Midterm Study Guide - Githubissues

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Midterm Study Guide #39

Open cmurray3 opened 8 months ago

cmurray3 commented 8 months ago

We will talk about the midterm exam in class on March 14.

In the meantime, here is an outline of what you can expect on the exam:

ROS Overview

What is ROS?
Which version of ROS are we running?
Which version of Ubuntu?
How to start ROS?
- roscore vs roslaunch
Environment Variables
- What are they?
- Which ones do you need?
- Where do we save them?
What is the "Parameter Server"?

Packages

Understand the elements of a ROS package. For example:
- Nodes, msg, srv, CMakeLists.txt, Package.xml, launch, worlds
How to create a new package
```
cd ~/catkin_ws/src
catkin_create_pkg
```
How to compile a package
```
cd ~/catkin_ws
catkin_make
```
When do you need to compile a package?
Which files need to be made "executable"? How do we do that?

Nodes

Nodes are C++ or Python scripts
Where do you save these in a package?
What line needs to go at the top of your .py files? Why?
How to change permissions on .py scripts?
Different nodes communicate via topics, services, and actions.
How to run a single node?
How to run nodes via a launch file?
How can you tell what nodes are active right now?

Topics

.msg structure
What are the available data types?
How to publish in Python script?
How to publish from the command line?
How to subscribe?
How to create custom topics?
- What role does CMakeLists.txt play?
- When do we need to recompile the package?
How can you tell what topics are being published right now?

Services

.srv structure
Difference between Topic and Service?
What are the available data types?
How to define server?
How to call server?
How server issues response
How to create custom services.
- What role does CMakeLists.txt play?
- When do we need to recompile the package?
Call a service from the command line (see Gazebo examples)
How can you tell what services are available right now?

Actions

What are "actions"?
How do these differ from topics/services?
When would these be useful?

Gazebo

What is Gazebo? Are ROS and Gazebo the same?
Which version of Gazebo are we running?
How to launch Gazebo via roslaunch?
What is a .world file
What is a .urdf? .sdf? .xacro?
How to define parameters?
Where to save .launch files? .world files? Model files?
What existing 3D models are available?
Namespaces (multi-robot simulation)

RViz

What is RViz?
How to call via launch file?

Other Libraries/Utilities

tf
rqt
rosgraph

Some nice resources to further your understanding

https://foxglove.dev/blog/the-building-blocks-of-ros1
A 5-part video series describing the early days of ROS and Gazebo: https://www.redhat.com/en/open-source-stories/robots/breaking-the-wheel
- A follow-on blog post from one of the authors of our textbook (featured in the above video series): https://www.redhat.com/en/blog/rise-robot-operating-system

cmurray3 commented 8 months ago

I've added some supplementary materials to help with your exam prep:

Textbook Chapter 2: Preliminaries
- https://wiki.ros.org/ROS/Tutorials/NavigatingTheFilesystem
Textbook Chapter 3: Topics
Textbook Chapter 4: Services
Textbook Chapter 5: Actions