Blog: ROS | The Construct

ROS STATISTICS: ROS tutorials

Video tutorial learning is one of the ways to learn ROS effectively (more ROS learning methods). It provides an unique presentation which show how programs are created and ran, in a practical way. It allows you to learn how to carry a ROS project from the professional or instructor, which alleviate a beginner’s fear to start learning ROS to a certain degree.

You can find over one million tutorials on youtube when you search ros tutorials. Over 500,000 new ROS tutorials were uploaded last year alone.

We have compiled some of the best-ranked ROS tutorials for you:

[ROS Q&A] 084 – Found the following, but they’re either not files or not exe

In this video we show how to solve the error “Found the following, but they’re either not files or not executable” that happens sometimes when you call “rosrun” to run a ROS Node. This error was reported in the following question:
https://answers.ros.org/question/258154/visualize_velocity_profilepy-not-working-in-teb_local_planner/

Q: When the user tries to run his file called visualize_velocity_profile.py this error happens.

A: This happened because the file doesn’t have execute permissions. To give “execute permissions” in this case the user could just run “chmod +x visualize_velocity_profile.py“.solve it.

[ROS Q&A] 083 – Have a 3-finger gripper simulated in Gazebo

Q: 3 finger gripper model for moveit/gazebo?
Original Question: https://answers.ros.org/question/277795/3-finger-gripper-model-for-moveitgazebo/

A: In the following video I show how you can easily have a 3 finger gripper simulated in Gazebo.

[ROS Q&A] 082 – Add AR tag in gazebo #Part2

This is the second part of this Ar tracking series where you will learn how to do AR tracking with only an RGB camera. This is the previous video of this series: https://youtu.be/WDhIaVOUwsk. The question related to is : https://answers.ros.org/question/240392/add-ar-tag-in-gazebo/

Q: Ar track with only RGB camera
A: Launch the ar tracking no kinect package script with the camera topic of your robot and the error values of around 20 %.

[ROS Q&A] 081 – Making Aibo robot walk with ROS – #Part 1

In this series of videos we are going to show how to use the Aibo robot with ROS. How to program the robot using a Gazebo simulation of Aibo and how to transfer to the real robot. Both, simulation and real robot will be controlled using ROS.

In this first video, we are showing the simulation we are using, and how to send commands to the joints to make Aibo adopt a pose.

[ROS Q&A] 080 – How to make custom ROS Action

About

In this tutorial, we will learn how to create and compile a custom ROS Action from zero by answering a real question from ROS.Answers.

Below are the Steps to create the project as shown in the video

Step 1

Head to ROS Development Studio and create a new project.
Provide a suitable project name and some useful description. (We have named the project how_to_make_custom_ros_action)
Load/Start the project (this will take a few seconds).
Let’s create a new catkin package in our catkin workspace. Open Tools > Shell and run the following commands

$ cd catkin_ws/src
$ catkin_create_pkg turtlebot3_console_controller actionlib_msgs std_msgs

We’ll create an action directory to put the action file. We will create an action file named Motor.action inside the action directory

$ cd turtlebot3_console_controller
$ mkdir action
$ touch Motor.action

Use Tools > IDE to browse the directory and file we just created. At this point we should have the following directory structure

.
├── ai_ws
├── catkin_ws
│   ├── build
│   ├── devel
│   └── src
│       ├── CMakeLists.txt
│       └── turtlebot3_console_controller
│           ├── action
│           │   └── Motor.action
│           ├── CMakeLists.txt
│           └── package.xml
├── how_to_make_custom_ros_action.zip
├── notebook_ws
│   ├── default.ipynb
│   └── images
└── simulation_ws
  ├── build
  ├── devel
  └── src

Step 2

Open the Motor.action file in IDE and write the following content to it.

# This is an action definition file, which has three parts: the goal
# the result, and the feedback.
# Part 1: the goal.
#
# The angle in degree the robot to turn, sent by client main
float64 angle
---
# Part 2: the result, sent by action server unpon completion
#
# How much time used
duration time_elapsed
# How many updates thrown in total
uint32 updates_n
---
# Part 3: the feedback,to be sent periodically by server
#
# The amount of time elapsed from the start
duration time_elapsed

The contents of Motor.action defines variables of three categories. The categories are separated by — lines. The first category of variables are related to GOAL, second is related to RESULT and third are related to the FEEDBACK. Here we have the following variable in different categories: angle for GOAL, time_elapsed, updates_n for RESULT and time_elapsed for FEEDBACK.

Now we have to add the directive to compile action file in CMakeLists.txt file. This file is inside our package directory i.e. ~/catkin_ws/src/turtlebot3_console_controller. Open the CMakeLists.txt file in IDE
Add the following code block
```
add_action_files(
FILES
Motor.action
)
```

Also, add this code block

generate_messages(
DEPENDENCIES
actionlib_msgs
)

Let’s compile the project. Run following commands in the SHELL

$ cd ~/catkin_ws

$ catkin_make
To test if the action file works we will create a script name node.py inside a new directory within the package. Use the following commands in SHELL

$ cd ~/catkin_ws/src/turtlebot3_console_controller

$ mkdir src

$ touch node.py
To create the directory and file we can use IDE tool as well. Let’s add the following code to the node.py file

from turtlebot3_console_controller.msg import MotorGoal, MotorResult, MotorFeedback 

print("OK, it worked!!!")

Let’s run the above script. Enter the following commands in the SHELL

$ cd ~/catkin_ws/src/turtlebot3_console_controller/src

$ ./node.py

After running the above command you should see the reply OK, it worked!!! in the next line.

And that’s it. We have created a basic action message and verified it works.

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