LandDetector: Added crude land detectors for multicopter and fixedwing

makefiles/config_px4fmu-v2_default.mk

@@ -72,6 +72,12 @@ MODULES		+= modules/mavlink
 MODULES		+= modules/gpio_led
 MODULES		+= modules/uavcan
 
+#
+# Vehicle land detection
+# 
+MODULES     += modules/mc_land_detector
+MODULES     += modules/fw_land_detector
+
 #
 # Estimation modules (EKF/ SO3 / other filters)
 #

src/modules/fw_land_detector/FixedwingLandDetector.cpp

@@ -0,0 +1,171 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2013-2015 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 FixedwingLandDetector.cpp
+ * Land detection algorithm for fixedwings
+ *
+ * @author Johan Jansen <jnsn.johan@gmail.com>
+ */
+
+#include "FixedwingLandDetector.h"
+
+#include <stdio.h>
+#include <math.h>
+#include <drivers/drv_hrt.h>
+#include <unistd.h>                 //usleep
+
+FixedwingLandDetector::FixedwingLandDetector() :
+    _landDetectedPub(-1),
+    _landDetected({0,false}),
+    
+    _vehicleLocalPositionSub(-1),
+    _vehicleLocalPosition({}),
+    _airspeedSub(-1),
+    _airspeed({}),
+
+    _velocity_xy_filtered(0.0f),
+    _velocity_z_filtered(0.0f),
+    _airspeed_filtered(0.0f),
+    _landDetectTrigger(0),
+
+    _taskShouldExit(false),
+    _taskIsRunning(false)
+{
+    //Advertise the first land detected uORB
+    _landDetected.timestamp = hrt_absolute_time();
+    _landDetected.landed = false;
+    _landDetectedPub = orb_advertise(ORB_ID(vehicle_land_detected), &_landDetected);
+}
+
+FixedwingLandDetector::~FixedwingLandDetector()
+{
+    _taskShouldExit = true;
+    close(_landDetectedPub);
+ }
+
+void FixedwingLandDetector::shutdown()
+{
+    _taskShouldExit = true;
+}
+
+/**
+* @brief Convinience function for polling uORB subscriptions
+* @return true if there was new data and it was successfully copied
+**/
+static bool orb_update(const struct orb_metadata *meta, int handle, void *buffer)
+{
+    bool newData = false;
+
+    //Check if there is new data to grab
+    if(orb_check(handle, &newData) != OK) {
+        return false;
+    }
+
+    if(!newData) {
+        return false;
+    }
+
+    if(orb_copy(meta, handle, buffer) != OK) {
+        return false;
+    }
+
+    return true;
+}
+
+void FixedwingLandDetector::updateSubscriptions()
+{
+    orb_update(ORB_ID(vehicle_local_position), _vehicleLocalPositionSub, &_vehicleLocalPosition);
+    orb_update(ORB_ID(airspeed), _airspeedSub, &_airspeed);
+}
+
+void FixedwingLandDetector::landDetectorLoop()
+{
+    //This should never happen!
+    if(_taskIsRunning) return;
+
+    //Subscribe to local position and airspeed data
+    _vehicleLocalPositionSub = orb_subscribe(ORB_ID(vehicle_local_position));
+    _airspeedSub = orb_subscribe(ORB_ID(airspeed));
+
+    _taskIsRunning = true;
+    _taskShouldExit = false;
+    while (!_taskShouldExit) {
+
+        //First poll for new data from our subscriptions
+        updateSubscriptions();
+
+        const uint64_t now = hrt_absolute_time();
+        bool landDetected = false;
+
+        //TODO: reset filtered values on arming?
+        _velocity_xy_filtered = 0.95f*_velocity_xy_filtered + 0.05f*sqrtf(_vehicleLocalPosition.vx*_vehicleLocalPosition.vx + _vehicleLocalPosition.vy*_vehicleLocalPosition.vy);
+        _velocity_z_filtered = 0.95f*_velocity_z_filtered + 0.05f*fabsf(_vehicleLocalPosition.vz);
+        _airspeed_filtered = 0.95f*_airspeed_filtered + 0.05f*_airspeed.true_airspeed_m_s;
+
+        /* crude land detector for fixedwing */
+        if (_velocity_xy_filtered < FW_LAND_DETECTOR_VELOCITY_MAX 
+            && _velocity_z_filtered < FW_LAND_DETECTOR_CLIMBRATE_MAX 
+            && _airspeed_filtered < FW_LAND_DETECTOR_AIRSPEED_MAX) {
+
+            //These conditions need to be stable for a period of time before we trust them
+            if(now > _landDetectTrigger) {
+                landDetected = true;
+            }
+        }
+        else {
+            //reset land detect trigger
+            _landDetectTrigger = now + FW_LAND_DETECTOR_TRIGGER_TIME;
+        }
+
+        //Publish if land detection state has changed
+        if(_landDetected.landed != landDetected) {
+            _landDetected.timestamp = now;
+            _landDetected.landed = landDetected;
+
+            /* publish the land detected broadcast */
+            orb_publish(ORB_ID(vehicle_land_detected), _landDetectedPub, &_landDetected);
+        }
+
+        //Limit loop rate
+        usleep(1000000 / FW_LAND_DETECTOR_UPDATE_RATE);
+    }
+
+    _taskIsRunning = false;
+    _exit(0);
+}
+
+bool FixedwingLandDetector::isRunning() const
+{
+    return _taskIsRunning;
+}

src/modules/fw_land_detector/FixedwingLandDetector.h

@@ -0,0 +1,107 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2013-2015 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 FixedwingLandDetector.h
+ * Land detection algorithm for multicopters
+ *
+ * @author Johan Jansen <jnsn.johan@gmail.com>
+ * @author Morten Lysgaard <Morten@mycptr.com>
+ */
+
+#ifndef __FIXED_WING_LAND_DETECTOR_H__
+#define __FIXED_WING_LAND_DETECTOR_H__
+
+#include <uORB/uORB.h>
+#include <uORB/topics/vehicle_land_detected.h>
+#include <uORB/topics/vehicle_local_position.h>
+#include <uORB/topics/airspeed.h>
+
+class FixedwingLandDetector {
+public:
+        FixedwingLandDetector();
+        ~FixedwingLandDetector();
+
+        /**
+        * @brief Executes the main loop of the land detector in a separate deamon thread
+        * @returns OK if task was successfully launched
+        **/
+        int createDeamonThread();
+
+        /**
+        * @returns true if this task is currently running
+        **/
+        bool isRunning() const;
+
+        /**
+        * @brief  blocking loop, should be run in a separate thread or task. Runs at 50Hz
+        **/
+        void landDetectorLoop();
+
+        /**
+        * @brief  Tells the Land Detector task that it should exit
+        **/
+        void shutdown();
+
+protected:
+        /**
+        * @brief  polls all subscriptions and pulls any data that has changed
+        **/
+        void updateSubscriptions();
+
+        //Algorithm parameters (TODO: should probably be externalized)
+        static constexpr uint32_t FW_LAND_DETECTOR_UPDATE_RATE = 50;        /**< Run algorithm at 50Hz */
+        static constexpr uint64_t FW_LAND_DETECTOR_TRIGGER_TIME = 2000000;  /**< usec that landing conditions have to hold before triggering a land */
+        static constexpr float FW_LAND_DETECTOR_VELOCITY_MAX = 5.0f;        /**< maximum horizontal movement m/s*/
+        static constexpr float FW_LAND_DETECTOR_CLIMBRATE_MAX = 10.00f;     /**< +- climb rate in m/s*/
+        static constexpr float FW_LAND_DETECTOR_AIRSPEED_MAX = 10.00f;      /**< airspeed max m/s*/
+
+private:
+        orb_advert_t                            _landDetectedPub;           /**< publisher for position in local frame */
+        struct vehicle_land_detected_s          _landDetected;              /**< local vehicle position */
+
+        int                                     _vehicleLocalPositionSub;   /**< notification of local position */
+        struct vehicle_local_position_s         _vehicleLocalPosition;      /**< the result from local position subscription */
+        int                                     _airspeedSub;
+        struct airspeed_s                       _airspeed;
+
+        float _velocity_xy_filtered;
+        float _velocity_z_filtered;
+        float _airspeed_filtered;
+        uint64_t _landDetectTrigger;
+        
+        bool _taskShouldExit;                                               /**< true if it is requested that this task should exit */
+        bool _taskIsRunning;                                                /**< task has reached main loop and is currently running */
+};
+
+#endif //__FIXED_WING_LAND_DETECTOR_H__

src/modules/fw_land_detector/fw_land_detector_main.cpp

@@ -0,0 +1,195 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2013-2015 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 fw_land_detector_main.cpp
+ * Land detection algorithm for fixed wings
+ *
+ * @author Johan Jansen <jnsn.johan@gmail.com>
+ */
+
+#include <unistd.h>                 //usleep
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <drivers/drv_hrt.h>
+#include <systemlib/systemlib.h>    //Scheduler
+#include <systemlib/err.h>          //print to console
+
+#include "FixedwingLandDetector.h"
+
+//Function prototypes
+static int fw_land_detector_start();
+static void fw_land_detector_stop();
+
+/**
+ * land detector app start / stop handling function
+ * This makes the land detector module accessible from the nuttx shell
+ * @ingroup apps
+ */
+extern "C" __EXPORT int fw_land_detector_main(int argc, char *argv[]);
+
+//Private variables
+static FixedwingLandDetector* fw_land_detector_task = nullptr;
+static int _landDetectorTaskID = -1;
+
+/**
+* Deamon thread function
+**/
+static void fw_land_detector_deamon_thread(int argc, char *argv[])
+{
+    fw_land_detector_task->landDetectorLoop();
+}
+
+/**
+* Stop the task, force killing it if it doesn't stop by itself
+**/
+static void fw_land_detector_stop()
+{
+    if(fw_land_detector_task == nullptr || _landDetectorTaskID == -1) {
+        errx(1, "not running");
+        return;
+    }
+
+    fw_land_detector_task->shutdown();
+
+    //Wait for task to die
+    int i = 0;
+    do {
+        /* wait 20ms */
+        usleep(20000);
+
+        /* if we have given up, kill it */
+        if (++i > 50) {
+            task_delete(_landDetectorTaskID);
+            break;
+        }
+    } while (fw_land_detector_task->isRunning());
+
+
+    delete fw_land_detector_task;
+    fw_land_detector_task = nullptr;
+    _landDetectorTaskID = -1;
+    warn("fw_land_detector has been stopped");
+}
+
+/**
+* Start new task, fails if it is already running. Returns OK if successful
+**/
+static int fw_land_detector_start()
+{
+    if(fw_land_detector_task != nullptr || _landDetectorTaskID != -1) {
+        errx(1, "already running");
+        return -1;
+    }
+
+    //Allocate memory
+    fw_land_detector_task = new FixedwingLandDetector();
+    if (fw_land_detector_task == nullptr) {
+        errx(1, "alloc failed");
+        return -1;
+    }
+
+    //Start new thread task
+    _landDetectorTaskID = task_spawn_cmd("fw_land_detector",
+                     SCHED_DEFAULT,
+                     SCHED_PRIORITY_DEFAULT,
+                     1024,
+                     (main_t)&fw_land_detector_deamon_thread,
+                     nullptr);
+
+    if (_landDetectorTaskID < 0) {
+        errx(1, "task start failed: %d", -errno);
+        return -1;
+    }
+
+    /* avoid memory fragmentation by not exiting start handler until the task has fully started */
+    const uint32_t timeout = hrt_absolute_time() + 5000000; //5 second timeout
+    while (!fw_land_detector_task->isRunning()) {
+        usleep(50000);
+        printf(".");
+        fflush(stdout);
+
+        if(hrt_absolute_time() > timeout) {
+            err(1, "start failed - timeout");
+            fw_land_detector_stop();
+            exit(1);
+        }
+    }
+    printf("\n");
+
+    exit(0);
+    return 0;
+}
+
+/**
+* Main entry point for this module
+**/
+int fw_land_detector_main(int argc, char *argv[])
+{
+
+    if (argc < 1) {
+        warnx("usage: fw_land_detector {start|stop|status}");
+        exit(0);
+    }
+
+    if (!strcmp(argv[1], "start")) {
+        fw_land_detector_start();
+    }
+
+    if (!strcmp(argv[1], "stop")) {
+        fw_land_detector_stop();
+        exit(0);    
+    }
+
+    if (!strcmp(argv[1], "status")) {
+        if (fw_land_detector_task) {
+
+            if(fw_land_detector_task->isRunning()) {
+                warnx("running");
+            }
+            else {
+                errx(1, "exists, but not running");
+            }
+
+            exit(0);
+
+        } else {
+            errx(1, "not running");
+        }
+    }
+
+    warn("usage: fw_land_detector {start|stop|status}");
+    return 1;
+}

src/modules/fw_land_detector/module.mk

@@ -0,0 +1,10 @@
+#
+# Fixedwing land detector
+#
+
+MODULE_COMMAND  = fw_land_detector
+
+SRCS        = fw_land_detector_main.cpp \
+              FixedwingLandDetector.cpp
+
+EXTRACXXFLAGS   = -Weffc++

src/modules/mc_land_detector/MulticopterLandDetector.cpp

@@ -0,0 +1,212 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2013-2015 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 MultiCopterLandDetector.cpp
+ * Land detection algorithm for multicopters
+ *
+ * @author Johan Jansen <jnsn.johan@gmail.com>
+ * @author Morten Lysgaard <morten@lysgaard.no>
+ */
+
+#include "MulticopterLandDetector.h"
+
+#include <stdio.h>
+#include <cmath>
+#include <drivers/drv_hrt.h>
+#include <unistd.h>                 //usleep
+
+MulticopterLandDetector::MulticopterLandDetector() :
+    _landDetectedPub(-1),
+    _landDetected({0,false}),
+    
+    _vehicleGlobalPositionSub(-1),
+    _sensorsCombinedSub(-1),
+    _waypointSub(-1),
+    _actuatorsSub(-1),
+    _armingSub(-1),
+
+    _vehicleGlobalPosition({}),
+    _sensors({}),
+    _waypoint({}),
+    _actuators({}),
+    _arming({}),
+
+    _taskShouldExit(false),
+    _taskIsRunning(false),
+    _landTimer(0)
+{
+    //Advertise the first land detected uORB
+    _landDetected.timestamp = hrt_absolute_time();
+    _landDetected.landed = false;
+    _landDetectedPub = orb_advertise(ORB_ID(vehicle_land_detected), &_landDetected);
+}
+
+MulticopterLandDetector::~MulticopterLandDetector()
+{
+    _taskShouldExit = true;
+    close(_landDetectedPub);
+}
+
+/**
+* @brief Convinience function for polling uORB subscriptions
+* @return true if there was new data and it was successfully copied
+**/
+static bool orb_update(const struct orb_metadata *meta, int handle, void *buffer)
+{
+    bool newData = false;
+
+    //Check if there is new data to grab
+    if(orb_check(handle, &newData) != OK) {
+        return false;
+    }
+
+    if(!newData) {
+        return false;
+    }
+
+    if(orb_copy(meta, handle, buffer) != OK) {
+        return false;
+    }
+
+    return true;
+}
+
+void MulticopterLandDetector::shutdown()
+{
+    _taskShouldExit = true;
+}
+
+void MulticopterLandDetector::updateSubscriptions()
+{
+    orb_update(ORB_ID(vehicle_global_position), _vehicleGlobalPositionSub, &_vehicleGlobalPosition);
+    orb_update(ORB_ID(sensor_combined), _sensorsCombinedSub, &_sensors);
+    orb_update(ORB_ID(position_setpoint_triplet), _waypointSub, &_waypoint);
+    orb_update(ORB_ID_VEHICLE_ATTITUDE_CONTROLS, _actuatorsSub, &_actuators);
+    orb_update(ORB_ID(actuator_armed), _armingSub, &_arming);
+}
+
+void MulticopterLandDetector::landDetectorLoop()
+{
+    //This should never happen!
+    if(_taskIsRunning) return;
+
+    //Subscribe to position, attitude, arming and velocity changes
+    _vehicleGlobalPositionSub = orb_subscribe(ORB_ID(vehicle_global_position));
+    _sensorsCombinedSub = orb_subscribe(ORB_ID(sensor_combined));
+    _waypointSub = orb_subscribe(ORB_ID(position_setpoint_triplet));
+    _actuatorsSub = orb_subscribe(ORB_ID_VEHICLE_ATTITUDE_CONTROLS);
+    _armingSub = orb_subscribe(ORB_ID(actuator_armed));
+
+    //Begin task
+    _taskIsRunning = true;
+    _taskShouldExit = false;
+    while (!_taskShouldExit) {
+
+        //First poll for new data from our subscriptions
+        updateSubscriptions();
+
+        const uint64_t now = hrt_absolute_time();
+
+        //only detect landing if the autopilot is actively trying to land
+        if(!_waypoint.current.valid || _waypoint.current.type != SETPOINT_TYPE_LAND) {
+            _landTimer = now;
+        }
+        else {
+            /*
+            static int debugcnt = 0;
+            if(debugcnt++ > 12) {
+                debugcnt = 0;
+                mavlink_log_critical(_mavlinkFd, "T: %.4f   R: %.4f", (double)_actuators.control[3], 
+                    sqrt( _sensors.gyro_rad_s[0]*_sensors.gyro_rad_s[0]+
+                          _sensors.gyro_rad_s[1]*_sensors.gyro_rad_s[1]+
+                          _sensors.gyro_rad_s[2]*_sensors.gyro_rad_s[2]));
+            }
+            */
+
+            //Check if we are moving vertically
+            bool verticalMovement = fabsf(_vehicleGlobalPosition.vel_d) > MC_LAND_DETECTOR_CLIMBRATE_MAX;
+
+            bool horizontalMovement = sqrtf(_vehicleGlobalPosition.vel_n*_vehicleGlobalPosition.vel_n 
+                + _vehicleGlobalPosition.vel_e*_vehicleGlobalPosition.vel_e) > MC_LAND_DETECTOR_VELOCITY_MAX;
+
+            //Next look if all rotation angles are not moving
+            bool rotating = sqrtf(_sensors.gyro_rad_s[0]*_sensors.gyro_rad_s[0]+
+                          _sensors.gyro_rad_s[1]*_sensors.gyro_rad_s[1]+
+                          _sensors.gyro_rad_s[2]*_sensors.gyro_rad_s[2]) > MC_LAND_DETECTOR_ROTATION_MAX;
+
+            //Check if thrust output is minimal (about half of default)
+            bool minimalThrust = _arming.armed && _actuators.control[3] <= MC_LAND_DETECTOR_THRUST_MAX;
+
+            if(verticalMovement || rotating || !minimalThrust || horizontalMovement) {
+                //Sensed movement, so reset the land detector
+                _landTimer = now;
+            }
+
+        }
+
+        // if we have detected a landing for 2 continious seconds
+        if(now-_landTimer > 2000000) {
+            if(!_landDetected.landed)
+            {
+                _landDetected.timestamp = now;
+                _landDetected.landed = true;
+
+                /* publish the land detected broadcast */
+                orb_publish(ORB_ID(vehicle_land_detected), _landDetectedPub, &_landDetected);
+            }
+        }
+        else {
+            // if we currently think we have landed, but the latest data says we are flying
+            if(_landDetected.landed)
+            {
+                _landDetected.timestamp = now;
+                _landDetected.landed = false;
+
+                /* publish the land detected broadcast */
+                orb_publish(ORB_ID(vehicle_land_detected), _landDetectedPub, &_landDetected);
+            }
+        }
+
+        //Limit loop rate
+        usleep(1000000 / MC_LAND_DETECTOR_UPDATE_RATE);
+    }
+
+    _taskIsRunning = false;
+    _exit(0);
+}
+
+bool MulticopterLandDetector::isRunning() const
+{
+    return _taskIsRunning;
+}

src/modules/mc_land_detector/MulticopterLandDetector.h

@@ -0,0 +1,116 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2013-2015 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 MultiCopterLandDetector.h
+ * Land detection algorithm for multicopters
+ *
+ * @author Johan Jansen <jnsn.johan@gmail.com>
+ * @author Morten Lysgaard <Morten@mycptr.com>
+ */
+
+#ifndef __MULTICOPTER_LAND_DETECTOR_H__
+#define __MULTICOPTER_LAND_DETECTOR_H__
+
+#include <uORB/uORB.h>
+#include <uORB/topics/vehicle_land_detected.h>
+#include <uORB/topics/vehicle_global_position.h>
+#include <uORB/topics/sensor_combined.h>
+#include <uORB/topics/position_setpoint_triplet.h>
+#include <uORB/topics/actuator_controls.h>
+#include <uORB/topics/actuator_armed.h>
+
+//TODO: add crash detection to this module?
+class MulticopterLandDetector {
+public:
+        MulticopterLandDetector();
+        ~MulticopterLandDetector();
+
+        /**
+        * @brief Executes the main loop of the land detector in a separate deamon thread
+        * @returns OK if task was successfully launched
+        **/
+        int createDeamonThread();
+
+        /**
+        * @returns true if this task is currently running
+        **/
+        bool isRunning() const;
+
+        /**
+        * @brief  blocking loop, should be run in a separate thread or task. Runs at 50Hz
+        **/
+        void landDetectorLoop();
+
+        /**
+        * @brief  Tells the Land Detector task that it should exit
+        **/
+        void shutdown();
+
+protected:
+        /**
+        * @brief  polls all subscriptions and pulls any data that has changed
+        **/
+        void updateSubscriptions();
+
+        //Algorithm parameters (TODO: should probably be externalized)
+        static constexpr float MC_LAND_DETECTOR_CLIMBRATE_MAX = 0.30f;      /**< max +- climb rate in m/s */
+        static constexpr float MC_LAND_DETECTOR_ROTATION_MAX = 0.5f;        /**< max rotation in rad/sec (= 30 deg/s) */
+        static constexpr float MC_LAND_DETECTOR_THRUST_MAX = 0.2f;
+        static constexpr float MC_LAND_DETECTOR_VELOCITY_MAX = 1.0f;        /**< max +- horizontal movement in m/s */
+        static constexpr uint32_t MC_LAND_DETECTOR_UPDATE_RATE = 50;        /**< Run algorithm at 50Hz */
+        static constexpr uint32_t MC_LAND_DETECTOR_TRIGGER_TIME = 2000000;  /**< usec that landing conditions have to hold before triggering a land */
+
+private:
+        orb_advert_t                            _landDetectedPub;           /**< publisher for position in local frame */
+        struct vehicle_land_detected_s          _landDetected;              /**< local vehicle position */
+
+        int _vehicleGlobalPositionSub;                                      /**< notification of global position */
+        int _sensorsCombinedSub;
+        int _waypointSub;
+        int _actuatorsSub;
+        int _armingSub;
+
+        struct vehicle_global_position_s          _vehicleGlobalPosition;   /**< the result from global position subscription */
+        struct sensor_combined_s                  _sensors;                 /**< subscribe to sensor readings */
+        struct position_setpoint_triplet_s        _waypoint;                /**< subscribe to autopilot navigation */
+        struct actuator_controls_s                _actuators;
+        struct actuator_armed_s                   _arming;
+        
+        bool _taskShouldExit;                                               /**< true if it is requested that this task should exit */
+        bool _taskIsRunning;                                                /**< task has reached main loop and is currently running */
+
+        uint64_t _landTimer;                                                /**< timestamp in microseconds since a possible land was detected*/
+};
+
+#endif //__MULTICOPTER_LAND_DETECTOR_H__

src/modules/mc_land_detector/mc_land_detector_main.cpp

@@ -0,0 +1,195 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2013-2015 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 mc_land_detector_main.cpp
+ * Land detection algorithm for multicopters
+ *
+ * @author Johan Jansen <jnsn.johan@gmail.com>
+ */
+
+#include <unistd.h>					//usleep
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <drivers/drv_hrt.h>
+#include <systemlib/systemlib.h>	//Scheduler
+#include <systemlib/err.h>			//print to console
+
+#include "MulticopterLandDetector.h"
+
+//Function prototypes
+static int mc_land_detector_start();
+static void mc_land_detector_stop();
+
+/**
+ * land detector app start / stop handling function
+ * This makes the land detector module accessible from the nuttx shell
+ * @ingroup apps
+ */
+extern "C" __EXPORT int mc_land_detector_main(int argc, char *argv[]);
+
+//Private variables
+static MulticopterLandDetector* mc_land_detector_task = nullptr;
+static int _landDetectorTaskID = -1;
+
+/**
+* Deamon thread function
+**/
+static void mc_land_detector_deamon_thread(int argc, char *argv[])
+{
+	mc_land_detector_task->landDetectorLoop();
+}
+
+/**
+* Stop the task, force killing it if it doesn't stop by itself
+**/
+static void mc_land_detector_stop()
+{
+	if(mc_land_detector_task == nullptr || _landDetectorTaskID == -1) {
+		errx(1, "not running");
+		return;
+	}
+
+	mc_land_detector_task->shutdown();
+
+	//Wait for task to die
+	int i = 0;
+	do {
+		/* wait 20ms */
+		usleep(20000);
+
+		/* if we have given up, kill it */
+		if (++i > 50) {
+			task_delete(_landDetectorTaskID);
+			break;
+		}
+	} while (mc_land_detector_task->isRunning());
+
+
+	delete mc_land_detector_task;
+	mc_land_detector_task = nullptr;
+	_landDetectorTaskID = -1;
+	warn("mc_land_detector has been stopped");
+}
+
+/**
+* Start new task, fails if it is already running. Returns OK if successful
+**/
+static int mc_land_detector_start()
+{
+	if(mc_land_detector_task != nullptr || _landDetectorTaskID != -1) {
+		errx(1, "already running");
+		return -1;
+	}
+
+	//Allocate memory
+	mc_land_detector_task = new MulticopterLandDetector();
+	if (mc_land_detector_task == nullptr) {
+		errx(1, "alloc failed");
+		return -1;
+	}
+
+	//Start new thread task
+	_landDetectorTaskID = task_spawn_cmd("mc_land_detector",
+					 SCHED_DEFAULT,
+					 SCHED_PRIORITY_DEFAULT,
+					 1024,
+					 (main_t)&mc_land_detector_deamon_thread,
+					 nullptr);
+
+	if (_landDetectorTaskID < 0) {
+		errx(1, "task start failed: %d", -errno);
+		return -1;
+	}
+
+	/* avoid memory fragmentation by not exiting start handler until the task has fully started */
+	const uint32_t timeout = hrt_absolute_time() + 5000000; //5 second timeout
+	while (!mc_land_detector_task->isRunning()) {
+		usleep(50000);
+		printf(".");
+		fflush(stdout);
+
+		if(hrt_absolute_time() > timeout) {
+			err(1, "start failed - timeout");
+			mc_land_detector_stop();
+			exit(1);
+		}
+	}
+	printf("\n");
+
+	exit(0);
+	return 0;
+}
+
+/**
+* Main entry point for this module
+**/
+int mc_land_detector_main(int argc, char *argv[])
+{
+
+	if (argc < 1) {
+		warnx("usage: mc_land_detector {start|stop|status}");
+		exit(0);
+	}
+
+	if (!strcmp(argv[1], "start")) {
+		mc_land_detector_start();
+	}
+
+	if (!strcmp(argv[1], "stop")) {
+		mc_land_detector_stop();
+		exit(0);	
+	}
+
+	if (!strcmp(argv[1], "status")) {
+		if (mc_land_detector_task) {
+
+			if(mc_land_detector_task->isRunning()) {
+				warnx("running");
+			}
+			else {
+				errx(1, "exists, but not running");
+			}
+
+			exit(0);
+
+		} else {
+			errx(1, "not running");
+		}
+	}
+
+	warn("usage: mc_land_detector {start|stop|status}");
+	return 1;
+}

src/modules/mc_land_detector/module.mk

@@ -0,0 +1,10 @@
+#
+# Multirotor land detector
+#
+
+MODULE_COMMAND	= mc_land_detector
+
+SRCS		= mc_land_detector_main.cpp \
+			  MulticopterLandDetector.cpp
+
+EXTRACXXFLAGS   = -Weffc++