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4.4 List of Mission Elements 121

4.4 List of Mission Elements

Planning entire missions is usually done before the start of the mission. During this
process, the mission is broken down into mission elements which can be performed
with the same set of behavioral modes. The list of mission elements is the task de-
scription for the process governing situation assessment and behavior decision. It
also calls for implementation of behavioral capabilities actually available. In case
some nominal behavioral capability is actually not available because of some
hardware failure, this fact is detected by this process (by polling corresponding bits
in the hardware monitoring system), and mission replanning has to take this new
situation into account.
The duration of mission elements may be given by local timescales or by some
outside event; for example, lane following should be done until a certain geo-
graphical position has been reached at which a turnoff at an intersection has to be
taken. This is independent of the time it took to get there.
During these mission elements defined by nominal “strategic” aspects of mis-
sion performance, tactical deviations from the nominal plan are allowed such as
lane changing for passing slower traffic or convoy driving at speeds lower than
planned for the mission element. To compensate for the corresponding time losses,
the vehicle may increase travel speed for some period after passing the convoy (pa-
rameter adjustment) [Gregor 2002; Hock 1994].
In the region of transition between two mission elements, the perception system
may be alerted to detect and localize the relative position so that a transient ma-
neuver can be started in time, taking time delays for implementation into account.
A typical example is when to start the steer rate maneuver for a turnoff onto a
crossroad. Sections 14.6.5 and 14.6.6 will discuss this maneuver as one important
element of mission performance as implemented on the test vehicle VaMoRs. Fig-
ure 14.15 shows the graphical visualization of the overall mission. The correspond-
ing list of mission elements (coarse resolution) is as follows:
1. Perform roadrunning from start till GPS signals the approach of a crossroad
onto which a turnoff to the left shall be made.
2. While approaching the crossroad, determine by active vision the precise width
and orientation of the cross road as well as the distance to the intersection.
3. Perform the turnoff to the left.
4. At a given GPS-waypoint on the road, leave the road at a right angle to the right
for cross-country driving.
5. Drive toward a sequence of landmarks (GPS-based); while driving, detect and
perceive negative obstacles (ditches) visually and avoid them through bypass-
ing on the most convenient side. [There is no one, actually in this part of the
mission.]
6. Visually detect and recognize a road being approached during cross-country
driving (point 6 in Figure 14.5). Estimate intersection angle, road width, and
distance to the road (continually while driving).
7. Turn onto road to the left from cross-country driving; adjust speed to surface
inclination encountered.
8. Perform roadrunning, recognizing crossroad as landmarks (points 6 to 8).