Unexplained Yaw with no input

PX4 Autopilot
1

Hi everyone;

I had some weird behavior on a hexacopter that I can’t explain. It’s a Tarot X6 using Pixhawk 6C and PX4 v 1.13.3. Whenever I take it off, it has a tendency to yaw by itself on a random basis. However on one flight, it started to yaw continuously in a circular motion. This is the log file.
Flight Review - Hexarotor (px4.io)

It didn’t do this on previous flights as seen in the log:
Flight Review - Hexarotor (px4.io)

I notice that the Actuator Output graph is different on these two flights. The one with the problem shows the PWM signals bottoming out. I’m wondering why this happened and whether its related to the problem.

Any help will be appreciated.
Joe

2

I am seeing this too, but only on takeoff. I am using PX4 1.14.3

3

I had a similar problem - check if on the I2C bus on which the compass sensor is placed you do not have another device with problems (like different working frequency).

4

Hi! Thanks for the reply. I am using a can gps and am not using the i2c port on my flight controller.

5

you can tilt the motors little inwards or outwards with washers, this will help you with unnecessary yaw moment.

It is quite often to have such problem, i also faced same and then tilted the motors little inwards.

Info about Angled Motor Mounts for Multicopters - Oscar Liang

6

Re: tilting motors.
The drone has a built-in tilt on all the motors so this is not the problem. Also I should point out that this drone has had many flights without this yawing condition. I think the problem might be a bad motor, or else the Pixhawk controller is not working properly. More testing is needed.

Joe

7

May be try re calibrating ESCs and recheck the min and max PWM values for all motors.

8

Hi,

i too faced the issue on PX4 v1.13.3 . I later corrected the issue by titling slightly the arm of one of the rotors which was misaligned.

9

The problem was the PIDs. When I did an Autotune, there was an error message that it failed. But since it was still flying I ignored it. Big mistake. That turned out to be a major navigation issue and it kept getting worse. So after two crashes I put all PIDs back to default values. Viola! no more bad behavior.

Problem solved.

Joe