Hi All,

I have flown my quad 12 times now, using the stock pid param as per 3.2.1

I get ~25min per flight with small HD Tube nose-mounted FPV cam.

I now want to attempt Auto-tune to optimize the rig.

 I don't think I am experienced enough to do PID tuning manually.

However, I read somewhere around that Auto-tune can fail on bigger, heavier quads, with low kv motors.

My build is based on the Tarot 650 Sport Quad Frame (X-config)

FC - PixHawk (3.2.1)

Motors - Tarot 4114  320kv    

Props - CF 1550

ESC - HobbyWing Xrotor 40A

Batt - 8AH 6S

AUW : 3kg

1) I would like to know if Auto-tune can be done successfully on this build.

2) Do you recommend that I first upgrade to 3.3.3

Thank you for your valuable comments.

Regards,

Gerhard

Cape Town, South Africa

T650Q6S8000_1.jpg

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Replies

  • try setting AUTOTUNE_AGGR to 0.1 (instead of 0.05)

  • Did you have to change your throttle gains much to get alt-hold to work?

    I am having similar problem with two different vehicles(110kv(4kg) and 360kv(2kg)) with pretty much identical problems. When I switch to alt-hold the vehicle drops couple meters instantly(as motors practically turn off) - I have not stayed in alt-hold mode long enough to know if it would steady out. Once the motors stop the vehicle pitches over too so its not very easy to test. I can attach logs but on one vehicle I checked Vibration and it was way within bounds. I also set the throttle mid to be correct hover level. Not sure what else to change. Any tips would be appreciated. 

    • Hi Steve,

      Quad's Thr Mid setting hover is @ 400,  see attached pic.

      Prior to Atun, with bad vibration, I had the same experience that, when changing from eg AltH to Stblz,

      the vehicle would loose Altitude sharply, had to Thr-up to get it on level again.  Once the vibration was resolved, with ATun, I find now that changing FM from eg AltH > Stblz (Thr was at Radio mid-point setting during FM Change) the vehicle would in fact climb, such that I have to Thr-down a little, to get it on level. Same with changing from PosH > Stblz. This behaviour is however exceptable to me.   Changing FM from AltH to PosH and back, does not in my case result in an large step Alt-change, such that I have to use the Thr stick. 

      I am really not experienced at all to offer sage advice, however these are the basic points

      that I have focused on, apart from the normal model Mandatory Init
      Config and Extended Config etc,  which I recon that you have done as well -

      1) Radio TX sticks centred.

      2) ESC's Calibrated for your ESC's brand/model.

      3) Vibration within acceptable levels.

      4) Set Thr Mid point for Hover in FM Stblz (mine @ 400)

           I assume you followed this How TO ?  >>http://ardupilot.org/copter/docs/ac_throttlemid.html

      5) AutoTune to satisfaction.

      I hope this helps?

      Regards,

      Gerhard

      Throttle Hover.JPG

      Setting Hover Throttle — Copter documentation
    • Ouch that sounds pretty bad.  I've seen alt-hold do that but on a much smaller scale - a momentary dip in throttle but almost instantly recovers, but haven't seen it on smaller higher kv craft.  You might want to ask here:

      http://discuss.ardupilot.org/c/arducopter/3-3

      As that's a more active support forum than here.

    • The single problem I have is that the quad is loosing altitude with forward flight, even in alt hold mode. Even the slightest forward flight will result in 30-40cm altitude loss... Once it stops it will climb back to the original altitude... It is very disappointing.

      • That's a completely separate known issue, it's to do with aerodynamic low pressure bubble in front of the craft in forward flight fooling the barometer to think it's higher than it is, so the FC compensates by lowering altitude.  When you stop the low pressure bubble equalises and the FC compensates by raising altitude again.  It's essentially a physical design 'flaw' that most multirotors have, there has been various discussion on how to fix it with static ports, software fudges etc, but I don't think anything concrete has been put in place yet unfortunately.

  • Hello, I've done an auto tune on almost the same setup, the quad became a little bit under tuned. I have even try lower KV motors too, those one became over-tuned. Good luck! 

  • Hi All,

    Just an update -

    Friday was an excellent day here in Cape Town, Bloubergstrand, to do flying.

    Good Vis, hardly a breeze.

    I finally took the plunge, went to a local open lawn-area and executed Auto-tune.

    It worked!!    AutoTune:Success   :)))))

    I saved a copy of the param-settings prior to ATun, such to compare the ATun results, quite a difference.

    ATun was configured for  R&P&Yaw axes.

    My observation was that it took about 18 min to complete, then again, I had to re-position the vehicle  a few times.

    After saving the ATun params, I tested in stblz, alth, posh, the vehicle 'felt'  good, compared to pre-ATun.  Unfortunately I only had  about 6 min.

    Once again, thanks to everybody who provided positive comments, suggestions and pure sound advice based on

    your experience. Your input built-up my confidence to take this plunge. Yes, I know it is actually small steps, in the bigger picture, but for me starting out with this hobby it is gaining quite a bit of ground getting towards my better understanding of the environment, ultimately to enjoy the hobby.

    It seems to be a great day again for flying, so I am going see how the vehicle responds.

    Regards,

    Gerhard

    • Well done Gerhard, happy flying :)

      Most people seem to get better results when doing at least 2 or three autotunes - if it has a better starting place it ends to get a better end result, and the subsequent autotunes are much quicker, at least that's what I found.

  • Hi All,

    I finally completed upgrading / installing FW 3.3.3.

    I did the first flight with new FW today.  Wind : Bit warble breezy  Duration : 20min to BattLow FS (set at 22V)

    Prior to flight, in MP I did the actions > pre-flight calb

       btw, are there other pre-flight calb which should be done prior to flight?

        (I am not referring to basic pre-flight inspection eg gps lock, mechanical sound)

    Tested FM : Stblz, Alt_H, Pos_H 

    In Alt_H I made some aggressive R&P stick movements, the Craft seemed to respond 'ok' 

    I had a look at the DF bin file -

    The 'Vibes' are within the spec as per  http://ardupilot.org/copter/docs/common-measuring-vibration.html

    The R&P seems to follow the des R&P, from what I see in the graphs.

    GPS R Atl / Alt Baro Alt, AHR2 Alt follows each other, however there is an 'offset' from each other.

    See attached files.  I am not sure how to interpret it?

    The .bin file is ~13M, too big to load here.

     How else can I share the file?

       Perhaps I should do a short ~5min flight in AltH hover, smaller file?

    Thank you once again for your comments, observations and suggestions.

    Without it, I will not be able to optimize the Craft in order to further explore and enjoy this hobby.

    Next step -

    Await a calm no-wind day, then fly it in an open park area, at this time I am flying at home in my backyard.

    Regards,

    Gerhard

    Vibe XY zoomed.jpg

    Vibe XYZ.jpg

    GPS Alti.jpg

    Measuring Vibration — Copter documentation
This reply was deleted.

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