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New or old, calibrate that IMU, help prevent fly a ways

Discussion in 'Phantom 2 Vision + Discussion' started by RoyVa, Jul 24, 2015.

  1. RoyVa

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    Many of us have heard about the dreaded fly a ways. One way to help prevent them is through calibrations. A lot of controversy over what causes them. But I can guarantee you one thing a proper IMU calibration will help prevent some of them. What is an IMU you say. Inertial Measurment Unit is the brains of the quad when it comes to a collection of the sensors and is typically comprised of at least a three-axis accelerometer and a 3-axis gyroscope and employes magnetometers (compass), barometers and other sensor to determine the angular position or attitude of the quadcopter. Basically it's location, direction and altitude at any determined time. Remove any one of the sensors information and you can have a fly a way.
    IMU information is data and data can be corrupted. Sensors can be disoriented. How you say, the main way is by rough handling (shipping), hard landings, crashes and changes to the sensors and compass. These quads are shipped all over the world and are roughly handled so new out of the
    box they need to be re-calibrated and have fresh data at their new home. After being sent out for repairs and shipped back to you the same is needed. DJI even sends you a email telling you to re-calibrate. Calibration is also needed after a major firmware update. New data is introduced.
    Calibration of the IMU must be done with the Quadcopter perfectly level from back to back and side to side. Easy way is to put a piece of glass, cutting board or simular flat panel on top of the quad covering the 4 motors spindles and then using a level front to back, side to side, and diagonally. Placing spacers or paper where needed under the legs to get her perfectly level. Then power up the assistant and the quad and fairly quickly do the advanced IMU calibration. This needs to be done before the main controller gets to warm from no airflow or you may get a to warm message. If it pops right up ignore it. But if the quad had be on for more that 5-10 minutes it may be legit and you'll need to shut down and cool her off for half an hour or so. A clean IMU calibration will only take 5-10 minutes at the most. When completed and after going outside do a compass calibration. When these are completed your quad should now have good data. The Roll, Pitch and Yall of the quad,as controlled by the changes in the motor speeds, will have good and proper orentation around the 3-axis as necessary for input from GPS and compass direction to let her know where she is, where she took off from, and how to get back, as long as you acquire the proper number of satellites and get home lock at take off. When you hover you should see a nice stable hovering quad with minimal drift and have good control of your unit. So when in doubt from a crash or hard landing, do your self a favor and re-calibrate. Do it after having shipped your unit or if it has seen rough handling. Less reduce the fly a ways! CALIBRATE !!!! Some have been lucky and have not done the IMU calibration. The old if it ain't broke don't fix it... Doesn't apply if you don't do the IMU then it may get broke. Don't listen to me ask the experts about IMU calibration. Search google and or you tube. The info is available.
     
    #1 RoyVa, Jul 24, 2015
    Last edited: Jul 25, 2015
  2. Tallyrver

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    Great information!
     
  3. ilovecoffee

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    Honestly I've never done a calibration after over 100 flights and 2 crashes lol. One was due to a bad compass calibration. The other, n00b pilot error.

    Given that I've never witnessed anything wonky while flying, I'd be hesitant to mess with it if it works. If it ain't broke...
     
  4. N017RW

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    Same here ilc,

    For me it's been 3 times in ~18mos.
    >Out-of-box
    >New Firmware (twice)

    Many people take off and hover for a bit testing stability, control response, listening to it, etc.
    Absent a new f/w load, trauma, or changes to the quad physically or mechanically (mods.) this is a more pragmatic way to determine if cal is necessary.


    No fly-aways BTW.
     
  5. pstockton

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    Nice post - did an IMU calibration last night as it's had 15-20 flights since new and was suffering a slight horizon tilt. Also, my last flight the camera kept flicking to the left as it was RTH and also suffering the Gimbal Overload messages.

    I'll be taking it out tonight or this weekend to see if issues are resolved or improved
     
  6. pstockton

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    Is the compass calibration not part of the P3 IMU calibration or is there a separate compass calibration I couldn't see?
    Can see compass figure on the IMU screen so figured it was part of this
     
  7. flight2

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    Thank for the info. Any negative effects reported after calibration?
     
  8. RoyVa

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    No, the IMU calibration normally settles any drifting or erattic flight issues.
     
    Genghis likes this.
  9. jryser

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    I did the IMU yesterday - had a very minor horizon issue. Anyway the p3p was perfect every other way. But I went ahead and did the IMU calibration. Did NOT refrigerate as some folks say! I did put it and the battery on the AC for a few cycles. Anyway it took 6 minutes - did a gimbal calibration after, calibrated the RC, and it flew even better today. Zero warmup time now. No problem with the horizon. Rock steady in the air. Good post and rationale.


    Sent from my PT beating heart
     
  10. WildEMT

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    This was more-than-enough to get me to do one on mine. The program recommended it being done when I checked the status.

    I didn't refrigerate or anything. It's only 65* in the house here. I fired it up from a half day of rest. It still gave me a temp warning, but I ignored it and went ahead. The calibration was done within a couple-three minutes.

    I suspect I probably should reset my BTU next time I have it hooked up to the laptop.
     
  11. Frogbone

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    Is this something that should be done after you travel to a different continent / country?
    Might be a stupid question but given that his is so complex I wanna know so I don't have surprises when I travel....
     
  12. RoyVa

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    It is really going to depend on the shipping. If it handled carefully I would think your IMU calibration would be ok. If the quad is rough handled, thrown into the hold of an aircraft or shipped via a carrier then I would definitely do the compass calibration at destination. Get satellite lock and home lock and do a few short flight test to be sure there are no problems. If it acts erratic or drifts a lot then you may need to do the IMU. If it hovers steady and looks and controls well then you should be ok. Hope this helps.
     
  13. sergekouper

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    Never recalibrated the IMU, but what do I know huh... ;)
     
  14. SouthernPhantom

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    As long as the unit is significantly cooler just before the IMU celebration than where you'll fly it, it doesn't matter how it gets that way. I am one of those refrigerator fans, but only because my moderately air-conditioned apartment has no cold spaces. None. My P3 had 5-10 minute warm-up times. Now, it always works perfectly and flies beautifully! After September, when the 80-90-degree Atlanta temps drop into the 60's at night, I'll place it on the balcony first! And yes, I located an absolutely level spot by using a carpenter's level. It's amazing how occasional calibrations do help! :)
     
  15. RoyVa

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    Yep just like NASCAR race engineers hooking those laptops to their cars to fine tune them and get the best performance and hopefully don't get any run away engines. They are calibrating the sensors and computer for the best performance and operation. Sound familiar doesn't it.