"Auto" head, pitch, and roll using ArduPilot?

I would like to automatically control my ROV's (underwater Remotely Operated Vehicle's) heading, pitch (and possibly roll).  Since GPS doesn't work underwater, I'll need to use a compass that outputs heading, pitch and roll such as this one:  http://www.sparkfun.com/commerce/product_info.php?products_id=8960 .  Communications to the ROV will be by either serial or ethernet.  The vehicle will be stationary when auto head, pitch, roll are engaged, and I plan on using 4 thrusters for maneuvering.

I initially thought to use a Pico ITX motherboard onboard the ROV and some code that talks to a serial servo controller.  Then I started to look at using an Arduino and then wondered if this might be done with an ArduPilot?

So is this possible?  If so how difficult will it be to achieve and where do I start?

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  • Here is another idea to consider on a underwater ROV. The GPS signal can be recieved to a surface vessel and sonar waves can travel to and from an ROV. You could use a system similar to that used by GPS and create your own water bourn grid of sattelite transmitters to triangulate positions. For example: syncronize three signals to a common time base that transmits out a sonar pulse from 3 separate locations. Sample the time delay to the ROV and thereby determine position. Run this signal through a program that compares your boat's GPS position to that of the ROV and you can easily transfer through mediums.

    All fluids have a speed of propagation. Whether it be air, water or some other medium. Sonar pulses can be coded to lock out other, spurious, noise and these signals can be decoded similar to the way RC signals are decoded. The floating transmitters could actually be quite small to be effective. Look at the size of a standard fish locator. The transmitter would be quite similar and multiplexing signals is simple on the surface where radio waves can be used.
    Interesting concept.
    Skip
    Seattle
  • bigkahuna, this might be a dumb question, but if GPS signals are bounced off the water's surface, how are you going to get a signal down to your radio RX or X-Bee or whatever to control your ArduPilot? Serial or Ethernet across what? A wire?

    I realize this post is a few months old, I'm just wondering if you've had any headway.
  • Hello,
    There may be some interesting options to consider for a project of this type. GPS is based on a time signal from sattelites to a handheld real time clock. The shift in this signal between three points is what gives you your coordinates. What you may be able to do is to reference this signal to your own support boat and then send this data to your submersible with hydrophone technology. Since the signal in the water is also a constant (barring thermoclines and salinity changes) you could use this data with an onboard digital compass to give position estimates based on GPS. This data could be reduced to a vector equation which should be fairly easy to program into your source code.

    Just an idea but I have often thought that many signals could be multiplexed with this process. Even impressing Video signals in the sonar wave. You have to consider this as a similar medium to air. Both can resonate the sum, difference and the original waves. It is quite possible that you could develope a system for underwater similar to the Ardupilot or adapt those features to your own use. What it comes down to are the types of sensors you use to collect data about your surroundings. From there the brain of the craft is identicle. I would go with the Arduino Mega. You need more memory capacity to dicern underwater signals and you may want to expand in the future. Unless, of course, you are limited by size.
    Regards,
    Skip
  • Moderator
    Why doesn't GPS work underwater, the signal should reach or how deep are you planning to go?
  • Is the system just for stabilisation?

    Be careful of magnetometers if you are going to be near wrecks and shipping.

    When you say heading do you mean so that it points or travels in a particular direction - or both?

    Have you seen the Homebuilt ROV site? They have a lot of useful links and you might find something there.
  • 3D Robotics
    You will able to do that with ArduPilot Mega or ArduIMU+ and our new magnetometer. You'll have to tweak the code a bit yourself for ROV purposes, of course.
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