Optical wireless communication (OWC) offers many benefits over established radio
frequency–based communication links. Particularly in, high-data services, high security,
and license-free operation, OWC link are becoming an attractive solution for the next
generation of communication systems. In OWC, precise alignment of the incoming
beam is necessary to close the communication link. However, precisely aligning the
beam between the transceivers is challenging due to the laser beam’s narrowness
and external disturbances that can significantly reduce, destroy, or scatter the beam
signal. Therefore, designing optimized control strategies can significantly improve
the alignment precision, which is the main motivation for this work. This thesis
deploys standard and optimal control techniques, with an emphasis on optimized
control strategies, to address the alignment problem in underwater optical wireless
communication (UOWC) and in laser beam stabilizer systems within a vibrating
environment.
First, the UOWC system’s alignment problem was investigated in a vibrating
scenario. For its effective control, the properties of light propagation were considered
by accounting for the dynamical model that describes the propagation characteristics
of the signal beam between transceivers. To control the UOWC system, we designed
an observer-based optimal controller approach that combined the unconstrained
and constrained optimal controllers, namely linear quadratic regulator (LQR) and
model predictive control (MPC) with the extended Kalman filter (EKF). The latter
enabled estimations of the beam dynamics from the power of the received beam signal.
Extensive simulation tests were conducted that demonstrated the efficiency of the
MPC algorithm compared to the LQR, fractional order proportional integral derivative
(FOPID) and conventional PID controllers in terms of tracking and robustness against
the disturbance levels.
Second, the alignment problem in the laser beam stabilizer system was considered,
whereby the designed control algorithms were tested experimentally in a vibrating
disturbance. For this particular system, the LQR and MPC optimal controllers were
designed both in simulation and experimental environments. The designed optimal
control algorithms were compared to a conventional PID controller and its optimized
variants (e.g., fractional and robust), demonstrating the MPC design’s outperformance
in terms of tracking error and robustness to different voltage disturbance levels.
| Identifer | oai:union.ndltd.org:kaust.edu.sa/oai:repository.kaust.edu.sa:10754/675957 |
| Date | 03 1900 |
| Creators | Al-Alwan, Asem Ibrahim Alwan |
| Contributors | Laleg-Kirati, Taous-Meriem, Computer, Electrical and Mathematical Science and Engineering (CEMSE) Division, Alouini, Mohamed-Slim, Feron, Eric, Jones, Burton, Djemai, Mohamed |
| Source Sets | King Abdullah University of Science and Technology |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Rights | 2023-03-26, At the time of archiving, the student author of this dissertation opted to temporarily restrict access to it. The full text of this dissertation will become available to the public after the expiration of the embargo on 2023-03-26. |
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