Journal of Marine Science and Engineering

Research

18 pages, 6819 KiB

Open AccessArticle

Gird Based Line Segment Detector and Application: Vision System for Autonomous Ship Small Assembly Line

by Jinhong Ding and Chongben Ni

J. Mar. Sci. Eng. 2021, 9(11), 1313; https://doi.org/10.3390/jmse9111313 - 22 Nov 2021

Cited by 2 | Viewed by 1972

The shipbuilding industry demands intelligent robot, which is capable of various tasks without laborious pre-teaching or programming. Vision system guided robots could be a solution for autonomous working. This paper introduces the principle and technique details of a vision system that guides welding [...] Read more.

The shipbuilding industry demands intelligent robot, which is capable of various tasks without laborious pre-teaching or programming. Vision system guided robots could be a solution for autonomous working. This paper introduces the principle and technique details of a vision system that guides welding robots in ship small assembly production. TOF sensors are employed to collect spatial points of workpieces. Huge data amount and complex topology bring great difficulty in the reconstruction of small assemblies. A new unsupervised line segment detector is proposed to reconstruct ship small assemblies from spatial points. Verified using data from actual manufacturing, the method of this paper demonstrated good robustness which is a great advantage for industrial applications. This paper’s work has been implemented in shipyards and shows good commercial potential. Intelligent, flexible industrial robots could be implemented with the findings of this study, which will push forward intelligent manufacturing in the shipbuilding industry. Full article

(This article belongs to the Special Issue Smart Technologies for Shipbuilding)

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24 pages, 4689 KiB

Open AccessArticle

Physical Welding Factors for Reclassified Welding Positions in Shipbuilding Assembly Process Based on Muscle Activity Measured by Surface Electromyography

by So-Yeon Baek and Jong-Ho Nam

J. Mar. Sci. Eng. 2021, 9(11), 1211; https://doi.org/10.3390/jmse9111211 - 02 Nov 2021

Cited by 2 | Viewed by 3970

Abstract

Welding, a key technology in the shipbuilding industry, is mostly performed by hand, owing to the complex structure and shape of production blocks. This manual welding requires a variety of working postures, which have become an important determinant of the worker’s workload and, [...] Read more.

Welding, a key technology in the shipbuilding industry, is mostly performed by hand, owing to the complex structure and shape of production blocks. This manual welding requires a variety of working postures, which have become an important determinant of the worker’s workload and, consequently, assembly man-hours. Currently, major shipyards calculate welding man-hours by reflecting the welding factor, which is defined as the working time consumed in the welding process. A set of welding factors is known to be based on the accumulated experience in shipyards, whereas the verification or derivation process for these factors is not disclosed or available. This study proposed a method for quantitatively calculating work difficulty for welding positions based on the working posture in a process where the posture acts as an important variable. Standard welding positions reflecting the actual welding work at shipyards were established. A physiological assessment method was used to propose the physical welding factor by analyzing the measured muscle activity. The validity of the proposed method was verified by comparing the results of a musculoskeletal simulation package and shipyard welding factors. The proposed method can be readily applied to other fields in which workers’ physical activities are involved. Full article

(This article belongs to the Special Issue Smart Technologies for Shipbuilding)

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27 pages, 53355 KiB

Open AccessArticle

Firefighting Equipment Arrangement Optimization for an Offshore Platform Considering Travel Distances

by Byeong Cheol Lee, Youngsu Choi and Hyun Chung

J. Mar. Sci. Eng. 2021, 9(5), 503; https://doi.org/10.3390/jmse9050503 - 07 May 2021

Cited by 1 | Viewed by 1700

Abstract

The offshore plant, due to its characteristics, is subject to many restrictions on the material and design of the pipes. Because the design of the firefighting piping depends on the pre-set fire protection design, it is possible to reduce the cost of the [...] Read more.

The offshore plant, due to its characteristics, is subject to many restrictions on the material and design of the pipes. Because the design of the firefighting piping depends on the pre-set fire protection design, it is possible to reduce the cost of the piping design by optimizing the arrangement of the firefighting equipment. Existing studies have low accuracy in obtaining service areas under these conditions. In addition, the arrangement optimization problem is generally modeled as a set cover problem (SCP). However, except for the traditional greedy approximation, this problem is not well researched for general solutions. In this paper, first, a modified iterative-deepening search (MIDS), which accurately obtains a service area according to the travel distance in the grid space, is proposed before optimization. Additionally, this paper seeks to define a set cover problem by combining the subsets obtained by MIDS. Second, by using the traditional greedy algorithm, we obtained the initial arrangement of the firefighting equipment. Then, we proposed a method to obtain an approximate optimization solution using a modified greedy method including rearrangement. The validity of the proposed coverage area acquisition and arrangement optimization method is verified by comparing the performance with other algorithms. Finally, this study was applied to the drawings of an actual offshore platform. Full article

(This article belongs to the Special Issue Smart Technologies for Shipbuilding)

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11 pages, 4039 KiB

Open AccessArticle

The Effect of High Glass Fiber Content and Reinforcement Combination on Pulse-Echo Ultrasonic Measurement of Composite Ship Structures

by Sang-Gyu Lee, Daekyun Oh and Jong Hun Woo

J. Mar. Sci. Eng. 2021, 9(4), 379; https://doi.org/10.3390/jmse9040379 - 02 Apr 2021

Cited by 13 | Viewed by 2573

Abstract

Ship structures made of glass fiber-reinforced polymer (GFRP) composite laminates are considerably thicker than aircraft and automobile structures and more likely to contain voids. The production characteristics of such composite laminates were investigated in this study by ultrasonic nondestructive evaluation (NDE). The laminate [...] Read more.

Ship structures made of glass fiber-reinforced polymer (GFRP) composite laminates are considerably thicker than aircraft and automobile structures and more likely to contain voids. The production characteristics of such composite laminates were investigated in this study by ultrasonic nondestructive evaluation (NDE). The laminate samples were produced from E-glass chopped strand mat (CSM) and woven roving (WR) fabrics with different glass fiber contents of 30–70%. Approximately 300 pulse-echo ultrasonic A-scans were performed on each sample. The laminate samples produced from only CSM tended to contain more voids compared with those produced from a combination of CSM and WR, resulting in the relative density of the former being lower than the design value, particularly for high glass fiber contents of ≥50%. The velocity of the ultrasonic waves through the CSM-only laminates was also lower for higher glass fiber contents, whereas it steadily increased for combined CSM–WR laminates. Burn-off tests of the laminates further revealed that the fabric configuration of the combined CSM–WR laminates was of higher quality, prevented the formation of voids, and improved inter-layer bonding. These findings indicate that combined CSM–WR laminates should be used to achieve more accurate ultrasonic NDE of GFRP composite structures. Full article

(This article belongs to the Special Issue Smart Technologies for Shipbuilding)

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20 pages, 4560 KiB

Open AccessArticle

Application Research of Digital Twin-Driven Ship Intelligent Manufacturing System: Pipe Machining Production Line

by Qingcai Wu, Yunsheng Mao, Jianxun Chen and Chong Wang

J. Mar. Sci. Eng. 2021, 9(3), 338; https://doi.org/10.3390/jmse9030338 - 19 Mar 2021

Cited by 37 | Viewed by 4674

Abstract

Digital twin has aroused extensive attention of international academia and industry to support future interaction with the physical and virtual world. Although the research and application of digital twin spring up continuously, the concept in the manufacturing domain remains in its infancy. In [...] Read more.

Digital twin has aroused extensive attention of international academia and industry to support future interaction with the physical and virtual world. Although the research and application of digital twin spring up continuously, the concept in the manufacturing domain remains in its infancy. In this context, this paper first reviews the applications of digital twins for intelligent manufacturing. Then it presents an innovative application framework of a digital twin-driven ship intelligent manufacturing system and analyzes its operation mechanism. The application framework of a digital twin-driven ship intelligent manufacturing system mainly includes five parts: the physical layer, model layer, data layer, system layer, and application layer. Finally, key enabling techniques, as well as a case study in a pipe machining production line, are constructed and studied to validate the proposed approach. Meanwhile, system design and implementation, the twin modeling construction, application process, and implementation effect of the pipe machining production line are described in detail to provide a reference for enterprises. Full article

(This article belongs to the Special Issue Smart Technologies for Shipbuilding)

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22 pages, 7823 KiB

Open AccessArticle

Development of Augmented Reality System for Productivity Enhancement in Offshore Plant Construction

by Sungin Choi and Jung-Seo Park

J. Mar. Sci. Eng. 2021, 9(2), 209; https://doi.org/10.3390/jmse9020209 - 17 Feb 2021

Cited by 11 | Viewed by 3607

Abstract

As the scale of offshore plants has gradually increased, the amount of management points has significantly increased. Therefore, there are needs for innovative process control, quality management, and an installation support system to improve productivity and efficiency for timely construction. In this paper, [...] Read more.

As the scale of offshore plants has gradually increased, the amount of management points has significantly increased. Therefore, there are needs for innovative process control, quality management, and an installation support system to improve productivity and efficiency for timely construction. In this paper, we introduce a novel approach to deal with these issues using augmented reality (AR) technology. The core of successful AR implementation is up to scene matching through accurate pose (position and alignment) estimation using an AR camera. To achieve this, this paper first introduces an accurate marker registration technique that can be used in huge structures. In order to improve the precision of marker registration, we propose a method that utilizes the natural feature points and the marker corner points in the optimization step simultaneously. Subsequently, a method of precisely generating AR scenes by utilizing these registered markers is described. Finally, to validate the proposed method, the best practices and its effects are introduced. Based on the proposed AR system, construction workers are now able to quickly navigate to onboard destinations by themselves. In addition, they are able to intuitively install and inspect outfitting parts without paper drawings. Through field tests and surveys, we confirm that AR-based inspection has a significant time-saving effect compared to conventional drawing-based inspection. Full article

(This article belongs to the Special Issue Smart Technologies for Shipbuilding)

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19 pages, 4281 KiB

Open AccessArticle

Estimating Production Metric for Ship Assembly Based on Geometric and Production Information of Ship Block Model

by Won-Seok Choi, Dong-Ham Kim, Jong-Ho Nam, Min-Jun Kim and Young-Bin Son

J. Mar. Sci. Eng. 2021, 9(1), 39; https://doi.org/10.3390/jmse9010039 - 02 Jan 2021

Cited by 6 | Viewed by 3349

Abstract

To secure technological competitiveness in shipbuilding and offshore industries, the continuous application and development of various technologies is essential. Efficient scheduling in shipyards is an important management task, whereby materials and manpower are allocated at the appropriate time and to the correct workspace. [...] Read more.

To secure technological competitiveness in shipbuilding and offshore industries, the continuous application and development of various technologies is essential. Efficient scheduling in shipyards is an important management task, whereby materials and manpower are allocated at the appropriate time and to the correct workspace. Although some large shipyards ensure effective scheduling and production management through simulations employing advanced technologies, most shipbuilding industries, including small- and medium-sized shipyards, continue to use an index based on past experiences. However, this legacy index, termed the basic unit, involves poor engineering logic; therefore, it does not appropriately reflect a shipyard’s working environment, which changes rapidly in response to technological developments. Although this has led to a demand for improvements in the basic unit, a clear solution has not been presented thus far. In this study, a method for calculating the man-hours required for assembly, which is the basis for preparing the basic unit, is proposed. First, the assembly process is analyzed, and individual activities involved in the assembly process are quantified and formulated into working hours, which is defined as a production metric. Based on a ship’s computerized block model, the geometric properties and production information required for calculating the metric are generated automatically as far as possible; this is to establish a convenient production metric calculation system. The proposed method features complete applicability in new shipyards through a customization. It also serves as a tool for predicting the metric of new ships or comparisons with those of existing ships. Full article

(This article belongs to the Special Issue Smart Technologies for Shipbuilding)

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14 pages, 4044 KiB

Open AccessArticle

Research on Real-Time Optimal Path Planning Model and Algorithm for Ship Block Transportation in Shipyard

by Chong Wang, Kang Wang, Jiabin Tao and Yongqing Zhou

J. Mar. Sci. Eng. 2020, 8(12), 991; https://doi.org/10.3390/jmse8120991 - 05 Dec 2020

Cited by 5 | Viewed by 2195

Abstract

Special vehicles called transporters are used to deliver heavy blocks in the shipyard. With the development and application of information and communication technology in shipyards, the real-time positioning and ship blocks online scheduling system for transporters are being developed. The real-time path planning [...] Read more.

Special vehicles called transporters are used to deliver heavy blocks in the shipyard. With the development and application of information and communication technology in shipyards, the real-time positioning and ship blocks online scheduling system for transporters are being developed. The real-time path planning of transporters is important for maintaining the overall production schedule of ship blocks. Because of the large volume and heavy weight of ship blocks, there may be some problems, such as high energy consumption, block deformation and other security issues, when transporters loading a block make a turn. So, fewer turns of the transporters are also important to make a block transportation schedule. The minimum driving distance and fewer turns are considered simultaneously for transporter real-time path planning in this paper. A hybrid model considering the number of turns and the optimal path of the transporter is constructed. Moreover, the optimal scheduling model, considering path missing, is also discussed. Several shortest path algorithms are analyzed, which show that the Dijkstra algorithm is the best way to solve this model. From the attained simulation results, we demonstrate that the proposed model and algorithm have the ability to effectively solve real-time path planning for the ship block transportation in shipyards. Full article

(This article belongs to the Special Issue Smart Technologies for Shipbuilding)

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16 pages, 8577 KiB

Open AccessFeature PaperArticle

Thermal Stress Analysis of Process Piping System Installed on LNG Vessel Subject to Hull Design Loads

by Se-Yun Hwang, Min-Seok Kim and Jang-Hyun Lee

J. Mar. Sci. Eng. 2020, 8(11), 926; https://doi.org/10.3390/jmse8110926 - 16 Nov 2020

Cited by 7 | Viewed by 5897

Abstract

In this paper, the procedure for the strength evaluation of the piping system installed on liquefied natural gas (LNG) carriers is discussed. A procedure that accounts for the ship’s wave load and hull motion acceleration (as well as the deformation due to the [...] Read more.

In this paper, the procedure for the strength evaluation of the piping system installed on liquefied natural gas (LNG) carriers is discussed. A procedure that accounts for the ship’s wave load and hull motion acceleration (as well as the deformation due to the thermal expansion and contraction experienced by the hull during seafaring operations) is presented. The load due to the temperature and self-weight of the piping installed on the deck is also considered. Various operating and load conditions of the LNG piping system are analyzed. Stress analysis is performed by combining various conditions of sustained, occasional, and expansion loads. Stress is assessed using finite element analysis based on beam elements that represent the behavior of the piping. The attributes of the piping system components (such as valves, expansion joints, and supports) are represented in the finite element model while CAESAR-II, a commercial software is used for finite element analysis. Component modeling, load assignment, and load combinations are presented to evaluate pipe stresses under various load conditions. An evaluation model is selected for the piping arrangement of LNG and the evaluated stress is compared with the allowable stress defined by the American Society of Mechanical Engineers (ASME). Full article

(This article belongs to the Special Issue Smart Technologies for Shipbuilding)

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21 pages, 5127 KiB

Open AccessArticle

Development of Entering Order and Work-Volume Assignment Algorithms for the Management of Piping Components in Offshore Structure Construction

by Jung Goo Park, Ho Jung Kim and Jong Hun Woo

J. Mar. Sci. Eng. 2020, 8(11), 894; https://doi.org/10.3390/jmse8110894 - 09 Nov 2020

Cited by 2 | Viewed by 2000

Abstract

In the early 2010s, with rising oil prices and increasing purchase orders for offshore structures for deep-sea resource development, the shipyards that took these orders suffered unexpected losses. Unlike the construction of commercial carrier vessels, the construction of offshore structures necessary to develop [...] Read more.

In the early 2010s, with rising oil prices and increasing purchase orders for offshore structures for deep-sea resource development, the shipyards that took these orders suffered unexpected losses. Unlike the construction of commercial carrier vessels, the construction of offshore structures necessary to develop deep-sea resources is difficult to manage due to the complexity of the outfitting process of the topside structure, which is a plant for gas and oil production and treatment. Piping components in particular, which comprise most of the design items, are difficult to manage because they involve 2 to 3 times the man-hours and up to 10 times the quantity of items compared to commercial carrier vessels. Due to not only high man-hours and quantity but also large fluctuations caused by design changes and long procurement lead times, process delays that result in delayed compensation frequently occurred. In response, Samsung Heavy Industries developed an integrated management system for piping components. This study describes the entering order optimization algorithm and work-volume assignment optimization algorithm, which are the core algorithms of this system. The entering order optimization algorithm determines the optimal installation order considering the procurement status of the piping components and the installation readiness status of the installation work site, through which it determines the entering order of the piping components. The algorithm seeks to accelerate the completion rate of installation of the piping components. Next, to minimize delivery delays of sub-contractors to the shipyard, this study developed a work-volume assignment optimization algorithm that can equalize the load on multiple sub-contractors considering the raw material readiness status and the production capacity of the sub-contractors, in terms of materials that must be ordered from external sub-contractors among the piping components whose entering order was determined. Finally, applying the algorithm developed using actual shipyard data resulted in an accelerated completion rate of installation and improved balance of load in terms of volume assigned to the sub-contractors. Full article

(This article belongs to the Special Issue Smart Technologies for Shipbuilding)

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24 pages, 5887 KiB

Open AccessArticle

Prediction of Ocean Weather Based on Denoising AutoEncoder and Convolutional LSTM

by Ki-Su Kim, June-Beom Lee, Myung-Il Roh, Ki-Min Han and Gap-Heon Lee

J. Mar. Sci. Eng. 2020, 8(10), 805; https://doi.org/10.3390/jmse8100805 - 16 Oct 2020

Cited by 29 | Viewed by 4476

Abstract

The path planning of a ship requires much information, and one of the essential factors is predicting the ocean environment. Ocean weather can generally be gathered from forecasting information provided by weather centers. However, these data are difficult to obtain when satellite communication [...] Read more.

The path planning of a ship requires much information, and one of the essential factors is predicting the ocean environment. Ocean weather can generally be gathered from forecasting information provided by weather centers. However, these data are difficult to obtain when satellite communication is unstable during voyages, or there are cases where forecast data for a more extended period of time are needed for the operation of the fleet. Therefore, shipping companies and classification societies have attempted to establish a model for predicting the ocean weather on its own. Historically, ocean weather has been primarily predicted using empirical and numerical methods. Recently, a method for predicting ocean weather using deep learning has emerged. In this study, a deep learning model combining a denoising AutoEncoder and convolutional long short-term memory (LSTM) was proposed to predict the ocean weather worldwide. The denoising AutoEncoder is effective for removing noise that hinders the training of deep learning models. While the LSTM could be used as time-series inputs at specific points, the convolutional LSTM can use time-series images as inputs, making them suitable for predicting a wide range of ocean weather. Herein, using the proposed model, eight parameters of ocean weather were predicted. The proposed learning model predicted ocean weather after one week, showing an average error of 6.7%. The results show the applicability of the proposed learning model for predicting ocean weather. Full article

(This article belongs to the Special Issue Smart Technologies for Shipbuilding)

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15 pages, 7198 KiB

Open AccessFeature PaperArticle

Modified Equivalent Load Method for Welding Distortion Analysis

by Jaemin Lee and Hyun Chung

J. Mar. Sci. Eng. 2020, 8(10), 794; https://doi.org/10.3390/jmse8100794 - 13 Oct 2020

Cited by 9 | Viewed by 2769

Abstract

In this study, modified equivalent load method for welding distortion analysis is suggested to improve its accuracy. To avoid the excessive computational time for welding distortion analysis of large welded structures, shell element-based elastic analysis methods are widely used, applying the inherent deformation [...] Read more.

In this study, modified equivalent load method for welding distortion analysis is suggested to improve its accuracy. To avoid the excessive computational time for welding distortion analysis of large welded structures, shell element-based elastic analysis methods are widely used, applying the inherent deformation approach. Equivalent nodal forces are commonly used in common FE (Finite Element) codes to enter these inherent deformation values. However, the conventional method cannot estimate precise longitudinal bending following the conventional equation. In this study, the problem of the existing equivalent load method is analyzed by a case study, and the modified equivalent load method that can estimate angular distortion, transverse shrinkage, and longitudinal bending is presented based on the FEM principle. The results show that by applying the proposed method, the shell element-based elastic FE approach for the welding distortion analysis can be achieved with improved accuracy. Full article

(This article belongs to the Special Issue Smart Technologies for Shipbuilding)

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12 pages, 19335 KiB

Open AccessArticle

Real-Time Prediction of Large-Scale Ship Model Vertical Acceleration Based on Recurrent Neural Network

by Yumin Su, Jianfeng Lin, Dagang Zhao, Chunyu Guo, Chao Wang and Hang Guo

J. Mar. Sci. Eng. 2020, 8(10), 777; https://doi.org/10.3390/jmse8100777 - 04 Oct 2020

Cited by 26 | Viewed by 2436

Abstract

In marine environments, ships are bound to be disturbed by several external factors, which can cause stochastic fluctuations and strong nonlinearity in the ship motion. Predicting ship motion is pivotal to ensuring ship safety and providing early warning of risks. This report proposes [...] Read more.

In marine environments, ships are bound to be disturbed by several external factors, which can cause stochastic fluctuations and strong nonlinearity in the ship motion. Predicting ship motion is pivotal to ensuring ship safety and providing early warning of risks. This report proposes a real-time ship vertical acceleration prediction algorithm based on the long short-term memory (LSTM) and gated recurrent units (GRU) models of a recurrent neural network. The vertical acceleration time history data at the bow, middle, and stern of a large-scale ship model were obtained by performing a self-propulsion test at sea, and the original data were pre-processed by resampling and normalisation via Python. The prediction results revealed that the proposed algorithm could accurately predict the acceleration time history data of the large-scale ship model, and the root mean square error between the predicted and real values was no greater than 0.1. The optimised multivariate time series prediction program could reduce the calculation time by approximately 55% compared to that of a univariate time series prediction program, and the run time of the GRU model was better than that of the LSTM model. Full article

(This article belongs to the Special Issue Smart Technologies for Shipbuilding)

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14 pages, 6594 KiB

Open AccessFeature PaperArticle

A Method to Minimize the Data Size of a Lightweight Model for Ship and Offshore Plant Structure Using Part Characteristics

by Kiyoun Kwon and Duhwan Mun

J. Mar. Sci. Eng. 2020, 8(10), 763; https://doi.org/10.3390/jmse8100763 - 30 Sep 2020

Cited by 9 | Viewed by 1937

Abstract

One of the most widely used methods for representing the shapes of ships and offshore plants is triangular mesh, which has a simple structure and is easy to visualize. In particular, lightweight models composed of triangular meshes are often used as a sharing [...] Read more.

One of the most widely used methods for representing the shapes of ships and offshore plants is triangular mesh, which has a simple structure and is easy to visualize. In particular, lightweight models composed of triangular meshes are often used as a sharing medium for three-dimensional (3D) shape design results in the collaboration process among many stakeholders participating in the construction process. Currently, there are demands for visualizing the total shapes of ships or offshore plants for design review, interference check, construction monitoring, and securing maintenance space. However, this requires high computing power and much time due to the large size of the triangular mesh model. We have two general solutions as follows: simplifying the shape of the ship and offshore plant structure and reducing the size of the lightweight file itself. Between them, this study proposes a method for reducing the lightweight file. This method classifies the part types of the ship or offshore plant structure and then only stores the minimum triangular mesh information for each part type, excluding unnecessary information. Then, the topographic information of triangular meshes is stored together in the lightweight file to shorten the time required for restoration of the lightweight file. Full article

(This article belongs to the Special Issue Smart Technologies for Shipbuilding)

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