ROBOT OPERATING SYSTEM AN INTRODUCTION BY SYED MUHAMMAD ABBAS LUMS SCHOOL OF SCIENCE & ENGINEERING, PAKISTAN

Transcription

1 ROBOT OPERATING SYSTEM AN INTRODUCTION BY SYED MUHAMMAD ABBAS LUMS SCHOOL OF SCIENCE & ENGINEERING, PAKISTAN

2 ROBOTICS EVOLUTION SIMPLIFIED! Micro Controller Brain Sumo Line follower Maze solver Firefighting... Higher level logic benefits from PC Magellan Robot arm... Higher level logic requires PC LEAF SLAM & more.

3 BUT SOON YOU HIT A CEILING SINCE... You develop Your own logging You write your own messaging infrastructure (protocols) Your own coordinate system transformations Your own joystick/keyboard driver Your own basic navigation logic Your own basic vision system... And you never catch up

4 STANDARD SOFTWARE REQUIREMENTS Standardized Layers System software abstracts hardware Applications leverage other applications (e.g. database, web server) and huge sets of libraries.

5 THANKS TO ROS! Open source system software for robotics.

6 ROS OBJECTIVE

7 ABOUT ROS Headed up by Willow Garage ( Four years old The software basis of Willow Garage s PR2 Exponential adoption

8 ROS GOALS ROS is to support code reuse in robotics research and development ROS is a distributed framework of processes (aka Nodes) Enables executables to be individually designed and loosely coupled at runtime Processes can be grouped into Packages and Stacks for easy understanding and reuse.

9 ROS GOALS Thin: ROS is designed to be as thin as possible code written for ROS can be used with other robot software frameworks Philosophy: ROS libraries should have clean functional interfaces Easy testing: ROS has a builtin unit/integration test framework called rostest Scaling: ROS is appropriate for large runtime systems and for large development processes

10 ROS REPOSITORIES EXPANSION

11 REPOSITERIES LOCATION

12 ROS PACKAGES EXPANSION

13 ROS OVERVIEW: A META OPERATING SYSTEM

14 ROS OVERVIEW: SOFTWARE ORGANIZATION

15 ROS SUPPORTED ROBOTS

16 FIELD ROBOTICS ICONS.. utexas-art-ros-pkg ART autonomous vehicle by researchers from the University of Texas at Austin Junior, most famously finished in a close second at the DARPA Urban Challenge

17 ROS WORKS EVEN UNDER WATERS University of Zurich Underwater Vehicle a new type of sailboat

18 ROS IN AIR

19 SUPPORT? Multi language support C++, python, Java, Octave, Lisp, RxLab Supported Platform Experimental Platforms

20 CONCEPT ROS has three levels of concepts: Filesystem level: ROS resources on disk. Computation Graph level: peer-to-peer network of ROS processes. Community level: You, me, them, everybody, everybody (repositeries)

21 CAPABILITIES

22 FILESYSTEM LEVEL ROS resources that you encounter on disk, such as: Packages: Packages are the main unit for organizing software in ROS, e.g. ROS runtime processes (nodes), ROS-dependent library, datasets, configuration files. Manifests: Manifests (manifest.xml) provide metadata about a package (e.g. dependencies, compiler flags). Stacks: Stacks are collections of packages that provide aggregate functionality, such as a navigation stack. Stacks Manifests: Stack manifests (stack.xml) provide data about a stack (e.g. dependencies on other stacks). Message (msg) Type: Defines the data structure of the message to be sent in ROS. Service (srv)type: Defines the request and response DS for service.

23 AGAIN FOR BETTER UNDERSTANDING!

24 NAVIGATING THE ROS FILESYSTEM Location on Ubuntu: /opt/ros/diamondback/common

25 CONCEPTS: COMPUTATION GRAPH LEVEL Computation Graph: Peer-to-peer network of ROS processes that are processing data together. The basic Computation Graph concepts of ROS are: nodes master parameter server messages topics services And bags.

26 COMPUTATION GRAPH: NODES Nodes are processes that perform computation. ROS is designed to be modular at a fine-grained scale: a robot control system will usually comprise many nodes. For example, one node controls a laser range-finder, another node performs localization. A ROS node is written with the use of a ROS client library, such as roscpp or rospy.

27 COMPUTATION GRAPH: MASTER Provides name registration and lookup to the rest of the Computation Graph. Without the Master, nodes would not be able to find each other, exchange messages, or invoke services. The master stores topics and services registration information for ROS nodes.

28 COMPUTATION GRAPH: PARAMETER SERVER The Parameter Server allows data to be stored by key in a central location. It is part of the Master.

29 COMPUTATION GRAPH: MESSAGES Messages: Nodes communicate with each other by passing messages. A message is simply a data structure of typed fields. Standard primitive types (integer, floating point, boolean, etc.) are supported, as are arrays of primitive types. Messages can include arbitrarily nested structures and arrays (much like C structs).

30 COMPUTATION GRAPH: TOPICS A node sends out a message by publishing it to a given topic. The topic is a name that is used to identify the content of the message. A node that is interested in a certain kind of data will subscribe to the appropriate topic. In general, publishers and subscribers are not aware of each others existence (decoupling).

31 COMPUTATION GRAPH: SERVICES Publish / subscribe model: many-to-many (messages) Request / reply: services Pair of message structures: one for the request and one for the reply. A providing node offers a service under a name and a client uses the service by sending the request message and awaiting the reply.

32 COMPUTATION GRAPH: MESSAGES VS. SERVICES

33 COMPUTATION GRAPH: MESSAGES VS. SERVICES 1:n communication Non-blocking 1:1 communication blocking

34 COMPUTATION GRAPH: BAGS Bags are a format for saving and playing back ROS message data. Mechanism for storing data such as sensor data (for developing and testing algorithms).

35 ROS COMMUNITY LEVEL Enable separate communities to exchange software and knowledge. Resources: Distributions: ROS Distributions are collections of versioned stacks that you can install. (Comparable to Linux distributions). Repositories: Different institutions can develop and release their own robot software components. The ROS Wiki: The ROS community Wiki is the main forum for documenting information about ROS (where most of this information comes from!). Bug Ticket System Mailing Lists: ros-users mailing list. Blog

36 HIGHER-LEVEL CONCEPTS Coordinate Frames/Transforms: The tf package provides a distributed, ROS-based framework for calculating the positions of multiple coordinate frames over time. Actions/Tasks: The actionlib package defines a common, topic-based interface for pre-emptible tasks in ROS. Message Ontology: The common_msgs stack provide a base message ontology for robotic systems. These includes messages for actions (actionlib_msgs), diagnostics (diagnostic_msgs), geometric primitives (geometry_msgs), robot navigation (nav_msgs), and common sensors (sensor_msgs), such as laser range finders, cameras, point clouds. Plugins : pluginlib provides a library for dynamically loading libraries in C++ code.

37 HIGHER LEVEL CONCEPTS Filters: The filters package provides a C++ library for processing data using a sequence of filters. Robot Model: The URDF(Unified Robot Description Format)package defines an XML format for representing a robot model and provides a C++ parser.

38 HIGHER LEVEL CONCEPT The ActionClient and ActionServer communicate via a "ROS Action Protocol", which is built on top of ROS messages.

39 HYBRID P2P ARCHITECTURE

40 SOME COMMANDS roscore rxgraph rostopic echo /turtle1/command_velocity rxplot 'displays a scrolling time plot of the data published on topics' rxconsole rosbag record -a rosbag play <your bagfile>

41 RXGRAPH

42 RXCONSOLE

43 CREATING A PACKAGE rospack find roscreate-pkg [package_name] [depend1] [depend2] [depend3] Example: rospack depends beginner_tutorials rosmake [package1] [package2] [package3] rosdep install turtle_teleop rxtools

44 WRITING A PUBLISHER mkdir msg rosrun beginner_tutorials talker name:=talker rosrun beginner_tutorials listener name:=listener

45 WRITING A SERVICE mkdir srv rosbuild_add_executable(add_two_ints_server src/add_two_ints_server.cpp) rosbuild_add_executable(add_two_ints_client src/add_two_ints_client.cpp) rosrun beginner_tutorials add_two_ints_server rosrun beginner_tutorials add_two_ints_client 5

46 BUILDING YOUR OWN ROBOT Create your own urdf file (.xml)

47 BUILDING YOUR OWN ROBOT Create the tree structure

48 BUILDING YOUR OWN ROBOT Add the dimensions

49 BUILDING YOU OWN ROBOT Completing the Kinematics So, if you look at joint2, you see it rotates around the positive Y-axis. So, simple add the following xml to the joint element:

50 RVIZ

51 RVIZ

52 GAZEBO WITH ROS

53 GAZEBO WITH ROS

54 EXTERNAL SUPPORT

55 EXTERNAL SUPPORT

56 DOCUMENTATION

57 HOME SEARCH ENGINE

58 ROS AND ANDROID +

59 POINT CLOUD GENERATION Thanks to PCL

60 POINT CLOUD LIBRARY

61 RGBD SLAM

62 SLAM

63 SLAM RESULTS

64 TERRIAN MAPPING

65 WE ARE PROUD TO SAY THAT.

66 THE END..!