Unit-4
The characteristics of robots generally considered in a selection
process include:
1. Size of class 2. Degrees of freedom 3. Velocity 4. Actuator type 5.
Control mode 6. Repeatability 7. Lift capacity 8. Right-Left-Traverse 9.
Up-down-traverse 10. In-Out-Traverse 11. Yaw 12. Pitch 13. Roll 14.
Weight of the robot
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Not an
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Installing Ubuntu 22.04 on a VM
Step 1 – downloading the Ubuntu . iso file
Download the Ubuntu 22.04 .iso file https://releases.ubuntu.com/noble/. Note that,
just like ROS, Ubuntu distributions also have a name. We usually only use the first
name, so Ubuntu Noble in this case. Click on 64-bit PC (AMD64) desktop image. The
file should be 5 to 6 GB, so make sure you have a good internet connection before
downloading it.
Step 2 – installing VirtualBox
You can start Step 2 while the Ubuntu .iso file is being downloaded. Two popular VM
managers have a free version: VMware Workstation and VirtualBox. Both would work,
but here, I will focus on VirtualBox as it’s slightly easier to use.
Go to the download page of the official VirtualBox website:
https://www.virtualbox.org/wiki/Downloads.
Under VirtualBox Platform Packages, select the current OS you are running. If you
want to install VirtualBox on Windows, for example, choose Windows hosts.
Step 3 – creating a new VM
Once you’ve installed VirtualBox and downloaded the Ubuntu .iso file,
open the VirtualBox software (VirtualBox Manager) and click New. This will
open a pop-up window where you can start to configure the new VM:
Step 4 – starting the VM and finishing the installation
Now that the VM has been configured correctly, we need to start it to install
Ubuntu, using the Ubuntu .iso file that we’ve downloaded and added to the
settings.
To start the VM, double-click on it in VirtualBox Manager, or select it and click on
the Start button.
You will get a boot menu. The first choice is Try or Install Ubuntu and it should
already be selected.
Press Enter.
Wait a few seconds; Ubuntu will start with the installation screen
Setting up the environment for ROS 2
$ source /opt/ros/humble/setup.bash
gedit ~/ .bashrc
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A mobile robot controlled by a camera
robot has 3 ROS packages (from low to high
level):
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Camera package
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Not an
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Motion planning package
Not an
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hardware control package
Not an
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Summary about Node
• A ROS node, according to the ROS wiki, is basically a process that performs
computation.
• It is an executable program running inside your application.
Not an
• You will write many nodes and put them into packages. operating
system
• Nodes are combined into a graph and communicate with each other ! ROS
using
topics, services, actions, etc.
• Note that 2 nodes can’t have the same name.
• If you want to run multiple instances of the same node, you’ll have to add a prefix
or suffix to the name or declare them anonymous.
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What are the main benefits of nodes? Why should
you use nodes instead of just writing all your
code in the same place?
• Reduce code complexity
Notnodes
• Better fault tolerance: If one node crashes, it will not make the other an crash.
operating
• Language agnostic: Can write one node in Python and another node in C++, and
system !
both can communicate without any problem.
$ ros2 run demo_nodes_cpp talker
ros2 run demo_nodes_cpp listener
rqt_graph
