[Avery.Andrews 950130]
I got my `fish' working, in a rudimentary sort of way, so here's a
little piece on velocity-control, including a simcon program for
testing the idea.
Suppose we want to get somewhere. In principle, we'd like to be
going very fast, but, of course, mostly we don't. We seem to have
some sort of very high ideal `wish-velocity', which gets downgraded
to a more moderate one, through the intervention, I claim, of
perceptions of fear (perception of too much velocity) and pain
(perception of too much effort).
To begin with, the high initial velocities. Objectively, the velocity
scale ranges between -c and c, but from a perceptual point of view,
the scale is quite different, limited by some sort of perception
based on velocity. For visually-guided locomotion, this will be flow
of the visual field, which would get mapped onto actual velocity
in a way dependent on the setup of the environment (walking in your
living room vs. flying an F111 through a mountain range). This
perception is obviously highly saturable, at a value I will arbitrarily
assume to be 100. So this is the constant `velwish'
In the model, velwish is one of the contributors to velref,
with a weighting factor of 1. Velref then determines an acceleration,
which integrates to give velocity.
The other contributor is fear; fear is generated by a one-sided
comparator when the velocity exceeds the speed-limit. In a
more comprehensive model, the speedlimit could be varied (via
assessment of the circumstances, as well as the weighting of
its contribution to velref (`timidity', if we express it in
positive units, & multiply it by -1. If you run this, you'll
see that it speeds up to above the speed limit, then shows
damped oscillation. I haven't managed to make the oscillations
go away, but haven't tried to hard since this sort of behavior
looks a bit realistic to me.
Next comes pain, but this will require slightly more elaborate physics,
& I wanted the first one to be simple.
Avery.Andrews@anu.edu.au
···
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title Speed vs. Fear
time 10.0 .01
velocity integrator 0.0 acceleration 1.0
velwish const 100 # ridiculously high
speedlimit const 20 # the point at which fear kicks in
fear0 comparator velocity speedlimit
fear limit fear0 0 200 # no fear until speedlimit exceeded
velref summator velwish 1 fear -100
velerr comparator velref velocity
acceleration amplifier velerr 0.0 0.1 0.5
group distance velocity acceleration
group fear0 fear
print velocity fear velref
plot
ro