Drone stability issue

#1

Hello,

I am trying to build Agriculture Sprayer Drone. I am using Pixhawk PX4.
The total weight of drone is near about 18kgs and using 100KV motors and ESC 80Amps.
When I am trying to take off it it starts oscillation and get crashed everytime.
Can anybody suggest me what is the issue here.
Flight Review of my Drone
@DanielePettenuzzo

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#2

Looking at the log it seems that the vibrations in the y axis are the largest, although also in x and z they are pretty high (raw acceleration plot). The magnetic field also seems to be affected by the thrust (thrust and magnetic field plot). For the magnetic field you should try to place the external compass further away from the power cables. While for vibrations you should try to find any loose components or parts on the frame that are flexible or somehow can vibrate when under stress. Moreover with high rate logging we could also see the frequency of the vibrations.

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#3

I improved thrust and magnetic field by making distance between FC and wires.
New Flight data logs(without flying the drone and no propellers with motors)

#4

looks much better. Although with props on the currents will be higher and also the interference can be higher.

#5

can Aluminum case of FC also reduce the magnetic field vibration?

#6

I guess this shouldn’t make a difference because you are using the compass inside the gps module.

#7

Hello Daniele,
Kindly check these new log files I updated new propellers and made some changes.
Test:1
Test:2
although we didn’t fly drone yet and we anchored it on ground and try to increase the thrust.
@DanielePettenuzzo

#8

@abhinav_singh_thakur The mag interference seems much better, although vibrations are still quite high and it would be interesting to see it how it behaves in flight. Moreover you have a peak in the actuator control FFT between 30 and 60 Hz so I would reduce the IMU_GYRO_CUTOFF and the IMU_ACEL_CUTOFF to 20 Hz. This adds a bit of delay so it could be possible that you also need to lower the P gains for pitchrate and rollrate.

#9

Hello,

I am testing with new frame and propellers now(hanging for roll PID tune).
It start and take off and when I try to change in roll it start oscillations.

Kindly suggest me where to start PID values and any other parameters need to set.

Test Log file
@DanielePettenuzzo