[Paul George 940719 10:40]
From Tom Bourbon [940718.1739]
Why would those two scenarios call for two different "modes" of control? If
perceived rate of closure is being controlled, with a reference value of
zero, or something very small, then think of how the error signals would be
changing in the two scenarios, prior to the person applying the brakes.
Even if the person's gain did not change, or the "mode" of control remained
the same, the error signal would be much bigger and growing more rapidly in
the one scenario than in the other. Perhaps?
Perhaps. Sometimes the magnitude or rate of change of the error signal may be
sufficient. I guess it depends how sophisticated you allow the output function
(F2) to be. If it can select between different actions based upon thresholds
for the error signal, fine. The idea is that different actions may be required
in response to different amounts or rates of disturbance. To deal with a punch,
sometimes you block, sometimes you duck. Depends on how fast it is coming, and
where your arms are.
I think the more common structure might be having another control loop
monitoring the error signal, treating it as a controlled variable. That loop's
output function would then activate the appropriate loop for the needed kind of
action (i.e an 'emergency' loop). This presupposes that you have multiple loops
capable of controlling the same perception, but have their reference variables
adjusted so only one actually generates an error signal at a given time.
Possible?
Paul