04-10-2012, 01:23 PM
Human–Machine Interaction
hmi.docx (Size: 32.79 KB / Downloads: 33)
The user interface, in the industrial design field of human–machine interaction, is the space where interaction between humans and machines occurs. The goal of interaction between a human and a machine at the user interface is effective operation and control of the machine, and feedback from the machine which aids the operator in making operational decisions. Examples of this broad concept of user interfaces include the interactive aspects of computer operating systems, hand tools, heavy machinery operator controls, and process controls. The design considerations applicable when creating user interfaces are related to or involve such disciplines as ergonomics and psychology.
Introduction
To work with a system, users have to be able to control and assess the state of the system. For example, when driving an automobile, the driver uses the steering wheel to control the direction of the vehicle, and the accelerator pedal, brake pedal and gearstick to control the speed of the vehicle. The driver perceives the position of the vehicle by looking through the windshield and exact speed of the vehicle by reading the speedometer. The user interface of the automobile is on the whole composed of the instruments the driver can use to accomplish the tasks of driving and maintaining the automobile.
Terminology
There is a difference between a user interface and an operator interface or a human–machine interface.
• The term "user interface" is often used in the context of (personal) computer systems and electronic devices
o Where a network of equipment or computers are interlinked through an MES (Manufacturing Execution System)-or Host.
o An HMI is typically local to one machine or piece of equipment, and is the interface method between the human and the equipment/machine. An Operator interface is the interface method by which multiple equipment that are linked by a host control system is accessed or controlled.[clarification needed]
o The system may expose several user interfaces to serve different kinds of users. For example, a computerized library database might provide two user interfaces, one for library patrons (limited set of functions, optimized for ease of use) and the other for library personnel (wide set of functions, optimized for efficiency).[clarification needed]
Consistency
A property of a good user interface is consistency. Good user interface design is about getting a user to have a consistent set of expectations, and then meeting those expectations. Consistency can be bad if not used for a purpose and when it serves no benefit for the end user, though; like any other principle, consistency has its limits.[2]
Consistency is one quality to trade off in user interface design as described by the cognitive dimensions framework. In some cases, a violation of consistency principles can provide sufficiently clear advantages that a wise and careful user interface designer may choose to violate consistency to achieve some other important goal.[3]
There are three aspects identified as relevant to consistency.[4][dubious – discuss][not in citation given]
First, the controls for different features should be presented in a consistent manner so that users can find the controls easily.[citation needed] For example, users find it difficult to use software when some commands are available through menus, some through icons, some through right-clicks, some under a separate button at one corner of a screen, some grouped by function, some grouped by “common,” some grouped by “advanced.” A user looking for a command should have a consistent search strategy for finding it. The more search strategies a user has to use, the more frustrating the search will be. The more consistent the grouping, the easier the search. The principle of monotony of design in user interfaces states that ideally there should be only way to achieve a simple operation,[5] to facilitate habituation to the interface.
Second, there is the "principle of least astonishment".[citation needed] Various features should work in similar ways.[6] For example, some features in Adobe Acrobat are "select tool, then select text to which apply." Others are "select text, then apply action to selection."[7] Commands should work the same way in all contexts.