Putting the Human First in HMI Design

The Challenge for Designers of Human-Machine Interfaces (HMIs) Remains a Balancing Act

By Keith Larson

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While the first distributed control system (DCS) represented a step-change in process control capabilities, it was a mixed bag at best for the process operator.

Gone was his familiar wall-full of analog electronic controllers, immediately recognizable as all "lined out" when the plant was running properly. Instead, he peered with reduced visibility through a much smaller CRT, toggling among simulated controller faceplate displays and process graphics peppered with alphanumeric data, granular detail sometimes obscuring the big picture view of overall process conditions. Instead of encouraging collaboration like the old wall did, others had to crowd over his shoulder just to see what was going on. And if something actually did go wrong, cascades of too many alarms (that now came "free" with every measurement) made it even more difficult to determine just what was really causing the upset—and what corrective action to take.

Today, the amount of raw data available to operators continues to explode even as the scope of operator responsibilities increases. Now as then, the challenge for designers of human-machine interfaces (HMIs) remains a balancing act: How do you make sure that operators are presented with all the information they need to make a timely decision, while excluding what they don't? How do you make deeper levels of process and plant data readily available, but prevent the obscuration of critical alerts? How do you make navigation of integrated information from the process control system—as well as dozens of complementary plant information systems—intuitive, seamless and context-sensitive?

Toward 'High-Performance' HMI

ABB's approach to improving operator effectiveness through high-performance HMI includes a range of technologies and industry best practices implemented in its System 800xA Operations environment. All are focused on boosting operators' situation awareness—and their correct and effective response to abnormal conditions. Better situation awareness can reduce the time it takes plant operators to complete required tasks during a process upset, and even allow operators to detect and intercept unfavorable process trends before alarm bells sound.

System 800xA allows customization based on users' preferences and needs with individualized menus, toolbar contents and display locations. Custom, role-dependent workplaces present information consistent with individual work processes and appear automatically on user log-in.

Windows management functions such as safe areas and the pinning and stacking of priorities help manage multiple process views. A new trend display always opens in the same window as the previous, and an alarm list is never covered by another view. As well as saving time and minimizing stress, this no-surprises view-handling simplifies the use of multiple monitors so that operators can supervise and control larger process areas with the same efficiency and safety. Within the displays themselves, information can be mixed and matched regardless of source.

Today's System 800xA process graphics not only provide graphics builders with better engineering tools, they also give process operators a much-improved image to view. True vector graphics, for example, enable scaling with maintained resolution. This effect is especially appreciated when operators need to scale-down graphic image windows to fit several on one screen.

Through the system's underlying Object and Aspect technology, the 800xA provides intuitive and easy access to all integrated information through a simple right mouse-click. Consistent, one-click navigation gives process operators more time to act: instead of spending time and energy looking for information, they can concentrate on informed decision-making and can share data with colleagues and field operators.

Trends Analysis and Alarm Management

Recent performance visualization is yet another System 800xA feature that improves operator insight. This HMI function displays the recent performance data of an object right next to the object graphic and its current status. Having recent operating values side-by-side with real-time status can alert operators to deviations before they develop into something more serious. Recent performance graphics can be shown at all times and for all objects — operators don't have to call up dedicated trend display windows.

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