An Introduction to ROS, the Robot Operating System: Controlling hardware (4/6)

Sid Faber
Canonical

The Robot Operating System (ROS) is a flexible, open source framework for writing robot software. ROS has been widely used in robotics research for over a decade, and many commercial products now rely on ROS.

We’ll cover the following topics:

The ROS architecture and how to get started
Basic ROS constructs: Nodes, topics, services and actions
Installing ROS on a Raspberry Pi running Ubuntu
Controlling hardware
Remote control of your robot
Adding sensors
Where to go from here
At the conclusion of this tutorial you’ll be prepared to build your own ROS-based robot!

[srikanth]

18:27 sending the command from the laptop to the raspberry pi.. is there a networking setting we need to make before this happens successfully? I came this far following your video but could not establish the communication between my Ubuntu machine and raspberry pi on the robot. Running ROS 2 Eloquent on both the RPi and the Ubuntu machine. The nodes dont find each other. Can you please point me in the right direction?

[messerschmidtfpv]

great video series. i use a L298n motorshield. all i have to do is change the gpio connections and add the ena / enb connections, if i understand that correctly, the program can then be adopted. Good work.

[ChampikaNirosh]

I've reached the fourth video in my attempt to grasp the concept of ROS (Robot Operating System), and I'm still struggling to comprehend its essence. Up until now, the content has primarily covered activities achievable without ROS, leaving me without a clear understanding of what ROS is. Could you please consider revisiting the video content, placing a stronger emphasis on explicating ROS and its functionalities?

[Zalameh-byke]

Thanks for sharing the video! Question: what is the benefit of having the ROS middleware in this case you have? I fail to see the purpose since everything could have been achieved without ROS

[sidaliu]

This demo project is very interesting and easy to follow, thanks! And I have a question: you mentioned in the previous video, the General Purpose IO (GPIO) is one level lower than ROS, but here we directly access GPIO, why do we do that? I thought we should only deal with ROS. Thanks again.

[SergioGugliandolo]

Hello, Nice project! I'm grateful for the knowledge you share with us!

I've done nearly everything you did in the last video (3/6), then shut down the Raspberry and turned the power down. After a day I connected again power to the Raspberry. Problems begin: it is not connecting to the wifi.

I've read that it may be that it does not connect until login. I don't think this is the case, because the last time I rebooted it a lot of times, and it still connected to wifi (or I would not have the opportunity to login because I'm only using ssh, as you recommended). If it is the problem what should I do (if needed I can access to keyboard, mouse, and monitor).

Another option I thought was that when I turned the system off, I did not wait enough time to unplug the cable (i waited about 20 seconds after the green led, which should indicate sd writing activity, stopped blinking).

Can you help me, please? Thank you.

EDIT

After a lot of time, it connected. I don't know why, I haven't done anything, just leaving it on while I was studiyng and founding it connected after about one our.

I will leave this comment to help someone haveing same issue. (If you prefer I can remove it)

Thank you again for the videos, really interesting and useful!!

[leewenger]

sudo apt install rpi.gpio doesn't exist and fails. when trying to run the examples they fail as gpio is protected and must be run as sudo... while some people have claimed that you can create a gpio group and such to make it so you don't need sudo access to run code that accesses the gpio pins, the steps to do this have not worked (for me). It would be nice if this was addressed in the video or at least in the video notes... have to admit its pretty frustrating to try to follow something step by step and have to do your own debug at literally every step... I'm interested in applying ros and not becoming an ubuntu ninja master.

[yesmani]

hi Sid, the way you explain this project is really very easy to understand. i have one issue with the communication, sending command from laptop to raspberry pi. When i run the command "ros2 topic pub '/move' 'std_msgs/String' '(data: forward)'", i am getting this error message in my laptop terminal "Failed to populate field: 'String' object has no attribute '(data' " .how to fix this issue

[kostik]

A great video, thank you. But because of your pointer it's impossible to watch with my cat nearby.

[ypm]

Hi can someone help me ? I installed everything just like in the video and as long as I'm in the robot everything works but from computer to robot doesn't. I run ros-helloworld.py in robot and do the ros2 topic pub command in PC .Is like the listener doesn't see the forward messages ??? What could I be doing wrong ??
Also I'm doing source the commands

[locyfish]

when I try to run the py code, a couple things. I have to sudo before python, and it keeps telling me no module named rclpy. Any thoughts?

[ypm]

hi, can you please share the code ????

[adviksharma]

BAD













































B

















A






















D

[mbunds]

OK then, so building the robot was the EASY part.