What characterises a good Human Machine Interface?

The path towards an optimised HMI design.

What characterises a good Human Machine Interface?

Where (exactly) do I have to click on this window in order to change parameters? And why should I confirm this message (again!) with OK? This step is completely unnecessary.

What's the reason for an experienced plant operator for being so perplexed in front of the operating panel of a machine? Often, a complicated Human Machine Interface (HMI) is partly responsible for the breakdown in human-machine interaction.

This is especially true for manufacturing companies: Well-designed HMI concepts are becoming increasingly important and have become a financial consideration not to overlook. A user interface that's consistently tweaked for the target audience avoids errors, reduces downtimes, and slashes support and training costs. In short, an intuitive HMI makes machine operation both safer and more productive.
Nowadays, however, HMIs must do more than just provide convenient operation: On the user side, there's a growing demand for a positive usability experience, as is known and expected from mobile applications across the consumer world. An intelligently designed HMI testifies to innovative strength and technical excellence and has actually become a business card for the machine manufacturer. Or, to frame it another way: a machine with innovative functions requires a modern HMI.

What challenges do machine and plant manufacturers face?

The current trends in the industry represent both an opportunity and a challenge for manufacturers. It can be observed that progressive digital connectivity within the manufacturing process means that operating concepts no longer only have to function for individual machines, but also across entire ecosystems. This results in entirely new tasks for software engineering: How can we integrate mobile devices into a more homogeneous concept? Can we inspire users with additional digital services? And how can we standardise user interfaces across entire product portfolios, in order to create a consistent user experience?

Taking all considerations into account, one aspect should always appear near the top of the list: An HMI will only be accepted by users if its operation is intuitive, logical and transparent. This, in turn, requires a strict user focus and consistent usability thinking from the developers – not an easy task in the stressful everyday life of a software developer.

Ways to optimise HMIs: Using existing know-how

The good news is that many companies already have specialists on staff who are passionate about the comprehensibility and usability of digital information products. Most of these people are technical editors.

What makes them so valuable for the interface communication between expert and user? As professional knowledge brokers, these people specialise in structuring and preparing technical information for maximum user benefit.
We at kothes are therefore convinced: With the methodological-didactic expertise of technical editorial professionals, HMI design can be optimised as early on as the conception phase!  

So that it doesn't just remain a theoretical thought exercise, we naturally wanted to test our thesis in practice. How did we go about this?
Our primary approach was to develop a sound and (at the same time) practical analysis tool for the usability of HMI concepts. With the help of our solution – the so-called HMI Check – manufacturers should be shown very concrete approaches for HMI optimisation.

The theoretical superstructure of our HMI Check is essentially based on DIN EN ISO 9241-125 and DIN EN ISO 9241-110 standards, which define comprehensive recommendations for the ergonomics and usability of interactive systems.

How exactly does the procedure work in practice?
We were able to carry out the first test runs of our HMI Check, together with our customers. The following procedure proved to be ideal: In a first step, we analyse the usage scenarios and target audiences that are particularly relevant for HMI operation on the respective machine. From these factors (e.g., environmental conditions, work objectives, and work methods of the various user groups), we can then derive the specific requirements for the HMI.
In a second step, we define typical use cases for operation that can be used to test the functionality and usability of the HMI particularly well (e.g., setting parameters, loading and adjusting recipes). For the actual usability testing, we finally put the HMI of the specific machine through its paces.

What are the main criteria we look at during the HMI Check?

  • Recognisability
    The information is clearly recognisable and, if necessary, highlighted.
  • Clutter-free
    The information can be perceived without other information interfering with its perceptibility.
  • Distinctness
    The information can be clearly differentiated.
  • Clear interpretability
    The information can be understood as is intended.
  • Conciseness
    Exactly (and only) the information required to accomplish a task is presented.
  • Consistency
    Identical information is presented identically throughout.

We present the results of the HMI Check to our customers in the form of a comprehensive test report. This provides companies with:

  • Basic optimisation recommendations in the categories of design, terminology, navigation, information density and labelling
  • A detailed list of the results of the individual test criteria with additional suggestions for improvement

Keeping users in mind – right from the start

So what's our summary after the first few projects? Has the HMI Check successfully passed the practicality test? Thanks to the positive feedback from our customers' Development departments, we can answer this question with a resounding Yes! It's already apparent that:
The HMI Check provides manufacturers with valuable insights for optimising their operating concepts and can be easily integrated into ongoing technical editorial projects. We at kothes look forward to carrying the idea of the HMI Check further and supporting our customers in designing modern HMI solutions. Because one thing is certain: Aspects such as the User Experience (UX) and usability of digital information products will continue to become increasingly important in the future. Manufacturers must have a precise understanding of the requirements of the various user groups in order to be able to support them optimally within their workflows. It therefore pays off in the long-term to include the know-how of UX specialists as early as possible in the development process of new products.

Do you have questions about the implementation of user-centric information solutions? If you'd like to learn more about the concept of our HMI Check, then contact us: Our team of experts would be happy to advise and support you.

Steffen Vorderstemann
Blog post Steffen Vorderstemann