Page 131 - Designing Autonomous Mobile Robots : Inside the Mindo f an Intellegent Machine
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Chapter 7
Route planning by force fields
Another popular approach is based on calculating imaginary repelling fields emanat-
ing from obstacles as shown in Figure 7.5. The fields can diminish linearly with
distance or geometrically. The process typically yields a path that stays as far away
from obstacles as possible. Limits are normally placed on the range of the field ef-
fects, so that calculations do not need to include distant objects.
In order to visualize this process, it helps to imagine the resulting map as a landscape
where the obstacles are ridges or peaks, and the most likely routes follow the valleys
(Figure 7.6). The floor of a valley occurs where two or more force fields cancel each
other and the height of a valley floor is equal to the magnitude of the canceling
fields. The path planner is allowed to route the robot through a valley as long as its
height is below a minimum. This minimum corresponds to the clearance of the
vehicle.
Goal
Obstacle
Obstacle
Obstacle
Start
Figure 7.5. Force fields for path planning
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