1660253219201 Fractalfutureabstract

Control your design

April 29, 2021
How will you program your machinery control in the future?

I participated in the 2021 PMMI Executive Leadership Conference. PMMI stands for Packaging Machinery Manufacturers Institute and is now known as the Association for Packaging and Processing Technologies.

It is a community of machinery manufacturers, and the event I am honored to be selected to attend is a yearly gathering to put the executives of packing-machinery manufacturers together with executives from the world of consumer-packaged-goods (CPG) manufacturers.

Unlike the previous events that I participated in, such as the Top to Top Summit in 2017, this event was an all-virtual event. While I have participated in other virtual meetings, this experience was the first time where there was an audience in attendance.

Generally, I am not a fan of the virtual event. I do acknowledge that the still-present pandemic has altered the way we normally conduct business, but I do find that virtual events for me just don’t cut the mustard. I suppose I am old-school but I do like to see people in person.

With my proximity to Chicago, I am fortunate to be able to catch the trade shows when they cycle through the city, and I very much look forward to the years when they are here. PackEx has always been a feature event for me. My years as an OEM/integrator has blessed me with a long list of former colleagues and vendor partners, so my attendance at this show is as much an opportunity to reconnect with old friends as it is an opportunity to catch up on the latest technology.

Working now with a manufacturer of consumer packaged goods, my background with the packaging-machinery manufacturers gives my employer an advantage when it comes to selecting partners to help us along the automation journey.

As one can imagine, when participating in a leadoff meeting with CPG manufacturers and machinery manufacturers, there were a lot of questions about the state of the industry. We fielded questions about the increase in demand for our products, working remotely, the prospect of allowing a machinery vendor to remotely access our packaging equipment and the impact on the supply of components during a pandemic.

Two interesting sidebars came out of this kickoff session. First, right in the middle of a pandemic, a major automation hardware vendor had learned of a vulnerability via an Ethernet connection to its processors. Second, as a direct result of the pandemic and mirroring the impact that we all seem to be experiencing right now, having to temporarily shutter manufacturing plants due to loss of employees or virus transmission protocols, there is a worldwide shortage of the computer chips used in automation products.

Both of these situations can make a serious impact on the decisions made while designing and, importantly, choosing which control software will be used to operate the machine or process.

The control of automated processes has changed a lot over the years. One might immediately think of the programmable logic controller (PLC) for automation control, and that would be reasonable. First introduced to the automotive industry in 1968, the Modicon 084 would be the ground-zero moment for programmable controllers and a ground-breaking event for General Motors, the client for that first project.
Designed by Bedford Associates, it was their 84th product, and the 84 moniker would be carried through all the successive generations of that venerable product line. One of the lead engineers on that project, the late Dick Morley, is affectionately acknowledged as the father of the PLC.

The key element in the early PLCs was the use of a programming language called ladder logic. Hardwired, control-system schematics resembled a ladder where the rungs represented the steps of logic that made up the control. Ladder logic followed the ladder format where inputs (switches and contacts) closing, directed power to flow from the left side of the ladder to the right where the outputs (relays, timers, contactors, valves) would reside.

The benefit of ladder logic was that, while switches and relays came with a specific number of contacts, computer logic did not. You could use as many input or output contacts as you needed to make the control algorithm work.

Behind the scenes of every programming interface is an assembler that converts the human readable code into executable machine code (chip level). As powerful as ladder logic can be, it has limitations. The created algorithm is only as sophisticated as the elements that are available to the programmer.

Normally open, normally closed, latching relay are terms that are used to describe the visual symbols that ladder logic provides. Timers, counters, math functions make the ladder logic more elaborate. With all of these, the assembler still has to translate that logic into machine code to download to the processor.

Early on in the evolution of the logic controller, hardware manufacturers realized that, while the ladder-logic interface could accomplish a lot, being able program in something much closer to the finished (assembled) machine code would provide a far more powerful means of programming.

Some hardware manufacturers provided a pseudo-programming method by providing a means to enter code in mnemonics. Mnemonic code is a textual representation of the ladder logic. For those who are handy with a keyboard, mnemonic code can be entered at a much faster rate than picking symbols out of a toolbox and then entering the memory address to be used with it.

As most of us are aware, the development of the personal computer (PC) paralleled the development of the programmable logic controller. Some might remember early code development for a PC using a language called Basic. Other more powerful languages such as Cobol, Pascal and Fortran all existed around this time. These programming languages have something in common in that they used structured text (ST) to format the way in which the code is represented on the screen. Over the years, more powerful versions of ST programming languages have evolved to the point where we are at a crossroads in the programming of a control system.

The latest technologists and engineers coming out of our educational institutions are already familiar with structured-text programming, and it seems like a step backward to have them learn what must seem like the archaic ladder-logic programming technique.

Without naming names, it is safe to say that all programmable-controller manufacturers have directed their product evolution to accommodate the “archaic” world of programmers such as myself who have gotten very creative with the use of ladder logic while opening up the architecture to permit the use of structured text in everyday programming opportunities.

While it is clear that the hardware folks are making every effort to keep the old-school programming method available, it is clear that there will come a day where it will become necessary to abandon ladder logic in order to use the advanced features only available via structured text.

You’ll find industrial computers that can communicate directly with I/O systems—the same I/O systems that previously were part of the backbone or chassis of a PLC-based system. These soft PLCs allow for the inclusion of other software to run concurrently with the control algorithm.

Commercially available software for things such as inventory control or code printers can run and interact with the controller program in a seamless system that eliminates the need to develop code in a PLC to trigger the operation of a printer or database retrieval program.

You will find PLCs have evolved into programmable automation controllers (PACs) to signify the inclusion of programming means other than ladder logic. You will find PACs that include an embedded but independent safety controller.

Finally, servo drives now include a logic controller so that a separate PLC or PAC is no longer required to control a system.

The method by which we control a machine or process is no longer a limited field of choice. We can stick with a ladder-logic-based system. We can choose a hardware platform that utilizes structured text. We can choose a programmable automation controller where we can use a commercially available programming software to create our control algorithm. If we are more comfortable with programming in a servo controller, we can now choose to stay in that comfort zone and control our entire machine or process with the servo controller and the central control point.

It’s important to consider the end user in this process. While the choice of structured text or commercial programming software such as C++ or others might be the quickest way to get to the desired solution, some end users may not be equipped to support a control design that uses this approach.

Ultimately, we are selling a solution to a client and their comfort with the solution is an important consideration with implications after the sale.

I also alluded to the now, very real impact of a shortage of chips and what it does to control design. The selection of a control software may depend, at least for the near future, on the availability of the hardware platforms that we count on.

The common lament from both CPG manufacturers and PMMI members was the direct impact on the ability to meet deliveries and project timelines. Many manufacturers make their own control systems in addition to working with machine vendors with their control systems.

How long this backlog will exist is the greatest question in the controls industry, but it surely will have a lasting impact on how we go about control. If we choose, for instance, to go with a servo with embedded controller because we can get that hardware today, will we go back to the more conventional means of a PLC/PAC controlling a system?

Will we, instead, jump into the soft-PLC platform on the assumption that industrial computers won’t suffer from the delivery issues that currently plague the PLC users?

The world is changing, and, perhaps, the days of ladder logic are over. It will be important to make sure that the vendors of control systems are ready to provide greater support to their clients while we transition through this journey from PLC to IT. It’s sure to be an exciting time for all of us in control design.

About the author: Rick Rice
About the Author

Rick Rice | Contributing Editor

Rick Rice is a controls engineer at Crest Foods, a dry-foods manufacturing and packaging company in Ashton, Illinois. With more than 30 years’ experience in the field of automation, Rice has designed and programmed everything from automotive assembly, robots, palletizing and depalletizing equipment, conveyors and forming machines for the plastics industry but most of his career has focused on OEM in the packaging machinery industry with a focus on R&D for custom applications. 

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