Gazebo

Gazebo

The nice sim framework Gazebo from here http://gazebosim.org/ can now be use from withing Paparazzi. Are you doing work on UAS in combination with e.g. Vision based navigation check it out. I might make testing your new work so much simpler.

Be warned, using it can be highly addictive, and might tempt youinto buying a new computer with hight spacification. To be able to use Gaxzebo a very good Video card is needed, considder upgrading you yadware if everything runs to slow.

Not that at the moment it is tested with v8 and the new v9 not yet, but feel free to try, the fun of opensource is in to make it work like you want it, If you have it working for v9, a pull request of changes neede warmly welcomed by the Paparazzi developers community.

Make yourself immortal; Add Gazebo v9 support

Gazebo backend for NPS NPS simulator

{TODO: Animated GIF here}}

Why

What is the use of this all.

Well... to be able to test your routines before you get cold, or to warm flying your aircraft for real outside and save some traveling time in the same run. Ofcoure there should be a much better text here.. It's wik so Please add it and remove what you see fit.

Installation

We assume you already have Paparazzi installed via the One liner. If Not install Paparzzi first plz. Then come back to this page.

Gazebo Installation=

Steps to install Gazebo

     1. Make sure gazebo 9 is installed. (sudo apt-get install gazebo8 libgazebo8-dev)

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.

World

Prepare the world (see conf/simulator/gazebo/worlds/ardrone.world).

NOTE: Pay attention to the following:

The real-time update rate should be set to zero, as the simulation backend 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>

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 behaviour, 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>

   4. 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 improvments to the main Paparazzi codebase, TIA

Reality

Never forget... A sim is not reality... validate via testflights in the real world after you think everything you created works perfectly.