HMI design is the practice of creating HMI displays that are clear to the end user, visually appealing, and easy to use. HMIs have become easy to install as control systems in production have shifted from old push-button models to being mostly operated by HMI displays.
Despite the huge variety of HMI-based systems available, the fundamental principles of excellent design remain constant. Distinct businesses may require different layout patterns for their systems, but basic practices remain. One such great practice is to get help from an automotive HMI design and development company, but if your desire to create an HMI by yourself is stronger, then take a look at some best practices we’ve gathered.
Unless you have a simple alphanumeric display, programming bare metal will be difficult and error-prone. By enabling interface development tools and library functions, the availability of real-time operating system (RTOS) assets will considerably accelerate HMI development.
During the design phase, you can only make assumptions about what is important to the drivers. However, you would gain more exact information if you conducted short interviews to understand their point of view.
Rather than cluttering the screen with extraneous information, concentrate on the critical operations. Inquire about the main things you should add to help them comprehend the state of the machines or the process. Instead of delving into specifics while creating the screen, consider the operation as a whole.
Designing a prototype and testing it with drivers would be the best solution. Examine how people interact with it and look for pain points. Reduce the number of steps needed to execute a process. Can you provide any more features that would make the driver’s life easier?
Speaking with drivers can help you see the big picture when your perspective is clouded by the details you must consider. The driver will be the end-user of your HMI design, so keep that in mind at all times.
Many HMI guidebooks advise utilising low contrast grey backgrounds and restricting the use of colour. This results in a much cleaner screen. Consider a light grey screen background with a typical indicator that is dark grey when turned off and white when turned on. This is pleasing to the eyes and makes sense because a lamp turns white when switched on. Only use strong, rich colours to denote dangerous situations.
Begin with process diagrams for monitoring and controlling HMI software development. Create an HMI diagram that includes the information and objects that will be presented on each screen of the HMI. The HMI diagram is an excellent tool for ensuring that you are on track to complete everything required for good HMI performance.
Only display the most critical facts on a single screen. For example, in a chilled water loop, you should display the basic loop design, the chiller status, the pump status, the temperature, and the pressure. Other metrics, such as pump speed or amperage, should be displayed in a pop-up window or elsewhere so that they do not distract from what you really need to see. Nobody wants to have to look for the information they require.
A text-based template detailing the content of each screen is a good start point for HMI design. Detail the main screen, gear status screens, set point or menu screens, manual operations, message displays, and problem displays with the driver’s perspective and simplicity of use in mind. These text templates can then be used to create a storyboard for each screen.
Dynamic images, such as status indicators, should be highlighted in the storyboard. It should also have repeating visuals at the top of the screen, such as titles, and navigation buttons at the screen’s corners. The buttons, indicators, and numeric displays on the screen should be properly aligned and arranged. Mixing screen selector controls with start/stop pushbuttons, for example, is not a good idea.
Data presentation is an important aspect of HMI design, and various data will demand different display styles. A number on a screen may show speed precisely, but its engineering units and the allowable range might be unknown. This can be solved by adding units, such as inches per second, as well as the maximum and lowest speed limit values.
The adage “a picture is worth a thousand words” applies perfectly to HMI design. Drivers can understand the significance of an image much quicker than they can read the words on a dull grey button. Pictures become even more significant when there is a linguistic barrier. Because C-more HMIs support overlapping objects, think about enabling a little image to overlay a button. A Bitmap Button Object is also an option, which allows you to utilise a built-in visual or create your own user graphics for the “ON” and “OFF” states. Keep in mind that huge visuals and animation effects might slow down the performance of a certain screen, so use them carefully or isolate them on other screens to guarantee fast response times on the major control panels.
Ensure that relevant data is shown properly so that drivers can rapidly understand the current condition of the machine or process (or as quickly as they need to). A good display responds to both the question of “Where is the data/process now?” and “How does that compare to appropriate conditions?” Displaying data with respect to the current state of the machine may be sufficient for discrete manufacturing. But for more complicated machines or processes, the screen design and layout should attempt to help the driver predict the future status of the car. Is knowing the present temperature of the oven really necessary, or would a trend graph help the driver to predict/prevent an impending disaster?
Provide visual (and audio) cues to the driver indicating that controls have been pressed or that specific tasks have already been completed. Positive feedback can increase trust and satisfaction with the system. If necessary, use colour and/or animation to guide drivers through complex tasks. However, keep things simple and avoid needless complexity. From the driver’s standpoint, there are two good things to ask: “Where do you expect to find that?”, as well as “What do you expect to happen?”
Set aside a section of the screen for these controls, like a band at the top or on the side, and ensure that this zone is totally consistent everywhere it is showcased. C-more includes a “background screen” function that enables designers to develop, modify, and manage such an area in a single spot inside your project layout, and then show it across several screens as needed.
Be careful to use pop-ups rarely, if at all. Nothing is worse than a series of error warnings that must all be acknowledged individually before the driver may proceed to the screen where the problem can be remedied. Other methods for attracting the driver’s attention include merely changing the backdrop colour of an object or area of the screen, or flashing objects, although this also should be used sparingly. The overuse of flashing or blinking effects can make the driver accustomed to them, reducing their usefulness as an alert, or possibly distracting the driver from a more significant issue elsewhere on the display.
When was the last time you received an instruction manual for your smartphone? It does come with some warranty and safety warning documentation in the box, but you can normally push the large button on the side and know how everything works.
A similar notion should be considered while designing an HMI. The use of simple graphical icons in place of words may even eliminate the requirement for translation. Consider the device’s screen size; employing images eliminates the need for consumers to squint to see the text. But be careful not to overload the consumer with information simply because there is screen real estate available. Layers can be used to organise detailed information; nevertheless, it is best practise to nest no more than three layers.
Create a collection of standard styles to stay consistent across all HMIs in a specific factory or facility. The consistent use of identical indications, visuals, trend objects, and so on helps improve driver familiarity and comprehension. C-more has an object library as well as a screen library where you may save (and share) proven elements – or entire screens – for simple reuse across numerous projects.
There are numerous approaches to developing HMI screens for machine control and related applications, but proper deployment necessitates design discipline. ISA, ASM, ISO, NUREG, and other organisations have released guidelines, standards, and handbooks on HMI best practices and design. All of these standards cover a wide spectrum of HMI design, build, operation, and maintenance approaches. Many people also talk about the equipment’s or process’s safety, quality, dependability, and efficient control under normal and unusual conditions. These standards can be used to develop internal company HMI design principles, which can then be used to develop uniform and functional HMI screens from one machine or project to the next.
Many aspects of hardware and software must be considered while designing an HMI. The goal is to provide an intuitive, efficient, and system-specific experience. When selecting an HMI terminal, it is critical to examine protocol requirements, hardware features, and system parameters. Before constructing the system, one must consider the navigation layout and the screen layout. The navigation determines how the user moves between the various displays, while the screen design determines how efficient the usage is.
HMI design is a form of art. However, it adheres to a number of fundamental concepts that may be found across a variety of businesses.