连杆机构英文文献和中文翻译(4)

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Performance Specifications'

When the background is understood, and the goal clearly stated, you are ready to formu- late a set of performance specifications. These should not be design specifications. The difference is that performance specifications define what the system must do, while de- sign specifications define how it must do it. At this stage of the design process it is un- wise to attempt to specify how the goal is to be accomplished. That is left for the ide- ation phase. The purpose of the performance specifications is to carefully define and

constrain the problem so that it both can be solved and can be shown to have been solved after the fact. A sample set of performance specifications for our "grass shortener" is shown in Table 1-2.

Note that these specifications constrain the design without overly restricting the engineer's design freedom. It would be inappropriate to require a gasoline engine for specification 1, since other possibilities exist which will provide the desired mobility. Likewise, to demand stainless steel for all components in specification 2 would be un- wise, since corrosion resistance can be obtained by other, less-expensive means. In short, the performance specifications serve to define the problem in as complete and as gener- al a manner as possible, and they serve as a contractual definition of what is to be ac- complished. The finished design can be tested for compliance with the specifications.

Ideation and Invention

This step is full of both fun and frustration. This phase is potentially the most satisfying . to most designers, but it is also the most difficult. A great deal of research has been done to explore the phenomenon of "creativity." It is, most agree, a common human trait. It is certainly exhibited to a very high degree by all young children. The rate and degree of development that occurs in the human from birth through the first few years of life cer- tainly requires some innate creativity. Some have claimed that our methods of Western education tend to stifle children's natural creativity by encouraging conformity and re- stricting inpiduality. From "coloring within the lines" in kindergarten to imitating the textbook's writing patterns in later grades, inpiduality is suppressed in favor of a so- cializing conformity. This is perhaps necessary to avoid anarchy but probably does have the effect of reducing the inpidual's ability to think creatively. Some claim that cre- ativity can be taught, some that it is only inherited. No hard evidence exists for either theory. It is probably true that one's lost or suppressed creativity can be rekindled. Oth- er studies suggest that most everyone underutilizes his or her potential creative abilities.