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My quad is very weird, binary log attached

The conditions are as follows

  1. Firmware 4.0.7 Stable
  2. Main flight mode is Loiter
  3. 15inch prop
  4. Here1

Symptoms are as follows

  1. The quad’s altitude goes up and down at will.
    The throttle remained neutral, but his altitude changed at will.

  2. Although in loiter mode, the roll pitch continues to flow

  3. When the wind blows, the quad cannot hold up. About 3~4m/s
I have referenced these documents.

I did the usual setting.

I haven’t had any problems so far.

But this presents a big problem.

It is in loiter state but cannot hold properly.

Since posz_p is high, I’ve seen quads hunting.

But this is a little different.

The altitude is changing at will.

alt_source uses baro.

This shows a very good flight in stabilize mode.

But flying in loiter and alt hold scares me.

I upload my binary log here.

Please take a look

did you set the harmonic notch?
did you do and autotune in AltHold mode?

Use this spreadsheet to fix up a few of your parameters, pay close attention to the FLT parameters, “Suggested” ones and battery ones (that’s all of them I guess :slight_smile: )

Then I think you could try these for attitude control:

And these for starting the Harmonic Notch Filter process:

Then do a hover test in AltHold for about a minute or more. If it’s going OK just do a few gentle movements in pitch and roll, not radical. Post a link to that .bin log file. Make sure you are a couple of meters up away from the ground, stay out of the ground-effect.

I didn’t do both.
Even without doing two things so far, I have seen good flight performance.
However, this is the first time that the altitude changes arbitrarily, or the quad does not stay in one place and flows here and there.

Thank you for answer.

Does this only apply to althold?

Or if i modify those, will this get better flight performance on the loiter?

It will help all flight. AltHold test is for us to gather data for the Harmonic Notch filter configuration.
Once it is set up and working properly, Autotune will produce much better results.

Thank you.
I plan to fly out in about 3 hours.

Could you set up my flight scenario for acquiring flight data to pass on to you?

You asked for a simple hover, a gentle flight, but how many minutes will this last?

Additionally, I have never done autotune before.
Is this affected by the number of sat, gps 3d fix, or ofs, compass calibration, flight altitude, external wind, etc.?

Set the Fence parameters and the other parameters I gave you, then do the test flight.

I got the log.
There were several dangerous moments in flight.

When I tried auto tune, the quad moved crazy.

The quad does not stop at the end of the Rll and the pit, but moves to a strange place.

Rcmap messed up during Althold.

The flight at Stabilize is fine.

Could this be a GPS problem?
Or maybe it’s an FC problem?
Is it possible to solve it with parameters?

Dont run Autotune yet.

I see a lot of mode changes but I cant see how RCMAP would mess up. People sometimes think controls are messed up when they hit Simple mode by mistake. So sort out your radio and test it well before flying again. Use the MissionPlanner radio calibration screen to check every thing - you don’t need to run the calibrations, just watch the PWM values and green indicators.

Also Y axis vibrations are not good, yet X axis and Z axis are good. So look for a difference in the antivibration mounting, or something touching the flight controller, or wires pulled tight or vibrating against the flight controller.

Set this first:
then refresh parameters to see the rest of the HNOTCH params, then set these:
And now do another hover test and some gentle flying around in ALTHOLD - let us see that log file.
We’ll soon get to Autotune…

Thank you.
Where did you get this much information?

In particular, I am curious about the role of this parameter of HNTCH.
Are there any formulas for determining these values?

It’s all in the documentation, we learn by reading it thoroughly - it’s a long road sometimes.
I’ve determined those values from your last logs.
We will know more after your next test flight.

The quad crashed during flight.

This was out of control.

Hit the ground so quickly.

Fortunately, the quad’s frame is fine, but there is sand in the motor.
I think I will be able to fly more after cleaning this.

First of all, I’ll attach a short but a little log

Your Vibe levels are high with plenty of clipping events.

Also, there is something off about IMU2. Look at it compared to IMU1. Perhaps someone with one of these Mro FC’s can comment:

That’s annoying and sad.
Harmonic Notch Filter, the PIDs and other settings don’t cause that. Attitude control was reasonable up until the point where it went crazy - and previously you’d even been able to start Autotune.

I agree with Daves opinion that something is going on with IMU2. It seems to be much more affected by vibrations than IMU1. When you get this ready for flying again leave it powered on for quite some time to check messages. Do some very small test flights at low level to minimize damage in case it goes crazy again. If you’re not confident that it’s fixed by sorting out the vibrations (as per below) then you’ll have to replace the FC.
Looking back through your previous logs the Y and Z vibrations weren’t as bad, so something changed.

You’ll have to find a way of reducing the Y axis and Z axis vibration. X and Y axis are forward/back left/right so look for unequal vibration damping or anything pulling or touch the flight controller.
Z axis is up and down and can be hard to fix, since prop wash over the arms cant be altered, except maybe by spacing the motors up a little higher. Or make sure props are not over-flying the base plates.
Recently Greg Wilson made a huge difference to his vibrations by dynamically balancing the motors and experimenting with the FC mounting:

The good thing is the Harmonic Notch Filter settings were working well, even if only for a short time. Before you fly next you’ll be able to set these to turn off the extra logging, but leave everything else how it is now:



Thank you for answer.

  1. If there is a problem with IMU2, how can I fix this problem?

  2. The log you saw is like the data that the quad crashed while flying out of control.
    There are vibrations in the other logs as well, but this is around 20.

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