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tags/0.4.1-experiment
Wouter Horlings 5 lat temu
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      content/case_experiment_feature_definition.tex
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      content/case_experiment_initial_design.tex

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content/case_experiment_feature_definition.tex Wyświetl plik

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%&tex
\subsection{Feature Definition}
\label{sec:case_featuredefinition}
At this point there are specifications and an initial design for the system.
In the following steps of the design method features will be implemented one by one.
The goal of this step is then to define these features.
During this step it became clear that this approach was not feasible.
Prior to this step the expectation was that this step would produce three features that could be implemented.
These three features were the SCARA, the cable suspended carriage, and the end-effector.
However, independent of the interpretation of this step, the result was not the three expected features.
\subsection{Feature Definition}
\label{sec:case_featuredefinition}
At this point there are specifications and an initial design for the system.
In the following steps of the design method features will be implemented one by one.
The goal of this step is to define those features.
However, the predefined approach was not able to produces a set of features that could be implemented.
This forced me to create a new approach for this step, introducing components into the design.
This section will first address why the current approach is not suitable, followed by the alternative approach.

Why were those three features expected in the first place?
During the previous steps a useful evaluation was to anticipate for the subsequent steps.
Where one of the following steps is to implement an individual feature.
Therefore, it must be possible to implement the feature.
Separating the initial design into the smallest components that could still be implemented, resulted in the SCARA, carriage and end-effector.
\subsubsection{Struggles with Features}
For their case study, \textcite{broenink_rapid_2019} design a control system for a mini-segway.
This mini-segway is an already existing \ac{cps} that is used during the lab-sessions of a control course, and any control-law can be uploaded directly to the system.
The specified features of that system are defined as:
\begin{enumerate}
\item Balancing the mini-segway upright
\item Steering the mini-segway
\item Driving forward and backward
\end{enumerate}
Although this is not explicitly explained, these features have dependencies: the steering and the driving both rely on a balanced segway.

The problem is that these three components do not describe the complete system.
Some functions of the system (feature) is performed by a combination of the components.
Therefore can the components in the system not be seen as features of the system.
Defining the components as features of the system is not a solution.
The relations between the components and features is still required.
A set of features for the Whiteboard writer would be:
\begin{enumerate}
\item Write character on position
\item Move carriage to position
\item Write text
\end{enumerate}
In this case, features 1 and 2 are required for feature 3.
However, in contrast with the mini-segway, the whiteboard writer does not exist yet.
Instead of creating a model based on the system, the system has to be designed first.
For these three features, the required hardware can be designed together with the feature.
The first feature would then also contain the design of the SCARA and the second feature the cable bot design.
Adding the features needed to meet the specifications for wiping the whiteboard, then such a feature would also need to design the SCARA.
In other words, more than one feature uses the SCARA in their behavior.
Resulting in the question: which feature should implement the hardware?

%As the features describe the behavior of the components, it is not a solution to replace the features with components.
\subsubsection{Separating Functions and Components}
It was decided not to add the SCARA and the cable bot as features, for the reason that they do not define behavior.
Instead, the features define how the hardware behaves.
A solution to organize the relations between features and components was found in RobMoSys\footnote{\url{https://robmosys.eu/approach/}}.
RobMoSys defines a separation of levels in a design.
Where the levels start functional and moves via software to hardware implementation.
Although not all levels of RobMoSys are used, it was very useful to define the features of the system.
The definition is shown in \autoref{fig:robmosys}.
The current definition of features allows to start the implementation with a component.
When the component is finished features can be implemented by following the tree upwards.
\begin{figure*}
\centering
\includegraphics[width=0.85\linewidth]{graphics/robmosys}
\caption{Feature Definition based on the separation of levels introduced by RobMoSys}
\label{fig:robmosys}
\end{figure*}

A solution to organize the relations between features and components was found in RobMoSys\footnote{\url{https://robmosys.eu/approach/}}.
RobMoSys defines a separation of levels in a design.
Where the levels start functional and moves via software to hardware implementation.
Although not all levels of RobMoSys are used, it was very useful to define the features of the system.
The definition can be seen in \autoref{fig:robmosys}
The current definition of features allows to start the implementation with a component.
When the component is finished features can be implemented by following the tree upwards.
\begin{figure*}
\centering
\includegraphics[width=0.85\linewidth]{graphics/robmosys}
\caption{Feature Definition based on the separation of levels introduced by RobMoSys}
\label{fig:robmosys}
\end{figure*}

\subsubsection{Evaluation}
Even though there is a feature definition that can be used in the next step, there remain a couple of difficulties.
There is still a really strong border between features and components.
And the single level of components makes it impossible to depict the dependencies between components.
Developing larger and complex systems will have sub-components in the system, introducing even more dependencies.
Therefore, this is not a valid solution for feature definition.
Fortunately the current solution suffices to continue the case study.
\subsubsection{Evaluation}
Even though there is a feature definition that can be used in the next step, there remain a couple of difficulties.
There is still a clear separation between features and components.
And the single level of components makes it impossible to depict the dependencies between components.
Developing larger and complex systems will have sub-components in the system, introducing even more dependencies.
Therefore, this is not a valid solution for feature definition.
Fortunately the current solution suffices to continue the case study.

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content/case_experiment_initial_design.tex Wyświetl plik

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%&tex
\subsection{Initial design}
\label{sec:initialdesign}
The initial design started with a design space exploration.
The goal was to collect possible solutions and ideas for the implementation.
The exploration resulted in a lot of whiteboard writing robots.


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