Page 185 - Introduction to AI Robotics

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5 Designing a Reactive Implementation
IV
SAND PIT
FINISH
START

I
III

II

Milestone (red bale)
Rock (white bale)
Obstacle (white bale)

Figure 5.5 The course for the 1994 Ground Robotics Competition.

with a 0.5 ft tolerance. This eliminated the need for an avoid obstacle behavior.
The analysis of the environment also identified an affordance for controlling the
robot. The only object of interest to the robot was the white line, which should have
a high contrast to the green (dark gray) grass. But the exact lighting value of the
white line changed with the weather. However, if the camera was pointed directly
at one line, instead of trying to see both lines, the majority of the brightest points
in the image would belong to the line (this is a reduction in the signal to noise ratio
because more of the image has the line in it). Some of the bright points would be due
to reflections, but these were assumed to be randomly distributed. Therefore, if the
robot tried to keep the centroid of the white points in the center of the image, it would
stay in the center of the lane.
Step 4: Describe how the robot should act in response to its environ-
ment. The purpose of this step is to identify the set of one or more candidate
primitive behaviors; these candidates will be refined or eliminated later. As
the designer describes how the robot should act, behaviors usually become
apparent. It should be emphasized that the point of this step is to concen-