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ROS Notes

Some notes on installing and using ROS (Robot Operating System):

Overview

The basic steps for bringing up ROS are:

  1. Reading up about configuring WiFi networks.
  2. Install ROS on a virtual machine running on your workstation.
    • Run robot navigation simulator on your workstation.
  3. Install ROS onto a Raspberry Pi 3B or 3B+.
    • Run some sort of "hello world" program.
  4. Install a Raspberry Pi camera on to the RasPi.
    • Run fiducial software on your Raspberry Pi.
  5. Install Raspberry Pi on Loki.
    • Run keyboard tele-operation on Loki
  6. Write first ROS Python Program and run it on Loki
    • Drive robot forward and backward.

Without any further adieu, let's get started.

Configuring WiFi Networks

Most ROS robots are mobile in that they move around the environment. What this means is that ROS relies heavily on the standard internet protocols with a particular emphasis on WiFi wireless networking. This allows you control, monitor, and debug your ROS robot from the comfort your development workstation (i.e. a desktop or laptop), while the ROS mobile robot is moving around on the floor.

For the internet, each computer attached to the network is given an address. For IPv4 (Internet Protocol version 4), the address is the form A.B.C.D, where A, B, C, and D each represent an 8-bit byte as a decimal number (e.g. 192.168.0.123, 10.234.7.6, etc.) Since IP addresses change, the internet has an additional level indirection called DNS (Domain Name Service) that maps from a human readable name to the IP address number (e.g google.com => 216.58.195.78.)

A complication occurs with computers that attach to the network via WiFi. WiFi typically uses a DHCP (Dynamic Host Configuration Protocol) server to assign IP addresses to computers that log into a network using WiFi. When the DHCP server is configured, it is setup to allocate IP addresses from a range (e.g. 192.168.0.100 through 192.168.0.150.) The problem that ensues is that when your ROS robot logs into a WiFi network, you do not actually know which IP address the DHCP picked to assign to it.

The solution to not knowing your ROS Robot IP address number, is to use a set of network technologies that goes by the name zeroconf. What this does is give each robot and development workstation computer a unique DNS name. The primary requirement for zeroconf is that all computers be connected to the same LAN (Local Area Network.)

This begs the question of "just what is a local area network?" The technical answer is that a local area network is a set of computer/network nodes that have the same basic internet address (e.g 192.168.0.x, 10.123.x.x, etc.) In practical terms, if you have a WiFi router, all computers that log in via WiFi AND all computers that are hardwired connected to the LAN ports on the router are on the same local area network. (Yes, there are exceptions, but for most people, the previous statement is correct.)

In order for zeroconf to work, each development workstation and robot MUST be given a different host name. The reason for this is because, zeroconf references each machine by HOSTNAME.local, where HOSTNAME is the machine's host name. If there are two or more machines with the same HOSTNAME, total confusion occurs.

The bottom line is that zeroconf is really important and in order for it to work you must ensure that the host name for all of your robots and development workstations unique (i.e. different from one another.) For example, if you have a robot lab with 10 robots and 20 development workstations, you will need to have a total of 30 different host names.

Install ROS on Virtual Machine Running on Your Development Workstation

A development workstation is a desktop or laptop with a 64-bit Intel processor on it.

  • VirtualBox Installation:

    • Download VirtualBox Software for you workstation.
    • Read Virtual Box Documentation.
    • Download Ubiquity Robotics Virtual Machine Image
    • Load Ubiquity Robotics Virtual Machine Image into VirtualBox and start it up.
      • Be sure that the virtual machine network is configured in "bridged mode"!!!
    • Login as user ubuntu and with a password ubuntu:
    • Click the terminal window icon (left column with black rectangle and carret) to open terminal.
    • Become superuser sudo -s (type in password of ubuntu).
    • From VirtualBox menu bar select [Devices=>Insert Guest Additions CD Image...].
    • Change directory to guest additions directory (cd /media/ubuntu/VBOXADD*). {Is this correct?}
    • Install guest additions (sudo ./runasroot.sh). {Is this correct?}

  • Do some system administration

    • Make sure you are still logged in as root by running sudo -s (type in password of ubuntu).
    • Decide on the host name for your virtual machine. You could use your first name followed by the letters ws (e.g. alicews, bobws, etc.) In the instructions below, replace NEWHOSTNAME with whatever use selected. Use all lower case letters.
      • Copy NEWHOSTNAME into /etc/hostname via echo NEWHOSTNAME > /etc/hostname.
      • Use nano /etc/hosts to edit /etc/hosts. Replace line with 127.0.1.1 ubuntu with line 127.0.1.1 NEWHOSTNAME NEWHOSTNAME.local.
    • Decide on your user account name. In a robotics lab situation, we recommend using your first name followed by your last name (e.g. alicesmith, bobliu, etc.) In a non-robotics lab situation, your first name should be good enough. Always use all lower case.
    • Create new user account (in the instructions below USER is used; pick something different):
      • adduser USER # Provide password and other information. Remember the password.
      • adduser USER sudo # Adds you to the sudo group that lets you use sudo program
      • adduser USER dailout # Adds you to the dailout group that lets you use a terminal emulator
    • Reboot the virtual machine using sudo reboot
    • Login it your new USER account with the password you specified previously.
    • Verify that sudo works by typing sudo ls. (Specify your password when prompted.)
    • Update your system by doing the following:
      • sudo apt update
      • sudo apt upgrade

  • Configure your virtual machine to suit you preferences. For wayne this is:

    • Install kubuntu plasma (Wayne perfers KDE; everybody else can skip this step)
      • sudo add-apt-repository ppa:kubuntu-ppa/backports
      • sudo apt install -y kubuntu-desktop
        • Select lightdm for the display manager when prompted
      • Logout and log back in under plasma
      • Set keyboard bindings using systems settings
    • Install your favorite editor (e.g. sudo apt-get install vim)

  • Create and configure ROS catkin workspace:

    • Run mkdir -p ~/catkin_ws/src

    • Clone ROS_NOTES repositiory into that newly created directory

      cd ~/catkin/ws/src

      git clone https://github.com/waynegramlich/ROS_Notes.git

    • Copy .ros_setup.bash up to your home directory

      cp ~/catkin/ws/src/ROS_NOTES/.ros_setup.bash ~

    • Edit your ~/.bashrc to have the source ~/.ros_setup.bash in it.

    • Run source ~/.bashrc to force you current shell to have ROS stuff in it.

    • Run catkin_make

  • Verify that ROS runs on virtual machine:

    • Install some launch files into your ROS workspace:

      cd ~/catkin_ws/src

      git clone https://github.com/UbiquityRobotics/ubiquity_launches.git

    • Install some missing packages:

      sudo apt-get install ros-kinetic-turtlebot-description
sudo apt-get install ros-kinetic-robot-state-publisher
sudo apt-get install ros-kinetic-yocs-velocity-smoother
sudo apt-get install ros-kinetic-yocs-cmd-vel-mux
sudo apt-get install ros-kobuki-safety-controller

      cd ~/catkin_ws catkin_make

    • Run robot simulator (./ubiquity_launches/bin/keyboard_navigate)

      • When RVIZ comes up select [2D Nav Goal].
      • User mouse click mouse in middle of maze and drop an arrow that points in any direction.
      • Watch the robot drive to the destination.
      • Woo Hoo!
      • Use [File=>Close] to kill the two windows.
      • Type Cntrl-C to kill off everything else.

Install ROS onto a Raspberry Pi 3B or 3B+

  • Download ubiquity robotics Raspberry Pi image.

    • Create a ~/downloads directory (mkdir -p ~/downloads).

    • Change to the ~/downloads directory (cd ~/downloads).

    • Download the Raspberry Pi Image with the following command:

      wget https://cdn.ubiquityrobotics.net/2018-06-07-ubiquity-xenial-lxde-raspberry-pi.img.xz

      (Note: this link may change in the future)

    • Run the Gnome Disk Utility (gnome-disks).

    • Plug a USB to SD/micro-SD device into free USB port on your workstation. Make sure you use one of the older USB to SD/micro-SD devices, they work better.

    • On the VirtualBox menu bar, select [Devices=>USB=>XXX] where XXX coresponds to the device you just plugged in. XXX will be something like Generic Storage Device.

    • The storage device should show up in the disk utility as something like VBOX HARDDISK.

    • Using the settings icon in the upper right corner of the disk utility (i.e. 3 short horizontal lines), select [# => Restore Disk Image].

    • Use the file chooser to select ~/downloads/2018-06-02-ubiquity-xenial-lxde-raspberry-pi.img.xz and click [Open] followed by Start Restoring....

  • Boot The Raspberry Pi image.

    • Boot the Raspberry Pi:
      • The most reliable way to boot the image is to find an HDMI cable, a USB mouse, a USB keyboard and plug them into the Raspberry Pi.
      • Plug in the micro-SD card.
      • Apply power to the Raspberry Pi.
      • After the image boots login as user ubuntu and password ubuntu.
      • Open a terminal window.

  • Do the same system administration as you did for you workstation. Make sure you select a NEWHOSTNAME that is different from you workstation. You should use the same USER account. Create the catkin workspace, but do not download either the ROS_Notes or ubiquity_launches packages. Do not try to run the robot simulator.

  • Run pifi to configure your WiFi...

Install Raspberry Pi camera onto RasPi

Install Raspberry Pi on Loki

Install Fiducials

Read up about fiducials.

Install some packages:

    sudo apt-get install ros-kinetic-fiducials
    (cd ~/catkin_ws ; catkin_make)

Get some 8.5" x 11" adhesive labels from Amazon. We want these to be removable labels. It is usually cheaper to buy a couple of boxes and try them out to figure out how removable they are.

Write first ROS Python Program and run it on Loki

  • Install AVR/Arduino tool chain on the workstation:

      sudo apt-get install arduino
  sudo apt-get install binutils gcc-avr avr-libc uisp avrdude flex byacc bison

  • Install Arduino, Arduino-Makefile, and bus_loki repos into your workstation:

      cd ~/catkin_ws/src

    git clone https://github.com/UbiquityRobotics/Arduino.git git clone https://github.com/UbiquityRobotics/Arduino-Makefile.git git clonehttps://github.com/UbiquityRobotics/bus_loki.git

  • Build the Loki firmware.

      cd bus_loki/ref_f

    make clean make

  • Plug 3.3V USB DFRobot USB to serial connector into correct connector.

  • Type make upload to force the firmware into the Loki.

LocalWords: IP HOSTNAME