Gazebo backend for NPS simulator NPS doc: http://wiki.paparazziuav.org/wiki/NPS Usage: 1. Make sure gazebo 9 is installed. (sudo apt-get install gazebo9 libgazebo9-dev) 2. Prepare the Gazebo world and model: 1. Prepare the UAV model (see conf/simulator/gazebo/models/ardrone/): - Place the aircraft model in the conf/simulator/gazebo/models/ folder, this folder is added to Gazebo’s search path when NPS is launched. - Gazebo uses a Front, Left, Up coordinate system for aircraft, so make sure the +x axis points forwards. - The model should include a link for each motor with the same names as those listed in NPS_ACTUATOR_NAMES (see below), e.g. ‘nw_motor’. - Camera links should have the name specified in .dev_name in the corresponding video_config_t struct, see sw/airborne/boards/pc_sim.h and sw/airborne/modules/computer_vision/video_thread_nps.c. 2. Prepare the world (see conf/simulator/gazebo/worlds/ardrone.world). Pay attention to the following: - The real-time update rate should be set to zero, as this is already handled by Paparazzi: @code{.xml} <physics type=”ode”> <max_step_size>0.001</max_step_size> <real_time_update_rate>0</real_time_update_rate><!– Handled by Paparazzi! –> </physics> @endcode - Spherical coordinates should be provided for navigation. At this moment, there is an issue where Gazebo incorrectly uses a WSU coordinate system instead of ENU. This can be fixed by setting the heading to 180 degrees as shown below: @code{.xml} <spherical_coordinates> <surface_model>EARTH_WGS84</surface_model> <latitude_deg>51.9906</latitude_deg> <longitude_deg>4.37679</longitude_deg> <elevation>0</elevation> <heading_deg>180</heading_deg><!– Temporary fix for issue https://bitbucket.org/osrf/gazebo/issues/2022/default-sphericalcoordinates-frame-should –> </spherical_coordinates> @endcode 3. Prepare the airframe file (see examples/ardrone2_gazebo.xml): 1. Select Gazebo as the FDM (Flight Dynamics Model) @code{.xml} <target name=”nps” board=”pc”> <module name=”fdm” type=”gazebo”/> </target> @endcode 2. Include the gazebo defines for the vehicle: @code{.xml} <section name=”SIMULATOR” prefix=”NPS_”> … </section> <include href=”conf/simulator/gazebo/airframes/ardrone2.xml”/> @endcode - If conf/simulator/gazebo/airframes does not contain an xml for the vehicle model, it should be created with the following contents: 1. Actuator thrusts and torques @code{.xml} <!DOCTYPE airframe SYSTEM “../../../airframes/airframe.dtd”> <airframe> <section name=”SIMULATOR” prefix=”NPS_”> <define name=”ACTUATOR_THRUSTS” value=”1.55, 1.55, 1.55, 1.55” type=”float[]”/> <define name=”ACTUATOR_TORQUES” value=”0.155, 0.155, 0.155, 0.155” type=”float[]”/> … </section> </airframe> @endcode The thrusts and torques are expressed in SI units (N, Nm) and should be in the same order as the ACTUATOR_NAMES defined in the airframe file. The torque direction is determined automatically from the motor mixing. 2. (Optional) Add actuator dynamics to the SIMULATOR section: @code{.xml} <section name=”SIMULATOR” prefix=”NPS_”> … <define name=”ACTUATOR_TIME_CONSTANTS” value=”0.02, 0.02, 0.02, 0.02” type=”float[]”/> <define name=”ACTUATOR_MAX_ANGULAR_MOMENTUM” value=”0.19, 0.19, 0.19, 0.19” type=”float[]”/> … </section> @endcode Actuator time constants can be provided without specifying the actuator’s maximum angular momentum. If the maximum angular momentum is provided as well, it is used to calculate the rotor spin-up torque. 3. In the same section, bypass the AHRS and INS as these are not supported yet: @code{.xml} <section name=”SIMULATOR” prefix=”NPS_”> … <define name=”BYPASS_AHRS” value=”1”/> <define name=”BYPASS_INS” value=”1”/> … </section> @endcode 4. If required, enable video thread simulation: @code{.xml} <section name=”SIMULATOR” prefix=”NPS_”> … <define name=”SIMULATE_VIDEO” value=”1”/> … </section> @endcode 5. Set the aircraft model in the xml file: @code{.xml} <section name=”SIMULATOR” prefix=”NPS_”> … <define name=”GAZEBO_AC_NAME” value=”my_uav”/> </section> @endcode 3. Make sure all included modules work with nps. At the moment, most of the modules that depend on video_thread are only built when ap is selected as the target. To fix this, add nps to the target attribute in the module xml, e.g.: @code{.xml} <makefile target=”ap|nps”> @endcode 4. The simulation environment is set in the flight plan file: @code{.xml} <flight_plan …> <header> … #define NPS_GAZEBO_WORLD “my.world” </header> … </flight_plan> @endcode







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