AP_TECS: added TECS_PITCH_MAX and TECS_PITCH_MIN

this allows the TECS controlled pitch limits to be smaller than the
FBWA limits. It is common for a human pilot to want a bit more
discretion over pitch than you want the automatic controller to use

libraries/AP_TECS/AP_TECS.cpp

@@ -133,6 +133,22 @@ const AP_Param::GroupInfo AP_TECS::var_info[] PROGMEM = {
 	// @User: Advanced
     AP_GROUPINFO("LAND_SPDWGT", 14, AP_TECS, _spdWeightLand, 1.0f),
 
+    // @Param: PITCH_MAX
+    // @DisplayName: Maximum pitch in auto flight
+    // @Description: This controls maximum pitch up in automatic throttle modes. If this is set to zero then LIM_PITCH_MAX is used instead. The purpose of this parameter is to allow the use of a smaller pitch range when in automatic flight than what is used in FBWA mode.
+	// @Range: 0 45
+	// @Increment: 1
+	// @User: Advanced
+    AP_GROUPINFO("PITCH_MAX", 15, AP_TECS, _pitch_max, 0),
+
+    // @Param: PITCH_MIN
+    // @DisplayName: Minimum pitch in auto flight
+    // @Description: This controls minimum pitch in automatic throttle modes. If this is set to zero then LIM_PITCH_MIN is used instead. The purpose of this parameter is to allow the use of a smaller pitch range when in automatic flight than what is used in FBWA mode. Note that TECS_PITCH_MIN should be a negative number.
+	// @Range: -45 0
+	// @Increment: 1
+	// @User: Advanced
+    AP_GROUPINFO("PITCH_MIN", 16, AP_TECS, _pitch_min, 0),
+
     AP_GROUPEND
 };
 
@@ -656,8 +672,24 @@ void AP_TECS::update_pitch_throttle(int32_t hgt_dem_cm,
 	_EAS_dem = EAS_dem_cm * 0.01f;
     _THRmaxf  = aparm.throttle_max * 0.01f;
     _THRminf  = aparm.throttle_min * 0.01f;
-	_PITCHmaxf = 0.000174533f * aparm.pitch_limit_max_cd;
-	_PITCHminf = 0.000174533f * aparm.pitch_limit_min_cd;
+
+	// work out the maximum and minimum pitch
+	// if TECS_PITCH_{MAX,MIN} isn't set then use
+	// LIM_PITCH_{MAX,MIN}. Don't allow TECS_PITCH_{MAX,MIN} to be
+	// larger than LIM_PITCH_{MAX,MIN}
+	if (_pitch_max <= 0) {
+		_PITCHmaxf = aparm.pitch_limit_max_cd * 0.01f;
+	} else {
+		_PITCHmaxf = min(_pitch_max, aparm.pitch_limit_max_cd * 0.01f);
+	}
+	if (_pitch_min >= 0) {
+		_PITCHminf = aparm.pitch_limit_min_cd * 0.01f;
+	} else {
+		_PITCHminf = max(_pitch_min, aparm.pitch_limit_min_cd * 0.01f);
+	}
+	// convert to radians
+	_PITCHmaxf = radians(_PITCHmaxf);
+	_PITCHminf = radians(_PITCHminf);
 	_flight_stage = flight_stage;
 
 	// initialise selected states and variables if DT > 1 second or in climbout

libraries/AP_TECS/AP_TECS.h

@@ -120,6 +120,8 @@ private:
 	AP_Float _spdWeightLand;
     AP_Float _landThrottle;
     AP_Float _landAirspeed;
+	AP_Int8  _pitch_max;
+	AP_Int8  _pitch_min;
 	
 	// throttle demand in the range from 0.0 to 1.0
     float _throttle_dem;