Updates

content/ardupilot/ardupilot-setup-checklist.md

@@ -102,7 +102,7 @@ The values in this section are specific to the Omnibus F4, but the settings aren
 See the [recommended settings](/ardupilot/ardupilot-recommended-settings.html) page for other recommended defaults.
 
 ## In the field
-- [ ] Run an autotune.
+- [ ] Run an [autotune](/ardupilot/miscellaneous-notes.html).
 - [ ] Fly in FBWA and see if you're gaining/losing altitude. Pitch up/down to fly level, check the pitch on the OSD, and use the formula `old_value+pitch*π/180` to get the new value for `AHRS_TRIM_Y` (in radians).
 - [ ] After you set `AHRS_TRIM_Y` correctly above, fly in FBWA at full throttle (or whatever throttle you feel is "full" enough, and note that value), and note the pitch you need so that the wing doesn't climb or sink. Then, set `KFF_THR2PITCH` with the formula `pitch_value_in_deg * 100 / throttle_percentage`. `pitch_value_in_deg` should be positive if you needed up pitch and negative if you needed down pitch.
 
@@ -111,6 +111,6 @@ _(Many thanks to Michel Pastor for his help with everything in this note.)_
 * * *
 
 <p style="font-size:80%; font-style: italic">
-Last updated on January 18, 2022. For any questions/feedback,
+Last updated on January 22, 2022. For any questions/feedback,
 email me at <a href="mailto:hi@stavros.io">hi@stavros.io</a>.
 </p>

content/ardupilot/miscellaneous-notes.md

@@ -2,6 +2,27 @@
 
 These are random AP-related notes that wouldn't fit anywhere else:
 
+
+## Performing an autotune
+
+The [ArduPilot Autotune documentation](https://ardupilot.org/plane/docs/automatic-tuning-with-autotune.html) and the [demo video](https://www.youtube.com/watch?v=Ud_YPu7fgXE) are very detailed on this, but here's the gist on how to run an autotune.
+
+Some things to know are:
+- Autotune does not tune the rotation rates, but does not really depend on them either.
+- You should set `AUTOTUNE_LEVEL` depending on the size of your aircraft. For small/agile craft, you can set `AUTOTUNE_LEVEL` to 7 or more. For larger, more sluggish craft, 6 (or less) is a good level. Under the hood, a higher `AUTOTUNE_LEVEL` decreases `*2SRV_TCONST` and increases `*2SRV_RMAX`).
+
+
+Before you switch into `AUTOTUNE` mode, complete a circle or fly in different directions to allow the airspeed estimator to get an accurate value before running the autotune (or tuning the TECS). After you switch into `AUTOTUNE`, start with left and right roll inputs at maximum stick deflection. You don't need to wait until you hit the max roll angle, what I tend to do is roll max right, leave it for half a second, then roll max left, repeat.
+
+The OSD will start showing you PID numbers, continue until a message saying `ROLL FINISHED` appears. Afterwards, do the same with pitch. Hit full stick deflection up and down, without reaching max pitch limits.
+
+After the `PITCH FINISHED` message appears, continue flying in `AUTOTUNE` for more than ten seconds, to make sure the tune values are saved.
+
+You're done, you can switch to any other mode and continue flying.
+
+_(Thanks to Mike for the above info.)_
+
+
 ## DMA on the Matek F405-Wing
 
 If you want to get DMA on UART3 of the Matek F405-Wing FC (or, more relatedly, the Racerstar F405, because UART1 is Bluetooth there), you can open `libraries/AP_HAL_ChibiOS/hwdef/MatekF405-Wing/hwdef.dat` and comment out line 92ish, where PA15 is defined.
@@ -11,6 +32,6 @@ That will enable DMA on UART3, at the expense of disabling the LED pad.
 * * *
 
 <p style="font-size:80%; font-style: italic">
-Last updated on December 31, 2021. For any questions/feedback,
+Last updated on January 22, 2022. For any questions/feedback,
 email me at <a href="mailto:hi@stavros.io">hi@stavros.io</a>.
 </p>