ROS + Gazebo 機器人模擬器工作坊

Presenter: 賴柏任

https://www.facebook.com/PoJenLai

08.20.2016

Brought to you by COSCUP 2016

Who am I

• 大學時有幸透過專題接觸 ROS，並陸續發表一些 ROS 的介紹文章

https://pojenlai.wordpress.com/

• 研究所的論文內容也是用 ROS 來開發

https://github.com/Po-Jen/transparent_objects/tree/addedfeature

• 工作閒暇之餘希望可以持續學習、也提供更多資源給大家

http://blog.techbridge.cc/

http://weekly.techbridge.cc/2

Who am I

• 順便推薦一下 ROS.Taipei 社群

https://www.facebook.com/groups/122728288090359/

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Outline

• ROS Introduction

• ROS Basic Mechanism

• ROS Tool Overview

• Gazebo Introduction

• Gazebo Usage

• Navigation & SLAM

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ROS Introduction

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What is ROS ?

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http://answers.ros.org/question/12230/what-is-ros-exactly-middleware-framework-operating-system/#18055

• ROS is acronym for Robot OS, but it is not a traditional OS like Windows, Ubuntu or Mac OS

What is ROS ?

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• Before we move on, we should clarify something

• Robot software = Distributed computing system

Decision Maker

Object Recognition

Object GraspingNavigation

What is ROS ?

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• ROS is a set of tools which enables– Easy construction of distributed computing systems

(Programs can be individually designed and easily connected at runtime)

– Code reuse

– Configuring, starting, introspecting, debugging, visualizing, logging, testing, and stopping distributed computing systems

Why is ROS preferred ?

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• It encourages users not to reinvent the wheel

Why is ROS preferred ?

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• Many open-sourced libraries

– SLAM (OpenSLAM)

– Real-time control(OROCOS)

– Path Planning (Openrave)

– Vision (OpenCV, PCL)

– 3D Simulator (Gazebo)

– 3D Visualizer (Rviz)

Why is ROS preferred ?

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• Package can be written in multiple programming languages

– C++

– Python

– Lisp

• And many more experimental support

– C#, Go, Haskell, Java, Node.js, Lua, R, Ruby

– http://wiki.ros.org/Client%20Libraries

Can ROS be used on different robot?

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• Of course!

• Check all robots using ROS - http://wiki.ros.org/Robots

https://vimeo.com/146183080

ROS Basic Mechanism & Tool

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建立ROS workspace

• 建立一個空的環境並編譯

– $ mkdir -p ~/catkin_ws/src

– $ cd ~/catkin_ws/src

– $ catkin_init_workspace

– $ cd ~/catkin_ws

– $ catkin_make

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File System

• Basic unit - package

– CMakeLists.txt

– package.xml

• ROS package 使用catkin 這工具來進行編譯

– 按照 ROS 規定的格式寫code，就可以用catkin編譯

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rosbuild v.s. catkin

• rosbuild

– ROS Groovy之前的編譯系統

– 有部分package仍未porting到catkin上，故仍需略懂

– 所有原始碼和編譯後的檔案都在同一資料夾下

• Catkin

– ROS Groovy之後的編譯系統

– 原始碼和編譯後的檔案分離

• 接著直接來寫個node看看怎麼編譯

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ROS Node

• Basic unit of program

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Decision Maker

Object Recognition

Object GraspingNavigation

Node 1

Node 2 Node 3 Node 4

讓我們開始實作

• 你們需要的code應該都在這了

– https://github.com/Po-Jen/coscup2016-ROS-workshop

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Create our first package & write a node

• 步驟先全部列在這，接著讓我們一步步來做– cd ~/catkin_ws/src

catkin_create_pkg coscup_1_node rospycd coscup_1_nodevim src/node.pychmod +x src/node.pycd ../..catkin_makesource devel/setup.bashroscorerosrun coscup_1_node node.pyrqt_graph

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ROS Master

• How do node knows each other? => ROS Master

• Control the graph of nodes

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rqt_graph

• Visualization of nodes and topics

• Part of rqt (integrates lots of debugging tools)

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How do ROS node communicate?

• ROS master as a message hub?

– What if there are many nodes?

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How do ROS node communicate?

• Let nodes communicates with each other directly

– Topic, Service, ActionLib

• If ROS does not exists

– Socket

– Shared memory

– We have to take care of these tedious work.

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ROS Topic

• Publisher/Subscriber mechanism (topic == bucket)

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Perception

ObjectRecognition

Semantic Map

Camera data

Recognition result

rostopic• 寫一個publisher (一直丟字串到topic_name這個topic)

– catkin_create_pkg coscup_2_topic rospy std_msgscd coscup_2_topicvim src/publisher.pychmod +x src/publisher.pycd ../..catkin_makesource devel/setup.bashroscorerosrun coscup_2_topic publisher.pyrqt_graphrostopic echo topic_namerostopic listrostopic list | grep topic

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rqt_graph

• Now, it should looks like

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rostopic

• 寫一個subscriber (從topic_name這個topic取出data)– cd ~/catkin_ws/src

cd coscup_2_topicvim src/subscriber.pychmod +x src/subscriber.pyrosrun coscup_2_node subscriber.pyrqt

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rqt_graph

• Now, it should looks like

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rqt

• We can try console

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Define our own msg for topic

• 創建一個只有一個int的msg– cd ~/catkin_ws/src

cd coscup_2_topicmkdir msgvim msg/Num.msgvim package.xmlvim CMakeLists.txtcd ../..catkin_makesource devel/setup.bashrosmsg show coscup_2_topic/Num

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package.xml

• Add build dependency and run dependency

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CMakeLists.txt (1)

• Add package dependency

• Or you can

– catkin_create_pkg coscup_2_topic rospy std_msgsmessage_generation

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CMakeLists.txt (2)

• Add build dependency

• Add msg file

• We use std_msgs/int64 in our msg file

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Publish自己寫的msg

• 步驟– cd ~/catkin_ws/src/coscup_2_topic/

vim src/my_msg_publisher.py

chmod +x src/my_msg_publisher.py

rosrun coscup_2_topic my_msg_publisher.py

rostopic echo my_msg_topic_name

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One more example

• geometry_msgs/Twist

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One more example

• geometry_msgs/Vector3

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How is the abstraction implemented?

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/cmd_veltopic

Base Controller

Motor Speed

geometry_msgs/Twist

將速度和角速度轉成馬達命令

ROS Service

• Query/Response Style

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Object Recognition

Brain

1 query 2 response

ROS Service

• 建立一個自己的srv格式– cd ~/catkin_ws/src

catkin_create_pkg coscup_3_service rospy std_msgscd coscup_3_servicemkdir srvvim srv/AddTwoInts.srvvim package.xmlvim CMakeLists.txtcd ../..catkin_makesource devel/setup.bashrossrv show coscup_3_service/AddTwoInts

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package.xml

• Add build dependency and run dependency

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CMakeLists.txt

• Add service file

• Add std_msgs dependency

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ROS Service

• 寫一個server

– cd coscup_3_servicevim src/add_two_ints_server.pycd ../..source devel/setup.bashchmod +x src/add_two_ints_server.py rosrun coscup_3_service add_two_ints_server.py

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ROS Service

• 寫一個client，送出request給server

– cd coscup_3_servicevim src/add_two_ints_client.pychmod +x src/add_two_ints_client.pyrun coscup_3_service add_two_ints_client.py 5 6

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Rviz

• An important tool for data visualization

• 先啟動你們的Rviz– $ sudo apt-get install ros-indigo-rviz-*

– $ roscore

– $ rviz

• Will be revisited when we use Gazebo

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Find out more on ROS Cheat Sheet

• https://github.com/ros/cheatsheet45

Gazebo Introduction

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What is Gazebo ?

• 3D物理模擬器

–機器人控制

–環境模擬

–物體物理特性模擬

• 用途廣泛

–DARPA Challenge也是用Gazebo來開發

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看個影片就有概念了

• https://www.youtube.com/watch?v=_8AhNWKzv2k

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Gazebo Usage

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Started Gazebo

• 先確保該安裝的東西都有被安裝– $ sudo apt-get install ros-indigo-gazebo-*

– $ sudo apt-get install ros-indigo-pr2-*

• 啟動Gazebo– $ gazebo

• 加入一些模型並存成world file

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Play around with Rviz

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SLAM & Navigation

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先來個 SLAM 的 DEMO

• Gazebo 開啟 PR2 進行 SLAM

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讓我們來實際操作

• Gazebo 開啟 PR2 進行 SLAM– $ roslaunch pr2_gazebo pr2_empty_world.launch

– $ 加入自己喜歡的模型

– $ roslaunch pr2_build_map.launch

– $ rviz

– $ roslaunch pr2_teleop teleop_keyboard.launch

– $ rosrun map_server map_saver

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SLAM 演算法簡介

• gmapping package (grid mapping)

http://wiki.ros.org/gmapping

• Grid map–Map is presented by 2D array

– Each grid• 0: free

• 1: occupied

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Map representation

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Map representation

• Given sensor data zt and the poses of the sensor xt, estimate the map

• 推導就不細講了– http://ais.informatik.uni-

freiburg.de/teaching/ws12/mapping/pdf/slam11-gridmaps-4.pdf

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Resources you can leverage

• ROS wiki

http://wiki.ros.org/

• ROS Answers

http://answers.ros.org/questions/

• Gazebo Answers

http://answers.gazebosim.org/questions/

• ROS Taipei 中文資源整理

https://hackpad.com/-ROS-Blog--lnDeWhHXH4T

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ROS 2.0

• 欲改進的點

– 多機器人協作 (ROS 1.0是for PR2開發的)

– 嵌入式平台開發 (不必再透過一層額外driver)

– real-time系統 (能有更精準的控制能力)

– 適用於產品開發 (原本偏向學術研究用)

– 設計模式的建立

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ROS 2.0 學習資源

• Official website

– http://design.ros2.org/

• ROS 2.0 中文翻譯( under construction…)

– http://po-jen.github.io/design/

• Tutorials from Erle-Robotics

– http://erlerobotics.com/docs/Robot_Operating_System/ROS_2/Tutorials/index.html

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Thanks for joining, you guys rock!

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Appendix I如何使用第三方提供的

package

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Example - ros_caffe

• Github page

– https://github.com/tzutalin/ros_caffe

• Tutorial

– http://www.artificialhumancompanions.com/integrating-ros-caffe-opencv-on-the-autonomous-deep-learning-robot/

• 使用topic_tools轉換Gazebo的PR2的topic name– rosrun topic_tools relay /wide_stereo/left/image_raw

/camera/rgb/image_raw

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