[karla]

The flying joy this sunday was from my 100 sized Heli, training flips

The wing has got most things working now, tilt rotor mechanics, the two main motors, but do have problems with the 3rd motor, not running clean.
Dont really understand where to troubleshoot it. It calibrates fine with Vehicle setup for ESCs and also when trying it in the real configuration in Output, test outputs - runs smooth in low mid and full throttle.
But when using the TX controller only the two main motors runs fine and the 3rd (rear) don't run clean, have stuttering, often enough to be a concern and make it impossible to fly.
I could change motor and ESCs again but I doubt thats really the problem, since it works fine in Test outputs?

(I think I have gone over all the tips of causes of stuttering noted before like, too thin wires, too long wires, if connected to current sensor etc and It has been working before with the this hardware...)

[TheOtherCliff]

That sometimes happens when the ESC and motor don't like each other.  They can work with smooth changes, but not abrupt changes.  Are you using manual thrust control or some baro control (could be jumping a little)?

If the PIDs are tuned too high it might do this.  You might try manual (no stabilization at all) just for a test to see if the third motor runs smoothly, but held down and not allowed to fly.  You could try Rate mode with manual thrust too and actually hover test a little bit.

[karla]

Thanks Cliff.
I tried all tests in manual mode. Also did the ESC calibration as detailed here https://librepilot.atlassian.net/wiki/display/LPDOC/ESC+Calibration
and feel it really completed okay.
However, the 3rd motor still not clean running, especially when applying some input like pitch. I then moved one of the fine working large motors form the wing spar to the rear, to see if it would work - it did not. Same stuttering.
My conclusion is that the ESC driving 3rd motor should be replaced. All 3 ESCs are the same BlHeli 20A.
I also tried with then same brand of motor as the ones working fine, EMAX, result the same though.

Does it matter what motor you have connected to the ESC at time of calibration? I would assume not.

[AerialPerPlexity]

Do the pids have anything to do with the 3rd motor? What I'm getting at is maybe the two dominant motors need bigger pids and the 3rd stabilize motor doesn't  require  the amount  p or I?  And that is why the studdering?  Just a suggestion good luck

[TheOtherCliff]

There is a form of stabilization oscillation (caused by PIDs too high, but don't just reduce PIDs, it can be inconclusive) that can effectively move the throttle toward half stick.  That is why I suggest a test with manual stabilization (none at all) to see if that motor is still jumpy.  Just set to manual stabilization with manual thrust, tie it down or hold it, and run the throttle up to where the motor should jitter.

If it doesn't jitter in manual/manual mode then we know what the problem is.  If it still jitters there, but works fine with "test outputs" then I would guess the RC control signal may be jittering for any of several reasons....   but you said the other motors are smooth while this is jittering.  The third motor is entirely controlled by the normal throttle channel isn't it?

[karla]

Thank you guys and sorry if I expressed myself unclear.
I did try it in manual stabilization for all axis, roll pitch yaw and thrust.
It gives the same jittering result as with all set to rate or attitude stabilization.
All three motors are controlled by the same RC control signal, PPM.

In the Vehicle, Custom, channel/type-table all the three motors have source curve 1, throttle. The third motor also have -64(50%) set for Pitch. If I set this to 0 it still have the same jittery result.



However, what does seem to have great impact is to lower the max in the Output setting all the way from 1900 down to 1700.
How to understand this? Its the same brand and type of ESCs for all three motors.



It seems to give enough rpm and lift even with the propeller on. If this works in the field as well, then I can live it.

[TheOtherCliff]

Has motor #3 ESC been calibrated at 1000, 1900 like #1 and #2?

Also if I recall correctly, the motor (LP code) has about 255 steps running from -127 to +127.  If the motor is already running +127 and you add more (like from pitch) it won't actually go higher.  This should not cause jitter though.

It really sounds like the ESC/motor does not like to run at 1900, but you should be able to see jitter at 1900 with "test outputs" if that is the problem.

[karla]

Yes, all 3 motors calibrated together 1000 to 1900 using the Link function. Followed the HowTo article to the dot.
Did "test outputs", and yes it starts jitter after 1650, but before that is smooth. The other 2 can go all the way to 1900 smooth though.
At 1650 it has really high rpm that feels like full throttle capacity of motor.
Hope this is not a sign the motor or the ESC will soon crash...

[karla]

All my might tells me the ESC for the 3 motor is the culprit.
I have replaced it. Running tests now...

[karla]

Yes. Seem okay now after replacement of ESC of #3 motor and redid the calibration.
All motors running smooth with similar Min, Max and Neutral settings.
Also simplified the output mixing so the pitch is only controlled by main and rear motors (no help from tilting the rotors like before).
Next is test in the field!

[zipray]

[f5soh]

Just a Bicopter with a a frame that's looks like a wing...
but not flying/cannot fly like a fixed wing.

[zipray]

Soon, when I turn the tilting mechanism installed.

[f5soh]

Maybe...
Did you plan some gliding phases ?

Here is a good example of a working configuration:

[zipray]

yes.



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