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PLCopen Newsletter - Issue May 2022
- PLCopen Guidelines for Object Orientation – Application example for Motion Control
- PLCopen Motion Control for Robotics
- PLCopen YouTube channel – new video available on 3-CAM segment profile
- Pre-announcement PLCopen annual General Meeting
- PLCopen Conformity Level ST Certification for Omron Corporation
- PLCopen sponsors 26th Annual ARC Industry Forum in Orlando, USA
- Brief overview of PLCopen and the IEC 61131-3 industrial control software standard
1. PLCopen Guidelines for Object Orientation – Application example for Motion Control
The 3rd edition of the IEC 61131-3 standard enables the usage of Object Oriented Programming, OOP. With Object Orientation one can make many additional choices in the way the program is structured and decomposed, providing a different look & feel to the users especially across the different systems and platforms, creating different training guidelines and differences in maintenance.
To support the right choices and to add to the training programs, PLCopen started an OOP Guidelines initiative, in order to create a more homogeneous method. This activity helps to understand to make the right choice upfront, and to create consistent programs with long-term support.
In November 2021 PLCopen released their Guidelines for Object Oriented Programming, version 1.0. This is an additional document within the framework of the PLCopen Software Construction Guidelines. It shows how to convert a “classical” program to an OO program.
The PLCopen Promotional Committee on Training is now working on a side document showing an application example for Motion Control.
With the PLCopen specification “Function blocks for Motion Control (formerly Part 1 and Part 2)”, the PLCopen Task Force Motion Control provided a set of standardized Function Blocks to ease modularization and reuse of motion control software.
The new document that PLCopen is now working on presents an object-oriented implementation of the motion control specification, which can be combined with the set of procedural standard Function Blocks (FBs). The general design of the proposed object-oriented (OO) implementation is a single Axis Class implementing different functions as Methods instead of formerly used multiple FBs. A benefit of the proposed software design is the compatibility with procedural motion control FBs: the standard FBs can call the Axis Class internally to combine both approaches in one application. Thus, the user of the OO implementation needs not to be familiar with the detailed OO principles or language elements for using it.
As common in object-oriented programming (OOP), an interface is used to define the motion standard since it describes how a class is presented to the outside (sometimes including the behavior). More precisely, an interface is the definition of the functionalities that a class may implement. The class is the actual implementation of the defined functionalities, including vendor-specific aspects. Correspondingly, this document standardizes a motion interface. For using this standard, an axis class needs to be implemented, which follows (“implements”) this standardized motion interface. In short: the interface defines the functionalities, but not how they are implemented (their content), which is done vendor-specific in an axis class.
Utilizing two application examples, this document shows how the standardized FBs from the PLCopen motion control specification can be ported to OOP by using a standardized interface itfAxis as introduced below. To apply the standard in a vendor-specific implementation, the programmer develops a class, which implements the interfaces itfAxis and, thus, has all the functions standardized in itfAxis without implementation. Then the actual, vendor-specific implementation of these functions is programmed. The advantage of the proposed interface itfAxis is that one can decide how to program: on one hand, the standard FBs can be used, and they can internally call the itfAxis methods. On the other hand, it is possible to program in OOP by using the defined methods to start a new command, get the current status of an axis, and update or abort a command.
The details on the proposed interface and the contained methods as well as several user-defined data types are introduced in the document.
This document focuses on the motion control part of the axes only. In real projects, the axis class will have many other properties and methods for communication, hardware configuration, and additional aspects. For simplicity, these are not explained in this document.
If you are interested in joining this working, please contact us.
2. PLCopen Motion Control for Robotics
In 2008 PLCopen released Part 4 of the Motion Control suite of specifications, dealing with coordinated motion, i.c. robotics. Basically, with this specification one can control a robot in the PLC or one can see it as an interface to a robotic controller, which will do the calculations and movements.
Especially for this last option we received feedback from robotics companies with specific requirements, which resulted in a Corrigendum and the basis for Version 2.0 of this specification.
Siemens went one step further with the release of their SIMATIC Robot Library. This library is based on PLCopen Part 4 and provides an interface to many robot controllers. For this, Siemens extended Part 4 with the knowledge from the community of robot suppliers, as many of them were involved. The extensions add the configuration section to it and some additional functionalities. And from a networking perspective it is open, so not limited to Profinet only.
Siemens offered their User Manual of the Robot Library, to PLCopen, which gives us the opportunity to update Part 4, esp. on the controller side. In this way it can easily be coupled to robot controllers of the different robot suppliers, while supporting other kinematic models.
In addition, Siemens provided their library definition to Profinet International, PI, and made available Version 1.2 of the specification itself, containing more functionalities.
The Robot Library adds especially configuration functionalities as well as defines an interface to the different robot suppliers. The essence for PLCopen is to incorporate these missing functionalities in the PLCopen Motion Control standard while maintaining the same Look & Feel by providing backward compatibility.
3. PLCopen YouTube channel – new video available on 3-CAM segment profile
A new video has been posted on the PLCopen YouTube channel. This video shows a basic machine operation application using a 3-CAM segment profile, showing a structured approach to the machine application.
Other videos on PLCopen Motion Control and Safety, and on Software Structuring have been made available earlier.
We hope you will enjoy watching our videos and that they will show you on how to become more efficient in your automation.
4. Pre-announcement PLCopen annual General Meeting
The PLCopen annual General Meeting is scheduled for Tuesday June 28 in Amsterdam - The Netherlands.
All PLCopen members can participate to this meeting. If you are interested, please contact us for more details.
5. PLCopen Conformity Level ST Certification for Omron Corporation
We are pleased to announce that OMRON Corporation was granted the Certification of a system according to PLCopen Conformity Level for ST (Structured Text) for version 1.48 of their product Sysmac Studio.
For more information visit www.PLCopen.org.
6. PLCopen sponsors 26th Annual ARC Industry Forum in Orlando, USA
The ARC Industry Forum is the “must attend” learning event of the year for industry executives and technology solution providers.
PLCopen is sponsoring ARC’s 26th Annual Industry Forum which takes place from
- June 6-9, 2022 in Orlando, Florida
- June 20-23, 2022 – Online
7. Brief overview of PLCopen and the IEC 61131-3 industrial control software standard
Bill Lydon, the Director of PLCopen North America published an interesting article on automation.com: No-Code Industrial Control Programming Basics
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