Servo auto trim

glebivanov · July 8, 2021, 5:34am

Hello. Servo auto trim work in auto mode?
Tks for answer

yak-54 · July 8, 2021, 6:37am

no its only in stabilized flight modes

SERVO_AUTO_TRIM: Automatic servo trim

Note: This parameter is for advanced users

This enables automatic servo trim in flight. Servos will be trimed in stabilized flight modes when the aircraft is close to level. Changes to servo trim will be saved every 10 seconds and will persist between flights. The automatic trim won’t go more than 20% away from a centered trim.

glebivanov · July 8, 2021, 9:12am

If use fbwa its okay?

Rolf · July 8, 2021, 11:30am

Auto mode is not a stabilized mode ? Who stabilizes the attitude in auto mode if not the autopilot?

Regards Rolf

TunaLobster · July 8, 2021, 1:29pm

Yes servo auto trim works in auto mode. You can read more about which modes are stabilized in the docs.
https://ardupilot.org/plane/docs/flight-modes.html

If you are curious, the code for servo auto trim is here. The comment on that code is quite old. Looks like it is referencing a time when RCIN and SERVOOUT were one and the same.

github.com

ArduPilot/ardupilot/blob/plane4.0/ArduPlane/servos.cpp#L861


void Plane::update_throttle_hover() {
    // update hover throttle at 100Hz
    quadplane.update_throttle_hover();
}


/*
  implement automatic persistent trim of control surfaces with
  AUTO_TRIM=2, only available when SERVO_RNG_ENABLE=1 as otherwise it
  would impact R/C transmitter calibration
 */
void Plane::servos_auto_trim(void)
{
    // only in auto modes and FBWA
    if (!auto_throttle_mode && control_mode != &mode_fbwa) {
        return;
    }
    if (!hal.util->get_soft_armed()) {
        return;
    }
    if (!is_flying()) {
        return;

glebivanov · July 8, 2021, 2:40pm

If use auto trim in auto mode fly point by point its okay?

yak-54 · July 8, 2021, 10:52pm

God is in charge when in auto

Automatic Trim works (AUTO, CRUISE,etc.) or FBWA

but he asked about SERVO AUTO TRIM

i tested it in flight in in auto as soon as i switch out to stabilized mode the trims changed to out of trim

but if i did it in stabilized mode it saved them
this what i had notices on my setup

tridge · July 9, 2021, 12:05am

yes, it works in AUTO mode

yak-54 · July 9, 2021, 12:13am

so Any idea what why it would change switching out of auto to STABILIZE mode then the planes out trim

tridge · July 9, 2021, 12:23am

I’m not really sure what you mean by “it would change”. The code operates the same way in AUTO as FBWA.
Note that it doesn’t run in STABILIZE mode (or several other modes such as ACRO).

yak-54 · July 9, 2021, 12:38am

this what it says in the docs it is why i was getting confused

SERVO Parameters

SERVO_AUTO_TRIM: Automatic servo trim

Note: This parameter is for advanced users

This enables automatic servo trim in flight. Servos will be trimed in stabilized flight modes when the aircraft is close to level. Changes to servo trim will be saved every 10 seconds and will persist between flights. The automatic trim won’t go more than 20% away from a centered trim.