Human
machine interface (HMI) devices are also called human interface machines
(HIM) or man machine interfaces (MMI). They essentially act as a junction
between the operators (human) and the electronic components (machine).
Now, this might conjure up images of
people wired to computers as in many sci-fi movies. This, however, is
not the case as HMIs are customised personal computers (PCs) capable
of performing specialised functions.
HMIs are generally associated with
the manufacturing industry and are required in order to cope with the
increasing level of automation at factories. Automation using HMIs is
one of the hottest fields of research and has a major influence on a
number of industry sectors. A key factor to be taken into account while
designing the interface system of a manufacturing plant is its overall
usability. It is extremely essential to build the operator’s confidence
in the machine. This can be done by empowering the HMI with features
such as ease-of-use, ease of programmability, easy understanding and
clear display of information. Although there still exists a segment
of designers who consider the HMI as a mere tool or prerequisite to
make things work, many new technologies with significant benefits are
all set to make HMI the centre of all monitoring and control operations.
What is an HMI?
HMI refers to the user interface in
a process control or manufacturing system. It provides a graphicsbased
visualisation of an industrial monitoring and control system and allows
the operator to monitor and control many, if not all, of a plant’s
functions.
Its design and functionality depend,
to a great extent, upon its intended application. Many HMIs are traditional
PCs running specialised software while others may resemble the cockpit
of an x-wing fighter from the Star Wars movies. In industries such as
food and beverages, bottling, and pharmaceuticals, there is a need to
use extremely hygienic and clean HMIs.
HMIs in the oil and gas industry are
designed to be rugged, with strong safe area protection (intrinsically
safe) as they operate in hazardous environments. Usability is one of
the most coveted attributes of an HMI and, as mentioned earlier, depends
upon the application. Usability is defined as the quality of use. According
to the ISO 9241 standard, three components of usability are defined
as applicable for the design of HMIs: efficiency, effectiveness and
satisfaction. Efficiency refers to the way in which the product’s
action matches the user’s requirement.
Efficiency has to do with the time
required for the users to understand and master the HMI. Also involved
is the error rate as well as the impact on the productivity/effort ratio.
Satisfaction is the user’s verdict concerning the HMI. One important
parameter is the stress factor. The HMI should be able to reduce stress
as well as enable the performance of a satisfying job for the users.
Usability engineering is the term given to the overall design process
that helps in achieving the maximum potential of the three usability
components.
What is an ‘interface’
and what are the different types?
An interface is the point of interaction between the computer and
the human. It refers to control sequences (mouse clicks, selections
with the touchscreen) that the user employs to control any programme,
and the auditory, graphical, and textual information that has been delivered
to the user. Some of the commonly used interfaces are graphical user
interface (GUI) and Web-based user interfaces.
Various types of interfaces are:
GUI interface
The input for a GUI is accepted through devices such as the computer
mouse and the keyboard, and the articulated graphical output is displayed
on the monitor. The two main principles used in the GUI design are application-oriented
interfaces and object-oriented interfaces. Web-based user interface
Web-based user interfaces accept
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