I traced the evolution of machine-control HMIs from monochrome CRTs, fixed screen grids and physical navigation keys to touchscreen interfaces with flexible, dynamic objects. But hardware and graphics tell only part of the story. An equally significant change has taken place in HMI development software, where the once-distinct approaches of machine control and process control are increasingly converging.

For process-control HMI products, the approach has always been to visualize the process in a graphical way. I’ve always thought of this as the bigger picture. Machine control is more of unit operation view of the world. Each machine has its own focus with specific screens to provide a means to interact with the equipment. Process control is more about the full scope of the operation with the executive view. I have a fair bit of experience with Wonderware software, which is now part of Aveva, and Simatic WinCC. There is a methodology with these systems in that they are more object-oriented with multiple instances of those objects making up the total system. Screens can be modified on the fly and deployed to the client stations with the operator rarely aware of a change being made.

Over time, the differences between a machine-control HMI and a process-control HMI have blurred to the point where there is little difference between the two. Hardware manufacturers help to integrate the two methodologies by combining the two approaches via the development software. Screen objects are multi-layered and have built-in functionality that would have taken hours to develop manually. Most major brands have a library of add-on objects that mesh well with matching data tags in the PLC. Of particular interest, the designer can create custom template objects that match user-defined tags in the PLC to expand that even further.

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Back when I was coming into the field of automation, the focus was on the component level design of a control system. This was a great foundation for the rest of my career but the most interesting class I took was in PLC programming. We did a simple project that started with a simple traffic-light system. We added to it to make it have advanced green and stop-and-go flashing signals like a real-life application. I bring this up because HMI development for me has always been about taking the building blocks and adding new features to them. The library after nearly 40 years in the industry is quite extensive, but I am finding that some of those custom blocks of code and HMI objects are now common objects offered with the software package. One might lament the work that went into those custom blocks, but I find that these now common blocks are the building blocks for future development. It is the software that makes this possible.

My favorite automation vendor came out with an HMI product a couple of years ago that is breaking the traditional barrier between machine and process HMI. The approach is from the process-control HMI side of things but incorporates the usual objects found in a machine-control HMI. I had some reservations when this first came out. I’m in a user group that gets to try out the software in an online environment where the developers watch me use the software without any direction on how to develop the objects I see on a sample screen. When participating in one of these sessions, I struggled with doing what I would say were simple tasks until it finally dawned on me that this is a process-HMI application that integrates the machine HMI components.

I wondered where the developers were coming from when designing this new software/hardware platform, and the answer was really quite simple. Students working their way through college don’t learn PLC and HMI. They learn programming languages and GUIs. Java, HTML5 and Python are the hot topics at school. Everyone has a tablet or a smartphone these days, and it occurred to me that the young people graduating from high school and college have a set of tools that I would not have even imagined when I graduated in the late 1980s. They are technically savvy at a level that is best leveraged by software development applications that speak their language.

Rather than lament the changes in HMI software over the years, I prefer to embrace them and realize that our future is bright, and I look forward to what the future holds.