fw landing: improve slope altitude calc to avoid climbout after waypoint. Throttle cut is now defined via altitude

src/modules/fw_pos_control_l1/fw_pos_control_l1_main.cpp

@@ -236,7 +236,7 @@ private:
 		float land_slope_length;
 		float land_H1_virt;
 		float land_flare_alt_relative;
-		float land_thrust_lim_horizontal_distance;
+		float land_thrust_lim_alt_relative;
 		float land_heading_hold_horizontal_distance;
 
 	}		_parameters;			/**< local copies of interesting parameters */
@@ -281,7 +281,7 @@ private:
 		param_t land_slope_length;
 		param_t land_H1_virt;
 		param_t land_flare_alt_relative;
-		param_t land_thrust_lim_horizontal_distance;
+		param_t land_thrust_lim_alt_relative;
 		param_t land_heading_hold_horizontal_distance;
 
 	}		_parameter_handles;		/**< handles for interesting parameters */
@@ -434,7 +434,7 @@ FixedwingPositionControl::FixedwingPositionControl() :
 	_parameter_handles.land_slope_length = param_find("FW_LND_SLLR");
 	_parameter_handles.land_H1_virt = param_find("FW_LND_HVIRT");
 	_parameter_handles.land_flare_alt_relative = param_find("FW_LND_FLALT");
-	_parameter_handles.land_thrust_lim_horizontal_distance = param_find("FW_LND_TLDIST");
+	_parameter_handles.land_thrust_lim_alt_relative = param_find("FW_LND_TLALT");
 	_parameter_handles.land_heading_hold_horizontal_distance = param_find("FW_LND_HHDIST");
 
 	_parameter_handles.time_const = 			param_find("FW_T_TIME_CONST");
@@ -523,7 +523,7 @@ FixedwingPositionControl::parameters_update()
 	param_get(_parameter_handles.land_slope_length, &(_parameters.land_slope_length));
 	param_get(_parameter_handles.land_H1_virt, &(_parameters.land_H1_virt));
 	param_get(_parameter_handles.land_flare_alt_relative, &(_parameters.land_flare_alt_relative));
-	param_get(_parameter_handles.land_thrust_lim_horizontal_distance, &(_parameters.land_thrust_lim_horizontal_distance));
+	param_get(_parameter_handles.land_thrust_lim_alt_relative, &(_parameters.land_thrust_lim_alt_relative));
 	param_get(_parameter_handles.land_heading_hold_horizontal_distance, &(_parameters.land_heading_hold_horizontal_distance));
 
 	_l1_control.set_l1_damping(_parameters.l1_damping);
@@ -558,7 +558,7 @@ FixedwingPositionControl::parameters_update()
 	}
 
 	/* Update the landing slope */
-	landingslope.update(math::radians(_parameters.land_slope_angle), _parameters.land_flare_alt_relative, _parameters.land_thrust_lim_horizontal_distance, _parameters.land_H1_virt);
+	landingslope.update(math::radians(_parameters.land_slope_angle), _parameters.land_flare_alt_relative, _parameters.land_thrust_lim_alt_relative, _parameters.land_H1_virt);
 
 	/* Update and publish the navigation capabilities */
 	_nav_capabilities.landing_slope_angle_rad = landingslope.landing_slope_angle_rad();
@@ -836,6 +836,8 @@ FixedwingPositionControl::control_position(const math::Vector<2> &current_positi
 
 		} else if (pos_sp_triplet.current.type == SETPOINT_TYPE_LAND) {
 
+			float bearing_lastwp_currwp = get_bearing_to_next_waypoint(prev_wp(0), prev_wp(1), curr_wp(0), curr_wp(1));
+
 			/* Horizontal landing control */
 			/* switch to heading hold for the last meters, continue heading hold after */
 			float wp_distance = get_distance_to_next_waypoint(current_position(0), current_position(1), curr_wp(0), curr_wp(1));
@@ -846,7 +848,7 @@ FixedwingPositionControl::control_position(const math::Vector<2> &current_positi
 
 				if (!land_noreturn_horizontal) {//set target_bearing in first occurrence
 					if (pos_sp_triplet.previous.valid) {
-						target_bearing = get_bearing_to_next_waypoint(prev_wp(0), prev_wp(1), curr_wp(0), curr_wp(1));
+						target_bearing = bearing_lastwp_currwp;
 					} else {
 						target_bearing = _att.yaw;
 					}
@@ -888,10 +890,9 @@ FixedwingPositionControl::control_position(const math::Vector<2> &current_positi
 			float airspeed_approach = 1.3f * _parameters.airspeed_min;
 
 			float L_wp_distance = get_distance_to_next_waypoint(prev_wp(0), prev_wp(1), curr_wp(0), curr_wp(1)) * _parameters.land_slope_length;
-			float L_altitude = landingslope.getLandingSlopeAbsoluteAltitude(L_wp_distance, _pos_sp_triplet.current.alt);//getLandingSlopeAbsoluteAltitude(L_wp_distance, _pos_sp_triplet.current.alt, landing_slope_angle_rad, horizontal_slope_displacement);
+			float L_altitude = landingslope.getLandingSlopeAbsoluteAltitude(L_wp_distance, _pos_sp_triplet.current.alt);
-			float landing_slope_alt_desired = landingslope.getLandingSlopeAbsoluteAltitude(wp_distance, _pos_sp_triplet.current.alt);//getLandingSlopeAbsoluteAltitude(wp_distance, _pos_sp_triplet.current.alt, landing_slope_angle_rad, horizontal_slope_displacement);
+			float bearing_airplane_currwp = get_bearing_to_next_waypoint(current_position(0), current_position(1), curr_wp(0), curr_wp(1));
-
+			float landing_slope_alt_desired = landingslope.getLandingSlopeAbsoluteAltitudeSave(wp_distance, bearing_lastwp_currwp, bearing_airplane_currwp, _pos_sp_triplet.current.alt);
-
 
 			if ( (_global_pos.alt < _pos_sp_triplet.current.alt + landingslope.flare_relative_alt()) || land_noreturn_vertical) {  //checking for land_noreturn to avoid unwanted climb out
 
@@ -903,7 +904,7 @@ FixedwingPositionControl::control_position(const math::Vector<2> &current_positi
 				/* kill the throttle if param requests it */
 				throttle_max = _parameters.throttle_max;
 
-				 if (wp_distance < landingslope.motor_lim_horizontal_distance() || land_motor_lim) {
+				 if (_global_pos.alt < _pos_sp_triplet.current.alt + landingslope.motor_lim_relative_alt() || land_motor_lim) {
 					throttle_max = math::min(throttle_max, _parameters.throttle_land_max);
 					if (!land_motor_lim) {
 						land_motor_lim  = true;
@@ -912,7 +913,7 @@ FixedwingPositionControl::control_position(const math::Vector<2> &current_positi
 
 				 }
 
-				float flare_curve_alt = landingslope.getFlareCurveAltitude(wp_distance, _pos_sp_triplet.current.alt);
+				float flare_curve_alt = landingslope.getFlareCurveAltitudeSave(wp_distance, bearing_lastwp_currwp, bearing_airplane_currwp, _pos_sp_triplet.current.alt);
 
 				/* avoid climbout */
 				if (flare_curve_alt_last < flare_curve_alt && land_noreturn_vertical || land_stayonground)

src/modules/fw_pos_control_l1/fw_pos_control_l1_params.c

@@ -172,5 +172,5 @@ PARAM_DEFINE_FLOAT(FW_LND_ANG, 10.0f);
 PARAM_DEFINE_FLOAT(FW_LND_SLLR, 0.9f);
 PARAM_DEFINE_FLOAT(FW_LND_HVIRT, 10.0f);
 PARAM_DEFINE_FLOAT(FW_LND_FLALT, 15.0f);
-PARAM_DEFINE_FLOAT(FW_LND_TLDIST, 30.0f);
+PARAM_DEFINE_FLOAT(FW_LND_TLALT, 5.0f);
 PARAM_DEFINE_FLOAT(FW_LND_HHDIST, 15.0f);

src/modules/fw_pos_control_l1/landingslope.cpp

@@ -48,13 +48,13 @@
 
 void Landingslope::update(float landing_slope_angle_rad,
 		float flare_relative_alt,
-		float motor_lim_horizontal_distance,
+		float motor_lim_relative_alt,
 		float H1_virt)
 {
 
 	_landing_slope_angle_rad = landing_slope_angle_rad;
 	_flare_relative_alt = flare_relative_alt;
-	_motor_lim_horizontal_distance = motor_lim_horizontal_distance;
+	_motor_lim_relative_alt = motor_lim_relative_alt;
 	_H1_virt = H1_virt;
 
 	calculateSlopeValues();
@@ -74,9 +74,21 @@ float Landingslope::getLandingSlopeAbsoluteAltitude(float wp_distance, float wp_
 	return Landingslope::getLandingSlopeAbsoluteAltitude(wp_distance, wp_altitude, _horizontal_slope_displacement, _landing_slope_angle_rad);
 }
 
-float Landingslope::getFlareCurveAltitude(float wp_landing_distance, float wp_landing_altitude)
+float Landingslope::getLandingSlopeAbsoluteAltitudeSave(float wp_distance, float bearing_lastwp_currwp, float bearing_airplane_currwp, float wp_altitude)
 {
-	return wp_landing_altitude + _H0 * expf(-math::max(0.0f, _flare_length - wp_landing_distance)/_flare_constant) - _H1_virt;
+	/* If airplane is in front of waypoint return slope altitude, else return waypoint altitude */
-
+	if (fabsf(bearing_airplane_currwp - bearing_lastwp_currwp) < math::radians(90.0f))
+		return getLandingSlopeAbsoluteAltitude(wp_distance, wp_altitude);
+	else
+		return wp_altitude;
+}
+
+float Landingslope::getFlareCurveAltitudeSave(float wp_landing_distance, float bearing_lastwp_currwp, float bearing_airplane_currwp, float wp_landing_altitude)
+{
+	/* If airplane is in front of waypoint return flare curve altitude, else return waypoint altitude */
+	if (fabsf(bearing_airplane_currwp - bearing_lastwp_currwp) < math::radians(90.0f))
+		return wp_landing_altitude + _H0 * expf(-math::max(0.0f, _flare_length - wp_landing_distance)/_flare_constant) - _H1_virt;
+	else
+		return wp_landing_altitude;
 }
 

src/modules/fw_pos_control_l1/landingslope.h

@@ -49,7 +49,7 @@ private:
 	/* see Documentation/fw_landing.png for a plot of the landing slope */
 	float _landing_slope_angle_rad;			/**< phi in the plot */
 	float _flare_relative_alt;				/**< h_flare,rel in the plot */
-	float _motor_lim_horizontal_distance;
+	float _motor_lim_relative_alt;
 	float _H1_virt;							/**< H1 in the plot */
 	float _H0;								/**< h_flare,rel + H1 in the plot */
 	float _d1;								/**< d1 in the plot */
@@ -63,7 +63,18 @@ public:
 	Landingslope() {}
 	~Landingslope() {}
 
-	float getLandingSlopeAbsoluteAltitude(float wp_landing_distance, float wp_landing_altitude);
+	/**
+	 *
+	 * @return Absolute altitude of point on landing slope at distance to landing waypoint=wp_landing_distance
+	 */
+	float getLandingSlopeAbsoluteAltitude(float wp_distance, float wp_altitude);
+
+	/**
+	 *
+	 * @return Absolute altitude of point on landing slope at distance to landing waypoint=wp_landing_distance
+	 * Performs check if aircraft is in front of waypoint to avoid climbout
+	 */
+	float getLandingSlopeAbsoluteAltitudeSave(float wp_landing_distance, float bearing_lastwp_currwp, float bearing_airplane_currwp, float wp_landing_altitude);
 
 	/**
 	 *
@@ -85,17 +96,17 @@ public:
 	}
 
 
-	float getFlareCurveAltitude(float wp_distance, float wp_altitude);
+	float getFlareCurveAltitudeSave(float wp_distance, float bearing_lastwp_currwp, float bearing_airplane_currwp, float wp_altitude);
 
 	void update(float landing_slope_angle_rad,
 			float flare_relative_alt,
-			float motor_lim_horizontal_distance,
+			float motor_lim_relative_alt,
 			float H1_virt);
 
 
 	inline float landing_slope_angle_rad() {return _landing_slope_angle_rad;}
 	inline float flare_relative_alt() {return _flare_relative_alt;}
-	inline float motor_lim_horizontal_distance() {return _motor_lim_horizontal_distance;}
+	inline float motor_lim_relative_alt() {return _motor_lim_relative_alt;}
 	inline float H1_virt() {return _H1_virt;}
 	inline float H0() {return _H0;}
 	inline float d1() {return _d1;}