| @@ -145,6 +145,36 @@ | |||
| Therefore, the last detail, the marker lifting, was added without any difficulty. | |||
| The servo is connected via a linkage with the marker such that it rotates away from the board. | |||
| \subsubsection{Component Design} | |||
| At this point the development has produced a design with a competent dynamic model. | |||
| The developed design does, however, not incorporate the physical component design. | |||
| Nevertheless, must these components be designed to validate that the SCARA and its components can be constructed. | |||
| For the mechanical part I used OpenSCAD as CAD software, based on prior experience with the software. | |||
| With this it was possible to implement all the components that have to be made, as well as the \ac{ots}-components. | |||
| Using the inverse kinematics model from the basic design of the SCARA, the angles were directly applied on the components in system. | |||
| Allowing me to change the configuration of the SCARA and inspect the clearance between each component. | |||
| Following the rectangular path as defined in \autoref{test1}, it revealed that collision occurred between some parts. | |||
| These collisions were resolved by adding an indentation and moving linkage and are shown in \autoref{fig:scad_clearance} | |||
| The configuration with the stepper motors, servo and marker is shown in \autoref{fig:scad_carriage}. | |||
| \begin{figure} | |||
| \centering | |||
| \includegraphics[width=0.8\linewidth]{graphics/scad_scara_circles.png} | |||
| \caption{ | |||
| CAD of the SCARA configuration, with the end-effector orientated in the lower left corner of the operating area. | |||
| The configuration has been adapted at the two circled points, to resolve collisions in this orientation. | |||
| An indentation was made to ensure that the arm could make the required corner. | |||
| Furthermore, the bottom linkage has been moved from above to below the actuated joints, as this linkage would otherwise collide with the end-effector. | |||
| } | |||
| \label{fig:scad_clearance} | |||
| \end{figure} | |||
| \begin{figure} | |||
| \centering | |||
| \includegraphics[width=0.8\linewidth]{graphics/scad_carriage.png} | |||
| \caption{Rendered 3D model of the SCARA, including steppers, marker and servo.} | |||
| \label{fig:scad_carriage} | |||
| \end{figure} | |||
| \subsubsection{Evaluation} | |||
| The complete development was rather smooth. | |||
| However, this was not without deviating from the original design plan. | |||
| @@ -158,18 +188,3 @@ | |||
| For example, changing the arm lengths and evaluate the new behavior. | |||
| Did it improve? Is this as expected? | |||
| Implicitly, the system was very often tested and changed based on test results. | |||
| Furthermore, the step from 2D to 3D physics was in no means a small increment in detail. | |||
| The first four levels of detail, as describe in the previous section, all were implemented in with two dimensions. | |||
| As the later details required a third dimension, all the detail was directly converted from 2D into 3D. | |||
| This is a large amount of work, introducing a high cost when the conversion fails. | |||
| Moreover, it creates a new 3D physics model, parallel to the 2D physics model instead of adding detail to the latter. | |||
| Alternative approaches for 3D model physics could be: | |||
| \begin{itemize} | |||
| \item Ignore 2D and start implementation in 3D modelling. | |||
| \item Retrace all incremental detail steps of the 2D model in a 3D model. | |||
| \end{itemize} | |||
| Both options are not ideal, the first one does not allow a simple basic model and the second approach redoes work. | |||
| The advantage of starting with 3D is that allows for a continuous development of one model, instead of switching the complete model. | |||