How to design an HMI system?

Melrose HMI System

In our previous blog post, What is HMI? An Extensive Guide About Human-Machine Interface, we gave you a walkthrough across the spectrum of Human Machine Interface. 

But how do you actually design an HMI system? What are the critical steps to make sure that your HMI matches the requirements of your application? 

By developing a proper interface between the machine and its human operator, you can greatly impact its efficiency and ease of use. The idea is to deliver a product that harnesses the connection between the two. This is what the human-machine interface field is all about. 

Sophisticated HMI systems allow reliable operation of technology in every single application, ranging from high-speed trains and medical equipment to semiconductor production equipment. HMI is about all the elements person will hear, see, touch, or use to control functions and receive feedback. 

In this article, we guide you through the fundamentals of HMI system design. You will see the key steps manufacturers should take to deliver a consistent, cost-effective, safe, and intuitive performance of your application. 

1. Define the functional requirements of your application

This point is all about identifying the tools required for effective operator control of the equipment, as well as matching the requirements of your application. Once you do finish, you’ll be able to determine which interface functions your application needs. 

Focus on general functionality first

How are the functions reflected in the interface control? Simple functions might be easily served by a rotary switch or push button, but more complex ones might require several screen displays to cover all the options. If that’s the case, what kind of auditory, visual, and tactile feedback will be most useful to the operator in performing the function? 

Next, consider how complex the input will be

The input can be as simple as an on and off switch. But things might get a little more challenging if you’re looking at a touchscreen display. 

Touchscreen and HMI systems are becoming more and more popular across various applications, from public transportation to information kiosks. They allow simplifying complex operations and tolerate consistent use. 

By defining your input requirements, you’ll be able to decide which control technology will work best for your application. 

Don’t forget about operator feedback

Feedback can be auditory, visual, tactile, or a combination of these. It all depends on your application. Feedback is crucial in HMI systems that have no mechanical travel – for example, ones equipped with a touchscreen or capacitive device that has no moving parts when triggered. 

Interface with other systems

Will you need an interface or interconnection with other systems? It’s essential for HMI systems to interface or interconnect with the system under control but also probably some related systems. Identify this need before setting down to designing your system. 

Count in the application environment 

The application’s environment will determine the required durability of your HMI system. Any stresses such as exposure to moisture, vandalism, temperature extremes, or other characteristics of harsh environments (like an industrial production floor) are relevant here. 

Consider regulatory or standard considerations

It’s essential that your HMI manufacturer has comprehensive knowledge of the technical design, economics, and manufacturing standards required for your application. 

2. Understand the operator

To design a successful HMI system, you need to have a firm understanding of your device’s operators. Are they passive or intuitive users? Your commands or functions might have to be simple and presented on a user-friendly interface. And if you’re looking to serve an expert user, you might have to introduce multiple layers or levels for interacting with the environment. 

Here are all the important ergonomic considerations you should be making at this point. 

Panel layout

Make sure that your panel layout is designed to provide the operator with functional groups of related information in a consistent manner. Moreover, your system needs to require the operator to initiate some action and keep them informed by providing timely feedback about their actions. 

Selecting the right components

HMI designers need to carefully analyze the application’s requirements and consider the following elements: actuation preferences, physical configuration and mounting needs, electrical ratings, special requirements (like marking, environmental sealing, illumination). 

Pick the right colors

Colors play a crucial role in HMI design because they make your application much more user-friendly. Make sure to avoid using too many colors in your interface or flashing alarms. Use red for stop, failure, or fault, yellow for warning, and green for okay/start. 

Deliver feedback to users

Make sure that your system presents the results of action like pressing a button or entering a command in an absolutely clear way. The feedback can be visual, auditory, tactile, or a combination of multiple of these techniques. 

Cursor control

Consider how much control the operator needs. A joystick or trackball enables granular, pixel by pixel control which is much more precise than the typical point-and-click controller we find in PCs. 

Add a switching technology

If your application is designed for an environment with public access and specific conditions, you might need special switches. Take a soda dispensing machine in a public location. The sugared liquid might get into crevices and affect the machinery, so you need a completely sealed surface. Your switching technology needs to accommodate this need. 

Display technologies

In HMI applications, displays provide users with the information that operators interact to obtain. The choice of display technology will be dictated by the environment of the HMI system, including its core requirements, degree of ambient illumination, and exposure to environmental risks. While active-matrix LCD screens are used for their color functionality, organic light-emitting diodes (OLED) displays are an interesting option too. 

Touchscreen technologies

Many applications use touchscreen technologies that provide a wide range of functionalities and characteristics for HMI systems today. Determine which touch technology you need in the early stages of the design cycle. Each option comes with its unique electrical and mechanical requirements. 

Motion control

Applications that require macro-control usually go well with the joystick technology – for example, controlling a robotic arm or piece of material-handling equipment. 

Hard-wired connections

Hard-wired systems are still used in industrial legacy systems and transportation industries. They require no special tools from you and are usually visible and easy to understand – especially if the HMI interface controls only one machine. However, expect many disadvantages here – for instance, difficulty in integrating changes or adding new features. 

Wireless connections

Industrial applications usually employ wireless technology to benefit from real-time data transmission, remote management capabilities, and application mobility. However, security, reliability, and interference are significant challenges for wireless connections applied to HMI systems. 

3. Consider user safety requirements

When designing HMI systems, you need to make safety a critical concern of the system. Most accidents in high-risk environments result from human error. The best way to mitigate this risk is by presenting alarms and enabling users to report errors. 

Moreover, your system needs to include emergency stop switches to ensure the safety of operators and machinery. That way, you can be certain that it provides a consistent failsafe control response. 

Electrical machinery might require switch control for emergency shutdown to meet workplace safety regulations and other regulatory requirements (both international and domestic). 

Get high-quality HMI components from our systems

At Melrose Systems, we equip our clients with HMI systems of the highest quality. Years of experience and extensive know-how of our specialists help us to meet the demands of every application.

Get in touch with us if you’re looking for a team of experts to help you design an HMI system for you.

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