\chapter {Needs and Goals}
\section{Problem Definition: Need Statement}
During the course of human development  different kinds of needs existed.  It is always have been and always
will be a need for improvement and making new designs.   Lincoln Steffenes wrote" The world is yours, nothing is
done, nothing is known.  The greatest poem isn't written, the best railroad isn't build yet, the perfect state
hasn't been thought of.  Everything remains to be done right, everything." \cite{buhl}.  The engineer is a
person who applies scientific knowledge to satisfy mankind's needs.  

The form in which the problem is often presented to an engineer constitutes one of the most serious
difficulties which he must overcome.  Even if some goals are given to the engineer, they are often not
specifically stated.  Problems may be presented as \emph{"the shaft is breaking"}, \emph{"the controls aren't
producing the desired effect"}, \emph{it costs too much to operate this engine." } It is then the first task of
the engineer to determine the real problems which exist and to determine the extent and confines of the goals. 

It is necessary to formulate a clear exact statement of the problem in  familiar words and symbols.  It is
necessary to isolate the problem from the general situation and to delineate its form.  This definition should
clearly identify every aspect of the problem on which attention should be concentrated.  The non essential
should be stripped away and the individual characteristics of the problem should be differentiated.  It should
be determined whether or not the immediate problem is part of the larger problem.  If it is, it should be
determined what relationship exists to the total part.  Lets consider the following example.  A designer  is
presented with a situation involving formation of ice on a television tower.  The ice would form during certain
types of weather, fall away from the tower and cause damage to vehicles and people below.  A general
formulation of this problem might be 
\emph{How to prevent ice from forming on a television tower?} By asking such questions as,\emph{ What would
happen if ice did form?} and \emph{What harm would such formation do?} It was determined that the first
definition was much too narrow.  A much boarder definition was, \emph{How to prevent ice which forms on a
television tower from doing harm or damage to people and equipment below the tower?}. 

Before an engineer can define the problem properly he must recognize all the problems that exist.  Most of the
failures in machines occur not because we make mistakes in analyzing the problem but because we fail to
recognize that there is a problem.  For example, the first year maintenance cost for a paint drying oven was
\$2000 (an oven whose original cost is \$1700).  The high cost was due to the frequent dismantling of oil in
bronze sleeve bearings mounted within the baking chamber.  Once the problem was recognized the solution was
relatively simple (mount the bearings outside the oven).  

\section{Objective Tree}
An important step in design is to clarify the design objectives.  This step is helpful in all design stages. The
objective ststement  
\begin{enumerate}
\item should be  easy to understand by the client and the designer
\item should be  agreed on by the client and the designer
\item controls and manages the design
\end{enumerate} 
The objective tree method offers a clear and useful format for the objective statement.  It shows in a
diagrammatic form the ways in which different objectives are related to each other.  The objective tree method
procedure was summarized by Cross \cite{cross} as
\begin{enumerate}
\item Prepare a list of design objectives: These are taken form of design brief, from questions  to the client
and from discussion from the design team
\item Order  the list into sets of higher level and lower level objectives.  The expanded list of objectives
and sub-objectives is grouped roughly into hierarchical levels.
\item Draw a diagrammatic tree of objectives, showing hierarchical relationships and interconnections.  The
branches in the tree represent relationships which suggest means of achieving objectives.
\end{enumerate}
\subsection{Worked Example}
After the residents of Gotham city complained to their mayor of the water quality, 
he ordered the health unit to investigate the
complaint. The health unit recomendation was based on the chemical analysis done by the 
top chemist at the Department of Public Health.
The task is now given to the City engineers to design water purifiers. 
Your task to help them out and build an Objective Tree.
\subsection*{Solution}
\begin{enumerate}
\item Prepare a list of design objectives
\begin{itemize}
\item Cost effective
\item Saftey
\item Can detect chemical imbalance
\item Fewer Repairs
\item Easy to repair when needed
\item Long lasting
\item Affordable
\item Low Damage
\item Low or no contamination
\item Takes up least possible space
\item Safe for human
\item Safe for environment
\item Gets the job done
\item Can correct problems in least time
\item Low maintainance
\item Cleans high volume of water 
\item ...(fill up the blank)
\item ...
\item ...
\end{itemize}
\item Order the list into sets

\begin{tabular}{ccc}
Safety&Cost Effective&Efficient\\ \hline
Safe for human&few repairs&can detect chemicals\\
safe for environment&Easy to repair&Long lasting\\
&affordable&low damage\\
&takes least possible space&get job done\\
&low maintainace&Correct problems in low time
\end{tabular}

\item Draw an objective tree
\begin{figure}
\vspace{7in}
\caption{Objective tree for water purifier}
\end{figure}
\end{enumerate}

\subsection{Example: Automatic coffee maker }
 Build an objective tree for automatic coffee maker 
\begin{enumerate}
\item  Prepare a list of design objectives
\begin{itemize}
\item Safety
\item Efficient
\item Quality
\item Convenient
\item Easy to use
\item Fast
\item Makes good coffee
\item Does'nt burn user
\item Good mixture
\item Right Temperature
\item Splash Proof
\item Cheap to consumer
\item Volume of coffee
\item Automatic
\item Timer
\item Energy saver
\item Temperature control
\item Easy to Clean
\item ...(fill up the blank)
\item ...
\item ...
\end{itemize}

\item Order the list into sets


\begin{tabular}{cccc}
Safety&Quality&Convenient&Economical\\ \hline
to user&Coffee tasts Good&easy to Clean&Affordable\\
Does'nt burn user&Right Temperature&Automatic&Volume of coffee\\
Splash Proof&Good mixture&Timer&Energy saver\\
&Temperature control&&Fast\\
\end{tabular}


\item Draw an objective tree 
\begin{figure}
\vspace{7in}
\caption{Objective tree automatic coffee maker}
\end{figure}
\end{enumerate}

\subsection{Example: Automatic aluminum can crusher}

We will use this example through the other chapters of this book.  The example was offered as a design project
for IME students during  the spring semester 1998. The project statement is given as: 

Design and build a device / machine that will crush aluminum cans. The device must be fully automatic. i.e. all the operator needs to do is load cans into
the device, the device should switch on automatically- crush the can
 automatically- eject crushed can automatically - switch off automatically ( unless
more cans are loaded). Furthermore students should adhere to the following:

\begin{itemize}
\item The device must have a continuous can feed mechanism.
\item Cans should be in good condition when supplied to the device 
(i.e. not dented, pressed, or slightly twisted) 
\item  The can must be crushed to one fifth of its original volume.
\item The maximum dimensions of the device is not to exceeed 1.5 x 1.5 x 1 feet.
\item Performance will be based on the number of cans crushed in one minute.
\item  Elementary school children (K up) must be able to operate the device safely. 
\item The device must be a stand alone unit. 
\item The total cost of the device should not exceed the given budget (\$200).
\end{itemize}

 Although the need
statment is relatively clear, the deisgn teams made several interviews with the client and ask questions 
and carfully listen
to the client's responses to clearly determine the goal of the intended device.  Once the interview is completed, the
engineering team met and constructed the following objective tree to claerly state the goals and define the directions of
the device deisgn.  The following set of figures presents the objective tree of the automatic can crusher. 

\begin{figure}[ht]
\vspace{1.5in}
\caption{Main heading}
\label{regtra}
\end{figure}

\begin{figure}[ht]
\vspace{6in}
\caption{Performance branch}
\end{figure}
\begin{figure}[ht]
\vspace{5in}
\caption{Safety branch}
\end{figure}
\begin{figure}[ht]
\vspace{3in}
\caption{Apperance branch}
\end{figure}
\begin{figure}[ht]
\vspace{2in}
\caption{Inexpensive branch}
\end{figure}
\newpage

\section{Problems}
\subsection{Team Activities}

\begin{enumerate}
\item In this activity each group as shown in the list below ask as many questions as
they can to clarify the given design statement

\begin{enumerate}
\item Groups 1 and 9: Design a coffee maker
\item Groups 2 and 10: Design a safe ladder
\item Groups 3 and 11: Design a safe chair
\item Groups 4 and 12: Design a safe lawn-mower
\item Group 5: Design a coffee maker
\item Group 6: Design a safe ladder
\item Group 7: Design a safe chair
\item Group 8: Design a safe lawn-mower
\end{enumerate}

\item Draw an objective tree for an automatic tea maker
\item Draw an objective tree for the following:

 If you drive in the state of Florida, you notice some traffic congestion due to the trees being trimmed on the state roads and the
     freeways. Assume that the Florida Department of Transportation is the client. Usually, branches 6 inches or less in diameter are
     trimmed. The allowable horizontal distance from the edge of the road to the branches is 6ft. The material removed from the trees must
     be collected and removed from the roadside. To reduce the cost of trimming, a maximum of only 2 workers can be assigned for each
     machine. The overall cost, which includes equipment, labor, etc. needs to be reduced by atleast 25\% from present cost. The state claims
     that the demand for your machines will follow the price reduction, i.e.,
      if you are able to reduce the cost by 40\%, the demand will
     increase by 40\%. Allowable working hours depend on the daylight 
     and weather conditions.  
     

\item Draw an objective tree for the following statement: We have a mountain size of wood chips that we want process to home use fire logs. We are located in Tallahassee, Florida. We can have a
continuous supply of wood chips through out the year. We should be able to produce 50 fire logs per minute. The share holders require us to
have a large profit margin and our prices should be lower than our competition for the same size logs. Needless to say the logs should preduce
enough heat to keep our customers faithful, and have environmentally clean exhaust.
\end{enumerate}

