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Cold IMU calibration issue ... again.

Discussion in 'Inspire 1 Discussion' started by Dobmatt, Jun 4, 2016.

  1. Dobmatt

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    I know, the procedure of successful IMU calibration was explained and discussed countless times here, but what is the reasoning for chilling the drone just before that? Can anybody scientifically explain the mechanism of it?
     
  2. Alastair

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    I've heard of people putting the RC in the fridge but I don't think they mean "cold" literally. They just mean it should be done right after startup. I usually have the RC on, with the app running on the calibration page. Then, turn on the AC and start the calibration. If the AC has been running already, shut it off for 20 minutes or so, before doing it. I don't know the reason why it has to be "cold". Over to you Editor!
     
  3. DesertWindAero

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    I've never heard of putting any drone in a refrigerator for any reason.

    From an April 16 post from The Editor,

    "...Calibrate your IMU first on a cold machine - that is one that has sat on the table for half hour or so to totally cool down the IMU which is internal to the flight controller. Turn the Inspire on (with gimbal in place) and as soon as the aircraft has initialised and the gimbal has done its startup sequence immediately go into the IMU calibration screen and run the calibration. Once this is done, then go outside and calibrate your compass."
     
    Alastair likes this.
  4. filmscum

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    They actually do mean cold as in temperature. From what I understand the IMU begins to heat up the second the craft is powered on, doing a cold calibration will greatly reduce warmup times. During the IMU calibration, the craft is collecting data at various temperatures about it's IMU sensors. If it has data from a relatively cool point, in the future it will be able to "warm up" faster. If you calibrate it while the craft is warm (just after a flight), it will have to return to that temperature during the "warm up" and will therefore take a much longer warm up time.

    MadAngler did a great video on this

     
  5. The Editor

    The Editor Moderator
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    My work here is done. :p

    What everyone above said!
     
  6. DesertWindAero

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    With all due respect, I believe that if DJI engineered their products to that level of exacting process in order for it to fly correctly, they would have put the process into their manuals.

    This comes across to me as just so much unnecessary effort.

    I mean really...all this will do, according to this expert, is reduce the time needed to take off and fly. I would suspect that if the cold treatment does, in fact, reduce that time, it would come to fractions of seconds and would not detract from the overall effort to get flying after turning on the battery.

    So, again...unnecessary as far as I can tell.
     
    #6 DesertWindAero, Jun 5, 2016
    Last edited: Jun 5, 2016
  7. The Editor

    The Editor Moderator
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    Cold as in the aircraft standing for half an hour or so is fine.
    The difference between ready to fly on a cold calibrated IMU v a 'warm' IMU can be up to 2 minutes!
     
  8. Dobmatt

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    That's exactly what I'm worrying about. By far nobody was able to come up with scientifically supported explanation of "cold" IMU calibration procedure. Somebody, long time ago, discovered this way of calibration, and most of us blindly follows the recipe. We all know that the procedure eliminates annoying (for some) "warming up" statement on Go app screen, but what it really does to somehow crucial calibrating process? Aren't we messing with IMU calibration for this stupid 2 minutes of waiting before first flight? Perhaps sensors really need warming in order to work properly?
     
  9. filmscum

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    Desert and Dobmatt I'm agreeing with the editor. Don't do it and fly. I did it back in December and have had zero issues. It's much more than fractions of a second by the way. Do what's best for you and have fun!
     
  10. The Editor

    The Editor Moderator
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    How often are you guys calibrating your IMU to be worried about this?
    If I was still running the original firmware my IMU would have been calibrated over 18 months ago and that would be it!
    The IMU is almost a 'set it and forget it' practice (although ALWAYS check mod values prior to take off).
    There is absolutely no need to do an IMU calibration unless the mods values are out or the aircraft has been subjected to some sort of physical shock.
    It is good practice to do one after a firmware update - although not absolutely necessary then, DJI have been so flakey in their code writing that changing algorithms may or may not have a detrimental affect on how the aircraft flies so doing an IMU calibration (on a cold machine) after an update gives a base reference for the new firmware. May not be necessary, but I and many others do this.
     
  11. Dobmatt

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    About every 2-3 weeks, Sir. It's roughly that much time between FW updates :D...
    BTW, the mechanism of "chilled" IMU calibration remains a mystery...