Add pure pursuit library

src/lib/CMakeLists.txt

@@ -64,6 +64,7 @@ add_subdirectory(perf EXCLUDE_FROM_ALL)
 add_subdirectory(fw_performance_model EXCLUDE_FROM_ALL)
 add_subdirectory(pid EXCLUDE_FROM_ALL)
 add_subdirectory(pid_design EXCLUDE_FROM_ALL)
+add_subdirectory(pure_pursuit EXCLUDE_FROM_ALL)
 add_subdirectory(rate_control EXCLUDE_FROM_ALL)
 add_subdirectory(rc EXCLUDE_FROM_ALL)
 add_subdirectory(ringbuffer EXCLUDE_FROM_ALL)

src/lib/pure_pursuit/CMakeLists.txt

@@ -0,0 +1,39 @@
+############################################################################
+#
+#   Copyright (c) 2024 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(pure_pursuit
+	PurePursuit.cpp
+	PurePursuit.hpp
+)
+
+px4_add_unit_gtest(SRC PurePursuitTest.cpp LINKLIBS pure_pursuit)

src/lib/pure_pursuit/PurePursuit.cpp

@@ -0,0 +1,75 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2024 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.
+ *
+ ****************************************************************************/
+
+#include "PurePursuit.hpp"
+#include <mathlib/mathlib.h>
+
+float PurePursuit::calcDesiredHeading(const Vector2f &curr_wp_ned, const Vector2f &prev_wp_ned,
+				      const Vector2f &curr_pos_ned,
+				      const float lookahead_distance)
+{
+	// Check input validity
+	if (!curr_wp_ned.isAllFinite() || !curr_pos_ned.isAllFinite() || lookahead_distance < FLT_EPSILON
+	    || !PX4_ISFINITE(lookahead_distance) || !prev_wp_ned.isAllFinite()) {
+		return NAN;
+	}
+
+	// Pure pursuit
+	const Vector2f curr_pos_to_curr_wp = curr_wp_ned - curr_pos_ned;
+	const Vector2f prev_wp_to_curr_wp = curr_wp_ned - prev_wp_ned;
+
+	if (curr_pos_to_curr_wp.norm() < lookahead_distance
+	    || prev_wp_to_curr_wp.norm() <
+	    FLT_EPSILON) { // Target current waypoint if closer to it than lookahead or waypoints overlap
+		return atan2f(curr_pos_to_curr_wp(1), curr_pos_to_curr_wp(0));
+	}
+
+	const Vector2f prev_wp_to_curr_pos = curr_pos_ned - prev_wp_ned;
+	const Vector2f prev_wp_to_curr_wp_u = prev_wp_to_curr_wp.unit_or_zero();
+	const Vector2f distance_on_line_segment = (prev_wp_to_curr_pos * prev_wp_to_curr_wp_u) *
+			prev_wp_to_curr_wp_u; // Projection of prev_wp_to_curr_pos onto prev_wp_to_curr_wp
+	const Vector2f curr_pos_to_path = distance_on_line_segment -
+					  prev_wp_to_curr_pos; // Shortest vector from the current position to the path
+
+	if (curr_pos_to_path.norm() > lookahead_distance) { // Target closest point on path if there is no intersection point
+		return atan2f(curr_pos_to_path(1), curr_pos_to_path(0));
+	}
+
+	const float line_extension = sqrt(powf(lookahead_distance, 2.f) - powf(curr_pos_to_path.norm(),
+					  2.f)); // Length of the vector from the endpoint of distance_on_line_segment to the intersection point
+	const Vector2f prev_wp_to_intersection_point = distance_on_line_segment + line_extension *
+			prev_wp_to_curr_wp_u;
+	const Vector2f curr_pos_to_intersection_point = prev_wp_to_intersection_point - prev_wp_to_curr_pos;
+	return atan2f(curr_pos_to_intersection_point(1), curr_pos_to_intersection_point(0));
+
+}

src/lib/pure_pursuit/PurePursuit.hpp

@@ -0,0 +1,91 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2024 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.
+ *
+ ****************************************************************************/
+
+#include <matrix/math.hpp>
+
+using namespace matrix;
+
+/**
+ * @file PurePursuit.hpp
+ *
+ * Implementation of pure pursuit guidance logic.
+ *
+ * Acknowledgements and References:
+ *
+ *    This implementation has been built for PX4 based on the idea from [1] (not including any code).
+ *
+ *    [1] Coulter, R. C. (1992). Implementation of the Pure Pursuit Path Tracking Algorithm
+ * 	  (Techreport CMU-RI-TR-92-01).
+ *
+ * Pure pursuit is a path following algorithm that uses the intersection between the path and
+ * a circle (the radius of which is referred to as lookahead distance) around the vehicle as
+ * the target point for the vehicle.
+ * 							C
+ * 		  				       /
+ * 						    __/__
+ * 						  /  /    \
+ * 						 /  /      \
+ * 						|  /  V     |
+ * 						 \/        /
+ * 						 /\ _____ /
+ * 	         	    N (0 rad)		/
+ * 			        ^	       P
+ * 				|
+ * 				| D
+ *  	   (-1.5708 rad) <----- ⨂ -----> E (1.5708 rad)
+ * 				|
+ * 				|
+ * 				⌄
+ * 			(+- 3.14159 rad)
+ *
+ * Input:  Current/prev waypoint and the vehicle position in NED frame as well as the lookahead distance.
+ * Output: Calculates the intersection points and returns the heading towards the point that is closer to the current waypoint.
+ */
+class PurePursuit
+{
+public:
+	/**
+	 * @brief Return heading towards the intersection point between a circle with a radius of
+	 * lookahead_distance around the vehicle and an extended line segment from the previous to the current waypoint.
+	 * Exceptions:
+	 * 	Will return heading towards the current waypoint if it is closer to the vehicle than the lookahead.
+	 * 	Will return heading towards the closest point on the path if there are no intersection points (crosstrack error bigger than lookahead).
+	 * 	Will return NAN if input is invalid.
+	 * @param curr_wp_ned North/East coordinates of current waypoint in NED frame [m].
+	 * @param prev_wp_ned North/East coordinates of previous waypoint in NED frame [m].
+	 * @param curr_pos_ned North/East coordinates of current position of the vehicle in NED frame [m].
+	 * @param lookahead_distance Radius of circle around vehicle [m].
+	 */
+	float calcDesiredHeading(const Vector2f &curr_wp_ned, const Vector2f &prev_wp_ned, const Vector2f &curr_pos_ned,
+				 const float lookahead_distance);
+};