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Introduction to ROS

Writing your own ROS node

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Intelligent Robotics: ROS

Mark Rowan

University of Birmingham

Semester 1 2011

Mark Rowan Intelligent Robotics: ROS
http://find/http://goback/

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Outline

1 Introduction to ROS

2 Writing your own ROS node

3 Working together

4 Final words


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What is ROS?

Interface between low-level robot and high-level programming

languages.

Languages: C++, Python, Java.

Robots: all sorts!

Open-source community-driven platform, supported by Willow

Garage and Google.

Fast becoming the industry standard in robotics software.


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What is ROS?

Interface between low-level robot and high-level programming

languages.

Languages: C++, Python, Java.

Robots: all sorts!

Open-source community-driven platform, supported by Willow

Garage and Google.

Fast becoming the industry standard in robotics software.


I t d ti t ROS

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What kind of programs do we write?

Laser scans

Movement commands


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ROS nodes

Program components in ROS are modular, called Nodes.

e.g. One node to control a laser,

one node to control the wheels,

one node to process laser data and decide what movements to

make.


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Communication between nodes

Nodes send data by talking and listening (or publishing and

subscribing).Messages containing data are published on topics.

Any node can subscribe to messages on any topic.

Nodes need a method by which to find each other: roscore


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Publisher topic Subscriber

talker chatter (std_msgs/String) listener

roscore

rostopic pub /chatter std_msgs/String Hello World -r 10

rostopic echo /chatter

Keeps going even when we kill echo. . .Mark Rowan Intelligent Robotics: ROS

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Publisher topic Subscriber

talker chatter (std_msgs/String) listener

roscore

rostopic pub /chatter std_msgs/String Hello World -r 10

rostopic echo /chatter

Keeps going even when we kill echo. . .Mark Rowan Intelligent Robotics: ROS

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Lots of nodes


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Useful tools

rostopic list list all currently published topics.rostopic echo listen to messages on a topic.

Ctrl+C kill current program in terminal.


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Module webpage

All this information is on the module webpage in the Notes section:http://www.cs.bham.ac.uk/internal/courses/

int-robot/2011/


Introduction to ROS
http://www.cs.bham.ac.uk/internal/courses/int-robot/2011/http://www.cs.bham.ac.uk/internal/courses/int-robot/2011/http://www.cs.bham.ac.uk/internal/courses/int-robot/2011/http://www.cs.bham.ac.uk/internal/courses/int-robot/2011/http://find/http://goback/

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Writing a ROS Java node

import org . ros .node.

;import org . ros . node. to pi c . Publ ishe r ;

import org . ros . message . geometry_msgs . Twi st ;

import org . ro s . message . sensor_msgs . LaserScan ;

import org . ros . message . MessageLi stener ;

p u b l i c c l as s Mover implements NodeMain {

p r i v a t e Node node ;

p r i v a t e P u b l i s h e r < T w i s t > pub ;

p u b l i c v oi d main( NodeConfigurat ion nc) throws E x ce p t io n {

node = new DefaultNodeFactory ( ) . newNode( "robot_mover" , nc ) ;

pub = node. newPublis her ( " cmd_vel" , " geometry_msgs / Twi st " );

node. newSubscriber ( " base_scan" , " sensor_msgs / LaserScan" , new MessageListener( ) {

p u b l i c v oi d onNewMessage( LaserScan message ) {

move( message ) ; / / C a l l method t o c ho os e movement d i r e c t i o n

}} ) ;

}

p u b l i c v oi d shutdown ( ) {

node. shutdown ( ) ;

}

}


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W iti ROS d

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Introduction to ROSWriting your own ROS node

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Compiling and running

First time: rosmake robotics

All other times: roscd robotics && ant compile

Run: rosrun rosjava_bootstrap run.py robotics ex1.Node



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Teams of 3, each team given a laptop with ROS installed.

Share code using SVN.

Register a repository at

https://codex.cs.bham.ac.uk/svnadmin/

Commit after every new feature or bug fix.

Useful commit messages.

Update before you commit!


https://codex.cs.bham.ac.uk/svnadmin/https://codex.cs.bham.ac.uk/svnadmin/http://find/http://goback/

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W ki t th

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Experiment!

Record your findings.

Collaborate but give credit.

Good luck!



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Experiment!



Good luck!



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Experiment!



Good luck!



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Experiment!



Good luck!


Documents

Ros Intro