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Thread: Naza GPS yaw issue

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    Full Blown Hucker Bison52's Avatar
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    Naza GPS yaw issue

    Went out early this am in perfectly calm wind to test my GPS. Calm air is rare around here. GPS held a hover rock steady. Held position on climb and descent. Flew straight and then held on fore and aft flight and side to side.

    But (ain't there always a but), on even a small gentle yaw, would drift off severely before correcting. Slow quarter turn to the left and it would drift 8 or ten feet to the left before slowing and returning to position. Same to the other direction. When it did correct, seemed to hunt for position a bit before returning to new original hover.

    GPS lock is very solid. After I power on, by the time I step back and pick up tx, it has achieved 7 satellite lock.

    Tried changing gain for yaw to no effect. May try recalibrating compass later

    Anybody run into this yet?

    Mike

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    Full Blown Hucker
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    I have not. An A/P friend of mine saw my video of PH/GPS yaw at max rotation. His comment was, that's impressive, but show me how it works with a really slow yaw. I am going to experiment with that. I am running 130 for my yaw if that helps.

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    Full Blown Hucker Bison52's Avatar
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    Just wondering if there was any follow up. I went out today in a rare calm to very light wind day and flew some tests. In atti and GPS, hexa flew like it was on rails. Maybe a hint of the classic naza drift to the right but almost perfect atti hover. Perfectly steady on ascent to altitude in GPS and did well on descent.

    But still has yaw issue in GPS mode. Make a quarter turn yaw and craft will slide off about 8 - 10 feet before correcting and returning to original position. I've adjusted gains and they are solid. Holds altitude well. Checked x,y,z entries for GPS and even moved GPS but no joy. Compass calibration is good too.

    This is nothing I can't live with but it's so dialed in everywhere else that this kind of bugs me.

    Oh yeah. Attempted a fail safe return to home from about 150 yards out and it landed right at my feet. So cool.

    Mike

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    Pilot Extraordinaire
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    same here - I calibrated the compass and tried various settings - it seems to do it all the time. we have some gusty winds round here so it always needs to correct usually, I guess if it was 100% locked in the input would be too harsh ... I tested it today on our field and it even went for a circle with a diameter of nearly 20m at one time ...
    DJI Phantom 2
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    Full Blown Hucker Bison52's Avatar
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    What's odd is that it doesn't want to wander off until the yaw is completed. After the stick is moved to stop the yaw, it almost seems to hesitate for a moment, then wander off in pretty much a straight line. Then it slows and stops and heads back to where it belongs.

    I thought at first it might be going in the direction of the wind, that is, it was losing position lock during the yaw and getting blown downwind before correcting but I don't think that's it. Need to do some more experimenting.

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    Approaching Solo
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    I also have raised this issue in another forum but so far, no responses. I made a video of it here:

    http://www.youtube.com/watch?v=FrckYYC_Lf4&feature=plcp

    I wonder if it is the same mechanism which causes the well reported 'toilet bowl effect'; just a stationary version of it?

    (Apologies for the somewhat jerky video - YouTube did something to it!)

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    Pilot Extraordinaire
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    Have you guys tried rotating the GPS/Compass unit? See page 35 in the Naza manual. It relates to the problem you are describing. Try rotating the GPS unit opposite the direction you are seeing your MR fly.

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    Full Blown Hucker Bison52's Avatar
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    Ghost. I've done some experimenting there and I don't think that's it.

    http://www.multirotorforums.com/showthread.php?t=4422

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    Full Blown Hucker Bison52's Avatar
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    Kevin. That is exactly what mine is doing. Let's figure this out. I've always used 10" props. DJI and Graupner.

    What could be the difference between 8 and 10 props? Something about the torque difference? Rotating into prop wash?

    My copter is in the bench while I'm making some upgrades. As soon as I'm back in the air I might try a few things. Wonder if increasing the throttle slightly to cause a slight rise with yaw has any affect?

  10. #10
    Approaching Solo
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    OK so - some observations:

    • In my video, I yaw the quad clockwise in both cases (as seen from above) &, after the yawing is done, it drifts left/port (the lights are standard aircraft format: left/port = red, right/starboard = green. Front is white & the rear arms have the strobes)
    • In both cases, the yaw is approx. 180deg
    • In earlier tests, I have spun the quad on the spot & it doesnt drift until you stop yawing which is also your experience

    It will be interesting to try 90/270/360/360+ & see what happens - I may try that tomorrow.

    Other information:
    • On a quad, I assume yaw is achieved by slowing one pair of (same rotation) rotors & speeding the other (opposite rotation) pair - so overall lift remains constant
    • I also assume that lateral movement is achieved by slowing the rotor on one arm & speeding the rotor on the opposite arm, so that the quad tilts slightly but overall lift remains the same
    • One difference between 8" & 10" prop's is that the 10" will rotate slower for the same amount of lift (yes?) - assuming the pitch is the same

    So the drift behaviour could be for many reasons. For example, if the flight controller takes too long to update the left (or right) ESC after yawing, then the quad would tilt & drift. Etc.

    It would be interesting to see a DJI rep. pick up this thread & maybe provide some guidance about what we could test for them.

    Any thoughts?

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