karthifairhawn / ROS_Learnings

The learning on robot operating system on Mistral Solution internship. Include turtlesim package clone in python and a face recognition prototype build using ROS2.

Robot Operating System

Build

From root dir - colcon build

To run packages from workspace

1. . install/build.bash

Parameters

1. ros2 param list - List all active parameters

2. ros2 param list /my_node - Particular nodes paramter list

3. ros param get /my_node use_sim_time - Get particular nodes paramter infrmation.`

4. os2 param set turtlesim background_g 100 - Set Parameter Information

5. ros param delete /my_node my_string - To delete a nodes paramter (Conditional)`

`6. ros2 param describe turtlesim background_g - Describe paramter information.

7. ros param dump /my_node - This command will print out all of the parameters on a particular node in a YAML file format. The output of this command can then be used to re-run the node with the same parameters later:

8. ros param load /my_node my_node.yaml - This command will load the values of the parameters from a YAML file into a particular node. That is, this command can reload values at runtime that were dumped out by ros2 param dump:

Topic

1. ros2 topic list - List all topics

2. ros2 topic type /turtle1/cmd_vel - Types on a particular topic.

3. ros2 topic pub /turtle1/cmd_vel geometry_msgs/msg/Twist "linear: x: 2.0 y: 0.0 z: 0.0 angular: x: 0.0 y: 0.0 z: 2.0" - To publish to a topic.

4.ros2 topic echo /turtle1/pose - Echo topic published info

5 ros2 topic hz /turtle1/pose - To get publish rate of particular topic

Service

1. ros2 service call /clear std_srvs/srv/Empty - Calling a service

2. ros2 service list - List all Services

Interfaces

1. ros2 interface show turtlesim/msg/MainBG - To view a msg interface

2. Creating new interace example

• In the tutorial_interfaces/msg directory you just created, make a new file called Num.msg with one line of code declaring its data structure: int64 num

• Back in the tutorial_interfaces/srv directory you just created, make a new file called AddThreeInts.srv with the following request and response structure:

  int64 a
  
  int64 b 
  
  int64 c
  
  ---
  
  int64 sum
  
  

• To convert the interfaces you defined into language-specific code (like C++ and Python) so that they can be used in those languages, add the following lines to CMakeLists.txt:

  find_package(rosidl_default_generators REQUIRED)
  
  rosidl_generate_interfaces(${PROJECT_NAME}
   "msg/Num.msg"
   "srv/AddThreeInts.srv"
  )
  

• Because the interfaces rely on rosidl_default_generators for generating language-specific code, you need to declare a dependency on it. Add the following lines to package.xml

  <build_depend>rosidl_default_generators</build_depend>
  
  <exec_depend>rosidl_default_runtime</exec_depend>
  
  <member_of_group>rosidl_interface_packages</member_of_group>
  

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