## 5 Conclusions  
This study developed a predictive model for the dynamic positioning motion simulation of a vessel with four hulls. The hydrodynamic coefficients were obtained through a series of oblique tank tests and static turning tests using a 1/3 scale model, and the propeller's performance curve was derived from the Propeller Open Test. A simple wind force model was established based on the wind load test results of a single hull and the superstructure. Validation navigation tests were carried out in calm water, as well as windy sea areas. The calculation margin of error was kept within 2 m by the model created under the quasi-static assumption. Such results are considered satisfactory for systems with multiple error sources, including position recorders, compasses, and mechanical component delays. Specific findings obtained from this study are summarized below.  
* The Quadmaran vessel can be dynamically positioned and kept within 2 m of the target point, under wind speeds not exceeding 5 m/s, as observed in actual sea tests.
* The drift angle of the vessel had a significant effect on the water loads generated from the parallel motion. The parallel motion with a drift angle in the range of 20-45 degrees was likely to rapidly fluctuate the fluid force due to the unique hull shape. The moment generated from the static yawing motion was almost proportional to the square of the yaw rate. The thrust coefficient (\(K_{T}\)) decreased as the advance ratio (\(J\)) increased when rotating forward, and was almost constant when reversing.
* The wind loads calculation model, which was established based on the database of wind load tests on a single hull and the superstructure, was found to be reliable in predicting the motion during DP of the vessel. The initial heading angle had some significance to the path of trajectory of the Quadmaran vessel in DP mode, but did not affect the prediction model if the loads were accurately assessed.
* The fluid force coefficient, assuming a quasi-static hull motion, was sufficiently accurate to predict the motion in DP mode. Therefore, the developed computational model can be useful to understand the motion characteristics of similar multi-hull vessels.  
Figure 24: Comparison of experiment and simulation at P10.  
**Author Contributions:** Conceptualization, M.J. and Y.N.; methodology, M.J. and Y.N.; software, M.J.; validation, M.J. and Y.N.; formal analysis, M.J.; investigation, M.J.; resources, Y.N.; data curation, M.J.; writing--original draft preparation, M.J. and S.S.; writing--review and editing, M.J., S.S. and Y.N.; visualization, M.J.; supervision, Y.N.; project administration, Y.N.; funding acquisition, Y.N. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This work was supported by the Ministry of Economy, Trade and Industry (METI) and Monozukuri R&D Support Grant Program for SMEs.  
**Data Availability Statement:** The data presented in this study are available on request from the corresponding author.  
**Acknowledgments:** Authors would like to express their deep gratitude to our Visiting Researchers [PERSON] and [PERSON] from Fractary Co., Ltd. Special thanks are extended to [PERSON], [PERSON], [PERSON], [PERSON], [PERSON] and [PERSON] from Nippon Kaiko Co., Ltd who supported our experiments.  
**Conflicts of Interest:** The authors declare no conflict of interest.