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Task 2: Simulate torpedo to follow a submarine

Your Objective:

To develop a controller node that subscribes headings and distance data from hydrophones, process it using PID Controller algorithm and publish rudder angle and propeller velocity to surge towards the submarine and finally, send a detonate request signal to the warhead while approaching the submarine.

About this Task:

This task aims to test your knowledge in ROS and basic robotics concepts such as:

  • ROS Publisher & Subscriber
  • ROS Service & Client
  • PID Controller

How should you proceed:

  1. Write codes to subscribe from /torpedo/hydrophones/headings & /torpedo/hydrophones/distance topics and publish on /torpedo/rudder/angle & /torpedo/propeller/velocity topics. ROS Publisher Subscriber Tutorial

  2. Use the following rostopic commands to get details of the topic and debug your code.

  • rostopic list: list all available ros topics.

  • rostopic info /topic_name: get msg datatype, current Publishers & Subscribers.

  • rostopic pub /topic_name: publish data to a topic.

  • rostopic echo /topic_name: subscribe data from a topic.

  • rosservice list: list all available services

  • rosservice call /service_name: call a service with required parameters

  • Use Tab key to autocomplete commands and also suggest possible commands/arguements.

  1. Write a PID Controller that takes headings as error input and generates rudder angle as output, thus aligning the torpedo towards the submarine. A constant value can be published to the propeller velocity, allowing the torpedo to surge forward.

  2. When the torpedo is less than 2 meters from the submarine, send a request detonation signal to the service /torpedo/warhead/detonate. ROS Service Client Tutorial

How to run:

  1. Firstly, navigate to tiburon_ws from the terminal cd ~/tiburon_ws and then create a new C++ node with the gedit controller.cpp command.

  2. Add the following lines at the end of CMakeLists.txt in the torpedo package and build the package with catkin build torpedo

add_executable(controller src/controller.cpp)
target_link_libraries(controller ${catkin_LIBRARIES})
  1. To launch warzone world along with torpedo, run the following commands in separate terminals (use CTRL+SHIFT+T in terminal to create a new tab inside the terminal)
  • roslaunch warzone arena.launch
  • roslaunch torpedo spawn.launch
  • rosrun torpedo controller