AB Periodic Tasks and PID's

dginbuffalo · Mar 11, 2019

Hello. I'm trying to figure out if it is better to have multiple PID loops in 1 periodic task, or have several (5) periodic tasks? I'm thinking 5 tasks because the period could possibly be different if the loops required different update times. Thoughts? Thank you!

Ken Roach · Mar 11, 2019

Are you using ladder PID or function-block PIDE ?

The PIDE enhanced function block adopts the periodic rate of the Task it is executed in, so if you need a different loop update rate, you need another Task.

The basic ladder PID is executed at whatever rate you program it to be executed (timer, Event, etc), and you have to be sure that you have programmed the instruction and configured the Task that contains it so that they actually run the way you intend.

dginbuffalo · Mar 11, 2019

Ken Roach said:
Are you using ladder PID or function-block PIDE ?

The PIDE enhanced function block adopts the periodic rate of the Task it is executed in, so if you need a different loop update rate, you need another Task.

The basic ladder PID is executed at whatever rate you program it to be executed (timer, Event, etc), and you have to be sure that you have programmed the instruction and configured the Task that contains it so that they actually run the way you intend.

Thanks Ken. Just running a ladder PID (only routine in that task). I've made sure my PID loop update time and periodic task rate are the same.

rdrast · Mar 12, 2019

I just group all of mine in a task based on the update rate needed.
25ms for faster loops, 500ms for heater loops, etc.

dginbuffalo · Mar 12, 2019

rdrast said:
I just group all of mine in a task based on the update rate needed.
25ms for faster loops, 500ms for heater loops, etc.

Thank you both!

AB Periodic Tasks and PID's

dginbuffalo

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Ken Roach

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rdrast

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