The px4_offboard_lowlevel node of this package consists of controller_node.cpp for the ControllerNode class which handles communication to ROS2 and PX4, and controller.cpp which contains the controller itself, both have corresponding header files in include/px4_offboard_lowlevel. For the implementation of your own controller you will probably only need to make changes to controller_node.cpp.
The ControllerNode class implements the interface between the controller, ROS2 and PX4. It provides the controller with odometry and setpoints, and it requests the controller to calculate desired outputs (attitude or thrust + torque) at a set interval.
The Controller class implements the controller itself.
The desired output is requested by the ControlledNode using the calculateControllerOutput function. It takes a vector for thrust and torque and a quaternion for orientation, these should both be set to the desired values. This may be the only function you need to change to implement your own controller.
calculateControllerOutput(Eigen::VectorXd *controller_torque_thrust, Eigen::Quaterniond *desired_quaternion)UAV Parameters are passed to the controller using the following functions:
setUavMass(double uavMass)
setInertiaMatrix(const Eigen::Vector3d &inertiaMatrix)
setGravity(double gravity)
setKPositionGain(const Eigen::Vector3d &PositionGain)
setKVelocityGain(const Eigen::Vector3d &VelocityGain)
setKAttitudeGain(const Eigen::Vector3d &AttitudeGain)
setKAngularRateGain(Eigen::Vector3d AngularRateGain)Odometry (position, orientation, velocity and angular velocity) is provided to the controller through the setOdometry funciton, this is called by the ControllerNode class every time odometry is received from PX4.
const Eigen::Vector3d &position_W, const Eigen::Quaterniond &orientation_W)Position and orientation setpoints are provided to the controller through the setTrajectoryPoint function.
setTrajectoryPoint(const Eigen::Vector3d &position_W, const Eigen::Quaterniond &orientation_W)Check the parameters that need to be defined for each vehicle in ./config/uav_parameters/x500_param.yaml. By creating another parameters yaml file and another launch file based on ./launch/x500_sitl.launch.py, you should be able to fly another vehicle with the package.