Position controller restricting movement to +-5 in x,y, and z axes

[ShameerMasroor]

Hello.

I was experimenting with your drone's position controller as I intend to use it for path following later on.
I passed it a command of

ros2 topic pub /simple_drone/cmd_vel geometry_msgs/msg/Twist 
"{linear: {x: 0.0, y: -8.0,z: 1.0}, angular: {x: 0.0, y: 0.0, z: 2.0}}"

after turning on the position controller using the command:

ros2 topic pub /simple_drone/posctrl std_msgs/Bool '{data: true}'

The position controller restricts the movement of the drone to +-5 in all the axes, and I am honestly unable to find where in the code this restriction is being imposed.

I would be humbled if you could explain the reason behind this, and a possible fix for this.

Thank you.

[ShameerMasroor]

I was able to identify the source of the issue.

Apparantly the PID controller has a limit condition which ceils the maximum input values for velocity to prevent the error from being too large and to prevent the drone from overpitching/overrolling. The implementation of the same PID controller for velocity control for the position controller is problematic, something which I believe the contributors have overlooked in the position controller.

To allow the drone to move to any position, simply comment out the line in the pid_controller.cpp file in the sjtu_drone_description folder

 // if (limit > 0.0 && fabs(new_input) > limit) {new_input = (new_input < 0 ? -1.0 : 1.0) * limit;}