ekf: refactor fake position control logic

src/modules/ekf2/CMakeLists.txt

@@ -54,6 +54,7 @@ px4_add_module(
 		EKF/ekf_helper.cpp
 		EKF/EKFGSF_yaw.cpp
 		EKF/estimator_interface.cpp
+		EKF/fake_pos_control.cpp
 		EKF/gps_checks.cpp
 		EKF/gps_control.cpp
 		EKF/gps_fusion.cpp

src/modules/ekf2/EKF/CMakeLists.txt

@@ -41,6 +41,7 @@ add_library(ecl_EKF
 	ekf_helper.cpp
 	EKFGSF_yaw.cpp
 	estimator_interface.cpp
+	fake_pos_control.cpp
 	gps_checks.cpp
 	gps_control.cpp
 	gps_fusion.cpp

src/modules/ekf2/EKF/control.cpp

@@ -1066,64 +1066,6 @@ void Ekf::controlDragFusion()
 	}
 }
 
-void Ekf::controlFakePosFusion()
-{
-	// if we aren't doing any aiding, fake position measurements at the last known position to constrain drift
-	// Coincide fake measurements with baro data for efficiency with a minimum fusion rate of 5Hz
-
-	if (!isHorizontalAidingActive()
-	    && !(_control_status.flags.fuse_aspd && _control_status.flags.fuse_beta)) {
-
-		// We now need to use a synthetic position observation to prevent unconstrained drift of the INS states.
-		_using_synthetic_position = true;
-
-		// Fuse synthetic position observations every 200msec
-		if (isTimedOut(_time_last_fake_pos, (uint64_t)2e5)) {
-
-			// Reset position and velocity states if we re-commence this aiding method
-			if (isTimedOut(_time_last_fake_pos, (uint64_t)4e5)) {
-				_last_known_posNE = _state.pos.xy();
-				resetHorizontalPosition();
-				resetVelocity();
-				_fuse_hpos_as_odom = false;
-
-				if (_time_last_fake_pos != 0) {
-					_warning_events.flags.stopping_navigation = true;
-					ECL_WARN("stopping navigation");
-				}
-
-			}
-
-			_time_last_fake_pos = _time_last_imu;
-
-			Vector3f fake_pos_obs_var;
-
-			if (_control_status.flags.in_air && _control_status.flags.tilt_align) {
-				fake_pos_obs_var(0) = fake_pos_obs_var(1) = sq(fmaxf(_params.pos_noaid_noise, _params.gps_pos_noise));
-
-			} else if (_control_status.flags.vehicle_at_rest) {
-				// Accelerate tilt fine alignment by fusing more
-				// aggressively when the vehicle is at rest
-				fake_pos_obs_var(0) = fake_pos_obs_var(1) = sq(0.1f);
-
-			} else {
-				fake_pos_obs_var(0) = fake_pos_obs_var(1) = sq(0.5f);
-			}
-
-			_gps_pos_innov.xy() = Vector2f(_state.pos) - _last_known_posNE;
-
-			const Vector2f fake_pos_innov_gate(3.0f, 3.0f);
-
-			fuseHorizontalPosition(_gps_pos_innov, fake_pos_innov_gate, fake_pos_obs_var,
-					       _gps_pos_innov_var, _gps_pos_test_ratio, true);
-		}
-
-	} else {
-		_using_synthetic_position = false;
-	}
-
-}
-
 void Ekf::controlAuxVelFusion()
 {
 	bool data_ready = false;

src/modules/ekf2/EKF/ekf.h

@@ -382,8 +382,7 @@ private:
 	uint64_t _time_last_flow_terrain_fuse{0}; ///< time the last fusion of optical flow measurements for terrain estimation were performed (uSec)
 	uint64_t _time_last_arsp_fuse{0};	///< time the last fusion of airspeed measurements were performed (uSec)
 	uint64_t _time_last_beta_fuse{0};	///< time the last fusion of synthetic sideslip measurements were performed (uSec)
-	uint64_t _time_last_fake_pos{0};	///< last time we faked position measurements to constrain tilt errors during operation without external aiding (uSec)
-
+	uint64_t _time_last_fake_pos_fuse{0};	///< last time we faked position measurements to constrain tilt errors during operation without external aiding (uSec)
 	uint64_t _time_last_gps_yaw_fuse{0};	///< time the last fusion of GPS yaw measurements were performed (uSec)
 	uint64_t _time_last_gps_yaw_data{0};	///< time the last GPS yaw measurement was available (uSec)
 	uint8_t _nb_gps_yaw_reset_available{0}; ///< remaining number of resets allowed before switching to another aiding source
@@ -1009,6 +1008,11 @@ private:
 
 	void stopFlowFusion();
 
+	void startFakePosFusion();
+	void resetFakePosFusion();
+	void stopFakePosFusion();
+	void fuseFakePosition();
+
 	void setVelPosFaultStatus(const int index, const bool status);
 
 	// reset the quaternion states and covariances to the new yaw value, preserving the roll and pitch

src/modules/ekf2/EKF/fake_pos_control.cpp

@@ -0,0 +1,125 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2022 PX4 Development Team. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name PX4 nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/**
+ * @file fake_pos_control.cpp
+ * Control functions for ekf fake position fusion
+ */
+
+#include "ekf.h"
+
+void Ekf::controlFakePosFusion()
+{
+	// If we aren't doing any aiding, fake position measurements at the last known position to constrain drift
+	// During intial tilt aligment, fake position is used to perform a "quasi-stationary" leveling of the EKF
+	const bool fake_pos_data_ready = isTimedOut(_time_last_fake_pos_fuse, (uint64_t)2e5); // Fuse fake position at a limited rate
+
+	if (fake_pos_data_ready) {
+		const bool continuing_conditions_passing = !isHorizontalAidingActive();
+		const bool starting_conditions_passing = continuing_conditions_passing;
+
+		if (_using_synthetic_position) {
+			if (continuing_conditions_passing) {
+				fuseFakePosition();
+
+				const bool is_fusion_failing = isTimedOut(_time_last_fake_pos_fuse, (uint64_t)4e5);
+
+				if (is_fusion_failing) {
+					resetFakePosFusion();
+				}
+
+			} else {
+				stopFakePosFusion();
+			}
+
+		} else {
+			if (starting_conditions_passing) {
+				startFakePosFusion();
+
+				if (_control_status.flags.tilt_align) {
+					// The fake position fusion is not started for initial alignement
+					_warning_events.flags.stopping_navigation = true;
+					ECL_WARN("stopping navigation");
+				}
+			}
+		}
+	}
+}
+
+void Ekf::startFakePosFusion()
+{
+	if (!_using_synthetic_position) {
+		_using_synthetic_position = true;
+		_fuse_hpos_as_odom = false; // TODO: needed?
+		resetFakePosFusion();
+	}
+}
+
+void Ekf::resetFakePosFusion()
+{
+	_last_known_posNE = _state.pos.xy();
+	resetHorizontalPosition();
+	resetVelocity();
+	_time_last_fake_pos_fuse = _time_last_imu;
+}
+
+void Ekf::stopFakePosFusion()
+{
+	_using_synthetic_position = false;
+}
+
+void Ekf::fuseFakePosition()
+{
+	Vector3f fake_pos_obs_var;
+
+	if (_control_status.flags.in_air && _control_status.flags.tilt_align) {
+		fake_pos_obs_var(0) = fake_pos_obs_var(1) = sq(fmaxf(_params.pos_noaid_noise, _params.gps_pos_noise));
+
+	} else if (_control_status.flags.vehicle_at_rest) {
+		// Accelerate tilt fine alignment by fusing more
+		// aggressively when the vehicle is at rest
+		fake_pos_obs_var(0) = fake_pos_obs_var(1) = sq(0.1f);
+
+	} else {
+		fake_pos_obs_var(0) = fake_pos_obs_var(1) = sq(0.5f);
+	}
+
+	_gps_pos_innov.xy() = Vector2f(_state.pos) - _last_known_posNE;
+
+	const Vector2f fake_pos_innov_gate(3.0f, 3.0f);
+
+	if (fuseHorizontalPosition(_gps_pos_innov, fake_pos_innov_gate, fake_pos_obs_var,
+	                           _gps_pos_innov_var, _gps_pos_test_ratio, true)) {
+		_time_last_fake_pos_fuse = _time_last_imu;
+	}
+}

src/modules/ekf2/test/test_EKF_basics.cpp

@@ -67,7 +67,7 @@ public:
 	SensorSimulator _sensor_simulator;
 
 	// Duration of initalization with only providing baro,mag and IMU
-	const uint32_t _init_duration_s{4};
+	const uint32_t _init_duration_s{5};
 
 protected:
 	double _latitude  {0.0};