Fix #9912: Add I-term stability check to servo autotrim#11215
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sensei-hacker wants to merge 2 commits intoiNavFlight:maintenance-9.xfrom
Open
Fix #9912: Add I-term stability check to servo autotrim#11215sensei-hacker wants to merge 2 commits intoiNavFlight:maintenance-9.xfrom
sensei-hacker wants to merge 2 commits intoiNavFlight:maintenance-9.xfrom
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Prevent continuous servo autotrim from applying trim adjustments during maneuver transitions when I-term is changing rapidly due to transient error. Root Cause: The autotrim code verified all flight conditions (level attitude, centered sticks, low rotation rate) but failed to check that the I-term was in a steady state before transferring it to servo trim. During maneuver transitions (e.g., exiting a turn), I-term accumulates transient error. When the plane momentarily satisfies all level-flight conditions, this transient I-term is incorrectly transferred to servo midpoints, causing the aircraft to fly out-of-trim. Changes: - Added I-term rate-of-change tracking in processContinuousServoAutotrim() - Added stability threshold check before applying autotrim - Added configurable parameter: servo_autotrim_iterm_rate_limit (default: 2) - Only transfers I-term to trim when rate of change is below threshold The fix ensures trim updates only occur during true steady-level flight, not during transient conditions following maneuvers. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
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Pull request overview
This PR addresses issue #9912 by adding I-term stability detection to the servo autotrim feature. The fix prevents transferring transient I-term values to servo trim during maneuver transitions by checking that the I-term rate of change is below a configurable threshold before applying trim adjustments.
Key Changes:
- Added
servo_autotrim_iterm_rate_limitconfiguration parameter to control maximum acceptable I-term rate of change - Implemented I-term rate-of-change calculation in the autotrim logic to detect transient vs. stable I-term values
- Updated documentation with the new setting
Reviewed changes
Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.
| File | Description |
|---|---|
| src/main/flight/servos.h | Adds servo_autotrim_iterm_rate_limit field to servoConfig_t struct to store the new configuration parameter |
| src/main/flight/servos.c | Implements I-term stability check by tracking previous I-term values and calculating rate of change before applying autotrim |
| src/main/fc/settings.yaml | Defines the new servo_autotrim_iterm_rate_limit setting with default value of 2 units/sec and range 0-50 |
| docs/Settings.md | Documents the new servo_autotrim_iterm_rate_limit setting for end users |
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- Move I-term tracking outside stable flight check for accurate rate calculation - Move servo_autotrim_iterm_rate_limit to end of struct for EEPROM compatibility
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Summary
Hopefully fixes #9912 - Continuous auto-trim active during maneuvers
Adds I-term stability detection to servo autotrim to prevent transferring transient I-term to servo trim during maneuver transitions.
Root Cause
The autotrim code verified all flight conditions (level attitude, centered sticks, low rotation rate) but failed to check that the I-term was in a steady state before transferring it to servo trim.
During maneuver transitions (e.g., exiting a turn), I-term accumulates transient error. When the plane momentarily satisfies all level-flight conditions, this transient I-term is incorrectly transferred to servo midpoints.
We want to transfer the I-term only when it's stable, not immediately when the pilot centers the sticks after a hard maneuver. How stable is "stable"? I don't know, so I added the temporary setting
servo_autotrim_iterm_rate_limitto for testing. I anticipate that after testing we'll know what a reasonable value is and won't need to add yet another user-facing facing.Testing
Note: This PR requires flight testing to validate the fix. The I-term stability threshold may need adjustment based on flight testing feedback.
Because this does introduce a new setting, an "erase all" and reload of the diff/dump would be needed.
If testers prefer, I could also just use 2 or 3 for testing, and skip the setting.
Related
Potentially Fixes #9912
@Yury-MonZon @ProfDrYoMan