Research Track I - Second Assignment

ROS Robot Simulator with Gazebo Simulation Environment - Delucchi Manuel (S4803977)

Project Description

It is the purpose of this assignment to develop a ROS package containing three ROS nodes that provide a way to interact with the environment in Gazebo.

The aim of the assignment is to create a package, in which the following nodes will be developed:

• Node A: A node that implements an action client, allowing the user to set a target (x, y) or to cancel it. The node also publishes the robot position and velocity as a custom message (x, y, vel_x, vel_z), by relying on the values published on the topic /odom;
• Node B: A service node that, when called, prints the number of goals reached and cancelled;
• Node C: A node that subscribes to the robot’s position and velocity (using the custom message) and prints the distance of the robot from the target and the robot’s average speed. The frequency at which the information is published can be set via a parameter in the launch file.

Then, it is asked to create a launch file to start the whole simulation.

Create and setup a Catkin Workspace

A catkin (ROS) workspace is a directory in which you can create or modify existing catkin packages. We will label our catkin workspace catkin_ws. To create the catkin workspace, type the following commands in the Terminal:

mkdir catkin_ws
cd catkin_ws
mkdir src
catkin_make

This will allow us to create a new folder in the home directory called catkin_ws by using the mkdir command. Then we create a source src folder inside the catkin workspace folder. Once done, make sure to use the command catkin_make inside the catkin_ws folder in order to init the catkin workspace. If you view your current directory contents, you should now have the devel and build folders. Inside the devel folder there are now several setup.*sh files.

Then, we will need to source the setup.bash file to overlay this workspace on top of our ROS environment. In order to do this, it is necessary to go back in your home directory with the cd command and then type:

source ~/catkin_ws/devel/setup.bash

Remember to add this source command to your .bashrc file under the source line of the global ROS installation. This is important so as to use your code with ROS functionalities. In order to access the .bashrc file type the following command:

gedit ~/.bashrc

How to run the simulation

Start by installing the xterm library. This can be done running on terminal the following code:

sudo apt-get install xterm

Note: xterm is the standard terminal emulator in the Unix-like environment. A user can have multiple xterm sessions started on one or more displays, which provide an input/output system for the processes launched.

Finally, you can move inside the package and clone the repository by typing the command:

git clone https://github.com/manudelu/ResearchTrackI_Assignment2.git

Note: Important!! You have to chnage the main folder name from ResearchTrackI_Assignment2 to assignment_2_2022

Then, since inside the source folder there is new content, you need to type the command catkin_make inside the catkin_ws folder:

cd
cd catkin_ws
catkin_make

Open a new tab in the terminal and run the whole project by running the launch file:

roslaunch assignment_2_2022 assignment1.launch 

Once the program has run, two screens will pop up in order to see the robot and the environment:

• Rviz (ROS visualization), is a powerful 3D visualization tool for ROS. It allows the user to view the simulated robot model, log sensor information from the robot's sensors, and replay the logged sensor information;

• Gazebo, simulation environment used to create a 3D scenario with robots, obstacles and many other objects.

Furthermore, three more windows will pop up. The user can interact with them in order to set or cancel a target for the robot in the simulation environment (NodeA), to see the number of goals reached and cancelled (NodeB) and to see how far the robot is from the target and at what speed it is moving (NodeC).

In case you want to use the Jupyter Notebook as your main User Interface instead of NodeA you can:

• Remove the line relative to NodeA inside the assignment1.launch file in the launch folder.
• Open a terminal and run the following command to start Jupyter Notebook:

jupyter notebook --allow-root

• Open a web browser and go to the URL displayed in the terminal after starting Jupyter Notebook.
• Navigate to NodeA.jpynb, inside the RT2_JupyterNotebook folder, to open the notebook.
• Run the program within the notebook by executing the cells and use it as your main User Interface instead of NodeA.

Node Graph

Code Documentation

Documentation for the code can be found there: Link to Documentation

Structure of Node A: User Interface

Possible Improvements

• Implement a ros service to print the number of goals reached and the number of goals cancelled.