RC3_TRIM Value for centre stick Throttle(Spring centre stick)

ArduCopter
1

Hi @rmackay9

in my copter i am using Spring centred throttle stick on my RC during calibartion. After calibarion i have seen all channels minimum and maximum value as around 1100 to 1900.
Especially, RC3_MIN = 1111, RC3_Max = 1911 and RC3_TRIM = 1111.

why not the trim value defaultly set to original trim value as RC actual around 1515.

since, current RC3_TRIM value is 1111 and Not 1515 when RC stick was centred but the drone keep decresing the altitude in Loiter Mode. after changing this value to 1515 then i dont see the drone altitude decrese.

Especially for RC centre stick can we have prearm check on TRIM value around 1500?

HERE is the Parameter file

Rc3_trim Change.param (19.0 KB)

2

If you want centered stick:

RC3_TRIM,1515 #or whatever yours needs
PILOT_THR_BHV,1
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3

Hi @kalai1219,

Thanks for the report. During the calculation of the pilot’s desired climb rate (in Loiter and other semi-autonomous modes) the RC3_TRIM values isn’t actually used so I don’t think this could be the cause of the climb in Loiter mode.

It’s possible to trace it through the code (as I have just now to confirm) but in the end it uses the RC_Channel::pwm_to_range_dz() function and it only uses the min and max values.

Hope that helps

4

Trim values are set at the end of the calibration routine. If your throttle stick was off-center, it would’ve recorded that state as trim.

5

Regardless of Center position of the stick its used RC3_TRIM value which will affect the uncommanded decent.

6

Hi @kalai1219,

Sorry, I don’t really understand but please believe me when I say the RC3_TRIM is not used. If you have an onboard log file I’m happy to look into it further.

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7

I think there are two potentially unrelated/conflated issues here:

  1. RC3_TRIM was improperly set at calibration and can be rectified by manually changing it or by re-calibrating and following on-screen instructions.
  2. Unexpected/uncommanded altitude change(s) in LOITER mode, for which log review is required.
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