Bad Motor Output with APM!

ArduCopter Copter 3.2
1

Hello everybody,
After struggling with taking of for about 2 weeks, I think that I finally found out that my APM card makes BAD outputs for the motors.
In fact, when I look at the logs I can see that :

  • With auto-analysis I have a WARNING message (highlighted in blue in the first screenshot, link below) : Test: Motor Balance = WARN - Motor channel averages = [1248, 1268, 1149, 1209] Average motor output = 1218
    Difference between min and max motor averages = 119

  • By analysing manually, I can see that in fact, the outputs are bad (on the second screenshot, you can see the legend with the arrows I drawed in green : arrow 1 shows the legend , arrows 2&3 the big differences between the motor outputs in response to the " RCin " and arrow 5 shows what I looked at.

  • I could confirm that something was wrong when I looked at the the “failsafe” section in MP (under “mandatory hardware” ), the radio 1-2-3-4 outputs in the right culumn (called “2nd flight mode”) reacts a bit weirdly ( 3rd and 4th screenshots show what I have when I put throttle at maximum) even without props, and even without the connection to the ESCs, so I don’t think it’s because of them…

I’m quite frustrated because I can’t take off, the quad reacts as if it was drunk, and eventually always crashes as soon as I stop to compensate with the joysticks)… even if everything seems really fine … (I have been through the troubleshooting guide of ardupilot many times, recalibrated and rebuilt the quad 3 times, checked everything was alright). Rmq: I have a 2-3% difference in the minimum throttle between 1 and the other 3 motors, but I calibrated the ESCs 10 times and can’t make it any better…and I read that this should be an acceptable difference.

–> So does andbody have an idea about HOW to correct the motor outputs of the APM ?

Thanks a lot for your time

Antoine

2

Have you checked if the quad is balanced, so the weight is distributed equally for all the motor?

3

Hello,
The quad is balanced, the CofG being underneath the APM and more on the back than on the front.
But anyhow, do you think this is really a hardware issue, as I have the same Warning in the logs when not connecting the ESCs into the output ? (maybe the card kind of saves what it “felt” before and compensate what doesn’t exist anymore, meaning that you are right and I should balance better the weight to the motors in front ! Does the CofG have to be exactly in the middle?)
Thanks.