Solved SOLVED: Major (Roll) Oscillations when arming quadcopter

[samtkeen]

I am fairly new to drone building and have been helped by my friend who has built drones before. I have built a fairly large drone which I want to use to film and coast, I don't intend to use it for racing of any type. I have also made some modifications in addition to the parts such as battery carrier, FPV camera mount and GoPro mount.

Summary of Issue
The issue I have is that as soon as I arm the drone, it immediately goes to full throttle even when it is below the minimum throttle threshold. This is guaranteed behaviour with airmode enabled, without it enabled it will run at minimum throttle (3%) but as soon as i reach mid throttle it will again oscillate and jump to max throttle immediately.

Troubleshooting
I have tried a variety of troubleshooting and trenched through the forums but not sure what is causing it.

• All motors are rotating the correct direction
• each motor can be spooled manually without issue in the motor tab using the sliders in betaflight or in BLHeli
• all firmware is up to date, FC, Receiver, Radio, ESC.
• FC is soft mounted (rubber anti-vibration offset screws)
• A trial of motors also being soft mounted at one point (3M foam) but did not improve things.
• FC and ESC protocols both on DSHOT
• PID tuning attempted
• All receiver channels are properly and correctly mapped
• everything else (VTX, Rx, radio, etc...) all work as expected.

Attached Files
as you can see from the logs there are large unexpected oscillations in the Roll (Red) Gyro. This seems to be causing all the others to go out of whack. There are screenshots of the BLHeli and Betaflight configuration which are pretty much defaults. Also included are the betaflight logs (without props) unfortunately i didn't have the blackbox running when trying with props. I am now too terrified to test it with props as it chucks it immediately to max throttle!

I am quite lost with what i can do to solve this issue, any ideas? if you need any more info let me know!

 

[JasonK]

but as soon as i reach mid throttle it will again oscillate and jump to max throttle immediately.

Sounds like your getting fly away, your P gain is probably to high. If your P gain is to high, it will over correct, then over correct the other way... and 'fly to the moon' as it tries to level itself out.

--- looking at your videos give s much clearer explanation..

when you don't have props on, you can't test anything related to the PID/etc. as it can't actually control anything.

it looks like your configuration is incorrect, when you had the props on it flipped over, which means one of 2 things ->
- the FC thinks it is upside down and is in angle mode - so it is trying to flip itself right side up.
- you have something related to the FC orientation or motors configured incorrectly, so that when it tries to correct itself, it is increasing the error instead of correcting it.

Make sure that 1) in the main window that when you move the quad, the image moves in sync and is upright the same way. 2) the correct motor relative to the positions on the quad spin up. At least one of these 2 are wrong.

 

[samtkeen]

Hi thanks for your reply
is there a P value you would reccomend then or just try and tune it? and if so just turn it all the way down the gradually increase or?

in response to your first point when calibrating the accelerometer the copter is the correct upward orientation and responds as expected when i tilt the copter. also on the flight controller itself, the physical arrow is facing forward and on the visible(top) side when mounted.

I also have checked the motors match the position according to the diagram (1 back right, 2 front right, 3 back left, 4 front right i think is the order, you can see in the images attatched to original post ) but regardless match the image when i test. they also all turn the correct orientation when using the sliders GUI to power each individual motor in betaflight. I will however check this again to make sure though.

In the meantime any other ideas?

 

[JasonK]

Hi thanks for your reply
is there a P value you would reccomend then or just try and tune it? and if so just turn it all the way down the gradually increase or?

in response to your first point when calibrating the accelerometer the copter is the correct upward orientation and responds as expected when i tilt the copter. also on the flight controller itself, the physical arrow is facing forward and on the visible(top) side when mounted.

I also have checked the motors match the position according to the diagram (1 back right, 2 front right, 3 back left, 4 front right i think is the order, you can see in the images attatched to original post ) but regardless match the image when i test. they also all turn the correct orientation when using the sliders GUI to power each individual motor in betaflight. I will however check this again to make sure though.

In the meantime any other ideas?

well... the video with props on, was not oscillation, it was a flip over, so the p-gain issue is most likely not the issue at the monument (or at least not the biggest issue).

until it doesn't try to flip itself over right after arm, there really isn't anything else to work on.

 

[samtkeen]

okay i will try again with props and see what happens with some p value adjustments.

in the meantime do you have any other suggestions for me to try to solve the flipping issue?

 

[JasonK]

okay i will try again with props and see what happens with some p value adjustments.

in the meantime do you have any other suggestions for me to try to solve the flipping issue?

the flipping issue is the only current issue that I see... the oscillation with the props off doesn't mean anything.

I would double, tripple, quadruple, etc check the configurations as it seems that either your quad thinks it is upside down... or it has its pitch or roll gyro config backwards.

 

[samtkeen]

The quad doesnt seem to flip over but i seem to be getting some "Toilet bowel wobble" as someone called. Also when airmode enabled it still shoots to max throttle even when stick is at zero right after arming. here are log files and will post videos in a moment

 

[samtkeen]

1 video with airmode, goes full throttle then crashes ( nothing important broke)

1 video without airmode enabled, toilet bowl wobble

 

[JasonK]

need to see the videos (I don't see them there in your messages).

 

[CappyAmeric]

Unfortunately, you cannot test min throttle etc. with props off. Prop load is an important component of throttle position. With props off, and air mode enabled, it SHOULD go to high throttle.

I agree with JasonK - the real issue is the flipping over, not throttle position at this time. Once you resolve that, you will likely be able to better test throttle with props ON (safe distance).

I would first make sure in the BF Receiver tab, that you have the correct channel mapping. With props off, battery plugged in, go to BF Receiver tab and make sure that the little quad animation coincides with stick movement.

Also, in the Modes tab, make sure that if you have a turtle mode setup that the switch is OFF.

 

[samtkeen]

sorry the videos didnt seem to want to upload, try this?

In response to @CappyAmeric thanks for reconfiming, i understand with props off it will fully spin up with airmode on. issue is (if the videos work this time) youll see with airmode on and props on it will still go max throttle.

I will test tomorrow with airmode off and a lowerd P and D gain value. i also have locking nuts that will secure my props on tighter fingers crossed. The channel mapping is also set up and matches what I am doing on radio.

in the modes tab i only have ARM, ANGLE, HORIZON AND BEEPER set up so no tutrle mode as far as im aware

link to videos as they are too large:
https://drive.google.com/drive/folders/18JxR21AwF-skCzNbAntpdcU0vlxKG2iJ?usp=sharing

 

[JasonK]

seen the difference between air mode on and air mode off... I would guess that your air mode throttle setting is likely to high. I would work with it off until you get the PID loops configured correctly.

in the second video, you didn't get off the ground quickly, so you could have some I term wind up from the ground preventing the quad from trying stabilize itself. it really wasn't airborn long enough to have a good idea what type of behavior it was having.

 

[samtkeen]

seen the difference between air mode on and air mode off... I would guess that your air mode throttle setting is likely to high. I would work with it off until you get the PID loops configured correctly.

in the second video, you didn't get off the ground quickly, so you could have some I term wind up from the ground preventing the quad from trying stabilize itself. it really wasn't airborn long enough to have a good idea what type of behavior it was having.

Yeah I figured with airmode until I've got it working alright I leave it off for now.

The second video I am very very gradually increasing the throttle as its unstable I'm terrified of it. I'll try with low P values and no airmode tomorrow to try and see what I can get going and a exact log if possible

 

[JasonK]

Also note, the defaults for BetaFlight are for a 5" quad, it looks like you have something a good bit bigger.

A quick internet search seems to indicate that lower PID values are typically safe, just possibly not stable, so lowering them should be safe to try.

it also seems that power to weight ratios have a big deal with if you need higher or lower PID values.

 

[samtkeen]

Also note, the defaults for BetaFlight are for a 5" quad, it looks like you have something a good bit bigger.

A quick internet search seems to indicate that lower PID values are typically safe, just possibly not stable, so lowering them should be safe to try.

it also seems that power to weight ratios have a big deal with if you need higher or lower PID values.

Yeah it appears the defaults are very off what my build requires. As a relative newbie I wasn't sure what specs to set my PID values to be honest so to hear defaults are for a 5 inch quad is good to know. I'll do research for mine

Additional notes
Specs are a 9x4.5 inch pops, weight is about 1.6kg and full thrust at 100% is about 12kg I think. 2812 900kv motors.

Not sure if that shouts any specific things you would reccomend to change but might be helpful to mention for further down the line. Specs of motors are attached (see 900kv)

 

[samtkeen]

I cant really fly it i can just ramp up the throttle a bit before it becomes unstable. please see video attached.

For the video
After this very short video, the motors were very hot, you almost couldn't touch them. Likely indicates issue with my D value?
Also the wobble seems to be mainly in the roll axis, likely due to P value being to high?

also attached is a log file

let me know what you think?

Thanks,
Sam

 

[samtkeen]

 

[JasonK]

1 - I would try your initial testing in rate mode instead of angle mode, that way your only working with the rate loop, and not an angle loop (if the PID settings are low, the angle mode could cause oscillation trying to get back to the expected angle... so it will be hard to figure out if your settings are too low or too high)
2- it appears to be time for some guess and check... basically pick some settings (I would start low), test.. adjust one of the settings (start with your P gains) test again. Repeat until you get something that can at least get airborn. Then at that point, detailed tuning can be done.

 

[samtkeen]

okay great, i will play around with some multpiliers and gain values starting low and see what i can get !

Thanks for the help so far

 

[samtkeen]

I have set my PID as follows and it seems to be better but still getting some "wobliness" and a little drone flyaway but i think this was just amplified by the instability. Unfortunately forgot to bring my recording stuff so dont have a video but you can probably see from the blackbox files the imporvement. Is there more i can do to improve it further?