Page 77 - Dynamic Vision for Perception and Control of Motion

3.2 A Framework for Capabilities 61

man language has special expressions for these capabilities of motion control,
which often are performed sub-consciously: They are called maneuvers and have a
temporal extension in the seconds-to-minutes range.
Other control activities are done to maintain an almost constant state relative to
some desired one, despite unforeseeable disturbances encountered. These are
called regulatory control activities, and there are terms in human language describ-
ing them. For example, “lane keeping” when driving a road vehicle is one such ac-
tivity where steering wheel input is somehow linked to road curvature, lateral off-
set, and yaw angle relative to the road. The speed V driven may depend on road
curvature since lateral acceleration depends on V²/R, with R the radius of the curve.
When driving on a straight road, it is therefore also essential to recognize the onset
of a beginning curvature sufficiently early so that speed can be reduced either by
decreasing fuel injection or by activating the brakes. The deceleration process takes
time, and it depends on road conditions too [dry surface with good friction coeffi-
cient or wet (even icy) with poor friction]. Vision has to provide this input by con-
centrating attention on the road sections both nearby and further away. Only
knowledgeable agents will be able to react in a proper way: They know where to
look and for what (which types of features yield reliable and good hints). This ex-
ample shows that there are situations where a more extended task context has to be
taken into account to perform the vision task satisfactorily.
Another example is given in
Figure 3.1. If both vehicles have
just a radar (or laser) sensor on
board, which is not able to rec-
ognize the road and lane
boundaries, the situation per-
ceived seems quite dangerous.
Two cars are moving toward Figure 3.1. Judgment of a situation depends on
each other at high speed (shown the environmental context and on knowledge
by the arrows in front) on a about behavioral capabilities and goals
common straight line.
Humans and advanced tech-
nical vision systems seeing the S-shaped road curvature conclude that the other ve-
hicle is going to perform lane keeping as an actual control mode. The subject vehi-
cle doing the same will result in no stress and a harmless passing maneuver. The
assumption of a suicidal driver in the other car is extremely unlikely. This shows,
however, that the decision process from basic vision “here and now” to judgment
of a situation and coming up with a reasonable or optimal solution for one’s own
behavior may be quite involved. Intelligent reactions and defensive driving require
knowledge about classes of subjects encountered in a certain domain and about
likely perceptual and behavioral capabilities of the participants.
Driving in dawn or dusk near woods on minor roads may lead to an encounter
with animals. If a vehicle has killed an animal previously and the cadaver lies on
the road, there may be other animals including birds feeding on it. The behavior to
be expected of these animals is quite different depending on their type.
Therefore, for subjects and proper reactions when encountering them, a knowl-
edge base should be available on