ROS summary

ROS in AIRWiki

The page you are reading provides additional information about installation and package management in ROS.

Basic information about ROS and its elements is available in the ROS HOWTO page. Such page also includes links to other AIRWiki pages related to ROS.

ROS and IDE initial setup

Configure your environment

If you followed the ROS tutorial to configure your environment, the variable $ROS_PACKAGE_PATH should be set. This can be easily verified by check if the command echo $ROS_PACKAGE_PATH returns an output similar to:

/home/your_user_name/fuerte_workspace/sandbox:/opt/ros/<ROS DISTRIBUTION>/share:/opt/ros/<ROS DISTIBUTION>/stacks

If you use a different path (e.g.: ~/eclipse_workspace) you should add it to the $ROS_PACKAGE_PATH variable. The simplest way to achieve this is to edit the .bashrc file located in your home directory and add the line

export ROS_PACKAGE_PATH=~/eclipse_workspace:${ROS_PACKAGE_PATH}

NOTE: Please be sure to add this command AFTER the following line (that you should have added to your .bashrc, according to the tutorial) or you will get an error running make eclipse-project:

source /opt/ros/<ROS DISTIBUTION>/setup.bash

Eclipse

• To reuse your shell environment it is advisable to launch Eclipse with the following command:

bash -i -c /usr/lib/eclipse/eclipse

• To let ROS create the Eclipse project files you can use the following command (only for Fuerte or older releases):

make eclipse-project

Note that if you change anything to your manifest.xml, you will have to run this script again, which will overwrite your Eclipse project file and thereby reverting all manual changes to the project settings. Please refer to this page if you need further information.

• To add an existing project to Eclipse select File --> Import --> General --> Existing Projects into Workspace, select the project's root directory and be sure that the "Copy projects into workspace" option is NOT selected.

• For Groovy users: you have to use the following command from within your catkin_ws folder:

catkin_make --force-cmake -G"Eclipse CDT4 - Unix Makefiles

Then import the project from the build/ folder. A link named Source directory within the project is provided, and you can edit the source code from there.

Package management

ROS packages can be managed using your linux distribution package manager and/or with the built-in ROS package manager.

Internal structure of a package

In ROS, each package has its own directory on disk: all the elements of the package are contained in such directory. The ROS package takes the name of the directory. Some of the package directories are installed by ROS, and reside somewhere on your hard disk (tip: to quickly reach a ROS package from the command line, and discover where it's located, simply use roscd name_of_the_package). Other package directories are created by you, and you can put them wherever you like (usually somewhere in /home/your_username).

It doesn't matter where your packages are, provided that the directory that contains them is one where ROS looks for packages. You can't just put your ROS package directory anywhere you want: you will also need to tell ROS where it can find them. In practice, this is done by properly configuring ROS. The simplest way to create and prepare the directory for a new ROS package is to use roscreate-pkg; otherwise you can do the preparation manually.

The contents of a package directory in ROS are standardized. Most of these are only modified by ROS, and you can ignore them; however, there are some elements of your package's directory that you will have to modify manually. Let us suppose that you are creating a new ROS package called MyPkg. As said above, all the elements of your package will be contained in a directory called MyPkg, located somewhere in your PC's filesystem. The elements of MyPkg that you might need to modify while working on your new package are the following:

• MyPkg/CMakeLists.txt, a text file which tells ROS which elements (executable files, message types, ROS services, ...) it will have to create while building package MyPkg. CMakeLists.txt defines the compile behaviour of rosmake for package MyPkg.

• MyPkg/src/, where the source code for your ROS nodes reside (in the form of .cpp files, if you are using C++). (By the way: the executable files that rosmake creates are in MyPkg/bin.)

• MyPkg/launch/, where you put your launchfiles, if you use them (which is very likely when you build complex ROS systems).

• MyPkg/msg/, where you define your own types of ROS messages.

• MyPkg/srv/, where you define your own ROS services.

• MyPkg/manifest.xml, which (by being present) specifies that MyPkg is a ROS package directory, and which defines some properties of the package; usually you won't need to modify manifest.xml unless you need to add a dependency to your package.

ROS package environment

• To initialize the ROS package management environment:

(as root) rosdep init

• To update the package list:

rosdep update

ROS package installation

• To find a package:

browse to this page to browse a list of available packages.

• To check if a ROS package or stack is installed, use the following commands:

rospack find package_name

rosstack find [stack_name]

If you get an error, install the stack that contains the package with the package manager of your linux distribution (e.g.: sudo apt-get install ros-distribution_release_name-stack_name ), then check again if rospack can find the package. If not, install it with the command:

(as root) rosdep install package_name

New package creation

This command creates a new package in the current directory:

roscreate-pkg package_name package_dependency_1 package_dependency_2 package_dependency_3 ...

Please note that package dependencies can be explicitly specified when the package is created, but they can also be manually added afterwards to the manifest.xml file or with the rospack command. Take a look at this page if you need further information.

CMakeLists.txt

Official pages:
Full description of the syntax
Examples.

cmake_minimum_required(VERSION 2.4.6)
include($ENV{ROS_ROOT}/core/rosbuild/rosbuild.cmake)

# Set the build type.  Options are:
#  Coverage       : w/ debug symbols, w/o optimization, w/ code-coverage
#  Debug          : w/ debug symbols, w/o optimization
#  Release        : w/o debug symbols, w/ optimization
#  RelWithDebInfo : w/ debug symbols, w/ optimization
#  MinSizeRel     : w/o debug symbols, w/ optimization, stripped binaries
# Usage:
#     set(ROS_BUILD_TYPE build_type)
set(ROS_BUILD_TYPE Debug)

rosbuild_init()

# Set the default path for built executables to the "bin" directory
set(EXECUTABLE_OUTPUT_PATH ${PROJECT_SOURCE_DIR}/bin)
# Set the default path for built libraries to the "lib" directory
set(LIBRARY_OUTPUT_PATH ${PROJECT_SOURCE_DIR}/lib)

# Uncomment if you have defined messages
#rosbuild_genmsg()

# Uncomment if you have defined services
#rosbuild_gensrv()

# **** Common commands for building c++ executables and libraries ****

# To add an executable cpp file: 
# Usage:
#     rosbuild_add_executable(${PROJECT_NAME} executable_path)
rosbuild_add_executable(test_read_map src/test_read_map.cpp)

# To add a library:
# Usage:
#     rosbuild_add_library(${PROJECT_NAME} libraries_path)
rosbuild_add_library(map
                    src/map/map_cspace.cpp
                    src/map/map_draw.c)

# To link a library to an executable file:
# Usage:
#     target_link_libraries(${PROJECT_NAME} library_name)
target_link_libraries(test_read_map map)

# To add boost directories:
# rosbuild_add_boost_directories()

# To link boost:
# rosbuild_link_boost(${PROJECT_NAME} thread)

# To add the dynamic reconfigure api:
# rosbuild_find_ros_package(dynamic_reconfigure)
# include(${dynamic_reconfigure_PACKAGE_PATH}/cmake/cfgbuild.cmake)
# gencfg()
# rosbuild_add_executable(dynamic_reconfigure_node src/dynamic_reconfigure_node.cpp)
# rosbuild_add_executable(FIRST_dynamic_reconfigure_node src/FIRST_dynamic_reconfigure_node.cpp)

Makefile

Be sure that the following line is present in the Makefile in order for the command make eclipse-project to work:

include $(shell rospack find mk)/cmake.mk

Manifest.xml

<package>
  <description brief="brief description of your package">

     [write here your package name]

  </description>
  <author>Your name</author>
  <license>BSD</license>
  <review status="unreviewed" notes=""/>
  <url>http://ros.org/wiki/package_name</url>
  <depend package="package dependance 1"/>
  <depend package="package dependance 2"/>
  ....
</package>

Gazebo wrapped into Groovy (a.k.a. Questo matrimonio non s'ha da fare)

Don't waste your time trying to execute the tutorials available on the ROS website!!

They are outdated and will almost surely not work in every ROS distribution later than electric. (Source). You can (almost) safely follow Gazebo's tutorials the gazebo standalone's tutorials, but be sure to select the right tutorials for the version of Gazebo included in your distribution of ROS (as of 15 March 2013, Groovy --> Gazebo 1.3) and to read the following instructions.

How to correctly setup a Gazebo package with a plugin inside Groovy

Note: the following supposes a working and correctly configured ROS environment (follow the ROS official installation guide otherwise)

Hereby we will use the Control model tutorial of gazebo standalone as an example to show what to do to make Gazebo standalone's tutorials work with the ROS-wrapped gazebo.

1. Create the ROS package, specifying the dependency on gazebo, and browse its folder:
   roscreate-pkg gazebo_control_model gazebo; cd gazebo_control_model/
2. Create the .world file, the model file (.sdf) and the plugin file (.cc), if any, as specified in the tutorial
3. Edit the CMakeLists.txt file, adding the following at the end (substitute the .cc filename appropriately):
   rosbuild_add_library(${PROJECT_NAME} control_model.cc)
4. Create the build folder and open it
   mkdir build; cd build
5. Run cmake and make
   cmake .. ; make (note the double point after cmake!)
6. Modify the <plugin filename> tag, if any, in the world files and in the model files. Write the library filename in a full path form. Note also that it is likely that the plugin will be in a "lib/" folder inside your package folder, be sure to write the correct path to the library.
7. Download and extract the following script in the package folder (in the main one, not inside the build folder). Read the included instructions (at the beginning of the script file) and modify the required variables. Then make it executable and run it to create the .launch file:
   chmod ugoa+x zzz_launchers_generator.sh; ./zzz_launchers_generator.sh
   

Interesting links for the future (to be tested)

• This discussion cites some model that seem to be working with the ROS-wrapped-Gazebo.

Common error messages

• Trying to execute the wrapped-into-Groovy Gazebo, you could encounter the following error:

Error [Rendering.cc:37] Failed to load the Rendering engine subsystem unable to find OpenGL rendering system. OGRE is probably installed incorrectly. Double check the OGRE cmake output, and make sure OpenGL is enabled

This can be due to two different issues:

1. The OGRE's package is not correctly installed: in this case install ogre with sudo apt-get install ros-groovy-visualization-common
2. The OGRE_RESOURCE_PATH variable is not correctly set in ROS: to solve this problem you will have to modify the "export OGRE_RESOURCE_PATH" in /opt/ros/groovy/stacks/simulator_gazebo/gazebo/scripts/setup.sh (potentially also in /opt/ros/groovy/stacks/simulator_gazebo/gazebo/setup.bash) with the correct OGRE path. This is usually located in one of the following folders:

/usr/lib/OGRE

/usr/lib/x86_64-linux-gnu/OGRE-1.7.4

/usr/lib/i386-linux-gnu/OGRE-1.7.4

Further information please refer to Gazebo answers

• Trying to spawn a model in gazebo, you could end up stuck with the following message forever:

waiting for service /gazebo/spawn_urdf_model

In this case the namespace could be wrong, try to specify the "gazeborver" namespace at the end of your spawing command, e.g.:

rosrun gazebo spawn_model -file object.urdf -urdf -model my_object -gazebo_namespace gazeborver

rosrun gazebo spawn_model -file object.sdf -gazebo -model my_object -gazebo_namespace gazeborver

NOTE: spawning models in this way will work only if you specify the full urdf/sdf filename path!

• Trying to spawn a model in gazebo, following the tutorial, you could receive an error like this:

Invalid <param> tag: Cannot load command parameter [table_description]: no such command [/opt/ros/groovy/share/xacro/xacro.py /opt/ros/groovy/stacks/simulator_gazebo/gazebo_worlds/objects/table.urdf.xacro].

Solution: as stated at the very beginning of this section, don't follow the tutorials on the ROS website!!

• Launching Gazebo you could get the following error:

run_id on parameter server does not match declared run_id

This is due to Gazebo opening before roscore has completely started. Just ignore it and open it again and it should work!