1. - The Robot Operating System
Ben Lewis
February

2. Intent of Lecture I am not an expert Give an overview of possibilities
Show examples
Learn that ROS can be very useful
Please read the information on the wiki and do the tutorials

3. What is ROS? Non-OS software package for developing robotics.
Version system - names like “Hydro” or “Indigo”
Handles communications, services, and multiple computers with good abstraction
De facto industry standard - very common
Developed at Stanford (by a BYU grad), then by Willow Garage
Supports C++ and Python
Runs on Linux (Windows version experimental)

4. Features Publisher-subscriber architecture
Can network to multiple computers
Can log and play back information (rosbag)
Rich ecosystem of developers
Gazebo simulator
Manages coordinate frames

5. Getting Started Install - via apt-get and apt-add-repository
Detailed instructions are found online
desktop-full version is ideal
sudo rosdep-init
Adding path (setup.bash) to .bashrc
Distributions - ROS Indigo
Installs OpenCV as well
Create a workspace (catkin_ws)

6. Packages
Logical organization of functionality (messages, publishers, subscribers, services) for a common purpose
Located in the src directory of the workspace
Built using catkin_make
Many packages are available online
rospack list

7. Topics and Messages rqt_graph
Topics carry messages between publisher and subscribers
Predefined messages: std_msgs, sensor_msgs, etc. A bundle of data
Choose a message type or roll your own

8. Common Commands roscore rosrun rosmsg rostopic rosls / roscd
catkin_make

9. Running ROS Run roscore & (1x) Start all nodes
Use a launch file for efficiency - XML file that launches everything, configures parameters, etc.
Run rqt_graph for visualization, rostopic echo, rostopic hz, etc.
Call services, publish commands, etc.

10. Simple Program catkin_create_pkg <name> <dependencies>
e.g. rospy, roscpp, opencv (?)
Dependencies can be added later
Publisher (example)
Subscriber (example)
Callbacks when receiving a message

11. Making the package package.xml CMakeLists.txt catkin_make in workspace
Package name, version, owner, dependencies
Meta information
CMakeLists.txt
cmake file, defines included files and dependencies
Add custom messages, services, executables, libraries, etc.
catkin_make in workspace

12. Launch Files Incredibly useful for starting a large number of nodes
Automatically calls roscore
Initialize parameters for nodes
Configurability
XML format

13. Services Bi-directional Can be used to perform dedicated tasks
Client-server architecture
Usually placed in the srv folder

14. Other features Network connection Data playback Custom messages
Remapping nodes to different names
Normally, you can only have one node of the same name running; new instances kill old instances
Log messages (i.e. ROS_INFO)
MATLAB compatibility (... sort of)
Namespaces - for preventing conflicts in nodes.
Each robot should have its own namespace
Multiple roscores?