Quote:
Originally Posted by Ether
I've never heard of such a thing. It would seem
to defeat the whole purpose of the integral controller.
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(I posted this last night, but it claimed it needed approval so I'll try again).
I suspect what they are hoping to communicate would be to eliminate
noise induced run away. If you get noise that interferes with your
return function then over a duration then...for example...you might
end up 'winding up' the I in such a way that even though you've
limited it...it's still way too high and because of it getting too high
over and over from disturbance and noise it may never come down and
the result might be perceived as erratic movement.
If you can 'reset' the I (not necessarily make the I constant 0), and
do it when the I is perceived to have 'wound up' too often, then you
can effectively prevent yourself from having to reset the entire PID
loop to eliminate what appears to be erratic function.
As an example...
http://community.mybb.com/thread-78886.html
When the goal is to achieve a set point of a fixed speed, then I can see how this helps when the prime concern is the change in set point.
As noted above, when the prime concern is achieving the set point position it makes sense when the loading is prone to bind at the last second. Though, the kind of binding matters. If for example the mechanism is prone to binding and then runaway (the motors are overloaded and then break free) then you're probably too close to the limits of the ideal, serial or parallel algorithms for the stable D to be achieved anyway in which case now you have a special case.