A human-machine interface (HMI) can come in various forms and had its genesis in hardware and firmware. I remember Steve Rubin, founder of Intellution, which is now iFix, telling the story of burning programmable read-only memory (PROM) on his kitchen table as a system update. The core of an early HMI has always been software/firmware that interfaces with specific hardware in the same space.
The video cards were normal, and there was a DOS interface to the video memory to draw the primitives—lights, buttons—and then a communication driver poached data from the system controller, typically a programmable logic controller (PLC) to animate these primitives.
Enter 1990 and Windows 3.0. A small company called Wonderware was working with Microsoft and developed Network DDE so they were intimate with the operating system (OS). The PC had been out for eight years using DOS as its OS, and HMI software was being developed under DOS, which Intellution migrated to and was the de facto leader in the space until.
Under Windows, Wonderware created a whole new ball game. Using standard interfaces such as video drivers and serial card/utility card drivers, a new HMI era was born. And we have never looked back.
The HMI provides the same level of interface as always—pump on/off and alarming, for example. But it has so much more capability in this age of networking, wireless and edge computing.
HMI is typically located at the machine level and is strictly software-based using standard PC-based hardware and systems. Some can support different programming languages, and most support template-based configuration of screens that the operator interfaces with.
A typical HMI hardware platform is an industrial, or commercial, PC mounted in or on the control panel, but, of course, the visualization can be a mobile device such as a smart phone or tablet. Connecting wirelessly is an option here.
In recent years, HMI software has become mainstream in the fact that it can and does use commercially available tools and add-ons such as OPC UA for communication, so the screen and back-end processes can access multiple devices on the same platform, which typically would use Ethernet for connectivity. Again, software plug-ins would be used to integrate data from certain supplier devices into one HMI application.
A methodology that is thrown around a lot is edge computing, and the HMI is at the edge. What does this really mean?
An edge device is at the end of a network and has computing capabilities. In a previous life, the HMI would read data from the PLC, which would have been formatted by the PLC and displayed. This data would be recorded on a clipboard and sneaker-netted into an office for data entry.
Now, no clipboard should be implemented. The HMI can take the raw data from the PLC, format and put the data through algorithms created by scripting to produce a result that means something to someone or something like a database.
It’s where the database is located that is the game-changer. It can be located locally, but more often it is located in a server room in the plant. In recent years, data was mirrored from the server to the cloud, which is offsite to be made available for remote users.
Now, an HMI with Internet connectivity can use protocols reserved for server-based applications directly to send data to the cloud and to the third-party applications that use this data for a variety of decision-making instances.
HMI software is no longer a simple machine interface to an operator. It can interface to local back-end programs, such as a computerized maintenance management system (CMMS) or enterprise resource planning (ERP) system, and cloud-based third party applications directly and provide remote access for monitoring and control, if needed. Be aware that security will still be an issue in any or all applications that are Internet-enabled. In fact, some frown upon having a process window available to the Internet. Be cognizant of the pitfalls, and do your homework.
To paraphrase one HMI vendor, the future is limitless, as with most HMI software technology solutions. Artificial-intelligence (AI), augmented-reality (AR) and virtual-reality (VR) interfacing may become available. Machine learning is already here and in operation.
We have an important tool at our disposal. With the proper implementation, we can do anything. Really, we can.
