Wenqi has successfully defended his MS thesis. Her work focused on Optimal control strategies for the alignment problem of optical communication systems.

Optical wireless communication (OWC) has a lot of advantages compared to the radio frequency (RF) communication and is currently widely used in many applications. However, the internal or external disturbances impose the OWC link a large misalignment, which may lead to intolerable signal fading. Hence, a very tight alignment is required to reduce the power loss caused by a misalignment between the transmitter and receiver.

This thesis reports three control strategies from different perspectives to solve the alignment problem for different optical wireless communication (OWC) systems.

·      Experimental modeling based strategy: model and analyze the vibration effects on the stationary OWC system. The proposed Bifurcated-Gaussian (B-G) distribution model helps to easily evaluate the link performance of UFSO systems and paves the way for constructing completed auxiliary control subsystems for robust UFSO links.

·      Extremum seeking control-based strategy: propose an extremum seeking control (ESC) based strategy for the mobile OWC system. The proposed approach is simple, effective, and easy to implement.

·      Time scale theory-based strategy: design a time scale based Kalman filter for the intermittent OWC system. The proposed strategy has great potential for solving the problem of observer design in the case of intermittent received signals (non-uniform measurements) and paves the way for further controller design.

The three proposed control strategies directly or indirectly solve the beam alignment problem for optical communication systems, supporting the development of a robust optical communication link.