When the Industrial Revolution took place in the 1800s the world changed drastically. Machines were invented to do the jobs of humans to make work easier, quicker and less expensive. However, machines are essentially useless unless they are programmed and operated properly. This is where the human touch is still valuable in today’s high tech world.
The term human-machine interface basically refers to the point at which people and technology meet. This human-technology interaction can be something as simple as a grip on a hand tool or as complex as the flight deck on a jumbo jet aircraft. A simple hand tool such as a screw driver can be used much more effectively if it has a good grip. The same screw driver with a magnetic head is extremely useful to fit screws in those hard-to-reach places without having to dismantle the whole machine. This is one example of human-machine interface (HMI), which covers all areas where humans and machines interact. Another common example of human-machine interface is when a waiter or waitress keeps track of their sales by touching the screen on a computerized billing system.
These days most humans interact more with computer-based technology than they do with things such as screwdrivers and hammers. The task of an HMI is to make the function of a technology self-evident. A well-designed tool such as a hammer fits a person’s hand and makes a physical task easy and a well-designed HMI must fit the user's mental map of the task he or she wishes to carry out.
The human-machine interface allows us to control a wide variety of machines and electronic equipment. It allows humans to give these devices instructions and to take corrective action. HMI covers the interface used to control mechanical and electrical machines, automobiles, etc. This includes your computer, CD player, alarm clock, washing machine, etc. The interface may consist of push buttons, levers, knobs, switches, handles, monitors, keyboards, computer mouse, joysticks, touch screen monitors, ATMs, DVD player controls, automobile dashboards, tractors and even space vehicles. Common user interfaces are: graphical, command line, and tactile.
To be of any use, an HMI should be productive, easy to learn and easy to use. The usability factor measures the amount of consideration given to the user's physiology and psychology while designing the interface. Ergonomics, which includes the operator seating arrangement, should also be considered to reduce operator fatigue. The ISO 9241 standard specifies three units for quality: effectiveness, efficiency and satisfaction.