\chapter{Actuation system}

\section{Overview}

This chapter describes the design stage of the pedal actuation unit: frame design, pneumatic components selection and design as well as manufacture of the custom parts, that link the pneumatic cylinders to the vehicle pedals.

\section{Design}

The pedal actuation unit (fig \ref{fig:pedal_actuator}) project was desegned based in simple principles.

\begin{itemize}
  \item The unit has to be compact;
  \item Easy and quick to install;
  \item Easy to operate;
  \item Simple to remove, so the vehicle can be driven to the test site, the systems are installed in few minutes, and after the tests the unit is detached from the vehicle and it can be driven back again.
\end{itemize}

To accomplish this goal, the unit frame was developed using Bosch Rexroth aluminium framing, and pneumatic actuators were used to provide compliance and compact design. The actuators are controlled by electric pressure regulators to simulate human force control. To ensure system robustness the actuation unit central control will be assigned to an industrial PLC.

\begin{figure}
  % Requires \usepackage{graphicx}
  \centering
  \includegraphics[width=0.7\textwidth]{Actuators2}\\
  \caption{Pedal actuator unit}\label{fig:pedal_actuator}
\end{figure}

For designing purposes, the force needed to actuate the vehicle controls was measured using a load cell. The maximum values registered were: 80N for accelerator, 375N for brake, 205N for clutch and a torque of 7.5N/m for the steering wheel.

\section{Frame}

For assembly ease, the frame (fig \ref{fig:frame}) is designed out of Bosch Rexroth 30x30mm aluminium framing, and fits in front of the vehicle driver seat. It is designed to be light, and easy to install, remove and store. It provides support to all pneumatic actuation components.

\begin{figure}
  % Requires \usepackage{graphicx}
  \includegraphics[width=0.9\textwidth]{frame}\\
  \caption{Frame dimensions}\label{fig:frame}
\end{figure}


\section{Pneumatic components}
With the base values from the force tests the following pneumatic equipment was selected:

\begin{itemize}
  \item Cylinders: SMC CP95SDC32-200;
  \item Electric pressure regulators: SMC ITV0050-L (fig \ref{fig:ITV_work} \& \ref{fig:ITV});
  \item Manual pressure regulator: SMC ARX21-01B;
  \item Tube: $\varnothing 4 mm$
  \item Tube accessories: SMC KQ2 series
  \item Silencer: SMC AN A1-01
\end{itemize}

\begin{figure}
  % Requires \usepackage{graphicx}
  \centering
  \subfloat[]{
    \includegraphics[width=0.5\textwidth]{ITV00_work}
    \label{fig:ITV_work}}
  \hfill
  \subfloat[]{
    \includegraphics[width=0.2\textwidth]{ITV00}
    \label{fig:ITV}}
  \caption{SMC ITV00 working principle\cite{SMC_ITV} (a) and package (b)}
\end{figure}

\section{Custom parts}

Custom parts were designed to fix the pneumatic cylinders to the vehicle pedals. To comply with the required movement degrees of freedom, the attachment has two parts. One, as seen in figures \ref{fig:rod_att1} and \ref{fig:rod_att} has one M10 thread which is attached to the pneumatic cylinder rod and was machined from a block or aluminum. The other, as seen in figures \ref{fig:CLTCH_BRK1} and \ref{fig:CLTCH_BRK} is shaped so it fits each of the ATLASCAR1 pedals and locks into place by the spring effect from the shape itself and was cut and fold from steel sheet metal.

\begin{figure}
  % Requires \usepackage{graphicx}
  \centering
  \includegraphics[width=0.6\textwidth]{rod_att1}\\
  \caption{Cylinder rod attachment}\label{fig:rod_att1}
\end{figure}

\begin{figure}
  % Requires \usepackage{graphicx}
  \centering
  \includegraphics[width=0.8\textwidth]{rod_att}\\
  \caption{Cylinder rod attachment drawing}\label{fig:rod_att}
\end{figure}

\begin{figure}
  % Requires \usepackage{graphicx}
  \centering
  \includegraphics[width=0.5\textwidth]{CLTCH_BRK1}\\
  \caption{Clutch and brake pedals attachment}\label{fig:CLTCH_BRK1}
\end{figure}

\begin{figure}
  % Requires \usepackage{graphicx}
  \centering
  \includegraphics[width=0.5\textwidth]{CLTCH_BRK}\\
  \caption{Clutch and brake pedals attachment drawing}\label{fig:CLTCH_BRK}
\end{figure} 