Programming-for-Robotics-ROS-22Spring

• Lecturers: Edo Jelavić, Mayank Mittal, Prof. Marco Hutter

• [Webpage]

Abstract

This course gives an introduction to the Robot Operating System (ROS) including many of the available tools that are commonly used in robotics. With the help of different examples, the course should provide a good starting point for students to work with robots. They learn how to create software including simulation, to interface sensors and actuators, and to integrate control algorithms.

Objective:

• ROS architecture: Master, nodes, topics, messages, services, parameters and actions
• Console commands: Navigating and analyzing the ROS system and the catkin workspace
• Creating ROS packages: Structure, launch-​files, and best practices
• ROS C++ client library (roscpp): Creating your own ROS C++ programs
• Simulating with ROS: Gazebo simulator, robot models (URDF) and simulation environments (SDF)
• Working with visualizations (RViz) and user interface tools (rqt)
• Inside ROS: TF transformation system, time, bags
• Introduction to ROS2

Lecture 1

• Topic ROS architecture & philosophy; ROS master, nodes, and topics; Console commands; Catkin workspace and build system; Launch-files; Gazebo simulator; Programming Tools

ROS Nodes

rosrun package_name node_name
rosnode list
rosnode info node_name

ROS Topics

rostopic list
rostopic echo /topic
rostopic info /topic

ROS Messages

• Data structure defining the type of a topic
• Defined in *.msg files

rostopic type /topic
rostopic pub /topic type data
rostopic pub /chatter std_msgs/String "data: 'ETH Zurich ROS Course'"

[example: PoseStamped.msg]

ROS Wiki Message files

ROS Nodelets

**ROS Wiki Nodelet **

ROS Workspace Environment

source /opt/ros/noetic/setup.bash

catkin build System

cd ~/catkin_ws
catkin build
source devel/setup.bash

Clean the entire build and devel space with

catkin clean

The catkin workspace setup can be checked with

catkin config

For example, to set the CMake build type to Release (or Debug etc.), use:

catkin build --cmake-args -DCMAKE_BUILD_TYPE=Release

Symlink a new package to your catkin workspace

ln -s ~/git/ros_best_practices/ ~/catkin_ws/src/

ROS Launch

• lauch is a tool for launching multiple nodes (as well as setting parameters)
• Are written in XML as *.launch files
• If not yet running, launch automatically starts a roscore

roslaunch file_name.launch
roslaunch package_name file_name.launch

**ROS Wiki Launch files ** **Roslaunch tips for large projects **

<?xml version="1.0"?>
<launch>

  <!-- Launch ROS Package Template Node -->
	<node pkg="ros_package_template" type="ros_package_template" name="ros_package_template" output="screen">
		<rosparam command="load" file="$(dirname)/../config/default.yaml" />
	</node>

</launch>

<!-- Create a re-usable launch files with <arg> tag, which works like a parameter -->
<arg name="use_sim_time" default="true"/>

<!-- Use arguments in launch file with $(arg use_sim_time)-->
<group if="$(arg use_sim_time)">
	<param name="/use_sim_time" value="true" />
</group>

<!-- Include other launch files -->
<!-- Find the system path to other packages with $(find package_name)-->
<include file="$(find gazebo_ros)/launch/empty_world.launch">
	<arg name="world_name" value="$(find gazebo_plugins)/test/test_worlds/$(arg world).world"/>
    <arg name="debug" value="$(arg debug)"/>
    <arg name="physics" value="$(arg physics)"/>
</include>

Gazebo Simulator

Gazebo tutorials

Lecture 2

• Topic ROS package structure; ROS C++ client library (roscpp); ROS subscribers and publishers; ROS parameter server; RViz visualization

ROS Packages

.
├── CMakeLists.txt
├── config
│   └── default.yaml                                   //(paramter files)
├── include
│   └── ros_package_template                           //(package name)
│       ├── Algorithm.hpp
│       └── RosPackageTemplate.hpp
├── launch
│   ├── ros_package_template.launch
│   └── ros_package_template_overlying_params.launch
├── LICENSE
├── package.xml
├── README.md
├── src
│   ├── Algorithm.cpp
│   ├── RosPackageTemplate.cpp
│   └── ros_package_template_node.cpp
└── test
    ├── AlgorithmTest.cpp
    └── test_ros_package_template.cpp

• package.xml
  • Package name
  • Version Number
  • Authors
  • Dependencies on other packages
  • ...
• CmakeLists.txt
  • see example
• pacakeg_name_msgs folder

ROS C++ Client Library (roscpp)

• Initialization and spinning

  • ros::spin() and ros::spinOnce()

• Node Handle

  • Default(public) node handle

   nh_ = ros::NodeHandle();                        /namespace/topic
  

  • Private node handle

   nh_private_ = ros::NodeHandle("~");             /namespace/node/topic
  

  • Namespace node handle

   nh_eth_ = ros::NodeHandle("eth");               /namespace/eth/topic
  

  • Global node handle (not recommanded)

• Logging

  • rosconsle
  • Logging

• Subscriber and Publisher

• Object Oriented Programming

• Paramters

  ros::NodeHandle nodeHandle("~");
  std::string topic;
  if (!nodeHandle.getParam("topic", topic)) {
      ROS_ERROR("Could not find topic parameter!");
  }
  ROS_INFO_STREAM("Read topic: " 

ROS Paramter Server

• Parameters
• YAML files
• launch API
• Command line tools

   rosparam list
   rosparam get parameter_nam
   rosparam set parameter_name value
  

Rviz

Exercise 2

• pointcloud_to_laserscan
• Introduction to Working With Laser Scanner Data
• LaserScan Msg

Lecture 3

• Topic TF Transformation System; rqt User Interface; Robot models (URDF); Simulation descriptions (SDF)

TF Transformation System

• View Frames
• C++ API
  • Writing a tf2 listener
  • Using stamped datatypes with tf2::MessageFilter

rqt

• User interface
• rqt_image_view
• rqt_multiplot
• rqt_graph
• rqt_console
• rqt_logger_level

Robots Models

• Unified Robot Description Format (URDF)
• Simulation Decription Format (SDF)

Lecture 4

• Topic ROS services; ROS actions (actionlib); ROS time; ROS bags; Debugging strategies; Introduction to ROS2

ROS services

rosservice list
rosservice type /service_name
rosservice call /service_name args

rossrv show ros_tutorials/TwoInts

• .srv files
• C++ API

ROS actions (actionlib)

ROS time

ROS bags

Debug Strategies

Intro to ROS 2

Exercise 4

• ekf_localization_node

Lecture 5

• Topic Case study: Using ROS in complex real world applications