Automation interfaces advance

Human-machine interfaces (HMIs) and other operator interface devices are being pushed to the edge of rugged applications to combine the best features of classic interfaces with modern commercial technologies.

By Benson Hougland, Opto 22 October 4, 2018

Operator interface devices are a crucial element of industrial automation, but many common solutions suffer from shortcomings and implementation obstacles. New options ruggedized for use on the edge of industrial and other critical applications combine the best features of classic interfaces with modern commercial technologies to meet user needs.

Industrial automation systems for machines and processes must monitor conditions, command devices, and coordinate control. Designers implement these functions by combining a wide range of industrial automation technologies, such as sensors and instruments, input/output (I/O) modules and digital controllers. Even the most advanced machines don’t run by themselves, which means some form of operator interface must also be provided with the automation system.

Early operator interface solutions consisted of panel-mounted pushbuttons, switches, lights and meters. As technology progressed, these gave way to electronic and digital devices. In particular, the increasing availability and capability of PCs in the 1980s introduced a wide range of flexible options, but there were many specialized and proprietary devices, as well.

Electronic devices allowing operators to interact with automated systems became collectively known as human-machine interfaces (HMIs). Sometimes a more dedicated device built on a non-PC computing platform might be called an operator interface terminal (OIT).

Incorporating HMIs and OITs into automation systems is crucial for many reasons. They offer far more interface options than simple panel devices, and if change is required, the HMI or OIT can usually be reconfigured or reprogrammed for a lower cost than cutting holes and installing new devices in a traditional control panel.

However, this kind of increased operator interface functionality still had a few shortcomings and made HMIs costly and difficult to maintain. To address these shortcomings, the latest HMI products are engineered by learning from the past while taking advantage of the latest commercial technologies. They offer a rich user experience and familiar features while overcoming the challenges of traditional devices. 

Traditional HMI, OIT challenges

First generations of HMIs and OITs focused on letting users start and stop equipment, understand how a system was operating, and make adjustments. The digital nature of these devices soon enabled them to do far more.

Alarm and event logging, historizing data and displaying trends were capabilities added over the years. HMI and OIT configurations could be copied and saved, and a new device could be deployed relatively quickly if the old one was damaged or failed. Improved networking capabilities, especially Ethernet and Wi-Fi, meant HMIs no longer had to be installed in physical proximity to machinery. Multiple HMIs could be installed at a site to provide interfaces in the control room, at the machine and in engineering offices.

These HMIs and OITs offered many benefits compared to hardwired panel devices, but also demonstrated a few downsides. These challenges included:

  • Limitations of proprietary hardware and software
  • High initial costs
  • Ongoing support and maintenance costs
  • Licensing complexity and cost
  • Extensive engineer and operator training
  • Effort required to integrate multiple platforms
  • Lagging technology.

Dedicated OITs are likely to employ proprietary hardware and software (Figure 1). Manufacturers offer these devices to provide an adequate control system interface experience in a relatively self-contained package. Since they are specialized for the industrial market, they don’t enjoy the commercial benefits of scale provided by consumer electronics, making them more expensive on a price-performance basis. However, they are usually built to withstand the industrial environment and offer a practical, serviceable solution.

As more advanced PC-based HMIs became available, the hardware was perceived as a good value compared with prior solutions, and provided flexibility and connectivity for the user. One downside, however, was increased ongoing maintenance and support requirements including:

  • The operating system (OS) and other software needed periodic updates and protection against malware
  • Non-hardened hardware was not suited for typical industrial conditions.
  • PCs used as HMIs typically ran vendor-supplied software, which entailed licensing costs and periodic version upgrades. (In many ways a basic OIT is more "ready out of the box" than a PC, which requires configuring a commercial OS and the HMI software.)

Perhaps even more than PCs, the proliferation of mobile consumer devices has struck a blow against classic industrial HMIs and OITs. Smartphones, tablets, and other products have raised performance expectations. Users now expect a polished look and feel, frequent free updates, and improvements to the device’s operating system and applications (Figure 2).

But innovation is somewhat slower for the industrial market because it is relatively small compared to the much larger consumer market—not to mention being far more conservative than the cutting-edge personal electronics market. Often, end users feel HMI and OIT products are "old tech," when they have been conditioned to yearn for "new tech." 

New HMI technologies

The latest generation of HMI products addresses each of these deficiencies by adapting commercial technologies, while including and building upon all the best features of previous generations of HMIs and OITs. Potential benefits include:

  • Economical open-source underpinnings
  • Affordable configuration software with no licensing fees
  • Ease of use · Integral controller screen providing an economical and capable local platform
  • HDMI connections to enable a larger local display, if needed
  • Networking, cloud-based connectivity, and web-based visualization to extend the reach of HMIs
  • Mobile devices for the ultimate in flexibility.

Let’s look at these benefits in more detail.

Open source: Ideally, a modern HMI combines the robustness and ease-of-use of a traditional OIT with the power and value of a PC-based HMI. This combination becomes possible when the hardware platform is based on a real-time open-source OS like Linux, which requires no purchase or license fees. Small footprint, hot-swappable components, local LED indicators, and other practical touches can make this platform field-friendly. Designed properly, the hardware is right at home, even in a challenging industrial environment, while providing PC-level performance.

Affordable configuration: Customization is possible, but not required, because modern HMI hardware includes built-in, standard functionality to meet most needs. The PC-based HMI configuration software is affordable and there are no restrictive licensing fees. The end user can concentrate on applying the HMIs where they fit best without worrying about limiting tag counts or runtimes.

Ease of use: A suite of development options makes modern HMIs easily approachable for new developers to create basic applications, but completely extensible for advanced programmers to develop custom applications using optional secure shell access. Original equipment manufacturers often need this type of flexibility for coding machine-specialized and even proprietary algorithms in C/C++, Python and other languages. Integral screen and flexible ports: An on-board display available on some devices might be more than enough HMI for many applications, although an HDMI connection allows for a larger local display if needed. In addition, multiple Ethernet and USB ports, as well as I/O modules, facilitate connectivity to any field devices or systems.

Networking and cloud-based connectivity: Even more power can be realized from modern HMIs when users take advantage of network and cloud-based connectivity. Data can be securely shared among databases and systems, and HMI visualization can extend out to any authorized computer or mobile device capable of hosting a web browser.

Mobile devices: Mobility is another key component of modern HMIs. Once the base device is installed and configured, any mobile device can connect securely and become another HMI, which offers more flexibility for engineers and operators. Designers can focus more on what the HMI content and experience should be while being relieved of the expense and complexities of the underlying platforms. Moving from dedicated OITs and PC-based HMIs to mobile devices is seen as a natural progression by many. 

New HMI examples

Advanced HMI products that help end users meet automation goals include an edge appliance, a server for Microsoft Windows and a programmable industrial controller system designed for use on the "edge" close to application measurements. These products provide a scalable way for deploying the best features of OITs and PC-based HMIs, while avoiding the costly and complex issues associated with traditional products. All three of these products include a web server for connectivity to any device capable of hosting a web browser such as a laptop, smartphone, or tablet.

The edge appliance is an Ethernet and USB plug-in device, which allows designers to build connectivity and data handling applications for automated equipment and Internet of Things (IoT) devices. It doesn’t contain a screen for local viewing. Instead, it connects to other devices with screens that act as HMIs.

groov Server for Windows software offers a way to view screens on its host PC, as well as on remote devices. The system adds control programming, I/O modules, and an on-board HMI to the feature set. (Figure 3 offers an example.)

The product can be mixed and matched while enabling secure visualization on any device capable of hosting a web browser without being encumbered with limits on users or tags.

HMIs and OITs have advanced to play a vital role in automated machinery and industrial processes. While there are many benefits to implementing these products, there have been some nagging concerns related to initial and sustaining costs, proprietary hardware and software, and maintainability.

The newest generation of HMIs combine the best features of traditional products with modern open-source hardware, software, and networking technologies to address these issues.

Since these new HMIs can also be readily and seamlessly networked and deployed to any typical mobile device, end users are finding today’s technology is meeting their needs at a price they can afford.

Benson Hougland, vice president of marketing, Opto 22. Edited by Mark T. Hoske, content manager, Control Engineering, CFE Media,

KEYWORDS: HMI, Edge devices

  • Operator interface devices have implementation obstacles.
  • New edge devices can be easier to setup and use than traditional human-machine interfaces (HMIs).
  • HMIs help connect sensors, instruments and actuators with logic.


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Author Bio

With 30 years’ experience in IT and industrial automation, Benson Hougland drives strategy for Opto 22 products connecting the real world to computer networks. Hougland speaks at trade shows and conferences, including IBM Think, ARC Forum and ISA. His 2014 TEDx Talk introduces non-technical people to the IoT.