PID Best Programming Practices

If I have a program that requires 10 different PID loops should I 10 different period tasks (using RSLogix5000)?

I use one Periodic Task for each update rate. The different functions go into different Programs (separate Tag Databases and Routines) inside the Task.

If all of your loops are similar, and run at the same update rate, I say put them inside the same Task.

Careful with Periodic Tasks

I agree with Ken on this. You can create a lot of problems by using too many periodic tasks because they can cause overlapping of tasks which will prevent some things from getting processed. Periodic tasks can be useful but a lot of planning and scheduling has to be taken into account.

In my opinion the fewer the periodic tasks the better.

Good Points. My thought was that I am walking into a process that I'm not sure how it's going to react and isolating each PID in its own task would give me more flexibility.

I recommend using a single periodic task and slicing it. For example, let's say that your loop updated time is 250ms. Create a 50ms task with a counter that counts 1 to 5 (or 0 to 4 or whatever). Increment this timer on each call to the task. When the counter = 1 call the 1st pair of PID loops, when 2 the 2nd pair, and so on.

Good luck,
(8{)} .)
(Yosi)