I am trying to understand L1 Controller but couldn’t find documentation like mentioned in this topic :
Fixed wing position control L1 controller
I know inputs and output of L1 Controller. But I want to learn more.
There is some information about it but it’s another autopilot software so I thought that it should be conveyed in a clearer and more understandable way in PX4 too. And also I wanted to be sure about control algortihm. Like is it L1 Adaptive control or what article/research was it intended for?. I couldn’t find any further information I will be glad if you help.
Thanks Px4 dev team for the note.
* Implementation of L1 position control.
* Acknowledgements and References:
* This implementation has been built for PX4 based on the original
* publication from  and does include a lot of the ideas (not code)
* from .
*  S. Park, J. Deyst, and J. P. How, "A New Nonlinear Guidance Logic for Trajectory Tracking,"
* Proceedings of the AIAA Guidance, Navigation and Control
* Conference, Aug 2004. AIAA-2004-4900.
*  Paul Riseborough, Brandon Jones and Andrew Tridgell, L1 control for APM. Aug 2013.
* - Explicit control over frequency and damping
* - Explicit control over track capture angle
* - Ability to use loiter radius smaller than L1 length
* - Modified to use PD control for circle tracking to enable loiter radius less than L1 length
* - Modified to enable period and damping of guidance loop to be set explicitly
* - Modified to provide explicit control over capture angle