Skip to content

Commit

Permalink
Apply suggestions from code review
Browse files Browse the repository at this point in the history
  • Loading branch information
hamishwillee committed Jul 10, 2024
1 parent 5d5c719 commit 21d0efd
Showing 1 changed file with 10 additions and 7 deletions.
17 changes: 10 additions & 7 deletions en/config_fw/trimming_guide_fixedwing.md
Original file line number Diff line number Diff line change
Expand Up @@ -33,26 +33,29 @@ The correct order to set the above parameters is:
If you are using an airspeed sensor, also set the correct cruise airspeed (`FW_AIRSPD_TRIM`).
1. Run [auto-trimming](#auto-trimming) during a flight to set `TRIM_ROLL`, `TRIM_PITCH` and `TRIM_YAW`.

Alternatively, if you feel comfortable flying in manual mode, you can also set the trim values manually:
1. Disable auto-trimming using [FW_ATRIM_MODE](../advanced_config/parameter_reference.md#FW_ATRIM_MODE).
Alternatively, if you feel comfortable flying in [Manual mode](../flight_modes_fw/manual.md), you can also set the trim values manually:
1. Disable auto-trimming by setting [FW_ATRIM_MODE=0](../advanced_config/parameter_reference.md#FW_ATRIM_MODE).
1. Fly in manual mode and trim your remote (with the trim switches).
1. Report the values to `TRIM_ROLL/PITCH/YAW` (and remove the trims from your transmitter) or update `TRIM_ROLL/PITCH/YAW` directly during flight via telemetry and QGC.
1. Report the values to `TRIM_ROLL/PITCH/YAW` (and remove the trims from your transmitter), or update `TRIM_ROLL/PITCH/YAW` directly during flight via telemetry and QGC.

### Auto-trimming

<Badge type="warning" text="main (PX4 v1.15)" />

Auto-trimming is enabled by default.
On first flight, auto-trimming estimates the current trim of the aircraft, and then updates the general trim parameters (`TRIM_ROLL`, `TRIM_PITCH` and `TRIM_YAW`) with calibrated values after landing.
Auto-trimming estimates the "center trim" at cruise speed (usually), and is enabled by default.
On first flight (in "Calibration" mode), auto-trimming estimates the current trim of the aircraft, and then updates the general trim parameters (`TRIM_ROLL`, `TRIM_PITCH` and `TRIM_YAW`) with calibrated values after landing.
The trim estimate is only updated when the aircraft flies with a bank angle of less than 10 degrees for more than 7 seconds.
So for the first calibration flight you should fly large circles or several phases of straight and level flight.

On subsequent flights auto-trimming continuously estimates the trim and slowly updates the stored trim parameters.
This reduces the constant load on the integrator of the angular rate control loop.
On subsequent flights (in "Continuous" mode), auto-trimming continuously estimates the trim, reducing the constant load on the integrator of the angular rate control loop if the trim calibration was imperfect or if the trim has changed.
In this mode the stored trim parameters are updated gradually — the maximum change to the trim parameters following each flight is 0.05.

Auto-trimming is enabled using [FW_ATRIM_MODE](../advanced_config/parameter_reference.md#FW_ATRIM_MODE).
This parameter is set to `(1) Calibration` (trim parameters are replaced by the trim estimate on landing) for the first flight and is then automatically changed to `(2) Continuous` mode (trim estimate is used to slowly update the existing trim parameters).

The trims can be reset by setting the `TRIM_ROLL`, `TRIM_PITCH` and `TRIM_YAW` back to `0` and `FW_ATRIM_MODE` to `1`.
This should not normally be necessary as the trims are continuously corrected.

## Advanced Trimming

Given that the downward pitch moment induced by an asymmetric airfoil increases with airspeed and when the flaps are deployed, the aircraft needs to be re-trimmed according to the current measured airspeed and flaps position.
Expand Down

0 comments on commit 21d0efd

Please sign in to comment.