91'5x122 cm Poster Template

1
MODELLING AND CONTROL OF HIGH SPEED CRAFT J.
Liu, R. Allen, H. Yi
Results
Introduction
1. Wave disturbance prediction
Motion control systems have a significant
impact on the performance of ships and marine
structures allowing them to perform tasks in
severe sea states and during long periods of
time. However, stabilization control of
high-speed craft is a very difficult problem
owing to the complicated nature of hydrodynamic
forces that act on these crafts. The performance
of traditional closed-loop stabilization methods
is usually poor in high sea-states. To improve
this situation, a new stabilization control
strategy has been proposed.
Figure 2. Prediction results by using Kalman
filter
Figure 3. Prediction by using ARMA model
2. Roll motion control results
Methods
This method introduced a feedforward
controller to compensate for the wave
disturbances. The method differs from the
traditional approaches in that feedforward
compensation is not based on measurements of
approaching waves (since these cannot
realistically be made with current technology),
but on the prediction of natural wave-induced
motion. The feedforward loop is embedded into a
model predictive control (MPC) framework which
can include the predictive disturbance in a
natural way.
Figure 4. Control results comparison
1. Scheme diagram
Conclusion and Future work
the prediction and the simulation results
show that better disturbance predictive
performance can lead to better control
performance. From this point, an adaptive MPC
framework is used which means that it can adapt
to changes in ship dynamics due to changes in
sea-states and wave angles. In the future,
other predictive methods, such as ARX, can also
be involved in this adaptive MPC framework to
deal with the model uncertainties. These
methods will be tested on a free-running ship
model built in China.
Figure 1. Control scheme
2. ARMA model in MPC framework
Control induced motion model (State-space)
Acknowledgements
Wave induced motion model (ARMA)
Minimize the cost function
The Author thanks China Scholarship Council
for the sponsoring his study in Institute of
Sound and Vibration and also thanks D. J. Taunton
in Ship Science department of University of
Southampton for the help of numerical modelling