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2Jan/100

Underwater ROV (Part 1) – Ideas and using off the shelf parts.

I was recently reading the public safety diver magazine and noticed the small commercial ROV's listed.  Intrigued I went to each site took a look then noticed the pricing.  They cost thousands if not tens of thousands to procure one.  I thought to myself, what if I just want a simple one to for what I've see as a need?  So I set out to do a quick feasibility study on build a small ROV for use with search and rescue and otherwise just something fun, useful, and inexpensive.

Design Goals

  • 50 ft average depth 100-125 ft max
  • Video
  • Surface controlled.
  • Tethered
  • Use easy to get materials.
  • Cost somewhere between $200-$1000
  • Small enough for one person to deploy

A quick search thru the web showed me that many people had indeed built ROV's well within the constraints above.  The big issues I saw was many didn't have a lot of thrust or directional control, didn't have speed control, didn't have camera pan/tilt/zoom, no belly cam.

I first realized the issue of how to get proportional control of all controls. Well the easiest method seemed to be electronic speed control using RC or hobby technologies.  The seem cheap enough and with a some embedded linux and a Cat5 tether I suppose one could solve both the control functions, telemetry, video etc all over ethernet buy embedding a linux cpu into the ROV.  Something like the gumstix or maybe even a atom board or maybe a PC104 ARM based board.   It could even be broken up to so that something like the http://www.pololu.com/ devices could control the RC gear including servos.  There are a lot of USB cabs to be had to put as many cams as one would need.  Ok so controlling could be pretty simple and commands relayed down to the embedded CPU with a computer with an analog controller or even keyboard controls.  This all seemed doable.

Next problem was thrust and control. At first i really like the idea of using bilge pumps till I released they are big and don't provide a lot of thrust.  Also the best RC ESC would be brushless. A quick browse made it apparently that the RC world had plenty to choose from as far as propulsion and marine ESC controls.  That seems to be the best solution.  On locations for control it would seem that you want to go forward, go backward, up, down, left, right and ability to turn in place.  Put a forward and reverse capible thruster on each of those axises, problem solved.

All the frames I saw were similar using PVC for the frame.  Cheap simple and easy to get the unit to neutral buoyancy.  If idea was to get fancy we'll have plenty of servo outputs to control a buoyancy control using small tank of gas.

After the weekend research session it pretty safe to say that this could be done.  I haven't decided to build anything but have feelers out on EBAY for cheap parts.  If you have built a ROV, wanted to, or are interested let me know.  I'm interested in the project but don't have a lot of time to complete it all on my own.

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