” and consists of a matrix
of cells, where each cell stores the state of a corresponding rectangular area
of the environment. A cell could be occupied by an obstacle (shown in
black), free of obstacles (light grey), or not yet explored (dark grey).
Figure 10.4 represents the case of an obstacle (the polygon with black
boundaries) partially seen by the laser range finder. The black cells repre-
sent the obstacle's boundary sensed by the laser.
It is easy to update this representation with sensory measures acquired by
a laser range finder or a set of sonars. The main drawback is the poor reso-
lution of the obstacle description. The width of each cell is the result of a
tradeoff between precision and computational complexity. We assume that
each cell has a width of 10 cm. The robot uses its internal representation of
the operational environment to plan its next moves. It always plans paths
that avoid the known obstacles. It chooses the next position within the
known region in such a way that it can sense the presence of obstacles in the
unknown region.
10.1.5
Simulation
The aim of this case study is to develop a software application that simulates
the behaviour of the mobile robot and its interaction with the external
`
MAP
p
`
OBSTACLE NAME
#
"Wall-A" OPAQUE
#
"false"
p
`
POINT X
#
"10" Y
#
"10"/
p
`
POINT X
#
"30" Y
#
"10"/
p
`
POINT X
#
"30" Y
#
"60"/
p
`
POINT X
#
"10" Y
#
"60"/
p
`
/OBSTACLE
p
`
OBSTACLE NAME
#
"Door-A" OPAQUE
#
"true"
p
`
POINT X
#
"15" Y
#
"60"/
p
`
POINT X
#
"25" Y
#
"60"/
p
`
POINT X
#
"25" Y
#
"110"/
p
`
POINT X
#
"15" Y
#
"110"/
p
`
/OBSTACLE
p
`
OBSTACLE NAME
#
"Wall-B" OPAQUE
#
"false"
p
`
POINT X
#
"10" Y
#
"110"/
p
`
POINT X
#
"30" Y
#
"110"/
p
`
POINT X
#
"30" Y
#
"160"/
p
`
POINT X
#
"10" Y
#
"160"/
p
`
/OBSTACLE
p
`
OBSTACLE NAME
#
"Wall-C" OPAQUE
#
"false"
p
`
POINT X
#
"70" Y
#
"40"/
p
`
POINT X
#
"120" Y
#
"40"/
p
`
POINT X
#
"120" Y
#
"100"/
p
`
POINT X
#
"100" Y
#
"100"/
p
`
POINT X
#
"120" Y
#
"60"/
p
`
POINT X
#
"100" Y
#
"60"/
p
`
/OBSTACLE
p
`
/MAP
p
Figure 10.5
The XML file that describes the simulated environment and its visualization
