HMI Design: Five Simple Tips

HMI Design: Five Simple Tips

SCADA systems are built around data. As the complexity of plant automation processes increase, so have a SCADA’s ability to process increasingly larger amounts of data. Unfortunately this usually results in a cluttered HMI, causing operators to be overwhelmed with data.

Most of the cutting-edge innovation in HMI design in recent times have come from, unsurprisingly, smartphone operating systems; and there’s a lot we can learn from them when designing an HMI for SCADA systems. Here are five simple tips in designing a killer HMI.

1. Make analogue controls more digital

It’s easy for a system integrator to design an HMI that simply mirrors the behaviour of hardware controls on a shiny, high-res touch screen. Early smartphone OSes have in fact adopted a so-called skeuomorphic design (graphical user interface objects that emulates the aesthetics of physical objects), but have quickly dropped that in favour of a flat design, reducing three dimensional design cues to a minimum.

While sometimes it may be the only option when presenting a set of controls, mimicking hardware is definitely a missed opportunity to rethink the way the operator interacts with the plant.

2. Focus on the KPIs

Overview screens on an HMI are like car speedometers; it is essential to get the information you need in a glance. Use subtle nuances to highlight abnormal conditions that require manual intervention. Only display the main KPIs of the plant on the main view, i.e. production output, downtime, and safety. For example, for a railway network, you might want to display the voltage of the tracks, the speed and location of each train in the network, number of passengers, or even the punctuality of each train in terms of delay in seconds.

Do not neglect the additional data that are not displayed on the main screen. They may not be critical to the KPIs, but turning those data into actionable information would definitely present a significant increase in productivity and response time.

3. Get the stakeholders involved early

What makes a good HMI? No one can say for sure, since each one is tailored to a specific use; but an HMI designed with the users in mind would definitely deliver a better outcome than one developed without user involvement. Be clear about the design direction with your users from the early stages. Reuse the back-end controller logic if it has been relatively stable for many years. Let users try new builds out, listen to what they want.

What if it’s too difficult to use? Identify whether it’s a problem with ergonomics, or just a habitual issue that users will adapt to after some time. User feedback prevents designing an HMI that only the designer understands, but take them with a pinch of salt. A quote allegedly associated to Henry Ford, the founder of the Ford Motor Company states that, “If I asked people what they wanted, they would say ‘a faster horse’,”. Ultimately, you should make the final call.

4. Be intuitive

When was the last time your smartphone came with an operating manual? It does come with some literature on warranty and safety warnings in the box, but generally you intuitively hit the large button on the side and know how everything works.

An HMI should be designed with a similar concept in mind. Replacing words with simple graphical icons may even eliminate the need for translation. Also consider the screen size of the device running the HMI; using graphics means users do not need to squint to read text. Beware though, try not to overwhelm the user with information just because there is existing screen real estate. Employ the use of layers to organise detailed information; though it’s best practice to nest fewer than three layers.

5. Be creative…?

We can’t argue that HMIs for a SCADA systems wouldn’t hurt if they were more aesthetically pleasing, but adding a splash of colour or having a futuristic jet black interface would probably not be the best practice in designing for process controllers.

Use subtle colours to pull the user’s attention to actionable processes, consider implementing a dark mode for users working in environments without proper lighting, design larger buttons for users that wear gloves. There’s no one-size-fit-all interface, so be creative and come up with original ideas; if you can’t, you can always copy someone else’s homework…?

Once more we turn to our friends, the smartphone OSes. Since literally everyone uses one, it would make sense to design a similar interface; one that users are familiar with and would immediately feel at home. Moreover, these companies, i.e. Google and Apple, have invested billions in this and even published guidelines on their findings. This makes even more sense when you consider that web SCADAs like Ecava IntegraXor are designed to run on smartphones anyway.

There is no perfect HMI though. There’s not even a perfect HMI for a specific use case since each operator has a different mental model. The only thing we can do as designers is to craft an HMI that fits around the majority of users, rather than convince users to work around it; the robot overlords do not rule the earth. Yet.