ekf2: add fake height fusion logic

When there is no vertical aiding, fake height is started to constrain the vertical channel of the EKF
2026-10-23 02:43:33 +08:00 · 2022-09-10 12:29:29 -04:00
parent aa716936bf
commit a54fa7b9b1
15 changed files with 177 additions and 7 deletions
@@ -0,0 +1,143 @@
+/****************************************************************************
+ *
+ *   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_height_control.cpp
+ * Control functions for ekf fake height fusion
+ */
+
+#include "ekf.h"
+
+void Ekf::controlFakeHgtFusion()
+{
+	auto &fake_hgt = _aid_src_fake_hgt;
+
+	// clear
+	resetEstimatorAidStatusFlags(fake_hgt);
+
+	// If we aren't doing any aiding, fake position measurements at the last known vertical position to constrain drift
+	const bool fake_hgt_data_ready = isTimedOut(fake_hgt.time_last_fuse, (uint64_t)2e5); // Fuse fake height at a limited rate
+
+	if (fake_hgt_data_ready) {
+		const bool continuing_conditions_passing = !isVerticalAidingActive();
+		const bool starting_conditions_passing = continuing_conditions_passing;
+
+		if (_control_status.flags.fake_hgt) {
+			if (continuing_conditions_passing) {
+				fuseFakeHgt();
+
+				const bool is_fusion_failing = isTimedOut(fake_hgt.time_last_fuse, (uint64_t)4e5);
+
+				if (is_fusion_failing) {
+					resetFakeHgtFusion();
+				}
+
+			} else {
+				stopFakeHgtFusion();
+			}
+
+		} else {
+			if (starting_conditions_passing) {
+				startFakeHgtFusion();
+			}
+		}
+	}
+}
+
+void Ekf::startFakeHgtFusion()
+{
+	if (!_control_status.flags.fake_hgt) {
+		ECL_INFO("start fake height fusion");
+		_control_status.flags.fake_hgt = true;
+		resetFakeHgtFusion();
+	}
+}
+
+void Ekf::resetFakeHgtFusion()
+{
+	ECL_INFO("reset fake height fusion");
+	_last_known_pos(2) = _state.pos(2);
+
+	resetVerticalVelocityToZero();
+	resetHeightToLastKnown();
+
+	_aid_src_fake_hgt.time_last_fuse = _imu_sample_delayed.time_us;
+}
+
+void Ekf::resetHeightToLastKnown()
+{
+	_information_events.flags.reset_pos_to_last_known = true;
+	ECL_INFO("reset height to last known");
+	resetVerticalPositionTo(_last_known_pos(2));
+	P.uncorrelateCovarianceSetVariance<1>(9, sq(_params.pos_noaid_noise));
+}
+
+void Ekf::stopFakeHgtFusion()
+{
+	if (_control_status.flags.fake_hgt) {
+		ECL_INFO("stop fake height fusion");
+		_control_status.flags.fake_hgt = false;
+
+		resetEstimatorAidStatus(_aid_src_fake_hgt);
+	}
+}
+
+void Ekf::fuseFakeHgt()
+{
+	const float obs_var = sq(_params.pos_noaid_noise);
+
+	const float innov_gate = 3.f;
+
+	auto &fake_hgt = _aid_src_fake_hgt;
+
+	fake_hgt.observation = _last_known_pos(2);
+	fake_hgt.observation_variance = obs_var;
+
+	fake_hgt.innovation = _state.pos(2) - _last_known_pos(2);
+	fake_hgt.innovation_variance = P(9, 9) + obs_var;
+
+	setEstimatorAidStatusTestRatio(fake_hgt, innov_gate);
+
+	// always protect against extreme values that could result in a NaN
+	fake_hgt.fusion_enabled = fake_hgt.test_ratio < sq(100.0f / innov_gate);
+
+	// fuse
+	if (fake_hgt.fusion_enabled && !fake_hgt.innovation_rejected) {
+		if (fuseVelPosHeight(fake_hgt.innovation, fake_hgt.innovation_variance, 5)) {
+			fake_hgt.fused = true;
+			fake_hgt.time_last_fuse = _imu_sample_delayed.time_us;
+		}
+	}
+
+	fake_hgt.timestamp_sample = _imu_sample_delayed.time_us;
+}