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Everything you need to know about effective HMI development

(Image credit: Shutterstock / Zapp2Photo)

Whether you decide to launch a smart bracelet, self-service kiosk, or medical laboratory equipment, you’ll want to make your product appealing, functionally rich, and convenient to use. To incorporate all these capabilities, your solution needs a high-performance UI, top-notch functionality (for both hardware and software), smooth human-to-machine interaction, and a mix of other things expected when developing a single HMI unit.

Broadly speaking, an HMI (Human Machine Interface) is anything that has a graphical display and the possibility for a user to interact with a device — from the Alexa app with voice recognition to a complex plant-wide solution connecting machines, sensors, and actuators.

The global Human Machine Interface market is growing by leaps and bounds. According to forecasts, it will be worth $7.24 billion by 2025 (Compare: in 2019, it was valued at $3.71 billion).

Experts predict that the pharmaceutical industry, in particular, will see significant growth in automation, citing the current trend towards the use of high-precision contamination-free minimal human-interaction machines as a sign of things to come. In different countries, including the US, China, and India, the pharmaceutical sector is expected to witness a CAGT of around 150-200%, according to a recent market report. (Note: the base year is 2019 — before the COVID-19 outbreak).

Along with solutions for the pharmaceutical sector, HMI development is common across various industries, such as consumer electronics, robotics applications, transportation, and more. Advanced HMI examples can be found across many industries and solutions — wearables, payment terminals, security systems, cars and airline cockpits.

Key aspects of HMI development 

Each HMI solution comes not only with a custom set of features and functions with different levels of complexity, but also various production standards and design patterns, as well as behavioural and technical aspects. While a self-service kiosk needs a basic data visualisation app on a built-in screen, an HMI unit for electric vehicles requires a complex cloud-based system with networking capabilities.

Meanwhile, typical HMI ecosystems rely on three core aspects to function — hardware, software, and infrastructure. All three aspects need to be mastered in order to be competitive in the HMI market.  

(Image credit: Future)

Things to consider when developing a human machine interface device

1. Determine the functions your HMI requires. Core functional requirements will define how your solution will be equipped on both the hardware and software levels. This includes keypads for terminals and kiosks, switches and control panels for train or bus equipment, elevators and conveyors for warehouses.

While a small operator interface terminal needs a basic feature set and simple software connected to a web-server, a mid-sized solution requires several screen displays, extensive functionality, and a range of hardware options, such as USB ports and hard drives.

In order to launch the final product with all relevant functionality and without extra costs (both for development and BOM), it is crucial to define all solution requirements at the outset. The more detailed the upfront project specification is, the more you can expect to save time and costs down the road.

2. Consider specific input and output requirements. Specify your input and output possibilities; users will input data with touch panels, keypads, buttons, and/or switches and information will be output with displays and indicator lights. Although touchscreens are common and popular, switches are useful in transport equipment, electronic production, and tools for medical diagnostics — especially for users wearing gloves. Also, never forget about emergency buttons and switches!

3. Explore the mandatory regulatory standards. These can involve state, industry, safety, design, and other regulations. In particular, you may have to follow industry guidelines, such as guidelines for semiconductor manufacturing equipment, and additional ANSI, IEEE, or ISO specifications, like ISA Standard 101 for process automation systems. Complying with some of the regulations will require additional development effort. For instance, while developing an HMI for electric vehicles, the team at Softeq integrated a Safety RTOS to make vehicles compliant with the ISO 26262 automotive standard, thus enabling safety-critical data to display at all times.

4. Define the environmental circumstances. Requirements can change dramatically depending on the setting of the HMI. An HMI for a clean indoor space may vary greatly from one in a noisy, outdoor public space. And it doesn't end with physical location. Temperature extremes, regular wear and tear, and even vandalism might be factors to consider. 

5. Take into account the expected in-service life. In the ideal situation, all elements should be durable and last for the entire solution's lifespan. Replacing specific faulty or low quality components is not only inconvenient, but also costly.

6. Find the right tech partner. You will have to choose whether to work with a single company that can develop a complex solution under one roof or find several vendors with niche expertise for separate project areas. While choosing the most suitable option, take into account the skill set, process management aspects, and costs.

7. Select the best tech stack within your budget. Select the technology resources for firmware, embedded systems, or software you can afford from the very beginning. Weigh all pros and cons of each decision: for example, choosing low-quality displays may lead to lower user engagement; going for the cloud instead of a server-based solution may help you minimise budget with no losses in performance.

Selecting your tech stack is a good opportunity to help prioritise your project objectives. When choosing a display technology, for example, there can be a host of options on the market — CRT or LCD for monochrome displays and OLED, Quantum Dot, or LCD for colour displays. 

8. Opt for approaches that improve performance. At Softeq, we divide hardware components to speed up specific software functions. In particular, we embed accelerators, such as DSP, GPU, IPU, or other relevant processing units, in the system. This division results in an increased overall performance.

Imagine you want to empower your HMI with augmented reality functionality and the possibility to display 3D objects. In this case a GPU embedded in the solution will speed up 3D rendering significantly, as it processes data in hardware rather than software. 

Adding coprocessors that equip HMI solutions with AI/ML functionality is being adapted by companies across the globe that are looking to speed up their tech. Leading manufacturer Arm, which has embedded chips in the majority of phones and smart devices, introduced its latest Cortex-M processor (the M55) and the Arm Ethos-U55 micro neural processing unit (NPU) back in February of this year. According to TechCrunch, "the combination of both designs can speed up machine learning performance by up to 480 times."

9. Introduce clear panel layout. This includes building a consistent and easily navigated information hierarchy, highlighting important objects, and creating an uncluttered HMI design. In HMI development, simplicity rules: limited colour use, no animated or 3D elements, and few variations in font types and text sizes make interaction easy and predictable for users.

When Softeq was creating the interface for a packaging and material handling manufacturer, we avoided overwhelming users with too much data on one HMI screen. As operators had to control a number of parameters, such as load weight and shape, film width and thickness, and containment force, keeping the display simple was an easy way to lower their cognitive load and fatigue.

10. Put the user first. In cooperation with UI/UX designers, focus on the user’s demands, possibilities, and level of expertise. It helps to select relevant HMI components, panel layout, data presentation, and ways to provide feedback (visual, audible, tactile, or combined). Powerful human machine interface devices stand out for their usability. How intuitive the interaction between the user and the interface is, and how fast it is to learn, makes an enormous difference.

11. Choose the way to connect the HMI with core equipment. There are three common methods to accomplish this — hard-wired, serial buses, or wireless connections. While traditional hard-wired connections usually require miles of wires (it is common for the transportation sector), serial buses enable connecting through software (using CAN, Ethernet, and other protocols). The advantageous wireless approach gives the unit maximum mobility and the possibility to transmit data in real-time.

Your solution may be required to support multiple connectivity methods. For instance, you may need to incorporate Ethernet and FPDLink for the wired interface, Wi-Fi, LTE, Bluetooth, Z-Wave, or Zigbee for external connections for vehicle and smart home solutions.

12. Focus on HMI security. A number of tools help developers to establish cybersecurity. Here’s a simple example: Alexa, the fastest-growing voice assistant, communicates over an HTTP connection, which is secured using SSL/TLS protocols. Make sure the authentication process in your HMI is safe through strong password protection, limited remote access, and auto log-off. The crucial task for a software vendor is to provide a robust network configuration, such as only connecting the network to specific ports and controllers and blocking all other connections.

Take home message

Developing excellent HMIs is not an option, it's a must. The spectrum of consequences for poor-quality HMIs ranges between costly and deadly. While poorly conceived wearables might lead to a drop in sales for the startup that launched the product, faulty industrial HMIs can cause severe accidents with irreversible consequences.

But it's not all doom and gloom. Well-designed, efficient HMIs equipped with top-notch functionality and user experience can work wonders. Here are just a few potential positive outcomes:

  • Increased product quality
  • Reduced errors and downtime
  • Time savings in startup and shutdown
  • Financial savings on bug fixing and unexpected errors
  • Increased sales
  • Increased safety and avoided accidents

Tatsiana Tsiukhai, Copywriter, Softeq