From 5b57df5d1c316c9182fcab7dcf4172c3815ba832 Mon Sep 17 00:00:00 2001
From: Jason Short <jasonshort@gmail.com>
Date: Thu, 22 Sep 2011 17:38:39 -0700
Subject: [PATCH] Refined Throttle Timer reset Reduced Loiter I gain to
 decrease overshoot.

---
 ArduCopter/ArduCopter.pde |  2 ++
 ArduCopter/Attitude.pde   | 17 +++++++++++------
 ArduCopter/config.h       |  4 ++--
 3 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/ArduCopter/ArduCopter.pde b/ArduCopter/ArduCopter.pde
index 445bfdb7be..f5a955e3b1 100644
--- a/ArduCopter/ArduCopter.pde
+++ b/ArduCopter/ArduCopter.pde
@@ -1095,6 +1095,8 @@ void update_throttle_mode(void)
 			}else{
 				g.rc_3.servo_out = 0;
 			}
+			// reset the timer to throttle so that we never get fast I term run-ups
+			throttle_timer = 0;
 			break;
 
 		case THROTTLE_HOLD:
diff --git a/ArduCopter/Attitude.pde b/ArduCopter/Attitude.pde
index 1a85a44d23..8200e98452 100644
--- a/ArduCopter/Attitude.pde
+++ b/ArduCopter/Attitude.pde
@@ -100,9 +100,17 @@ get_nav_throttle(long z_error, int target_speed)
 	rate_error 		= target_speed - altitude_rate;
 	rate_error 		= constrain(rate_error, -110, 110);
 
-	long timer				= millis();
-	float delta_throttle	= (float)(timer - throttle_timer)/1000.0;
-	throttle_timer    		= timer;
+	float delta_throttle;
+
+	// is the throttle_timer uninitialized?
+	if(throttle_timer == 0){
+		throttle_timer = millis();
+		delta_throttle = 0;
+	}else{
+		long timer		= millis();
+		delta_throttle	= (float)(timer - throttle_timer)/1000.0;
+		throttle_timer  = timer;
+	}
 
 	return (int)g.pi_throttle.get_pi(rate_error, delta_throttle);
 }
@@ -162,9 +170,6 @@ static void reset_nav(void)
 	nav_throttle 		= 0;
 	invalid_throttle 	= true;
 
-	// clear the throttle timer
-	throttle_timer = millis();
-
 	g.pi_nav_lat.reset_I();
 	g.pi_nav_lon.reset_I();
 
diff --git a/ArduCopter/config.h b/ArduCopter/config.h
index 68eafe7845..e973722592 100644
--- a/ArduCopter/config.h
+++ b/ArduCopter/config.h
@@ -485,7 +485,7 @@
 # define LOITER_P			.4		//
 #endif
 #ifndef LOITER_I
-# define LOITER_I			0.04	//
+# define LOITER_I			0.01	//
 #endif
 #ifndef LOITER_IMAX
 # define LOITER_IMAX		12		// degrees°
@@ -513,7 +513,7 @@
 # define THROTTLE_P		0.6			//
 #endif
 #ifndef THROTTLE_I
-# define THROTTLE_I		0.03		// with 4m error, 12.5s windup
+# define THROTTLE_I		0.02		// with 4m error, 8 PWM gain/s
 #endif
 #ifndef THROTTLE_IMAX
 # define THROTTLE_IMAX		300