Application of Deep Reinforcement Learning to Predict Shaft Deformation Considering Hull Deformation of Medium-Sized Oil/Chemical Tanker

Abstract

The enlargement of ships has increased the relative hull deformation owing to draft changes. Moreover, design changes such as an increased propeller diameter and pitch changes have occurred to compensate for the reduction in the engine revolution and consequent ship speed. In terms of propulsion shaft alignment, as the load of the stern tube support bearing increases, an uneven load distribution occurs between the shaft support bearings, leading to stern accidents. To prevent such accidents and to ensure shaft system stability, a shaft system design technique is required in which the shaft deformation resulting from the hull deformation is considered. Based on the measurement data of a medium-sized oil/chemical tanker, this study presents a novel approach to predicting the shaft deformation following stern hull deformation through inverse analysis using deep reinforcement learning, as opposed to traditional prediction techniques. The main bearing reaction force, which was difficult to reflect in previous studies, was predicted with high accuracy by comparing it with the measured value, and reasonable shaft deformation could be derived according to the hull deformation. The deep reinforcement learning technique in this study is expected to be expandable for predicting the dynamic behavior of the shaft of an operating vessel.

A π-Theorem-Based Advanced Scaling Methodology for Similarity Assessment of Marine Shafting Systems

“…Which is in agreement with the results obtained from dimensional analysis found also in literature for cantilever beam, but similarity cannot be ensured at a mixed type of beam including both a cantilever and a simply supported beam, since the similarity parameters in Equations ( 7)-( 9) are not the same as the ones demanded in Equations ( 12)- (14). Therefore, a supplementary phase is required, to couple this theoretical background with the complexity of the application for marine shafting systems.…”

“…In that particular case study of the shafting system of an 82,000 DWT bulk carrier, the initial alignment of the vessel was compared against the performance corresponding to different bearing offset combinations. Similar studies have been recently reported by other researchers especially focusing on the important effect of hull structural deformations in regard to shaft alignment [12][13][14]. These studies collectively tackle various interconnected issues pertinent to marine shafting system operations, with a shared focal point: shaft deflection.…”

A Pi-Theorem-Based Advanced Scaling Methodology for Similarity Assessment of Marine Shafting Systems

“…In that particular case study of the shafting system of an 82000 DWT bulk carrier, the initial alignment of the vessel was compared against the performance corresponding to different bearing offset combinations. Similar studies have been recently reported by other researchers especially focusing in the important effect of hull structural deformations in regard to shaft alignment [12][13][14].…”

Research on the Contact Pressure Calculation Method for the Misaligned Elastomeric Journal Bearing

“…Bearing failure will cause increased shaft vibration, reduced propulsion efficiency, and oil leakage. Reports of bearing failures have shown an increasing trend in recent years with the extending size of ships [1]. For example, three patrol vessels of the Indian Coast Guard experienced bearing wear failures [2], 11 of 17 identical commercial ships were subjected to bearing incidents [3], and DNV GL Classification has noted that they have received increasing reports of aft propeller shaft bearing damage in recent years [4].…”