hsg7280 / lunar_rover

Project: Gazebo Integration using API

Overview

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Concepts Used

Following are the concepts used for this project:

• ROSlaunch API
  • To import the image using path
  • To import the image using camera
  • To set thresholds for Canny edge detection
• ROS tf
  • To set the values of threshold parameters
  • To fetch the values of threshold parameters

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Directory Structure

• Following is the directory structure of the package

  .
  ├── CMakeLists.txt
  ├── docs                             # README dependencies
  │   ├── tf.png
  │   └── tree.txt
  ├── include
  │   └── TurtleSim-tf
  ├── launch                           # Launch files
  │   ├── dynamic.launch                 # Launch - Multiple instance of same node using launch file
  │   └── spawn.launch                   # Launch - Multiple turtles in a turtlesim using launch file
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  ├── nodes                            # ROS Nodes
  │   ├── add_frame.py                   # Blueprint of a node - spawn random turtles and broadcast transform
  │   ├── pylaunch.py                    # Launch multiple instances using ROSlaunch API
  │   └── Turtle.py                      # Turtle class to control turtle activities
  ├── package.xml
  ├── README.md
  └── src

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Coding Style Guide - PEP8

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Dependencies

• ROS-tf2 package
• turtlesim package

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Setup and Run

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

• Download the packages - turtlesim-tf

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

• Build the work-space

  • $ cd ~/ROS_ws/
  • $ catkin_make

Using XML

File associated - dynamic.launch and blueprint_node_launch.py

Using Python Script

File associated - pylauncher.py and blueprint_node.py

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

• Run the command - $ roslaunch turtlesim-tf xxxxxx.launch 5

  • where 5 = number of turtle in a turtlesim

    You can configure this number

• In a new terminal, run the command - $ rqt_tf_tree to display the tf-tree

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• This is an architecture for Gazebo
• There are two main nodes - server and a client
• Server handles all the physics, sensors and calculation part
• Client's job is to render all this data in the simulator
• Gazebo's server and client keeps communicating continuously
• After reading the data from this communication channel, we can read sensor data, simulation data and the physics data
• This data once augmented with ROS arguments can be sent over ROS topics to be accessed by the ROS nodes

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Article

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