Throttle variations interfere with attitude control

ArduCopter Copter 4.6
1

Hello,
I am currently trying to tune a 7inch quad being my very first time actually tuning a drone with ardupilot. I am having a pretty big problem that I cannot solve on my own :

In accro mode, (and in any other flight mode) the attitude of the drone changes on throttle variations. It is especially bad on low throttle as the drone is no longer locked at the target attitude. Attitude control is resumed when throttle increased. On some punchouts and subsequent throttle chops, the attitude error can reach around 30°, and is especially observed on the pitch axis, but not exclusively.

The setup :
H7 FC with arducopter 4.6.0
BlHeli_S 4in1 ESC (this is constrained unfortunately)
7inch 7040 triblade props
2207 1750kv motors
4S LiPo
969g all up weight

What I did :
I set up the dynamic notch filters using dynamic FFT following Chris Rosser tuning guide.
I tuned the rate PID controller following Chris Rosser tuning guide. This is my first time doing so, so the outcome my be “sub optimal”.
The problem described was observed at all times from the very beginning of the tuning process, to the end. My hope was that as the tuning was getting better, this problem would eventually disappear on its own, but that was not the case.
Here is a list of the parameters I tried to adjust : (ATC_THR_G_BOOST, MOT_THST_EXPO, ATC_THR_MIX_MAX, ATC_THR_MIX_MAN, MOT_SPIN_MIN ).

Here is a log of an accro flight and the corresponding DVR:

Do you think it is caused by bad rate PIDs, or a bad filter setup ? If so, do you have any advice ?
Or is it something else ? Maybe the setup itself is poor an d not likely to fly properly ?

I am a bit lost as this problem is quite a big deal and would make any not-aware pilot react unpredictibly.

Sorry for my poor English, and Thank you.

2

With all due respect to some of the great work that Chris Rosser has done, his Ardupilot tuning guide is full of mistakes and doesn’t work.

Reset your tuning parameters, (PID and filters) to default and start over. Use the guide in the wiki Tuning — Copter documentation or the AMC: How to methodically tune any ArduCopter | MethodicConfigurator

There are large vertical vibraitons. You will need to fix those before you will be able to tune the drone.

Reset ARMING_CHECKS,1. If it won’t arm, figure out why and fix it. In that video if you had to RTL the drone wouldn’t have made it home.

Try this for a filter:

image
image475Ă—543 9.8 KB

It’s not perfect but it will get you started until you get the mechanical vibrations sorted out. There’s no need to use FFT. Throttle based filter will work just fine (if not better)

3 Likes
3

That was a mistake, those guides have errors. Plenty of posts about that on the forum here.
Follow the Arducopter Tuning Guides from the Wiki or the Methodic Configurator.
Arducopter Tuning Process Instructions
Methodic Configurator

3 Likes