ekf2_main - Add optical flow innovation pre-flight check (#13036)

* ekf2: Add FirstOrderLpf and InnovationLpf classes for innovation lowpass filtering * ekf2: use InnovLpf filter class in preflight checks * ekf2: move selection of yaw test limit for pre-flight check in function * ekf2: Move pre-flight checks into separate function * ekf2: use static constexpr insetead of inline for sq (square) function * ekf2: Split pre-flight checks in separate functions Also use the same check for all the innovations: innov_lpf < test and innov < 2xtest * ekf2: Add optical flow pre-flight check * ekf2: Combine FirstOrderLpf and InnovationLpf in single class * ekf2: check vel_pos_innov when ev_pos is active as well * ekf2: transform InnovationLpf into a header only library and pass the spike limit during the update call to avoid storing it here * ekf2: Static and const cleanup - set spike_lim constants as static constexpr, set innovation - set checker helper functions as static - rename the mix of heading and yaw as heading to avoid confusion * ekf2: use ternary operator in selectHeadingTestLimit instead of if-else * ekf2: store intermediate redults in const bool flags. Those will be used for logging * ekf2: set variable const whenever possible * ekf2: create PreFlightChecker class that handle all the innovation pre-flight checks. Add simple unit testing Use bitmask instead of general flag to have more granularity * PreFlightChecker: use setter for the innovations to check instead of sending booleans in the update function This makes it more scalable as more checks will be added * ekf: Use booleans instead of bitmask for ekf preflt checks Rename "down" to "vert"
2026-07-03 04:00:36 +08:00 · 2019-10-22 16:22:42 +02:00
parent 644c816a2a
commit 549fb0d5de
9 changed files with 620 additions and 87 deletions
@@ -0,0 +1,45 @@
+############################################################################
+#
+#   Copyright (c) 2019 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.
+#
+#############################################################################
+
+px4_add_library(Ekf2Utility
+	PreFlightChecker.cpp
+)
+
+target_include_directories(Ekf2Utility
+	PUBLIC
+	${CMAKE_CURRENT_SOURCE_DIR}
+)
+
+target_link_libraries(Ekf2Utility PRIVATE mathlib)
+
+px4_add_unit_gtest(SRC PreFlightCheckerTest.cpp LINKLIBS Ekf2Utility)
@@ -0,0 +1,79 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2019 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.
+ *
+ ****************************************************************************/
+
+/**
+ * First order "alpha" IIR digital filter with input saturation
+ */
+
+#include <mathlib/mathlib.h>
+
+class InnovationLpf final
+{
+public:
+	InnovationLpf() = default;
+	~InnovationLpf() = default;
+
+	void reset(float val = 0.f) { _x = val; }
+
+	/**
+	 * Update the filter with a new value and returns the filtered state
+	 * The new value is constained by the limit set in setSpikeLimit
+	 * @param val new input
+	 * @param alpha normalized weight of the new input
+	 * @param spike_limit the amplitude of the saturation at the input of the filter
+	 * @return filtered output
+	 */
+	float update(float val, float alpha, float spike_limit)
+	{
+		float val_constrained = math::constrain(val, -spike_limit, spike_limit);
+		float beta = 1.f - alpha;
+
+		_x = beta * _x + alpha * val_constrained;
+
+		return _x;
+	}
+
+	/**
+	 * Helper function to compute alpha from dt and the inverse of tau
+	 * @param dt sampling time in seconds
+	 * @param tau_inv inverse of the time constant of the filter
+	 * @return alpha, the normalized weight of a new measurement
+	 */
+	static float computeAlphaFromDtAndTauInv(float dt, float tau_inv)
+	{
+		return dt * tau_inv;
+	}
+
+private:
+	float _x; ///< current state of the filter
+};
@@ -0,0 +1,142 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2019 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 PreFlightCheckHelper.cpp
+ * Class handling the EKF2 innovation pre flight checks
+ */
+
+#include "PreFlightChecker.hpp"
+
+void PreFlightChecker::update(const float dt, const ekf2_innovations_s &innov)
+{
+	const float alpha = InnovationLpf::computeAlphaFromDtAndTauInv(dt, _innov_lpf_tau_inv);
+
+	_has_heading_failed = preFlightCheckHeadingFailed(innov, alpha);
+	_has_horiz_vel_failed = preFlightCheckHorizVelFailed(innov, alpha);
+	_has_vert_vel_failed = preFlightCheckVertVelFailed(innov, alpha);
+	_has_height_failed = preFlightCheckHeightFailed(innov, alpha);
+}
+
+bool PreFlightChecker::preFlightCheckHeadingFailed(const ekf2_innovations_s &innov, const float alpha)
+{
+	const float heading_test_limit = selectHeadingTestLimit();
+	const float heading_innov_spike_lim = 2.0f * heading_test_limit;
+
+	const float heading_innov_lpf = _filter_heading_innov.update(innov.heading_innov, alpha, heading_innov_spike_lim);
+
+	return checkInnovFailed(innov.heading_innov, heading_innov_lpf, heading_test_limit);
+}
+
+float PreFlightChecker::selectHeadingTestLimit()
+{
+	// Select the max allowed heading innovaton depending on whether we are not aiding navigation using
+	// observations in the NE reference frame and if the vehicle can use GPS course to realign in flight (fixedwing sideslip fusion).
+	const bool is_ne_aiding = _is_using_gps_aiding || _is_using_ev_pos_aiding;
+
+	return (is_ne_aiding && !_can_observe_heading_in_flight)
+	       ? _nav_heading_innov_test_lim // more restrictive test limit
+	       : _heading_innov_test_lim; // less restrictive test limit
+}
+
+bool PreFlightChecker::preFlightCheckHorizVelFailed(const ekf2_innovations_s &innov, const float alpha)
+{
+	bool has_failed = false;
+
+	if (_is_using_gps_aiding || _is_using_ev_pos_aiding) {
+		const Vector2f vel_ne_innov = Vector2f(innov.vel_pos_innov);
+		Vector2f vel_ne_innov_lpf;
+		vel_ne_innov_lpf(0) = _filter_vel_n_innov.update(vel_ne_innov(0), alpha, _vel_innov_spike_lim);
+		vel_ne_innov_lpf(1) = _filter_vel_n_innov.update(vel_ne_innov(1), alpha, _vel_innov_spike_lim);
+		has_failed |= checkInnov2DFailed(vel_ne_innov, vel_ne_innov_lpf, _vel_innov_test_lim);
+	}
+
+	if (_is_using_flow_aiding) {
+		const Vector2f flow_innov = Vector2f(innov.flow_innov);
+		Vector2f flow_innov_lpf;
+		flow_innov_lpf(0) = _filter_flow_x_innov.update(flow_innov(0), alpha, _flow_innov_spike_lim);
+		flow_innov_lpf(1) = _filter_flow_x_innov.update(flow_innov(1), alpha, _flow_innov_spike_lim);
+		has_failed |= checkInnov2DFailed(flow_innov, flow_innov_lpf, _flow_innov_test_lim);
+	}
+
+	return has_failed;
+}
+
+bool PreFlightChecker::preFlightCheckVertVelFailed(const ekf2_innovations_s &innov, const float alpha)
+{
+	const float vel_d_innov = innov.vel_pos_innov[2];
+	const float vel_d_innov_lpf = _filter_vel_d_innov.update(vel_d_innov, alpha, _vel_innov_spike_lim);
+	return checkInnovFailed(vel_d_innov, vel_d_innov_lpf, _vel_innov_test_lim);
+}
+
+bool PreFlightChecker::preFlightCheckHeightFailed(const ekf2_innovations_s &innov, const float alpha)
+{
+	const float hgt_innov = innov.vel_pos_innov[5];
+	const float hgt_innov_lpf = _filter_hgt_innov.update(hgt_innov, alpha, _hgt_innov_spike_lim);
+	return checkInnovFailed(hgt_innov, hgt_innov_lpf, _hgt_innov_test_lim);
+}
+
+bool PreFlightChecker::checkInnovFailed(const float innov, const float innov_lpf, const float test_limit)
+{
+	return fabsf(innov_lpf) > test_limit || fabsf(innov) > 2.0f * test_limit;
+}
+
+bool PreFlightChecker::checkInnov2DFailed(const Vector2f &innov, const Vector2f &innov_lpf, const float test_limit)
+{
+	return innov_lpf.norm_squared() > sq(test_limit)
+	       || innov.norm_squared() > sq(2.0f * test_limit);
+}
+
+uint8_t PreFlightChecker::prefltFailBoolToBitMask(const bool heading_failed, const bool horiz_vel_failed,
+		const bool vert_vel_failed, const bool height_failed)
+{
+	return heading_failed | (horiz_vel_failed << 1) | (vert_vel_failed << 2) | (height_failed << 3);
+}
+
+void PreFlightChecker::reset()
+{
+	_is_using_gps_aiding = false;
+	_is_using_flow_aiding = false;
+	_is_using_ev_pos_aiding = false;
+	_has_heading_failed = false;
+	_has_horiz_vel_failed = false;
+	_has_vert_vel_failed = false;
+	_has_height_failed = false;
+	_filter_vel_n_innov.reset();
+	_filter_vel_e_innov.reset();
+	_filter_vel_d_innov.reset();
+	_filter_hgt_innov.reset();
+	_filter_heading_innov.reset();
+	_filter_flow_x_innov.reset();
+	_filter_flow_y_innov.reset();
+}
@@ -0,0 +1,182 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2019 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 PreFlightChecker.hpp
+ * Class handling the EKF2 innovation pre flight checks
+ *
+ * First call the update(...) function and then get the results
+ * using the hasXxxFailed() getters
+ */
+
+#pragma once
+
+#include <uORB/topics/vehicle_status.h>
+#include <uORB/topics/ekf2_innovations.h>
+
+#include <matrix/matrix/math.hpp>
+
+#include "InnovationLpf.hpp"
+
+using matrix::Vector2f;
+
+class PreFlightChecker
+{
+public:
+	PreFlightChecker() = default;
+	~PreFlightChecker() = default;
+
+	/*
+	 * Reset all the internal states of the class to their default value
+	 */
+	void reset();
+
+	/*
+	 * Update the internal states
+	 * @param dt the sampling time
+	 * @param innov the ekf2_innovation_s struct containing the current innovations
+	 */
+	void update(float dt, const ekf2_innovations_s &innov);
+
+	/*
+	 * If set to true, the checker will use a less conservative heading innovation check
+	 */
+	void setVehicleCanObserveHeadingInFlight(bool val) { _can_observe_heading_in_flight = val; }
+
+	void setUsingGpsAiding(bool val) { _is_using_gps_aiding = val; }
+	void setUsingFlowAiding(bool val) { _is_using_flow_aiding = val; }
+	void setUsingEvPosAiding(bool val) { _is_using_ev_pos_aiding = val; }
+
+	bool hasHeadingFailed() const { return _has_heading_failed; }
+	bool hasHorizVelFailed() const { return _has_horiz_vel_failed; }
+	bool hasVertVelFailed() const { return _has_vert_vel_failed; }
+	bool hasHeightFailed() const { return _has_height_failed; }
+
+	/*
+	 * Overall state of the pre fligh checks
+	 * @return true if any of the check failed
+	 */
+	bool hasFailed() const { return hasHorizFailed() || hasVertFailed(); }
+
+	/*
+	 * Horizontal checks overall result
+	 * @return true if one of the horizontal checks failed
+	 */
+	bool hasHorizFailed() const { return _has_heading_failed || _has_horiz_vel_failed; }
+
+	/*
+	 * Vertical checks overall result
+	 * @return true if one of the vertical checks failed
+	 */
+	bool hasVertFailed() const { return _has_vert_vel_failed || _has_height_failed; }
+
+	/*
+	 * Check if the innovation fails the test
+	 * To pass the test, the following conditions should be true:
+	 * innov <= test_limit
+	 * innov_lpf <= 2 * test_limit
+	 * @param innov the current unfiltered innovation
+	 * @param innov_lpf the low-pass filtered innovation
+	 * @param test_limit the magnitude test limit
+	 * @return true if the check failed the test, false otherwise
+	 */
+	static bool checkInnovFailed(float innov, float innov_lpf, float test_limit);
+
+	/*
+	 * Check if the a innovation of a 2D vector fails the test
+	 * To pass the test, the following conditions should be true:
+	 * innov <= test_limit
+	 * innov_lpf <= 2 * test_limit
+	 * @param innov the current unfiltered innovation
+	 * @param innov_lpf the low-pass filtered innovation
+	 * @param test_limit the magnitude test limit
+	 * @return true if the check failed the test, false otherwise
+	 */
+	static bool checkInnov2DFailed(const Vector2f &innov, const Vector2f &innov_lpf, float test_limit);
+
+	/*
+	 * Packs the boolean flags into a bit field
+	 */
+	static uint8_t prefltFailBoolToBitMask(bool heading_failed, bool horiz_vel_failed, bool vert_vel_failed,
+					       bool height_failed);
+
+	static constexpr float sq(float var) { return var * var; }
+
+private:
+	bool preFlightCheckHeadingFailed(const ekf2_innovations_s &innov, float alpha);
+	float selectHeadingTestLimit();
+
+	bool preFlightCheckHorizVelFailed(const ekf2_innovations_s &innov, float alpha);
+	bool preFlightCheckVertVelFailed(const ekf2_innovations_s &innov, float alpha);
+	bool preFlightCheckHeightFailed(const ekf2_innovations_s &innov, float alpha);
+
+	void resetPreFlightChecks();
+
+	bool _has_heading_failed{};
+	bool _has_horiz_vel_failed{};
+	bool _has_vert_vel_failed{};
+	bool _has_height_failed{};
+
+	bool _can_observe_heading_in_flight{};
+	bool _is_using_gps_aiding{};
+	bool _is_using_flow_aiding{};
+	bool _is_using_ev_pos_aiding{};
+
+	// Low-pass filters for innovation pre-flight checks
+	InnovationLpf _filter_vel_n_innov;	///< Preflight low pass filter N axis velocity innovations (m/sec)
+	InnovationLpf _filter_vel_e_innov;	///< Preflight low pass filter E axis velocity innovations (m/sec)
+	InnovationLpf _filter_vel_d_innov;	///< Preflight low pass filter D axis velocity innovations (m/sec)
+	InnovationLpf _filter_hgt_innov;	///< Preflight low pass filter height innovation (m)
+	InnovationLpf _filter_heading_innov;	///< Preflight low pass filter heading innovation magntitude (rad)
+	InnovationLpf _filter_flow_x_innov;	///< Preflight low pass filter optical flow innovation (rad)
+	InnovationLpf _filter_flow_y_innov;	///< Preflight low pass filter optical flow innovation (rad)
+
+	// Preflight low pass filter time constant inverse (1/sec)
+	static constexpr float _innov_lpf_tau_inv = 0.2f;
+	// Maximum permissible velocity innovation to pass pre-flight checks (m/sec)
+	static constexpr float _vel_innov_test_lim = 0.5f;
+	// Maximum permissible height innovation to pass pre-flight checks (m)
+	static constexpr float _hgt_innov_test_lim = 1.5f;
+	// Maximum permissible yaw innovation to pass pre-flight checks when aiding inertial nav using NE frame observations (rad)
+	static constexpr float _nav_heading_innov_test_lim = 0.25f;
+	// Maximum permissible yaw innovation to pass pre-flight checks when not aiding inertial nav using NE frame observations (rad)
+	static constexpr float _heading_innov_test_lim = 0.52f;
+	// Maximum permissible flow innovation to pass pre-flight checks
+	static constexpr float _flow_innov_test_lim = 0.1f;
+	// Preflight velocity innovation spike limit (m/sec)
+	static constexpr float _vel_innov_spike_lim = 2.0f * _vel_innov_test_lim;
+	// Preflight position innovation spike limit (m)
+	static constexpr float _hgt_innov_spike_lim = 2.0f * _hgt_innov_test_lim;
+	// Preflight flow innovation spike limit (rad)
+	static constexpr float _flow_innov_spike_lim = 2.0f * _flow_innov_test_lim;
+};
@@ -0,0 +1,108 @@
+/****************************************************************************
+ *
+ *   Copyright (C) 2019 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.
+ *
+ ****************************************************************************/
+
+/**
+ * Test code for PreFlightChecker class
+ * Run this test only using make tests TESTFILTER=PreFlightChecker
+ */
+
+#include <gtest/gtest.h>
+
+#include "PreFlightChecker.hpp"
+
+class PreFlightCheckerTest : public ::testing::Test
+{
+};
+
+TEST_F(PreFlightCheckerTest, testInnovFailed)
+{
+	const float test_limit = 1.0; ///< is the limit for innovation_lpf, the limit for innovation is 2*test_limit
+	const float innovations[9] = 	 {0.0, 1.5, 2.5, -1.5, -2.5, 1.5, -1.5, -2.5, -2.5};
+	const float innovations_lpf[9] = {0.0, 0.9, 0.9, -0.9, -0.9, 1.1, -1.1, -1.1, 1.1};
+	const bool expected_result[9] = {false, false, true, false, true, true, true, true, true};
+
+	for (int i = 0; i < 9; i++) {
+		EXPECT_EQ(PreFlightChecker::checkInnovFailed(innovations[i], innovations_lpf[i], test_limit), expected_result[i]);
+	}
+
+	// Smaller test limit, all the checks should fail except the first
+	EXPECT_FALSE(PreFlightChecker::checkInnovFailed(innovations[0], innovations_lpf[0], 0.0));
+
+	for (int i = 1; i < 9; i++) {
+		EXPECT_TRUE(PreFlightChecker::checkInnovFailed(innovations[i], innovations_lpf[i], 0.0));
+	}
+
+	// Larger test limit, none of the checks should fail
+	for (int i = 0; i < 9; i++) {
+		EXPECT_FALSE(PreFlightChecker::checkInnovFailed(innovations[i], innovations_lpf[i], 2.0));
+	}
+}
+
+TEST_F(PreFlightCheckerTest, testInnov2dFailed)
+{
+	const float test_limit = 1.0;
+	Vector2f innovations[4] = {{0.0, 0.0}, {0.0, 0.0}, {0.0, -2.5}, {1.5, -1.5}};
+	Vector2f innovations_lpf[4] = {{0.0, 0.0}, {1.1, 0.0}, {0.5, 0.5}, {1.0, -1.0}};
+	const bool expected_result[4] = {false, true, true, true};
+
+	for (int i = 0; i < 4; i++) {
+		EXPECT_EQ(PreFlightChecker::checkInnov2DFailed(innovations[i], innovations_lpf[i], test_limit), expected_result[i]);
+	}
+
+	// Smaller test limit, all the checks should fail except the first
+	EXPECT_FALSE(PreFlightChecker::checkInnov2DFailed(innovations[0], innovations_lpf[0], 0.0));
+
+	for (int i = 1; i < 4; i++) {
+		EXPECT_TRUE(PreFlightChecker::checkInnov2DFailed(innovations[i], innovations_lpf[i], 0.0));
+	}
+
+	// Larger test limit, none of the checks should fail
+	for (int i = 0; i < 4; i++) {
+		EXPECT_FALSE(PreFlightChecker::checkInnov2DFailed(innovations[i], innovations_lpf[i], 1.42));
+	}
+}
+
+TEST_F(PreFlightCheckerTest, testBitMask)
+{
+	PreFlightChecker preflt_checker;
+
+	const bool heading_failed = true;
+	const bool horiz_vel_failed = true;
+	const bool down_vel_failed = false;
+	const bool height_failed = true;
+
+	int bitmask = PreFlightChecker::prefltFailBoolToBitMask(heading_failed, horiz_vel_failed, down_vel_failed,
+			height_failed);
+
+	EXPECT_EQ(bitmask, 0b1011);
+}