Cooperative Payload Transportation Project (CPT)

Daniel Williams, May - September 2018

Matlab Simulation

Instructions for Usage

1. Ensure that MATLAB R2016 or higher is installed
2. The files can be run from the directory ./MATLAB

Description of Files

• cpt_toplevel.m: top-level file for customizing parameter values, running simulations and plotting output. This is generally the only file you will need to modify. Modifiable parameters include:
  • times: start, end, and transition points
  • cable length and tension (assumed to be mg/2)
  • payload geometry, mass and moment of inertia
  • PID gains for each agent's x-plane and y-plane motion
  • position setpoints
  • maximum velocity
  • initial values for each state variable
• cpt_startupmode.m: holds the system of differential equations describing the startup flight mode of the simulation
• cpt_gatekeeper.m:
• cpt_carrymode.m: holds the system of differential equations describing the carrying flight mode of the simulation
• cpt_dropoffmode.m: holds the system of differential equations describing the drop-off flight mode of the simulation
• cpt\_sat_o.m: limits output in order to remain within user-defined velocity constraints
• cpt\_sat_i.m: a velocity limiter that uses a built-in interpolator with the user-defined position setpoints

Outstanding Bugs

• Offset from zero degrees for θ1 and θ2 during dropoff mode (23 September 2018)
• ϕ is not giving sound output, issue not solved by using ode15s instead of ode45 (23 September 2018)

Changelog

• 23 September 2018: renamed files, first commit to the new remote

ROS-Gazebo-MAVROS-SITL Simulation

Instructions for Usage

1. Ensure you have followed the instructions for installing prerequisites for the software-in-the-loop joystick flight package (see here)
2. Copy the folder cpt_sitl_pkg to ~/catkin_ws/src/, then build and source the catkin workspace
3. Open a terminal shell and do the following:

    roscd cpt_sitl_pkg
    cd ./build
    cmake ../
    make

For a demonstration of the angle-measuring plugin, an example world with a pendulum is included in /worlds/pendulum.world.

1. In a terminal shell run the following:

    roscore

2. Open a new terminal shell and run the following:

    roscd cpt_sitl_pkg
    gazebo ./worlds/pendulum.world --verbose

3. To see the pendulum in action, right click the model and set it to Wireframe
4. In Gazebo, bring up the Topic Visualization panel with Ctrl+T and double-click on /Pendulum/joint_angle to see the published angle messages.
5. Open a new terminal shell and run rostopic echo /Pendulum/joint_angle to observe the published angle messages in ROS

A demonstration of the customized model and world for the cooperative payload transportation project is also available. Simply run roslaunch cpt_sitl_pkg multiuav_demo.launch.

Description of Files

• /build: directory for building the angle-measuring plugin
• /launch: contains launch files for the angle-measuring plugin demonstration and the CPT flight demonstration
• /models: contains the modified 3DR Iris model, with two UAVs, a cylindrical payload and cables
• /scripts: contains a Python script that sends position setpoints for each agent to MAVROS for onboard execution
• /worlds: contains the example world for the angle-measuring plugin demonstration
• /joint_angle_plugin.cc: C++ source code for angle-measuring plugin
• /CMakeLists.txt: required for CMake
• /package.xml: required for ROS

Outstanding Bugs

• Custom launch file for pendulum demonstration does not launch the plugin (25 September 2018)
• Gazebo requires high GPU capacity to run smoothly, therefore low real-time factor and unsound IMU readings for the leader agent UAV0 (25 September 2018)

Changelog

• 25 September 2018: merged angle-measuring plugin files into the cpt_sitl_pkg ROS package, first commit to the new remote