Review end-effector section

content/case_experiment_end-effector.tex

@@ -1,64 +1,62 @@
 With the preparation phase completed, the development cycle is next.
 This consists of three steps: Feature selection, Rapid Development and Variable Approach.
 The current section explains the first development cycle during the design.
-For this first cycle of the design process, I will develop the end-effector.
-The implementation of the end-effector was not successful, as the design was too complex.
-Fortunately, this failure did give valuable insight on the design method.
+For this first cycle of the design process, I design the end-effector.
+However, not long after the start of the development process, the implementation proved to be too complex.
+This led to the decision to abort the implemention of the end-effector.
+Eventhough no progress was made, this attempted implementation did provide valuable insight in the desing process.
 
     \subsection{Feature Selection}
         \label{sec:case_feature_selection_1}
         \begin{table}[]
-            \caption{Overview of the different features and their dependencies, number of tests that can be completed and the risk/time factor.
+            \caption{Overview of the different features and their dependencies, number of tests that are covered and the risk/time factor.
             The risk/time factor is calculate as risk divided by time.}
             \label{tab:firstfeatureselection}
             \begin{tabular}{|l|l|l|l|l|l|}
                 \hline
                 Feature      & Dependees   & Tests  & Risk   & Time    & Risk/Time  \\ \hline
-                SCARA        & -           & 3      & 40\%   & 10 days & 4          \\ \hline
-                End-effector & SCARA       & 2      & 60\%   & 8 days  & 7.5        \\ \hline
-                Carriage     & -           & 2      & 30\%   & 10 days & 3          \\ \hline
+                \ac{scara}        & -           & 3      & 40\%   & 10 days & 4          \\ \hline
+                End-effector & \ac{scara}       & 2      & 60\%   & 8 days  & 7.5        \\ \hline
+                \ac{cdc}     & -           & 2      & 30\%   & 10 days & 3          \\ \hline
             \end{tabular}
         \end{table}
-        The feature is selected according to the feature selection step, explained in \autoref{sec:feature_selection}.
-        For each component in the system the dependees, tests and risk/time factor is determined.
+        For each feature in the system the dependees, tests and risk/time factor is determined, as explained in \autoref{sec:feature_selection}.
         These values are combined into \autoref{tab:firstfeatureselection}.
 
-        The SCARA is dependent on the end-effector, as was explained in the initial design.
-        However, for the carriage no dependency was defined even though it has to lift the other two components.
-        This is mainly because the behavior of the SCARA changes depending on the end-effector, resulting in a possible design change.
-        For the carriage it only changes the mass that has to be lifted.
+        The \ac{scara} depends on the end-effector, as explained in the initial design.
+        However, for the \ac{cdc} no dependency was defined even though it has to lift the other two components.
+        This is mainly because the torque and range requirements of the \ac{scara} depending on the implementation of the end-effector.
+        Especially the required range depends on the method of grabbing and releasing tools.
+        For the \ac{cdc} it only changes the mass that has to be lifted.
         Upgrading the motor torque is a minor parametric change and the dependency is therefore insignificant.
 
-        The testing number is directly the number of tests that can be completed by implementing that single component.
+        The testing number is directly the number of tests that apply to that feature.
         The risk and time values are not determined with a specific protocol, but with simple engineering judgement.
         The estimated risk is high for the end-effector due to the collision dynamics of the operation.
         It has to grab something and that is difficult to model. Furthermore, it was not known if that design would work.
-        The SCARA has the most moving parts, but no difficult dynamics and has therefore an estimated risk of medium.
-        For the carriage there was no real risks and got therefore a low risk indication.
+        The \ac{scara} has the most moving parts, but no difficult dynamics and has therefore an estimated risk of medium.
+        For the \ac{cdc} there was no real risks and got therefore a low risk indication.
         
-        The SCARA would be implemented first based on number of tests, but is dependent on the end-effector.
-        Beginning with the end-effector is an obvious choices. 
-        It unlocks the SCARA and has the highest risk/time factor.
+        Based on \autoref{tab:firstfeatureselection}, the end-effector is implemented first.
+        The end-effector has the most dependees, and is therefore chosen above the other two.
 
         \subsubsection{Evaluation}
             This first step of the detail design phase did go well.
-            A more refined method for this step could be very useful.
-            But the risk and time assessment will probably always be a engineering judgement from the developer.
+            Although risk and time assessment is always depend on some engineering judgment, this human factor introduces uncertainty in the assessment.
+            However, an improved approach for the risk assesment can drastically reduce this human factor.
             Within a design team a form of planning poker \autocite{grenning_planning_2002} could be a good option.
         
-    \begin{figure}
-        \centering
-        \includegraphics[width=0.9\linewidth]{graphics/end-effector.pdf}
-        \caption{Operation of the end-effector. The marker is clamped in the springloaded end-effector (1).
-        To release the marker, the upper part of the clamp is placed against the holder (2). This extra arm length is used as a leverage to open clamp while the end-effector moves downwards (3,4).
-        The arm length also allows to move backwards without disturbing the marker (5,6). To grab the marker, the process is repeated in reverse.}
-        \label{fig:gripper}
-    \end{figure}
-
     \subsection{Rapid Development of the End-Effector}
-        The end-effector will operate as an interface between the SCARA and the different tools.
-        For that it has to be able to grab and release the tools.
-        The end-effector is mounted at the end of the SCARA.
+        This section explains the process of the development of the end-effector.
+        The first step is to create an initial design of the model.
+        In subsequent steps, detail is added to this model.
+
+        The previous section explained the relative high risk assessment  for the end-effector.
+        Which was not exaggerated as the implementation proved to be troublesome.
+        Eventually, the implementation was unfeasible and was therefore cut short.
+        Nonetheless did it result in useful evaluation points on the design method.
+        The process of this step is explained in the following sections.
+
 
         The development starts with an initial design of the system.
         The next step is to develop that further into a model and prototype.
@@ -66,28 +64,41 @@ Fortunately, this failure did give valuable insight on the design method.
         However, the evaluation gave new useful insight on the design plan.
 
         \subsubsection{Initial design}
-        There are multiple options to connect a tool with a moving arm.
-        However, there is a trade-off to be made with the SCARA feature, the heavier the end-effector is, the more force the SCARA must deliver.
-        And because the goal is to make the SCARA light and quick, this end-effector should be light-weight.
-        The best options in this case is to go with a simple spring-loaded clamp.
-        It is light-weight, and provides sufficient clamping force and precision for this application.
-        To release the tool, the clamp must be forced open.
-        Instead of using a servo, the movement of the SCARA can force the clamp open, resulting in a significant simplification of the design.
-        The initial design of the clamp and the operation is shown in \autoref{fig:gripper}. 
+            The end-effector is mounted on the \ac{scara} and acts as an interface.
+            With the end-effector, the \ac{scara} is able to grab and release tools.
+            There are multiple approaches to handle these tools.
+            However, there is a trade-off to be made with the \ac{scara} feature, the heavier the end-effector is, the more force the \ac{scara} must deliver.
+            And because the goal is to make the \ac{scara} light and quick, this end-effector must be light-weight as well.
+            The best options in this case is a simple spring-loaded clamp.
+            To release the tool, the clamp is forced open, pushing it against the holder.
+            As the end-effector is connected to the \ac{scara}, the \ac{scara} is responsible for the pushing force.
+            Because the actuation force of the \ac{scara} is used, it removes the need for an additional servo in the end-effector.
+            Resulting in a simpler and lighter design.
+            The initial design of the clamp and the operation is shown in \autoref{fig:gripper}. 
+            Although this design requires the \ac{scara} to deliver more force.
+            The relative low mass of the end-effector also keeps the moment of inertia small.
+            Therefore, the current design reduces the impact on the acceleration of the \ac{scara} to a minimum.
+            \begin{figure*}
+                \centering
+                \includegraphics[width=151mm]{graphics/end-effector.pdf}
+                \caption{Operation of the end-effector. The clamp is forced open against the holder to release the marker.
+                Instead of releasing, the marker is grabbed by reversing the order of executing for these steps.}
+                \label{fig:gripper}
+            \end{figure*}
 
         \subsubsection{Behavior Modelling}
-        The next step is to implement this design with the corresponding behavior in a dynamic model.
-        The challenge in this case is the modelling of the contact dynamics.
-        Based on some experience in modelling with collisions, I decided to use the 20-sim 3D mechanics editor.
-        There is little tooling available and there are no debugging options if the model does not behave as expected.
-        The marker kept falling trough the gripper or flew away.
-        With the small amount of progress made in two days the implementation was not promising. 
-        A system freeze caused the model to corrupt, where the complete configuration of the shapes and their collisions was lost.
-        Based on the loss of work and the low feasibility of the implementation, it was decided that the end-effector would no longer be part of the design.
+            The next step is to implement this design with the corresponding behavior in a dynamic model.
+            The challenge in this case is the modelling of the contact dynamics.
+            Based on some experience in modelling with collisions, I decided to use the 20-sim 3D mechanics editor.
+            Unfortunately, there is little tooling available and there are no debugging options if the model does not behave as expected.
+            The marker kept falling trough the gripper or flew away.
+            With the small amount of progress made in two days the implementation was not promising. 
+            A system freeze caused the model to corrupt, where the complete configuration of the shapes and their collisions was lost.
+            Based on the loss of work and the low feasibility of the implementation, the decision was made to remove the end-effector from the design.
 
-        With the end-effector removed, the SCARA will get a direct connection with the marker.
-        The lifting of the marker from the will be included in the SCARA as well.
-        Furthermore, this means that the wiping will no be possible via the SCARA.
+            With the end-effector removed, the \ac{scara} gets a direct connection with the marker.
+            The lifting of the marker from the is included in the \ac{scara} as well.
+            Furthermore, this means that the erasing is no longer possible as a feature.
 
         \subsubsection{Evaluation}
             The lost progress of the model is unfortunate, but the implementation did not go as expected anyway.
@@ -95,4 +106,3 @@ Fortunately, this failure did give valuable insight on the design method.
             However, it did show the value of the risk/time analysis.
             This early failure resulted in changes for other components.
             But as none of the components were implemented yet, no work was lost.
-

graphics/end-effector.tex

@@ -6,7 +6,7 @@
 %\input{graphics/tics.tikz}
         
 \begin{document}
-    \begin{tikzpicture}[x=0.6cm, y=0.6cm]
+    \begin{tikzpicture}[x=0.9cm, y=0.9cm, nodes={text width=4.5cm,anchor=north west,draw=none}]
         \def \markerradius {0.5};
         \def \angle {40};
         \def \startangle {-90-\angle};
@@ -20,8 +20,8 @@
         \def \blockdistance {2.8}
         \def \blockpos {(0,0)};
         \def \markerdrop {0.5};
-        \def \spacing {5.5};
-        \def \yspacing {3.9};
+        \def \spacing {5.6};
+        \def \yspacing {4.6};
     \tikzset{
         block/.pic=
         {
@@ -45,13 +45,13 @@
             \draw[fill=gray] (0,0) circle(\markerradius);
         }
     }
-        \def \nodepos {(\blockdistance+1,1.9)};
+        \def \nodepos {(\blockdistance-4.0,2.9)};
     \begin{scope}[shift={(0*\spacing,0)}]
         \def \eex {1.3};
         \def \eey {-0.5};
         \pgfmathsetmacro{\clampangle}{max(0,atan2(\eey,{\blockdistance+\eex}))};
         \draw \blockpos pic {block};
-        \node at \nodepos {1.};
+        \node at \nodepos {1. Marker is clamped in springloaded end-effector.};
         \draw (2-\eex,{\markerradius+\eey*-1}) pic {marker};
         \begin{scope}[shift={(-\eex,-\eey)}]
             \draw (0,0) pic {lowerclamp};
@@ -63,7 +63,7 @@
         \def \eey {0};
         \pgfmathsetmacro{\clampangle}{max(0,atan2(\eey,{\blockdistance+\eex}))};
         \draw \blockpos pic {block};
-        \node at \nodepos {2.};
+        \node at \nodepos {2. End-effector is positioned on the holder.};
         \draw (2,\markerradius) pic {marker};
         \begin{scope}[shift={(-\eex,-\eey)}]
             \draw (0,0) pic {lowerclamp};
@@ -75,7 +75,7 @@
         \def \eey {0.5};
         \pgfmathsetmacro{\clampangle}{max(0,atan2(\eey,{\blockdistance+\eex}))};
         \draw \blockpos pic {block};
-        \node at \nodepos {3.};
+        \node at \nodepos {3. End-effector is moved down, forcing the upper clamp open.};
         \draw (2,\markerradius-\markerdrop) pic {marker};
         \begin{scope}[shift={(-\eex,-\eey)}]
             \draw (0,0) pic {lowerclamp};
@@ -87,7 +87,7 @@
         \def \eey {0.7};
         \pgfmathsetmacro{\clampangle}{max(0,atan2(\eey,{\blockdistance+\eex}))};
         \draw \blockpos pic {block};
-        \node at \nodepos {4.};
+        \node at \nodepos {4. End-effector continues down, leaving the marker in the holder.};
         \draw (2,\markerradius-\markerdrop) pic {marker};
         \begin{scope}[shift={(-\eex,-\eey)}]
             \draw (0,0) pic {lowerclamp};
@@ -99,7 +99,7 @@
         \def \eey {0.7};
         \pgfmathsetmacro{\clampangle}{max(0,atan2(\eey,{\blockdistance+\eex}))};
         \draw \blockpos pic {block};
-        \node at \nodepos {5.};
+        \node at \nodepos {5. The longer arm allows the end-effector to move sideways.};
         \draw (2,\markerradius-\markerdrop) pic {marker};
         \begin{scope}[shift={(-\eex,-\eey)}]
             \draw (0,0) pic {lowerclamp};
@@ -111,7 +111,7 @@
         \def \eey {0};
         \pgfmathsetmacro{\clampangle}{max(0,atan2(\eey,{\blockdistance-\eex}))};
         \draw \blockpos pic {block};
-        \node at \nodepos {6.};
+        \node at \nodepos {6. Return to begin position, now without marker.};
         \draw (2,\markerradius-\markerdrop) pic {marker};
         \begin{scope}[shift={(-\eex,-\eey)}]
             \draw (0,0) pic {lowerclamp};
@@ -119,8 +119,8 @@
         \end{scope}
     \end{scope}
 
-    \draw (4.2,-1.3*\yspacing) -- ++(0,1.9*\yspacing);
-    \draw[shift={(\spacing,0)}] (4.2,-1.3*\yspacing) -- ++(0,1.9*\yspacing);
+    \draw (4.2,-1.3*\yspacing) -- (4.2,2.9);
+    \draw[shift={(\spacing,0)}] (4.2,-1.3*\yspacing) -- (4.2,2.9);
     \draw(-1.4,-1.5) -- ++(3*\spacing,0);
 
     \end{tikzpicture}

include

@@ -1 +1 @@
-Subproject commit c481ca012ef63f75bae07a0174d5098a4623e8e9
+Subproject commit c60fc733267eb72f37dc3228cf76d95be5a7d7db