MRC/Tutorials/Setting up the PICO simulator: Difference between revisions

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== Gazebo ==
= Installing Gazebo =


We will use the robot simulator [[http://gazebosim.org/ Gazebo]] to simulate the PICO robot and its environment. This includes simulation of the physics and sensors of the robot. To install Gazebo:
We will use the robot simulator [[http://gazebosim.org/ Gazebo]] to simulate the PICO robot and its environment. This includes simulation of the physics and sensors of the robot. To install Gazebo:
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<pre>gazebo</pre>
<pre>gazebo</pre>
= Configuring the PICO simulator =
Now you have installed Gazebo, we can almost start using the PICO simulator. However, we first need to ''compile'' the ROS packages that we checked-out in the ''~/ros/emc'' folder before:
# Open a terminal ''(ctrl-alt-t)''
# Build and compile the jazz simulator and other necessary packages: <pre>rosmake pico_gazebo gazebo_map_spawner</pre>
Furthermore, Gazebo needs to know where to find the PICO robot description (located in ''pico_description'') which includes its meshes, textures, kinematic chain, etc, and where to find the plugins for the controllers and sensors. This information can be set in the environment variables ''GAZEBO_PLUGIN_PATH'' and ''GAZEBO_MODEL_PATH'':
# Open a terminal ''(ctrl-alt-t)''
# Open ''.bashrc'':<pre>gedit ~/.bashrc</pre>
# Add the following lines:<pre>export GAZEBO_PLUGIN_PATH=~/ros/emc/general/pico_gazebo/lib:~/ros/emc/general/tue_gazebo_plugins/lib:$GAZEBO_PLUGIN_PATH</pre><pre>export GAZEBO_MODEL_PATH=~/ros/emc/general/jazz_description:$GAZEBO_MODEL_PATH</pre>
== Starting the Simulator ==
# Start Gazebo:<pre>gazebo</pre>
# Spawn the maze:<pre>rosrun gazebo_map_spawner spawn_maze</pre>
# Spawn PICO:<pre>roslaunch pico_gazebo pico.launch</pre>
Notice that the PICO robot is spawned in the Gazebo world. The Gazebo GUI shows how the world actually '''is'''. We can also visualize how the robot perceives it through its sensors, by using the ROS tool [http://ros.org/wiki/rviz Rviz]. You can start RViz with a pre-defined config showing most of PICO' sensors using:
<pre>rosrun pico_visualization rviz</pre>
In fact, this simply runs the following command:
<pre>rosrun rviz rviz -d ~/ros/general/jazz_visualization/rviz/jazz.vcg</pre>
If you are running the Gazebo simulation, you will see the PICO robot model and white dots which represent the sensor data originating from the (simulated) laser range finder. RViz allows you to visualize many more things. For example, to show the data from the camera:
# Click on the ''Add'' button in the lower left
# Select ''Camera'' and click ''OK''. A Camera item will pop up in the ''Displays'' view on the left.
# Click in the field right next to ''Image Topic'' and click the ''...'' button. Now you can select the camera topic (''/pico/camera/image'')
You will see the camera images visualized in the lower left of your screen.
== Examples ==
Here are some examples on how to use the simulator and how to practice the corridor competition in simulation.
=== Jazz Driving Example ===
# Have a look at the file '''jazz_node.cpp''' in the ''src'' folder of the '''jazz_example''' package. You should be able to understand what the program will do.
# Build the package:<pre>rosmake jazz_example</pre>
# Run the node (make sure the simulator is still running):<pre>rosrun jazz_example jazz_node</pre>Check the result in both Gazebo and RViz.
# Feel free to use this example as a start for your project
=== Jazz Safe Driving Example ===
# First of all, make sure you have the latest version of the '''jazz_example''' package:
## <pre>roscd jazz_example</pre>
## <pre>svn up</pre>
# Take some time to have a good look at the file '''safe_drive.cpp''' in the '''src''' folder of the '''jazz_example''' package. It contains a quite elaborate explanation of what is going on in the code, which will hopefully clarify quite some things.
# Build the package:<pre>rosmake jazz_example</pre>
# Run the node (make sure the simulator is still running):<pre>rosrun jazz_example safe_drive</pre>Check the result in both Gazebo and RViz.
# Feel free to use this example as a start for your project
<!--
=== Corridor ===
An extra Gazebo world has been added, which contains a simple corridor with a side exit.
# First, make sure you SVN-update the jazz_simulator package, i.e.:<pre>roscd jazz_simulator</pre><pre>svn up</pre>
# Then, you can start the simulator with the new world by typing:<pre>roslaunch jazz_simulator start_corridor.launch</pre>
=== Changing the initial robot pose ===
As you can see, Jazz does not start exactly in the center of the corridor, and its rotation is also slightly off. This is done to make sure that you don't rely on a ''perfect'' initial position, ''i.e.'', you have to be robust against such deviations. It might be nice to play around with different initial poses. To do so, have a look at the launch file ''start_corridor.launch'' in the ''launch'' subfolder. You should see a line like this:
<pre><node name="spawn_jazz" pkg="gazebo" type="spawn_model" args="-unpause -urdf -param robot_description -model jazz -x 5.3 -y 0 -Y 1.87" respawn="false" output="screen" /></pre>
This line starts the ''spawn_model'' node from the ''gazebo'' ROS package, with some arguments as defined in ''args''. In this argument list you see ''-x'', ''-y'' and ''-Y'', which define the initial X-position, Y-position and rotation (in radians) respectively. Play around with these values to see if your algorithm is robust against different initial poses.
=== Changing the corridor ===
It may also be nice to change the corridor, ''e.g.'', changing the position of the exit. To do so, simply edit the file '''tue_corridor.png''' in the ''./Media/materials/textures'' folder of the ''jazz_simulator'' package. As you can see, this is a simple image in which white pixels represent free space, and black pixels represent walls. Of course, you need to restart the simulator to see the effects of your change.
-->
== Troubleshoot ==
=== Gazebo does not stop gracefully upon exit or interrupt (ctrl-c) ===
You may get the warning:<pre>Warning [gazebo_main.cc:59] escalating to SIGKILL on server</pre> when stopping Gazebo. This is a known bug and has no consequences, other than that it takes a bit longer to kill Gazebo.

Revision as of 21:52, 23 April 2014

Installing Gazebo

We will use the robot simulator [Gazebo] to simulate the PICO robot and its environment. This includes simulation of the physics and sensors of the robot. To install Gazebo:

  1. Open a terminal (ctrl-alt-t)
  2. Setup your computer to accept software from packages.osrfoundation.org:
    sudo sh -c 'echo "deb http://packages.osrfoundation.org/gazebo/ubuntu precise main" > /etc/apt/sources.list.d/gazebo-latest.list'
  3. Retrieve and install the keys for the Gazebo repositories:
    wget http://packages.osrfoundation.org/gazebo.key -O - | sudo apt-key add -
  4. Update apt-get and install Gazebo.
    sudo apt-get update
    sudo apt-get install gazebo
  5. Initialize.
    gzserver
    Wait until you get a message like Publicized address: ....

You can try if your Gazebo installation was successfull by either executing a gazebo client on a seperate terminal (i.e., while gzserver is running): 

gzclient

Or by running the server and client at the same time with one command: 

gazebo

Configuring the PICO simulator

Now you have installed Gazebo, we can almost start using the PICO simulator. However, we first need to compile the ROS packages that we checked-out in the ~/ros/emc folder before:

  1. Open a terminal (ctrl-alt-t)
  2. Build and compile the jazz simulator and other necessary packages: 
    rosmake pico_gazebo gazebo_map_spawner

Furthermore, Gazebo needs to know where to find the PICO robot description (located in pico_description) which includes its meshes, textures, kinematic chain, etc, and where to find the plugins for the controllers and sensors. This information can be set in the environment variables GAZEBO_PLUGIN_PATH and GAZEBO_MODEL_PATH:

  1. Open a terminal (ctrl-alt-t)
  2. Open .bashrc:
    gedit ~/.bashrc
  3. Add the following lines:
    export GAZEBO_PLUGIN_PATH=~/ros/emc/general/pico_gazebo/lib:~/ros/emc/general/tue_gazebo_plugins/lib:$GAZEBO_PLUGIN_PATH
    export GAZEBO_MODEL_PATH=~/ros/emc/general/jazz_description:$GAZEBO_MODEL_PATH

Starting the Simulator

  1. Start Gazebo:
    gazebo
  2. Spawn the maze:
    rosrun gazebo_map_spawner spawn_maze
  3. Spawn PICO:
    roslaunch pico_gazebo pico.launch

Notice that the PICO robot is spawned in the Gazebo world. The Gazebo GUI shows how the world actually is. We can also visualize how the robot perceives it through its sensors, by using the ROS tool Rviz. You can start RViz with a pre-defined config showing most of PICO' sensors using: 

rosrun pico_visualization rviz

In fact, this simply runs the following command: 

rosrun rviz rviz -d ~/ros/general/jazz_visualization/rviz/jazz.vcg

If you are running the Gazebo simulation, you will see the PICO robot model and white dots which represent the sensor data originating from the (simulated) laser range finder. RViz allows you to visualize many more things. For example, to show the data from the camera:

  1. Click on the Add button in the lower left
  2. Select Camera and click OK. A Camera item will pop up in the Displays view on the left.
  3. Click in the field right next to Image Topic and click the ... button. Now you can select the camera topic (/pico/camera/image)

You will see the camera images visualized in the lower left of your screen.

Examples

Here are some examples on how to use the simulator and how to practice the corridor competition in simulation.

Jazz Driving Example

  1. Have a look at the file jazz_node.cpp in the src folder of the jazz_example package. You should be able to understand what the program will do.
  2. Build the package:
    rosmake jazz_example
  3. Run the node (make sure the simulator is still running):
    rosrun jazz_example jazz_node
    Check the result in both Gazebo and RViz.
  4. Feel free to use this example as a start for your project

Jazz Safe Driving Example

  1. First of all, make sure you have the latest version of the jazz_example package: 
    1. roscd jazz_example
    2. svn up
  2. Take some time to have a good look at the file safe_drive.cpp in the src folder of the jazz_example package. It contains a quite elaborate explanation of what is going on in the code, which will hopefully clarify quite some things.
  3. Build the package:
    rosmake jazz_example
  4. Run the node (make sure the simulator is still running):
    rosrun jazz_example safe_drive
    Check the result in both Gazebo and RViz.
  5. Feel free to use this example as a start for your project


Troubleshoot

Gazebo does not stop gracefully upon exit or interrupt (ctrl-c)

You may get the warning:

Warning [gazebo_main.cc:59] escalating to SIGKILL on server

when stopping Gazebo. This is a known bug and has no consequences, other than that it takes a bit longer to kill Gazebo.

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