ROS Pylauncher

Overview

Lauch Files are a great way to launch multiple ROS nodes. In this project, different ways of launching multiple instances of a node in ROS is shown. Different methods of launching the nodes such as using xml files and python script are demonstrated in this project.

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Concepts Used

Following are the concepts used for this project:

• Manually launching multiple instances of same node using launch files
  • To run multiple instances of same node
• Dynamically launching multiple instances of same node using launch files
  • To recursively start same node with different node names
• Dynamically launching multiple instances of same node using Python scripts and ROSlaunch API
  • To launch nodes in sequence with custom node name, topic name, and broadcasting tf data

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Directory Structure

• Following is the directory structure of the package

  .
  ├── CMakeLists.txt
  ├── docs                                         Supporting files for README
  │   ├── manual.png
  │   ├── ROSAPI.png
  │   ├── rosgraph.png
  │   ├── ros.png
  │   └── topics_info.png
  ├── include
  │   └── pylauncher
  ├── launch                                       Launch Files
  │   ├── dynamic.launch                               Dynamically launch multiple instances of a node 
  │   └── manual.launch                                Manually launch multiple instances of a node
  ├── nodes                                        ROS Nodes
  │   ├── blueprint_node_launch.py                     Template Node to be launched using xml launch files
  │   └── ROSAPI
  │       ├── blueprint_node.py                        Template Node to be lanched using python launch script
  │       ├── pylaunch.py                              Script to launch ROS Nodes
  │       └── turtle.py                                Script containing class for turtles in turtlesim 
  ├── package.xml
  ├── README.md
  └── src

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Coding Style Guide - PEP8

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Setup and Run

To run the project on your local system, follow the procedure:

• Download the packages - pylauncher

• Copy these packages to your ROS workspace i.e. ~/ROS_ws/src/

• Build the work-space

  • $ cd ~/ROS_ws/
  • $ catkin_make

• Open new terminal and source the ROS workspace - source ~/ROS_ws/devel/setup.bash

Using XML

• Files associated - manual.launch, dynamic.launch and blueprint_node_launch.py

• To run the manual launch file, run the following command

  $ roslaunch pylauncher manual.launch

• To run the dynamic launch file, run the following command

  $ roslaunh pylauncher dynamic.launch num:=5

Using Python Script

• File associated - pylauncher.py and blueprint_node.py

• Navigate to ROSAPI directory using following command

  $ cd ~/ROS_ws/src/pylauncher/nodes/ROSAPI/

• Run the python script to launch nodes using python script

  $ python3 pylaunch.py 5

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