A reliability modeling method based on symbolic directed graph

Abstract

The present invention provides a reliability modeling method based on a symbolic directed graph, comprising the following steps: S1, determining the product functional medium transmission path; S2: according to the determined functional medium transmission path, clarifying each node on the path, that is, the product component unit; S3: forming a preliminary functional path network; S4: clarifying the medium input requirements of the unit node; S5: clarifying the function of the unit node; S6: clarifying the output requirements of the medium; S7: clarifying the relationship matrix between the unit node function and the output requirements; S8: establishing a symbolic directed graph of the system to form a reliability model. The present invention uses graph theory to introduce the symbolic directed graph into the reliability modeling method, abstracts the functional schematic diagram of the system, represents the physical unit through nodes, and abstractly represents the function, input requirements, output requirements, etc. of the physical unit through graph theory, which has the characteristics of being unified with the product solution design, intuitive physical meaning, and detailed and complete information description.

Description

Technical Field

[0001] The invention relates to the field of aerospace technology, and in particular to a reliability modeling method based on a symbolic directed graph. Background Art

[0002] Reliability modeling is the basis for reliability work of launch vehicles, etc. Reliability model is a description of the reliability and fault logic relationship between products and their components. At present, the reliability block diagram (RBD) modeling method is widely used in my country's launch vehicles. Its main standard is GJB 813 "Establishment of Reliability Model and Reliability Prediction". GJB 813 has top-level requirements for the establishment of reliability model functions, environmental conditions, working hours, parameter constraints, etc., but does not reflect the functional impact relationship of the medium.

[0003] The reliability modeling method provided by GJB 813 is a description of the functional relationship between the system components, but does not describe the operating status of the functional medium, and does not reflect the composite status of the unit products and the functional medium when the system is running. As a result, the role of the reliability model in reliability work is greatly reduced, which is mainly reflected in the following aspects:

[0004] First, the reliability block diagram cannot reflect the quantitative index requirements. The reliability block diagram abstracts the product components and regards the functions after reliability evaluation as a function box, which is too abstract;

[0005] Second, the reliability block diagram oversimplifies the description of the product function mechanism, mainly considering whether the functions are redundant, and cannot give a good description of the complex relationship between functions;

[0006] 3. It is not conducive to fault analysis. The reliability block diagram model cannot reflect the impact relationship between the fault modes of products, and cannot reflect the impact of a certain fault mode on the system. When conducting fault analysis and fault diagnosis, a new model needs to be re-established, resulting in a disconnect between the reliability model and fault analysis.

[0007] Fourth, it is not conducive to the continuous improvement of the system. Since the reliability model is too simplified, more information cannot be reflected in the model. In the process of system design optimization and improvement, the reliability block diagram model cannot play a role, resulting in the disconnection between reliability work and product design work, and the "two-skin" phenomenon is serious. Summary of the invention

[0008] The purpose of the present invention is to provide a reliability modeling method based on a signed directed graph to solve the above technical problems.

[0009] The technical solution of the present invention is to provide a reliability modeling method based on a symbolic directed graph, comprising the following steps:

[0010] S1. Determine the product function medium transmission path;

[0011] S2: According to the functional medium transmission path determined in step S1, each node on the path, i.e., the product component unit, is identified;

[0012] S3: Formation of a preliminary functional pathway network;

[0013] S4: Clarify the medium input requirements of the unit nodes;

[0014] S5: clarify the function of unit nodes;

[0015] S6: Clarify the output requirements of the media;

[0016] S7: Clarify the relationship matrix between unit node functions and output requirements;

[0017] S8: Establish a symbolic directed graph of the system to form a reliability model.

[0018] The reliability modeling method based on symbolic directed graph provided by the present invention utilizes graph theory to introduce symbolic directed graph into the reliability modeling method, abstracts the functional schematic diagram of the system, represents the physical unit through nodes, and represents the function, input requirement, output requirement, etc. of the physical unit through graph theory abstraction. It has the characteristics of being unified with product solution design, intuitive physical meaning, detailed and complete information description, etc.; it is convenient to describe the functional relationship and the coupling relationship between the function and the medium; it is convenient to carry out work such as fault analysis and continuous product improvement. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The invention will be further described below in conjunction with the accompanying drawings:

[0020] Figure 1 It is a schematic diagram of reliability modeling in an optional embodiment of the present invention. DETAILED DESCRIPTION

[0021] The reliability modeling method based on a symbolic directed graph proposed by the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer according to the following description and claims. It should be noted that the accompanying drawings are all in a very simplified form and use inaccurate ratios, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0022] Please refer to Figure 1 Taking the safety valve of a launch vehicle as an example, the present invention provides a reliability modeling method based on a symbolic directed graph, comprising the following steps:

[0023] S1: Determine the product function media transmission path;

[0024] According to the functional principle of the system, the functional medium transmission path of the product is determined. Taking the safety valve as an example, the pilot safety valve selected in this embodiment first analyzes the path of gas as the functional medium. The gas transmission path is 1: from the storage tank to the main valve cavity; 2: from the storage tank, valve seat, pilot valve, and main valve back pressure chamber. Therefore, the gas transmission path is the above two. In the above two gas paths, there is also a force transmission path, which controls the action of the valve together with the pressure generated by the gas. The force transmission path of the control valve is the fixed nut, valve seat, spring, spring seat, valve disc, and pull rod; the force transmission path of the main valve is the fixed nut, spring, bellows assembly, and valve disc.

[0025] S2: According to the functional medium transmission path determined in step S1, each node on the path, i.e., the product component unit, is identified;

[0026] On the basis of step S1, all node products on the gas path and force transmission path are clarified and refined. On gas transmission path 1, node products include housing and piston; on gas transmission path 2, node products include: housing, straight pipe joint, gasket, pipeline, pilot valve disc, valve seat, back pressure chamber. On the force transmission path of the pilot valve, node products include: pilot valve housing, hexagonal nut, adjustment screw, spring disc, reference spring, pressure pad, pull rod, pull sleeve, and pilot valve disc.

[0027] S3: Formation of a preliminary functional pathway network;

[0028] After completing the above S1 and S2 tasks, a preliminary network model is formed using a symbolic directed graph.

[0029] S4: Clarify the medium input requirements of the unit nodes;

[0030] Based on the preliminary network model of S3, the media input requirements of each node are clarified.

[0031] S5: clarify the function of unit nodes;

[0032] Based on the preliminary network model of S3, the function of each node is clarified.

[0033] S6: Clarify the output requirements of the media;

[0034] Based on the preliminary network model of S3, the functional medium output requirements of each node are clarified.

[0035] S7: Clarify the relationship matrix between unit node functions and output requirements;

[0036] Establish a relationship matrix between node functions and functional medium output requirements to clarify how product functions will affect the output characteristics of the functional medium.

[0037] S8: Establish a symbolic directed graph of the system to form a reliability model.

[0038] After completing the work of S4, S5, S6, and S7, integrate them into the preliminary network diagram formed by S3 to form a reliability model of the system.

[0039] In summary, the present invention utilizes the symbolic directed graph of graph theory to abstract the functional principle of the product through nodes, and integrates the product's function, medium, and the influence relationship between function and medium into a system topology diagram, which has intuitive physical meaning and is easy to understand and implement in engineering. It is convenient for the high degree of unification of reliability work and product design work, and is convenient for fault analysis and diagnosis, which greatly improves the status of reliability models in reliability work.

[0040] The contents not described in detail in this specification belong to the prior art known to those skilled in the art. It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention.

Claims

1. A reliability modeling method based on a symbolic directed graph, characterized in that: The steps include: S1. Determine the product function medium transmission path; S2: According to the functional medium transmission path determined in step S1, each node on the path, i.e., the product component unit, is identified; S3: Formation of a preliminary functional pathway network; S4: Clarify the medium input requirements of the unit nodes; S5: clarify the function of unit nodes; S6: Clarify the output requirements of the media; S7: Define the relationship matrix between unit node functions and output requirements; S8: Establish a symbolic directed graph of the system to form a reliability model; In step S1, the product is a pilot-operated safety valve; the product functional medium transmission path is: 1) from the tank to the main valve cavity; 2) from the tank, valve seat, pilot valve, and main valve back pressure cavity; In the two product functional medium transmission paths, there is also a force transmission path, which controls the action of the valve together with the pressure generated by the gas. The force transmission path of the control valve is: fixing nut, valve seat, spring, spring seat, valve disc, pull rod; the force transmission path of the main valve is: fixing nut, spring, bellows assembly, valve disc; In step S2, on the gas transmission path 1), the node products include a shell and a piston; on the gas transmission path 2), the node products include: a shell, a straight pipe joint, a gasket, a pipeline, a command valve disc, a valve seat, and a back pressure chamber; On the force transmission path of the pilot valve, the node products include: pilot valve housing, hexagonal nut, adjusting screw, spring disk, reference spring, pressure pad, pull rod, pull sleeve, and command valve disc.

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