Merge pull request #1341 from PX4/fwlandingterrain

FW landing: use terrain estimate

2 files changed, 84 insertions, 74 deletions

diff --git a/src/modules/fw_pos_control_l1/fw_pos_control_l1_main.cpp b/src/modules/fw_pos_control_l1/fw_pos_control_l1_main.cpp
index fdb1b2429..dbaecfbed 100644
--- a/src/modules/fw_pos_control_l1/fw_pos_control_l1_main.cpp
+++ b/src/modules/fw_pos_control_l1/fw_pos_control_l1_main.cpp
@@ -88,7 +88,6 @@
 #include <launchdetection/LaunchDetector.h>
 #include <ecl/l1/ecl_l1_pos_controller.h>
 #include <external_lgpl/tecs/tecs.h>
-#include <drivers/drv_range_finder.h>
 #include "landingslope.h"
 #include "mtecs/mTecs.h"
 
@@ -146,7 +145,6 @@ private:
 	int 		_params_sub;			/**< notification of parameter updates */
 	int 		_manual_control_sub;		/**< notification of manual control updates */
 	int		_sensor_combined_sub;		/**< for body frame accelerations */
-	int		_range_finder_sub;		/**< range finder subscription */
 
 	orb_advert_t	_attitude_sp_pub;		/**< attitude setpoint */
 	orb_advert_t	_tecs_status_pub;		/**< TECS status publication */
@@ -162,17 +160,16 @@ private:
 	struct vehicle_global_position_s		_global_pos;			/**< global vehicle position */
 	struct position_setpoint_triplet_s		_pos_sp_triplet;		/**< triplet of mission items */
 	struct sensor_combined_s			_sensor_combined;		/**< for body frame accelerations */
-	struct range_finder_report 			_range_finder;			/**< range finder report */
 
 	perf_counter_t	_loop_perf;			/**< loop performance counter */
 
 	/* land states */
-	/* not in non-abort mode for landing yet */
 	bool land_noreturn_horizontal;
 	bool land_noreturn_vertical;
 	bool land_stayonground;
 	bool land_motor_lim;
 	bool land_onslope;
+	bool land_useterrain;
 
 	/* takeoff/launch states */
 	LaunchDetectionResult launch_detection_state;
@@ -243,7 +240,9 @@ private:
 		float land_flare_alt_relative;
 		float land_thrust_lim_alt_relative;
 		float land_heading_hold_horizontal_distance;
-		float range_finder_rel_alt;
+		float land_flare_pitch_min_deg;
+		float land_flare_pitch_max_deg;
+		int land_use_terrain_estimate;
 
 	}		_parameters;			/**< local copies of interesting parameters */
 
@@ -289,7 +288,9 @@ private:
 		param_t land_flare_alt_relative;
 		param_t land_thrust_lim_alt_relative;
 		param_t land_heading_hold_horizontal_distance;
-		param_t range_finder_rel_alt;
+		param_t land_flare_pitch_min_deg;
+		param_t land_flare_pitch_max_deg;
+		param_t land_use_terrain_estimate;
 
 	}		_parameter_handles;		/**< handles for interesting parameters */
 
@@ -321,12 +322,6 @@ private:
 	bool		vehicle_airspeed_poll();
 
 	/**
-	 * Check for range finder updates.
-	 */
-	bool		range_finder_poll();
-
-
-	/**
 	 * Check for position updates.
 	 */
 	void		vehicle_attitude_poll();
@@ -347,9 +342,9 @@ private:
 	void navigation_capabilities_publish();
 
 	/**
-	 * Get the relative alt either from the difference between estimate and waypoint or from the laser range finder
+	 * Return the terrain estimate during landing: uses the wp altitude value or the terrain estimate if available
 	 */
-	float get_relative_landingalt(float land_setpoint_alt, float current_alt, const struct range_finder_report &range_finder, float range_finder_use_relative_alt);
+	float get_terrain_altitude_landing(float land_setpoint_alt, const struct vehicle_global_position_s &global_pos);
 
 	/**
 	 * Control position.
@@ -423,7 +418,6 @@ FixedwingPositionControl::FixedwingPositionControl() :
 	_params_sub(-1),
 	_manual_control_sub(-1),
 	_sensor_combined_sub(-1),
-	_range_finder_sub(-1),
 
 /* publications */
 	_attitude_sp_pub(-1),
@@ -441,7 +435,6 @@ FixedwingPositionControl::FixedwingPositionControl() :
 	_global_pos(),
 	_pos_sp_triplet(),
 	_sensor_combined(),
-	_range_finder(),
 
 /* performance counters */
 	_loop_perf(perf_alloc(PC_ELAPSED, "fw l1 control")),
@@ -451,6 +444,7 @@ FixedwingPositionControl::FixedwingPositionControl() :
 	land_stayonground(false),
 	land_motor_lim(false),
 	land_onslope(false),
+	land_useterrain(false),
 	launch_detection_state(LAUNCHDETECTION_RES_NONE),
 	last_manual(false),
 	landingslope(),
@@ -489,7 +483,9 @@ FixedwingPositionControl::FixedwingPositionControl() :
 	_parameter_handles.land_flare_alt_relative = param_find("FW_LND_FLALT");
 	_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.range_finder_rel_alt = param_find("FW_LND_RFRALT");
+	_parameter_handles.land_flare_pitch_min_deg = param_find("FW_FLARE_PMIN");
+	_parameter_handles.land_flare_pitch_max_deg = param_find("FW_FLARE_PMAX");
+	_parameter_handles.land_use_terrain_estimate= param_find("FW_LND_USETER");
 
 	_parameter_handles.time_const = 			param_find("FW_T_TIME_CONST");
 	_parameter_handles.time_const_throt = 			param_find("FW_T_THRO_CONST");
@@ -590,8 +586,9 @@ FixedwingPositionControl::parameters_update()
 	}
 
 	param_get(_parameter_handles.land_heading_hold_horizontal_distance, &(_parameters.land_heading_hold_horizontal_distance));
-
-	param_get(_parameter_handles.range_finder_rel_alt, &(_parameters.range_finder_rel_alt));
+	param_get(_parameter_handles.land_flare_pitch_min_deg, &(_parameters.land_flare_pitch_min_deg));
+	param_get(_parameter_handles.land_flare_pitch_max_deg, &(_parameters.land_flare_pitch_max_deg));
+	param_get(_parameter_handles.land_use_terrain_estimate, &(_parameters.land_use_terrain_estimate));
 
 	_l1_control.set_l1_damping(_parameters.l1_damping);
 	_l1_control.set_l1_period(_parameters.l1_period);
@@ -695,20 +692,6 @@ FixedwingPositionControl::vehicle_airspeed_poll()
 	return airspeed_updated;
 }
 
-bool
-FixedwingPositionControl::range_finder_poll()
-{
-	/* check if there is a range finder measurement */
-	bool range_finder_updated;
-	orb_check(_range_finder_sub, &range_finder_updated);
-
-	if (range_finder_updated) {
-		orb_copy(ORB_ID(sensor_range_finder), _range_finder_sub, &_range_finder);
-	}
-
-	return range_finder_updated;
-}
-
 void
 FixedwingPositionControl::vehicle_attitude_poll()
 {
@@ -846,21 +829,23 @@ void FixedwingPositionControl::navigation_capabilities_publish()
 	}
 }
 
-float FixedwingPositionControl::get_relative_landingalt(float land_setpoint_alt, float current_alt, const struct range_finder_report &range_finder, float range_finder_use_relative_alt)
+float FixedwingPositionControl::get_terrain_altitude_landing(float land_setpoint_alt, const struct vehicle_global_position_s &global_pos)
 {
-	float rel_alt_estimated = current_alt - land_setpoint_alt;
-
-	/* only use range finder if:
-	 * parameter (range_finder_use_relative_alt) > 0
-	 * the measurement is valid
-	 * the estimated relative altitude (from global altitude estimate and landing waypoint) <= range_finder_use_relative_alt
-	 */
-	if (range_finder_use_relative_alt < 0 || !range_finder.valid || range_finder.distance > range_finder_use_relative_alt ) {
-		return rel_alt_estimated;
+	if (!isfinite(global_pos.terrain_alt)) {
+		return land_setpoint_alt;
 	}
 
-	return range_finder.distance;
-
+	/* Decide if the terrain estimation can be used, once we switched to using the terrain we stick with it
+	 * for the whole landing */
+	if (_parameters.land_use_terrain_estimate && (global_pos.terrain_alt_valid || land_useterrain)) {
+		if(!land_useterrain) {
+			mavlink_log_info(_mavlink_fd, "#audio: Landing, using terrain estimate");
+			land_useterrain = true;
+		}
+		return global_pos.terrain_alt;
+	} else {
+		return land_setpoint_alt;
+	}
 }
 
 bool
@@ -965,10 +950,17 @@ 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));
+			float bearing_airplane_currwp = get_bearing_to_next_waypoint(current_position(0), current_position(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));
+			/* calculate a waypoint distance value which is 0 when the aircraft is behind the waypoint */
+			float wp_distance_save = wp_distance;
+			if (fabsf(bearing_airplane_currwp - bearing_lastwp_currwp) >= math::radians(90.0f)) {
+				wp_distance_save = 0.0f;
+			}
+
 			//warnx("wp dist: %d, alt err: %d, noret: %s", (int)wp_distance, (int)altitude_error, (land_noreturn) ? "YES" : "NO");
 			if (wp_distance < _parameters.land_heading_hold_horizontal_distance || land_noreturn_horizontal) {
 
@@ -1004,29 +996,30 @@ FixedwingPositionControl::control_position(const math::Vector<2> &current_positi
 
 			/* Vertical landing control */
 			//xxx: using the tecs altitude controller for slope control for now
-
-//				/* do not go down too early */
-//				if (wp_distance > 50.0f) {
-//					altitude_error = (_global_triplet.current.alt + 25.0f) - _global_pos.alt;
-//				}
 			/* apply minimum pitch (flare) and limit roll if close to touch down, altitude error is negative (going down) */
 			// XXX this could make a great param
 
-			float flare_pitch_angle_rad = -math::radians(5.0f);//math::radians(pos_sp_triplet.current.param1)
 			float throttle_land = _parameters.throttle_min + (_parameters.throttle_max - _parameters.throttle_min) * 0.1f;
 			float airspeed_land = 1.3f * _parameters.airspeed_min;
 			float airspeed_approach = 1.3f * _parameters.airspeed_min;
 
+			/* Get an estimate of the terrain altitude if available, otherwise terrain_alt will be
+			 * equal to _pos_sp_triplet.current.alt */
+			float terrain_alt = get_terrain_altitude_landing(_pos_sp_triplet.current.alt, _global_pos);
+
 			/* Calculate distance (to landing waypoint) and altitude of last ordinary waypoint L */
-			float L_altitude_rel = _pos_sp_triplet.previous.valid ? _pos_sp_triplet.previous.alt - _pos_sp_triplet.current.alt : 0.0f;
+			float L_altitude_rel = _pos_sp_triplet.previous.valid ?
+				_pos_sp_triplet.previous.alt - terrain_alt : 0.0f;
 
-			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_rel_desired = landingslope.getLandingSlopeRelativeAltitudeSave(wp_distance, bearing_lastwp_currwp, bearing_airplane_currwp);
 
-			float relative_alt = get_relative_landingalt(_pos_sp_triplet.current.alt, _global_pos.alt, _range_finder, _parameters.range_finder_rel_alt);
-
-			if ( (relative_alt < landingslope.flare_relative_alt()) || land_noreturn_vertical) {  //checking for land_noreturn to avoid unwanted climb out
-
+			/* Check if we should start flaring with a vertical and a
+			 * horizontal limit (with some tolerance)
+			 * The horizontal limit is only applied when we are in front of the wp
+			 */
+			if (((_global_pos.alt < terrain_alt + landingslope.flare_relative_alt()) &&
+						(wp_distance_save < landingslope.flare_length() + 5.0f)) ||
+					land_noreturn_vertical) {  //checking for land_noreturn to avoid unwanted climb out
 				/* land with minimal speed */
 
 //					/* force TECS to only control speed with pitch, altitude is only implicitely controlled now */
@@ -1035,7 +1028,7 @@ FixedwingPositionControl::control_position(const math::Vector<2> &current_positi
 				/* kill the throttle if param requests it */
 				throttle_max = _parameters.throttle_max;
 
-				 if (relative_alt < landingslope.motor_lim_relative_alt() || land_motor_lim) {
+				 if (_global_pos.alt < terrain_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;
@@ -1053,12 +1046,13 @@ FixedwingPositionControl::control_position(const math::Vector<2> &current_positi
 					land_stayonground = true;
 				}
 
-				tecs_update_pitch_throttle(_pos_sp_triplet.current.alt + flare_curve_alt_rel,
+				tecs_update_pitch_throttle(terrain_alt + flare_curve_alt_rel,
 						calculate_target_airspeed(airspeed_land), eas2tas,
-						flare_pitch_angle_rad, math::radians(15.0f),
+						 math::radians(_parameters.land_flare_pitch_min_deg),
+						 math::radians(_parameters.land_flare_pitch_max_deg),
 						0.0f, throttle_max, throttle_land,
-						false, flare_pitch_angle_rad,
-						_pos_sp_triplet.current.alt + relative_alt, ground_speed,
+						false,  land_motor_lim ? math::radians(_parameters.land_flare_pitch_min_deg) : math::radians(_parameters.pitch_limit_min),
+						_global_pos.alt, ground_speed,
 						land_motor_lim ? TECS_MODE_LAND_THROTTLELIM : TECS_MODE_LAND);
 
 				if (!land_noreturn_vertical) {
@@ -1079,8 +1073,8 @@ FixedwingPositionControl::control_position(const math::Vector<2> &current_positi
 				  * if current position is below the slope continue at previous wp altitude
 				  * until the intersection with slope
 				  * */
-				float altitude_desired_rel = relative_alt;
-				if (relative_alt > landing_slope_alt_rel_desired || land_onslope) {
+				float altitude_desired_rel;
+				if (_global_pos.alt > terrain_alt + landing_slope_alt_rel_desired || land_onslope) {
 					/* stay on slope */
 					altitude_desired_rel = landing_slope_alt_rel_desired;
 					if (!land_onslope) {
@@ -1089,10 +1083,11 @@ FixedwingPositionControl::control_position(const math::Vector<2> &current_positi
 					}
 				} else {
 					/* continue horizontally */
-					altitude_desired_rel =  _pos_sp_triplet.previous.valid ? L_altitude_rel : relative_alt;
+					altitude_desired_rel =  _pos_sp_triplet.previous.valid ? L_altitude_rel :
+						_global_pos.alt - terrain_alt;
 				}
 
-				tecs_update_pitch_throttle(_pos_sp_triplet.current.alt + altitude_desired_rel,
+				tecs_update_pitch_throttle(terrain_alt + altitude_desired_rel,
 						calculate_target_airspeed(airspeed_approach), eas2tas,
 						math::radians(_parameters.pitch_limit_min),
 						math::radians(_parameters.pitch_limit_max),
@@ -1101,7 +1096,7 @@ FixedwingPositionControl::control_position(const math::Vector<2> &current_positi
 						_parameters.throttle_cruise,
 						false,
 						math::radians(_parameters.pitch_limit_min),
-						_pos_sp_triplet.current.alt + relative_alt,
+						_global_pos.alt,
 						ground_speed);
 			}
 
@@ -1278,7 +1273,6 @@ FixedwingPositionControl::task_main()
 	_airspeed_sub = orb_subscribe(ORB_ID(airspeed));
 	_params_sub = orb_subscribe(ORB_ID(parameter_update));
 	_manual_control_sub = orb_subscribe(ORB_ID(manual_control_setpoint));
-	_range_finder_sub = orb_subscribe(ORB_ID(sensor_range_finder));
 
 	/* rate limit control mode updates to 5Hz */
 	orb_set_interval(_control_mode_sub, 200);
@@ -1357,7 +1351,6 @@ FixedwingPositionControl::task_main()
 			vehicle_setpoint_poll();
 			vehicle_sensor_combined_poll();
 			vehicle_airspeed_poll();
-			range_finder_poll();
 			// vehicle_baro_poll();
 
 			math::Vector<3> ground_speed(_global_pos.vel_n, _global_pos.vel_e,  _global_pos.vel_d);
@@ -1421,6 +1414,7 @@ void FixedwingPositionControl::reset_landing_state()
 	land_stayonground = false;
 	land_motor_lim = false;
 	land_onslope = false;
+	land_useterrain = false;
 }
 
 void FixedwingPositionControl::tecs_update_pitch_throttle(float alt_sp, float v_sp, float eas2tas,
diff --git a/src/modules/fw_pos_control_l1/fw_pos_control_l1_params.c b/src/modules/fw_pos_control_l1/fw_pos_control_l1_params.c
index 847ecbb5c..c00d82232 100644
--- a/src/modules/fw_pos_control_l1/fw_pos_control_l1_params.c
+++ b/src/modules/fw_pos_control_l1/fw_pos_control_l1_params.c
@@ -412,12 +412,28 @@ PARAM_DEFINE_FLOAT(FW_LND_TLALT, -1.0f);
 PARAM_DEFINE_FLOAT(FW_LND_HHDIST, 15.0f);
 
 /**
- * Relative altitude threshold for range finder measurements for use during landing
+ * Enable or disable usage of terrain estimate during landing
  *
- * range finder measurements will only be used if the estimated relative altitude (gobal_pos.alt - landing_waypoint.alt) is < FW_LND_RFRALT
- * set to < 0 to disable
- * the correct value of this parameter depends on your range measuring device as well as on the terrain at the landing location
+ * 0: disabled, 1: enabled
  *
  * @group L1 Control
  */
-PARAM_DEFINE_FLOAT(FW_LND_RFRALT, -1.0f);
+PARAM_DEFINE_INT32(FW_LND_USETER, 0);
+
+/**
+ * Flare, minimum pitch
+ *
+ * Minimum pitch during flare, a positive sign means nose up
+ * Applied once FW_LND_TLALT is reached
+ *
+ */
+PARAM_DEFINE_FLOAT(FW_FLARE_PMIN, 2.5f);
+
+/**
+ * Flare, maximum pitch
+ *
+ * Maximum pitch during flare, a positive sign means nose up
+ * Applied once FW_LND_TLALT is reached
+ *
+ */
+PARAM_DEFINE_FLOAT(FW_FLARE_PMAX, 15.0f);