px4_offboard_control

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px4_offboard_control is a ROS 1 PX4 Offboard trajectory publisher. It generates analytic position, velocity, acceleration, yaw, and yaw-rate references and sends them through MAVROS to the built-in PX4 position controller. It does not contain a ROS-side flight controller.

Analytic trajectory -> mavros_msgs/PositionTarget -> MAVROS -> PX4

Flight demonstrations

Horizontal figure eight	Vertical figure eight

Sinusoidal flip	Fast circle

Features

• Publishes position, velocity, acceleration, yaw, and yaw-rate references at a configurable rate
• Pre-streams Offboard setpoints and can automatically request OFFBOARD mode and arm
• Uses a quintic transition from the current vehicle state to the trajectory start
• Decelerates smoothly and holds position when trajectory tracking is stopped
• Uses a fixed angular speed with smooth online speed changes and continuous trajectory phase
• Publishes a nav_msgs/Path reference preview for visualization
• Provides an RQT reference-trajectory panel with trajectory parameters and start/stop controls
• Publishes PX4-direct setpoints at 250 Hz by default and shows measured setpoint/feedback rates
• Starts RViz with the reference path and MAVROS vehicle pose by default

Available analytic trajectories:

• figure8_horizontal
• figure8_vertical
• helix_flip
• helix_flip_y
• flip_loop_sine
• fast_circle

Requirements

• Ubuntu 20.04
• ROS Noetic
• PX4 Autopilot
• MAVROS
• Eigen3

Install the ROS dependencies:

sudo apt update
sudo apt install ros-noetic-mavros ros-noetic-mavros-extras \
  ros-noetic-rqt-reconfigure ros-noetic-rqt-gui ros-noetic-rviz libeigen3-dev

Build

Place this package in the src directory of a catkin workspace, then run:

cd ~/mavros_ws
catkin build px4_offboard_control
source devel/setup.bash

For a catkin_make workspace:

cd ~/mavros_ws
catkin_make
source devel/setup.bash

Usage

This package does not require a specific PX4 source repository. Start either an upstream PX4 firmware or simulation environment, or the df-main firmware described below.

For example, start upstream PX4 with Gazebo Classic on Ubuntu 20.04:

cd ~/PX4-Autopilot
make px4_sitl gazebo-classic_iris

Alternatively, use the df-main branch of DuctedFanUAV-Autopilot. This branch includes a modified iris and also supports ducted-fan UAV airframes:

git clone --branch df-main --recursive \
  https://github.com/mengchaoheng/DuctedFanUAV-Autopilot.git
cd DuctedFanUAV-Autopilot
make px4_sitl gazebo-classic_iris
# or
make px4_sitl gazebo-classic_ductedfan4

Replace ductedfan4 with another supported ducted-fan UAV airframe when required. On real hardware, run the corresponding flight-controller firmware; PX4 SITL is not required on the companion computer.

Build the package before the first launch and whenever the source code changes:

cd ~/mavros_ws
source /opt/ros/noetic/setup.bash
catkin build px4_offboard_control
source devel/setup.bash

After PX4 starts, open a second terminal and connect MAVROS:

cd ~/mavros_ws
source /opt/ros/noetic/setup.bash
source devel/setup.bash
roslaunch mavros px4.launch fcu_url:="udp://:14540@127.0.0.1:14557"

Open a third terminal and start the trajectory node:

cd ~/mavros_ws
source /opt/ros/noetic/setup.bash
source devel/setup.bash
roslaunch px4_offboard_control px4_direct.launch

This command starts the px4_direct node, the reference-trajectory panel, and RViz. To run without either graphical tool:

roslaunch px4_offboard_control px4_direct.launch visualization:=false trajectory_panel:=false

The package uses the MAVLink SET_POSITION_TARGET_LOCAL_NED interface and does not depend on PX4 ROS 2 message versions. This MAVLink interface is available across multiple PX4 releases, but each selected PX4/MAVROS combination should still be regression-tested in SITL before flight.

The launch file enables automatic trajectory start, OFFBOARD mode requests, and arming by default. Confirm that the flight area, trajectory altitude, and amplitudes are safe. For initial real-flight tests, disabling automatic arming is recommended:

<param name="auto_arm" value="false"/>

Start and stop

Start trajectory tracking:

rosservice call /px4_direct/start "data: true"

Stop smoothly and hold position:

rosservice call /px4_direct/start "data: false"

Main parameters

Parameter	Default	Description
traj_name	figure8_horizontal	Trajectory type
omega_value	0.15	Fixed angular speed in rad/s
omega_transition_duration	2.0	Smooth online speed-transition duration in seconds
setpoint_rate_hz	250.0	PX4-direct setpoint publication rate in Hz
auto_start	true	Start tracking automatically after the vehicle is ready
auto_offboard	true	Request OFFBOARD mode automatically
auto_arm	true	Arm automatically
trajectory_yaw_lock	true	Use a fixed yaw angle
trajectory_yaw_fixed	0.0	Fixed yaw angle in radians
trajectory_start_ramp_duration	5.0	Smooth trajectory ramp duration in seconds
trajectory_switch_transition_duration	3.0	Nominal transition time to the trajectory start

The trajectory geometry defaults match geometric_controller: amplitudes/radii are 3.0 m, center heights are 6.0 m, and the helical translation speed is 0.3 m/s.

Trajectory amplitudes, heights, initial phases, Offboard retry settings, and transition limits are configured in launch/px4_direct.launch.

Change the angular speed during flight; the node transitions smoothly while preserving phase:

rosparam set /px4_direct/omega_value 1.0

The same angular-speed setting, trajectory selection, geometry, yaw settings, and transition parameters are available in the RQT panel. Geometry or trajectory-type changes trigger a smooth switch from the current vehicle state. The panel displays the measured setpoint rate and MAVROS local-position feedback rate. PX4 control loops remain internal and are therefore not reported as a ROS controller rate. The panel contains no ROS-side controller settings.

Increasing setpoint_rate_hz reduces reference update latency but does not increase the PX4 controller gains. More aggressive motion is set with omega_value; more aggressive tracking response requires PX4-side tuning and may use the df-main firmware where appropriate. Confirm MAVLink bandwidth before using high rates on a serial connection.

ROS interfaces

Published topics:

• mavros/setpoint_raw/local (mavros_msgs/PositionTarget): PX4 P/V/A/yaw/yaw-rate setpoint
• reference/trajectory (nav_msgs/Path): reference trajectory preview
• reference/current_pose (geometry_msgs/PoseStamped): current reference pose
• vehicle/current_pose (geometry_msgs/PoseStamped): MAVROS vehicle pose for RViz
• vehicle/path (nav_msgs/Path): actual vehicle trail

Subscribed topics:

• mavros/state
• mavros/local_position/pose
• mavros/local_position/velocity_local

Service:

• /px4_direct/start (std_srvs/SetBool)

Coordinate frame

The node generates local references using the ROS/MAVROS ENU convention and sets PositionTarget::FRAME_LOCAL_NED. MAVROS converts the setpoint from ENU to NED before sending the MAVLink message.