Welcome to PhantomPilots.com

Sign up for a weekly email of the latest drone news & information

IMU Calibration

Discussion in 'Pro/Adv Discussion' started by 2k3sgm, May 13, 2015.

  1. 2k3sgm

    Joined:
    Apr 27, 2015
    Messages:
    117
    Likes Received:
    34
    So I did the IMU cal to get the camera back into alignment. Up until then when I started the P3V it started up normal. Since the IMU cal I get the "warming up" warning. Has anyone else experienced this after an IMU cal?
     
  2. bbfpv

    Joined:
    Feb 3, 2015
    Messages:
    3,751
    Likes Received:
    1,093
    Location:
    Long Island, NY
    What was the ambient temperature at the time you did the calibration?
     
  3. KillerCut

    Joined:
    Apr 9, 2015
    Messages:
    134
    Likes Received:
    33
    I usually have to wait 60 seconds each time I fly for imu warm up. Maybe I shouldn't have done imu cal out of the box. It was probably 5-10 degrees cooler outside when I went flying. It was done at home at 75deg...
     
  4. 2k3sgm

    Joined:
    Apr 27, 2015
    Messages:
    117
    Likes Received:
    34
    70*, it was done in the kitchen on the counter, only thing in my house that seem to be dead balls level!
     
  5. KillerCut

    Joined:
    Apr 9, 2015
    Messages:
    134
    Likes Received:
    33
    Same here, kitchen counter, guess we need to do it outside or something
     
  6. bbfpv

    Joined:
    Feb 3, 2015
    Messages:
    3,751
    Likes Received:
    1,093
    Location:
    Long Island, NY
    According to Blade over on RCGroups:

    Originally Posted by blade strike [​IMG]
    I have about a 20-30 sec warm up.
    Try this, cool the bird down as best as you can, maybe wait for night. Then bring it in and immediately do an advance imu cal. It will take a little longer but will give you a better temp range for the sensors. You wont have to wait as long for it to warm up to the correct operating range since you will have calibration data for the lower temp.
     
  7. KillerCut

    Joined:
    Apr 9, 2015
    Messages:
    134
    Likes Received:
    33
    Guess I should put it in the fridge next time I do imu cal, lol.

    Should I close the door and do imu cal with it inside? Or cool it and then do imu cal before it warms up outside the fridge?
     
  8. 2k3sgm

    Joined:
    Apr 27, 2015
    Messages:
    117
    Likes Received:
    34
    Well I guess since it's all of 43* today I just need to find a level surface outside in the parking lot at work and do it again.
     
  9. bbfpv

    Joined:
    Feb 3, 2015
    Messages:
    3,751
    Likes Received:
    1,093
    Location:
    Long Island, NY
    The latter. Who knows what kind of condensation can build up when it's inside a refrigerator!
     
  10. Tj1627

    Joined:
    Apr 27, 2015
    Messages:
    33
    Likes Received:
    20
    Location:
    Chicago
    During the cal process, the phantom has an internal heater that will heat it to the max temp. So if you start the imu cal at (making up numbers here) 25 deg c and the max temp is 50 deg c (again, made up numbers here), then the imu cal has accurate data from 25-50 deg c.

    If you do an imu cal when it is already hot, 45 deg c let's say, then it'll warm to 50 deg c (remember, made up #s), and then you'll only have accurate data from 45-50 deg c.

    So what does this mean when you fly? The phantom starts warming up (literally using its internal heater. This is a physical warm up) to the range it was calibrated in. Calibrate it across a wider range (25-50) and when you fly in 20 deg c weather, it only has to warm up 5 degrees. That should be 20-30 seconds or so. But if you calibrated it in the 45-50 degree range, then it needs to warm up 25 degrees. That'll take longer. Maybe up to 2-3 minutes? Not sure.

    It'd be interesting to learn what the minimum temp is so that we can do the calibration across the full range of operable temps. I'm sure it's in the docs somewhere, I just haven't looked yet. Maybe after I get some coffee ;-)
     
  11. 2k3sgm

    Joined:
    Apr 27, 2015
    Messages:
    117
    Likes Received:
    34
    So would it be logical to think that if you calibrate with a narrow temp range as TJ states the sensors might not be so accurate once air born and at altitude? The air up there tends to be quite cooler.
     
  12. bbfpv

    Joined:
    Feb 3, 2015
    Messages:
    3,751
    Likes Received:
    1,093
    Location:
    Long Island, NY
    Theoretically you'd want it calibrated for the whole temp range, so starting it when it's cool is probably a good bet. I'll wait for confirmation, since I've not had to calibrate and have had no issues flying even at height.
     
  13. leekiya

    Joined:
    Aug 29, 2014
    Messages:
    1,103
    Likes Received:
    145
    Location:
    Lee. UK
    This makes a lot of sense with my first 3 flights today, it must have been 3 mins for my IMU to warm up on my first flight this morning (730am uk so pretty cold). My craft was on for a good while the other night and would have been very warm when i did the advanced IMU calibration as it was one of the last things i did while messing about with settings. So i will stick it in the garden later tonight for a bit when its cold and then bring it back in a do another, then see if it warms up quicker on tomorrow mornings flight which i guess it will.
     
  14. bbfpv

    Joined:
    Feb 3, 2015
    Messages:
    3,751
    Likes Received:
    1,093
    Location:
    Long Island, NY
    What's your address? :p
     
    leekiya likes this.
  15. leekiya

    Joined:
    Aug 29, 2014
    Messages:
    1,103
    Likes Received:
    145
    Location:
    Lee. UK
    I would like to say the dog would be straight out there if he heard anyone, but if i didn't lock him in the house while it was back there he would eat it. Then i would probably be the first posting " Dog Chews up P3". :D
     
  16. bbfpv

    Joined:
    Feb 3, 2015
    Messages:
    3,751
    Likes Received:
    1,093
    Location:
    Long Island, NY
    and blaming it on DJI for not making the Phantom canine resistant
     
    2k3sgm likes this.
  17. leekiya

    Joined:
    Aug 29, 2014
    Messages:
    1,103
    Likes Received:
    145
    Location:
    Lee. UK
    I did the cold calibration late last night, and this morning on my first flight the IMU only took 42 secs to warm up, instead of the 2 to 3 mins it was taking yesterday. Very pleased
     
  18. bbfpv

    Joined:
    Feb 3, 2015
    Messages:
    3,751
    Likes Received:
    1,093
    Location:
    Long Island, NY
    Glad it worked out.
     
  19. mmccurdy

    Joined:
    Jan 26, 2014
    Messages:
    103
    Likes Received:
    22
    So how does this affect those of us living in warmer / humid climates?
     
  20. KillerCut

    Joined:
    Apr 9, 2015
    Messages:
    134
    Likes Received:
    33
    Had mine in the fridge for 10 min, startup took like 10 seconds this time, yay.