04 ROS Tutorial - Università degli Studi di Bergamo

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Transcript 04 ROS Tutorial - Università degli Studi di Bergamo

ROS Robot Operating System

Robotica Prof. Davide Brugali Università degli Studi di Bergamo

Tutorials

 [online] http://wiki.ros.org/  [2014] Jason M. O’Kane

A Gentle Introduction to ROS

https://cse.sc.edu/~jokane/agitr/agitr-letter.pdf

 [2013] Aaron Martinez, Enrique Fernández

Learning ROS for Robotics Programming

http://www.ict.griffith.edu.au/~vlad/teaching/robotics.d/R EADINGS/Learning20ROS%20for%20Robotics%20Pro gramming%20%5BeBook%5D.pdf

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Speed control

y Odometry Y

y V

Twist

{

x Odometry X

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4 Sviluppo di un sistema composto da tre applicazioni (nodi) Legge la tastiera e modifica il twist corrente

velocity_keyboard VelocityCmd

Implementato da noi Trasmette periodicamente il twist corrente al robot

velocity_controller Twist

Simula il movimento del robot

rover_driver

Implementato da noi Simulatore Turtlesim fornito con ROS UNIBG - Robotica - Brugali

Software components

rover_driver main()

twist

velocity_controller main()

command

velocity_keyboard main()

RoverDriver + setTwist() + getOdometry() VelocityController + updateTwist() + getTwist()

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VelocityKeyboard + readKeyboard()

Connectors implementation : Middleware

rover_driver velocity_controller velocity_keyboard Runtime Infrastructure (Concurrency, Communication) Operating System Runtime Infrastructure (Concurrency, Communication) Operating System UNIBG - Robotica - Brugali

Connectors : Publish-subscribe styles (Event flow)

 Components interact via announced events  Components subscribe to a set of events  The runtime infrastructure ensures that each published event is delivered to all subscribers  The connector is an event bus  Set of subscribers are unknown to the publisher UNIBG - Robotica - Brugali

Robot Operating system (ROS)

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Example of ROS Node: velocity_controller

Nome Tipo

velocity_controller main() subscribes to keyboard/ cmd_vel VelocityCmd

main loop VelocityController + updateTwist() + getTwist() publishes turtle1/ cmd_vel Twist

Nome Tipo UNIBG - Robotica - Brugali

velocity_controller_node.cpp

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velocity_controller_node.cpp

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VelocityController.hpp

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VelocityController.cpp

13 … etc.

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Workspace di sviluppo per ROS

mobile_robot / src / CMakeLists.txt

build / devel / -- WORKSPACE - SOURCE SPACE (contains the packages) -- The 'toplevel' CMake file - - BUILD SPACE CATKIN_IGNORE DEVELOPMENT SPACE 14 Workspace CMakeList.txt

/ ROS-Tutorial /mobile_robot/

http://wiki.ros.org/catkin/Tutorials/create_a_workspace UNIBG - Robotica - Brugali

Creazione del Workspace e compilazione

$ mkdir ~ / ROS-Tutorial / mobile_robot / src $ cd ~ / ROS-Tutorial / mobile_robot / src $ catkin_init_workspace $ cd ~ / ROS-Tutorial / mobile_robot $ catkin_make $ source devel / setup.bash

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ROS Packages

 Software in ROS is organized in useful module.

packages

. A package might contain ROS nodes, a ROS-independent library, a dataset, configuration files, a third-party piece of software, or anything else that logically constitutes a  The goal of these packages it to provide this useful functionality in an easy-to-consume manner so that software can be easily reused.  This means that a package is the smallest individual thing you can build in ROS and it is the way software is bundled for release (meaning, for example, there is one debian package for each ROS package), respectively. 16  http://wiki.ros.org/Packages UNIBG - Robotica - Brugali

Workspace di sviluppo per ROS

packages 17 Node Class Message Workspace velocity_keyboard velocity_keyboard_node.hpp

velocity_keyboard_node.cpp

VelocityKeyboard.hpp VelocityKeyboard.cpp

VelocityCmd.msg

CMakeList.txt

package.xml

velocity_controller velocity_controller_node.hpp

velocity_controller_node.cpp

VelocityController.hpp VelocityController.cpp

CMakeList.txt

package.xml

CMakeList.txt

/ ROS-Tutorial /mobile_robot/

http://wiki.ros.org/catkin/Tutorials/create_a_workspace UNIBG - Robotica - Brugali turtlesim

Package velocity_controller

$ cd ~/ROS-Tutorial/mobile_robot/src $ catkin_create_pkg velocity_controller std_msgs rospy roscpp $ source ~/ROS-Tutorial/mobile_robot/devel/setup.bash

mobile_robot / src / CMakeLists.txt

velocity_controller/ CMakeLists.txt

package.xml

-- package UNIBG - Robotica - Brugali

ROS Nodes

 A

node

is a process that performs computation. Nodes are combined together into a graph and communicate with one another using  streaming topics ,  RPC services ,  and the Parameter Server .  These nodes are meant to operate at a fine-grained scale; a robot control system will usually comprise many nodes.  For example, one node controls a laser range-finder, one Node controls the robot's wheel motors, one node performs localization, one node performs path planning, one node provide a graphical view of the system, and so on.

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ROS Nodes

20  All running nodes have a

graph resource name

that uniquely identifies them to the rest of the system.  For example, /hokuyo_node could be the name of a Hokuyo driver broadcasting laser scans.  Nodes also have a node type, that simplifies the process of referring to a node executable on the fileystem.  These node types are

package resource name

with the name of the node's package and the name of the node executable file.  In order to resolve a node type, ROS searches for all executables in the package with the specified name and chooses the first that it finds.  As such, you need to be careful and not produce different executables with the same name in the same package .

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Nodo velocity_controller

velocity_controller_node

main program 21

VelocityController

N.B. comando per spostarsi direttamente nella cartella base di un package $ roscd velocity_controller/ $ gedit include/VelocityController.hpp

$ gedit src/VelocityController.cpp

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VelocityKeyboard.hpp

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velocity_keyboard_node.hpp

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velocity_keyboard_node.cpp

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Messaggio “VelocityCmd”

26  velocity_controller  include  VelocityController.hpp

 velocity_controller_node.hpp

 msg 

VelocityCmd.msg

 src  VelocityController.cpp

 velocity_controller_node.cpp

 CMakeList.txt

 package.xml

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Messaggio “VelocityCmd”

VelocityCmd.msg

int8

command 27 UNIBG - Robotica - Brugali

CMakeLists.txt

## Declare a cpp executable add_executable( velocity_controller_node src/VelocityController.cpp

src/velocity_controller_node.cpp)

nome del file eseguibile

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Compilare il codice sorgente in ROS

 Aprire un terminale selezionando l’icona  Digitare i seguenti comandi: $ cd ~/ROS-Tutorial/mobile_robot/src $ source ~/ROS-Tutorial/mobile_robot/devel/setup.bash

$ catkin_make 29  Se serve, modificare il codice sorgente  Ricompilare i progetti con il comando catkin_make UNIBG - Robotica - Brugali

ROS Messages

velocity_controller Twist turtlesim



geometry_msgs / Twist.msg



nav_msgs / Odometry.msg

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POSE

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TWIST

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Odometry

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Esecuzione di programmi ROS

 Cambiare workspace di Ubuntu selezionando l’icona   Selezionare una delle trefinestre libere Aprire quattro terminali cliccando il tasto destro sull’icona 34 UNIBG - Robotica - Brugali

Digitare i seguenti comandi

TERMINALE 1 : avviare il core di ROS $ roscore 35 TERMINALE 2 : avviare il simulatore del robot Turtle $ source ~/ROS-Tutorial/mobile_robot/devel/setup.bash

$ rosrun turtlesim turtlesim_node UNIBG - Robotica - Brugali

Digitare i seguenti comandi

TERMINALE 3 : avviare l’applicazione velocity_controller $ source ~/ROS-Tutorial/mobile_robot/devel/setup.bash

$ roscd velocity_controller $ rosrun velocity_controller velocity_controller_node 36 TERMINALE 4 : avviare l’applicazione velocity_keyboard $ source ~/ROS-Tutorial/mobile_robot/devel/setup.bash

$ roscd velocity_keyboard $ rosrun velocity_keyboard velocity_keyboard_node UNIBG - Robotica - Brugali

Simulatore TurtleSim

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38 Sviluppo di un sistema composto da tre nodi

Keyboard Target position_controller Twist turtlesim Odometry

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