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Technical requirements

In the https://github.com/ros-mobile-robots organization on GitHub are the required ROS packages to set up a differential drive robot. One of the main software repositories is https://github.com/ros-mobile-robots/diffbot. It includes packages for simulation and the configurations and software to operate a real robot and interact with it from a development PC. For the hardware, you can build your own two- or four-wheeled differential drive robot similar to the one present in the diffbot_description package or 3D print a more stable Remo robot with the stl files in https://github.com/ros-mobile-robots/remo_description.

The next two sections describe the technical requirements for the software and hardware.

Info

This technical requirements page is here to give you an overview of what is required to get your robot up and running. You can already follow the steps in practice but they will be also mentioned in later sections (in more detail) when they are really needed.

Software requirements

The following sections give an overview about which software will be used:

More detailed software setup instructions are found in the chapter about Processing Units.

Operating System

For the development PC, you should have ROS Noetic installed on Ubuntu 20.04 or using Windows Subsystem for Linux (WSL) 2 running on Windows 11.

Note

Windows 11 is required for GUI features, such as Gazebo and RViz. WSL 2 on Windows 10 only provides command line support, although you can install an X11 server, such as VcXsrv, explained here.

On the Single Board Computer (SBC) (e.g. Raspberry Pi 4 B) that is mounted on Remo, we use Ubuntu Mate 20.04 for arm64 architecture.

Git

As the software is hosted on GitHub which uses git as a version control system it needs to be present in your used operating system.

On Ubuntu this is usually the case, which you can check with:

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$ git --version
git version 2.25.1

On Windows you need to install Git using a package manager such as chocolatey or downloading it from https://git-scm.com/downloads.

To clone large stl files from the Git repository we use git-lfs. On both Ubuntu flavors it needs to be installed with the following terminal command:

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sudo apt install git-lfs

Remote Control

On both the development PC and the SBC of the robot, you need a connection to the same local network and to enable the ssh protocol, to connect from the development PC (client) to the robot, which is running an open-ssh server. Install it on Ubuntu Mate 20.04 with the following:

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sudo apt install openssh-server

Hardware Interface

Another interface setup that is needed to work with the microcontroller, is to add your user to the dialout group on both machines, the SBC and the development PC. This can be done with the following command, followed by a system reboot:

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sudo adduser <username> dialout

Source Dependencies

When you clone the diffbot repository in a new catkin workspace, you will find two YAML files, diffbot_dev.repos and remo_robot.repos, that list required source dependencies together with their version control type, the repository address, and a relative path where these dependencies are cloned. remo_robot.repos is here to clone source dependencies on the real robot.

To make use of such YAML files and clone the listed dependencies, we use the commands from vcstool, which replaces wstool:

  1. Install vcstool using the command:

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    sudo apt install python3-vcstool
    
  2. In a new catkin workspace, clone the diffbot repository inside the src folder:

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    ros_ws/src$ git clone https://github.com/ros-mobile-robots/diffbot.git
    

    for a specific tag (e.g. 1.0.0) you can use the following command:

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    ros_ws/src$ git clone --depth 1 --branch 1.0.0 https://github.com/ros-mobile-robots/diffbot.git
    
  3. Make sure to execute the vcs import command from the root of the catkin workspace and pipe in the diffbot_dev.repos or remo_robot.repos YAML file, depending on where you execute the command, either the development PC or the SBC of Remo to clone the listed dependencies:

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    vcs import < src/diffbot/diffbot_dev.repos
    
  4. Execute the next command on the SBC of the robot:

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    vcs import < src/diffbot/remo_robot.repos
    

Binary Dependencies

After obtaining the source dependencies with vcstool, we can compile the workspace. To successfully compile the packages of the repository, binary dependencies must be installed. As the required dependencies are specified in each ROS package's package.xml, the rosdep command can install the required ROS packages from the Ubuntu repositories:

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rosdep install --from-paths src --ignore-src -r -y

Build ROS Workspace

Finally, the workspaces on the development machine and the SBC of the robot need to be built, either using catkin_make or catkin tools. catkin_make comes pre-installed with ROS.

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catkin build
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catkin_make

Hardware requirements

The repository at https://github.com/ros-mobile-robots/remo_description contains the robot description of Remo. Remo is a modular mobile robot platform, which is based on NVIDIA's JetBot. The currently available parts can be 3D printed using the provided stl files in the remo_description repository. To do this, you either need a 3D printer with a recommended build volume of 15x15x15 cm or to use a local or online 3D print service. Further details are found in hardware setup.

On the following components page you find a bill of materials and more details about each part.

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