Integerator

[Marteney, Steven J.]

PID stands for (going from memory, some cells shorted) Proportional-
Integrated-Differential, and they are seperated by dashes because it's not
meant to be a "phrase".  The feedback in this type of control system is the
weighted sum of the output with some gain factor (Proportional), the
integral of the output (I), and the derivative of the output (D).  This type
of system typically provides more stable operation but can be more agressive
without oscillation, depending on how it's implemented.  Can't tell you
which is used in an ECM though.  That's why I'm on the list!!!

Steve

-----Original Message-----
From: Roger Heflin [mailto:rah at horizon.hit.net]
Sent: Wednesday, November 03, 1999 12:36 PM
To: gmecm at efi332.eng.ohio-state.edu
Subject: Re: Integerator




On Wed, 3 Nov 1999, CSH-HQ wrote:

> OK, then the short term corrections are integerator, and not stored,
right?.
> They are a simple feed back response to what the ecm memcal want for
mixture.
> Do the gm ecms actually use a PID, or just a dampened feedback loop?.
> Is ther much difference from feedback to PID?.
> Grumpy
> 
> 
The integrators are not stored long term, once you leavel that BLM
cell the integratros are reset to 0( 128).   But if the integrators
are greateer that +-8 (<120 or >136) on my car that makes the BLM
cell be adjusted, but when the BLM is adjusted the integrator is not
adjusted on a stock car.  2 integrators points are equal to 1 BLM
point.  On my car I modifed the code so that when the BLM is adjusted
because of the integrator, the integrator is also adjusted to maintain
constant mixture, this caused my car to not osciallate so much on the
fuel mixture.   I belive the oscillation was mostly because the VE
were so far off from all of the modifications I have done to it.

What exactly is a PID?  If I remember control systems right a feedback
loop is a standard control setup, so my guess would be that a feedback
loop is a PID, and standard controls systems stuff dones usually
dampen the feedback loop to prevent rapid osicllations.

			Roger