Throttle IMAX increasing by itself after flight

I’ve been having an issue with the new beta on both PH1 /and PH2 where my throttle IMAX is increasing itself after a flight… it isn’t noticeable in flght until the IMAX gets to around 50, and you can notice violent jumps and drops in altitude during flight. Then I have to go in MP and change the IMAX back down to 5…

does this have something to do with the new throttle learn feature?

Thank you in advance.

Ben

Hi all,

An issue has risen with my throttle IMAX using the PH2 on our big sprayer drone, Graupner 100A ESCs and u13 motors (yes, big), but I also recall it occurring on the new beta on PH1 just before I switched to the PH2.

Basically, the IMAX is changing itself during flight. I have it set to 5 starting off and then I’ll start experiencing violent jerks either increasing or decreasing altitude during flight and come to land the copter and notice that the throttle IMAX PID has risen to 40 or 50. Then I have to put it back down to 5 and the problem disappears until a couple flights later when it creeps back up to the 40-50 range.

I attached the last log from my flight today. Another issue (don’t know if it’s related or not), occurred when I landed on this flight. As soon as I landed motor 6 would not spool down all the way. In fact, even after I activated an emergency stop of the motors it still spooled back up and got more and more violent, almost flipping the entire copter. Luckily, I toggled the emergency stop until the motor finally quit acting up and managed to quickly unplug the copter.

Attached the log from this flight and hope someone can help me as soon as possible. I really need to make sure this value does not change itself as it can lead to a serious accident for my beginner drone operators here.

Link to log: https://drive.google.com/open?id=0B_Z4GlBtSfZUTU5xSzZyaE5wNzQ

Ben,

Thanks for the report. It sounds like a few separate issues.

  1. IMAX changing by itself should be ok. This is a safety measure to ensure that the altitude controller can always bring the throttle back to zero even if the learned MOT_THST_HOVER climbs.
    I don’t see any violent jerks in altitude in this log. Do you notice any during this particular flight?
    There are a couple of possible causes including EKF lane switching or just bad tuning.
    You could try reducing the throttle accel P and I. I see you’re using 0.7/1.4 so these could be reduced to 0.5 / 1.0.
    It’s also possible to turn off learning of hover throttle. wiki is here: http://ardupilot.org/copter/docs/ac_throttlemid.html#automatic-learning-of-hover-throttle

  2. for motor 6 not spooling down is most likely an ESC calibration issue. Could you test the motors with the MP’s motor test screen? http://ardupilot.org/copter/docs/set-motor-range.html

1 Like

Hi Randy,

Thanks for this information. I will try tinkering with this tomorrow… I know that all my my motors will spin at 5% using the motor test after individually calibrating each of them, so I don’t believe calibration is the issue.

I would like to add that after examining the copter that propeller 6 was extremely damaged- something overlooked from earlier in the day hitting a stemmy piece of brush… I can’t imagine why this would result in the violent spool ups but figured it was worth a mention.

Ben