Opto 22

43044 Business Park Drive, Temecula, CA 92590 USA
Local & outside the USA:(951) 695-3000
Toll-Free within the USA:(800) 321-6786
Fax: (951) 695-3095
Email: sales@opto22.com
 
KB82058
Host-fed PID Velocity Type B, ISA, Parallel, and Interacting algorithms do not calculate D or P terms
Revision:  4.0
Published:  7/21/2016
Applies To
Firmware for:
SNAP-PAC-EB1
SNAP-PAC-EB2
SNAP-PAC-EB1-W
SNAP-PAC-EB2-W
SNAP-PAC-R1
SNAP-PAC-R2
SNAP-PAC-R1-W
SNAP-PAC-R2-W
SNAP-PAC-SB1
SNAP-PAC-SB2
Versions
Problem affects versions:  
All versions
Problem is fixed in version:  
PAC Firmware R9.4c
(See NOTE.)

SYMPTOMS

When configuring a PID, if the input is supplied by the host rather than directly from an I/O point, the controller firmware can overwrite the value of the input (making it incorrect in the equation). When this happens, the P Term and the D Term will calculate to zero.

The types of PIDs affected are:

  • Velocity (Type B)
  • ISA
  • Parallel
  • Interacting

WORKAROUND

Use the Velocity Type C PID algorithm.

RESOLUTION

Opto 22 has resolved this issue.

NOTE

To resolve this issue, new algorithms for ISA, Parallel, and Interacting were added to PAC Firmware R9.4c and higher.

To avoid impacting existing PID loops, the original algorithms will remain in the Algorithm list. Because they still have this defect, their names were changed to ISA (Obsolete), Parallel (Obsolete), and Interacting (Obsolete).  The Velocity - Type B algorithm was also renamed, because it’s affected by the same defect. Velocity (Type C) did not change because it does not have the defect.


If you upgrade to the newest PAC software, you’ll see the new names when you edit PID loops that were configured with an obsolete algorithm.  This lets you know that your PID loop was configured with the original version of the algorithm.  You can continue to use the obsolete algorithms, but Opto 22 recommends you use the new algorithms or Velocity (Type C) when you configure PID loops for a new application.

You don’t need to change your PID loop configuration unless you are affected by this issue.

If you have PID loops that get their input from Host, here’s what you can do to fix them:

  • For PID loops that use Velocity (Type B), reconfigure them to use Velocity (Type C), and retune them.

  • For PID loops that use ISA (Obsolete), Parallel (Obsolete), or Interacting (Obsolete), you must:
  1. Upgrade the firmware of the I/O units (brains) that your PID loops are configured on to PAC R9.4c or higher.
  2. Upgrade the software you use to configure PID loops.
    The lowest versions that support the new algorithms are:
    • PAC Control R9.5a
    • PAC Manager R9.5a
    • EtherNet/IP Configurator R3.0n
  3. Reconfigure the PID loops to use the new algorithms.
  4. Retune the PID loops.

Relevant Downloads
No relevant downloads have been specified.
Questions? Contact Opto 22 Product Support.
Phone: 800-835-6786 or 951-695-3080
Email: support@opto22.com

DISCLAIMER

This Opto 22 Knowledge Base ('OptoKB') article is intended to provide general technical information on a particular subject or subjects and is not an exhaustive treatment of such subjects. Accordingly, the information in this OptoKB article is not intended to constitute application, design, software, or other professional engineering advice or services. Opto 22 may modify the OptoKB articles at any time. Before making any decision or taking any action which might affect your equipment, you should consult a qualified professional.

OPTO 22 DOES NOT WARRANT THE COMPLETENESS, TIMELINESS, OR ACCURACY OF THE DATA CONTAINED IN THIS OPTOKB ARTICLE AND MAY MAKE CHANGES THERETO AT ANY TIME AT ITS SOLE DISCRETION WITHOUT NOTICE. FURTHER, ALL INFORMATION CONVEYED HEREBY IS PROVIDED TO USERS 'AS IS.' IN NO EVENT SHALL OPTO 22 BE LIABLE FOR ANY DAMAGES OF ANY KIND INCLUDING DIRECT, INDIRECT INCIDENTAL, CONSEQUENTIAL, LOSS PROFIT, OR DAMAGE, EVEN IF OPTO 22 HAS BEEN ADVISED ON THE POSSIBILITY OF SUCH DAMAGES.

OPTO 22 DISCLAIMS ALL WARRANTIES WHETHER EXPRESSED OR IMPLIED WITH RESPECT TO THE INFORMATION (INCLUDING HARDWARE, SOFTWARE, AND/OR FIRMWARE) PROVIDED HEREBY, INCLUDING THE IMPLIED WARRANTIES OF FITNESS FOR A PARTICULAR PURPOSE, MERCHANTIBILITY, AND NON-INFRINGEMENT. Note that certain jurisdictions do not sanction the exclusion of implied warranties: thus, this disclaimer may not apply to you.

Copyright © 2016 Opto 22. All rights reserved.

My.Opto22

All Opto22

Request Information
  • FREE Product Brochure
  • Product Demonstration
  • PreSales Engineering Assistance

Opto 22 Product Support

Opto 22 Product Support is FREE Monday through Friday 7 a.m. to 5 p.m. Pacific Time

Product Support Numbers:

Local: (951) 695-3080
Toll-Free: (800) 835-6786
Fax: (951) 695-3017
support@opto22.com

Products

None

Downloads

None

Documents

None