AC_AutoTune: fix tracking of maximum angular acceleration

Issue introduced in #27370 and partially fixed in #27762, though evidently not properly tested. Failing to track the maximum can result in dangerously low values being calculated for `ATC_ACCEL_[RPY]_MAX` and the vehicle becoming unflyable. Make the variable a reference so that the maximum value is preserved between function calls.
ArduPilot · Dec 5, 2024 · d7b26a2 · d7b26a2
1 parent 9a5f81a
commit d7b26a2
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Showing 2 changed files with 2 additions and 2 deletions.
diff --git a/libraries/AC_AutoTune/AC_AutoTune_Multi.cpp b/libraries/AC_AutoTune/AC_AutoTune_Multi.cpp
@@ -644,7 +644,7 @@ void AC_AutoTune_Multi::twitching_test_angle(float angle, float rate, float angl
 }
 
 // twitching_measure_acceleration - measure rate of change of measurement
-void AC_AutoTune_Multi::twitching_measure_acceleration(float &accel_average, float rate, float rate_max) const
+void AC_AutoTune_Multi::twitching_measure_acceleration(float &accel_average, float rate, float &rate_max) const
 {
     if (rate_max < rate) {
         rate_max = rate;

diff --git a/libraries/AC_AutoTune/AC_AutoTune_Multi.h b/libraries/AC_AutoTune/AC_AutoTune_Multi.h
@@ -156,7 +156,7 @@ class AC_AutoTune_Multi : public AC_AutoTune
     void twitching_test_angle(float angle, float rate, float angle_target, float &meas_angle_min, float &meas_angle_max, float &meas_rate_min, float &meas_rate_max);
 
     // measure acceleration during twitch test
-    void twitching_measure_acceleration(float &accel_average, float rate, float rate_max) const;
+    void twitching_measure_acceleration(float &accel_average, float rate, float &rate_max) const;
 
     // updating_rate_d_up - increase D and adjust P to optimize the D term for a little bounce back
     // optimize D term while keeping the maximum just below the target by adjusting P