DSA-inspired assessment of autonomous ships stability during turning maneuver

Abstract

Assessing the stability of autonomous ships is challenging due to a lack of crew ensuring situational awareness, experience and good seamanship, which have contributed to safety of navigation to date. Therefore, a comprehensive approach towards evaluation of autonomous ship stability in each phase of operation is required. This problem is raised here with respect to the ship turning maneuver. A Direct Stability Assessment (DSA) inspired approach is applied. Therefore, a series of ship motion simulations are carried out to obtain the dynamic angle of heel for sample operational scenarios and numerous irregular wave realizations to enable identification of a stability failure. An up-to-date 6DoF ship dynamics model is utilized. The simulations account for both the maneuverability and stability characteristics of a vessel. A 56-m long training vessel is used as an example. The simulation results are statistically processed to elicit the maximum instantaneous angle of heel corresponding to a 5% probability of exceedance, to be compared to the assumed threshold. However, the required number of simulations ensuring the required statistical significance of the results remains an open question.