Kwang-Phil Park

Development of a simulation framework and applications to new production processes in shipyards

Recently, a floating crane is frequently used for the block lifting, transportation, turn-over, and assembly processes in waves. For these production processes, it is important to detect collision in advance between assembly blocks or the block and the other facilities like the wire rope and the barge which are carrying the block. The tension of the wire rope also needs to be calculated to check that the maximum value is less than the safety criteria. In this paper, a mathematical model is constructed based on multibody system dynamics considering the external forces such as the hydrostatic, hydrodynamic, wind force, etc. To observe the dynamic motions of the floating crane and the block, and to calculate the tension of the wire rope, the time and event simulations are performed by solving the mathematical model in the computer. For applying the simulations to the various production processes in shipyards, a simulation framework is developed. The simulation framework consists of a simulation kernel, application-specific modules, a simulation coordinator, development tools, and post-processing tools. The simulation kernel manages both DEVS (discrete event system specification) and DTSS (discrete time system specification) to deal with various simulation requests. The application-specific modules provide the functions used in application systems, such as dynamic analysis, collision detection, visualization, wire rope force calculation, hydrostatic force calculation and hydrodynamic force calculation. The simulation coordinator manages the data of the simulation kernel and the application-specific modules. The development tools provide a development process, a scenario manager, and a simulation model generator. The post-processing tools are used to report the simulation results. The examples of block lifting, transportation, turn-over, and assembly simulations are developed based on the framework to show that the framework is useful for the simulations of the production processes using one or more floating cranes.

Validation of advanced evacuation analysis on passenger ships using experimental scenario and data of full-scale evacuation

SIMPEV is one of the advanced evacuation software on the passenger ship.SIMPEV is applied to two validation datasets given by real evacuation experiments.SIMPEV satisfies the acceptance criteria for each datasets.SIMPEV gives better or almost equal results compared with other software. Evacuation analysis, which calculates the total evacuation time should be fulfilled for all passenger ships. One of the ways to calculate evacuation time is to use the computer simulation, which models various effects of human behaviors in an emergency situation. In the previous research, SIMPEV (SIMulation system for Passenger EVacuation) was developed for the evacuation analysis based on the latest human behavior algorithms. It has already showed that SIMPEV basically satisfied the eleven test cases suggested in International Maritime Organization (IMO) Maritime Safety Committee (MSC)s Circulation 1238. The main focus of this paper is the validation of SIMPEV by using SAFEGUARD Validation Data Set 1 and 2, which performed real evacuation trials in two full-scale ships to compare simulation data with experimental data. Total evacuation time is computed by SIMPEV based on the validation data sets such as drawings, initial distributions and end locations. The results from 50 times simulation are analyzed to be compared with the experimental data in the statistical methods. From the results, it is found that SIMPEV satisfies the acceptance criteria for each of data sets. Furthermore, the results show a close similarity to those of the other simulation programs.

Achieving Data Interoperability of Communication Interfaces for Combat System Engineering

System of systems (SoS) engineering ensures that subsystems successfully interoperate with one another via a physical network along with the designed interface specifications. The twofold challenge that motivated the authors is regarding the achievement of the interoperability for an SoS-based combat system as follows: 1) the validation of the interface specifications against the specified requirements at the system-design phase and 2) the verification of the subsystems against the interface specifications at the system-integration phase. To this end, an interoperability validation and verification toolset (IVVT) consisting of the following three components was developed: signal distributor, message collector, and message analyzer. The signal distributor captures the signal data in the middle of the existing communication interfaces, the message collector stores the signals in the form of distinguishable messages, and the message analyzer evaluates the messages by comparing the designed interface specifications that cover the communication syntax and semantics. For the experimentations, the developed IVVT was utilized for the combat systems of real submarines that have been domestically targeted for a renovation project. The objective of the experiments is the validation of the overall designed interface specifications before the development of the subsystems. The empirical results show that 12 fault cases were found in the specifications, some of which are extremely critical; therefore, a preferential validation of the specifications could prevent the incompatibilities between the subsystems during the combat system integration. In a future work, the authors will employ the IVVT for a verification of the developed subsystems to be integrated depending on the validity of the interface specifications.

The flexible multibody dynamics of a floating offshore wind turbine in marine operations

ABSTRACT In this paper, a dynamic response analysis of a floating offshore wind turbine is performed during the rotor rotation under wind and wave loads after the turbine was installed on a floating platform. The floating offshore wind turbine is modelled as a system that consists of the floating platform, a tower, a nacelle, a hub, and three blades. Flexible multibody dynamics is employed in constructing the equations dealing with motion for the floating offshore wind turbine in the dynamic response analysis. The tower and the blades are constructed as flexible bodies by using the three-dimensional beam element. The external forces acting on the floating platform included the hydrostatic force, the hydrodynamic force, and the mooring force. Then, aerodynamic force was calculated based on the blade element momentum theory, and was applied to the blades. Using the wave and wind conditions that are generally required to operate a 5-MW offshore wind turbine, a numerical simulation was performed to determine the dynamic response of the floating offshore wind turbine, and the results are compared with the calculated dynamic response and stress based on a wind turbine analysis code that is open to the public.

Interface Data Modeling to Detect and Diagnose Intersystem Faults for Designing and Integrating System of Systems

In system of systems engineering, system integrators are in charge of compatible and reliable interfaces between subsystems. This study explains a systematic solution to identify and diagnose interface faults during designing and integrating systems of systems. Because the systems targeted in this study are real underwater vessels, we first have anatomized 188 interface data transferred between 22 subsystems of them. Based on this, two interface data models are proposed, which include data sets regarding messages and inner fields and transition and decision functions for them. Specifically, a structure model at the message level evaluates how inner fields belong to a message, and a logic model at the field level assesses how each field is interpreted and if the interpreted value is understandable. The software that supports the modeling is implemented using the following concepts: (1) a model-view-viewmodel pattern for overall software design and (2) a computer network for representing sequential properties of field interpretations. The proposed modeling and software facilitate diagnostic decisions by checking the consistency between interface protocols and obtained real data. As a practical use, the proposed work was applied to an underwater shipbuilding project. Within 10 interfaces, 14 fault cases were identified and diagnosed. They were gradually resolved during the system design and integration phases, which formed the basis of successful submarine construction.