Human Machine Interface Design: A Complete Guide

You deal with the Human Machine Interface, or HMI, when you’re navigating through your car’s digital dashboard or monitoring the screen next to the patient’s bed in a hospital. HMI design is a link between decision-making (by humans) and the execution (by machines). Human Machine Interface transforms our commands into actions and converts the data into logical information.

Basically, HMI makes it possible for humans to function and control machines. These machines can range from healthcare devices, industrial machines, and can be touchscreen or physical button-led instruments with screens. HMI is also found in smart home appliances and as an aircraft’s voice-controlled cockpit system.

What’s unique in HMI design as compared to the typical UI UX design in mobile and app is: the situation and the impact of its use. A bad website UI UX design can irritate customers. However, a poor Human-Machine Interface design is time-sensitive and can directly impact a patient’s health readings, production losses, safety threats, and errors that are lethal.

Industries using HMI

HMI UI UX design is widely used in sectors, including;

Industrial Automation

In automated industries, HMI design is used in production assembly lines, supervisory control and data acquisition i.e., SCADA systems, programmable logic controller dashboards, etc.

Automotive

Infotainment systems, digital instrument clusters, and EV charging stations use Human-Machine Interface design for interaction and functioning.

Healthcare

Human-Machine UI/UX Design is widely used in surgical robotics, diagnostic machines, patient health monitoring, and patient care systems.

Aerospace and Defence

Mission control interfaces, navigation, cockpit display systems, and other time-critical mission-led defence machines are all developed with advanced HMI designs.

Consumer Electronics

Consumer electronic devices like home appliances, smart home dashboards, and other gadgets are all examples of high-tech HMI designs.

These are some of the many examples where HMI UI UX design is effectively used and directly impacts productivity, customer satisfaction, and even safety.

Human Factors in HMI Design

The main goal of Human machine interface design is to make machines easily operable by humans. For this, it is significant to understand human behaviour and the factors that lead to interaction with the machines and interfaces, and make decisions accordingly. Let us explore the human factors responsible for HMI design.

Physical Factors

HMI UI UX Designers need to understand the physical factors while developing machine-led interfaces. In factories or at the R&D institutions, assembly lines, most of the workers and scientists move with overalls, factory wear, gloves, and other wearables while dealing with the machines. In such cases, small and unintentional button or screen touches should be avoided at any cost. For this reason, the designers should consider the environment and the location where the machine will be placed and develop HMIs with big buttons, touchscreens compatible with gloves, physical dials, and large fonts.

Cognitive Factors

In time-sensitive environments, only the critical, urgent, and exact information should be displayed on the screens. For example, in medical emergencies, the monitor screen shouldn’t be consumed with excess information, as it can confuse the operator. It’s significant for the HMI designer to prioritize critical data as per the scenarios and also reveal secondary data with progressive disclosure if required.

Environmental Factors

Have you ever noticed that our car dashboards have a display setting for screen brightness? That helps drivers adjust the screen light and operate easily, both day and night. Or at a mining location, the Human machine interface needs to be high-contrast so the miners can operate even at low light. Additionally, the aviation UI may require both visual and auditory alert systems so the pilots do not miss any notifications. These environmental factors, including sound, vibration, temperature, and light, are all extremely significant human factors when building an HMI.

Accessibility Factors

Accessibility is a must in designing a human-machine interface. Colour coding, icons, patterns, buttons, and sounds ensure inclusion. These accessibility factors play a crucial role in designing a human-machine interface, making it efficient, safe, and easy to use.

HMI design needs may vary as per the above human-led factors and industry requirements; however, these best practices are followed religiously while developing an HMI design. Let’s get to know the best practices of HMI UI UX design.

Best Practices for HMI Design

Clarity

Only the information necessary and critical should be displayed on the HMI. For example, for a train operator, speed, distance, signal status, and tracking are the most primary and time-sensitive information needed on the display. Hence, clarity and simplicity are one of the core principles in HMI designing.

Consistency and Visual Hierarchy

In Human-Machine Interface, only limited, consistent, and urgency-based information is displayed in sequence and as needed. The designers need to organize the components, information, and elements in a way that allows the HMI operator to easily identify the data they need to view on the screen without confusion. Also, critical alerts and routine information should be displayed distinctly through colour coding and other features, thus maintaining the visual hierarchy.

Feedback, Error, Prevention, and Recovery

Every command, input, or action should trigger a prompt and clear response by the system. Hence, the user can rest assured that the input was noted correctly and permits them to react promptly. Errors should be signalled quickly, and prevention inputs should be given on time through guided workflows.

User-Centric Design Priority

When designing an interface, the user is the king. A designer should understand the user, their perceptions, and their mindset. The designer should ask questions like, where the user will operate the machine or device, does it involve quick decision-making, is it time-sensitive, or does it involve a complex process? For this, HMI designers should conduct field studies, workflow analysis, and interviews, and develop interfaces that reflect these realities.

Context of Use

A metal manufacturing environment differs from a car’s ambience. Hence, the interface design should consider the environment, whether it’s too crowded, noisy, or a quiet one, like a surgical room. This allows the designers to understand the context and design features like voice commands, accessible controls, buttons, and tactile functions, without needing to check the screen often.

Visual-Audio and Physical Communication

Human-Machine Interface, as the name suggests, is an interactive communication between humans and machines. Hence, the designers need to create such interfaces that make it easier for humans to interact with the devices effortlessly. This communication can be in multiple ways, including colour coding, icons, audio signals, typography, etc. For instance, red colour signifies stop or danger, while green colour indicates a ‘go-ahead’ signal for any functioning. The font size matters a lot when the operator needs to quickly read the screen data to respond to an action. These universal communicative elements play a very crucial role in a critical environment where decisions are to be made just by glancing, in less-than-ideal situations.

Interaction Design Optimization

How humans interact with machines or devices depends on the situation. For example, a dentist can operate the dental machinery through a foot pedal, giving ease of access for the dental tasks. In environments where the machines or kiosks need to be out, a touchscreen won’t work due to rain, heat, sunrays, and dust. Hence, physical buttons would be more convenient to operate. The HMI designers need to analyze these conditions and optimize the HMI accordingly.

Consistency Across Systems

Sometimes, organizations may require multiple interaction designs for their interfaces. Industries may face downtimes or technical errors. In such cases, the users must be able to switch between the systems and layouts with minimal friction. All physical, audio, and visual communication and feedback systems, standard control layouts based on the user’s operability needs to be accounted for while designing the human-machine interfaces.

These best practices help the UI UX design team to create interfaces that are scalable, adaptable, and operable.

TheFinch’ s Expertise

Our design experts make it easily possible to translate complex systems and prototypes into interfaces that make a difference for both businesses and users. Our HMI UI UX design team ensures the above-mentioned best practices are considered right from the design discovery. Our goal is simple: to make designs that are not just visually appealing but also deliver productivity, ease of access, and business success.

Our principles are based on the ‘human factor’ when designing ‘machines’. Whether it's medical equipment, an aerospace display system, or a fabrication workshop, we begin with well-researched data and a rapid prototype. We conduct hardcore tests to make sure the designs are capable in real-world scenarios. We combine industry knowledge and HMI design best practices that are tried, tested, and proven under varied circumstances.

At The Finch, we deliver high-performance HMI designs and systems that can be trusted by businesses and users, before, during, and after every operation.