Originally Posted by flyflash

Thanks for the help. Log 05 this flight was without problems, I landed normally, but in the log I saw these fluctuations. the sound of the motors, as if they are momentarily braked. Log 06 and 07 at the end of the flight were fluctuations in pitch and roll and crash with the disarm. It looks as if the copter is resonating, but I do not see it in the logs. Flight controller softmounted, Motors hardmounted, no capacitor. In 8/8 mode, dshot300 flies normally.
PS Made a softmount motor and the problem with the twitch gyro disappeared. But there were oscillation. The problem in the memory card work and frequency of blackbox logging rate, with the black box turned off (without a memory card) flies well.

Then what you see is probably what TCHTHSKY said- bumping the ground as you land.

Originally Posted by flyflash

Thanks for the help. Log 05 this flight was without problems, I landed normally, but in the log I saw these fluctuations. the sound of the motors, as if they are momentarily braked. Log 06 and 07 at the end of the flight were fluctuations in pitch and roll and crash with the disarm. It looks as if the copter is resonating, but I do not see it in the logs. Flight controller softmounted, Motors hardmounted, no capacitor. In 8/8 mode, dshot300 flies normally.
PS Made a softmount motor and the problem with the twitch gyro disappeared. But there were oscillation. The problem in the memory card work and frequency of blackbox logging rate, with the black box turned off (without a memory card) flies well.

Did you turn off sd card dma ? Format the card using sdcard formatter tool - https://www.sdcard.org/downloads/formatter_4/

Originally Posted by Arakon

This is a hover/light flight log set at 3S and 2S. I'm seeing shaking in flight especially when accelerating/punching throttle, mostly on the yaw axis.
Am I right in seeing that D is overactive and causing it?
https://gfycat.com/VacantUnconsciousHammerheadbird
See the shaking there when taking off and also when punching out.
In the video, I was using 3S and PIDs:
set p_pitch = 42
set i_pitch = 45
set d_pitch = 20
set p_roll = 35
set d_roll = 17
set p_yaw = 85

Reducing yaw P actually makes zero difference, so I believe the issue is not yaw related.

Looked at both logs and it is ALL coming from the Roll & Pitch D-Terms. Yaw is clean.
My GUESS is you need to Tune the D-term filters.
Since this is running the Pre-release v3.2 READ Boris' ßF Thread for discussions on how to Tune V3.2

Filters are off except for LPF and dynamic filter.

Originally Posted by Arakon

Filters are off except for LPF and dynamic filter.

Can you point to times per LOG where you see this shaking, so we talk about same events ?

Originally Posted by waltr

Then what you see is probably what TCHTHSKY said- bumping the ground as you land.

Yes, I just inattentively read it. It's really "bumping the ground as you land".
And with hard motor mount flies well

Originally Posted by saxin

Did you turn off sd card dma ?

Yes. Now flies well.

Originally Posted by saxin

Format the card using sdcard formatter tool - https://www.sdcard.org/downloads/formatter_4/

It seems to me it helped. Now works with "sdcard_dma = on". But I'm not sure.
Thanks!

Originally Posted by saxin

Can you point to times per LOG where you see this shaking, so we talk about same events ?

I unfortunately don't have a log of a flight with it, only careful indoor flying. The logger is at best loosely soldered on and held by the battery strap, nothing I'd dare to subject to fullspeed flying and flips/rolls. This is a 2" copter that has absolutely no space to properly mount it.

Okay.. turns out that most likely it was a dying runcam lens.
I had mad shakes on the last flight, but none of that was audible in the motors.

Originally Posted by waltr

Ok, probably not 8k/8k but do check the CPU loading and cycle times - they should be steady- not bouncing around.

Could be the FAQ #56 issue in particular electrical noise getting int the ESC signal. Which ESC Protocol are you running?
If MS try OS42. If dshot then this shouldn't be an issue but could be.
Do you have added a large value, low ESR Cap??

Try hovering in ACRO mode which is Gyro Only - Angle Mode puts Accelerometer date into the PIDC loop so if this doesn't do this in Acro mode it might be the Accelerometer.

Update:
i replaced the 1000uf/25v Cap with a larger 2200uf/25v Low ESR Cap, also i changed the soft-mounting method of my FC from rubber O-rings (usually used on my T-rex Helis) that were under the FC plastic bolts to the Rubber pads that comes with the DYS F4 FC, they fit the holes of the FC and provide soft-mounting from bottom+top of the FC PCB and that was it, quad is smooth as silk now and the log shows very clean Gyro/Motors graph now
( 8 tests with Blackbox logs already done, and zero issue in the Logs so far )

Also for the record, i returned to using 8k/8k looptime, also i tested with both motor timings : Medium and Medium-High and this doesn't affect things at all. (i'm using Emax RS2205S and still can't decide which is the better timing to use Medium or Medium-High, the motors temp is almost the same using both timings )

I think the 2200uf Low ESR Cap was the key to solve the problem, or maybe the DYS Rubber mounts, anyway thanks for the hints man.
Cheers.

Originally Posted by Rogero

Update:
i replaced the 1000uf/25v Cap with a larger 2200uf/25v Low ESR Cap, also i changed the soft-mounting method of my FC from rubber O-rings (usually used on my T-rex Helis) that were under the FC plastic bolts to the Rubber pads that comes with the DYS F4 FC, they fit the holes of the FC and provide soft-mounting from bottom+top of the FC PCB and that was it, quad is smooth as silk now and the log shows very clean Gyro/Motors graph now
( 8 tests with Blackbox logs already done, and zero issue in the Logs so far )

Also for the record, i returned to using 8k/8k looptime, also i tested with both motor timings : Medium and Medium-High and this doesn't affect things at all. (i'm using Emax RS2205S and still can't decide which is the better timing to use Medium or Medium-High, the motors temp is almost the same using both timings )

I think the 2200uf Low ESR Cap was the key to solve the problem, or maybe the DYS Rubber mounts, anyway thanks for the hints man.
Cheers.

Great news. It is very possible the 1000uF cap was damaged and not longer worked.
Proper soft-mounting of the FC is a very well known fix now and required on many of the newer FCs.
Now have fun flying.

Originally Posted by flyflash

Yes, I just inattentively read it. It's really "bumping the ground as you land".
And with hard motor mount flies well

Did you ever feel "twitching" or was the BB log the only thing you were going by?

Originally Posted by AILERON8

Did you ever feel "twitching" or was the BB log the only thing you were going by?

I did not feel any twitching in flight. When the copter began to oscillate and fall, the BB stopped writing the log. This I understood much later. Twitching was when the copter was lying on the table and I switched on the maximum throttle from the transmitter without prop. I made a flight, where I hard landing on the ground several times, and these peaks were exactly repeated at the moment of landing.

I was having no luck tuning my 130mm build. I made great progress when I switched out the flight controller, now it flies reasonably well with stock Betaflight 3.1.7 PIDs.

But I got the tuning bug during my struggles and enjoyed learning to observe and adjust and so forth. I will comb through this thread as I am sure my remaining problems are nothing new and have been solved many times with your help. I would like to eliminate the little imperfections I have become aware of.

To be sure I do not think I can come up with a new idea, but when I tried using the black box the first thing I noticed is that I am quite incapable of getting a good set of data just running the quad through some paces flying around.

Since I have a transmitter that allows it, I set up a system wherein the trim switches on the elevator, aileron and rudder will feed a steady input determined by an auxiliary potentiometer.

This allows me to fly and put in exact and crisp and uncontaminated steps of various sizes on each axis one at a time.

The results were quite good. I can see textbook PID responses and I am sure if I ever manage to learn enough the black box data will inform adjustments to try.

My build

130mm X frame
hand-made PDB
X6B IBUS receiver (I use a deviated Devo 10 TX)
SPRacing F3 v1
1306 3100kv motors on 6A ESCs
HQProp 3x3x4 or DAL 3045s, still learning about propellers
3s 450 or 850 mAh battery, both work well, waiting for some 650 mph

120g, add 50g or 80g battery (AUW 170-200 grams)

As I said, it flies OK now but I hope to improve it. Here is a screen shot of medium pitch pulses that exhibit some "ringing" when I get off the clicker to stop a rotation. That's the heavier battery and the DQ propellers. Not exactly a monster, but plenty for me at my current abilities.

One question: when I look at the YAW data I collected in this manner, I see that the D term on the PID graph is always 0. If I had set d_yaw to zero, I would expect this, but it is at the deafult setting, 20. Is D not used or used differently or is there a recording flaw?

crash7X

Correct, there is no Yaw D in any of the recent versions of BetaFlight.