From 3f765d8bbed07af403439bae63bec11b1fa58116 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Sun, 7 Jul 2019 11:27:28 +1000
Subject: [PATCH] APM_Control: added decay_I() function

used by VTOL planes to decay integrator on fixed wing components when
at very low airspeed
---
 libraries/APM_Control/AP_PitchController.h |  8 ++++++++
 libraries/APM_Control/AP_RollController.h  |  8 ++++++++
 libraries/APM_Control/AP_YawController.h   | 10 +++++++++-
 3 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/libraries/APM_Control/AP_PitchController.h b/libraries/APM_Control/AP_PitchController.h
index e3334416b3..dd2d6eb602 100644
--- a/libraries/APM_Control/AP_PitchController.h
+++ b/libraries/APM_Control/AP_PitchController.h
@@ -26,6 +26,14 @@ public:
 
 	void reset_I();
 
+    /*
+      reduce the integrator, used when we have a low scale factor in a quadplane hover
+    */
+    void decay_I() {
+        // this reduces integrator by 95% over 2s
+        _pid_info.I *= 0.995f;
+    }
+    
     void autotune_start(void) { autotune.start(); }
     void autotune_restore(void) { autotune.stop(); }
 
diff --git a/libraries/APM_Control/AP_RollController.h b/libraries/APM_Control/AP_RollController.h
index 7b243be8e2..9b317f1073 100644
--- a/libraries/APM_Control/AP_RollController.h
+++ b/libraries/APM_Control/AP_RollController.h
@@ -26,6 +26,14 @@ public:
 
 	void reset_I();
 
+    /*
+      reduce the integrator, used when we have a low scale factor in a quadplane hover
+    */
+    void decay_I() {
+        // this reduces integrator by 95% over 2s
+        _pid_info.I *= 0.995f;
+    }
+    
     void autotune_start(void) { autotune.start(); }
     void autotune_restore(void) { autotune.stop(); }
 
diff --git a/libraries/APM_Control/AP_YawController.h b/libraries/APM_Control/AP_YawController.h
index 09edd6daf7..426fcbbbbe 100644
--- a/libraries/APM_Control/AP_YawController.h
+++ b/libraries/APM_Control/AP_YawController.h
@@ -26,7 +26,15 @@ public:
 
 	void reset_I();
 
-	const DataFlash_Class::PID_Info& get_pid_info(void) const {return _pid_info; }
+    const DataFlash_Class::PID_Info& get_pid_info(void) const {return _pid_info; }
+
+    /*
+      reduce the integrator, used when we have a low scale factor in a quadplane hover
+    */
+    void decay_I() {
+        // this reduces integrator by 95% over 2s
+        _pid_info.I *= 0.995f;
+    }
 
 	static const struct AP_Param::GroupInfo var_info[];