> -----Original Message-----
> From: Peter L. Peres [SMTP:plp@ACTCOM.CO.IL]
> Sent: Friday, November 29, 2002 3:56 PM
> To:   PICLIST@mitvma.mit.edu
> Subject:      Re: [pic]: PID
>
> Note2: The integral term will cause a lot of trouble. It is customary to
> zero it whenever Error is 0 and to limit its growth both in the high
> direction and in the low direction, to reduce trouble. The Derror is also
> limited sometimes in the high and low direction to avoid giant kicks when
> the input Setpoint changes by a large value.
>
Wether you can zero the integral term depends very much on what you are
controlling.  For a system where the controller output is zero when the
error is zero, this is acceptable (e.g. positional controls), but for e.g. a
temperature controller the controller always has some output even when error
is zero, so the integral cannot be zeroed.

Mike

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