Fixed-wing autoland: Introduce parameter to enable/disable the early...

Fixed-wing autoland: Introduce parameter to enable/disable the early activation of the landing configuration

src/modules/fw_pos_control_l1/FixedwingPositionControl.cpp

@@ -75,6 +75,7 @@ FixedwingPositionControl::FixedwingPositionControl() :
 	_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.land_use_terrain_estimate = param_find("FW_LND_USETER");
+	_parameter_handles.land_early_config_change = param_find("FW_LND_EARLYCFG");
 	_parameter_handles.land_airspeed_scale = param_find("FW_LND_AIRSPD_SC");
 	_parameter_handles.land_throtTC_scale = param_find("FW_LND_THRTC_SC");
 
@@ -148,6 +149,7 @@ FixedwingPositionControl::parameters_update()
 	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));
+	param_get(_parameter_handles.land_early_config_change, &(_parameters.land_early_config_change));
 	param_get(_parameter_handles.land_airspeed_scale, &(_parameters.land_airspeed_scale));
 	param_get(_parameter_handles.land_throtTC_scale, &(_parameters.land_throtTC_scale));
 
@@ -847,7 +849,8 @@ FixedwingPositionControl::control_position(const Vector2f &curr_pos, const Vecto
 
 			float alt_sp = pos_sp_curr.alt;
 
-			if (pos_sp_next.type == position_setpoint_s::SETPOINT_TYPE_LAND && pos_sp_next.valid && _l1_control.circle_mode()) {
+			if (pos_sp_next.type == position_setpoint_s::SETPOINT_TYPE_LAND && pos_sp_next.valid
+			    && _l1_control.circle_mode() && _parameters.land_early_config_change == 1) {
 				// We're in a loiter directly before a landing WP. Enable our landing configuration (flaps,
 				// landing airspeed and potentially tighter throttle control) already such that we don't
 				// have to do this switch (which can cause significant altitude errors) close to the ground.

src/modules/fw_pos_control_l1/FixedwingPositionControl.hpp

@@ -294,6 +294,7 @@ private:
 		float land_flare_pitch_min_deg;
 		float land_flare_pitch_max_deg;
 		int32_t land_use_terrain_estimate;
+		int32_t land_early_config_change;
 		float land_airspeed_scale;
 		float land_throtTC_scale;
 
@@ -358,6 +359,7 @@ private:
 		param_t land_flare_pitch_min_deg;
 		param_t land_flare_pitch_max_deg;
 		param_t land_use_terrain_estimate;
+		param_t land_early_config_change;
 		param_t land_airspeed_scale;
 		param_t land_throtTC_scale;
 

src/modules/fw_pos_control_l1/fw_pos_control_l1_params.c

@@ -328,6 +328,23 @@ PARAM_DEFINE_FLOAT(FW_LND_HHDIST, 15.0f);
  */
 PARAM_DEFINE_INT32(FW_LND_USETER, 0);
 
+/**
+ * Early landing configuration deployment
+ *
+ * When set to 0/disabled, the landing configuration (flaps, landing airspeed, etc.) is only activated
+ * on the final approach to landing. When set to 1/enabled, it is already activated when entering the
+ * final loiter-down (loiter-to-alt) WP before the landing approach. This shifts the (often large)
+ * altitude and airspeed errors caused by the configuration change away from the ground such that
+ * these are not so critical. It also gives the controller enough time to adapt to the new
+ * configuration such that the landing approach starts with a cleaner initial state.
+ *
+ * @value 0 Disable early land configuration deployment
+ * @value 1 Enable early land configuration deployment
+ *
+ * @group FW L1 Control
+ */
+PARAM_DEFINE_INT32(FW_LND_EARLYCFG, 1);
+
 /**
  * Flare, minimum pitch
  *
@@ -386,7 +403,7 @@ PARAM_DEFINE_FLOAT(FW_LND_AIRSPD_SC, 1.3f);
  * @min 0.2
  * @max 1.0
  * @increment 0.1
- * @group FW TECS
+ * @group FW L1 Control
  */
 PARAM_DEFINE_FLOAT(FW_LND_THRTC_SC, 1.0f);