The application of signal processing techniques for real-time monitoring of the dynamic stability of a ship via its motion responses
Enshaei, H and Birmingham, R, The application of signal processing techniques for real-time monitoring of the dynamic stability of a ship via its motion responses, Journal of engineering for the maritime environment, 227, (2) pp. 114-124. ISSN 1475-0902 (2013) [Refereed Article]
Significant changes of stability at sea can lead to dangerous situations and eventually stability failure. Despite its importance,
the current intact stability criteria do not evaluate the motion responses of a vessel. More recently, the
International Maritime Organization has identified phenomena in seaways responsible for stability failures. These phenomena
can cause large roll angles and/or accelerations that can endanger ships due to critical stability situations in waves.
The measurement of waves while a ship is underway is a major challenge, but ship motion is a good reflection of the wave
characteristics and can be captured. Signal processing techniques are used in the detection and estimation of the influential
parameters of a wave through the analysis of motion responses. Some variables of the system can be detected by spectral
analysis of heave and pitch responses. These variables are the peak wave frequencies and associated magnitudes which
can cause a high roll motion when similar to the roll natural frequency. The instantaneous frequency present in the signal
is revealed through spectral analysis of short-time Fourier transforms in less than a minute. The instantaneous frequency
is a parameter of practical importance which can be used in decision-making processes to avoid high roll motions.