A Simulation-based Shipbuilding System for Evaluation of Validity in Design and Manufacturing * Hongtae Kim, Jong-Gap Lee, Soon-Sup Lee, Jin. H. Park Korea Research Institute of Ships & Ocean Engineering/KORDI, Daejeon, Korea
[email protected] Abstract - This paper is concerned with simulationbased approaches in the shipbuilding industry such as digital shipbuilding, simulation-based design (SBD), and virtual shipyard. A simulation-based shipbuilding model based on the function model of ship design and the process model of ship manufacturing is suggested. For application and implementation of the proposed model, the process model for block erection processes is designed using IDEF0 and UML methodologies. In addition, an application is developed to evaluate the validity of simulation-based shipbuilding models. This application is called the virtual assembly simulation system for shipbuilding (VASSS), which can simulate crane operation and block erection in a virtual dock. Keywords: Digital shipbuilding, simulation, process modeling.
1
Introduction
The emerging information and communication technologies of shipbuilding industrial environments are rapidly changing. To respond to this changing situation, a new paradigm has matured with new concepts such as the concrete method. In particular, all efforts are shown to be concentrated on the realization of the concept of SBD based on 3D ship CAD system. The objective of such concepts are the computerization of the whole process of ship production, the detection of errors in the initial stages of the process by making use of such technologies as simulation and virtual reality, and the performance of efficient decision making. In this paper, related technologies, areas of application, and methods of digital shipbuilding in the shipbuilding and marine industries are presented. Then, a simulation-based shipbuilding model for ship design and production is suggested. In addition, virtual assembly simulation system for shipbuilding (VASSS), a tool for crane operability and block erection simulation in virtual docks based on the 3D product model, will be introduced. *
0-7803-7952-7/03/$17.00 2003 IEEE.
2
Simulation-based ship design and manufacturing
Up to now, research related to simulation-based shipbuilding systems and their applications have been incomplete, and design demonstration of constructed ships is only partially done for use in sales or assembly simulation of welding robots. Research aimed at the realization of virtual shipyard in an integrated environment have yet to be conducted as new concept ships and large marine structures include thousands of different parts and, therefore, the performance and cost of hardware and software that can process such a vast amount of information can be difficult to achieve under irregular working environments. In addition, a few characteristics of shipbuilding industry could also be the reason that such research has yet to be conducted. Generally, shipbuilding is order based and a new design is made for each new ship. Furthermore, the whole process from contract and design to building happens concurrently. The cycle of design/manufacturing/ maintenance is repeated, where through each stage, information becomes more detailed. Many processes are mainly dependent on human labor and require qualitative information making it difficult to extract detailed information in early stages. The only possible way to overcome these limitations and reduce the lead-time of the process from design to manufacturing is through the use of computers. Since computers are already widely used and the current level of their usage is very high, simulation-based shipbuilding process can lead to greatly reduced manufacturing time than can conventional sequential process from design through process planning to manufacturing. Evaluation of production capability in the early design stage is very important. The importance is shown vividly in relation with production cost and the possibility of cost reduction [10]. In other words, early evaluations of design and manufacturing activities occupy a low percentage of total cost, but they have big effects on cost reduction. However,
in general, early evaluation requires a vast amount of information on design and manufacturing, and frequently it is not an easy task. If a simulation-based shipbuilding system is used, all elements and activities (both in design and manufacturing) that are required for product development will be modeled in a computer-based product model, and the whole design and manufacturing process can be simulated in a computer environment.
3
Current research works application examples
and
Recently, much government funded research has been conducted for the purpose of turning the originally labor intensive and experience centered shipbuilding industry into a knowledge based and technology intensive industry with advancements in information technology based on computer technology. The United States Navy's Defense Advanced Research Projects Agency (DARPA) runs a simulation based design (SBD) program in order to develop a design system/environment that can reduce the cost of system design and developments, reduce development time, and verify and reduce risks . Starting in 1996, phase I of the SBD program established an environment for the implementation of SBD, and in phase II, SBD architecture that supports verification of phase I concepts are being developed [2][3]. DARPA has tried to develop a few prototypes to apply the SBD concept in feasibility studies and follow-up research. Good examples are the operation simulation of LPD-17, a next generation carrier, NSSN submarine development of General Dynamics Electric Boat Division, and Mobile Offshore Base of the Gulf Coast Region Marine Technology Center (GCRMTC). The technology used in these development processes is being commercialized. In addition, Bath Iron Works (BIW) performed simulation of crane usage, floating drydock usage, dock and pier usage, installation and removal of production equipment, emergency vehicle movement and routes through yards, and personnel emergency evacuation routes from ships [5]. The Virtual Reality Laboratory (VRL) in the University of Michigan is doing research on the application of virtual reality, such as immersive virtual reality and augmented reality, to industries [1]. This research includes structural walk-through modeling, accident simulation and training simulation. Projects related to virtual prototyping and virtual reality are ship motion simulation, and virtual simulation of the shipbuilding process. Traditionally, Europe has led shipbuilding system technology and naval/marine related organizations conducting inter or international projects through the European Strategic Program for Research and
Development in Information Technology (ESPRIT) project. Representative of such projects is the Management and Reuse of Information over Time (MARITIME) project led by the Norwegian ship registration office (DNV) with many European naval related organizations and run as a part of the ESPRIT III project. The main purpose is the development of an infrastructure of next generation naval systems based on the ship product model, with the aim of leading naval system technology worldwide through internal standardization and commercialization of project results. The Department of Ship and Marine Technology in University of Strathclyde is conducting research on computer technology applications and interfaces between human factors as means to achieve the objective of shipyards such as user requirements, competitiveness of ships, cost efficiency, and safety, under the rapidly changing environment of the shipbuilding industry [11]. The main project includes "Sub-sea Navigation of Remotely Operated Vehicles (ROV)" and "Evacuation Simulation of Ro-Ro Ferry Ships". Japan is trying at governmental level to maintain its current level of technology and competitiveness while turning the shipbuilding industry into a futuristic industry. Under the direction of the Ship and Ocean Foundation (SOF), the Computer Integrated Manufacturing for Shipbuilding (CIMS) project was begun in the mid-1980s and was succeeded by the General Product Model Environment (GPME) project in 1996 to acquire technology for putting ship CIM models to practical use. Recently, the GPME based advanced CIM, which is related to knowledge sharing technology, and the LINKS project for implementing virtual shipyard under the CALS concept were completed. The shipbuilding industry in Korea is the top in the world in the amount of building, but in terms of quality of technology, it is still behind other countries. In Korea the Computerized Ship Design and Production System (CSDP) project led by the Korea Research Institute of Ships & Ocean Engineering (KRISO) was initiated to acquire ship CIM base technology the ship manufacturing system integration technology development project for acquiring application technology was completed, and, recently, preparations have been made for ship CALS/EC development.
4 4.1
Simulation-based shipbuilding model Framework of simulation-based shipbuilding model
To establish a simulation-based shipbuilding environment, the most important factor is successfully resolving the planning problem. Planning in the shipbuilding process is the process of devising a method that minimizes the effects of design change and delay,
supports the appropriate manufacturing method, and maximizes the usage of resources in decision making [6]. However, if planning and production are done without the optimization of decision making during the design and manufacturing process, unexpected delays, unwanted modifications, and various other problems may occur. In other words, to solve problems after the beginning of the planning and production requires changes in plans such as the reassignment of resources. In short, in order to accurately plan the shipbuilding process, the technology for implementing dynamic simulations is required. Simulation-based shipbuilding based on 3D CAD systems can be described as a concept that enables the product and process simulation of a wide range of the whole of the product life cycle including the design, production, and maintenance under virtual computer environments. Figure 1 shows the framework of the simulationbased shipbuilding model. To realize simulation-based shipbuilding, it is necessary to perform both function modeling of the design and operational resources related to ship functions based on a 3D virtual ship prototypes and process modeling of the manufacturing processes, related plans, and manufacturing resources. The results of such modeling and information of virtual ship prototypes should be shared between shipyards, ship registration offices, engineering companies, ship owners, and marine transport companies under a virtual environment.
Product Model (3D CAD System)
Function Models
Design Resource ...
Performance
Process Models
Virtual Ship Prototype
Operation Resource
Workplace ...
Planning & Scheduling Resource
Process Resource
Transportation ...
Job Resource
Worker, Operator
Virtual Shipbuilding Environment
Function Simulation
Process Simulation
- General Arrangement - Equipment Arrangement
- Virtual Dock Simulation - Virtual Assembly Simul.
Figure 1. Framework of simulation-based shipbuilding model
The product model in Figure 1 is a database including the complete definition of the ship being developed. This model in not restricted to geometrical information, and includes non-geometrical parameters such as physical characteristics and performance parameters of all the elements in the system. Here, the product modeling function of ship design and development is dependent on commercial CAD systems.
The function model has a close relation with ship design. To be a virtual prototype that is meaningful in engineering sense, its behavior should be exactly expressed. In other words, behavior based on physical characteristics should be expressed. In this sense, the function model is the model used for expressing the behavior of its object system in the simulation of provided functionalities. It should convey system behavior pattern and output responses to control input. The function model should be able to take input from other system models, and provide output for the simulation of other systems. Also, it should be connected with the geometric and characteristics database of the product model. The process model is an indispensable model for ship manufacturing. The process model requires the expression of the product and process. In other words, not only the information of the product to be produced, but also the assembly sequence, the manufacturing technology or assembly process according to the production plan should be incorporated as well. In addition, as an example of the process model, it includes certain behavior to quantify phenomena happening during the building process such as welding distortion. To express various production patterns of ships, various process models are required. The creation of building models plays an important role in the creation of adequate virtual prototypes or production of prototypes. The virtual prototype is in the form of a product model, function model, and process model combined, and should be manipulated in a virtual environment. For the virtual prototype to achieve the real time response required in a design and development environment, a high power computer that can recalculate the vast geometry database that composes a part of the product model is required. In addition, in order to ensure real-time responses to input data and interaction among prototype, system, and environment, high computing power that can process countless calculations related to the function model are also required. Currently, computer systems that can manage such a large amount of data in a design environment are not commercially available yet. However, designers, developers, operators, and manufacturers use only part of product model database according to their needs, therefore, a collection of small prototypes adequate to each function rather than one complete prototype with all the necessary functions is more realistic. In addition, for the efficient operation of simulation systems using virtual prototypes, an important issue to resolve is real-time processing, which is considered as being in the area of high performance visualization. While CAD systems focus on 3D solid objects, high performance visualization focuses on surface rendering. The basic expression unit of an image is the polygon, and frequently millions of polygons are necessary for realistic frames. In this sense, partial simplification is necessary
for product models to perform as geometry models for virtual prototypes. Virtual shipbuilding environments indicate the area where virtual prototypes are appropriately operated. Virtual prototypes in virtual environment require separate virtual systems to simulate integration with other previous operation systems. These systems should be able to integrate virtual objects with real objects in simulated environments to satisfy all fields of virtual experience. In addition, previous systems should be converted to virtual counterparts to be inserted into virtual environments. However, sometimes, Distributed Manufacturing Simulation (DMS) is used to integrate distributed systems and system concepts [8]. Under the virtual environment, some arenas of application for simulation-based shipbuilding in the ship design and manufacturing can be done. These are function simulation, process simulation, and safety simulation. Function simulation includes verification of the main functions of ships such as the evaluation of General Arrangement (GA), various equipment, and cargo loading/unloading. Other typical ship function simulations are Ro-Ro ships loading simulations, passenger flow simulations, galley operations simulations, and simulation of anchor handling, which replace awkward plastic models. Some simulations are a combination of both continuous and event based simulator programs: for example, on a Ro-Ro loading simulation, the truck driving times to stowage positions are found out by using continuous simulators and, based on that information, the loading process is optimized using an event based simulator. Process simulation includes evaluation of manufacturing processes such as the evaluation of processes and resource planning, and the manufacturing of automation equipment. Other typical process simulations are the simulation of the entire prefabrication facility, simulation of different ship construction approaches, simulation of steel fabrication lines and simulation of block erection process. Generally, the development process of ship or marine structures is done in the order of conceptual design, basic design, detailed design, production design, building, maintenance, and operation.
4.2
Analysis
and
design
of
simulation-based
shipbuilding model The simulation-based shipbuilding model is composed of a ship function model and a ship process model. The function model represents design and operational resources related to ship functions based on the 3D virtual ship prototype. The process model
represents the manufacturing process, related plan, and manufacturing resources. Ship
Function Model
Process Model
Capability
Floating
Movement
Fabrication
Cargos
Shape
Performance
Fabrication Planning
Weight
Basic Calculation
Pre-processing Speed
Seaworthiness
Intact
Resistance
Seakeeping
Propulsion
Maneuvering
Damage LCB
Bending Moment
Forming Part Assembly
KB
Shear Force
Stability Stability
Erection Erection Planning
Sub-block Assembly
Block Lift & Transport
Semi-block Assembly
Block Setting
Cutting
Stability Stability Buoyancy Curve
Assembly Planning
Hydrodynamic
Loading Hydrostatics
Assembly
Block Assembly
Stability Stability
Accuracy Check Cutting
Inspection
Welding
Fitting
Figure 2. Planning Level Information Model for SimulationBased Shipbuilding
Figure 2 represents the planning level information model including the function model and the process model of ships for simulation-based shipbuilding. The function model is deployed by ship function including capacity, floating, and movement. The process model is deployed by production stages including fabrication, assembly, and erection. Many methodologies have been constructed for the efficient analysis and design of manufacturing systems. Among these are the CIM-Open System Architecture (CIM-OSA), Group de Recherche en Automatisation Integriel (GARI), Nijssen Information Analysis Mehtod (NIAM), Integration Definition (IDEF) methodology, and Unified Modeling Language (UML) [9]. IDEF0 method is frequently used to analyze CIM systems. UML is a modeling language that visualizes, describes, establishes software systems, and documents its products. UML integrated conventional object-oriented methods such as OMT (Object Management Technique), Booch, and Objectory and is now a standard objectoriented methodology of the OMG (Object Management Group). UML is a powerful object-oriented methodology to describe features, activities, and states of a system and is frequently used in the process of software design. Object-orientation concepts describe systems as they are. Classes are identified and then interactions among those classes are modeled. This feature makes it possible to make a thoroughgoing design of the simulation model. In this research, IDEF0 and UML models are used for the design of simulation-based shipbuilding models. Because IDEF0 is a functional analysis modeling methodology for constructing information systems, it is used to define general procedures of simulation-based shipbuilding systems. As shown in Figure 3, the process model and the function model are defined by activity and resources through the IDEF0 method. The UML model is
used for detailed design of simulation objects. All the product facilities and design elements are identified as classes. Each class consists of attributes, methods, and a name. These elements are obtained from the transition mechanism described below. Control
Activity Diagram in IDEF0 Model
… Input
Output
…
…
Activity
Resource
type_of
type_of
type_of CSimObj
method_of
name_of CFunction
CProcessM
method_of
Class Diagram in UML Model
Figure 3. Transition mechanism from IDEF0 to UML model
Activities of IDEF0 are transferred to methods of the subclass of CProcessM. Also, resources in IDEFO are transferred to class names of the subclass of CProcessM or methods of the subclass of CFunction in the UML class diagram. Other factors such as control, input, and output in IDEF0 become instances of CSimObj’s subclass.
5
Applications and implementation
For the verification of the suggested methodology the Virtual Assembly Simulation System for Shipbuilding (VASSS) was developed. VASSS enabled simulation of block erection process plan items such as the location of block erection decisions and erection sequence evaluation taking account of information and ability of equipment from 3D CAD systems. In other words, VASSS can evaluate block erection sequences by taking account of product data related to block and equipment such as goliath cranes. 5.1
Description of block erection process
The block erection process begins from on-block outfitting of blocks produced from the assembly process. Then, the blocks are painted, pre-erected, and finally erected on dock. From the viewpoint of manufacturing planning, first, a building schedule (dock usage plan) is made based on long-term load balancing and the master schedule. Then, the beginning date for each line and dock, launching date, and on-board outfitting time is decided. Based on these timelines, a block erection schedule is established. Generally, other manufacturing process schedules are established based on this schedule. Process planning in block erection can be summarized as selecting keel blocks and floating blocks,
grouping of pre-erection blocks, and decisions on block erection sequences. Among these, the ones that are closely related to CAD systems are the selection of floating blocks and the grouping pre-erection blocks. Keel block selection and floating block selection are to be decided during production. This research focuses on the evaluation of block erection sequences that are closely related with production planning function. Since the block erection process is used as a base for other planning, it should be the initial planning to be established in the intermediate schedule of ship manufacturing planning. Current methods for deciding erection methods are usually based on experience or previous methods for appropriate hull form or ship type. However, these methods do not guarantee good results when dock or batch construction situation is rapidly changing. Most previous research on generation block erection sequences use constraint directed graph searches based on expert knowledge [7] and block assembly information. In this research, block position and erection methods are used to generate block erection sequences. Since general ship structure has the block type of up and down, left a right, and front and back, the block, which has neighboring blocks below, either left or right, and either front or back will be possible erection block. Selected candidate erection sequence is checked erection feasibility that satisfies possible erection conditions. The general block erection sequence is to select the keel-laying block as a stable block under erection conditions. The blocks are erected in the direction of bow and stern, left and right, and up and down. Erection method can be divided into floor-type, ring-type, and pyramid-type according to ship forming methods, or onepoint type, two-point type, and multi-point type according to keel laying block selection methods [4]. Floor-type erection starts from the keel block in the direction of bow to stern, and the order of construction is from the ship’s bottom through the traverse bulkhead, and from the longitudinal bulkhead to shell plating. Ring-type erection is faster in the upper direction from the ship’s bottom to the upper deck is constructed as one unit. Pyramid-type erection has aspects of both the horizontal and vertical methods. The sequence is from the ship’s bottom through the bulkhead block and from the shell block to the upper deck. The keel laying block is the first block to be erected. In a two-point type and multi-point type, an insert block, which can complicate the erection process, always occurs, but overall erection time can be shortened if block erection occurs at more than two points at the same time.
5.2
Process modeling for ship manufacturing
As an example of the process model, Figure 4 shows the procedure of the block erection process in ship manufacturing using the IDEF0 method.
Also, a sequence diagram and collaboration diagram for the goliath crane operation procedure. A collaboration diagram expresses the relation of objects for operation of goliath crane and a sequence diagram expresses a scenario for operation of goliath crane. These diagrams are used in the simulation method for sequence assessment according to the block erection process, which is described in Section 5.3. 5.3
Virtual Block Assembly Simulation System for Shipbuilding (VASSS)
Figure 4. Activity diagram for block erection process
As shown in this figure, the block erection process is divided into the erection plan, lift/transport operation and welding operation. The input data for the block erection process is composed of drawings and assembly blocks. The control data for the block erection process is composed of the erection method, the welding method, and rules. The mechanism is composed of an erection sequence and erection resources generation program. Figure 5 shows the class diagram for the block erection process. Generally, a class diagram is created to provide a picture or view of some or all of the classes in the model. The class diagram for the block erection process is composed of a process logic class for generation of the erection sequence and a resource class for block erection, which includes worker, crane, dock, and equipment. The elements of class diagrams are obtained from activity diagrams, which are expressed in Figure 4. As shown in Figure 5, activities of IDEF0 are transferred to methods of the subclass of CProcessM, and resources in IDEFO are transferred to class names of subclasses of CProcessM.
To show the feasibility of simulation-based shipbuilding model in the ship production process, the system for sequence assessment during the erection process, VASSS, was developed. VASSS enables crane operation verification and block erection simulation in virtual dock based on 3D product model in the initial stage of ship production. VASSS consists of geometric modeling subsystems, erection sequence generation subsystems, and Computer Aided Engineering (CAE) subsystem.
Product Modeling y Hull Form y Compartment y Part y Block
Block Spec.
y Block Code y Block Type y Equipment Pattern y Welding Length y Fitting Length
Block Analysis Report
Block Weight
Resource Modeling y Dry Dock y Facility
Process Modeling
Simulation Model
Block Erection Simulation y Erection Process y Erect Sequence y Crane Availability
y Standard Pattern for Equipment
AVI files
Block Erection Sequence DB
Figure 6. System configuration of the VASSS
The function of the geometric modeling module is to perform the modeling of the hull form and compartment of the container ship, as well as the modeling of the shape of the goliath crane, the jib crane, and the dry dock. The function of the erection sequence generation module is to provide the candidate erection sequence based on the erection method and block position. The function of the CAE module is to provide the analysis for kinematics and dynamics motions. The Configuration of the system for block erection simulation is shown in Figure 16. 5.3.1
Figure 5. Class diagram for block erection process
Ship Product Model (Design Model)
Block Information
Product and resource modeling
Product information for blocks are entered in the IGES data format, and various equipment such as the goliath crane and dock layout are modeled by device modeling from information extracted from appropriate
blueprints. First, block information is generated from CAD systems, but the amount of data is too large to be used in simulation since all the data about structural parts is included. Therefore, the data is simplified by excluding unnecessary data. Device modeling of work environments means modeling resources as equipment and facilities except product model. Device in this article refers to highlevel entities in the Delmia database, and is constructed from [Device Context]. In order to construct a device, several parts are assembled and their relationships are defined. These devices have a tree structure of attributes that specify part movements and part structures. Facilities and equipment for construction of the virtual dock include the dock, gate, goliath crane, jib crane, and small equipment. 5.3.2
solutions, and if it is too large, solutions may not exist since the accuracy is too low or a collision may escape from two tag points. A trajectory verification function is used in this case. If the verification of block erection processes is perfectly done, actual simulations are performed to verify restraint conditions during the motion process. Various methods such as the Gantt chart, fly, fly-through, walkthrough, and view port are used to view simulation results. In addition, collisions during goliath crane motion can be verified as a process of optimizing block erection sequences by goliath crane. Figure 7 shows the process of optimizing block erection sequences through the above processes.
Simulation of block erection process
VASSS first constructs ship assembly workcells based on product data from 3D CAD systems and block erection sequences from generation algorithms. Then, through process modeling such as equipment usage pattern, VASSS generates path and sequences that can optimize collision free path , erection time and availability. In this research, 3,400 TEU container ships and the dry dock in S shipyard are used for the simulation. In workcell implementation for assembly simulations, many children parts are attached to a parent part in a hierarchical structure. Kinematics and dynamic implementation of devices makes it possible to actually operate and detect collisions with other workloads, workers, or devices. It also includes motion controls, setting paths, GSL implementation, and collision check. GSL is an ENVISION specific interactive programming language for operating devices. When block erection processes is optimized, trajectory paths are created, for which the overall sequence time is estimated using the Gantt chart. Previous movement speed of crane is input and sequences are optimized based on the speed. The auto trajectory function is used for creating collision free paths between two tag points or the whole trajectory. Before using this function, parts or devices that can collide with the device should be defined in the collision queue, and after the collision queue, assembly trajectory can be created. In order to use the auto trajectory function, the user should determine if it is for two tag points or for all trajectories. In addition, options for deciding either transportation or rotation paths should be predetermined. If rotation is selected, computational load is exponentially increased, so in most cases, only optimized path for transportation is used. In creating block erection paths, step size is very important since part movement and collision detection occurs at every step. If this step size is too small, a huge amount of time and computer memory is used on arbitrary
Figure 7. Optimal path of erection process
5.4
Results of simulation
In this research, the evaluation of the block erection methods for container ships is simulated. The three erection methods evaluated are floor-type erection, ringtype erection, and pyramid-type erection with consideration of the number of keel laying blocks (onepoint erection, two-point erection) on the container ship. Table 1. Simulation Results for Evaluation of Erection Methods
Table 1 shows the evaluation results for block erection methods using goliath cranes. Total erection time here considers movement speed of the goliath crane, equipment replacement time, and block fastening time. As shown in Table 1, floor–type and ring-type erection is
almost identical in total erection time and the pyramidtype two-point method takes the least time. Also, as shown in Figure 8, floor–type and ringtype erection is almost identical in total idle time of goliath crane and pyramid-type two-point method takes the least time. As shown in the above results, the pyramidtype two-point method proved to be the most efficient both in erection time and the availability of goliath cranes.
In the future, by applying virtual simulation technology to the design, modeling, analysis, simulation, manufacturing, testing, and information systems under simulation-based manufacturing environments, a basis for concurrent engineering systems can be built, and with CALS/EC, it will be a principal factor affecting the competitiveness of the shipbuilding industry.
References [1] K. Beier, “Web-based virtual reality in design and manufacturing applications, Proceedings of COMPIT 2000, Germany, 2000.
Total Idle Time of Goliath Carne (min)
500
[2] J. Cardner, Simulation of mobile offshore base, Project Report, GCRMTC, 1993.
450
[3] K. Fast, “EVS at electric boat”, Proceedings of Deneb's User Group, Michigan, USA, 1996.
400 350 300 250
1 Point Ty pe 2 Point Ty pe Floor Ty pe
Py ramid Ty pe
Figure 8. Comparison of total idle time of goliath crane Using the above results, it was possible to provide the adequacy of pyramid-type erection, which is the most popular method in shipyards. In addition, VASSS can be used for pre-evaluation of new production methods.
6
Conclusions
Current shipbuilding industries promote next generation shipbuilding systems based on CAD/CAM systems. Naturally, these systems automate conventional processes and increase productivity and quality, but they are limited in introducing fundamental changes to conventional processes or accepting rapidly advancing technologies efficiently. Recently, much attention has been paid to simulation-based manufacturing, which can model and simulate the whole process of manufacturing products including the design. This simulation-based manufacturing environment is called virtual manufacturing, digital manufacturing, or virtual factory, and it is implemented in concepts such as virtual shipyards, and digital shipbuilding. In order to develop practical systems based on the contents of this research, a product model based 3D CAD system and product data management (PDM) technology is needed. Furthermore, technologies for the process of block erection, assembly, processing, cutting, and testing should also be developed with application development and operational verification.
[4] W-K. Ham, K-C. Kim, I-J. Shin, D-S. Um and B-K. Hong, Ship Construction Engineering, pp. 218-221, The Society of Naval Architects of Korea, 1996. [5] J. C. Hugan, “Using simulation to evaluate cargo ship design on the LPD17 program”, Proceedings of the Winter Simulation Conference, Orlando, USA, 2000. [6] H. Kim, “Applying digital manufacturing technology to ship production and maritime environment”, Integrated Manufacturing Systems, Vol. 13, No. 5, pp. 295-305, 2002. [7] J-K. Lee and H-R. Choi, “Erection scheduling at shipbuilding using constraint directed graph search; DASERECT”, Proceedings of Korea-Japan Joint Conference on Expert Systems, Seoul, Korea, 1993. [8] MISSION Consortium, “Intelligent Manufacturing System (IMS) project proposal: modeling and simulation environments for design, planning and operation of globally distributed enterprises (MISSION)”, Version 3.3, Tokyo, Japan, 1998. [9] H. Rozenfeld and A. F. Rentes, “Workflow modeling for advanced manufacturing concepts”, Annals of CIRP, Vol. 43, No. 1, pp. 385-388, 1994. [10] SNAJ(The Society of Naval Architects of Japan), Computer integrated shipping and shipbuilding, 1998. (in Japanes) [11] D. Vassalos, H. Kim, G. Christiansen and J. Majumder, “A mesoscopic model for passenger evacuation simulation in a virtual ship environment and performance-based evaluation”, Proceedings of Conference on Pedestrian and Evacuation Dynamics, Germany, 2001.
