ROS Tutorial Summarize

Tutorial 1 (Configurations)

• Create a ROS workspace:

mkdir -p ~/catkin_ws/src
cd ~/catkin_ws
catkin_make

• Overlay the workspace over environment:

source devel/setup.bash

• Check out:

echo $ROS_PACKAGE_PATH

Tutorial 2 (Packages)

• Find the path of a package:

rospack find roscpp

• Go into the path of a package:

roscd roscpp

The command will only find ROS packages that are within the directories listed in your ROS_PACKAGE_PATH.

• Go into the log directory:

roscd log

• List directory content:

rosls roscpp_tutorials

Tutorial 3 (Packages)

• Create a ROS package:

cd ~/catkin_ws/src
catkin_create_pkg beginner_tutorials std_msgs rospy roscpp

beginner_tutorials is the created packages while those after it are dependencies.

• Build the workspace:

cd ~/catkin_ws
catkin_make

• Source the workspace:

. ~/catkin_ws/devel/setup.bash

• List 1st order packages dependencies:

rospack depends1 beginner_tutorials

These dependencies are stored in the package.xml file:

roscd beginner_tutorials
cat package.xml

• List dependencies recursively:

rospack depends beginner_tutorials

• Customize the package.xml:

Without comments, the file content looks like this:

<?xml version="1.0"?>
<package>
  <name>beginner_tutorials</name>
  <version>0.0.0</version>
  <description>The beginner_tutorials package</description>

  <maintainer email="xiaoqiang@todo.todo">xiaoqiang</maintainer>

  <license>TODO</license>

  <buildtool_depend>catkin</buildtool_depend>

  <build_depend>roscpp</build_depend>
  <build_depend>rospy</build_depend>
  <build_depend>std_msgs</build_depend>
</package>

It contains the description tag, maintainer tag, license tag and dependencies tags, which can be customized as you wish.

The dependencies are split into build_depend, buildtool_depend, exec_depend(run_depend sometimes) and test_depend.

We want our specified dependencies to be available at build and run time, so we’ll add a run_depend tag for each of them as well:

<?xml version="1.0"?>
<package>
  <name>beginner_tutorials</name>
  <version>0.0.0</version>
  <description>The beginner_tutorials package</description>

  <maintainer email="xiaoqiang@todo.todo">xiaoqiang</maintainer>

  <license>TODO</license>

  <buildtool_depend>catkin</buildtool_depend>

  <build_depend>roscpp</build_depend>
  <build_depend>rospy</build_depend>
  <build_depend>std_msgs</build_depend>

  <run_depend>roscpp</run_depend>
  <run_depend>rospy</run_depend>
  <run_depend>std_msgs</run_depend>
</package>

Tutorial 4 (Packages)

• Build packages:

rosmake beginner_tutorials

It builds (compiles) the beginner_tutorials plus all its dependencies in a correct order.

rosmake multiple packages:

rosmake [package1] [package2] [package3]

• catkin_make

Usage:

catkin_make [make_targets] [-DCMAKE_VARIABLES=...]

It combines the calls to cmake and make in the standard CMake workflow.

If no target specified, it will compile all packages in the workspaces together in a correct order:

catkin_make
catkin_make install # (optionally)

The above command will build any catkin project found in the src folder.

To build projects in a different place, you would call catkin_make like this:

catkin_make --source my_src
catkin_make install --source my_src # (optionally)

Now, build your packages:

cd ~/catkin_ws
catkin_make

Tutorial 5 (ROS node)

• Running roscore:

roscore

roscore is the first thing you should run when using ROS.

• Using rosnode:

rosnode list
rosnode info /rosout

ROS node isn’t much more than an executable file within a ROS package.

ROS nodes use a ROS client library to communicate with other nodes.

• Using rosrun:

rosrun [package_name] [node_name]

rosrun runs a node within a package.

rosrun turtlesim turtlesim_node

List all running nodes:

rosnode list

• Reassign the name for a node:

rosrun turtlesim turtlesim_node __name:=my_turtle

List all running nodes:

rosnode list

• Review:

roscore: master + rosout + parameter server
rosnode: ROS tool to get information about a node
rosrun: runs a node from a given package

Tutorial 6 (ROS topic)

• Start roscore and run turtlesim:

roscore
rosrun turtlesim turtlesim_node

• Move the turtle:

rosrun turtlesim turtle_teleop_key

Now move the turtle with arrow keys.

• Show the graph of ROS running nodes:

rosrun rqt_graph rqt_graph

The nodes turtlesim_node and turtle_teleop_key are comunicated by using ROS topic /turtle1/cmd_vel.

One message publisher turtle_teleop_key and one message subscriber turtlesim_node.

• rostopic:

rostopic -h

This lists all the available options and their explanations.

rostopic echo /turtle1/cmd_vel

This prints the publishing messages.

• List all the running topics:

rostopic list -h # help on the available options
rostopic list -v # verbose

• Show message type:

rostopic type /turtle1/cmd_vel

Result is geometry_msgs/Twist.

• Show details of this type of message with rosmsg:

rosmsg show geometry_msgs/Twist

Result is:

geometry_msgs/Vector3 linear
  float64 x
  float64 y
  float64 z
geometry_msgs/Vector3 angular
  float64 x
  float64 y
  float64 z

• Directly publish message using rostopic:

rostopic pub -1 /turtle1/cmd_vel geometry_msgs/Twist -- '[2.0, 0.0, 0.0]' '[0.0, 0.0, 1.8]'

-1 means publish the message once. If you want to publish a steady stream of messages, use -r.

-- tells the option parser that none of the following arguments is an option (important e.g. when the arguments contain negative numbers).

The arguments '[2.0, 0.0, 0.0]' '[0.0, 0.0, 1.8]' are in YAML syntax. See YAML command line documentation for details.

• rostopic hz:

See how fast the turtlesim_node is publishing /turtle1/pose:

rostopic hz /turtle1/pose

We can see the detailed format of the publishing/subscribing message:

rostopic type /turtle1/cmd_vel | rosmsg show

• Using rqt_plot:

To plot the curve between /turtle1/pose/x and /turtle1/pose/y:

rosrun rqt_plot rqt_plot

In the pop up window, type /turtle1/pose/x in the text box after the Topic and press Enter. Then type /turtle1/pose/y and repeat the process.