I can't fly my quadcopter, because my motors oscillates badly after the activation of Harmonic Notch filters

xfacta · May 7, 2023, 12:30am

Also reduce D terms to these:

ATC_RAT_PIT_D,0.00275
ATC_RAT_RLL_D,0.00275

amilcarlucas · May 7, 2023, 11:09am

There is also the system identification flight mode and the off line model based PID tunning that can be done in Matlab Simulink.
But to do that you need a bit of control theory.

Gkar · May 7, 2023, 1:12pm

Hi Sir,
Can you give me more information?
Thanks for your reply!!!

amilcarlucas · May 7, 2023, 5:15pm

github.com

fbredeme/ardupilot_wiki/blob/pr-system-id-improvements/copter/source/docs/systemid-mode-operation.rst

.. _systemid-mode-operation:

.. contents::

System ID Mode Operation
========================

System Identification Mode (SYSID mode) provides a rapid means to develop highly accurate flight
dynamics models (also known as Digital Twin) using flight test data. These models generated by actual vehicle data can then be used for math-model validation and improvement (if one is already available), or they can replace the existing model entirely. Tuning of the control laws including simulation of the closed loop vehicle response can also be done as seen in <systemid-mode-ctrl-optimization>.

The models and associated control law analysis are invaluable to demonstrating
required stability metrics as part of airworthiness certifications.

This flight mode produces a data set of stimulus signals and measured responses that are recorded in the data flash log. These signals are injected and collected at specific parts of the autopilot depending on the purpose of the model being created. The injected signal ("chirp") propagates through the autopilot control structures until they are output to physical actuators that cause the vehicle to react to the injected signals. The frequency sweep and amplitude of the "chirp" can be set by parameters, as well as the injection point.

The vehicle's electrical/mechanical reactions are then monitored by the internal sensors of
the autopilot and logged. By recording the output of these sensors and comparing them to the stimulus
(injected "chirp" signals) the engineer can gain insight to the electrical/mechanical properties and
interactions of the aircraft.

This file has been truncated. show original

and

github.com

fbredeme/ardupilot_wiki/blob/pr-system-id-improvements/copter/source/docs/systemid-mode-operation.rst

.. _systemid-mode-operation:

.. contents::

System ID Mode Operation
========================

System Identification Mode (SYSID mode) provides a rapid means to develop highly accurate flight
dynamics models (also known as Digital Twin) using flight test data. These models generated by actual vehicle data can then be used for math-model validation and improvement (if one is already available), or they can replace the existing model entirely. Tuning of the control laws including simulation of the closed loop vehicle response can also be done as seen in <systemid-mode-ctrl-optimization>.

The models and associated control law analysis are invaluable to demonstrating
required stability metrics as part of airworthiness certifications.

This flight mode produces a data set of stimulus signals and measured responses that are recorded in the data flash log. These signals are injected and collected at specific parts of the autopilot depending on the purpose of the model being created. The injected signal ("chirp") propagates through the autopilot control structures until they are output to physical actuators that cause the vehicle to react to the injected signals. The frequency sweep and amplitude of the "chirp" can be set by parameters, as well as the injection point.

The vehicle's electrical/mechanical reactions are then monitored by the internal sensors of
the autopilot and logged. By recording the output of these sensors and comparing them to the stimulus
(injected "chirp" signals) the engineer can gain insight to the electrical/mechanical properties and
interactions of the aircraft.

This file has been truncated. show original

Gkar · May 7, 2023, 10:39pm

Hi,
This is the new log file. The quadcopter behaves better, especially in holding position and altitude control (the Shawn’s settings for Baro and GPS made a big difference), but it still had serious oscillations. Also, I think there is a problem with Motor 3. The aircraft was always heading towards this motor. Maybe, this also causes the oscillations. In fact, the motor was getting pretty hot and it had a strange noise (this noise had appeared when the harmonic notch filters were activated for the first time) and wouldn’t rotate several times, when I was arming the aircraft. All the motors Sunnysky V4006 are new, as well as the ESCs.

xfacta · May 8, 2023, 12:13am

There’s definitely something wrong with that motor then. It could be a physical issue like the shaft at the bottom of the motor is jammed against the motor mount, or a mounting screw is too long and touching a motor winding. Check the ESC and wires are not shorting to each other or the frame, but that usually gives a more drastic effect.

Gkar · May 15, 2023, 8:09am

Hi,
My motor No3 has a serious problem. I thought that the bearings were the problem, but I replaced them and the motor still has the weird noise and it was getting too hot. Also, at high RPM the motor is not stable and oscillates. I will order a new motor and then I will continue with settings.