# Reliability Optimization Design of Diesel Engine System Based on the GO Method
## 1 Introduction
It is an inductive analysis method that investigates all possible failure modes of each product in the system and all possible impacts on the system and classifies each failure mode according to its severity and occurrence probability. FEMCA is a bottom-up inductive analysis method. Regardless of many standards, it still has many deficiencies in restoring system capabilities, visual models, and quantitative calculations. The GO method is a system reliability analysis method oriented to mission success. Its basic idea is to directly translate the system schematic diagram, flow chart, or engineering diagram into a GO diagram model according to certain rules and then adopt the GO algorithm to perform GO operations based on the GO diagram model to obtain the reliability analysis results of the system. The GO method is particularly suitable for complex systems with multiple states, feedback, and dependencies. Moreover, its scalability is extremely strong, and it can be combined with other technologies to improve and solve various engineering practical problems. Therefore, compared with common system reliability analysis methods, such as reliability block diagram, fault tree, and FMECA, the GO method is more suitable for reliability analysis of complex systems such as diesel engines. The GO method was initially proposed by the U.S. military and applied to the reliability analysis of weapon systems. Later, it was employed in transportation, water supply system, nuclear industry system, power system, and other fields [10]. In recent years, many Chinese researchers have further improved the GO method. For example, [PERSON] et al. presented the shared signal correction algorithm and the shared signal accurate algorithm of the GO method. The reliability analysis results of the GO method in many engineering systems verified that the results obtained by the accurate algorithm of the shared signal were closer to engineering practice. [PERSON], [PERSON], et al. proposed the GO method reliability analysis for a repairable system with multiple failure modes under the consideration of the maintenance correlation of redundant structure and the multiple failure modes units of the system to analyze the reliability of hydraulic fuel supply system of vehicle integrated transmission device [11; 12; 13]. On the basis of the 17 standard operators, [PERSON] combined Type 18A and Type 20 operators to describe the backup structure composed of multiple input devices [14] and defined Type 19 operators to describe the components with fluctuating performance in a stable system [15]. In the study, the concept of auxiliary operators was first proposed. Type 15B and Type 22 operators were combined to illustrate the multifunctional element in the multifunctional complex system [16]. The Type 21 operator was defined to reflect the input signal unit with multifunctional mode and multiple working conditions. The Type 23 logical operator was defined to indicate the logical relationship output by the multifunctional mode system. The Type 25 operator was defined to explain the conversion of scalar signal flow and vector signal flow [15]. The Type 24 operator was created to describe the multi-input closed-loop feedback link, which broke the restriction that the GO method cannot model the closed-loop system for a long time [17; 18]. [PERSON] [19] et al. proposed a Type 24B operator to describe the multi-closed-loop feedback link. Given the main challenges currently faced by the reliability optimization design of the engine system, the GO method, which can better reflect the actual structure of the product, is employed in this paper to model and analyze the reliability of a V-type diesel engine. Its unit reliability interval optimization design is performed under minimum resource usage, large reliability, and robust distribution results. In addition, a three-level optimization design model of system-function-unit considering functional differences is constructed following the characteristics of the diesel engine.