ekf2: new gravity observation (#21038)

Signed-off-by: Daniel M. Sahu <danielmohansahu@gmail.com>
2026-10-22 21:33:34 +08:00 · 2023-02-07 13:28:58 -05:00
parent 3e149ee6c5
commit fa6fda6cce
15 changed files with 456 additions and 7 deletions
@@ -0,0 +1,95 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2023 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
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+ *
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+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
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+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name ECL 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
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+ * 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 gravity_fusion.cpp
+ * Fuse observations from the gravity vector to constrain roll
+ * and pitch (a la complementary filter).
+ *
+ * @author Daniel M. Sahu <danielmohansahu@gmail.com>
+ */
+
+#include "ekf.h"
+#include "python/ekf_derivation/generated/compute_gravity_innov_var_and_k_and_h.h"
+
+#include <mathlib/mathlib.h>
+
+void Ekf::controlGravityFusion(const imuSample &imu)
+{
+	// fuse gravity observation if our overall acceleration isn't too big
+	const float gravity_scale = _accel_vec_filt.norm() / CONSTANTS_ONE_G;
+
+	_control_status.flags.gravity_vector = (_params.imu_ctrl & static_cast<int32_t>(ImuCtrl::GravityVector))
+					       && (((gravity_scale >= 0.9f && gravity_scale <= 1.1f)) || _control_status.flags.vehicle_at_rest)
+					       && !isHorizontalAidingActive();
+
+	// get raw accelerometer reading at delayed horizon and expected measurement noise (gaussian)
+	const Vector3f measurement = imu.delta_vel / imu.delta_vel_dt - getAccelBias();
+	const float measurement_var = sq(_params.gravity_noise);
+
+	// calculate kalman gains and innovation variances
+	Vector3f innovation; // innovation of the last gravity fusion observation (m/s**2)
+	Vector3f innovation_variance;
+	Vector24f Kx, Ky, Kz; // Kalman gain vectors
+	sym::ComputeGravityInnovVarAndKAndH(
+		getStateAtFusionHorizonAsVector(), P, measurement, measurement_var, FLT_EPSILON,
+		&innovation, &innovation_variance, &Kx, &Ky, &Kz);
+
+	// fill estimator aid source status
+	resetEstimatorAidStatus(_aid_src_gravity);
+	_aid_src_gravity.timestamp_sample = imu.time_us;
+	measurement.copyTo(_aid_src_gravity.observation);
+
+	for (auto &var : _aid_src_gravity.observation_variance) {
+		var = measurement_var;
+	}
+
+	innovation.copyTo(_aid_src_gravity.innovation);
+	innovation_variance.copyTo(_aid_src_gravity.innovation_variance);
+
+	float innovation_gate = 1.f;
+	setEstimatorAidStatusTestRatio(_aid_src_gravity, innovation_gate);
+
+	_aid_src_gravity.fusion_enabled = _control_status.flags.gravity_vector;
+
+	if (_aid_src_gravity.fusion_enabled && !_aid_src_gravity.innovation_rejected) {
+		// perform fusion for each axis
+		_aid_src_gravity.fused = measurementUpdate(Kx, innovation_variance(0), innovation(0))
+					 && measurementUpdate(Ky, innovation_variance(1), innovation(1))
+					 && measurementUpdate(Kz, innovation_variance(2), innovation(2));
+
+		if (_aid_src_gravity.fused) {
+			_aid_src_gravity.time_last_fuse = imu.time_us;
+		}
+	}
+}