Computer Vision Group Prof. Daniel Cremers

VisNav Exercise 01

Dr. Jürgen Sturm

Jakob Engel Christian Kerl

Introduction to ROS

What is ROS?

Robot Operating System

Open-Source Middleware for Robotics

Drivers, Communication, Package System, …

Supports C++, Python, …

Dr. Jürgen Sturm, Computer Vision Group, TUM Visual Navigation for Flying Robots 2

ROS in Numbers

175+ organizational/individual contributors

90+ types of robots supported

3699+ packages

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Concepts – Nodes

Every ROS-enabled program is a node

Registers with ROS master

Unique name

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Concepts – Master

Registry for

Nodes

Topics

Services

Parameters

One instance per system

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Concepts – Topics

Message channel between nodes

Unique name

/ardrone/front/image_raw

Fixed type

sensor_msgs/Image

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namespace name

Concepts – Topics

Node sending messages is a publisher

Node receiving messages is a subscriber

Topic has to be advertised beforehand

Multiple publishers/subscribers per topic possible

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Concepts – Bags

Containers to store messages

Supports recording and playback of messages

Good for testing, debugging, logging

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Tools – roscore

Starts the ROS master

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Tools – rosrun/roslaunch

Starts a node

rosrun ardrone_autonomy ardrone_driver

Important environment variable $ROS_PACKAGE_PATH

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package node

Tools – rostopic

rostopic

list – display available topics

info – show details of a topic

hz – measure publishing rate

echo – print messages

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Tools – rosbag+rxbag

rosbag

record – create new bag file

play – playback a bag

info – display details about a bag

rxbag – GUI to view bag files

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Tools – rviz

Visualization tool

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