Weird AH and stability problem with MK FC 2.5 and BL Ctrl 3.0

Discussion in 'Electronics' started by Ozkan Erden, Apr 16, 2014.

  1. Ozkan Erden

    Ozkan Erden Distributor

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    Hello everybody,

    I'm facing a very strange problem; I will write the progress here. Any thoughts are welcome on this problem.

    The copter details:
    Avroto 3520 KV400 motors - 12N14P
    CineStar 8 frame and 16" Tiger props
    MK Flight Ctrl 2.5
    Double Quadro 2 XL PDB

    Before migrating to BL Ctrl 3.0, I was using 6S with Herkules III board and the copter was flying beautifully, very smooth. The only change was the ESCs.

    The first observation of the problem:
    After migrating to Double Quadro 2 XL PDB, the copter was not flying smoothly. It was shaking even in zero wind. I changed the gyro settings, but it didn't help. The motors weren't starting consistently, so I upgraded the all of the BL Ctrl 3.0 firmware to this one: http://www.mikrocontroller.com/files/upload/BL-Ctrl3_MEGA168_V1_02d_SVN799.hex

    The motors started to initiate properly with stock settings. But the copter was still vibrating, especially in wind.

    Altitude Hold was working inconsistenly. When AH is on and if I nick forward, the copter starts to rise very fast and becoming very unstable. When it's windy, AH doesn't work properly.

    I thought the FC is faulty, I got the new one and installed it. The problem still persist.

    * I changed the timing of the motors other than 24 (28, 18) to see if it would help, but it didn't help.
    * I tried 2.04 firmware and 2.06a firmware. It didn't help.
    * I put a heatshrink over the baro sensor, but it still has the problem. I covered the whole board with insulation tape to isolate it from the wind. But it didn't help either.
    * I checked two FC 2.5 controllers. They both have the same problem.
    I'm waiting an OktoXL Combi 3.0 PDB, which is on the way to try it also.

    I attached the GPX file. If you check the lines between 28-76, you will see the problem:
    * On line 28, I activate the AH. And then I nick forward.
    * As I nick forward you see the increase in altitude.
    * If you check the lines around 70, it gets back again to its original altitude while I don't touch any sticks.
    * If I cruise very very slowly, the AH works as it should.

    Here is the video of this problem:
    .
    You should watch it in full screen to see the change in altitude.

    The only different setting than the stock settings is ACC/Gyro Compenstation and it's set at 200. I reverted back it to default value, but again, still the same problem. Tried different Altitude P, Barometric D values, but no luck.

    I wrote this problem to MK.DE also.

    If anybody had the same problem, I'd like to hear the thoughts.

    Thanks.
     

    Attached Files:

  2. Dave King

    Dave King Well-Known Member

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    Ozkan

    This is a bit odd. I looked at your GPX file and at datapoint 36 you are at 12 feet altitude and at datapoint 41 you are at 24 feet altitude despite not giving it any gas input. Usually altitude hold is completely a function of the flight control board. Since you said you tried 2 different boards and the problem is still there I wonder if somehow the navigation/GPS electronics/cabling are affecting the operation of the FCB causing it to act crazy as far as AH goes. I couple things I would try just for the sake of trying to elilminate the issue is 1) fly it in manual mode and see if the altitude still changes. 2) Disconnect the GPS and Navigation boards and fly it manually and see if it has any affect. Have you checked the CG of the copter? I think if the CG wa severely off you could see issues like you are mentioning.

    Another thing that doesn't sound right is that you mentioned was that the copter was shaking which is not good. Even with all stock settings the copter should not be shaking. All signs of a flight control board not operating correctly. The odds of 2 different FCB's being bad with the same issue is highly unlikekly.
     
  3. Ozkan Erden

    Ozkan Erden Distributor

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    Hello Dave,

    Thanks for the input.

    * The copter flies without any erratic behaviour on manual mode. It flies expectable, controllable and keeps its line and height as long as you master the sticks on manual mode.

    * I also took off the Navi board off to see if it would react the same and the problem was still there.

    Today, there was no wind, the vibrations weren't there but that GPX file is from today.

    I will try the 3rd FC 2.5 board on Friday.
     
  4. Dave King

    Dave King Well-Known Member

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    Ozkan

    I am a little confused. If it flies good manually it should fly exactly the same way without the nav/gps because you are flying in manual mode.
     
  5. Ozkan Erden

    Ozkan Erden Distributor

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    Let me correct myself :)

    Navi/GPS is plugged in:
    * Flying manually OK
    * AH behaves weird
    * PH is working perfectly


    Navi/GPS is unplugged:
    * Flying manually OK
    * AH behaves weird
     
  6. Gary Haynes

    Gary Haynes Administrator
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    Sounds like a bad pressure sensor in on the FC board.
     
  7. Dave King

    Dave King Well-Known Member

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    When you changed out the flight control board are you calibrating the ACC and verifying its perfectly level? Did you make sure you calibrate the ACC after you did the firmware update? Did you delete the INI file after the firmware upgrade?
     
  8. Dave King

    Dave King Well-Known Member

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    Yeap, what are the odds of having 2 flight control boards with bad pressure sensors though? Weird issue.
     
  9. Ozkan Erden

    Ozkan Erden Distributor

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    The weird thing is, with Herkules III ESC, it was working without problems and two FC 2.5 boards act the same (one is totaly new).

    New Okto Combi PDB is arriving tomorrow. I will also try the third FC tomorrow, will not be able to wait for Friday :) With the third FC, I should eleminate one of the source.

    I got a message from Ingo, they are now on holiday, they will assist in this problem.

    My gut says, this problem is related with the PDB somehow, we will see how it will end up.
     
  10. Ozkan Erden

    Ozkan Erden Distributor

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    Yes, as a standard procedure, I always do ACC calibration, compass calibration and delete settings file on the SD card.

    There's no problem with the CoG btw. Everything perfectly level and balanced.
     
    Dave King likes this.
  11. Morgan Friedland

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    The music in your video makes it feel like an old Knight Rider show. Epic!
     
    Ozkan Erden likes this.
  12. Ozkan Erden

    Ozkan Erden Distributor

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    Here is an update regarding this issue:

    I setup totally a new CineStar 8 featuring MK FC 2.5, Okto XL Combi 3.0 Bl Ctrl and Tiger MN4014 motors with 16" props. All of the parts are brand new.

    It flew perfectly. That means, every component on this machine is working as it should.

    So, I took this beautifully working FC and put it to my weird machine, and it still has the AH problems!

    So, I've eleminated the FC as a source of the problem.

    Another note: On the new Okto XL Combi 3.0 PDB, I've also installed the new BL Ctrl firmware: http://www.mikrocontroller.com/files/upload/BL-Ctrl3_MEGA168_V1_02d_SVN799.hex So, both PDB has the same software on them.

    So I still believe, this is a Double Quadro2XL PDB issue but don't know how. I'm still waiting an answer on this matter from Germany.
     
  13. Dave King

    Dave King Well-Known Member

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    I didn't think that a 3rd one would cure it as the chances of 2 FCB's having the identical issue was like hitting the lottery. This is extremely strange. To me there's the radio, the receiver, and the flight control board. That's the signal change that affects altitude.
    Could the radio be engaging/disengaging AH and MK tools not reporting it or I wonder if there is somthing really odd about your radio that's sending intermittant gas control overrides that also is not reporting in MK tools? Have you tried using a different radio just to eliminate the problem? I can't see how the PDB is the issue because it just supples I2C info and power to the flight control board. Just thinking out loud...............
     
  14. Ozkan Erden

    Ozkan Erden Distributor

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    Hello Dave,

    Changing the reciever (tried two different Graupner GR-24) was also one of the things I've done for testing. And actually, I'm flying the copters with the same radio.

    My new motors, KDE 4014XF, also arrived, I'll also change the motors just in case.

    I will put the OktoXL Combi 3.0 PDB to this weird machine tomorrow. If that doesn't work, I am throwing out everything. :)
     
  15. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    This sounds more like an electrical interference/noise problem that two boards with the same issue -- plus the new boards work fine on the "non-weird" machine.

    I would start to ponder whether you've got problems with BEC, or the placement of wiring, etc. Anything that could create noise, etc.

    Can you (or have you already) swap out the cables between the various boards? They can cause really odd things to happen if they go rogue.

    Andy.
     
  16. Ozkan Erden

    Ozkan Erden Distributor

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    Hello Andy,

    As far as I know, the AH is not affected by the EMI. And another note, the kopter was flying perfectly stable with Herkules III PDB.

    Only two components left to try out:

    - Another BL 3.0 PDB
    - Another set of motors
    o_O
     
  17. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Ozkan: I doubt that the AH itself (that is the transducer) will be affected by EMI, but what about electrical noise to the boards -- that could be caused either by RFI or EMI. Alternatively, you may have a wiring/cable issue -- it's hard to explain why good boards go bad depending on which copter they're mounted without pondering what might be different about the environment, isn't it?

    Andy.
     
  18. Ozkan Erden

    Ozkan Erden Distributor

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    Here is another update:

    MK Germany responded this problem and they think the vibration dampeners could be too soft and they might be the source of the problem.
    Actually I'm using the same rubber and plastic standoffs which I always use on all MK systems. Since I'm tired of chasing the cause, I made more than one change at once this time:

    * Changed the motors to KDE 4014XF (Set the BL Ctrl timing to 28 and PWM start to 1 )
    * Updated the BL-Ctrl 3.0's firmware once again.
    * Changed the rubber standoff with a shorter one.

    The machine is now very stable, smooth and holds the altitude as expected

    I'm not sure, what solved this issue.

    I'll move the Avroto 3520's to 6S Hexa setup, I'll try them out there. We will see if the motors were the cause.

    Andy, the cables are organised at the same way as before, I think one of three things above solved this issue. ,

    Thanks everyone for the heads up, another weird machine is now acting as normal :)
     
  19. MIke Magee

    MIke Magee Active Member

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    Ozkan, where did you get the recommendations for the BL changes for the 4014's, and what version of the BL firmware are you at? MK didn't feel any parameter changes for the 4014's would be required when I asked them. Glad you got this sorted out.

    tx,m
     
  20. Ozkan Erden

    Ozkan Erden Distributor

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    Hello Mike,

    I found the settings by myself. For Tiger 4014 and KDE 4014XF, I'm using the same settings:

    Timing: 28
    PWM Start: 1 (2 also works but sometimes one of the motors stutter. With the value of 1, they don't do this)

    I tried different combinations and timings, these work best for me.
     
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