## 1 Introduction
The secondary energy conversion system of a movable object type wave power generator is typically a mechanical system type that transmits energy transmitted from the motion of a floating body in rotational motion using various gear systems, pulleys, and gearboxes. The wave power generator applying Salter's duck type WEC is a representative movable object type wave power generator to which the secondary energy conversion mechanical system is applied [15]. In addition, there is a wave power generator to which a secondary energy conversion hydraulic system is attached that operates a hydraulic pump and motor by generating a pressure difference of a fluid through a hydraulic cylinder, or operates a turbine with a flow of fluid using energy transmitted from the motion of a floating body. Representatively, the generators that apply wavestar type WEC belong to this category [16]. In addition, there are hybrid generators that use both secondary energy conversion mechanical and hydraulic systems in combination. Many studies have previously been conducted on the efficiency analysis of these secondary energy conversion systems. With the theme of the secondary energy conversion mechanical system, a system that can amplify or reduce the final efficiency by combining the mechanism of the gear system was constructed [17]. The system consists of 12 sets of parallel gears that transmit torque to a sun gear through a level gear, one-way gear. A system using a double rack and pinion gear system and a shaft were applied. This system converts the horizontal reciprocating motion of the wave into the reciprocating motion of the arm and rack gear and converts it into the rotational motion of the pinion gear [18]. In addition, a multi-level secondary energy conversion system was developed that converts bidirectional rotational motion into unidirectional motion using bearings and level gears, and then applies a power transmission system to increase the rotational speed [19]. A complex system was constructed in which the toothed gear rack attached to the buoy rotates the pinion gear, and the other pinion gear rotates in the opposite direction to generate power. This system is attached with a revolution per minute (RPM) multiplier to improve the RPM of the output shaft [20]. For pulleys, not gears, a bidirectional driven float-type wave power generator with six pulleys and two ratchet wheels was designed [21]. As the theme of the secondary energy conversion hydraulic system, a power take-off (PTO) system using a discrete displacement cylinder was constructed. It transfers energy by changing the flow of oil or gas and converts the flow energy into rotational energy using a hydraulic motor [22]. Additionally, a hydraulic pump with secondary control hydrostatic transmission was applied. This system produces pulley torque using buoy and counterweight, increases the pulley torque produced using the gearbox, and uses the increased torque for the hydraulic pump and motor [23]. As a result of previous research analysis, various types of secondary energy conversion systems can be applied. However, contrary to the diversity of the configuration of the secondary energy conversion system, it is difficult to find a study for the conceptual design of the system through system analysis and generalization. Since the power generation performance of the system varies depending on the form of the secondary energy conversion system, the reliability assessment of the system in the conceptual design stage is a very important issue. For this, it is necessary to generalize the power transmission form of the secondary energy conversion system by assessing the reliability of the system using appro  
Figure 2: Step-by-step process of energy conversion through movable object type wave power generator. priate methods. Regarding the reliability assessment of the engineering structure, various techniques considering uncertainty have been actively studied [24; 25; 26; 27], and studies related to reliability assessment of wave power generator systems have been conducted [28; 29].