Embedded Motion Control 2013/Simulator

Installation

If you followed all steps specified on the installation page , you will already have downloaded the simulator Gazebo and our specific Jazz simulator. To be able to use the Jazz simulator, you first have to compile the downloaded ROS packages:

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

   rosmake jazz_gazebo gazebo_map_spawner

Furthermore, Gazebo needs to know where to find the robot description (located in jazz_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/general/jazz_gazebo/lib:~/ros/general/tue_gazebo_plugins/lib:$GAZEBO_PLUGIN_PATH

   export GAZEBO_MODEL_PATH=~/ros/general/jazz_description:$GAZEBO_MODEL_PATH

Usage

1. Start Gazebo:

   gazebo

2. Spawn the maze:

   rosrun gazebo_map_spawner spawn_maze

3. Spawn Jazz:

   roslaunch jazz_gazebo jazz.launch

Notice that the Jazz 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 Jazz' sensors using:

rosrun jazz_visualization rviz

In fact, this simply runs the following command:

rosrun rviz rviz -d ~/svn/emc/2013/general/jazz_visualization/rviz/jazz.vcg

If you are running the Gazebo simulation, you will see the Jazz robot model and white dots which represent the sensor data originating for 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. Load the package in Eclipse, or create your own package, and... have fun!

Corridor

An extra Gazebo world has been added, which contains a simple corridor with a side exit.

1. First, make sure you SVN-update the jazz_simulator package, i.e.:

   roscd jazz_simulator

   svn up

2. Then, you can start the simulator with the new world by typing:

   roslaunch jazz_simulator start_corridor.launch

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:

<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" />

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:

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.