Assignment1_rt

During this assignment, two nodes were implemented:

• ass1_node1, based on the code written in UI.cpp, which allows the user to interact with two turtles;
• ass1_node2, based on the code written in distance.cpp, which works as a controller of the distance between the two turtles and makes them stop in case of collision with the wall of between themselves.

Requirements

• ROS: Must be installed and properly configured on the system.
• Turtlesim Package: Must be installed in your ROS workspace.

Installation commands

In order to use this package, cloning the repository in your ROS environment is necessary:

git clone https://github.com/mrtelisa/assignment1_rt

In order to compile the nodes, in the workspace the following command must be launched:

catkin_make

Compilation

Firstly, launch ROS:

roscore

Then, open a new terminal window and launch the turtlesim environment:

rosrun turtlesim turtlesim_node

Now our nodes can be launched; the node1, based on UI.cpp, can be launched with:

rosrun assignment1_rt ass1_node1

while the node2, based on distance.cpp, can be launched with:

rosrun assignment1_rt ass1_node2

In order to monitor the distance topic, use:

rosrtopic echo /turtle_distance

Description of the nodes

Node1: UI.cpp

This node follows these steps:

• Spawns a new turtle (turtle2) in the environment;
• Generates in the terminal an interface where the user is required to interact with, selecting:
  • the turtle to control (turtle1 or turtle2);
  • the linear velocities (along x and y axes);
  • the angular velocity;
• Sends the movement requested to the selected turtle for 1 second; then it stops and the user can insert a new command.

Node2: distance.cpp

This node follows these steps:

• Calculates and publishes the value of the distance between the two turtles in a specific topic;
• Checks the distance and stops the moving turtle if:
  • the distance between the two turtles is smaller than a certain threshold, which in this case is set equal to 1.
  • the turtle is assuming a pose too near to the borders; this control is implemented using two fixed values of thresholds, too.

Interaction with the nodes

While the node2 sends a message only if the turtle is too close to the borders or to the other turtle, the first node requires the user to interact with the terminal. The values required are respectively the following ones:

• The turtle to control: turtle1 or turtle2;
• The linear velocity along the x-axis;
• The linear velocity along the y-axis;
• The angular velocity;

After every value inserted as input, pressing enter is required. Also, to close the node it is necessary to press Ctrl+C, followed by "q" and eventually press enter.