According to Apple founder Steve Jobs, “Design is not just what it looks and feels like. Design is how it works.”
This is one of the guiding principles outlined in a series of videos by user experience expert Oliver Gerstheimer of Siemens. The goal of the series is to teach others great HMI design. From concept to prototype, each step of the design process is laid out.
A good HMI design goes beyond how it looks to also encompass how it feels and how well it works for the user. Done right, the HMI creates added value in terms of saved time, avoided errors, workflow efficiency and happy users.
The process begins by asking the right questions, understanding the actual tasks and getting to know the routine of those who will be using the HMI. By doing so, the designer better be ready for detours and multiple iterations, while also being prepared to discard what initially appeared to be bright HMI concepts. The focus should always be on the user, so the designer must avoid working from his or her own point of view. Take the time to see things through the eyes of those who will be using the system.
However, it is vital that HMI design not be left until the tail end of machine development. If it is little more than an afterthought, the end result will be poor. By starting early with HMI design, the machine itself can be improved. In other words, develop the equipment and the HMI in parallel.
Context in HMI Design
Success depends upon an understanding of context. The designer has to know who the various user groups are and what their requirements might be. Those who assume they already know their users are likely to make serious errors or produce HMIs that users dislike.
Identify the various user personas. By grouping the major user types, profiles can be drawn up that greatly assist the HMI designer. Analyze the tasks done on the machine by each group, the context of their work and their pain points. Prioritize these personas, too. Someone who uses the machine all day long is far more important than a supervisor who looks at it once per shift. Nevertheless, the needs of the supervisor or manager should also be incorporated into the screen layout.
Similarly, events and functions must be graded according to relevance and frequency. Relevant events are major occurrences that might occur only a few times a shift. This might be the beginning or end of a major process or an unscheduled stoppage, for example. Frequent events occur again and again. Each one might not be that important, but the operator performs them constantly. While there may be other use cases to examine, they should be given lower priority in HMI design than the most relevant and high frequency use cases.
Another point is environmental and plant floor conditions. Audio signals from the machine won’t work in a noisy factory. Light, too, can influence screen usability. Take these into account as part of HMI context.
Known pain points also must be addressed. Ambiguous error messages can cause the user to conduct a lengthy physical inspection of the plant floor. Therefore, such messages, dialog boxes and feedback items must be explicit. By giving due consideration to these points, it becomes possible to translate known machine pain points into positive user experiences, reduce the distance operators have to travel and to save operator time.
The HMI must mirror user expectations in terms of look, usability and workflow. And that’s not easy to do when staring at a blank screen. The designer should begin with paper sketches of the big picture instead of pushing boxes around on a computer.
A useful tip from Gerstheimer is to plan your HMI the way you would plan a house. It should have an entranceway that flows easily to the other “rooms.” Each room should be easily identifiable with its own characteristics. In other words, the main screen of the HMI should be self-explanatory and its navigation pane should lead intuitively to other functional areas.
The easiest way to achieve this is with multiple sketches. Laying them out side by side or posting them on a wall helps to highlight the workflow and identify any shortcomings in the initial concept. But don’t get too complicated. Sketch only the main interfaces at first. And lay out the screens according to functional relevance and frequency. Major elements should be prominent, minor elements should be placed in the background or to the side.
Just as light switches in houses are placed at the same height and at a uniform distance from door frames, place buttons such as “next” and “back” in familiar positions that are easy to find. Users shouldn’t struggle to perform common tasks that are hidden by too much HMI flash or originality. This is known as high expectation conformity. Deliver what users expect via consistency of design.
Tied into this is the avoidance of screen clutter. An HMI can suffer from too many elements. Therefore, designers should develop an instinct about how to use available space and how many elements can comfortably fit on one screen. Each screen should be divided into function blocks. In some cases, all blocks can be on one screen, and in other cases, the user picks only the relevant functional block which then appears in its own view.
However, the HMI is laid out, pay strict attention to alignment and spacing. Group and frame those elements that belong together without choking the page with information overload.
Dashboards are a popular way to highlight vital information at a glance. The icons, graphics and diagrams on a dashboard operate like a store window. The operator can scan it rapidly looking for something eye catching that demands attention. The number of elements, their spacing and placement are particularly pertinent in dashboards. Once again, pay attention to functional relevance and frequency. More space should be given to primary data, and less to secondary data. Key performance indicators, for example, should be centered.
These are only a few of the many points covered by Gerstheimer. Further tips include:
- Opt for a menu or a workflow based on context
- Design error messages that support the user in resolving issues
- Prevent user mistakes whenever you can
- Protect users from small clicks with huge consequences
- Test the prototype with users onsite
- Follow a task-based and explorative testing strategy
- Document the results in a concise report to support implementation of user feedback
- Don’t mistake your HMI for a coloring book.
- Don’t waste time with effects that are just for show
You can learn more about HMI design by taking the HMI Design Masterclass (seven 10-minute online videos) free of charge. Click here.Have an Inquiry for Siemens about this article? Click Here >>