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Ring Laser Gyro

Posted by Miles on August 5, 2010 at 4:17pm
Hi Everyone,

Just an idea here and yes I know its out of DIY community price range but could the IMU on autopilots in general be replaced with Ring Laser Gyro to improve overall performance e.g. position, IMU drift etc. Just a thought.

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Replies

  • Patrick Hammer August 6, 2010 at 2:26pm
    An interesting article about inertial sensor technology trends can be read at:

    http://www.draper.com/digest99/paper1.pdf

    Written in 1998, it’s interesting to compare what was predicted then, to what the “state of play” is now.

    How far off were the authors?

    In terms of nav technology trends filtering down to hobby/amatuer users & applications, I think the next big real world benefit hobby UAV flyers will be able to make use of (i.e. associated hardware will be cost/mass/volume wise within the grasp of amatuer UAV users), will be realised when Galileo is launched, and manufacturers start producing and retailing hardware to replace GPS units.

    With the market for nav hardware at the consumer level in all its forms now so well developed and established, I suspect "Moores Law" will kick in, both in terms of development and price drop, a lot lot faster for Galileo hardware/software products than it did for consumer level GPS products.
  • Tom Yochum August 6, 2010 at 8:24am
    RLG's are pretty complex. The "cheaper" version are Fiber Optic Gyros (FOGs). However, the trick with these is you need to wind a long distance of fiber on as small a spool as possible. Because you can't bend fiber beyond a certain radius, you end up with something orders of magnitude larger than a MEMS chip. But the performance is amazing! A bit overkill for an AHRS, but for GPS/INS type applications it would be great.
  • Bill Porter August 5, 2010 at 8:58pm
    Also, don't forget the gyro is only half the dead reckoning equation. If your linear motion tracking isn't good who cares about how well you can measure rotation. How would you purpose to have good linear motion tracking?
  • Miles August 5, 2010 at 8:25pm
    I thought they could be used. If used successfully say 3 or 4 units the accuracy would be far better than GPS and would allow GPS to become a secondary back up navigation.

    Then we only need to brief up the processing power of the autopilot. How about GPS processors with Ring laser Gyro, now that make a autopilot!
  • Bill Porter August 5, 2010 at 6:29pm
    There are Laser Ring Gyro's in the Unmanned Underwater Vehicles I use at work. The accuracy is awesome (to the point I can't tell you exactly how awesome) but if any consumer product comes close it would be cool. Although they are very heavy, either the weight of the mirror, or piles of fiber. Could they really scale to the weight acceptable for UAVs?
  • Garry Qualls August 5, 2010 at 6:20pm
    Yes, ring laser gyros are just really good gyros. Most vehicles end up using four to get a complete solution and have redundancy in case one of the four fails. I hear cheap ring laser gyros are made from coils of fiber optic cable, so DIY versions may not be as far away as you might think.

    Garry
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