Zero to ROS

Install terminator with

sudo apt install terminator

In this example we will explore the world of ROS using a simple example. You will build a complete ROS package to calculate the Area and Volume of a Cylinder.

Note:

In the video we did not mention a very important step: when we are sourcing .bashrc, we assume that you have added your development environment to the file, as

source ~/catkin_ws/devel/setup.bash

You can add those lines either by editing the file (with vim or nano for example) or by:

echo "source ~/catkin_ws/devel/setup.bash" >> ~/.bashrc

In this way, every time you source ~./bashrc you make sure that the development environment is sourced correctly.

If you miss this step you won't be able to see your package among the list of available packages

Also: make sure you apply chmod to your file! That is the second most forgotten command in ROS, after sourcing the environment ;-)

The name of the package is different from our ROS-101 repository because you are meant to create the package and write the code by yourself

This video shows how to approach a ROS architecture: you want to find a good balance between modularity and complexity: you decide the best architecture that does the job at the minimum cost.

Python: is a master on none. It does all well, but does not excel in anything. It's extremely user friendly and forgiving, but at the cost of a slower runtime.

For the sake of our course and many application in real life, the advantage of a compiled language like C++ are negligible (in the milliseconds), so unless you are not creating real-time sensitive applications, you are fine with Python. Furthermore, many libraries, like cv2, are wrappers of C-compiled code, and run very fast, even in a Python project

This is the first time we are creating a Custom message. Custom messages are powerful but try and use already available messages because it will

1. save you time and

2. make you compatible with other people's work

In this course we will use

• Standard messages http://wiki.ros.org/std_msgs

• Common messages and in particular, geometry messages: http://wiki.ros.org/common_msgs?distro=noetic#geometry_msgs

• Sensor messages: http://docs.ros.org/en/noetic/api/sensor_msgs/html/index-msg.html

The project is available on our repo at https://github.com/school-of-ros/ROS-101/tree/main/ros_101_tutorial_cylinder

Logging in ROS with Python: http://wiki.ros.org/rospy/Overview/Logging

rqt tools: http://wiki.ros.org/rqt

When we talk about pose, in robotics we mean the 6DOF position and orientation of a system. With this information you can reconstruct the state of your system for monitoring or feedback purposes.

As we will see in further video, you need to read your robot position when you want to navigate to a waypoint.

In this lesson you will be introduced to the basic math and coding necessary to perform autonomous navigation of a 2D robot

If you want to be more conservative with your sensor's reading, You can modify the code and simulate the sonar as the minimum value received rather than the average.