PID and PIDE Getting Started Guide for ControlLogix and CompactLogix Bruce Kyer RA Technical Support Engineer

Conference Call Information US Dial 866-774-1453 Conference ID: 25089971 Copyright © 2011 Rockwell Automation, Inc. All rights reserved.

Copyright © 2011 Rockwell Automation, Inc. All rights reserved. Agenda 1. Introduction 2. Parameter Overview 3. Demos Intended audience: Those that are already a little familiar with PID or process control with a some programming experience. We will quickly cover the most common PID fields used. The go over a demonstration of adding the PID and PIDE. This slideshow and ACD example will be attached to KB ID 462378, link: http://rockwellautomation.custhelp.com/cgi- bin/rockwellautomation.cfg/php/enduser/std_adp.php?p_faqid=462378 Copyright © 2011 Rockwell Automation, Inc. All rights reserved.

Adding the Ladder PID and Tags Enter the following for the ladder PID: A Tag for operator manual control if desired, or leave 0 if not used The tag that holds the PV value A backing tag of type PID for internal storage The output tag that you’ll use to drive the process (CV) Set these three fields to zero if you don’t use them These are display values from PID backing tag Copyright © 2011 Rockwell Automation, Inc. All rights reserved.

Configuring the PID - Scaling Tab Unscaled Min/Max: This should match the range from the input card Engineering units: This is what the setpoint is specified in and what the status below uses. The range the PID will use for its output This is the range the Tieback tag will use Some notes, it’s really important to have correct scaling. If you change while the processor is running, you must uncheck this box once Copyright © 2011 Rockwell Automation, Inc. All rights reserved.

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

Configuring the PID - Configuration Tab Choose Derivative of PV or Error Choose the Control Action PV–SP or SP-PV Choose independent or dependent equation form. This affects tuning. Enter the desired Loop Update Time Enter a range to limit the CV to. Enter 100 and 0 for no limit Additional Options Enter Deadband value. Freezes CV when PV is “close enough”. Can save on valve wear or help stabilize system. Leave 0 if not used. Copyright © 2011 Rockwell Automation, Inc. All rights reserved.

Configuring the PID - Tuning Tab Setpoint is what the PID tries to drive the PV to. Manual mode feeds the Tieback tag directly to the PID output. Use Set Output to directly control the output when software manual is checked. Output bias, also known as feedforward, is directly added to the output. Enter the PID gains here. These numbers can be adjusted to tune the loop. Current values and status to monitor PID state. Copyright © 2011 Rockwell Automation, Inc. All rights reserved.

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

Adding a Function Block PIDE and Tags Connect process measurement tag Connect the process control tag The Function Block PIDE Connect a tag for setpoint Connect a tag for manual output control Set True for Program Control Set for the mode desired Copyright © 2011 Rockwell Automation, Inc. All rights reserved.

Configuring the PIDE – EUs/Limits Tab Engineering units. This is the range the PV and SP use. The PV input is assumed to be in EU. Specify the range for CVEU to use (the PIDE output). 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. Make sure status says “OK” Copyright © 2011 Rockwell Automation, Inc. All rights reserved.

Configuring the PIDE – General Config Tab Usually best to leave mode periodic. In that case, PIDE will regulate itself. Specify the gains. Choose control action and equation type More advanced settings, can normally leave alone. Copyright © 2011 Rockwell Automation, Inc. All rights reserved.

Copyright © 2011 Rockwell Automation, Inc. All rights reserved. Demos PID PIDE Copyright © 2011 Rockwell Automation, Inc. All rights reserved.

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