March 2020

Welcome to the PLCopen® electronic newsletter.

For comments or additional information check either www.PLCopen.org or send an email to Wendelien@PLCopen.org.
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PLCopen Newsletter - Issue March 2020

  1. PLCopen Guidelines for Object Orientation
  2. PLCopen Benchmarking – entering a new phase
  3. PLCopen releases version 2.01 of the Safety Part 1 specification
  4. PLC Programming Preference Survey
  5. PLCopen welcomes new members

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1. PLCopen Guidelines for Object Orientation

In November last year we announced the start of the new initiative on PLCopen Guidelines for Object Oriented Programming. The 3rd edition of the IEC 61131-3 standard enables the usage of Object Oriented Programming. Parallel to this, PLCopen has defined the concept of function block libraries including object orientation, as well as sets of function blocks for motion control, safety and communication.

When one starts to program in an object-oriented world, one can make many choices. Choices like: are all FBS in one Class? If so, do we need the MC_, or even the AxisRef? How do they contain the methods? And will we use only methods, or also direct access to variables? Is the state machine for the axis controlled by the methods? Are all axes objects with methods, and we access them only via these methods? How about interfaces?

All these choices give a different look & feel to the users across the different systems, different training guidelines and differences in maintenance. And this is where PLCopen wants to help and give guidance, in order to create a more homogeneous programming methodology.

Overall there is very little information on how to use object orientation for industrial control or the operation technology (OT). The goal of the PLCopen working group is to guide here with the following goals:

  • Guidance to using Object Orientation in addition to the “classical” way.
  • Provide the same look & feel in using OO programming across the different platforms and implementations.
  • Create generic design patterns for industrial control programming.
  • The classical programming way should be possible to use in addition to the object orientated way (e.g. this can mean that we have to extent the classical FBs with for instance interfaces, methods, properties, and maybe input and outputs).

In order to show an example, the warehousing example as used in PLCopen Motion Control examples to represent this in the different forms of programming will be used.

Since the kick-off meeting, we made good progress and are now getting into a phase where we would like to extend the working group with more users who are willing to share their experiences.

If you can contribute to the PLCopen Guidelines for Object Oriented Programming, please contact me: evdwal@PLCopen.org.

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2. PLCopen Benchmarking – entering a new phase

The PLCopen benchmarking workgroup has a more hardware resource oriented (like processor and computing architecture) approach. With this new initiative, the benchmark can indicate the effective performance of the different processors and architectures as used in the industrial controllers. By the time the IEC program can run, it is already "too late" to tune and much time and effort is already invested.

This workgroup is defining a common language between the different parties involved, combined with common test scripts for real-time and the influence of the other processes and perhaps not looking for highest performance but for predictable, reliable and deterministic approach at good pricing. Otherwise stated: the best performance for the best price, like “the best bang for the buck”.

This initiative is now entering the phase of defining and developing the microbenchmark scripts relevant for the evaluation.

In order to speed up the process there is a bi-weekly webmeeting scheduled on Wednesday at 16:00 CET. Let me know if you want to participate: evdwal@PLCopen.org.

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3. PLCopen releases version 2.01 of the Safety Part 1 specification

In July 2018 PLCopen published version 2.0 of their Safety Specification Part 1 - Concepts and Function Blocks for Safety Functions. The original document describes the functionalities as well as extensive state diagrams which add to the understanding, references to the applicable standards, description of error behavior, functional checks, and error codes, and identifies different programming levels. As such it is an ideal platform for implementers. For users, additional information on safety devices, connections and wiring is of course needed.

The updated Version 2.0 contained many changes:

  • Incorporating the Part 3, especially the section on diagnostics and the additional defined 5 function blocks.
  • The Structured Text language ST is added, as well as additional datatypes and functionalities.
  • All the original function blocks have been updated w.r.t. diagnostic codes, the outputs safety demand and reset requested, and the reset functionality has been extended to trailing edge via the definition of a new function block.
  • Also there are 3 motion related function blocks removed and added to a separate document on SafeMotion.

PLCopen now released version 2.01 of the Safety Part 1 specification, based on the feedback and resulting corrigendum on version 2.0. There were a set of small errors and references in the V2.0 which of course had to be resolved. Hence the update.

The new document PLCopen Safety Part 1, version 2.01 can be downloaded from our website.

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4. PLC Programming Preference Survey

In 2019 PLCopen North America and Automation.com conducted a joint survey of PLC programming preferences.  The majority of over 200 responses from PLC users were from North America and Europe. Here are some of the results to inform you of current trends in PLC programming and users’ thoughts on vendors: https://www.automation.com/plc-programming-preference-survey-insights-user-comments.

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5. PLCopen welcomes new members

PLCopen is very pleased to announce three new members:

  • Arm Ltd., based in the UK, a world leading supplier of microprocessor technology and delivering a complete Internet of Things (IoT) solution.
  • Intel Corporation, based in the USA, well-known for their processors and a.o. cloud and IoT technologies.
  • Zhongji Huajiao, is a training centre for intelligent manufacturing industry in the province of Anhui in China.

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