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\begin{document}

\begin{labcover}
\labtitle{The PABLOX}
\vspace{0.1in}
\labdate{August 2017}
\vspace{0.1in}
\labauth{Michael Benjamin, mikerb@mit.edu}
\labauth{Department of Mechanical Engineering}
\labauth{MIT, Cambridge MA 02139}
\labtoc{small}
\end{labcover}

\wikidoc{file=PavLab.PabloX}
\wikidoc{auth=mikerb@mit.edu}

%=================================================================
\section{The PABLOX System}
%=================================================================
\label{sec_pablo_sys_background}

Payload autonomy is a method of operating robotic units where the
mission-level and decision computing components of the system are
separated from the low-level actuation systems. Typically, a "front
seat" consists of computing units that are embedded in the vehicle and
have direct management of control surfaces. A "back-seat" computer,
physically connected as a payload on the vehicle, contains the
autonomous navigation and other action-decision logic. In short, the
payload autonomy system handles vehicle motion decisions while the
vehicle's native controller affects the movement.

Implementing a payload autonomy paradigm simplifies robotic
development and deployment but requires constructing a dedicated box
to house, power, and protect the back seat computer. MIT's Pablo Unit
was developed as a payload autonomy box (the "PAB" of Pablo). While
initially designed to interface with a specific vehicle (the Clearpath
Robotics Kingfisher M200), the modular design can support alternative
payload connectors and computer boards.

At MIT, the greatest strength of the payload autonomy paradigm is in
supporting classroom instruction and research efforts. The M200
vehicles are expensive and each unit requires ongoing resources for
upkeep, batteries, and storage.  Historically, students using the
vehicle would require hours-long blocks of time to load software onto
the embedded computer then iteratively test and improve their
work. With payload autonomy, each student is given a Pablo box to use
at his or her leisure, testing the box against a vehicle emulator
running on the student's laptop. During class time, the Pablo box is
connected to the real vehicle with a minimal time spent on
configuration.

Pablo boxes also provide the secondary benefit of scaling up
simulations of multi-vehicle missions. Each unit is effectively a
back-seat computer that is already configured to run the mission and
autonomy components on a networkable device. By running a simulator on
the embedded computer, a large number of boxes can be connected to
simulate a swarm or collection of vehicles. The logistics of managing
multiple networked Pablo boxes is far simpler than attempting to run
many simulations on a common machine and much less expensive than
purchasing and configuring many laptop or desktop computers.

%====================================================================
\section{System Hardware Components}
%====================================================================
\label{sec_system_components}

The Pablo System is comprised of the following:

\begin{packed_itemize}
\item {\em (2) Clearpath Robotics Kingfisher M200 unmanned surface 
  vehicles} \\
\item {\em (25) Pablo Boxes.} \\
\item {\em (5) M200 Data Harnesses.} \\
\item {\em (5) Payload Power Pack.} \\
\end{packed_itemize}


%====================================================================
\section{M200 Vehicle Subsystem}
%====================================================================

The M200 robotic boat is the actual deployed vessel. Each vehicle
includes its embedded computer that processes OEM sensors and
interfaces to the motor controllers. When the vehicle is deployed, a
Pablo unit can be installed in the payload bay, interfacing via a
waterproof Ethernet connector.

When purchased, the M200 subsystem includes:

\begin{packed_itemize}
\item Clearpath Robotics Kingfisher M200 main unit \\
\item Payload bay lid \\
\item 2 x M200 battery units \\
\item 2 x battery chargers \\
\end{packed_itemize}

\vspace{0.1in}
\begin{figure}[H]
  \centering 
  \includegraphics[width=0.6\textwidth]{figures/M200.png}
  \caption{A Clearpath Robotics Kingfisher M200 vehicle underway. The rear 
    hatch is closed, helping to secure the Pablo unit inside. }
  \label{fig_PABLO}
\end{figure}
\vspace{0.1in}

%====================================================================
\section{Pablo Unit}
%====================================================================

Each Pablo box acts as an independent computing unit that runs a 
GNU/Linux-based operating system and the MOOS-IvP suite of autonomy 
applications. The housing is waterproof and includes connectors to interface 
with the vehicle, external devices, and battery or shore power.

Pablo units are assembled manually from existing parts. The main components 
used in a Pablo unit include:

\begin{packed_itemize}
\item Waterproof housing with clear lid \\
\item Raspberry Pi computer with data storage and TFT display \\
\item Waterproof connectors for USB, Ethernet, and power \\
\item Internal data and power cables \\
\item Internal mounting hardware \\
\item AC-DC shore power supply \\
\end{packed_itemize}

\vspace{0.1in}
\begin{figure}[H]
  \centering 
  \includegraphics[width=0.6\textwidth]{figures/pablo_cover.png}
  \caption{A single PABLO unit with its AC-DC power supply. }
  \label{fig_PABLO}
\end{figure}
\vspace{0.1in}


%====================================================================
\section{Data Harness}
%====================================================================

The data harness is a waterproof cable that connects the Pablo box
Ethernet port to an M200 payload connector. Onshore, Pablo units
connect with standard Ethernet cables but a custom harness is required
when deploying Pablo on the vehicle to mate unique waterproof
connections.

A data harness is comprised of:

\begin{packed_itemize}
\item Waterproof Ethernet plug and cable (Bulgin) that connects to the 
  Pablo unit \\
\item Waterproof Ethernet plug (CONEC) that is attached to the Bulgin 
  connector \\
\end{packed_itemize}

%====================================================================
\section{Power Pack}
%====================================================================

The power pack includes a battery, power regulator, and waterproof cable to 
supply 5-volt power to the Pablo unit. Onshore, AC-DC power supplies are used 
but a custom power assembly is required when deploying Pablo on the vehicle.

The power pack subsystem includes:

\begin{packed_itemize}
\item Rechargeable NiMH battery \\
\item DC-DC regulator to ensure a steady 5-volt supply \\
\item Waterproof barrel connector to interface with a Pablo unit
\end{packed_itemize}

\end{document}

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