| @@ -3,7 +3,7 @@ | |||
| \label{chap:analysis} | |||
| \begin{marginfigure} | |||
| \centering | |||
| \includegraphics[width=6cm]{graphics/design_flow_analysis.pdf} | |||
| \includegraphics[width=6cm]{graphics/design_flow.pdf} | |||
| \caption{Overview of the design flow, split in two phases: Preliminary Design and the \ac{ridm}.} | |||
| \label{fig:design_flow_analysis} | |||
| \end{marginfigure} | |||
| @@ -11,58 +11,53 @@ The previous chapter introduced how two design methods are combined to form the | |||
| In this chapter, a design plan is created from this combined design method. | |||
| The goal is to have a concrete design plan that can be used in the case study. | |||
| All of the steps in the design plan must be specific such that each of these steps can be evaluated after the case study is finished. | |||
| The design plan is split in a preliminary design and a \ridm part as shown in \autoref{fig:design_flow_analysis}. | |||
| The first three steps of the design phase are based on the \ac{se} approach and are already described with great extend by \textcite{blanchard_systems_2014}. | |||
| As the evaluation of \ac{se} is not in the scope of this thesis, this chapter only covers the minimal description of the design steps in \ac{se}. | |||
| The steps that are introduced by \ridm are covered in more detail. | |||
| \section{Systems Engineering} | |||
| The goal of the preliminary design is to setup system requirements and an initial design according to the problem definition. | |||
| Although these design steps in \ac{se} play a crucial roll in the success of the development, they are, however, very exhaustive. | |||
| A major part of this complete design process is the required documentation to ensure agreement about the design between the different stakeholders. | |||
| Resulting in a process that can take months or even years, which is not feasible for this thesis. | |||
| In this thesis, this design plan is only used for evaluation and will have only one stakeholder, the author. | |||
| This allows for a simple implementation of the \ac{se} approach, as it not possible to create a false start due to misunderstanding, saving valuable time. | |||
| For each of these \ac{se} steps is explained what is involved with a full implementation, and what part of the step is used in the design plan. | |||
| \subsection{Problem Definition} | |||
| Before any design process can start, the "problem" has to be defined. | |||
| In other words, why is the function of the system needed? | |||
| This is described in a \emph{statement of the problem}. | |||
| In this statement of the problem it is important to describe "what" has to be solved, not directly "how". | |||
| \textcite{blanchard_systems_2014} also note that "defining the problem is often the most difficult part of the process". | |||
| It is important to ensure good communication and understanding between the different stakeholders. | |||
| Otherwise, it is possible that the designed product is not up to the customers expectations. | |||
| It furthermore involves defining the subjects like what are the primary and secondary functions? When must this be accomplished? What is not a function? | |||
| For this thesis, however, the problem definition is limited to a short statement of the problem, covering some required functions with corresponding requirements. | |||
| \subsection{System Requirements} | |||
| The system requirements are derived from the problem definition, and describe the characteristics of the system. | |||
| As these characteristics form the foundation of the system, the requirements must be defined without any ambiguity, vagueness or complexity. | |||
| The requirements will be written according to the \ac{ears} \autocite{mavin_easy_2009}. | |||
| \ac{ears} was chosen for this design method due to its simplicity, which fits the scope of this thesis. | |||
| Later in the design, these requirements are divided over the subsystems. | |||
| Any issues, like ambiguity, in the requirements, propagate through these subsystems. | |||
| This might lead to a redesign of multiple sub-systems when these requirements have to be updated. | |||
| \subsection{Initial Design} | |||
| In the initial design step, the "what has to be solved", is expanded with a solution on "how it is solved". | |||
| To find the best solution it is important to explore the different solutions and design space. | |||
| Often, there are many possible alternatives but they must be narrowed down to the solutions that fit within the schedule and available resources. | |||
| This step results in one initial design that can be used in the next phase of the design. | |||
| \section{Preliminary Design} | |||
| The goal of the preliminary design is to setup a list of features that can be implemented in the \ridm phase. | |||
| To get to this list, there are four different steps to be completed. | |||
| Although these steps play a crucial roll in the success of the development, they are, however, also the most difficult steps of a design process \autocite{blanchard_systems_2014}. | |||
| An exhaustive design process would takes months or even years, and is just not feasible for this thesis. | |||
| \subsection{Problem Definition} | |||
| The first step of the design cycle is to describe the problem that has to be solved. | |||
| A clear and concise problem definition increases a successful design process. | |||
| It gives a better basis for the system requirements. | |||
| Therefore, lowering the number of reviews required for the system requirements. | |||
| Furthermore, good definitions help determine the overall feasibility of the project in an early stage. | |||
| \subsection{System Requirements} | |||
| The system requirements are derived from the problem definition. | |||
| As the features will be derived from these system requirements, the goal is to define the requirements without any ambiguity, vagueness or complexity. | |||
| The requirements will be written according to \ac{ears} \autocite{mavin_easy_2009}. | |||
| \ac{ears} was chosen for this design method due to its simplicity, which is is deemed suitable for the scope of this research. | |||
| If issues, like ambiguity, are not dealt with correctly, these issues can propagate into the sub-requirements that will be defined for each feature. | |||
| Solving these issues in a later stage of the design could require a redesign of features that were already completed. | |||
| \subsection{Initial Design} | |||
| At the start of a development the final solution for the problem is unknown. | |||
| It is important to explore the different solutions and design space. | |||
| The goal of this initial design is to create an overview of these possibilities. | |||
| Due to the scope of this research, the choice of design solutions is made for a design that is expected to fit this research, instead of determining the optimal solution. | |||
| However, in an actual design case, this step is crucial and can even be extended. | |||
| A problem can be solved with more than one design. | |||
| It is expected that these design solutions contain identical features. | |||
| For example, take a cube that has to be moved. | |||
| Each design has a grab feature that picks up the cube. | |||
| Instead of choosing a specific initial design, we could start by implementing the grab-feature. | |||
| If the grab feature proofs to be infeasible, we know that we have to choose a different design. | |||
| Would the grabber be a success, then the feature is already implemented for the designs that use it. | |||
| This can reduce the risk during the design by implementing features first that have overlap in other design solutions. | |||
| First of all, it can help select a suitable design solution. | |||
| If a initial design fails in a later stage, switching to a different design can be cheaper as some features are transferable. | |||
| \section{Rapid Iterative Design Method} | |||
| \subsection{Feature Definition} | |||
| \section{Rapid Iterative Design Method} | |||
| \subsection{Feature Selection} | |||
| \subsection{Rapid Development Cycle} | |||
| \subsection{Variable Approach} | |||
| \subsection{Feature Selection} | |||