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IMU Calibration issue

Discussion in 'Inspire 1 Discussion' started by ppdrone, Jan 10, 2015.

  1. ppdrone

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    So I read on facebook pages that it is advised to do an IMU calibration.

    I just got the I1 yesterday. Did all the firmware updates, etc.
    Today was the day to take it out for the first few short flights.
    All batteries charged and I1 nicely sitting in the DJI case.

    Take it to the car, drove literally a few minutes to the location close to my house.
    Got the I1 out of the case and on the road.
    Battery in, remote on, I1 on....out of travel mode. All components off.
    Props on, turn the whole system on again. Bear with me...
    Compas calibration done!
    Next up IMU calibration.
    Watched the video on youtube and followed the same steps. Went for the Advance option.
    Pressed the key and red letters came on my screen saying something like this:
    Inspire/battery overheated, please turn off and wait for 5 minutes and try again.

    It was 45F....so not warm. I literally had the battery on for maybe 2 minutes...I think even less....
    Overheating!

    I restered the system, and went for simpler IMU calibration and got the message that all is OK.

    Did a few flight without any issues...got 13 minutes out of the first battery and packed it up at about 25% left.

    Posted this on Facebook also and someone suggested I talk to DJI online support which I did.

    They weren't too concerned...

    What I dont get, and I really haven't received a logical explanation...how can a battery overheat after 2 minutes being on...

    Anyway....just FYI...
     
  2. Ultra310x

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    imu over heated not the battery. you should insure its actually calibrated took me a few times press the check calibration button.
     
  3. shockwave199

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    Is it actually standard practice to have to do an IMU calibration on site all the time? Can't this be done indoors in a controlled setting and then not really have to do it again? I've heard of two times you should advance calibrate- before your very first flight and after a firmware update. And I haven't heard, and certainly hope you don't have to include IMU calibration outside...frequently.
     
  4. Ultra310x

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    So I just checked my IMU again after a few flights and it says calibration needed again so I did it. advanced cal only goes to 97% then it runs the basic cal on its own and completes . but I don't get it why so often? I just did this before the first flight. is this something we are going to have to do every flight now ? or is there a bigger issue confused
     
  5. ppdrone

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    i was told not to do it every time I want to fly....
     
  6. Ultra310x

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    By who ? and why ? whats the source of info ? thanks
     
  7. The Editor

    The Editor Moderator
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    No you DO NOT need to do an IMU calibration every time you fly - would you go and get a wheel alignment done on your car every time you wanted to drive to the grocery store?

    An IMU calibration is simply calibrating or resetting if your like the internal accelerometers/gyros to a 'status quo' or null/reset state.

    It is good practice to check you mod values every time you fly.

    The last time I did (but didn't HAVE to) do a full calibration was probably around 10 months ago. I only did it because I like my mod values as close to zero or 1 as I can get them.

    To do an IMU calibration everytime you go out to fly is overkill IMO and runs the risk of introducing an error if done in the field on a non level surface.

    Compass calibration is different as there are external variables, magnetic declination depending on location in the world and local forces, but again, although I check my compass raw values the last time I did a 'compass dance' was probably over six months ago.
     
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  8. ppdrone

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    By DJI on line chat person...
     
  9. Tahoe Ed

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    My take on IMU calibration. I do it every time I do an update. There appears to be an issue with the IMU calibration on the Inspire. I would recommend that you check the IMU Mod values prior to launch. If they are out of standards then I would calibrate, at home, at the field, where ever. It does not matter as long as the surface is perfectly level and away from interference.
     
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  10. lrwskyfilms

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    Updates all OK, but now the IMU needs calibrating, do that OK, restart I1, RC and App and it says it needs calibrating again? What's going on here, anyone know? Cheers for any help, Mark
     
  11. lrwskyfilms

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    And yes the MODs are OK.
     
  12. GizaDog

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    Tahoe Ed - Any tips on doing this and what to look for?
     
  13. Quadpilot

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    If you're using iOS tablet with iOS8 running, turn off the app, then restart. To turn it off double tap the home button and swipe up off the page. That's the only way to really turn off an app. Otherwise it's always running in the back ground. Sorry if this is going over stuff you already did.
    That worked for me.

    Edit: What just occurred to me is that if you have been letting the Inspire run for awhile indoors, the IMU gets too hot. Let it cool off and then check again.
     
  14. lrwskyfilms

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    Thx again, it worked before the last firmware update, I'll try again. After being switched off for a hour or so, the ACC MOD's went from 1.00 +/- 0.01 to 0.97 after restarting the I1, bizarre. Now running an IMU calibration, it completes.
    It seems the basic and advanced IMU buttons have been removed leaving just one IMU calibration button, so maybe it doesn't need a calibration but only one button is there if you do. Anyone else notice the IMU basic and advanced buttons missing on the IOS app?

    Cheers again, Mark
     
  15. Quadpilot

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    Glad you pointed that out. I had not noticed it, although I thought I had done a cal after update. Strange :confused:
     
  16. slim.slamma

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    Gone
     
  17. lrwskyfilms

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    I have to say another prompt answer from DJI chat, yes only one IMU calibration button, it does mean it needs calibrating, it's just the button to start one if required. Excellent service, IHMO.
     
  18. aknauer

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    I am experiencing slight drift and position holding that is not rock solid.
    I have done an advanced IMU calibration and the MOD is spot on zero. acceleration MOD spot on 1g, compass around 1500.

    I have been building multi-rotors for the last four years, many right from scratch with Mikrokopter electronics. I know how important IMU calibration on a level plane is. This level has to be zero in relation to the rotor plane, and is very sensitive to small misalignments.
    With the retractable undercarriage there is an element of uncertainty that this calibration is still valid in the raised position. I was trying to calibrate with the legs raised and perfectly leveled across the the propeller tips, but since selective undercarriage operation is disabled, I would have to build a jig high off the ground to avoid trigerring gear lowering.

    Has anybody any further ideas on that?
     
  19. The Editor

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    I take it this drift isn't in P-GPS mode? That would be odd. So I assume it is in Atti. You make an interesting point with regards to the FC being possibly slightly out of true when landing gear is raised.
    Like you, I have designed and built many multi rotors from scratch and I have never been an 'IMU calibration junkie'. I prefer to get it right and then leave well alone unless mod values are out ocalibrated message presents itself.
    I have not experienced any drift and have only calibrated with gear down and then only twice.....once the day I unboxed the Inspire and once more when I upgraded the FW to .17.
    With regard to your drift problem, could you maybe shim the Inspire's legs in the opposite direction when you do the calibration. Only by a fraction (a few sheets of paper etc). The first time you do this will be a bit of trial an error until you get the shim value correct but then for future calibrations you will know what legs to shim and by how much?
     
  20. beatnik

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    What if you put tape over one of the ultrasonic emitters?