Members Only | Ezine | Links | Legal Notice | Contact us |

NEWS


booth #1-06


PLCopen OPC-UA
Client v 1.1
now released


Creating PLCopen
Compliant Libraries
v0.99 RfC




PLCopen
Safe Motion v0.99
Release for Comments



PLCopen
presentations
available

 


 

 


 

 




 

 

 

PLCopen gains world wide acceptance

Introduction

PLCopen has been founded in 1992 as an independent association for industrial suppliers and users. “Looking back, a lot has happened within PLCopen during this period, and nowadays these goals have been adjusted.” says Eelco van der Wal, Managing Director of PLCopen. “Within a changing environment it is impossible to stick to the same goals during a long period of time” he adds.

One of the major changes is the focus from promoting the IEC 6113-3 standard to supplement to this standard. The promotion however is still taking place on a worldwide scale.

In Europe, where the activities of PLCopen were started, the acceptance of the standard is already on a high level, so promotion is not the main issue.

In other regions, like the US and Japan, where the acceptance is lower, the promotion is still very important. However, the acceptance and interest in Japan is increasing, also due to the support by local government in their tenders as pre-requisite.

China, as upcoming market, is also important at this moment. “We want to introduce the IEC standard there also” says Eelco van der Wal. ”I am particularly thinking about the educational system. With this you create engineers which are used to these environments and will be able to use the standard in a broad area of applications, independent of the supplier. It is a major advantage that one can give a training without directly referring to a specific product or development environment. It is all about the right methods and structuring tools included in the standard.

As such, one can see a global difference: in Europe, technical activities on and additions to the standards are developed or already realized and implemented, while in certain other areas they are still in the process of acceptance, understanding the basics and using the benefits provided.

Technical aspects

The work on technical extensions mostly take place in Europe, within the so called ‘technical committees‘. At this moment the most active of these committees are TC2 for function blocks libraries, TC3 for certification nowadays on a higher level, TC5 for safe software, and TC6 for XML.

Within TC2, there are two groups active: one dedicated to Motion Control function blocks, which is already active for quite a while, and the other for safety related function blocks.

Two years ago, the Motion Control group released a specification related to the building blocks for motion control, combined with a state diagram.

This specification provides the user a standardized interface to his application software and system. Also, the development environment, the development structure, as well as the development methodology are equal and independent of the underlying system architecture. As such it supports different architectures and platforms with the same look and feel.. This is a major step forward, which is getting more and more accepted.

The specification itself is available on the PLCopen website and has been downloaded more then 25.000 times over the past two years. Mr. van der Wal states that he does not know who downloaded the specification but he sees a very clear acceptation level in the feedback.

Machine manufacturers

A very important user group, who sees the importance of this specification, are the machine manufacturers. Within this group it is especially the packing industry. This type of industry has to react fast to changes in consumer behavior by providing alternative packaging technologies. This can be done by more flexible machines in their production lines. And to provide this flexibility, one has to go beyond mechanical solutions, to mechatronic alternatives. Of course this includes more software, playing an key role.

Within this area the acceptance level of the Motion Control specification is very high, and European suppliers of the packing industry are very progressive. This makes them market leader in the world, meaning that most of the machines are manufactured in Europe. As such it is an important export product. And this export immediately shows additional difficulties: different regions ask for different brands of controllers. Meaning that even though it is used on the same machine and providing the same functionality, several different brands of controllers have to be implemented for export.

The intention of the Motion Control group was to specify an independent library of building blocks. This provides a standard command set and structure which hides the under lying architecture to the user. Otherwise stated, the structure can be used on many platforms and architectures. In this way one can decide in a late stage of the development which architecture will be used. Advantages for the machine builder are, amongst others, lower costs for supporting the different platforms and the freedom to develop application software in an independent way, without destroying productivity. On top of that, maintenance is easier and the education period is shorter.

User groups are important

The increase of the acceptance within the food & beverage, as well as pharmaceutical industry is becoming more visible every day. For instance, there is a big user group, started by the automotive industry, which nowadays serves these markets too. This group is searching for methods how to make the production lines more flexible . This research is very important for industries like packaging, which cannot produce the same packaging over and over. A simple example is coffee. We all know the vacuum-sealed pounds packs, the bricks. Is has been here for ages. If we look nowadays on the shelves in the supermarket we see an enormous variety, with different tastes and different packaging technologies. The basics of the coffee are not changed. The process side is like finalized, and cannot provide much more. This means that more and more attention is going now to the presentation in the shop.

Another example is Wasa Knäckebröd, and similar items, which nowadays is sold in smaller entities within the same package, to guarantee a longer freshness of the product. To realize this the infrastructure in the production line must be changed: a packaging function has to be added. However, these, and other sometimes temporarily changes, have to be realized on the same production lines.

One last example: a 20% discount on a bag of chips is less visible as a bigger bag containing 20% more. However, for the production line this is a major change. Not only the filling system must be adjusted, but a different sized bag has to be used. A temporarily marketing action like this cannot be solved adequately with in a pure mechanical system. Mr. Van der Wal: “This is impossible because the machine will b closed down for at least one week.” What manufacturers really want, is this transformation within one minute, resulting in a minimum loss of production and money. “You see this happen in the whole packing industry” adds Eelco van der Wal.

An easier integration in the production line is required to make this possible. An added function has to be realized within a matter of hours. The aforementioned user group developed a model with which they showed that adding a packaging function out-of-the-crate until full production can be done within 3 hours.

User requirements need new machine concepts.

To easily fit into production lines, a packaging machine has to fulfill two requirements for the user: ‘maintenance free’, or at least very low and predictable, and easy to clean for maximum hygiene. Add a goal for the machine builder, like a 50% reduction of the mechanical parts. If you take these three goals for your new packaging machine development, what will be the outcome, is the rhetorical question of Eelco van der Wal.

For the realization this means: remove all mechanical parts that can attract dust and everything that needs oil. Items like pulley’s, belts, gearboxes, and mechanical CAMs.

In practice this means, that a conventional machine with 118 functional units will be reduced to 23 function units. A reduction of 81%!

“We move from a traditional mechanical design to a design with much less components, and which is easier to clean” adds Eelco van der Wal. ”From a mechanical linked unit we will go to a mechatronic operated system: cleaner, more simple, more transparent, faster and cheaper, to name a few advantages. And this is what the user wants.”

The only way out is a mechatronic solution, with a more essential role for the control. It’s not about the quality of the mechanics anymore, but about the software in the control. Unfortunately, this usually gives a different problem within the average machine manufacturer. On the average they are between 50 and 100 years in operation, and family owned. And they have a mechanical background. It is extremely difficult to change from an organization with a classic mechanical mindset, in which at the end one adds a controller - into one focused to software and control, with the mechanics at a later stage.

Within PLCopen motion control this is recognized, and a tight coupling between the logical tasks and motion tasks is realized. Software plays an ever increasing crucial role, like supported by all kind of research on cost structures. ”Thirty years ago there was almost no software in the machines, now this is around 50% of the total cost on a production line” adds Eelco van der Wal.

Different architectures – one solution

Within the motion control market there is a variety of systems, all with their own, proprietary technology, own languages, own dialects, own busses and an own development environments, and more. Although there is a need for standardization, it is definitely was not available.

The machine manufacturer wants to serve a broad market, while only developing the application once. Until now several developments take place: for his high-end machines, his middle-end machines en his low-end machines. Van der Wal “He doesn’t want to be involved in three totally different types of development. Further more there are many export regulations to be considered, as well as for several types of operations and platforms.”

Why do we need ten different descriptions to move an axis, when it is possible with only one. Why know which motor, control or encoder is used already in an application phase?

Address this user on a different level by implementing all the technical aspects in the functionalities itself. That is what PLCopen Motion Control has done.

Motion Control Specification - Part 1

Two years ago, part 1 of the specification was released. It included motion functionality for both single axes and multiple axes, several administrative tasks, as well as a state diagram. The latter is for control and safety aspects: not every command can be issued to a machine at all moments. One has to go through a certain routine.

“Whatever system is used, we only need a few steps to rotate an axis.” explains Eelco van der Wal. “What is logical to the user: turn the power on, start the home procedure, and finally give the axis a move command like ‘move-absolute’. With these three simple steps, the axis has to move.”

“I do not want to know what network is behind the interface - that is something the supplier has to take care of”. He supplies me with the buildings blocks and I just call these three in a small program. I compile the code, download it and play it. If the axis doesn’t turn, the supplier has a problem, not the user.”

This part 1 is now available also in products, and in the meantime two additional parts have been defined: Part 2, containing the extensions with mainly multi-axis related tasks and Part 3, the user guidelines. In these guidelines it is described how the user can make its own building blocks based on the IEC standard and the PLCopen Motion control function blocks.

To give an example: in part 2 a registration function is defined, without giving the input that is used. Inputs from sensors where either the location is not known (directly or networked) and /or need to be compensated. This functionality consists of standard blocks in which the registration function is defined, and other, user-defined blocks, and can be added as such to the company own library. This registration function now can be used company wide, and the source is usable on different platforms. This saves time and money in the next machine.

The near Future

The next part of the Motion Control specification – User Guidelines - will be published shortly as version 0.99. ” With this, we want to signal the users to give feedback, which we will integrate in part 2 before we release it as the 1.0 specification. Part 3 shall be a more open specification, which we will update on a regular base, including new application examples or to ad specific subjects.

And even at that time the work will not be ready. Discussions started already on two additional parts: one to describe the homing procedure in more detail, and one to include stacked commands.

Market acceptance – the full supply chain

PLCopen Motion Control deals with a chain. This chain consists of independent software suppliers, hardware suppliers for control, and on the user side the machine manufactures.

The software suppliers are very happy with these developments. Because it is a standard, it makes it easier for them to talk to their (potential) users – the control suppliers. They only need to implemented it once, with only small changes regarding the underlying architecture. The newer hardware suppliers, with no legacy systems, also see it as important progress: they do not have to think about the specifications anymore. The longer existing motion suppliers had a little skepticism to accept a standard, because they are afraid that their possibilities for differentiation will be restricted.

“An elusive argument” says Eelco van der Wal “Because not everything is covered in the standard. There are different networks, control systems, operating systems, installation and maintenance tools, ranges of drives, motors, and encoders . Here, diversification is applicable.. An absolute movement remains an absolute movement in any environment, you do not want to change that. One has to diversify in the supplied building blocks, the software suite of tools, the range of servo’s, encoders, and more. This group, however, is willing to integrate their different, existing platforms into a single environment while merging the know-how of their different motion control groups, to better make use of the synergy. This standard offers them a way out of the jungle of their different implementations.

The next link in the chain are the machine builders. With some of them you see a clear break with the past. They are working on knowledge center where mechatronic solutions are offered. Especially for this, companies are bought and merged into bigger operations to jointly enlarge and broaden the market, by offering a new generation of machinery.

At the end of the chain are the users – those who use the machines. They want their flexibility and less downtime: faster, better, cheaper. What is new?

Product liability

A lot is happening in the supplier markets. And the government plays a major role in this with the increase of the product liability. And with this, trace ability is becoming very important.. Examples are the pollution in a product. It better has to be traceable in which batch it has occurred, to reduce the costs of recall. This liability also means that there are increasing demands on production. Expiration dates for instance. Sterile production environments, hygiene circumstances, and others, must be controlled, and must be proven as soon as there are problems. Penalties of 100 million dollars if you do not commit to the strict norms of the FDA, Food and Drug Administration, can enforce bankruptcy of the company.

Safety

Labor conditions, especially focused to injuries, are also part of the company liability issues. Nowadays one sees a stronger awareness of safety aspects around the production lines to be defined and implemented. Unfortunately, there are many standards on this, and most of them provide more a framework than directly applicable guidelines.

For this reason, PLCopen initiated a safety working group. They will define safety aspects, and support from a software point of view of applicable standards and regulations.

Nowadays is the mentality of people involved in safety aspects completely different from those working on the application side. For example, let us look at an (little exaggerated) example of a light bulb. The engineer switches the lamp to ON if he wants to give a signal, so the lamp will normally not burn. With the safety people it is always on, for testing the circuit, and all alarms go on if the light is not burning.

This has to change: a standard can take over several functions – integrating the application and safety aspects in a efficient way, including existing safety busses and controls. Important is that the safety person can communicate with the software engineer. And for this the key word is standardization, comparable with function blocks for motion control.

Interested parties are the German TÜV, which see this standardization at the software level as a great gift bringing unity in the enormous pile of regulations and rules.

Besides function blocks for safety, it is very important that we look at the development environments, in which the blocks are connected and should operate with each other within the safety environment. “Within a safety relevant part one cannot easily include a non-safety related block and think you are still fulfilling the safety level. We have to work on this safe environment supporting tools within TC5 safe software of PLCopen, to help the engineers, otherwise things can go wrong. too easily”.

XML

IEC 61131-3 is focused to the software development environment. As such it is just one part for a total solution. Other parts of a structure of tools, like network tools, debug tools, simulators, documentation tools, etc. A few years ago, PLC open therefore has decided to realize interfaces towards these support tools. This resulted in a workgroup TC6 for XML (eXtended Markup Language). With this, an open interface between all different tools will be defined.

“We want to be able to transfer the information on the screen - showing not only text but also graphical information (where are the blocks and how do they connect) – to other platforms.

The program has to remain as it is designed, and not be altered during the transfer.” says Eelco van der Wal. “The big variety of possibilities has to be brought under one umbrella.”

STEP can be looked at as an earlier version of XML, but the graphical part was limited. “We used the STEP protocol for our Portability Level, but were stuck in the lack of graphical definitions” adds Eelco van der Wal. “We want to accomplice that with -one push of the button- we can transfer a project from one development environment to the other, without loosing information” explains Eelco van der Wal. “And XML provides the right tool for this”.

As such it will be more than an export / import tool from one development environment to another. From the moment onwards that this format is available, it is just a small step to feed for instance a documentation tool. Actually, it is not important where this XML-code is coming from as long as it is recognizable and useable. So it could be generated by for instance simulation and modeling tools, and consumed by verification, documentation, and version control tools.

“With this we create a complete new market, in which the focus is on reusability of developments. All information will be exported. It is up to the intelligent import function of a tool, which parts of this information is useful and which need to be imported and used.” concludes Eelco van der Wal.

And in the end….we get a conclusion

It is clear that the organization PLCopen goes well beyond the development environments with these activities. PLCopen has effect on the way the controls are being used, programmed, connected, and looked upon. Nobody in this industry can ignore this trend for the next coming years. Users have to understand that they have to play an active role in these developments too. They can contribute, so that their existing needs fit existing environments, and their future needs fit into environments which are perhaps not even known now, because it is not known yet what is new. PLCopen can help them to get there.