UX for the Industrial Environment, Part 1

The Control Room

A centralized control room presents its own host of challenges because operators must monitor a much broader swath of production from their workstation, as shown in Figure 2. It’s not uncommon for a single user to monitor six or more large HMI displays simultaneously. While the control room is a more controlled environment than that on the plant floor, many challenges exist. While an HMI for use on the plant floor should focus on the machine or process it’s monitoring—and allow more imprecise interaction—control-room HMIs must be more comprehensive. Users in the control room must have more of a bird’s-eye view of several processes or machine lines at once. Thus, it’s crucial to have a clear information hierarchy so things that need to draw users’ attention—such as problem states—are apparent at a glance. Users in control rooms don’t context switch as much as those on the plant floor, but eye fatigue can be a major issue for anyone looking at large digital displays throughout an eight- to twelve-hour shift.

Image source: CKLB Radio

HMI Design Principles

While the plant floor and the control room offer different contexts, goals, and challenges, there are several HMI design principles that can make information easier to consume in both of these environments. Here are some key principles for an effective HMI design regardless of the user’s environment:

Censor Graphic Violence

While visualizations might be better than alphanumeric data, that doesn’t mean they should be photo-realistic or skeuomorphic depictions of the actual production environment—a common characteristic of many poorly designed HMIs. Anything that doesn’t add value should not appear on the screen. This rule applies to any context. It’s important to avoid saturated colors, gradients, 3D effects, animations, and anything else that vies for the user’s attention. Figure 3 shows an example of a poorly designed HMI. Do the licking flames in the furnace, the cheery little tree in the upper right-hand corner, or the violently jagged edges of the burst vessels help users to understand the status of the process it depicts? What is the primary focus of this screen? Who can tell? Design trivialities add up to unnecessary complexity and visual noise, and they steal the user’s focus away from what’s most important—the information. If everything on the screen appears to have focus, nothing has focus.

Image source: Opto 22

Cut, Cut, Cut

Designers should be ruthless about removing extraneous design elements that neither provide useful information nor help the user understand that information. If something is not informative, it’s simply decoration that risks taxing the user’s cognitive load. Many user interfaces feature background colors, containers, and lines that aren’t necessary to assist a user’s comprehension of the information. A display that has unnecessary visual elements drains the user’s mental battery faster than a display that’s more intentional, showing only truly valuable information. To help the user get through the long haul, designers must nix the unnecessary.

Wield Contrast and Intensity with Care

An effective design helps the user stay productive by reducing eye fatigue, as the user’s eyes continually focus and refocus. You can ease the burden on the user’s eyes by reducing contrast between foreground and background elements and restraining your use of saturated colors. This is especially critical in a control-room environment where the user is viewing multiple HMI visualizations. You may think that the HMI shown in Figure 4 is a bit ho-hum, but it’s ideal for use over an eight- to twelve-hour shift when performance, uptime, and human safety are on the line. The mostly grayscale gauges and data values are well afforded, despite the user interface’s minimal use of color. The use of color is limited to outlining problem states, as shown in the upper right in Figure 4, with square shapes that outline information groupings that represent problem areas. The color values themselves are intentional as well. Because yellow, purple, and red differ in intensity, they differentiate states even for color-deficient users. Finally, the neutral gray background helps the colors stand out. While using a bright, white background is common in many consumer-facing user interfaces today, this creates luminance contrast issues for colors with lighter values and intensity—for example, yellow on a white background.

Image source: Schneider Electric

Use Color Responsibly

The use of color is one of the most challenging issues that industrial-automation UX designers face. Color draws the user’s subconscious attention, so is distracting. Therefore, you should use color only for things that must immediately stand out on the screen—such as an alarm condition or a problem state. Plus, the best design solutions redundantly code colored components with a label or an icon so their meaning is obvious—especially for use in suboptimal lighting conditions. Not everyone can reliably see the full color spectrum—one in twelve males have color-deficient vision. That’s 8% of all males on the planet. The ratio is more benign for women—just one in 200—but you get the point. When designers rely solely on colors of similar intensities, they unintentionally make users’ lives more difficult, especially when a problem state exists. Heavy use of color for elements that are unnecessary to the user’s comprehension taxes her cognitive load.

Use Gestalt Principles

According to Gestalt principles, designers should spatially group related objects and elements to allow the user to perceive the whole as a single unit of information. In Figure 5, logical spatial groupings of related data help make the information design apparent. You can also achieve Gestalt grouping through similarity—for example, by using consistent fonts and sizes for labels and values so the user can mentally associate them. Again, while it’s important to cut out uninformative user-interface elements, another simple way of conveying relationship is the principle of closure—for example, enclosing a grouping of elements inside a border or a box. As Figure 5 shows, the borders help reinforce informational relationships. In this example, spatial grouping of elements alone would not be sufficient to make their relationships apparent. Without the boxes, the various groupings of gauges and labels would run together on the screen, taxing the user’s cognitive load. While designers sometimes use closure to group related elements whose relationship would be apparent from spatial grouping alone, in this case, closure adds value because it’s informative and reduces cognitive load. Separating the various groupings of information doesn’t place any strain on the user.

Image source: Schneider Electric

Do More with Less

The HMI shown in Figure 5 doesn’t comprise photo-realistic tanks, pipes, and flames, but communicates effectively using graphic information. The user interface is simpler, but simpler doesn’t necessarily mean more white space. It’s simplicity comes from using vertical gauges, horizontal gauges, trend lines, and radial gauges to communicate the contextualized information. As I previously mentioned, graphic elements are often more impactful than a listing of alphanumeric values. However, that doesn’t mean using literal graphic depictions of the real-world environment. By visualizing information in the most appropriate way, you can contextualize information that helps the operator understand how it’s doing, how it’s been, and how it will be. For example, using a vertical gauge to represent temperature maps to most users’ existing mental model of how a thermometer works and why it has a vertical orientation.

Key Takeaways

The aim of many of these key design principles is to make content more comprehensible to the operator in the work environment. But users working in industrial automation typically view highly nuanced information, so the visualizations that users such as operators, maintenance engineers, and plant managers consume often exist outside the influence of UX professionals. Plus, there’s a tendency for the many HMI designers who aren’t UX professionals to design from a system point of view rather than leveraging the user’s mental model. I’ll cover this in greater detail in Part 3.

Design work usually occurs in office cubicles. It’s important to map your design choices to the user’s target environment because it’s different from your own. Optimize your product experience for the target environment and be ruthless about removing unnecessary user-interface elements that don’t add value. Be aware of what elements compete for users’ attention when they’re using your product. Information isn’t the same as data, and more white space isn’t the same as simplification. Be aware that the overuse of color—especially for information that doesn’t need to stand out—can make the user’s life more difficult because color draws subconscious attention and is distracting. Above all, censor graphic violence. If everything on the screen appears to have focus, nothing has focus.

Conclusion

For people who work in industrial automation, the environment itself presents obstacles, but these are just a few of the many obstacles in this domain. In Part 2 of this series, I’ll share some methods that industrial-automation UX designers can use to combat the challenges of designing for isolated customer sites, as well as the challenges of localizing information for global users.