Reliability index distribution, verification and evaluation method based on reuse and power redundancy

Abstract

The invention discloses a reliability index distribution, verification and evaluation method based on reuse and power redundancy, and the method comprises the steps: S1, carrying out the reliability index distribution of each product, and obtaining the reliability index of each product; s2, calculating the system reliability of the power redundancy system according to the reliability index of each product; s3, according to the system reliability and the index requirement, judging whether the distribution result meets the requirement, if so, entering step S4, and if not, returning to step S1; s4, calculating failure rate or characteristic life according to the reliability index of each product; s5, calculating test time according to the failure rate or the characteristic life; s6, carrying out a reliability test according to the test time, and counting the total number of faults; and S7, according to the total number of faults, calculating to obtain reliability, and realizing reliability evaluation of the product. The problem that a part of products in a traditional distribution method are high in reliability index is solved, and the purpose of saving test expenditure is achieved.

Description

Technical Field

[0001] The invention relates to a reliability index allocation, verification and evaluation method based on reuse and power redundancy, and belongs to the technical field of aerospace overall design and reliability engineering. Background Art

[0002] Previous launch vehicles were all disposable and did not have power redundancy technology. Reliability index allocation adopted conventional practices. According to a simple series-parallel model, the rocket reliability index was allocated to each system and each unit. When conducting verification and evaluation, only a single mission was considered. First, reliability tests were carried out on each unit, and then reliability evaluation was carried out. Finally, the LM method was used to evaluate the reliability of the entire rocket mission. "Task reliability model index allocation method based on improved importance and complexity" (Patent No.: 202311377580.1, Patent Owner: Jiangsu Hezheng Special Equipment Co., Ltd.), "A reliability index allocation method considering multi-dimensional factors" (Patent No.: 202311312810.6, Patent Owner: Beijing Institute of Space Systems Engineering), "A space orbit control engine reliability assessment method" (Patent No.: 201810581542.0, Patent Owner: Shanghai Space Propulsion Institute), "A reliability assessment method for pump-type liquid rocket engine turbopump" (Patent No.: 202311345225.6, Patent Owner: China Aerospace Standardization Institute), etc. and some other professional books and literature papers on reliability engineering reflect the above background technology.

[0003] As reuse and power redundancy become the representative technologies of the new generation of rockets, the traditional single-mission profile has been transformed into a multi-mission profile, and the simple series-parallel system has been transformed into a complex functional logic. The above reliability methods are no longer applicable. In order to adapt to such complex reliability problems, it is necessary to develop a new technology and method that can effectively solve the reliability problem considering reuse and power redundancy. Summary of the invention

[0004] The technical problem solved by the present invention is: to overcome the deficiencies of the prior art, to provide a reliability index allocation, verification and evaluation method based on reuse and power redundancy, and to provide a reliability verification scheme considering different reuse times.

[0005] The technical solution of the present invention is:

[0006] The present invention discloses a reliability index allocation, verification and evaluation method based on reuse and power redundancy, including:

[0007] S1. Allocate reliability indexes for each product to obtain the reliability index of each product;

[0008] S2. Calculate the system reliability of the power redundancy system based on the reliability index of each product;

[0009] S3, judging whether the allocation result meets the requirements according to the system reliability and index requirements, if so, proceeding to step S4, if not, returning to step S1;

[0010] S4. Calculate the failure rate or characteristic life according to the reliability index of each product;

[0011] S5. Calculate the test time based on the failure rate or characteristic life;

[0012] S6. Carry out reliability tests according to the test time and count the total number of failures;

[0013] S7. Calculate the reliability based on the total number of failures to evaluate the reliability of the product.

[0014] Furthermore, in the above method, the system reliability of the power redundancy system is specifically:

[0015]

[0016] Among them, R g1 is the reliability of a single engine at rated thrust and rated working time, R g2 R is the reliability of a single engine when it operates beyond the rated thrust or exceeds the rated operating time. g3 It is the reliability of the engine when it works to the moment when failure is allowed; N is the number of identical engines in the system, and K is the minimum number of engines required to work normally in the power system.

[0017] Furthermore, in the above method, the failure rate is specifically:

[0018] If the product life follows an exponential distribution, the formula for calculating the product failure rate is:

[0019]

[0020] Among them, R1, R n , R 1-N They represent the reliability of the first task, the reliability of the nth task, and the reliability of completing N tasks respectively; λ represents the product failure rate, and t0 represents the single task time.

[0021] Furthermore, in the above method, the characteristic lifespan is specifically:

[0022] If the product life follows the Weibull distribution, the formula for calculating the characteristic life of the product is:

[0023]

[0024] Among them, t0 is the single task time, θ is the product scale parameter or characteristic life, m is the shape parameter, R1, R n , R 1-N They are the reliability of the first task, the reliability of the nth task, and the reliability of completing N tasks respectively.

[0025] Furthermore, in the above method, the test time is specifically:

[0026] For the test time of the power redundancy system, the calculation formula is:

[0027]

[0028] Among them, R g2 is the reliability of the engine when it operates at a thrust higher than the rated thrust, R g1 is the reliability when working at rated thrust; t i , t′ i represents the total test time of a single engine for reliability test at rated thrust and overrated thrust respectively, N and N′ are the corresponding number of test units; γ is the confidence level; K is the environmental factor, indicating that the test time at overrated thrust is equivalent to K times the test time at rated thrust; m is the shape parameter; r represents the total number of failures occurring during the test; t0 is the single mission time.

[0029] Furthermore, in the above method, the test time is specifically:

[0030] For products with exponential life distribution, the total test time formula is:

[0031]

[0032] Where T represents the total test time, λ represents the failure rate distribution value, represents χ with 2r+2 degrees of freedom 2 The gamma quantile of the distribution, r, represents the total number of failures that occurred during the test.

[0033] Furthermore, in the above method, the test time is specifically:

[0034] For products whose life follows the Weibull distribution, the test time formula is:

[0035] The calculation formula for the test time of the first task is:

[0036] The calculation formula for the test time after completing N tasks is:

[0037] Among them, t iis the cumulative test time of the i-th product, n is the number of test products, t0 is the single task time, R1, R n , R 1-N They are the reliability of the first mission, the reliability of the nth mission, and the reliability of completing N missions, respectively. m is the shape parameter, and r is the total number of failures that occurred during the test.

[0038] Furthermore, in the above method, the reliability is specifically:

[0039] For products whose lifespan follows an exponential distribution, the reliability evaluation formula is:

[0040]

[0041] R 1-N =R N

[0042] Among them, t0 is the single task time, represents χ with 2r+2 degrees of freedom 2 The gamma quantile of the distribution, T is the total trial time, and N is the number of trials.

[0043] Furthermore, in the above method, the reliability is specifically:

[0044] For products whose life follows the Weibull distribution, the reliability calculation formula is:

[0045]

[0046] Among them, t0 is the single task time, represents χ with 2r+2 degrees of freedom 2 Distribution gamma quantile, t i is the cumulative test time of the i-th product, t i is the total test time of a single engine for reliability test according to rated thrust; m is the shape parameter, N is the number of test units; R1, R n , R 1-N They are the reliability of the first task, the reliability of the nth task, and the reliability of completing N tasks respectively.

[0047] Furthermore, in the above method, the reliability is specifically:

[0048] The reliability R of the engine in the power redundancy system when working at rated thrust g1 , reliability R when working at over rated thrust g2 , the calculation formula is:

[0049]

[0050] Among them, t0 is the single task time, represents χ with 2r+2 degrees of freedom 2 Distribution gamma quantile, t i is the total test time of the i-th single engine for reliability test according to rated thrust; t′2 is the total test time of the single engine for reliability test according to over-rated thrust; m is the shape parameter, and N and N′ are the corresponding number of test units.

[0051] The beneficial effects of the present invention and the prior art are:

[0052] (1) Based on the characteristics of rocket reuse missions, the present invention provides a reliability index formulation for typical rocket distribution products when they are reused multiple times and the mathematical relationship between the various indexes, thereby solving the problem of conflicts between different indexes that may exist in the reliability index allocation process;

[0053] (2) The present invention adopts a mathematical model of the reliability of the voting system and provides a reliability index allocation process when power redundancy is considered, thereby solving the problem of high reliability indexes of some products in the traditional allocation method and achieving the purpose of saving test expenses;

[0054] (3) Based on different distribution models of products, the present invention provides a reliability verification scheme considering different reuse times, and further provides a verification scheme for variable thrust engines by comprehensively utilizing various tests, thus filling the gap in product reliability verification schemes under such problems;

[0055] (4) The present invention adopts the environmental factor theory, provides a method for reliability verification and evaluation of an engine operating at over-rated thrust using rated thrust test data, and provides a specific mathematical formula, which can effectively save test costs and test cycles. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 It is a schematic diagram of the reliability index allocation process considering reuse and power redundancy of the present invention. DETAILED DESCRIPTION

[0057] The present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0058] The present invention discloses a reliability index allocation, verification and evaluation method based on reuse and power redundancy, including:

[0059] S1. Allocate reliability indexes for each product to obtain the reliability index of each product;

[0060] S2. Calculate the system reliability of the power redundancy system based on the reliability index of each product;

[0061] S3, judging whether the allocation result meets the requirements according to the system reliability and index requirements, if so, proceeding to step S4, if not, returning to step S1;

[0062] S4. Calculate the failure rate or characteristic life according to the reliability index of each product;

[0063] S5. Calculate the test time based on the failure rate or characteristic life;

[0064] S6. Carry out reliability tests according to the test time and count the total number of failures;

[0065] S7. Calculate the reliability based on the total number of failures to evaluate the reliability of the product.

[0066] Preferably, the system reliability of the power redundancy system is specifically:

[0067]

[0068] Among them, R g1 is the reliability of a single engine at rated thrust and rated working time, R g2 R is the reliability of a single engine when it operates beyond the rated thrust or exceeds the rated operating time. g3 It is the reliability of the engine when it works to the moment when failure is allowed; N is the number of identical engines in the system, and K is the minimum number of engines required to work normally in the power system.

[0069] Preferably, the failure rate is specifically:

[0070] If the product life follows an exponential distribution, the formula for calculating the product failure rate is:

[0071]

[0072] Among them, R1, R n , R 1-N They represent the reliability of the first task, the reliability of the nth task, and the reliability of completing N tasks respectively; λ represents the product failure rate, and t0 represents the single task time.

[0073] Preferably, the characteristic lifespan is specifically:

[0074] If the product life follows the Weibull distribution, the formula for calculating the characteristic life of the product is:

[0075]

[0076] Among them, t0 is the single task time, θ is the product scale parameter or characteristic life, m is the shape parameter, R1, R n , R 1-NThey are the reliability of the first task, the reliability of the nth task, and the reliability of completing N tasks respectively.

[0077] Preferably, the test time is specifically:

[0078] For the test time of the power redundancy system, the calculation formula is:

[0079]

[0080] Among them, R g2 is the reliability of the engine when it operates at a thrust higher than the rated thrust, R g1 is the reliability when working at rated thrust; t i , t′ i represents the total test time of a single engine for reliability test at rated thrust and overrated thrust respectively, N and N′ are the corresponding number of test units; γ is the confidence level; K is the environmental factor, indicating that the test time at overrated thrust is equivalent to K times the test time at rated thrust; m is the shape parameter; r represents the total number of failures occurring during the test; t0 is the single mission time.

[0081] Preferably, the test time is specifically:

[0082] For products with exponential life distribution, the total test time formula is:

[0083]

[0084] Where T represents the total test time, λ represents the failure rate distribution value, represents χ with 2r+2 degrees of freedom 2 The gamma quantile of the distribution, r, represents the total number of failures that occurred during the test.

[0085] Preferably, the test time is specifically:

[0086] For products whose life follows the Weibull distribution, the test time formula is:

[0087] The calculation formula for the test time of the first task is:

[0088] The calculation formula for the test time after completing N tasks is:

[0089] Among them, t i is the cumulative test time of the i-th product, n is the number of test products, t0 is the single task time, R1, R n , R 1-N They are the reliability of the first mission, the reliability of the nth mission, and the reliability of completing N missions, respectively. m is the shape parameter, and r is the total number of failures that occurred during the test.

[0090] Preferably, the reliability is specifically:

[0091] For products whose lifespan follows an exponential distribution, the reliability evaluation formula is:

[0092]

[0093] R 1-N =R N

[0094] Among them, t0 is the single task time, represents χ with 2r+2 degrees of freedom 2 The gamma quantile of the distribution, T is the total trial time, and N is the number of trials.

[0095] Preferably, the reliability is specifically:

[0096] For products whose life follows the Weibull distribution, the reliability calculation formula is:

[0097]

[0098] Among them, t0 is the single task time, represents χ with 2r+2 degrees of freedom 2 Distribution gamma quantile, t i is the cumulative test time of the i-th product, t i is the total test time of a single engine for reliability test according to rated thrust; m is the shape parameter, N is the number of test units; R1, R n , R 1-N They are the reliability of the first task, the reliability of the nth task, and the reliability of completing N tasks respectively.

[0099] Preferably, the reliability is specifically:

[0100] The reliability R of the engine in the power redundancy system when working at rated thrust g1 , reliability R when working at over rated thrust g2 , the calculation formula is:

[0101]

[0102] Among them, t0 is the single task time, represents χ with 2r+2 degrees of freedom 2 Distribution gamma quantile, t i is the total test time of the i-th single engine for reliability test according to rated thrust; t′2 is the total test time of the single engine for reliability test according to over-rated thrust; m is the shape parameter, and N and N′ are the corresponding number of test units.

[0103] Example

[0104] like Figure 1 As shown, the present invention provides a reliability index allocation, verification and evaluation method based on reuse and power redundancy, comprising the following steps:

[0105] 1. Reliability Index Allocation

[0106] 1) Considering the reliability index allocation of reuse

[0107] If the rocket / product is reused N times, the reliability requirements for the rocket / product are generally stated in the following three ways: the reliability of the first mission, the reliability of the nth mission, and the reliability of completing N missions. It should be noted that the above indicators are not independent, and they all reflect the reliability level of each product. There is an inevitable mathematical relationship. When allocating indicators, only one indicator can be proposed, and multiple indicators should not be proposed.

[0108] The reliability of products with exponential life distribution is as follows:

[0109]

[0110] That is, the following relationship exists:

[0111]

[0112] Where: R1, R n , R 1-N They represent the reliability of the first task, the reliability of the nth task, and the reliability of completing N tasks respectively; λ represents the product failure rate, and t0 represents the single task time. It is assumed that the task time is the same for each task.

[0113] The relationship between the reliability indicators of products whose life follows Weibull distribution is as follows:

[0114]

[0115] Where: θ represents the product size parameter or characteristic life, and m represents the shape parameter.

[0116] If multiple indicators need to be proposed, the quantitative relationship between the indicators should be considered to avoid contradictions between the indicators.

[0117] 2) Reliability index allocation considering power redundancy

[0118] If the rocket has power redundancy, that is, when the rocket electrical system detects that an engine has failed, it can actively shut down the engine, and take measures such as increasing the working time of other engines and improving the working thrust of other engines to enable the rocket to complete the scheduled mission. At this time, when allocating indicators to the various systems of the rocket, it should be based on Figure 1 The steps shown are as follows:

[0119] The first step is to use the traditional method to build a reliability block diagram using the series-parallel model.

[0120] The second step is to allocate the indicators to each system and then to each single machine.

[0121] The third step is to use the redundancy reliability block diagram of the rocket propulsion system, which is generally a voting system, that is, a system where K out of N identical engines are selected, and generally K = N-1, indicating that only one engine can be allowed to fail. The actual reliability level of the rocket is checked, and the reliability of the propulsion system is calculated as follows:

[0122]

[0123] Where: R g1 It indicates the reliability of a single engine at rated thrust and rated working time. It should be noted that when an engine is shut down, the remaining engines will generally operate at a higher thrust or rated working time, and the engine reliability will be reduced. In this formula, R g2 When performing preliminary reliability index allocation or when there is not much data to calculate, it can be simplified to R g2 =R g1 . R g3 It indicates the reliability of the engine when it works to the moment when failure is allowed. This is related to the overall design plan of rocket power redundancy. The earlier the engine failure is allowed, the higher the rocket reliability level.

[0124] Step 4. After completing step 3, the rocket reliability index obtained will be higher than the specified value of the index. You can return to step 2, appropriately lower the product indexes with higher index allocation values, and then repeat the above steps.

[0125] By adopting this method, the reliability indicators of some products can be reduced, thus achieving the purpose of saving testing funds.

[0126] 2. Reliability Verification

[0127] For products whose lifespan follows an exponential distribution, no matter the reliability of the first mission, the reliability of the nth mission, or the reliability of completing N missions is assigned, the requirements for the product failure rate λ index should be the same, and the test can be planned according to the following formula:

[0128]

[0129] Where: T represents the total test time, λ represents the failure rate distribution value, represents χ with 2r+2 degrees of freedom 2 The gamma quantile of the distribution, r, represents the total number of failures that occurred during the test.

[0130] For products whose lifespan follows the Weibull distribution, since they are life-weary products, the more missions they go through, the lower the reliability of the next mission will be. If the indicator proposed for the product is the reliability of the first mission, or the reliability of completing N missions, the test is planned according to the following formula:

[0131]

[0132] Where: t i It represents the cumulative test time of the i-th product, and n represents the number of tested products.

[0133] If the indicator proposed for the product is the reliability of the nth mission, when the test is planned according to the above formula, t i It should not include the first n-1 tasks that the product has experienced, and the cumulative test time should be subtracted from the previous task time, that is, (n-1)t0.

[0134] When considering power redundancy, the reliability R of the engine when operating at a thrust higher than the rated thrust is g2 , can be combined with its reliability R when working at rated thrust g1 Let’s verify it together as follows:

[0135]

[0136] Where: t i , t′ i represents the total test time of a single engine for reliability test at rated thrust and over-rated thrust respectively, N and N′ are the corresponding number of test units; γ is the confidence level; K is the environmental factor, indicating that the test time at over-rated thrust is equivalent to K times the test time at rated thrust.

[0137] 3. Reliability Assessment

[0138] For products whose lifespan follows an exponential distribution, the reliability of the first or nth mission is the same and is evaluated as follows:

[0139]

[0140] The reliability of completing N tasks is evaluated as follows:

[0141] R 1-N =R N

[0142] For products whose service life follows the Weibull distribution, the reliability of each task is calculated as follows:

[0143]

[0144] The reliability of the engine at rated thrust is R g1 , reliability R when working at over rated thrust g2 , calculated as follows:

[0145]

[0146] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

[0147] The contents not described in detail in the specification of the present invention belong to the common knowledge of the professionals in this field.

Claims

1. A reliability index allocation, verification and evaluation method based on reuse and power redundancy, characterized in that: include: S1. Allocate reliability indexes for each product to obtain the reliability index of each product; S2. Calculate the system reliability of the power redundancy system based on the reliability index of each product; S3, judging whether the allocation result meets the requirements according to the system reliability and index requirements, if so, proceeding to step S4, if not, returning to step S1; S4. Calculate the failure rate or characteristic life according to the reliability index of each product; S5. Calculate the test time based on the failure rate or characteristic life; S6. Carry out reliability tests according to the test time and count the total number of failures; S7. Calculate the reliability based on the total number of failures to evaluate the reliability of the product.

2. The reliability index allocation, verification and evaluation method based on reuse and power redundancy according to claim 1 is characterized in that: The system reliability of the power redundancy system is specifically: Among them, R g1 is the reliability of a single engine at rated thrust and rated working time, R g2 R is the reliability of a single engine when it operates beyond the rated thrust or exceeds the rated operating time. g3 It is the reliability of the engine when it works to the moment when failure is allowed; N is the number of identical engines in the system, and K is the minimum number of engines required to work normally in the power system.

3. The reliability index allocation, verification and evaluation method based on reuse and power redundancy according to claim 1 is characterized in that: The failure rate is specifically: If the product life follows an exponential distribution, the formula for calculating the product failure rate is: Among them, R1, R n , R 1-N They represent the reliability of the first task, the reliability of the nth task, and the reliability of completing N tasks respectively; λ represents the product failure rate, and t0 represents the single task time.

4. The reliability index allocation, verification and evaluation method based on reuse and power redundancy according to claim 1 is characterized in that: The characteristic lifespan is specifically: If the product life follows the Weibull distribution, the formula for calculating the characteristic life of the product is: Among them, t0 is the single task time, θ is the product scale parameter or characteristic life, m is the shape parameter, R1, R n , R 1-N They are the reliability of the first task, the reliability of the nth task, and the reliability of completing N tasks respectively.

5. The reliability index allocation, verification and evaluation method based on reuse and power redundancy according to claim 1 is characterized in that: The test time is specifically: For the test time of the power redundancy system, the calculation formula is: Among them, R g2 is the reliability of the engine when it operates at a thrust higher than the rated thrust, R g1 is the reliability when working at rated thrust; t i ,t i ′ represents the total test time of a single engine for reliability test at rated thrust and overrated thrust respectively, N and N′ are the corresponding number of test units; γ is the confidence level; K is the environmental factor, indicating that the test time at overrated thrust is equivalent to K times the test time at rated thrust; m is the shape parameter; r represents the total number of failures occurring during the test; t0 is the single mission time.

6. The reliability index allocation, verification and evaluation method based on reuse and power redundancy according to claim 1 is characterized in that: The test time is specifically: For products with exponential life distribution, the total test time formula is: Where T represents the total test time, λ represents the failure rate distribution value, represents χ with 2r+2 degrees of freedom 2 The gamma quantile of the distribution, r, represents the total number of failures that occurred during the test.

7. The reliability index allocation, verification and evaluation method based on reuse and power redundancy according to claim 1 is characterized in that: The test time is specifically: For products whose life follows the Weibull distribution, the test time formula is: The calculation formula for the test time of the first task is: The calculation formula for the test time after completing N tasks is: Among them, t i is the cumulative test time of the i-th product, n is the number of test products, t0 is the single task time, R1, R n , R 1-N They are the reliability of the first mission, the reliability of the nth mission, and the reliability of completing N missions, respectively. m is the shape parameter, and r is the total number of failures that occurred during the test.

8. The reliability index allocation, verification and evaluation method based on reuse and power redundancy according to claim 1 is characterized in that: The reliability is specifically: For products whose lifespan follows an exponential distribution, the reliability evaluation formula is: R 1-N =R N Among them, t0 is the single task time, represents χ with 2r+2 degrees of freedom 2 The gamma quantile of the distribution, T is the total trial time, and N is the number of trials.

9. The reliability index allocation, verification and evaluation method based on reuse and power redundancy according to claim 1 is characterized in that: The reliability is specifically: For products whose life follows the Weibull distribution, the reliability calculation formula is: Among them, t0 is the single task time, represents χ with 2r+2 degrees of freedom 2 Distribution gamma quantile, t i is the cumulative test time of the i-th product, t i is the total test time of a single engine for reliability test according to rated thrust; m is the shape parameter, N is the number of test units; R1, R n , R 1-N They are the reliability of the first task, the reliability of the nth task, and the reliability of completing N tasks respectively.

10. The reliability index allocation, verification and evaluation method based on reuse and power redundancy according to claim 1 is characterized in that: The reliability is specifically: The reliability R of the engine in the power redundancy system when working at rated thrust g1 , reliability R when working at over rated thrust g2 , the calculation formula is: Among them, t0 is the single task time, represents χ with 2r+2 degrees of freedom 2 Distribution gamma quantile, t i is the total test time of the i-th single engine for reliability test according to rated thrust; t2′ is the total test time of the single engine for reliability test according to over-rated thrust; m is the shape parameter, and N and N′ are the corresponding number of test units.

Images