18th annual conference on manual control.pdf - Acgsc.org

is repeatedfor several values of control attention,fc, and the summationis
taken over the nine elementsof Eq. (i0). The optimal fci that ensue provide
the relativeimportanceof each of the states, i.e., the informationrequirements
for the control task.
The OCM analysis yields the relative attentional allocation (fci/fc), summarized
in Table 1 and Figure I. The attentional allocations are examined at four
levels of total control attention, fc = 0.9, 0.7, 0.5, 0.3. The only variables
..thatcommand significant pilot attention are the terrain "vertical acceleration"
_(t), the FPE rate, e(t), and the FPE e(t). All other system states demand
negligible attention in the pilot model.
TABLE i. RELATIVE ATTENTIONAL ALLOCATION- f
INFORMATION LEVEL c! $
.... ....... -_c 0.6
fc f/fc re/refe/fc 04
0.9 0.46 0.34 0.i 0.2
0.7 0.46 0.36 0.i . : • , •
I
0.5 0.42 0.36 0.i 0:2 0'.4 0._6 0.'8 1.0'_ f¢
0.3 0.37 0.33 0.i
........ Figure i. Relative Attentional
Allocation-lnformation Level.
Notice that there is a consistency in these results, i.e.,
fe
fe
f = const., --_--- =_const., f _ const.
c c C
Thus, the relative importance of the key state variables does not change over
different levels of control attention fc"
,.
The results, which indicate that _(t), e(t), and e(t) is the critical information
base, must now be interpreted. A major design issue, at this point, is
in determining whether or not a separate display of each critical variable is
required for use by the pilot. It is clear that a FPE indicator should be
included since it is essential that the pilot knows his instantaneous position
with respect to the desired path K(t). Such a display is easily constructed
using, e.g., a radar altimeter. Also, the pilot can easily extract the FPE
rate from a well designed display of e (t), and therefore, a separate e (t)
indicator is not needed.
The major portion of the pilot's attention is allocated to E(t). In practice,
this variable is difficult to derive and display explicity. Also, it is not
clear how such a display might.be used by the pilot. One must, therefore,
synthesize a display in which _ (t) will be incorporated in a practical manner.
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