## 1 Introduction  
As computer performance has increased, simulations that replicate an actual system are used in various industrial fields, including the marine industry, to evaluate the dynamic characteristics of a product prior to its fabrication. Such technology is known as computer-aided engineering (CAE). Utilization of such technology in actual production sites has advantages in terms of cost savings and a shorter development period. Recent studies: compensator was designed by [PERSON] that uses 2 gas DSC cylinders, which was studied through numerical analysis to confirm damping factor [1]. [PERSON] simulated ship and process in ship yard using multi body dynamcis analysis [2]. [PERSON] optimized AHC system of hoisting rig using the dynamics analysis [3]. [PERSON] verified mechanical semi active compensation system using oil pressure analysis [4]. Same as the researches applied through computer simulation, have various forms in the design step, because offshore plant cost a lot in development.  
Because of the complexity of parts organization, analysis technology and software for multi-body dynamics are used for system analysis, allowing the identification of design errors. This is done by determining the behaviors of parts resulting from the load or deformation, not inside a part, but generated by its movement and transferred to other parts, and by assessing interference between parts. Compared with previous manual parametric modeling, multi-body dynamics analysis technology, when used with an existing compatible design program, facilitates modeling and analysis of complicated machine systems [5; 6; 7; 8; 9]. This technology works by dividing the components of the machine system into body, joint, and force elements, and by applying the mechanical and dynamic constraints distinctive to each component to organize the system equation of motion.  
In this study, when the compensation system for an offshore plant is designed, a 1:5 scale compensator was manufactured and tested for vibration. After the oil pressure system was modeled, the proper AHC control value was known through simulation. DSC and AHC cylinder speed were detected through multi body dynamics analysis. Therefore, results were expected to get correct design value through various researches and to economize the manufacturing cost and time.  
A heave compensation system comprises a drill string compensator (DSC) and an active heave compensator (AHC). The DSC reduces the disturbance caused by the heave motion of the platform applied to the heavy object suspended from the hosting system, and attenuates disturbance by up to \(\sim\)90%. The AHC is added to the DSC, and thus reduces disturbance of heave motion by \(\sim\)5% and applies control force to the part supporting the heavy object. It can also attenuate the disturbance of heave motion by applying control force in a positive or negative direction. In general, an oil pressure system is used to apply the control force [10].  
Unlike drilling work carried out on the ground, in drilling work carried out in the marine environment, the key is to minimize the influence of the external force of fluid applied to the hull. Accordingly, in this study, a dynamics analysis model and a structural analysis model are proposed to determine dynamic performance and safety for the design of a heave compensator system for marine plants.