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Technical requirements can be divided into four groups.
The first group. Requirements that contain geometric and constructive
cons-
traints
. Example of wording: the maximum deviation of the axle distance is
±0.5 mm.
The second group.
Requirements expressed through
technical or physical
concepts, written in the form of numbers with dimensions. Example of wording:
the resistance force at the output link is not more than 100 N.
The third group. Requirements expressed verbally, which do not include
either concepts
defined quantitatively, or geometric constraints in the design.
Example of wording: the device must be quick-detachable.
The fourth group. Requirements formulated with complex concepts or ma-
thematical dependencies.
The first group of requirements is significantly replenished as a result of
the discovery of restrictions related to the location of the designed mechatronic
module.
The second group of requirements is largely the result of a quantitative
mapping of the interrelationships of the mechatronic module with the external
environment and the features of the schematic diagram.The constructive reali-
zation of the requirements, expressed with the help of clear technical concepts
defined quantitatively (such as, for example, as a gear ratio), can be implemented
in various ways. The advantages of this form of writing requirements are very
large, as it does not carry uncertainty and serves
as a means of an objective
verification of the correctness of the design. All that has been said about the
second group of requirements can be attributed to the fourth group.
We should especially mention the third group of requirements. The verbal
form of writing technical requirements in most cases indicates the incomple-
teness of the process of formalizing the real physical picture. Sometimes it
is generated by the lack of information about the quantitative
side of certain
relationships or the lack of knowledge of the essence of any processes in the
mechatronic module-environment mechatronic system. Often the verbal formu-
lation by means of very general concepts unites a set of undisclosed relations.
An example of this formulation: «The mechatronic module should be easy to
use, when installing and dismantling.»
The designer, specifying and supplementing
the terms of reference for
himself, should decipher this point by considering the most significant inter-
relations between the mechatronic module and the servicing personnel. But
this does not mean that one should strive for the most complete formalization
of all technical requirements without exception. The degree of necessary
formalization is determined,
on the one hand, by the difficulties of its imple-
mentation, on the other hand by the requirements of the subsequent stages of
construction.
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The process of implementing requirements in
the design is accompanied
by back interactions for technical requirements. To implement a rational per-
centage of «requirements implementation,» the designer should be able to vary
within the permissible limits the parameters of the technical requirements. It is
therefore important in the requirements to reflect not only the nominal, but also
the limiting values of the values to be pledged.
Requirements for the mechatronic module can not be formulated if the
general direction of the design is not chosen.
The question of what to do is inseparable when designing from the question
of how to do it. The completed list of technical requirements always reflects the
degree of clarity of the designer’s views on the chosen direction of work.
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