Gazebo
The nice sim framework Gazebo from here http://gazebosim.org/ can now be use from within Paparazzi. Are you doing work on UAS in combination with e.g. Vision based navigation? Then check it out. I might make testing your new work so much simpler.
Be warned, using it can be highly addictive, and might tempt you into buying a new computer with high specifications. To be able to use Gazebo a very good Video card is needed, consider upgrading you hardware if everything runs slowly.
Note that from stable version 5.14 onwards, only version 8 and 9 of Gazebo work in Paparazzi on Ubuntu 16.04 or higher.
Installation
Make sure Gazebo is installed, version 9 if you are on Ubuntu 18 and higher
sudo apt install gazebo9 libgazebo9-dev
If for some reason this doesn’t work, you can find some additional instructions here: http://gazebosim.org/tutorials?cat=install&tut=install_ubuntu&ver=9.0
Setup and Configure
This section shows what and how to configure to run a simulation in Gazebo through paparazzi.
Vehicle Model
Prepare your Gazebo aircraft model (example see conf/simulator/gazebo/models/ardrone/
):
Place the aircraft model in the conf/simulator/gazebo/models/
folder, this folder is added to the search path of Gazebo 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
Additional models can be found in the sw/ext/tudelft_gazebo_models
. You will have to run git submodule init
, git submodule update
to pull in the models.
World
Prepare the world (see conf/simulator/gazebo/worlds/ardrone.world or any other world file you might find there).
Note
The real-time update rate should be set to zero, as the simulation back-end is already handled by Paparazzi:
<physics type="ode">
<max_step_size>0.001</max_step_size>
<real_time_update_rate>0</real_time_update_rate><!-- Handled by Paparazzi! -->
</physics>
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:
<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>
Additional world models can be found in the sw/ext/tudelft_gazebo_models
. You will have to run git submodule init, git submodule update to pull in the models.
Airframe
Enhance your Paparzazzi airframe file to be able to use Gazebo (see examples/ardrone2_gazebo.xml
):
Select Gazebo as the FDM (Flight Dynamics Model) by adding it to the aircraft file
<target name="nps" board="pc">
<module name="fdm" type="gazebo"/>
</target>
Add actuator thrusts and torques to the SIMULATOR
section:
<section name="SIMULATOR" prefix="NPS_">
<define name="ACTUATOR_NAMES" value="nw_motor, ne_motor, se_motor, sw_motor" type="string[]"/>
<define name="ACTUATOR_THRUSTS" value="1.55, 1.55, 1.55, 1.55" type="double[]"/>
<define name="ACTUATOR_TORQUES" value="0.155, -0.155, 0.155, -0.155" type="double[]"/>
...
<section>
The thrusts and torques are expressed in SI units (N, Nm) and should be in the same order as the ACTUATOR_NAMES
.
In the same section, bypass the AHRS and INS as these are not supported yet, so add this
<section name="SIMULATOR" prefix="NPS_">
...
<define name="BYPASS_AHRS" value="1"/>
<define name="BYPASS_INS" value="1"/>
...
<section>
If you want to use visual based behavior, enable video thread simulation:
<section name="SIMULATOR" prefix="NPS_">
...
<define name="SIMULATE_VIDEO" value="1"/>
...
<section>
Specify the Gazebo world and aircraft name:
<section name="SIMULATOR" prefix="NPS_">
...
<define name="GAZEBO_WORLD" value="my_world.world"/>
<define name="GAZEBO_AC_NAME" value="my_uav"/>
<section>
Note
Make sure all included modules work with NS.
At the current state of Paparazzi code (20180206), most of the modules that depend on video_thread are only built when the target ap (autopilot hardware) is selected as the target.
As a quick ‘n dirty fix, try to remove the target attribute from the makefile element in the module xml, e.g.:
<makefile target="ap"> ---> <makefile>
It would be great if as a user you would improve this and make a Pull request of your code improvements to the main Paparazzi codebase, TIA