lib/magnetometer_bias_estimator: Add library for online magnetometer calibration on the ground

Co-authored-by: bresch <brescianimathieu@gmail.com>
2026-10-23 16:33:34 +08:00 · 2021-01-18 11:44:58 -05:00
parent 36d15ada1c
commit d9954ecaf0
7 changed files with 427 additions and 0 deletions
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+/****************************************************************************
+ *
+ *   Copyright (c) 2020 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,
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+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/**
+ * @file MagnetometerBiasEstimator.cpp
+ */
+
+#include "MagnetometerBiasEstimator.hpp"
+
+#include <px4_posix.h>
+#include <drivers/drv_mag.h>
+#include <mathlib/mathlib.h>
+
+using namespace matrix;
+using namespace time_literals;
+
+MagnetometerBiasEstimator::MagnetometerBiasEstimator(const matrix::Dcmf &board_rotation) :
+	ModuleParams(nullptr),
+	_board_rotation(board_rotation)
+{}
+
+void MagnetometerBiasEstimator::extractBias(vehicle_magnetometer_s &mag_raw, const sensor_combined_s &gyro_raw)
+{
+	// fill in vectors
+	Vector3f gyro(gyro_raw.gyro_rad);
+	Vector3f mag(mag_raw.magnetometer_ga);
+
+	// prepare delta time in seconds
+	hrt_abstime time_stamp_current = hrt_absolute_time();
+	float dt  = math::min((time_stamp_current - _time_stamp_last_loop), hrt_abstime(500_ms)) / 1e6f;
+	_time_stamp_last_loop = time_stamp_current;
+
+	_field_sensor_bias_estimator.updateEstimate(gyro, mag, dt);
+	const Vector3f &bias = _field_sensor_bias_estimator.getBias();
+
+	// save the bias to the parameters to apply it given the right circumstances
+	const bool longer_than_10_sec = (time_stamp_current - _time_stamp_last_save) > hrt_abstime(10_s);
+	const bool bias_significant = bias.norm_squared() > (0.01f * 0.01f);
+
+	_actuator_armed_sub.update();
+
+	if (!_actuator_armed_sub.get().armed && bias_significant && longer_than_10_sec) {
+		saveBias(bias);
+		_time_stamp_last_save = time_stamp_current;
+	}
+
+	(mag - bias).copyTo(mag_raw.magnetometer_ga);
+}
+
+void MagnetometerBiasEstimator::saveBias(const matrix::Vector3f &bias)
+{
+	// estimated bias is in body frame, but the driver needs sensor frame
+	const Vector3f transformed_bias = _board_rotation.transpose() * bias;
+
+	// get current calibration
+	updateParams();
+	Vector3f calibration_bias(_param_cal_mag0_xoff.get(),
+				  _param_cal_mag0_yoff.get(),
+				  _param_cal_mag0_zoff.get());
+
+	// estimated bias comes on top of existing calibration
+	calibration_bias += transformed_bias;
+
+	// save new calibration
+	_param_cal_mag0_xoff.set(calibration_bias(0));
+	_param_cal_mag0_yoff.set(calibration_bias(1));
+	_param_cal_mag0_zoff.set(calibration_bias(2));
+	_param_cal_mag0_xoff.commit();
+	_param_cal_mag0_yoff.commit();
+	_param_cal_mag0_zoff.commit();
+
+	// reset internal bias to zero because from now the driver will correct
+	_field_sensor_bias_estimator.setBias(Vector3f());
+}