\chapter{Concepts Evaluation}
In the previous chapter, we developed a technique for generating different concepts
that satisfy the need statement.  As it was demonstrated, the number of 
possibilities that may satisfy the need is a function of the number of entries
(different ways) that fulfill a function.  The larger the number of entries the
larger the number of concepts.  Obviously, not all combinations through the
morphological chart will lead to a feasible product.  The goal of this chapter
is to provide a methodology for evaluating the different devices. By the end of
the evaluation process, a product which has the highest potential for becoming
the quality product will be identified with the
availability of the many concepts that were generated by the 
morphological chart.  
The difficulty in concept evaluation resides in that the
designing team must choose a concept to spend time developing while they
still have limited knowledge and data on which to base their selection.
  Concepts at this point are still abstract, have little details and cannot be
  measured.  The essential question then becomes, should time be spent refining and adding minute details to
  all concepts and then measuring their outputs? Or would developing a mechanism to point out one
  concept that will most likely become the quality product, prove to be a more efficient option?  
  
  The screening of concepts can be accomplished by using different levels, which are:
  \begin{enumerate}
  \item 
  The concepts are directly measured with respect to a fixed 
  set of limits (specifications).  If a concept doesn't satisfy the
  specification requirement it will be dropped.
  \item  The design team uses their experience (Engineering gut feeling)
   to eliminate some concepts because the technology is not yet available
  to facilitate the concept. Or, by their judgement, the product is not
  feasible.   
  \item  The concepts are evaluated with respect to each other using measures
  defined by the criteria (specifications/wishes).
  This screening method was developed by Stuart Pugh in the 1980's, and is often
  called Pugh concept selection.  The purposes of this stage are to narrow the
  number of concepts quickly. 
  \end{enumerate}
  
  \section{Decision Matrix}
 The decision matrix method, or Pugh method, is based on comparing alternatives
 with the wishes list in the specification table.  An alternative should meet
 the customer demands, otherwise it will be dropped in the initial screening.
 Also, the concept should seem feasible to the engineering group, or it will be
 dropped by the second stage of screening.  The concepts that pass the initial
 two stages need to be evaluated with respect to each other, using a fixed
 criteria (specification table).  The Pugh evaluation 
 method tests the completeness and understanding of requirements, rapidly
 identifies the strongest alternative and helps foster new alternatives.  This
 method is most effective if each member of the design team performs it
 independently, and the individual results are then compared.  The results of the
 comparison lead to a repetition of the technique, with the iteration continued
 until the team is satisfied with the results.  The Pugh evaluation 
 method is performed using the following steps:
 \begin{enumerate}
 \item {\bf Choose the Comparison Criteria}.  If all alternatives fulfill the
 demands on the same level, then the criteria should be the wishes in the
 specification table.  Remember, the wishes were organized in an ordered fashion
 before they were used in the house of quality.  The order is based on the level
 of importance according to the design team.  A weighting factor between 0 and
 10 is assigned by the design team for each wish.  The basis for the weighting
 factor depends on the engineering team's feeling of how important the attribute may be to the
 final product.
 If the alternatives contain differences in the levels at which demands may be
 fulfilled, then the demands can be entered in the comparison criteria.
 \item {\bf Select the Alternatives to be Compared}
 From the morphological chart, different alternatives will be generated, some of
 these alternatives will be dropped because they do not satisfy the customer
 demands or they are not feasible.  The rest of the alternatives are possible
 candidates.  However, by using the initial screening stages, few alternatives
 will be left for the final stage.
 
 \item {\bf Generate Scores}.  After careful consideration, the design team
 chooses a concept to become the benchmark or
 datum against which all other concepts are rated.  The reference is generally
 either an industry standard or an obvious solution to the problem.  It can be a
 commercially available product, an earlier generation of the product, or any one
 of the concepts under consideration. It may also be a combination of subsystems, which have been combined to
 represent the best features of different products.
 
 For each comparison, the concept being evaluated is judged to be either better
 than, about the same as or worse than the datum.  If it is better than the
 datum the concept is given a [+] score.  If it is judged to be about the same as
 the datum, the concept is given [0]. If the concept does not meet the criterion
 as well as the datum does, it is given a [-].
 \item {\bf Compute the Total Score} After a concept is compared with the datum
 for each criterion, four scores are generated: the number of plus scores, the
 number of minus scores, the overall total and the weighted total.  The overall
 total is the difference between the number of plus scores and the number of
 minus scores.  The weighted total is the sum of each score multiplied by the
 importance weighing.  
 The scores can be interpreted in a number of ways:
 \begin{itemize}
 \item If a concept or a group of similar concepts has a good overall total
 score, or a high + total score, it is important to notice what strength they
 exhibit. In other words, notice which criteria they meet better than the datum.  Likewise, the
 grouping of - scores will show which requirements are difficult to meet.
 \item If most concepts get the same score on a certain criterion, examine that
 criterion closely.  It may be necessary to develop  more knowledge in the area
 of the criterion to generate better concepts.  Or, it may be that the criterion
 is ambiguous, or it may be interpreted differently by different members of the team.
 \item To learn even more, redo the comparison, with the highest scoring
 concept used as the new datum.  This iteration should be redone until the
 clearly "best" concept or concepts emerge.
 \end{itemize}
 
 After each team member has completed this procedure, the entire team should
 compare their individual results.  Then a team evaluation needs to be conducted.
 \end{enumerate}
 \section{Example}
 In designing a Splashgard for a mountain bicycle, the design team generated the
 following function diagram.
 
 
 \begin{figure}
 \vspace{4in}
 \caption{Function diagram for Splashgard}
 \end{figure}
 
 The preliminary list of customer requirements for the Splashgard are shown in the 
following table.
 
 
 \def \epsfsize#1#2{0.7#1}
 \begin{figure}
 \epsffile{../figures/8-2.eps}
 \caption{ Preliminary List of Customer Requirements for Splashgard}
 \end{figure}
 
 
 The morphological chart is shown in the following diagram.
 
 \def \epsfsize#1#2{0.7#1}
 \begin{figure}
 \epsffile{../figures/8-3.eps}
 \caption{Morphological Chart for the Splashgard}
 \end{figure}
 
 From the morphological chart the following concepts were generated.

\def \epsfsize#1#2{0.05#1}
 \begin{figure}
 \epsffile{../figures/8-1-b.eps}
 \caption{Concepts Sketch}
 \end{figure}
 
 The decision matrix is evaluated with respect to concept VII as the datum.
 
 \def \epsfsize#1#2{0.7#1}
 \begin{figure}
 \epsffile{../figures/8-5.eps}
 \caption{Initial decision matrix for Splashgard water deflection subsystem}
 \end{figure}

\section{Example: Automatic can crusher}
From the morphological chart many possible combinations of devices can be obtained, but not all
of these processes are positive or able to be effectively accomplished.  In this stage, the design
team begins to limit the possible designs based on specifications, manufacturability, cost and
other factors.  The surviving designs are then evaluated against each other. The concepts are shown
in the follwoing sequence of figures.  A decision
matrix is constructed to evaluate the designs based upon the wishes obtained from the
specification table.  Specifications are weighted by importance, with one being the lowest
and ten being highest importance.  The concepts are evaluated and one design is chosen by the
design team to be the best possible design. This design is considered the datum by which all
of the other designs are compared. Then, all of the other designs are evaluated against the
datum by a "+" if they exceed the datum in a wish, a "-" if they are below the datum in the wish and
"0" if they are equal to the datum in the wish.  The results are tallied and scores are evaluated,
then the best design is placed as the datum, and the evaluation is done again.  The
highest scoring design is the chosen design to be built.

\def \epsfsize#1#2{0.1#1}
\begin{figure}
\epsffile{../figures/concept-i.eps}
\caption{Concept I}
\end{figure}

\def \epsfsize#1#2{0.1#1}
\begin{figure}
\epsffile{../figures/concept-ii.eps}
\caption{Concept II }
\end{figure}

\def \epsfsize#1#2{0.1#1}
\begin{figure}
\epsffile{../figures/concept-iii.eps}
\caption{Concept III }
\end{figure}


\def \epsfsize#1#2{0.1#1}
\begin{figure}
\epsffile{../figures/concept-iv.eps}
\caption{Concept IV }
\end{figure}


\def \epsfsize#1#2{0.1#1}
\begin{figure}
\epsffile{../figures/concept-v.eps}
\caption{Concept V }
\end{figure}


\def \epsfsize#1#2{0.7#1}
\begin{figure}
\epsffile{../figures/8-6.eps}
\caption{Evaluation of designs: V is datum}
\end{figure}

\def \epsfsize#1#2{0.7#1}
\begin{figure}
\epsffile{../figures/8-7.eps}
\caption{Evaluation of designs:IV is datum}
\end{figure}
