Fouling organisms reduce a ship’s fuel efficiency and disturb the ecosystem. Therefore, the International Maritime Organization (IMO) and many nations have enacted laws that mandate periodic hull cleaning for removing fouling organisms. However, cleaning niche areas of the ship hull is extremely difficult. Due to their complex shape, applying antifouling paint and cleaning with hull cleaning robots is difficult, but about 80% of fouling organisms are concentrated in the niche areas. To resolve this issue, this research proposes the use of an autonomous cleaning robot with a hydraulic polyarticular robot arm to clean niche areas of the ship hull. This robot can approach niche areas of the ship hull with complex shapes using its polyarticular arm. It was designed to be able to scan the cleaning area, establish a cleaning plan, and clean accordingly. This robot autonomously cleaned a propeller blade, which is a typical niche area of the ship hull, to verify the applicability of this system. The experiment results show that approximately 80% of the biofouling was removed from the hull crevices and 81% of the cleaned biofouling was recovered.

There is a large risk of damage, triggered by harsh ocean environments, associated with offshore structures, so structural health monitoring plays an important role in preventing the occurrence of critical and global structural failure from such damage. However, obstacles, such as applicability in the field and increasing calculation costs with increasing structural complexity, remain for real-time structure monitoring offshore. Therefore, this study proposes the comparison of cosine similarity with sensor data to overcome such challenges. As the comparison target, this method uses the rate of changes of natural frequencies before and after the occurrence of various damage scenarios, including not only single but multiple damages, which are organized by the experiment technique design. The comparison method alerts to the occurrence of damage using a normalized warning index, which enables workers to manage the risk of damage. By comparison, moreover, the case most similar with the current status is directly figured out without any additional analysis between monitoring and damage identification, which renders the damage identification process simpler. Plus, the averaged rate of errors in detection is suggested to evaluate the damage level more precisely, if needed. Therefore, this method contributes to the application of real-time structural health monitoring for offshore structures by providing an approach to improve the usability of the proposed technique.

The deep-seabed mining system for mining resources consists of a mining vessel, lifting riser, lifting pump, buffer system, flexible riser, and mining robot. Because this system is exposed to extreme environments such as fluid resistance, high water pressure, and deep water, a considerable amount of time and cost is consumed in the design and test evaluation of equipment. To tackle these problems, the deep-seabed mining system in an extreme environment requires simulation-based technology. In particular, due to the large movement caused by marine energy, vibration caused by the operation of the mechanical system, and driving resistance of mining robot by the subsea soft soil, it is very important in the mining system design to analyze the dynamic effects of the various elements that constitute the deep-seabed mining system in a single integrated environment. This paper introduces the development of an integrated dynamic simulation method for deep-seabed mining systems and discusses the results.

In this study, the basic configuration and operation concept of a CO₂ terminal were identified by conducting a system engineering process. The performance goal of a CO₂ terminal was determined by requirement analysis. Then, functions and timelines were derived by functional analysis to meet the performance goal. Equipment to perform the functions were defined and finally, a process flow block diagram of the CO₂ terminal was acquired. The CO₂ terminal in this study consisted of three parts. First, the CO₂ loading/unloading part is responsible for liquid CO₂ unloading from the carrier and loading vapor CO₂ onto the carrier. Secondly, the liquid CO₂ transmission part extracts liquid CO₂ from the storage tanks and increases the pressure until it satisfies the offshore pipeline transportation condition. The vapor-treatment part collects boil-off gas, generates vapor CO₂, and charges the storage tanks with vapor CO₂ to control the pressure of the storage tanks that discharge liquid CO₂. Finally, the study results were compared with a liquefied natural gas (LNG) terminal. The biggest difference between the CO₂ terminal in this study and the LNG terminal is that a vaporizer is essential in the CO₂ terminal due to the smaller storage capacity of the CO₂ terminal and, therefore, the lower amount of boil-off gas.

Regular inspections and hull cleanings are essential to prevent bio-fouling on ships. However, traditional cleaning methods such as brush cleaning and high-pressure water-jet cleaning at docks are ineffective in cleaning niche areas like bow thrusters and sea chests. Consequently, cleaning robots based on brushes and water jets have been developed to effectively remove bio-fouling. However, there are concerns that brushes may damage hull coatings, allowing bio-fouling to penetrate the damaged areas. In this study, removal experiments were conducted to identify the most dominant factor in fouling removal using water jet-based cleaning, in preparation for the development of non-contact cavitation high-pressure water jet-cleaning robots. The Taguchi method was used to identify influential factors and generate experimental conditions, and equipment systems for the removal experiments were established. Image analysis was performed to assess the bio-fouling occurrences on each specimen before and after cleaning, and numerical simulations of the nozzle were conducted to estimate stagnation pressure and wall shear stress to confirm the effect on micro-fouling removal. The results indicated that pump pressure is the most influential factor in removing large bio-fouling organisms grown in marine environments and on ship surfaces.