A Model-Based Hierarchical Fault Analysis Method for Complex Manned Space Systems

Abstract

The present invention relates to a model-based hierarchical fault analysis method for complex manned space systems. While using SysML for the design and analysis of complex manned space systems, potential faults are identified through the decomposition of the hierarchical system functions or structures, and the fault mode analysis of each layer of the system is carried out based on the model. Then, through the iteration of the models between the layers, the fault analysis of the entire system is completed. The present invention provides a new approach for fault identification in the model-based design and demonstration of future manned space engineering and other complex systems, which is beneficial to the traceability, control, and future system safety and reliability analysis of complex manned space system faults, and guides the system design, and can meet the needs of future model-based system engineering development.

Description

Technical Field

[0001] The present invention relates to the technical field of safety and reliability analysis of manned spaceflight complex systems, and particularly relates to a model-based hierarchical fault analysis method for manned spaceflight complex systems. Background Art

[0002] The manned spaceflight project involves the coordination of multiple systems such as the launch vehicle system, the manned spacecraft system, the launch site system, the TT&C communication system, the astronaut system, and the landing site system, and has the characteristics of a typical complex system. Manned spaceflight takes ensuring the safety of astronauts as the highest criterion. Therefore, the safety and reliability analysis of the system is a very important link in the manned spaceflight project. The fault analysis of the system is the basis for carrying out safety and reliability analysis. Traditional fault analysis methods include two categories: one is the top-down analysis idea. The most classic one is the main logic analysis method, which assumes the failure of the top-level system and analyzes the causes leading to the failure along the failure mode downward; the other is the bottom-up analysis idea, such as the failure mode and effects analysis (FMEA) method, which assumes the failure of a certain function at the bottom layer and analyzes other failure modes and consequences further caused by this failure. In recent years, in order to solve the problems of complex system design, management, and demonstration, the model-based systems engineering (MBSE) method has emerged, which models the paper-based documents and can realize the control of the entire life cycle of the system, and is also applicable to the manned spaceflight project. However, the manned spaceflight complex system faces the following two problems: one is that due to the huge system architecture and complex relationships of the complex system, it is difficult to fully identify all the faults of the system during the system design and demonstration stages, and the change of system design will also lead to the emergence of new risk sources; the other is that the separation of fault analysis and system design leads to the prominent problem of "two skins" in safety and reliability analysis. Therefore, the safety and reliability analysis of manned spaceflight based on traditional methods has always faced great challenges.

[0003] Integrating fault analysis into model-based system design and demonstration can effectively solve the current problems of safety and reliability analysis of complex systems. The MBSE methodology provides basic support for system modeling, but there are still deficiencies in the current integration with fault analysis. Many industrial departments also first model the system through SysML, and then export the model to a third-party software for fault analysis. Such a mode still has deficiencies in analysis efficiency and it is also difficult to guarantee the homology of the model. Therefore, it is very necessary to use the model-based hierarchical fault analysis method for complex systems to break through the barriers among the MBSE methodology, traditional fault analysis methods, and the design of manned spaceflight complex systems, and comprehensively identify potential faults and risks. Summary of the Invention

[0004] The object of the present invention is to provide a model-based hierarchical fault analysis method for complex manned spaceflight systems, which integrates the top-down and bottom-up fault mode analysis methods in the hierarchical decomposition of manned spaceflight systems, and combines with the MBSE methodology to model the analysis process, solving the problems of fault identification, analysis and traceability of complex manned spaceflight systems in the design and demonstration stages.

[0005] The present invention provides a model-based hierarchical fault analysis method for complex manned spaceflight systems. While using SysML for the design and analysis of complex manned spaceflight systems, through the decomposition of hierarchical system functions or structures, potential faults are identified, and the fault mode analysis of each layer of the system is carried out based on the model. Then, through the iteration of the models between layers, the fault analysis of the entire system is completed. Among them, the models that can be interacted between the engineering general body and subsystems are the bottommost models of the engineering general body, that is, the topmost models of subsystems, including fault models. The fault analysis method includes:

[0006] Step 1, each system uses the risk assessment and modeling language published by object-oriented organization to establish a basic model for defining manned spaceflight faults through SysML, and based on this, defines fault modes, establishes a fault mode library, constructs FMEA entries, and associates fault response strategies.

[0007] Step 2, the engineering general body only distributes the bottommost models to the corresponding subsystems, and the subsystems also only transfer the topmost models to the engineering general body. Each system uses the hierarchical fault analysis method through the access of the interactable fault models to realize the iteration of fault analysis and improve the fault models of the entire system.

[0008] Further, the hierarchical fault analysis method in Step 2 includes the following steps:

[0009] (1) Decompose the functions or structures of the system in a top-down manner to form a model for the forward design of the system.

[0010] (2) Assume that the highest-level function or structure in the current-level system fails, and refer to the system decomposition mode. Adopt the main logic analysis method to find the reasons for the failure of the upper-level function or structure, that is, the failure modes of the lower-level systems.

[0011] (3) Based on the decomposition of the top-level function or structure to the bottommost function or structure, directly identify the bottommost failure modes.

[0012] (4) Adopt a bottom-up manner, and use the FMEA method to recursively push up layer by layer on the basis of the bottom-layer fault modes to obtain the upper-layer failure modes and consequence states caused by them, and establish FMEA entries.

[0013] (5) If step (3) finds a different fault mode from the one identified in step (2), then the original bottom-level failure mode library is expanded, and the different fault mode is used as the top-level event of the main logic analysis, and a top-down analysis is performed to find out whether there is a new lower-level fault mode. If there is, the fault mode library of this layer is further expanded, and the new fault analysis is reviewed using the FMEA method and FMEA items are established;

[0014] (6) The upper-level system divides the system into the finest granularity of its concern within this level, and decomposes the subsystem and the corresponding failure mode into each subsystem;

[0015] (7) Each subsystem checks whether there is a new top-level failure mode of the system at the same level. If so, repeat steps (2) and (4). If a new failure mode of the upper-level system is obtained, it is fed back to the upper level. After receiving the new failure mode, the upper level system checks whether a new bottom-level failure mode appears. If so, repeat step (4).

[0016] (8) Repeat steps (5) to (7) until a consensus is reached among the systems and no new failure modes appear.

[0017] Through the above scheme, through the model-based hierarchical fault analysis method of manned space complex systems, combined with the development mode of manned space engineering, the main logic analysis method and the FMEA method are combined, which is conducive to the identification of faults in the design stage of future manned space complex systems; at the same time, in order to adapt to the design of future model-based manned space engineering, the fault analysis is modeled and hierarchical modeling is carried out, which is conducive to the tracing, control and analysis of future system safety and reliability of manned space complex systems, and guides the design of the system.

[0018] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The present invention is a flowchart of a model-based hierarchical fault analysis method for complex manned spaceflight systems. DETAILED DESCRIPTION

[0020] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0021] This embodiment provides a model-based hierarchical fault analysis method for complex manned space systems. While using SysML to perform design analysis on complex manned space systems, potential faults are identified through hierarchical system function or structure decomposition. Failure mode analysis is then conducted for each system layer based on the model. Failure analysis of the entire system is then completed through iteration of models between layers. (Each system performs fault analysis based on its own characteristics, and fault information is transmitted between systems through model interaction.) The interactive model between the overall project and its subsystems is the bottom-level model of the overall project, i.e., the top-level model of the subsystem, including the fault model. The fault analysis method includes:

[0022] Step 1: Each system uses SysML, a risk assessment and modeling language published by an object-oriented organization, to establish a basic model for defining manned spaceflight failures. Based on this model, failure modes are defined, a failure mode library is established, FMEA items are constructed, and failure response strategies are associated.

[0023] In step 2, the overall project only distributes the bottom-level model to the corresponding subsystem, and the subsystem only passes the top-level model to the overall project. Each system uses a hierarchical fault analysis method through access to the interactive fault model to implement fault analysis iteration and improve the fault model of the entire system.

[0024] In this embodiment, the hierarchical fault analysis method in step 2 includes the following steps:

[0025] (1) Decompose the system's functions or structures from top to bottom to form a model for system forward design;

[0026] (2) Assuming that the highest level function or structure in the system fails, refer to the system decomposition model and adopt the main logic analysis method to find the cause of the upper level function or structure failure, that is, the failure mode of the lower level system;

[0027] (3) Directly identify the lowest-level failure mode by decomposing the top-level function or structure into the lowest-level function or structure;

[0028] (4) Using a bottom-to-top approach, the FMEA method is used to recursively work upwards layer by layer based on the underlying failure mode to obtain the upper-level failure mode and consequence state caused by it, and to establish FMEA items;

[0029] (5) If step (3) finds a different fault mode from the one identified in step (2), then the original bottom-level failure mode library is expanded, and the different fault mode is used as the top-level event of the main logic analysis, and a top-down analysis is performed to find out whether there is a new lower-level fault mode. If there is, the fault mode library of this layer is further expanded, and the new fault analysis is reviewed using the FMEA method and FMEA items are established;

[0030] (6) The superior system divides the system within the current level into the finest granularity it concerns, and decomposes the subsystem and the corresponding failure mode into each subsystem;

[0031] (7) Each subsystem checks whether there is a new top-level failure mode of the current-level system. If so, repeat steps (2) and (4). If a new failure mode of the superior system is obtained again, feedback it to the superior; after receiving it, the superior system checks whether there is a new bottom-level failure mode. If so, repeat step (4);

[0032] (8) Repeat steps (5) to (7) until a consensus is reached among the systems and no new failure modes appear.

[0033] This model-based hierarchical fault analysis method for complex manned space systems integrates the main logic analysis method and the failure mode and its effects analysis (FMEA) method while using SysML for the design of complex manned space systems. By establishing a fault model of the system and comprehensively using the above two methods to carry out iterative hierarchical fault analysis within and between systems, it realizes the identification of potential fault modes of complex manned space systems and the association of corresponding fault measures, providing a new approach for fault identification in the future manned space engineering and other complex systems in model-based design and demonstration. It is conducive to the traceability and control of faults in complex manned space systems and guides the design of the system, and can meet the needs of future model-based systems engineering development.

[0034] The following further elaborates on the present invention in detail:

[0035] The present invention mainly includes three parts:

[0036] (1) Hierarchical fault analysis method

[0037] Through long-term practice, the manned space engineering has formed a mature system system, including the project overall and each system (launch vehicle system, manned spacecraft system, launch site system, etc.). The clear system division and task assignment lay a good foundation for hierarchical fault analysis. The hierarchical fault analysis method is as Figure 1 shown, and its specific steps are as follows:

[0038] ①: Forward identification of faults based on main logic analysis. Within the scope concerned by the current system, decompose the function or structure of the system in a top-down manner according to its own working mode; adopt the main logic analysis method, assume the failure of the highest-level function or structure within the current-level system, and decompose layer by layer according to the system layering method to find the reasons for the failure of the upper-level function or structure, that is, the failure mode of the lower-level system.

[0039] ②: Reverse recursion of failure modes based on FMEA. Within the current system level, decompose the top-level functions or structures to the bottom level, and find the bottom-level failure modes through enumeration. Using a bottom-to-top approach, use the FMEA method to recurse upward layer by layer to obtain the upper-level failure modes and consequence states caused by them, and establish FMEA items. If a new upper-level failure mode is discovered, expand the original failure mode library.

[0040] ③: Iterative improvement of fault analysis within the current system. By conducting FMEA within the current system, if a fault mode different from the main logic analysis method is found, then use this different fault mode as the top-level event of the main logic analysis, and analyze from top to bottom to find whether there are new lower-level fault modes. If there are, further expand the fault mode library of this layer, and use the FMEA method to review the new fault analysis and establish FMEA items.

[0041] ④: Iterative improvement between systems. An interface is required between the overall project and the subsystems to transmit fault risks and associate failure mode logic. The superior system divides the system into the finest granularity it is concerned about within its own level and decomposes it into subsystems. Each subsystem further conducts fault analysis based on its own model based on the system function or structure and failure mode transmitted by the superior system. If a new fault mode of the superior system is obtained, it will be fed back to the superior, and the superior will further conduct fault analysis after receiving it; if a new fault mode of the subordinate system is obtained, it will be fed back to the subordinate system. Iterate in this way until a consensus is reached between the systems and no new fault modes appear.

[0042] (2) Modeling of fault analysis

[0043] The traditional document-based fault analysis is modeled based on the Model-Based Systems Engineering (MBSE) methodology, and a mapping from hierarchical fault analysis to a hierarchical fault model is established. This mainly includes the following parts:

[0044] ①: Establish a basic failure model corresponding to the forward design of manned space systems. Based on the risk assessment and modeling language published by the object-oriented organization, a basic model for defining manned space failures is established using SysML. This includes risk factors, failure modes, failure consequences, risk control measures (at the overall engineering level: escape and emergency life-saving measures; at the subsystem level: risk control design solutions such as system redundancy), and the relationships between these key factors.

[0045] ②: Analyze the fault mode using the main logic analysis method against the structural model or functional model generated by the forward decomposition of the system. Based on the basic fault model, model the identified fault mode through generalization to form a preliminary fault mode library for each layer of the system.

[0046] ③: Establish a model for FMEA items. Starting from the lowest-level failure mode identified by the current system, sort out the relationship between each layer of failure modes in the logical order of risk factors, failure modes, and failure consequences. The lower-level failure modes serve as the causes of the upper-level failure modes, and the failure of the top-level tasks serves as the failure consequences. For each low-level failure mode, use the SysML module definition diagram to establish an FMEA item, which includes its corresponding risk factors, failure modes, and failure consequences, thereby establishing a traceability relationship between failures at different levels. At the same time, according to the safety measures that each system is concerned about, the corresponding risk control measures to be implemented are incorporated into the FMEA items using the inclusion relationship, forming a traceability relationship with the corresponding failure mode.

[0047] (3) Hierarchical fault modeling method

[0048] In manned spaceflight projects, each system has a clear interface, and systems exchange relevant information only through these interfaces. Fault modeling must also adhere to this fundamental characteristic. In hierarchical fault modeling, the underlying functions or structures of the system at this level serve as the top layer of the lower-level systems. Therefore, the failure modes of the underlying systems at this level also serve as interfaces for fault analysis. During model-based system design, the upper-level system distributes the underlying functions or structures and corresponding failure mode models to the lower-level systems. The lower-level systems have read and write access to these models, while other models are encapsulated. Fault-related information analyzed by the lower-level systems is also transmitted to the upper-level systems. The completeness of the fault model for the entire system can be achieved simply through the interaction of the underlying fault models at each level.

[0049] The present invention utilizes the iterative process of main logic analysis and FMEA to analyze the failure of complex manned space systems, model them, establish a complete complex system failure transmission relationship, and associate the failure countermeasures of each system. In a specific embodiment, the method includes:

[0050] (1) After receiving the task of designing and demonstrating a manned space activity, the boundaries of the overall project and subsystems are defined based on the experience of traditional manned space engineering. At the overall project level, the overall task (for example, the successful implementation of a manned space mission) is functionally decomposed using SysML activity diagrams and module definition diagrams. Based on the complexity of the task and the way it is carried out, it can be decomposed into several layers, each layer containing all sub-functions that support the implementation of the upper layer functions, until the system boundary. At the subsystem level, the function of the system boundary is taken as the main function. Based on the working mode of this system, it is decomposed into several layers using activity diagrams, module definition diagrams, internal block diagrams, etc., until it meets the granularity of its design and manufacturing.

[0051] (2) Conduct a main logic analysis in the overall project and each subsystem, and establish a fault model. In each system, assume that the top-level function fails (for example, at the overall project level: a certain manned space mission fails, and the astronauts are injured; for the launch vehicle system: the spacecraft fails to be launched into orbit; for the manned spacecraft system: fails to complete tasks such as rendezvous and docking, orbiting the earth, etc.). Using the system decomposition process in step (1) as the main logic line, recursively deduce the failure modes of each layer. The specific modeling method is as follows: Use the risk assessment and modeling language published by object-oriented organization and the established basic model, and use the generalization method to define the failure modes of each layer, and at the same time establish the association relationship with the original system or function.

[0052] (3) Identify the failure modes from the bottom layer of the overall project and each subsystem, conduct FMEA analysis, and establish the FMEA item model: ① In each system, according to the layering result of step (1), directly identify the corresponding failure modes in the bottom-level functions or structures based on experience or logical relationships. Compare with the results identified by the main logic analysis method in step (2). If there is an increase, use the basic fault model to define it and add it to the model library of each layer. If there is no increase, do not modify. ② Taking each failure mode in the bottom-level failure mode library of each system as the basis, use the FMEA method to recursively deduce the upper-level failure modes caused by this failure mode and the resulting consequence states of this system to the upper layer. Each bottom-level failure mode corresponds to an FMEA item block, and each FMEA item block contains three elements: failure cause, failure mode, and consequence state, as well as the causal relationship among the three. ③ Compare with the upper-level failure mode library formed in step (2). If a new failure mode appears during the recursion, add it to the upper-level system failure mode library, otherwise do not modify.

[0053] (4) Conduct iterative fault analysis within each system. If a new consequence state, i.e., the top-level failure mode, is found in step (3), then use this consequence state as the top event of this system, repeat step (2) to conduct a main logic analysis, search for the lower-level failure modes. If new failure modes appear, repeat step (3)② to construct FMEA items and improve the failure mode library. If not, skip this step.

[0054] (5) Iterative fault analysis among systems: ① The overall project distributes the models of the underlying functions or structures and corresponding failure modes of its own system to each subsystem according to the division of responsibilities, so that each subsystem has read and write permissions for the model; ② Each subsystem refers to the received failure modes and corresponding functions or structures. If they are different from the top events of the previously conducted analysis, repeat step (2) to find out whether there will be new lower-level failure modes within the subsystem. If there are, then construct the FMEA entry model according to the modeling method in step (3); ③ Transmit the top-level failure mode library obtained from the subsystem analysis to the overall project. The overall project compares it with the underlying failure mode library of its own system. If the failure modes analyzed by the subsystem increase, the overall project uses step ② in step (3) to establish FMEA entries and perfect them accordingly by comparing with the upper-level failure mode library. Repeat step (4) and step (5) until no new failure modes occur in the overall project and the subsystems. Thus, a complete system fault analysis model is obtained.

[0055] (6) According to the safety measures concerned by each system (for example, the escape and emergency rescue measures of the overall project, the risk control design schemes such as system redundancy of the subsystem, etc.), incorporate the corresponding safety policies into the FMEA entries using the inclusion relationship and establish the traceability relationship with the corresponding failure modes.

[0056] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the technical principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A model-based hierarchical fault analysis method for complex manned spaceflight systems, characterized in that, While using SysML for the design and analysis of complex manned space systems, potential failures are identified through the decomposition of hierarchical system functions or structures. Fault mode analysis is carried out for each layer of the system based on the model, and through the iteration of models between layers, the fault analysis of the entire system is completed. Among them, the model that can be interacted between the overall project and subsystems is the bottom layer model of the overall project, that is, the top layer model of the subsystem, including the fault model. The fault analysis method includes: Step 1: Each system uses the risk assessment and modeling language published by object-oriented organization to establish a basic model for defining manned space faults through SysML, and based on this, defines fault modes, establishes a fault mode library, constructs FMEA entries, and associates fault response strategies. Step 2: The overall project only distributes the bottom layer model to the corresponding subsystems, and the subsystems only pass the top layer model to the overall project. Each system uses the hierarchical fault analysis method through the access of the interactive fault model to realize the iteration of fault analysis and improve the fault model of the entire system. The hierarchical fault analysis method described in Step 2 includes the following steps: (1) Decompose the function or structure of the system in a top-down manner to form a model of the forward design of the system. (2) Assume that the highest layer function or structure in the current level of the system fails, and refer to the system decomposition mode. Adopt the main logic analysis method to find the cause of the upper layer function or structure failure, that is, the failure mode of the lower layer system. (3) Based on the decomposition of the top layer function or structure to the bottom layer function or structure, directly identify the failure mode of the bottom layer. (4) Adopt a bottom-up manner, and use the FMEA method to recursively push up layer by layer on the basis of the bottom layer fault mode to obtain the upper layer failure mode and consequence state caused by it, and establish FMEA entries. (5) If the fault mode found in Step (3) is different from the one identified in Step (2), then expand the original bottom layer failure mode library, and use this different fault mode as the top event of the main logic analysis, and analyze from top to bottom to find whether there are new lower layer fault modes. If so, further expand the new lower layer fault mode library, and use the FMEA method to review the new fault analysis and establish FMEA entries. (6) The upper level system divides the system into the finest granularity it is concerned with within the current level to obtain subsystems, and decomposes the subsystems and the corresponding failure modes into each subsystem. (7) Each subsystem checks whether there are new top layer fault modes of the current level system. If so, repeat Step (2) and Step (4). If new fault modes of the upper level system are obtained again, feedback them to the upper level. After receiving them, the upper level system checks whether there are new bottom layer fault modes. If so, repeat Step (4). (8) Repeat Step (5) to Step (7) until consensus is reached among systems and no new fault modes appear.

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