How to tune a Rockwell PIDE

PID versus PIDE

The PID instruction is the older, simpler block. PIDE is the enhanced one: it supports the two forms, better tracking, and the cascade connections you actually want. A set of numbers copied from PID into PIDE without converting for form will not behave. Convert, or retune from a bump — do not transcribe.

What to type on a PIDE in dependent form

Proportional gain: higher is stronger. Reset is typically minutes per repeat in dependent form — lower is faster integral. Rate is minutes. Put derivative on PV. Change one number. Wait.

If the block is in independent form, the three gains are separate. Raising P does not speed the integral. Tuning rules and calculators that assume the ideal form do not apply until you convert.

Mode and tracking

PIDE will kick the output on a Program-to-Operator or Manual-to-Auto transfer if .SWM, .SO and the tracking bits are not doing what you think. If the loop will not go to AUTO cleanly, fix that before any gain change. A bump that starts with a mode-change spike is not a bump.

Questions that come up

Which PIDE form should I use?

Dependent form matches most published tuning and most of the rest of the plant. Use independent only if you have a reason and you convert every number that comes from an ideal-form source.

Can I paste Ziegler-Nichols Kc, Ti, Td into a PIDE?

Only after you know the form and the units. Ti from a calculator is often seconds; the PIDE may want minutes. A factor of sixty in the wrong field is a hunting loop that still looks like a plausible tune.

Related