Just built a large/heavy X8 config running 3.3.3 - 12 pounds and 17.5" props. Tiger 80A ESC and KDE 360 kV motors.
On the initial flight test the X8 would yaw left without input and even at full yaw input would barely rotate to the right. The log files show a pretty large difference in mean output between the CCW motors (outputs 1,3,5,7) and the CW motors (outputs 2,4,6,8) (see attached). I can't find conclusive information on this, but logically it seems like this should not be occurring. I'd expect all 8 motors to have output levels about the same when at a steady hover, is this accurate?
If so, what could be causing this? Obviously I've checked and rechecked the motor connections, spin direction and prop direction.
Replies
Hi Climr,
This is almost definitely a twisted arm. Your yaw controller is only just able to keep the copter from spinning.
Can you add photos.
I agree....classic twisted arm symptoms
When I said perpendicular I was aiming at what Jimmy commented on. If the motors don't provide trust straight down it can cause yaw. Also if the arms are twisting under load it could cause the same effect. The developers created the "H" frames settings for frames that twist around the center also causing a yaw.
Yes if the balance was perfect. If the balance was off or the motors not on perpendicular you would see problems.
Sure the props are all the right type going the right direction on the right motor? It is easy to make a mistake, I know from experience checking and double checking and still have one wrong.
What do you mean "if the balance was perfect"? The balance of the system? In what axis?
The arms we are using are very stiff vertically (Z axis), but not very resistant to a twisting force. Is a torque moment created that could be twisting the arms under power and causing this issue?
Motor connections and prop direction triple checked by 3 independent people. Mission planner A,B,C,D,E,F,G starts at top right, the bottom right and continues around clockwise. Motors spin in the correct CW or CCW direction based on the documentation and props all applied such that air is pushed downward as they spin.
Thanks for any insight!
Get a little bubble-level and make sure all 4 motor mounts are level with eachother and the main frame. They need to be as level with eachother as possible for best performance. Any tilt at all will add a yaw component that you're experiencing. Also if you yaw hard right or left, does the copter become unsettled and roll and pitch? If so that's also a dead giveaway that the motor mounts aren't level.
Also, didn't see it but I assumed you have done: have you calibrated the ESCs?
I had exactly this as well - not found a reason yet, but suspect the yaw PID is way off. Waiting for some clear weather to do some autotune and manual editing of the PIDs.
Let me know if you find something similar.
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