SD Robotics Club at RoboLink: ROS Workshop

QuickStart Commands:

rostopic list - Displays a list of available topics, Topics are like channels, through which messages flow.

rostopic echo /topic - Current values from the messages flowing through this topic

rosparam list - shows variables / settings

rosmake node - Makes a node. A node is like a program, or more accuratly, a programs folder. You only need to make it if it's not already compiled.

rosrun node nodename - Runs a node. The nodename is the name of the binary. It's normally the same name as the node. E.g. rosrun rviz rviz

roscd node - cd to the folder of the node. Note that you don't have to be in the folder to run the binary... rosrun seems to know where all the nodes are. In the folders, messages will be in the msg folder. They will be in .msg files and the files contain the types of the data in that topic.

The Turtle Tutorial

From:
http://wiki.ros.org/ROS/Tutorials/UnderstandingTopics

Open a new terminal window (press Ctrl+Alt+T see Linux notes below) and type roscore. The core should start and no prompt will be returned. Minimize the window. On a real robot, this would be started automatically when the OS started.

Open another terminal window and type rosrun turtlesim turtlesim_node you should see the TurtleSim screen with the turtle in the center. You can minimize the terminal window, but leave the TurtleSim screen up.

Open another terminal window and type rosrun turtlesim turtle_teleop_key This terminal window will pick up arrow key presses (when you have the window selecte) and send them to the turtle. Make sure it's visable, but you can re-size it to make it smaller.

Open another terminal window and type rostopic list you should see the new turtle topics. For example, you can type rostopic echo /turtle1/cmd_vel and then switch back to the turtle_teleop_key window and press the arrow keys to see the changes in velocity of the turtle. (Note: in Xbuntu, When you minimize a program, it goes to the TOP, not the bottom.)

Open another terminal window and type:
sudo apt-get install ros-jade-rqt
sudo apt-get install ros--rqt-common-plugins
rosrun rqt_graph rqt_graph

This should creates a dynamic graph of what's going on in the system. If you place your mouse over /turtle1/command_velocity it will highlight the ROS nodes (in circles) and topics (on lines). As you can see, the turtlesim_node and the turtle_teleop_key nodes are communicating on the topic named /turtle1/command_velocity.

Additional Tools

rosrun rviz rvis - 3D Robot Visualizer

MoveIt! is state of the art software for mobile manipulation, incorporating the latest advances in motion planning, manipulation, 3D perception, kinematics, control and navigation. It provides an easy-to-use platform for developing advanced robotics applications, evaluating new robot designs and building integrated robotics products for industrial, commercial, R&D and other domains.
moveit.ros.org

SMACH is a state machine for high level behaviors.
http://wiki.ros.org/smach

Setup:

Assuming you have a 64 bit processor running Windows, Macintosh, or Solaris:

1. Download and install VirtualBox from
   https://www.virtualbox.org/wiki/Downloads
2. Download Ubuntu 14.04.3 LTS (Trusty Tahr) 64-bit PC (AMD64) desktop image iso
   http://releases.ubuntu.com/14.04/ubuntu-14.04.3-desktop-amd64.iso (this is 1GB or several hours on a good connection)
3. Create new VirtualBox VM with 20GB drive (can be dynamic) - for RAM I did 4096MB.
   • New, give it a name e.g. "Ubuntu" and select the OS type: Linux... the Version should default to Ubuntu (64-Bit)
   • Change the memory to 4096 if you have 8GB, or half of your actual RAM.
   • Next, create a virtual hard dist now, use VDI, Next, Dynamically allocated, Next, hit the little folder with the green upchuck to change the location and change the size to 20GB.
4. Attach iso to storage of new VM (so it will boot from image)
   • Devices / Optical Drive / browse to the .iso file from above.
5. Boot VM and install Ubuntu (pick default options for installation questions).
   • Press the green start arrow. Ubuntu installer should start from the ISO image in the fake CD drive and start going through the install. Standard stuff... pick a name, set a password, language, etc...
   • The scary part is telling Ubuntu to format the hard drive and install. Don't worry, that's the "fake" hard drive you make for the VM.
   • When it asks you to restart, you have to force remove the ISO image from the Virtual CD drive, Devices / Optical Drive / Remove disk... Force... then Machine / Reset. The restart hangs because it don't let go of the CD.
6. Reboot into Ubuntu and install VM guest additions
   • Click Devices / Insert Guest Additions CD Image, and Ubutu will ask you if you want to run. You can't see the Run button because it's off the tiny screen, but it's to the right of Cancel. Then you will have to enter the password you chose and hit enter. That runs for a while, then waits for you to press enter, which you can't see because it's off the bottom of the tiny screen. Scroll down.
   • Restart Ubutu with the gear in the upper right corner, Shutdown, Restart.
   • Now you can change the screen size with View / Virtual Screen 1 / resize.
     
     Some notes about Linux:
     • Ctrl + C to get out of stuff.
     • Hit Ctrl + Alt + T for a terminal window. If you see an instruction to enter a command, like $ cd somefolder, the $ is the prompt and you don't enter that. You get to the $ prompt by opening a terminal window.
     • On standard Ubuntu, there is a list of common programs on the left side of the screen. Xbuntu does away with that. Under Xbuntu:
     • The main menu is in the upper right corner. It sort of looks like a dead white animal on a blue background. You can get to a browser there.
     • When you minimize a program, it goes to the TOP, not the bottom.
     • From the VM window, Devices, Shared Clipboard, set to Bidirectional, allows you to Ctrl + Shift + V paste, or Edit / Paste in the terminal window
       
7. Install Xubuntu $ sudo apt-get install xubuntu-desktop
   • Hit Ctrl + Alt + T for a terminal window.
   • type in
     sudo apt-get install xubuntu-desktop
     and press enter. It will ask for your password again, and then ask for your approval to use more disk space (why?) by enterying Y. It works for a LONG time. Is xubunut really required for this?
8. Reboot again and install ROS Jade (now the fun really starts)
   http://wiki.ros.org/jade/Installation/Ubuntu
   • (P.S. Devices, Shared Clipboard, Bidirectional, allows you to Ctrl + Shift + V paste, or Edit / Paste in the terminal window)
   • Ctrl + Alt +T again for a terminal window. Just stay in it after this.
   • Enter (or paste)
     sudo sh -c 'echo "deb http://packages.ros.org/ros/ubuntu $(lsb_release -sc) main" > /etc/apt/sources.list.d/ros-latest.list'
     it will ask for your password again, but as long as you keep the same terminal open, that's it.
   • sudo apt-key adv --keyserver hkp://pool.sks-keyservers.net --recv-key 0xB01FA116
     bunch of junk with imported: 1 at the end.
   • sudo apt-get update
     That takes a while.
   • I'm assuming the FULL is what what want.
     sudo apt-get install ros-jade-desktop-full
     Confirm the extra space with Y. That takes a LONG time.
   • sudo rosdep init
   • rosdep update
   • echo "source /opt/ros/jade/setup.bash" >> ~/.bashrc
   • source ~/.bashrc
   • sudo apt-get install python-rosinstall
     Y to continue. Takes a bit.

See also:

• http://wiki.ros.org/ROS/Higher-Level Concepts
• http://wiki.ros.org/ROS/Tutorials
• http://wiki.ros.org/turtlesim and
  http://wiki.ros.org/ROS/Tutorials/UnderstandingTopics
• http://moveit.ros.org/
• http://juxi.net/workshop/ros-2018/ a simular but more up to date and more extensive intro to ROS.

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