Abnormal behavior in Loiter

Hello everyone,

After several flights with Stabilize and AltHold, and a trouble-free PID setting on my drone, I tried a switch to LOITER, which was accompanied by a few cold sweats…

As soon as the mode was engaged, the drone started to oscillate and became unmanageable, so I switched back to AltHold and it stabilized immediately.

It’s equipped with a pixhawk 6c and an M9N antenna, and while the two are aligned, the antenna gives me a YAW270 orientation. However, I have an identical configuration that flies very well, and it mentions the same inconsistency.

In short, I’m a bit lost… Does anyone have any clues?

Thanks in advance!

Without the log file of the flight where it occured it is only guesswork and none of us are clairvoyants

Sorry, I was just editing my post.

Firstly, I think you have not done an autotune to your 20" propeller quaddrone and Harmonic Notch filter yet.

how do you derive the following?

Keep these to the default first. you may need to change later for a big drone.

MOT_PWM_TYPE,7 DShot1200, do you think you may have connected it wrongly? SERVO1_FUNCTION,34 (should SERVO9_FUNCTION,33, digital ESC)

according to the tunning guide you have to complete the tune in sequence
angle rate - the inner most control loop
angle - the second control loop, wraps around the angle rate control loop
Loiter adds a 3rd cascading outer PID control loop on top for position. And the inner angle and angle rate loops are still used.

To improve the loiter response, you first need to make sure the innermost angle rate control loop is performing correctly, after that the second level angle control loop is doing OK. And only after that you tune the outermost position control loop.

for big drones after autotune and Alt-hold flying is good, then you can check this post. importantly, you must have a low noise and vibration drone before you start the autotune. your current vibration is a bit high, try to aim for 15 m/s/s max.

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