This project has three key elements which are explained below:

1. Dynamic models
2. Controllers
3. Turtlebot sim

For examples which use this project, see Setup and Launch Repo

This package has simple models for running the robot. An example is given in unicycle.cpp

Two important functions that should be modified for creating more complex dynamic models are:

1. Unicycle::updateOdometry(...): This performs Euler integration on the dynamics
2. Unicycle::commandVelocityCallback(...): This stores the commanded inputs to the system

This package contains controllers for controlling the robot. At the current time there are only two joystick controllers. You must install the joy package (for joystick drivers)

kinetic:

sudo apt install ros-kinetic-ros-tutorials

sudo apt install ros-kinetic-joy

melodic:

sudo apt install ros-melodic-ros-tutorials

sudo apt install ros-melodic-joy

See http://wiki.ros.org/joy to setup the joystick drivers correctly.

This package is used for the visualization of the robot. There are currently two nodes:

• simple_map_tf: Produces a mapping from the odom frame to the map frame to allow for plotting of the vehicle in the map frame
• turtlebot_vehicle: Produces the motion of the joint states for the plotting of the turtlebot

For adding additional visualizations, you may want to create another node like turtlebot_vehicle which publishes the correct joint positions and motions.

This package contains a occupancy grid implementation that can be generated off of configuration files at startup, or at run time via laser scan messages. To launch a node that makes and maintains an occupancy grid run the following command:

roslaunch occupancy_grid occupancy_grid.launch

The meaning of each argument in the occupancy_grid.launch launch file is listed below:

• loop_rate: The rate at which this node will publish messages, answer service calls, and respond to incoming messages
• world_file: This is the absolute path to a configuration file that defines what pixels of the occupancy grid will be occupied at startup
• resolution: How far apart each pixel of the occupancy grid will be
• service_topic: The topic that other nodes can use to receive the occupancy grid via a service call
• massage_topic: The topic that this node will publish the occupancy grid on
• tf_frame: The TF frame the grid should live in
• laser_scan_topic: The topic that this node will receive laser scan messages on so it can update the occupancy grid with new obstacles
• laser_scan_queue_length: How many laser scan messages this node will hold between updates
• laser_scan: A boolean flag that tells the launch file whether or not to have the node receive laser scan messages
• start_rviz: A boolean flag that tells the launch file whether or not it should spin-up RVIZ

The meaning of each part of the world configuration files is listed below;

• origin: The x, y, and yaw value of the 0,0 point on the occupancy grid in the global ROS frame
• height: The height of the occupancy grid
• width: The width of the occupancy grid
• line_width: The width of the lines added at startup and at run time
• line(): A incrementally increasing list of lines in the form, [x1, y1, x2, y2]