Human machine interfaces (HMI) are used extensively in commercial applications, including factories, businesses and workplaces. It lives up to its namesake by offering an interface through which a human operator controls a machine. While HMIs vary in terms of function, most are comprised of a few basic components. This includes membrane switches, rubber keypads and touchscreens.
While most people are familiar with the general concept behind HMIs, few know how they are designed. Of course, the design plays an important role in its function. If an HMI is properly designed for a specific function or task, it will perform that function or task with greater efficiency. On the other hand, however, HMIs that are poorly designed will suffer from lower accuracy, efficiency and other problems.
So, how exactly is an HMI designed? Again, it varies depending on the specific HMI. However, most are designed in three stages: interaction specification, interface software specification and prototyping.
For interaction specification, practices used for designing an HMI include user-centered design, persona, activity-oriented design and more.
For interface software specification, practices used for designing an HMI include use cases, constrain enforcement and more.
For prototyping, practices used for designing an HMI include basing the design on libraries of interface elements like controls and decoration.
It’s important to note that most of the larger and more complicated HMIs are computerized. For these HMIs, the term “human-computer interface” is used, as it describes the interface’s function more accurately. This term is also used to describe the software used to control the buttons and other physical elements of the interface.
On the engineering side of HMIs, ergonomics plays a key role in its design. The term ergonomics refers to the fitting of a workplace or device to meet the needs of the worker. When speaking about HMIs, this could be placing the buttons and controls in proper locations so they are more comfortable and natural to use. If the HMI has buttons placed in awkward locations, it may prevent the operator from being able to easily use it, in which case the HMI would suffer from poor ergonomics.
According to Wikipedia, some of the tools used to incorporate ergonomics factors into HMIs are designed based on computer science like computer graphics, operating systems, programming languages, etc. Expression graphical user interfaces are also used for HMI designs.
Hopefully, this will give you a better understanding of how HMIs are designed.