| dc.description.abstract | Rising marine activity in the arctic has introduced many ice related challenges for
Dynamically Positioned (DP) marine vessels. Current motion control systems for
DP vessels are not designed to handle ice-related disturbances, and will thus need
to be improved to be able to operate in these challenging conditions.
The main goals of this master thesis have been to evaluate opportunities for handling
large and sudden unknown external disturbances, and compare these with
existing solutions.
There will be presented a predictive feedforward controller to minimize the impact
of an external disturbance. There will also be presented a selective wave filter
with a notch frequency that is adapted by a wave-frequency tracker.
A modified highly responsive PID controller with nonlinear stiffness and damping
terms has been derived, and proven globally asymptotically stable using Lyapunov
based stability analysis. There will also be presented a Disturbance Rejection by
Acceleration Feedforward controller that utilizes acceleration feedback from inertial
measurements.
All of the proposed improvements have been implemented and tested in Matlab/
Simulink, while some of the methods have been implemented and tested hardware-in-
the-loop in a simulator provided by Marine Technologies. The proposed methods
were shown both theoretically and through simulations to yield improved stationkeeping
performances. | |
