PX4 MPC

Model Predictive Control (MPC) for spacecraft and multirotors running on PX4 Autopilot, integrated with ROS 2.

This package runs MPC controllers as ROS 2 nodes that talk to PX4 through the uXRCE-DDS bridge. The controllers read vehicle states from PX4 and send setpoints back in offboard mode. The optimal control problems are built and solved with the acados framework.

The main vehicle is the ATMOS free-flyer spacecraft. Its controller has several control modes, from body rates and wrench commands down to direct thruster allocation. A quadrotor (x500) example is also included. Setpoints can be set interactively in RViz or come from a predefined setpoint node.

Citation

If you find this package useful in academic work, please cite:

P. Roque, S. Phodapol, E. Krantz, J. Lim, J. Verhagen, F. Jiang, D. Dorner, R. Siegwart, I. Stenius, G. Tibert, H. Mao, J. Tumova, C. Fuglesang and D. V. Dimarogonas, "Towards Open-Source and Modular Space Systems with ATMOS," arXiv preprint arXiv:2501.16973, 2025.

arXiv

BibTeX

@article{roque2025towards,
  title={Towards Open-Source and Modular Space Systems with ATMOS},
  author={Roque, Pedro and Phodapol, Sujet and Krantz, Elias and Lim, Jaeyoung and Verhagen, Joris and Jiang, Frank and Dorner, David and Siegwart, Roland and Stenius, Ivan and Tibert, Gunnar and others},
  journal={arXiv preprint arXiv:2501.16973},
  year={2025}
}

Quick Start

Prerequisites

• ROS 2 (e.g. Humble)
• acados and its Python interface
• PX4 SITL with ROS 2 support, set up by following the PX4 ROS 2 guide (this includes the Micro XRCE-DDS Agent)
• For the spacecraft: the ATMOS simulation, set up by following the ATMOS simulation guide
• (Optional) QGroundControl

Install

mkdir -p ~/ros2_ws/src
cd ~/ros2_ws/src
git clone https://github.com/PX4/px4_msgs.git              # PX4 messages for communication with PX4 DDS
git clone https://github.com/DISCOWER/px4-offboard.git     # RViz interface and setpoint generation
git clone https://github.com/DISCOWER/px4-mpc.git          # this package
cd ..

Install the remaining dependencies (ROS 2 packages, NumPy, SciPy, CasADi, python-control, ...) with rosdep. If you have never used rosdep before, run sudo rosdep init first.

rosdep update
rosdep install --from-paths src --ignore-src -y

Build the workspace:

colcon build --packages-up-to px4_mpc
source install/setup.bash  # use setup.zsh for zsh users

Note: rosdep does not install acados. Install it and its Python interface as described in Prerequisites.

For the propeller control mode, also clone atmos_propeller_plate_interface into ~/ros2_ws/src, rerun the rosdep install command above, and build it:

colcon build --packages-up-to px4_mpc propeller_plate_iface

PX4 Setup

DDS topics: the PX4 topics exposed to ROS 2 are configured in PX4-Autopilot/src/modules/uxrce_dds_client/dds_topics.yaml. Edit this file if you need additional topics.

Arming and mode switching: by default, PX4 expects RC inputs and a QGroundControl (QGC) connection before it allows arming and mode switching. These are the recommended settings for real deployments. Set up either QGC or a headless configuration before running the examples. Both options below describe how to switch to offboard mode and arm the vehicle.

With QGC (recommended)

1. Open QGroundControl.
2. Click the QGroundControl icon in the top left corner and open "Application Settings".
3. Under the "Fly View" tab, scroll down to "Virtual Joysticks" and enable them by clicking the slider to the right of "Enabled".
4. Make sure that auto-center throttle is disabled.
5. Click "Exit Application Settings" in the top left corner to return to the Fly View screen.

To start the MPC, select "Offboard" in the flight mode menu in the top toolbar, then arm the vehicle.

Important: Before arming the vehicle, make sure that the throttle (left vertical joystick) is at the lowest position.

Headless (no QGC)

Warning: Do this at your own risk. We recommend using QGC to keep hardware and software setups consistent.

Disable the RC check and the QGC connection requirement by setting the following parameters in the PX4 SITL terminal:

pxh> param set COM_RC_IN_MODE 1
pxh> param set NAV_DLL_ACT 0
pxh> param set COM_ARM_WO_GPS 1
pxh> param set CBRK_USB_CHK 197848
pxh> param set COM_ARMABLE 1

Then restart the PX4 SITL to apply the changes. After rebooting, you should be able to arm and switch vehicle modes.

To start the MPC, switch to offboard mode and arm the vehicle in the PX4 SITL terminal:

pxh> commander mode offboard
pxh> commander arm

Run the Spacecraft Example

Terminal 1: Start the DDS agent

micro-xrce-dds-agent udp4 --port 8888

Terminal 2: Start PX4 SITL with Gazebo

cd ~/PX4-Autopilot
make px4_sitl_spacecraft gz_atmos

Terminal 3: Start the MPC

ros2 launch px4_mpc mpc_spacecraft_launch.py mode:=wrench rviz_mode:=setpoint

Switch the vehicle to offboard mode and arm it (see PX4 Setup).

The vehicle should now start following the desired setpoints.

KTH Space Lab: to simulate the KTH Space Lab environment, start PX4 SITL with gz_atmos_kthspacelab and enable the matching constraints (recommended):

make px4_sitl_spacecraft gz_atmos_kthspacelab

ros2 launch px4_mpc mpc_spacecraft_launch.py mode:=wrench rviz_mode:=off kthspace_constraints:=true

Spacecraft Control Modes

Set the control mode with mode:=<mode> when launching mpc_spacecraft_launch.py.

Mode	Description	PX4 Offboard Setpoint
wrench (default)	MPC that commands body forces and torques	Thrust and torque
rate	MPC that commands body forces and body rates	Body rate
direct_allocation	MPC that commands individual thrusters	Direct actuator
offset_free_wrench	Offset-free wrench MPC. Requires OpenMPC	Thrust and torque
lqr_wrench	LQR that commands body forces and torques	Thrust and torque
propeller	MPC for the ATMOS propeller plate. Also launches propeller_plate_iface_node from atmos_propeller_plate_interface	Direct actuator

Run the Quadrotor Example

Terminal 1: Start the DDS agent

micro-xrce-dds-agent udp4 --port 8888

Terminal 2: Start PX4 SITL with Gazebo

cd ~/PX4-Autopilot
make px4_sitl gz_x500

Terminal 3: Start the MPC

ros2 launch px4_mpc mpc_quadrotor_launch.py

Switch the vehicle to offboard mode and arm it (see PX4 Setup).

Launch Arguments

mpc_spacecraft_launch.py:

Argument	Default	Description
mode	wrench	Control mode (see Spacecraft Control Modes)
namespace	''	Namespace for all nodes. Must match the PX4 namespace
rviz_mode	setpoint	off: no RViz. viz: RViz for visualization only. setpoint: RViz for visualization and setting the setpoint pose. In off and viz, setpoints come from the test_setpoints node
px4_uses_ned	true	PX4 uses the NED frame (true) or the ENU frame (false)
skip_build	false	Skip the acados solver build and reuse the previously generated solver
kthspace_constraints	false	Use KTH Space Lab constraints. Recommended with gz_atmos_kthspacelab
sitl	false	Also publish vehicle odometry on odom (SITL only)

mpc_quadrotor_launch.py:

Argument	Default	Description
namespace	''	Namespace for all nodes. Must match the PX4 namespace
setpoint_from_rviz	true	Set the setpoint pose interactively in RViz

Namespaces

To run with a namespace, start PX4 SITL with the same namespace as the MPC:

PX4_UXRCE_DDS_NS=pop make px4_sitl_spacecraft gz_atmos

ros2 launch px4_mpc mpc_spacecraft_launch.py mode:=wrench rviz_mode:=off namespace:=pop

References

• ATMOS
• PX4 Autopilot
• PX4 ROS 2 User Guide
• px4_msgs
• px4-offboard
• atmos_propeller_plate_interface
• acados
• ROS 2 Documentation