We are using pixhawk with 3dr Y6 frame 2014 configuration. After arming, when we gradually raised the throttle, we find that the speed of the motors fluctuated, sometimes low and sometimes high. After we have raised the throttle above the midpoint, it seems everything went back to normal, so we continued. When Y6 was about to lift up, we see that it tend to turn clockwise.
We used mission planner to monitor the 6 output channels of pixhawk, we found that before midpoint throttle, pixhawk outputs fluctuated, so we suggest it was not the problem of ESC or motor. Furthermore, we found that channel 2, 4 and 6 outputs are constantly higher than 1,3,5, which we guess is the reason causing Y6 to turn clockwise. But what causes pixhawk to behave this way?
Really appreciate if anyone can help us with this issue!!
Replies
After a rather hard vertical landing the other day, I checked everything out and recalibrated compass, gps, etc. When getting to the current calibration, the motors were fluctuating up and down so couldn't get a good reading to plug in. I decided to do an ESC calibration, then it stopped and current remained constant.
I then ran compassmot; 3%. So far so good.
There was a problem with performing all-at-once ESC calibration; don't recall the thread. Seems like the amount of time allotted after arming was not enough (or you had to be quick) making it difficult if not impossible to do. It worked ok for me tonight though.
After going through the check list, I flew several missions to test out the new 8000mah battery. It worked flawlessly and landed within 1m of the launch every time. Having no wind helped.
Thank you for your reply! i have done all-at-once calibration several times, but not sure whether it can be the root of the problem, since pixhawk outputs also behave in a strange way.
Hi,
I'm currently having the same problem as you but in a quadcopter: outputs 2 and 3 give much more pwm to motors 1 and 4 and don't know really well where is the root of the problem in the pixhawk. I had had the same problem with an apm 2.6 and problem had been solved reflashing and reinstalling the same firmware version. Well now i can't even do the same in the pixhawk.
Did you finally arrived to a solution?
Cheers
When you reflashed and reinstalled the firmware, it reset the trim; I'm not saying that was absolutely the reason why, but highly suspect it. When you do the accel calibration, make sure the FC is level to the copter, and the copter is level to gravity for the first calibration step (surface should be level as possible).
Note in the pic below there is 0 trim for my Spy 750. It was also 0 for my Y6B, but was not always the case. This was accomplished by the above, and it may seem like overkill, but I use scales to balance the CG of my copters. I fought trim/pwm issues for quite a while until figuring out how important balancing is. Using the finger method may work "ok", but the Y6B needs to have equal weight distributed to the arms, otherwise it causes heat issues by overworking motors on the heavy arm, and when more power is called for it exacerbates the problem.
No guarantees, but here's what I'd do:
1) Check your trims, zero them out.
2) Redo accelerometer calibration as described above.
3) Balance the copter. The better it's balanced, the better it will take off and fly, plus the pwm's will be much better correlated.
I'll try to ilustrate what happened to me. What i got in thottle response was something like that:
Must say the pwm in channel 1 varies from something like 990 to 2015, so for an input of 10% throttle should be (cause the throttle response is set to linear in transmitter) around 1100 in all motors, but as you can see 2 and 3 outputs much more than this and 1 and 4 seems to be died.
After trying to reflash and upload the firmware again (it took me like 5 times with the px4upload.exe,so patience) i think i fixed the problem, at least temporarily. Throttle response is something like that now:
Thank you for your quick answer
Regards,
Not sure if I can replicate what you are experiencing... But have seen similar things when building, I had a few problems that I found mainly we had the wrong motors connected to the wrong ports... Depending on the configuration chosen... Also check the motor rotation...
From what I hear it is the above, the motor speed issue is due to the wrong connects to the FC
thx for your reply! i am sure we have connected the motors to the correct position, and the motor direction are also correct...just after a while we played with the Y6 again, and the self-spining issue seems to be solved by itself, without us making much changes...kind of strange