Studio/Logix5000

Anyway to setup the standard PID / PIDE / LEADLAG blocks to be event based rather than time based? I have tried gain scheduling, but I find this changes too quickly for me.

I am considering just writing my own.

http://www.plctalk.net/qanda/showthread.php?t=74531

There are many settable settings in the enhanced PID instruction (PIDE). I have not looked at all of them.

Event driven vs time based is an interesting topic. I have only worked on time based but have read about the event based.
https://hal.archives-ouvertes.fr/hal-00832014/document

It looks like you may have to write your own.
Thanks for getting me thinking.

I cannot comment on LEAD/LAG, but the PID instructions MOST DEFINITELY need to be executed at a periodic rate.

The calculations within the PIDs are based on elapsed real-time, and you will throw them into disarray if you do not execute the instructions on a repetitive, fixed, time-base. And you need to tell the instruction what that time-base is, by writing to the .UPD parameter in the PID tag.

You need to ask a specific question about a specific application.
PID/PIDE/Lead-Lag are ALL time-dependent functions. Remove the time element, and what do you have?

What do you expect with "Event" based calculations?

I have a conveyer with an encoder.

I would like to do
OP = KP * E + KI * SUM (E dx) + KD * dE/dx
Where x is in meters
Rather than
OP = KP * E + KI * SUM (E dt) + KD * dE/dt

My dead time is 5meters and my lag is 15meters
I have linearised my output so that the steady state process gain is constant.

I think you are right, and my best bet is to write my own, rather than trying to shoehorn my crazy idea into a time dependent set of functions.