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hank.su1968

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Misalignment in yaw direction for long term PH

by hank.su1968 » Tue Feb 23, 2016 4:30 am

Dear all:
Can some one help point out where my problem is? I have completed 6 point sensor calibration, autotune , PID, .. etc. In the Attitude/ filter setting, I use INSoutdoor for Attitude and INS for Navigation. The PH I did was always good at begining, but later my quad copter will start rotating certain degree, therefore I found the quad had turned into face the true North. This is really confused me.
Could this be any problem caused by my Neo-M7N gps? I am sure most of the time it has 8~10 satellites locked, so I am not sure if it is wherther or not the problem due to satellite number.
In the system / vtolPathFollowerSetting / YawMode, I selected AxisLock. It should lock my quad copter in the direction where I want.
Can someone help or teach me to solve the problem.

Thanks in advance...
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pug398

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Re: Misalignment in yaw direction for long term PH

by pug398 » Tue Feb 23, 2016 6:00 pm

What is the PID setting for yaw on Stabilization tab? Best to try attitude filter of both INSOutdoors and Complimentary to see which one best serves you. I generally stick with complimentary.
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peabody124

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Re: Misalignment in yaw direction for long term PH

by peabody124 » Tue Feb 23, 2016 7:11 pm

I'm not following you when you say it has turned to face true north? When in position hold mode, you can still yaw with the yaw stick. Are you saying it simply turned, or you started getting toilet bowl behavior implying the absolute yaw inference is wrong?
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hank.su1968

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Re: Misalignment in yaw direction for long term PH

by hank.su1968 » Tue Feb 23, 2016 9:54 pm

First, thanks all your reply.

- The PID setting is completed using autotune because honestly I don't really know what standard procedure is to tune PID.
- For INSOutdoors and Complimentary, I try them both before. The complementary mode has more damping in vertical direction than the insoutdoors, for I am not sure if the poor barometer on the chinese clone board has led to the problem.
- For turned to face true north, I have to check it again if it is coincidence or not. The yaw stick will move back to center automatically after I release. The throttle control and LoiterAllowAltControl all set in "True".
- Probably, it could be one of toilet bowl behavior. I don't know what difference is between "major" or "minor" of toilet bowl problem. The altitude of my quad copter was held except slightly up/down damping, but the quad copter will lose fix in yaw.
Should I go to System/ Vtol.../YawMode and set Attitude instead of AxisLock or not? I saw people using "magnetmot" to check magnetic interference for their pixhawk FCs. Does anyone have the same problem before? I think I will try to use Neo-M8N to compare with Neo-M7N to clear if the less satellite numbers will result in distortion problem in Yaw.

Thanks you all, again...
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netwalker

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Re: Misalignment in yaw direction for long term PH

by netwalker » Wed Feb 24, 2016 7:51 am

Sounds like you are having an issue getting your magnetometer calibrated correctly. For me it seems best if you do all steps of the 6 point calibration facing either east or west. Also, make sure that the wizard spits out magnetometer numbers in the window on the calibration screen when you are done. I've had 6-point calibration hang on the last few steps (forcing me to close the program), and commonly say that the magnetometer calibration failed (in the window where the results are displayed). I would also recommend you use "complementary" attitude unless you really know what your doing.

Once you get a successful calibration, then leave the quad sit for a few minutes and hopefully the HSI will slowly slew to align with the actual magnetic heading it is facing. If not, do the 6 point calibration again. Rinse and repeat until it aligns.

I've also had much better luck with the on-board magnetometer on the Sparky 2 than the magnetometer on that M7N, but I think it may be more of an issue with compatibility vs quality.
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hank.su1968

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Re: Misalignment in yaw direction for long term PH

by hank.su1968 » Wed Feb 24, 2016 2:35 pm

Thanks very much, netwalker.

I will pay more attention for doing 6 point calibration and check if any magnetic interference
for the magnetometer on my sparky.


Thanks, again.
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pug398

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Re: Misalignment in yaw direction for long term PH

by pug398 » Wed Feb 24, 2016 3:45 pm

Autotune does not currently tune yaw PID. I do not know what yaw PID you have but defaults are sometimes not high enough to maintain a solid lock. You might try 60/100/0 to see if it makes any difference.
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hank.su1968

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Re: Misalignment in yaw direction for long term PH

by hank.su1968 » Thu Feb 25, 2016 12:22 am

Thanks very much, all you are professional.

I will try tune Kp and Ki for Yaw.
I have also heard some RC players mentioned an " axis-lock" problem in yaw about CC3D FC.



Thanks, again.

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