The "CAUV 2008"

By Cambridge University, UK Posted on October 10th, 2008

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The Aim

The CAUV 2008 is an Autonomous Underwater Vehicle that has been designed to compete in the Student Autonomous Underwater Challenge - Europe (SAUC-E). It is one of the smallest robots at the competition weighing in at just under 7kg. It makes use of the world's smallest full-featured x86 mainboard, the Pico-ITX, to power the autonomy software which guides it through an underwater assault course.

The SAUC-E competition is a Europe wide competition aimed at University level students. The teams design and build their own AUVs that must attempt an underwater assault course that may vary from year to year but can consist of gates, drop targets and surface zones that may have to be detected by visual or acoustic means.

The Preparation

AUV Specification:

• 1 GHz EPIA PX 10000 mainboard
• 1 GB RAM
• 4GB CF Card
• 2 x Logitech Quickcam Pro 4000
• 4 x Internal vector thrusters*
• 1 x 100W Brushless Motor
• 5 x 30A MAG8 electric speed controllers
• 1 x Belkin Wireless USB Adapter
• 1 x Inertial Measurement Unit*
• 12 x 2400mAHr LiPol Batteries
• 1 x M3-ATX picoPSU 125W
• Battery Management System*
• Carbon Fibre Hull*
• Aluminium Connectors*

Items marked with (*) are ones we have built ourselves.

Calculations using a basic fluid dynamics model show that our AUV should be able to reach a maximum speed of around 4.2m/s and a maximum range of 40km at a cruising speed of 2.4m/s.

The AUV is 1.1 meters long and has a 90mm diameter with 4 internal vectored thrusters to provide manoeuvrability and a 100W rear propeller for high speed cruising. The AUV has full control over yaw, pitch, forward, sideways and vertical movement; roll is controlled passively by the low centre of gravity. The main sensors include an Inertial Measurement Unit; two cameras and pressure sensors. All this hardware is controlled by the high level decision software, written in Java and run on the Pico-ITX.

The Pico-ITX setup uses a 1 GHz processor, 1GB RAM, a 4GB CompactFlash as the storage device and an M3-ATX Wide Input PICO-PSU. The Pico-ITX has been fitted into an easily removable module that slides into the central section of the AUV. The central section contains the heart of the AUV consisting of the Pico-ITX, the battery module, the INS and the central hub. The central hub is a set of connectors that break through the carbon fibre hull, that various payloads can be plugged into, such as a marker dropping system, an acoustic modem or a side scan sonar.

To communicate with the AUV we have two options, firstly the tether, a long Ethernet cable that attaches to a waterproof connector on the top of the AUV. Secondly we have an 802.11g wireless USB adapter in the vehicles nose cone, allowing for surface communication.

The PICO testing rig used for software debugging. On the AUV we use Ubuntu Server 8.04.

The processor module drying out in the sun after an unintended bath. Ooops.

Spot the difference.

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