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Autonomous sub powers up with Wheezy on Haswell

Jul 25, 2014 — by Eric Brown 1,321 views

Cornell University’s “Gemini” AUV will compete in next week’s 2014 RoboSub competition. The sub runs Debian Linux on an Intel Core-based computer-on-module.

The Cornell University Autonomous Underwater Vehicle (CUAUV) team’s Gemini AUV will enter next week’s 17th Annual International RoboSub competition with the help of Adlink, whose “Express-HL” COM Express style computer-on-module will power the autonomous sub using a stripped down version of Debian “Wheezy” Linux. The competition will be held at the Space and Naval Warfare Command Research facility in San Diego, from July 28 through August 3.

The Gemini design is intended to demonstrate a reduction in weight, ease of integration and use, and improved control properties, compared to earlier CUAUV AUVs. Gemini features stronger frame structures and pressure vessels, along with a streamlined electronics system, an improved sensor suite, and advanced vision algorithms.

Gemini rendering (top), on land, and in the water
(click images to enlarge)

The 41 x 23 x 18-inch UAV features an acrylic hull and weighs 70 pounds. Gemini can travel at up to 0.6 m/s at a depth of up to 50 feet, for up to two hours.


COM Express-based Embedded computer

Adlink’s Express-HL COM Express Type 6 COM handles all mission, machine vision, and control processing tasks. There is no secondary computer. However, the module communicates with micro-controllers on several custom-built peripheral circuit boards.

Gemini embedded computer photo showing the COM, carrier board, and thermal solution
(click image to enlarge)

The Express-HL module is based on Intel’s quad-core Core I7-4700 system-on-chip of the 4th Generation “Haswell” variety, paired with a Mobile Intel QM87 Express chipset. The Express-HL is connected to a Connect Tech COM Express Ultra Lite Carrier Board. The onboard computer is further equipped with 8GB of RAM and a 256GB mSATA solid state drive. All external sensor and actuator boards are routed through a custom serial interface board.

Adlink Express-HL COM: photo and block diagram
(click images to enlarge)

The Connect Tech Ultra Lite board has a +12V power supply and is rated for industrial temperatures. The 125 x 95 mm board offers four display interfaces, dual gigabit Ethernet ports, six USB ports, and five serial ports. Other features include a microSD slot, dual Mini-PCIe slots, audio I/O, and 8x GPIO.

Debian-based software stack

On the software side, Gemini runs custom Debian and features a custom shared memory system for centralized vehicle state, with interfaces supporting C/C++ and Python programs.​ The shared memory system allows simultaneous access to global variables throughout the vehicle’s software infrastructure. The variables are synchronized across various boards through a standardized serial protocol for easier reading and writing.

The Debian stack includes a logging system that supports offline review and testing. There’s also a simulator program for testing the craft in a virtual environment.

Gemini sensors and other features

The Gemini sensor array includes the following components:

  • Teledyne RDI Explorer Doppler Velocity Log
  • Temperature sensor
  • Custom-built hydrophones
  • IDS uEye downward camera
  • AVT Guppy forward camera
  • Custom-built IMU
  • LORD Microstrain 3DM-GX1 IMU
  • LORD Microstrain 3DM-GX4-25 IMU
  • Depth sensor
  • Internal pressure sensor
  • PNI Trax AHRS Module

Additional Gemini features are said to include:

  • Cantilever rack system
  • Dual hull
  • Main pressure vessel integrated forward cameras
  • Easily accessible Ethernet tether
  • Power system with hot swappable battery pods
  • 8x thrusters for 6 degree of freedom control
  • Redundant main sealing system
  • Wet-mate tether
  • SEACON underwater connectors
  • Plug and play serial
  • Electronics back-panel
  • Vacuum-sealed hull

RoboSub competition

The international RoboSub competition is co-sponsored by the Association for Unmanned Vehicle Systems International (AUVSI) Foundation and the U.S. Office of Naval Research (ONR). The competition’s mission elements and tasks are designed to simulate real-world challenges, such as visual recognition of objects, navigation, and acoustic sensing.

RoboSub 2014 pool and competition diagram
(click images to enlarge)

The 43-student CUAUV team spends more than 20,000 person-hours per year designing its UAVs, and has won the annual RoboSub competition four out of the last five years. The team began testing Gemini in pool and lake waters in June, running the sub through an obstacle course similar to that of RoboSub.

“When we started designing Gemini back in August 2013, we knew that we wanted something smaller and more powerful than the 3rd generation Intel Core i7 processor on Mini-ITX form factor that we used on our 2013 vehicle,” stated Markus Burkardt, CUAUV team leader and Cornell University senior. “We decided that a quad-core computer-on-module was the best option to reduce overall vehicle weight and footprint without giving up performance, so we started contacting vendors for support. We were really happy when Adlink agreed to be our sponsor.”

Other Linux-based AUVs include Bluefin Robotics’s Bluefin-21 automated mini-sub, which has been leading the search for Malaysia Airlines Flight 370. On the low end, you can voyage to the bottom of your pool with the BeagleBone based OpenROV.

Two other underwater AUVs: Bluefin-21 (left); OpenROV
(click images to enlarge)

Further information

More information on Gemini may be found at CUAUV’s Gemini page, and details about RoboSub may be found at the AUVSI RoboSub page.

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