Yawing Issue with EDF (Electric Ducted Fan) Octacopter/Multirotor/Drone/UAV Flight

I have tested this EDF motor based octacopter. several times. I have noticed that there always seems to be some kind of yawing without prompting.

Yesterday I have to pull the yaw stick the left in order to half the yawing. when I release the stick the yawing resumes like when doing RTL.

I calibrated the Compass and IMU.

Could this be an issue with vibration or emi?

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If you you switch into position hold, does he still rotate on the spot or does he go wild and flys big circles?

I took off in Position Hold. All through the video its in position hold.

Armin Strobel said:

If you you switch into position hold, does he still rotate on the spot or does he go wild and flys big circles?

That is what I was expecting. I would say your compass / IMU is working fine.

You have a problem of controllability. I would try to tilt your EDFs a bit more (which I assume you have already done a bit).

Let me know If you don't understand what I mean.

Just for explanation:

A well built ducted fan creates no torque (which you would need to control yaw). The torque of the motor is compensated by the stators / guide vanes. Or seen it from the other side (actio = reactio) the swirl created by the fan is straighten by the stators, so they don't create any external torque.

Was unaware that the EDF should be tilted. 

By how many degrees? Any tilt direction preference for the motors.

Also, do  EMI also affect accelerometers and gyro?



Armin Strobel said:

That is what I was expecting. I would say your compass / IMU is working fine.

You have a problem of controllability. I would try to tilt your EDFs a bit more (which I assume you have already done a bit).

Let me know If you don't understand what I mean.

Just for explanation:

A well built ducted fan creates no torque (which you would need to control yaw). The torque of the motor is compensated by the stators / guide vanes. Or seen it from the other side (actio = reactio) the swirl created by the fan is straighten by the stators, so they don't create any external torque.

That explains all.

I assume the EDF you have are all turning in the same direction.

I don't know your exact setup, thats why i am suggesting a more testing approach.

I would put the trust to something like 20% and then turn the drone around the vertical axis (yaw) in one direction. Half of the EDFs should accelerate and the other ones should slow down a bit. Then you need to turn the EDFs in a way that the ones which accelerated push against the yaw moment you did and the other ones in the other direction. To test the proper direction I would use 45 degrees or so, just to check the proper direction (don't try to fly with it)

For flying i would do a few degrees (maybe 5 degree or a bit less). The yaw motion parameters need be probably adjusted.

The EDF motors have 4 CW and 4 CCW.

Hence why I thought it should function like normal motors.

That said the current draw appear quite high as each motor has a max of  53amps.

Could this affect the IMU and compass?


Armin Strobel said:

That explains all.

I assume the EDF you have are all turning in the same direction.

I don't know your exact setup, thats why i am suggesting a more testing approach.

I would put the trust to something like 20% and then turn the drone around the vertical axis (yaw) in one direction. Half of the EDFs should accelerate and the other ones should slow down a bit. Then you need to turn the EDFs in a way that the ones which accelerated push against the yaw moment you did and the other ones in the other direction. To test the proper direction I would use 45 degrees or so, just to check the proper direction (don't try to fly with it)

For flying i would do a few degrees (maybe 5 degree or a bit less). The yaw motion parameters need be probably adjusted.

Yes, it could but in your case it doesn't. If it would the position control would correct in the wrong direction and would start to go in big circle (would cause most likely a crash).

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