lecture 1: course overview and introduction to...

Lecture 1: course overview andintroduction to ROS

Jonathan [email protected]

PRISMA LabDepartment of Electrical Engineering and Information Technology

University of Naples Federico II

www.prisma.unina.it

Jonathan Cacace 09 March 2020 1

Course overview

Robotics Lab: learn how to program advanced roboticsystems (mobile and industrial).

Formal teacher: Prof. Vincenzo Lippiello

Lecturer: dr. Jonathan Cacace

Postdoctoral researcher @ PRISMA Lab: building 3A, roomS.07http://wpage.unina.it/jonathan.cacace/

jonathan.cacace@{unina.it, gmail.com}Teaching assistantship: Monday 14.30/16.30 (onappointment!)


https://www.docenti.unina.it/vincenzo.lippiello

http://wpage.unina.it/jonathan.cacace/

http://wpage.unina.it/jonathan.cacace/

Course overview

Robotics Lab: first time for us!Objectives:

Improve your skills in programming and usage of Linux OS

Learn to design a whole robotic application interfacingsensors, decision and control

Learn to use off-the-shelf software to speed up thedevelopment process


Course overview

This topics discussed during the course can be classified asfollow:


Course overview

Motivation:


Course overview

Material:

Main: lecture notes. Each lesson is associated with a setof slide, pdf lecture notes and eventually materials (sourcecode, etc. . . ).

Text book: L. Joseph, J. Cacace, ‘Mastering ROS forRobotics Programming 2nd edition’. Get it ‘here’.

Google group: rl2020 (on invitation)


https://www.dropbox.com/s/aj49d39gl1due0l/JCACACE-MASTERING_ROS_FOR_ROBOTICS_PROGRAMMING_SECOND_EDITION.pdf?dl=0

Course overview

Evaluation:

Simulation scenes to program industrial and mobile(ground and aerial) robots

Each candidate chooses a simulation scene to develop aproject

The project can be made in working groups composed by2/3 persons

Project : ROS package to accomplish a given task

Exam: discussion of the project plus questions to provestudent’ knowledge


Course overview

Each lesson is associated with:

A set of slides

Lecture notes

Sample code (if needed)

Step-by-step exercises will help you to become familiar withrobotics programming.


Course overview

Any questions or doubts about the organization of the course?


ROS: an introduction

Robot Operating System (ROS) represents a flexibleframework, providing various tools and libraries to write roboticsoftware. It offers several powerful features to help developersin such tasks as message passing, distributing computing, codereusing, and implementation of state-of-the-art algorithms forrobotic applications.



Originally developed in 2007 at the Willow Garage andStanford Artificial Intelligence Laboratory under GPL license

Since 2013 managed by OSRF

Today used by many robots, universities and companies

Standard for robots programmingJonathan Cacace 09 March 2020 14


Motivation:The most common problem of robotics at the time was thatthey spent too much time to re-implement the softwareinfrastructure required to build complex robotics algorithmslike: drivers to the sensors and actuators, and communicationsbetween different programs inside the same robot and too littletime dedicated to build intelligent robotics programs that werebased on that infrastructure



The correct definition for ROS is a robotic middleware: asoftware that connects different software components orapplications.


Plumbing

ROS allows communication betweenprocesses (nodes). In particular, itprovides publish-subscribe messaginginfrastructure designed to support thequick and easy construction ofdistributed (local and remote)computing systems. For example,consider that your application usesdata from a camera. You can use theROS node deployed by the vendor ofyour camera to implement yourapplication.


Tools

ROS provides an extensive setof tools to configure, manage,debug, visualize data, log andtest your robotic application.


Capabilities

ROS provides a broad collectionof libraries that implementuseful robot functionalities, likemanipulation, control, andperception. In addition, ROScan be connected to otherexternal software like OpenCv,PCL, and so on, thanks toproper wrappers.


Ecosystem

ROS is supported and improvedby a large community, with astrong focus on integration anddocumentation. On ROSwebpage: ros.org you can findbasic and advanced tutorial tolearn how to program in ROS,while di Q&A website(answers.ros.org) allow you todirectly ask you solution foryour own problems (andcontains thousand of questionalready answered).


ROS philosophy

Peer to peer.

Distributed.

Multi-language.

Light-weight.

Free and open-source.


ROS nodes

Nodes are the processes that perform computation (theexecutable). Each ROS node is written using ROS clientlibraries implementing different ROS functionalities, suchas the communication methods between nodes, which isparticularly useful when different nodes of our robot mustexchange information between them. Using the ROScommunication methods, they can communicate with eachother and exchange data. One of the aims of ROS nodes isto build simple processes rather than a large process withall the functionality (modularity).


ROS master

Master: The ROS Master is a particular ROS node thatprovide the name registration and lookup to the rest of thenodes. Nodes will not be able to find each other, exchangemessages, or invoke services without a ROS Master. In adistributed system, we should run the master on onecomputer, and other remote nodes can find each other bycommunicating with this master.


ROS: an application example


ROS communication

Publish-subscribe:


ROS communication

Services:


ROS messages

ROS communication relies on a set of standard and customdata structures called ROS messages. The types of data aredescribed using a simplified message description language calledROS messages. These datatype descriptions can be used togenerate source code for the appropriate message type indifferent target languages. The message definition consists in atypical data structure composed by two main types: fields andconstan


ROS messages

geometry_msgs::PoseStamped is used to share the pose of anobject:

1 std msgs/Header header2 uint32 seq3 time stamp4 s t r i n g f rame id5 geometry msgs/Pose pose6 geometry msgs/Point p o s i t i o n7 f l o a t 6 4 x8 f l o a t 6 4 y9 f l o a t 6 4 z

10 geometry msgs/Quaternion o r i e n t a t i o n11 f l o a t 6 4 x12 f l o a t 6 4 y13 f l o a t 6 4 z14 f l o a t 6 4 w


ROS service

Service: request - response:

1 #Request message type2 s t r i n g s t r3 −−−4 #Response message type5 s t r i n g s t r

The first section is the message type of the request that isseparated by and in the next section is the message type ofthe response. In these examples, both Request and Responseare strings.


ROS visualization

RViz: ROS Visualization


ROS simulation

Gazebo ROS


ROS issue

ROS issue

No QoS in communication

Security: the ROS master will respond to requests fromany device on the network

ROS cannot be used in industry as is.


Developer PC

To programming using ROS you must setup a developer’s PC:

Ubuntu 18.04: https://ubuntu.com/tutorials/tutorial-install-ubuntu-desktop#1-overview

ROS Melodic:http://wiki.ros.org/melodic/Installation/Ubuntu

Dual boot vs Virtual Machine: A simplest way to setup thedeveloper’s PC is installing Linux on a Virtual Machine. This isnot suggested due to the high hardware resources needed by thesimulation scenes used in the evaluation. Moreover, you can useit in the first part of the course to test initial roboticprogramming examples.


https://ubuntu.com/tutorials/tutorial-install-ubuntu-desktop#1-overview

https://ubuntu.com/tutorials/tutorial-install-ubuntu-desktop#1-overview

http://wiki.ros.org/melodic/Installation/Ubuntu

Next lesson

During we will start to discuss the technologies used to programrobots:

C++

C++ compilation using Cmake

Git (version control)

Linux command line tools


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