Reliability evaluation method for multi-aircraft combined spacecraft

Abstract

The invention discloses a reliability evaluation method for a multi-aircraft combined spacecraft, and the method comprises the steps: building a reliability evaluation system for a multi-stage task of a combination, determining the connotation of a reliability index of the task, and verifying the evaluation requirements and targets; determining an aircraft and product reliability evaluation method; identifying reliability information, and collecting and analyzing effective evaluation subsamples; determining an evaluation range; and according to the reliability evaluation system, the reliability evaluation system, the effective evaluation subsample and the evaluation range, establishing an evaluation model, and finally obtaining a task reliability quantitative evaluation result of the combined aircraft. According to the method, the problems of inaccurate evaluation and poor effectiveness caused by mismatching of the reliability evaluation data sample size and the development / flight task process in the aircraft development and on-orbit operation process are solved, and a basis can be provided for task planning and decision making. Under the controllable cost, effective evaluation of important time points (such as product state determination and before launching) of a development stage and continuity of an on-orbit flight stage is realized.

Description

Technical Field

[0001] The present application relates to the technical field of overall design of spacecraft, and in particular to a reliability assessment method for a multi-spacecraft combined spacecraft. Background Art

[0002] Reliability assessment is an important means to discover reliability weaknesses and guide reliability improvement design. It is also a task that must be carried out during the development and long-term operation of spacecraft. NASA has carried out quantitative assessment of mission risks in the ground development, assembly and construction, and on-orbit operation stages of the International Space Station project, and has conducted three system assessments to extend the service life of the space station. It has been in orbit for more than 20 years. Based on the experience of the construction and operation of the International Space Station, reliability quantitative assessment can identify key failures that lead to astronaut casualties and mission failures, and can serve as a basis for planning the launch of uplink cargo and evaluating the feasibility of extending the life of the spacecraft.

[0003] Since the mission of the combination is implemented in steps, the evaluation data is gradually generated across the ground development and on-orbit flight stages, and the evaluation timing is scattered. There is a mismatch between the sample size of the reliability evaluation data and the development / flight mission process, resulting in inaccurate evaluation and poor effectiveness. In addition, the multi-spacecraft combination repairable spacecraft usually requires an on-orbit operation life of more than 15 years and high reliability requirements, especially for large and complex electromechanical products. Based on the whole machine test data, the reliability evaluation using Weibull distribution requires multiple evaluation sub-samples with a life span far exceeding 15 years. For products such as solar wings and control moment gyroscopes, not only the price of a single unit exceeds 10 million yuan, but also the production cycle is long and the production capacity is limited. It is costly to conduct multiple sub-sample quantitative tests to accumulate reliability evaluation sub-samples in engineering feasibility checks.

[0004] In addition, during the long-term operation of spacecraft in orbit, on-orbit flight data continues to accumulate, and the sample size is continuously expanded based on the life and reliability information in the development stage, providing conditions for on-orbit mission reliability assessment. However, how to effectively integrate on-orbit flight data with the verification information in the development stage to improve the effectiveness of the assessment is another difficulty faced. Summary of the invention

[0005] The present invention provides a reliability assessment method for a multi-aircraft combined spacecraft, with the aim of solving the problem of inaccurate assessment and poor effectiveness caused by the mismatch between the sample size of reliability assessment data and the development / flight mission progress during the aircraft development and on-orbit operation, and can provide a basis for mission planning and decision-making.

[0006] In a first aspect, a reliability assessment method for a multi-vehicle combined spacecraft is provided, comprising:

[0007] Establish a reliability assessment system for multi-stage tasks of the complex, clarify the connotation of task reliability indicators and the requirements and objectives of verification and assessment;

[0008] Determine methods for evaluating aircraft and product reliability;

[0009] Reliability information identification, collection and analysis of effective evaluation samples;

[0010] Determine the scope of the assessment;

[0011] According to the reliability evaluation system, reliability evaluation system, effective evaluation sub-samples and evaluation scope, an evaluation model is established, and finally the quantitative evaluation results of the mission reliability of the combined aircraft are obtained.

[0012] In conjunction with the first aspect, in certain implementations of the first aspect, the establishment of a reliability evaluation system for multi-stage tasks of the assembly, clarifying the connotation of task reliability indicators and verification evaluation requirements and objectives, includes:

[0013] According to the spacecraft mission profile, the probabilistic risk analysis (PRA) method is used to identify the initial events that lead to the failure of the top-level mission, and the independence analysis of the initial events is carried out to determine the normal flight mission of the spacecraft, and the short-term special missions implemented on this basis, including the rendezvous and docking mission, the transfer mission, the propellant replenishment mission, and the extravehicular activity mission as the second-level mission;

[0014] A comprehensive analysis is conducted on the timing of the generation of data samples that can be used for quantitative evaluation during the ground-based development and on-orbit flight of various levels of spacecraft products. Combined with the on-orbit mission profile, the quantitative evaluation requirements for the second-tier mission reliability indicators are determined to form a reliability evaluation system.

[0015] In conjunction with the first aspect, in some implementations of the first aspect, the reliability evaluation system satisfies:

[0016] During the single-cabin flight phase, for the assessment object A cabin, the reliability parameters include autonomous flight mission reliability, propellant replenishment support mission reliability, astronaut and cargo transportation support mission reliability, and extravehicular activity support mission reliability. The assessment time is before launch and at the end of the single-cabin independent flight.

[0017] During the assembly and construction phase, for the assessment object B module, the reliability parameters include autonomous flight mission reliability and docking and transfer mission reliability. The assessment time for autonomous flight mission reliability is before launch and at the end of the single module independent flight, and the assessment time for docking and transfer mission reliability is before launch, at the end of the single module independent flight and at the end of construction.

[0018] During the assembly and construction phase, for the evaluation object A module + B module combination, the reliability parameters include the reliability of the assembly and construction mission and the reliability of the autonomous flight mission of the two-module combination. The evaluation time is before launch and at the end of the independent flight of a single module.

[0019] During the assembly and construction phase, for the assessment object C module, the reliability parameters include autonomous flight mission reliability and docking and transfer mission reliability. The assessment time for autonomous flight mission reliability is before launch and at the end of the single module independent flight, and the assessment time for docking and transfer mission reliability is before launch, at the end of the single module independent flight and at the end of construction.

[0020] During the assembly and construction phase and the operation phase, for the evaluation object A module + B module + C module combination, the reliability parameters include assembly and construction mission reliability, three-module combination autonomous flight mission reliability, propellant replenishment support mission reliability, astronaut and cargo transportation support mission reliability and extravehicular activity support mission reliability. The evaluation time is before launch, at the end of the independent flight of a single module and at the end of construction.

[0021] In conjunction with the first aspect, in certain implementations of the first aspect, the method for determining aircraft and product reliability assessment includes:

[0022] The system reliability assessment adopts the Bayesian method, starting from the pre-test information of the on-orbit failure rate of components, and combining the field test information of single machine, subsystem and spacecraft at all levels to evaluate the reliability that the spacecraft can achieve. For high-reliability products with insufficient tests, the predicted failure rate is converted into a confidence upper limit, which is converted into an exponential distribution and used as pre-test information for evaluation.

[0023] In the system reliability assessment, the inter-level information conversion method is as follows: after the field test of the system and subsystem, the exact operating time and number of failures of each device are counted, which are the field test information of each device; this information is combined with the pre-test information to obtain the post-test information of the device, and then the system reliability is directly integrated according to the system reliability logical structure.

[0024] In conjunction with the first aspect, in certain implementations of the first aspect, different reliability assessment models are applied to the aircraft product according to the failure mode:

[0025] The binomial distribution model is used for success-failure products, which is suitable for pyrotechnic products;

[0026] The exponential distribution model is used for products whose main failure mode is accidental failure mode. It is suitable for electronic products and electromechanical products with short working time and not entering the wear and degradation period during the mission;

[0027] The main failure mode is the wear failure mode. The Weibull distribution model is used for products that are difficult to characterize the working state with a single performance parameter. It is suitable for products such as motors, bearings, and engines.

[0028] Products that can use a single performance parameter to characterize their working state use the normal distribution model, which is suitable for batteries, solar cell circuits, and products with leakage rate as their product performance parameter;

[0029] Long-life products usually require the establishment of performance models or acceleration models. The performance degradation model characterizes the relationship between product performance and working time. The Arrhenius model is used in high-temperature accelerated life tests of electronic products. Other products establish accelerated models based on the impact of accelerated stress on life.

[0030] In conjunction with the first aspect, in certain implementations of the first aspect, the reliability information identification, collection and analysis of effective evaluation sub-samples include:

[0031] Establish a data validity evaluation mechanism for reliability assessment, covering the tests during ground development and the on-orbit flight process, and select valid data as evaluation matrix information from the status of the test products, test conditions, test conditions at all levels of development and testing, and the actual working conditions of the on-orbit flight products;

[0032] Build a product life cycle reliability data collection system to comprehensively collect test and flight data of common products in the assembly and products of similar models, and realize the collection and management of assembly reliability information.

[0033] In conjunction with the first aspect, in certain implementations of the first aspect, reliability information is identified based on product status changes, and the identification principles are as follows:

[0034] Faulty products are non-repairable products and will be treated as related faults during evaluation and counted as faults.

[0035] If the faulty product is an on-orbit replaceable unit (ORU), the faulty product is replaced after the fault, but after analysis, it is found to be an individual random fault of the product, and the technical status of the ORU has not changed. During the assessment, it is handled as an associated fault, and the product mission reliability is re-evaluated according to the reliability assessment model with faults and the number of failures is accumulated, but the working time before and after the abnormality is included in the assessment sub-sample;

[0036] If an ORU product fails and is analyzed to be a design or process problem, the ORU technical status has changed and it is replaced with an ORU in a new status. During the evaluation, the mission reliability of the new status product is directly evaluated, and the method is consistent with the evaluation method in the development stage. The evaluation sub-sample is determined according to the minimum envelope principle after analyzing the impact of the status change on the product reliability;

[0037] When the new-status ORU cannot use the evaluation samples of the previous product, it is necessary to accumulate reliability evaluation samples again. The evaluation samples are mainly based on the working time of the actual working products in orbit to ensure that the evaluation samples are authentic and valid, and to avoid deviations caused by differences between the sky and the earth in ground verification tests.

[0038] In conjunction with the first aspect, in certain implementations of the first aspect, determining the evaluation scope includes:

[0039] When modeling the system mission reliability assessment model, relevant functional systems and products are identified according to the mission requirements; the functional systems related to autonomous flight missions include the structure and mechanism system functions, control and propulsion system functions, energy and power supply and distribution system functions, communication and data management system functions, and thermal management system functions; the functional systems related to special missions include rendezvous and docking support functions, manned stay support functions, propellant replenishment functions, and extravehicular activity functions;

[0040] The product scope of each functional system evaluation is determined according to the importance of the function. Products that will lead to functional failure if their failure affects the safety of the spacecraft and the reliability of mission execution should be included in the evaluation scope, and they should be identified by comprehensive application of safety analysis, failure mode and effects analysis FMEA, and fault tree analysis FTA.

[0041] In conjunction with the first aspect, in certain implementations of the first aspect, the on-orbit mission reliability assessment scope is determined in accordance with the following principles:

[0042] According to the actual flight plan and mission requirements on orbit, determine the usage quantity reserve model of terminal products, which include: lighting, cameras, mobile phone image and voice related equipment, as well as switches, payload adapters and application mission related terminal equipment;

[0043] Functions that do not directly cause mission failure, but only reduce the comfort and convenience of astronauts’ lives and some performance indicators, are not included in the scope of system mission reliability assessment;

[0044] When a product's technical status changes due to an abnormality, it is analyzed that the previous reliability assessment samples cannot be used for the new status product, and the on-orbit usage data needs to be re-accumulated. When the on-orbit usage data is temporarily insufficient, the product will not be included in the system reliability assessment model, and the on-orbit usage time of the product will be accumulated normally, and the product life and reliability assessment will be continuously carried out. If there is a risk to reliability in use, an uplink spare parts demand will be put forward.

[0045] In conjunction with the first aspect, in certain implementations of the first aspect, establishing the evaluation model and ultimately obtaining a quantitative evaluation result of the mission reliability of the combined aircraft includes:

[0046] According to the redundant configuration inside a single cabin and the integrated use mode of functions between cabins, and in accordance with the reliability logical relationship between key reliability components, single machines, combination functions, and second-level tasks, an inverted pyramid structure is used to establish a system mission reliability assessment model; with mission requirements as the center and the combination as a whole, accurate modeling of system mission reliability is achieved, including system-level assessment, function-level assessment, and single-machine-level assessment from top to bottom, and single-machine-level assessment.

[0047] Compared with the prior art, the solution provided by this application includes at least the following beneficial technical effects:

[0048] The present invention provides a reliability assessment method for a multi-vehicle combined spacecraft, which can achieve continuous effective assessment at important time points in the development stage (such as determining product status and before launch) and during the on-orbit flight stage at a controllable cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 The present invention is a multi-vehicle combined spacecraft reliability assessment flow chart.

[0050] Figure 2 It is a Bayesian evaluation flow chart of the present invention.

[0051] Figure 3 It is a flow chart of the modeling of mission reliability assessment of a multi-aircraft assembly of the present invention. DETAILED DESCRIPTION

[0052] The present application is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0053] like Figure 1 As shown, the present invention provides a reliability assessment method for a multi-aircraft combined spacecraft. The specific steps are as follows.

[0054] Step 1: Establish a reliability assessment system for the multi-stage tasks of the complex, clarify the connotation of task reliability indicators and verify the assessment requirements and objectives.

[0055] According to the spacecraft mission profile, the probabilistic risk analysis (PRA) method is used to identify the initial events that lead to the failure of the top-level mission. An independence analysis is conducted on the initial events, and the second-level tasks are determined to include the normal flight mission of the spacecraft and the short-term special missions implemented on this basis, including rendezvous and docking missions, transfer missions, propellant replenishment missions, and extravehicular activity missions.

[0056] A comprehensive analysis is made of the timing of data samples that can be used for quantitative evaluation during the ground development and on-orbit flight of various levels of spacecraft products. Combined with the on-orbit mission profile, the quantitative evaluation requirements of the second-tier mission reliability indicators are determined to form a reliability evaluation system. The evaluation system is shown in Table 1.

[0057] Table 1 Mission reliability assessment system for multi-aircraft combination

[0058]

[0059]

[0060] Step 2: Determine the aircraft and product reliability assessment methods.

[0061] Spacecraft products are extremely small sample complex products, and the Bayesian method can be used to evaluate the system reliability. The Bayesian reliability evaluation starts with the prior information of the on-orbit flight failure rate of components, and combines the field test information of single machines, subsystems and spacecraft at all levels to evaluate the reliability that the spacecraft can achieve. It is mainly for high-reliability products with insufficient tests. The predicted failure rate value is converted into a confidence upper limit, which is converted into an exponential distribution and used as prior information for evaluation. For details of the Bayesian evaluation process, see Figure 2 .

[0062] In the system reliability assessment, the inter-level information conversion method is as follows: after the field test of the system and subsystem, the exact operating time and failure times of each device are counted, which are the field test information of each device (that is, the system and subsystem test information is used for a single machine, and integrated from bottom to top). This information is combined with the pre-test information to obtain the post-test information of the device, and then the system reliability is directly integrated according to the system reliability logical structure.

[0063] Aircraft products are suitable for different reliability assessment models according to the failure mode:

[0064] 1) The binomial distribution model is used for success-failure products, which is suitable for pyrotechnic products;

[0065] 2) The exponential distribution model is used for products whose main failure mode is accidental failure mode. It is suitable for electronic products and electromechanical products with short working time and not entering the wear and degradation period during the mission;

[0066] 3) The main failure mode is the wear failure mode. For products whose working status is difficult to be characterized by a single performance parameter, the Weibull distribution model is used, which is suitable for products such as motors, bearings, and engines;

[0067] 4) Products that can use a single performance parameter to characterize the working state use the normal distribution model, which is suitable for batteries, solar cell circuits, and products with leakage rate as the product performance parameter;

[0068] 5) Long-life products usually require the establishment of performance models or acceleration models. The performance degradation model should characterize the relationship between product performance and working time. The Arrhenius model is used in high-temperature accelerated life tests of electronic products, and other products establish accelerated models based on the impact of accelerated stress on life.

[0069] Step 3: Identify reliability information, collect and analyze valid evaluation samples

[0070] Establish a data validity evaluation mechanism for reliability assessment, covering the tests in the ground development process and the on-orbit flight process, and select valid data as the evaluation matrix information from the status of the participating products, test conditions, test conditions, and actual working conditions of the on-orbit flight products at all levels of development and testing; at the same time, build a product life cycle reliability data collection system to comprehensively collect test and flight data including common products of the assembly and other types of similar products, so as to realize the collection and management of assembly reliability information.

[0071] During the on-orbit process, the product is affected by space radiation, high-energy particles, microgravity environment, and the differences between the actual on-orbit working conditions, usage mode and development stage. On-orbit anomalies may occur, and abnormal handling measures usually lead to changes in product status. Reliability information identification is required for the specific situation of product status changes. Combining the main aspects of on-orbit status changes, the identification principles are proposed as follows:

[0072] 1) Faulty products are non-repairable products and will be treated as related faults during evaluation and counted as faults;

[0073] 2) If the faulty product is an on-orbit replaceable unit (ORU), the faulty product is replaced after the fault, but after analysis, it is found that the product is an individual random fault, and the technical status of the ORU has not changed. During the evaluation, it is handled as an associated fault, and the product mission reliability (accumulated number of failures) is re-evaluated according to the reliability evaluation model with faults, but the working time before and after the abnormality can be included in the evaluation sub-sample;

[0074] 3) If the ORU product fails, it is analyzed as a design or process problem, the ORU technical status has changed, and it is replaced with an ORU in a new status. During the evaluation, the mission reliability of the new status product is directly evaluated, and the method is consistent with the evaluation method in the development stage. The evaluation sub-sample needs to be determined according to the minimum envelope principle after analyzing the impact of the status change on the product reliability (if the product reliability is improved after the change, the reliability evaluation sub-sample of the original status product can be adopted after analyzing the inheritance).

[0075] 4) When the new-status ORU cannot use the evaluation samples of the previous product, it is necessary to accumulate reliability evaluation samples again. The evaluation samples are mainly based on the working time of the actual working products in orbit to ensure that the evaluation samples are authentic and valid, and to avoid deviations caused by the difference between the sky and the earth in the ground verification test.

[0076] Through reliability information identification, products with insufficient evaluation samples are identified, and additional quantitative verification tests are planned. In view of the long verification test cycle of complex electromechanical products and the problem that production capacity constraints cannot be used to invest in more whole machine samples, a strategy based on comprehensive evaluation of key reliability components is adopted, and reliability key component tests are planned in combination with whole machine tests. Through the strategy of combining multi-sample component tests with small sample whole machine tests, the verification timing is moved forward and the verification cost is significantly controlled.

[0077] Step 4: Determine the scope of the assessment

[0078] When modeling the system mission reliability assessment model, relevant functional systems and products should be identified according to the mission requirements. The functional systems related to autonomous flight missions should include the functions of the structure and mechanism system, the control and propulsion system, the energy and power supply and distribution system, the communication and data management system, the thermal management system, etc.; the functional systems related to special missions should include the rendezvous and docking support function, the manned stay support function, the propellant replenishment function, the extravehicular activity function, etc.

[0079] The product scope of each functional system evaluation is determined according to the importance of the function. Products that will lead to functional failure and affect the safety of the spacecraft and the reliability of mission execution should be included in the evaluation scope. They can be identified by comprehensive application of safety analysis, failure mode and effects analysis (FMEA), fault tree analysis (FTA) and other methods.

[0080] On this basis, the scope of on-orbit mission reliability assessment is determined in accordance with the following principles:

[0081] 1) Determine the usage quantity reserve model of terminal products based on the actual flight plan and mission requirements on orbit. Terminal products include: lighting, cameras, mobile phones and other image and voice related equipment, as well as switches, payload adapters and other application mission related terminal equipment.

[0082] 2) It will not directly cause mission failure, but will only reduce the comfort and convenience of astronauts' lives and the functions of some performance indicators, and is not included in the scope of system mission reliability assessment.

[0083] 3) When a product's technical status changes due to an abnormality, after analysis it is found that the previous reliability assessment samples cannot be used for the new status product and it is necessary to re-accumulate on-orbit usage data. If the on-orbit usage data is temporarily insufficient, the product will not be included in the system reliability assessment model, and the on-orbit usage time of the product will be accumulated normally, and the product life and reliability assessment will be continuously carried out. If there is a risk to reliability in use, an uplink spare parts demand will be proposed.

[0084] The fifth step is to establish an evaluation model and finally obtain the quantitative evaluation results of the mission reliability of the combined aircraft.

[0085] First, according to the internal redundant configuration of a single cabin and the integrated use mode of functions between cabins, and in accordance with the reliability logic relationship between key reliability components, single machines, combination functions, and second-level tasks, an inverted pyramid structure is used to establish a system mission reliability assessment model. Breaking through the limitations of subsystems and cabins, focusing on mission requirements and taking the combination as an organic whole, the system mission reliability is accurately modeled. The reliability assessment model establishment process is as follows: Figure 3 shown.

[0086] Although the present invention is disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope defined by the claims of the present invention.

Claims

1. A reliability assessment method for a multi-vehicle combined spacecraft, characterized in that: include: Establish a reliability assessment system for multi-stage tasks of the complex, clarify the connotation of task reliability indicators and the requirements and objectives of verification and assessment; Determine the aircraft and product reliability assessment system; Reliability information identification, collection and analysis of effective evaluation samples; Determine the scope of the assessment; According to the reliability evaluation system, reliability evaluation system, effective evaluation sub-samples and evaluation scope, an evaluation model is established, and finally the quantitative evaluation results of the mission reliability of the combined aircraft are obtained.

2. The method according to claim 1, characterized in that The above-mentioned establishment of a reliability assessment system for multi-stage tasks of the combination, clarifying the connotation of task reliability indicators and verification assessment requirements and objectives, includes: According to the spacecraft mission profile, the probabilistic risk analysis (PRA) method is used to identify the initial events that lead to the failure of the top-level mission, and the independence analysis of the initial events is carried out to determine the normal flight mission of the spacecraft, and the short-term special missions implemented on this basis, including the rendezvous and docking mission, the transfer mission, the propellant replenishment mission, and the extravehicular activity mission as the second-level mission; A comprehensive analysis is conducted on the timing of the generation of data samples that can be used for quantitative evaluation during the ground-based development and on-orbit flight of various levels of spacecraft products. Combined with the on-orbit mission profile, the quantitative evaluation requirements for the second-tier mission reliability indicators are determined to form a reliability evaluation system.

3. The method according to claim 2, characterized in that The reliability evaluation system meets the following requirements: During the single-cabin flight phase, for the assessment object A cabin, the reliability parameters include autonomous flight mission reliability, propellant replenishment support mission reliability, astronaut and cargo transportation support mission reliability, and extravehicular activity support mission reliability. The assessment time is before launch and at the end of the single-cabin independent flight. During the assembly and construction phase, for the assessment object B module, the reliability parameters include autonomous flight mission reliability and docking and transfer mission reliability. The assessment time for autonomous flight mission reliability is before launch and at the end of the single module independent flight, and the assessment time for docking and transfer mission reliability is before launch, at the end of the single module independent flight and at the end of construction. During the assembly and construction phase, for the evaluation object A module + B module combination, the reliability parameters include the reliability of the assembly and construction mission and the reliability of the autonomous flight mission of the two-module combination. The evaluation time is before launch and at the end of the independent flight of a single module. During the assembly and construction phase, for the assessment object C module, the reliability parameters include autonomous flight mission reliability and docking and transfer mission reliability. The assessment time for autonomous flight mission reliability is before launch and at the end of the single module independent flight, and the assessment time for docking and transfer mission reliability is before launch, at the end of the single module independent flight and at the end of construction. During the assembly and construction phase and the operation phase, for the evaluation object A module + B module + C module combination, the reliability parameters include assembly and construction mission reliability, three-module combination autonomous flight mission reliability, propellant replenishment support mission reliability, astronaut and cargo transportation support mission reliability and extravehicular activity support mission reliability. The evaluation time is before launch, at the end of the independent flight of a single module and at the end of construction.

4. The method according to claim 1, characterized in that: The method for determining the reliability assessment of an aircraft and a product includes: The system reliability assessment adopts the Bayesian method, starting from the pre-test information of the on-orbit failure rate of components, and combining the field test information of single machine, subsystem and spacecraft at all levels to evaluate the reliability that the spacecraft can achieve. For high-reliability products with insufficient tests, the predicted failure rate is converted into a confidence upper limit, which is converted into an exponential distribution and used as pre-test information for evaluation. In the system reliability assessment, the inter-level information conversion method is as follows: after the field test of the system and subsystem, the exact operating time and number of failures of each device are counted, which are the field test information of each device; this information is combined with the pre-test information to obtain the post-test information of the device, and then the system reliability is directly integrated according to the system reliability logical structure.

5. The method according to claim 4, characterized in that Aircraft products are suitable for different reliability assessment models according to the failure mode: The binomial distribution model is used for success-failure products, which is suitable for pyrotechnic products; The exponential distribution model is used for products whose main failure mode is accidental failure mode. It is suitable for electronic products and electromechanical products with short working time and not entering the wear and degradation period during the mission; The main failure mode is the wear failure mode. The Weibull distribution model is used for products that are difficult to characterize the working state with a single performance parameter. It is suitable for products such as motors, bearings, and engines. Products that can use a single performance parameter to characterize their working state use the normal distribution model, which is suitable for batteries, solar cell circuits, and products with leakage rate as their product performance parameter; Long-life products usually require the establishment of performance models or acceleration models. The performance degradation model characterizes the relationship between product performance and working time. The Arrhenius model is used in high-temperature accelerated life tests of electronic products. Other products establish accelerated models based on the impact of accelerated stress on life.

6. The method according to claim 1, characterized in that The reliability information identification, collection and analysis of effective evaluation samples include: Establish a data validity evaluation mechanism for reliability assessment, covering the tests during ground development and the on-orbit flight process, and select valid data as evaluation matrix information from the status of the test products, test conditions, test conditions at all levels of development and testing, and the actual working conditions of the on-orbit flight products; Build a product life cycle reliability data collection system to comprehensively collect test and flight data of common products in the assembly and products of similar models, and realize the collection and management of assembly reliability information.

7. The method according to claim 6, characterized in that Reliability information is identified based on product status changes. The identification principles are as follows: Faulty products are non-repairable products and will be treated as related faults during evaluation and counted as faults. If the faulty product is an on-orbit replaceable unit (ORU), the faulty product is replaced after the fault, but after analysis, it is found to be an individual random fault of the product, and the technical status of the ORU has not changed. During the assessment, it is handled as an associated fault, and the product mission reliability is re-evaluated according to the reliability assessment model with faults and the number of failures is accumulated, but the working time before and after the abnormality is included in the assessment sub-sample; If an ORU product fails and is analyzed to be a design or process problem, the ORU technical status has changed and it is replaced with an ORU in a new status. During the evaluation, the mission reliability of the new status product is directly evaluated, and the method is consistent with the evaluation method in the development stage. The evaluation sub-sample is determined according to the minimum envelope principle after analyzing the impact of the status change on the product reliability; When the new-status ORU cannot use the evaluation samples of the previous product, it is necessary to accumulate reliability evaluation samples again. The evaluation samples are mainly based on the working time of the actual working products in orbit to ensure that the evaluation samples are authentic and valid, and to avoid deviations caused by differences between the sky and the earth in ground verification tests.

8. The method according to claim 1, characterized in that Determining the scope of assessment includes: When modeling the system mission reliability assessment model, relevant functional systems and products are identified according to the mission requirements; the functional systems related to autonomous flight missions include the structure and mechanism system functions, control and propulsion system functions, energy and power supply and distribution system functions, communication and data management system functions, and thermal management system functions; the functional systems related to special missions include rendezvous and docking support functions, manned stay support functions, propellant replenishment functions, and extravehicular activity functions; The product scope of each functional system evaluation is determined according to the importance of the function. Products that will lead to functional failure if their failure affects the safety of the spacecraft and the reliability of mission execution should be included in the evaluation scope, and they should be identified by comprehensive application of safety analysis, failure mode and effects analysis FMEA, and fault tree analysis FTA.

9. The method according to claim 8, characterized in that The scope of on-orbit mission reliability assessment is also determined in accordance with the following principles: According to the actual flight plan and mission requirements on orbit, determine the usage quantity reserve model of terminal products, which include: lighting, cameras, mobile phone image and voice related equipment, as well as switches, payload adapters and application mission related terminal equipment; Functions that do not directly cause mission failure, but only reduce the comfort and convenience of astronauts’ lives and some performance indicators, are not included in the scope of system mission reliability assessment; When a product's technical status changes due to an abnormality, it is analyzed that the previous reliability assessment samples cannot be used for the new status product, and the on-orbit usage data needs to be re-accumulated. When the on-orbit usage data is temporarily insufficient, the product will not be included in the system reliability assessment model, and the on-orbit usage time of the product will be accumulated normally, and the product life and reliability assessment will be continuously carried out. If there is a risk to reliability in use, an uplink spare parts demand will be put forward.

10. The method according to claim 1, characterized in that The evaluation model is established to finally obtain the quantitative evaluation results of the mission reliability of the combined aircraft, including: According to the redundant configuration inside a single cabin and the integrated use mode of functions between cabins, and in accordance with the reliability logical relationship between key reliability components, single machines, combination functions, and second-level tasks, an inverted pyramid structure is used to establish a system mission reliability assessment model; with mission requirements as the center and the combination as a whole, accurate modeling of system mission reliability is achieved, including system-level assessment, function-level assessment, and single-machine-level assessment from top to bottom, and single-machine-level assessment.

Images