Page 308 - Design for Six Sigma a Roadmap for Product Development

278 Chapter Eight

Theorem 18: (The Best Design for Large Systems)
The best design among the proposed designs for a large
system that satisfy m FRs and the Independence Axiom
can be chosen if the complete set of the subsets of {FR}
vector that the large system must satisfy over its life is a
known priori.
Theorem 19: (The Need for Better Design for Large Systems)
When the complete set of the subsets of FRs that a given
large flexible system must satisfy over its life is not a
known priori, there is no guarantee that a specific design
will always have the minimum information content for
all possible subsets and thus, there is no guarantee that
the same design is the best at all times.
Theorem 20: (Improving the Probability of Success)
The probability of choosing the best design for a large
flexible system increases as the known subsets of FRs
that the system must satisfy approach the complete set
that the system is likely to encounter during its life.
Theorem 21: (Infinite Adaptability versus Completeness)
The large flexible system with an infinite adaptability
(or flexibility) may not represent the best design when
the large system is used in a situation where the com-
plete set of the subsets of FRs that the system must sat-
isfy is a known priori.
Theorem 22: (Complexity of Large Systems)
A large system is not necessarily complex if it has a high
probability of satisfying the FRs specified for the system.
Theorem 23: (Quality of Design)
The quality of design of a large flexible system is deter-
mined by the quality of the database, the proper selection
of FRs, and the mapping process.

Appendix 8B: Historical Development
of Axiomatic Design
Axiomatic design can be defined as a system design method. The
process for system design is this: identify the functional requirements
or CTQs, determine the possible design parameters and process vari-
ables and then integrate into a system. In this case, being able to
understand the relationship among the different requirements and