Humans in Work System Environment - Fundamentals and Assessment Tools for Occupational Ergonomics - page 83

manual better-
example:
It seems impossible
to teach a computer
to takecare of
children, or write
symphonies.

supervisory better -example: In manufacturing automation is
more economical than doing it by hand ( large-batch operation ).

manual better
-example:
It takes less time
to write a few
words by hand
than to type it in a
writing program
on a computer.

completion
time

direct manual
control

execution
time

supervisory
control

sum of
planning and
teaching time
and execution
time

planning and
teaching time

computer execution
speed compensates the
time for planning and
teaching overhead

measure of task complexity

the task is too complex
to be progr ammed

manual better supervisory better manual better

FIGURE 5.11 Range in which supervisory control outperforms manual control (in modification of Sheridan, T.B.,
Humans and Automation — System Design and Research Issues, John Wiley & Sons, Santa Monica, 2002. With
Permission).

system approach (Section 5.2.2) are to be considered with the task design. Moreover, regarding the
implementation of group work, important organizational design fundamentals are described in

Section 5.5.6.

5.4.1.4 Ergonomic Design
In the fourth stage of the ergonomic design the “division of labor between segments of the organism” is
designed. On the basis of anthropometric and physiological and also information- and cognition-
psychological realizations, activity elements and working equipment are improved for the functions of
energy and power generation and the functions of the information absorption, processing, and delivery.
The model of user-computer interface, which is described in the following exemplifies the stage of
ergonomic design. This model is based on the language model, which derives from Foley and van
Dam (1982). The model supports the process of designing the user-computer interface and consists
of four steps (Figure 5.12).

1. In the first step (conceptual design), the user has to clarify how a task can be carried out with the
help of a computer. At this level the structure of the fulfilment of a task is partially determined by
the analysis of the task.
2. In a second step, the software functions are defined. The functions influence the activities of the
working person (semantic design).
3. In the next level, the user has to find a way to solve the function. Therefore, the syntactic design
defines the sequence of input and output. “For input, sequence is grammar — the rules by which
sequences of tokens (words) in the language are formed into proper

sentences.” These input
sentences are, for example, commands, names, coordinates, etc. The output tokens are often
symbols and drawings.

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