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Copyright © 2011 Rockwell Automation, Inc. All rights reserved.

PID and PIDE Getting Started Guide for ControlLogix and CompactLogixBruce KyerRA Technical Support Engineer

Conference Call Information

US Dial 866-774-1453 Conference ID: 25089971

Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 2


Agenda

1. Introduction

2. Parameter Overview

3. Demos


Adding the Ladder PID and Tags

• Enter the following for the ladder PID:

A backing tag of type PID for

internal storage

The tag that holds the PV value

The output tag that you’ll use to drive the process

(CV)

A Tag for operator manual control if desired, or leave

0 if not used

These are display values from PID backing tag

Set these three fields to zero if you don’t use them


Configuring the PID - Scaling Tab

Engineering units: This is what the setpoint is

specified in and what the status below uses.

Unscaled Min/Max: This should match the range

from the input card

The range the PID will use for its output

This is the range the Tieback tag will use

If you change while the processor is running, you

must uncheck this box once


Configuring the PID - Alarms Tab

• The PID has built-in alarming.– Can be used by the program to indicate that the PV is out of range.– Is not essential for PID operation - does not have to be used.

Specify alarm limit values if desired, or leave all 0 if

you don’t use.


Configuring the PID - Configuration Tab

Choose independent or dependent equation form.

This affects tuning.

Choose the Control Action

PV–SP or SP-PV

Choose Derivative of PV or Error

Enter the desired Loop Update Time

Enter Deadband value. Freezes CV when PV is “close enough”. Can save on valve wear or help stabilize system. Leave 0 if not used.

Additional Options

Enter a range to limit the CV to. Enter 100

and 0 for no limit


Configuring the PID - Tuning Tab

Setpoint is what the PID tries to drive the PV to.

Output bias, also known as feedforward, is directly added to the output.

Manual mode feeds the Tieback tag directly

to the PID output.

Enter the PID gains here. These numbers can be

adjusted to tune the loop.

Current values and status to monitor PID state.

Use Set Output to directly control the output when software manual is

checked.


Adding the Ladder PID - Timing

• The Ladder PID is not self-regulated (timed). – Needs to be regulated with Timer or Periodic Task, otherwise, output will be wild.– PID should only be executed as fast as process needs to conserve CPU resources.– The period at which the PID is scanned true should be filled into the Loop Update

Time. Programmer must make sure that this is filled in manually or update programmatically PID_Backing_Tag.UPD.


Adding a Function Block PIDE and Tags

• The Function Block PIDE Connect process measurement tag

Connect a tag for manual output

control

Set True for Program Control

Connect the process control tag

Set for the mode desired

Connect a tag for setpoint


Configuring the PIDE – EUs/Limits Tab

Specify the range for CVEU to use (the PIDE

output).

Engineering units. This is the range the PV and SP

use. The PV input is assumed to be in EU.

Make sure status says “OK”

Limits the CV and SP to a sub-range. Make sure this

is filled in after setting scaling. Typically, SP limit

is same as PV.


Configuring the PIDE – General Config Tab

Specify the gains.Usually best to leave mode periodic. In

that case, PIDE will regulate itself.

Choose control action and equation

type

More advanced settings, can normally

leave alone.


Demos

• PID

• PIDE


References

• Using the PIDE Instruction White Paper• Logix5000 Controllers Advanced Process Control Reference Manual• Logix5000 Controllers General Instructions Reference Manual• This presentation and the associated ACD example will be attached to

Knowledgebase ID 462378

http://literature.rockwellautomation.com/idc/groups/literature/documents/wp/logix-wp008_-en-p.pdf

http://literature.rockwellautomation.com/idc/groups/literature/documents/rm/1756-rm006_-en-p.pdf

http://literature.rockwellautomation.com/idc/groups/literature/documents/rm/1756-rm003_-en-p.pdf

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