Abstract: A new method of virtual ship assembly modeling which integrates ship three-dimensional design and ship construction planning was described in this paper. A workflow model of simulation modeling based on the virtual ship assembly process was also established; furthermore, a method of information transformation between the ship three-dimensional design and ship construction plan was formulated. To meet the requirements of information sharing between different systems in the ship virtual assembly, a simulation database was created by using the software engineering design method and the relational data model. With the application of this database, the information of ship three-dimensional design, construction planning, and virtual assembly can be integrated into one system. Subsequently, this new method was applied as a tool to simulate the virtual assembly of a ship, and the results guarantee its rationality and reliability.

Keywords: ship virtual assembly; simulation modeling; workflow model; simulation database; three-dimensional design; construction planning

Article ID: 1671-9433(2011)04-0447-08

1 Introduction

Ship construction requires a large and complex engineering system which involves the cooperation of the various types of work within limited space and resources. It is characterized by high intensity of technology, capital, and labor. Virtual manufacturing (VM) is an integrated approach which preliminarily simulates the ship construction process and accurately forecasts the performance index (Kim et al., 2003). Virtual ship assembly is considered to be one of the most significant applications in virtual ship manufacturing. It is a computer-based design process which coordinates ship components, including solid modeling, assembly,  and checking of interference. With the application of the virtual assembly technology, designers can confirm the validity of the ship assembly design and operation mode (Mclean and Shao, 2001). If there are some problems in the assembly process, designers can discover them in advance and solve them by modifying the model or changing the assembly sequence, and the assembly process can be visualized for the engineers and technicians. After the assembly, the system can formulate the necessary information for the subsequent analysis of the assembly, such as the appraisal report and video recorder.

The establishment of the ship simulation model is  important in virtual ship assembly. Besides the geometric information of the assembly solid, the simulation model can also include other   information   such  as   the  assembly   path,  assembly

sequence, assembly time, and assembly node. Furthermore, to confirm that the simulation results are correct and valid, the information of the simulation model should be strictly consistent with that of the ship design and engineering plan. Ship construction is such a complicated engineering task that it is difficult for designers to establish the simulation model in an efficient way. A number of studies have been done on simulation of the modeling of virtual ship assembly. Lee et al. (1997) adopted an object-oriented method and simulated the lifting process in the dockyard, but the  simulation effectiveness was affected by the absence of visual modeling of the lifting process. Xu and Jin (2007) proposed a timed transforming Petri net model, and integrated various subnets into one model by applying the sharing synthesis method. Though the time information and the sequence of lifting assembly were displayed, it still could not visualize the simulation model. Liu et al. (2004) suggested that the CAD modeling should be transformed into the virtual assembly model in order to provide the geometric modeling and the visual modeling. This method can enhance the efficiency of solid geometric modeling, which contains too much work from the virtual ship assembly. However, this suggestion did not integrate the virtual assembly modeling with the construction planning system. From all the  research mentioned above a conclusion can be reached that, although some research has been done to simulate virtual ship assembly modeling, there are still some shortages in the existing modeling methods. First of all, the simulation modeling can not be integrated with the ship design and planning system; therefore the design information and the planning information can not be used repeatedly. Moreover, maintaining   the   consistency   of   the   design   information,