The novel method accounts for the dynamic conditions in a
real sea that affect the manoeuvring performance of autonomous
ships
BUSAN, South Korea,
March 14, 2024 /PRNewswire/ -- The
study of ship manoeuvring at sea has long been the central focus of
the shipping industry. With the rapid advancements in remote
control, communication technologies and artificial intelligence,
the concept of Maritime Autonomous Surface Ships (MASS) has emerged
as a promising solution for autonomous marine navigation. This
shift highlights the growing need for optimal control models for
autonomous ship manoeuvring.
Designing a control system for time-efficient ship manoeuvring
is one of the most difficult challenges in autonomous ship control.
While many studies have investigated this problem and proposed
various control methods, including Model Predictive Control (MPC),
most have focused on control in calm waters, which do not represent
real operating conditions. At sea, ships are continuously affected
by different external loads, with loads from sea waves being the
most significant factor affecting manoeuvring performance.
To address this gap, a team of researchers, led by Assistant
Professor Daejeong Kim from the
Division of Navigation Convergence Studies at the Korea Maritime
& Ocean University in South
Korea, designed a novel time-optimal control method for
MASS. "Our control model accounts for various forces that act on
the ship, enabling MASS to better navigate and track targets in
dynamic sea conditions," says Dr. Kim. Their study was made
available online on January 05, 2024,
and published in Volume 293 of the journal Ocean Engineering on
February 01, 2024.
At the heart of this innovative control system is a
comprehensive mathematical ship model that accounts for various
forces in the sea, including wave loads, acting on key parts of a
ship such as the hull, propellers, and rudders. However, this model
cannot be directly used to optimise the manoeuvring time. For this,
the researchers developed a novel time optimisation model that
transforms the mathematical model from a temporal formulation to a
spatial one. This successfully optimises the manoeuvring time.
These two models were integrated into a nonlinear MPC controller
to achieve time-optimal control. They tested this controller by
simulating a real ship model navigating in the sea with different
wave loads. Additionally, for effective course planning and
tracking researchers proposed three control strategies: Strategy A
excluded wave loads during both the planning and tracking stages,
serving as a reference; Strategy B included wave loads only in the
planning stage, and Strategy C included wave loads in both stages,
measuring their influence on both propulsion and steering.
Experiments revealed that wave loads increased the expected
manoeuvring time on both strategies B and C. Comparing the two
strategies, the researchers found strategy B to be simpler with
lower performance than strategy C, with the latter being more
reliable. However, strategy C places an additional burden on the
controller by including wave load prediction in the planning
stage.
"Our method enhances the efficiency and safety of autonomous
vessel operations and potentially reduces shipping costs and carbon
emissions, benefiting various sectors of the economy," remarks
Dr. Kim, highlighting the potential of this study. "Overall, our
study addresses a critical gap in autonomous ship manoeuvring which
could contribute to the development of a more technologically
advanced maritime industry."
Reference
Title of original paper: Time-optimal control of ship
manoeuvring under wave loads
Journal: Ocean Engineering
DOI: https://doi.org/10.1016/j.oceaneng.2023.116627
About National Korea Maritime & Ocean University
visit: http://www.kmou.ac.kr/english/main.do
Contact:
Hong Jun Cho
+82 51 410 5147
374458@email4pr.com
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SOURCE National Korea Maritime & Ocean University