Reliability and MTBF analysis method of tri-redundancy flight control system

Abstract

The invention belongs to the technical field of civil aircraft flight control system verification, and particularly relates to a reliability and MTBF analysis method of a three-redundancy flight control system. Comprising the following steps: step 1, constructing an integrated formalized model of a three-redundancy flight control system and a fault; 2, constructing a single-point fault statistical mathematical model based on the integration formalized model of the three-redundancy flight control system and the fault, and integrating the integration formalized model and the single-point fault statistical mathematical model into a three-redundancy flight control system model; 3, analyzing the three-redundancy flight control system model by adopting a statistical model test method to obtain the reliability of the three-redundancy flight control system model; and 4, setting different system operation times and single-point fault occurrence probabilities, and executing the step 3 for multiple times to obtain the reliability under different system operation times and fault occurrence probabilities, namely MTBF.

Description

Technical Field

[0001] The present invention belongs to the technical field of civil aircraft flight control system verification, and in particular relates to a reliability and MTBF analysis method for a triple-redundant flight control system. Background Art

[0002] The triple-redundant flight control system distributes flight control function master / backup decisions and fault handling across three flight control computers and four flight control actuators to achieve system reliability. Therefore, these seven components and their associated bus transmissions must agree on the system's master / backup decisions, such as which flight control computer is currently the master. Internal failures within a triple-redundant flight control system are frequent and random, and the seven components operate on independent clocks. Consequently, the diverse combinations of system failures and the asynchronous nature of the components can lead to the possibility of concurrent failures and clock asynchrony.

[0003] Traditional system reliability and MTBF analysis methods are highly subjective and are generally calculated based on formulas according to the connection status of system components. However, for triple-redundant flight control systems with dynamic reconstruction characteristics, fault timing correlation, and logic correlation, the comprehensiveness and accuracy of calculation and analysis based on formulas are difficult to guarantee. However, if sufficient reliability and MTBF analysis cannot be performed on the triple-redundant flight control system, it will be difficult to meet the airworthiness confidence review of the flight control system. Summary of the Invention

[0004] Purpose of the invention: To provide a reliability and MTBF analysis method for a triple-redundant flight control system to improve the comprehensiveness and accuracy of the analysis.

[0005] Technical solution:

[0006] A reliability and MTBF analysis method for a triple-redundant flight control system includes:

[0007] Step 1: Construct an integrated formal model of the triple-redundant flight control system and its faults;

[0008] Step 2: Based on the integrated formal model of the triple-redundant flight control system and faults, a single-point fault statistical mathematical model is constructed, and the integrated formal model and the single-point fault statistical mathematical model are combined into a triple-redundant flight control system model;

[0009] Step 3: Analyze the triple-redundant flight control system model using the statistical model testing method to obtain the reliability of the triple-redundant flight control system model;

[0010] Step 4: Set different system operating times and single-point failure probabilities, and perform step 3 multiple times to obtain the reliability under different system operating times and failure probabilities, that is, MTBF.

[0011] Preferably, step 1 is specifically:

[0012] Firstly, a formal model of the triple-redundant flight control system is constructed based on its characteristics and functions;

[0013] Then, a formal model of the fault is constructed based on the type and characteristics of the fault;

[0014] Finally, the formal model of the fault is injected into the formal model of the triple-redundant flight control system to form an integrated formal model.

[0015] Preferably, in step 2, a single point failure statistical mathematical model is constructed, specifically:

[0016] First, analyze the type of single point failure, including whether it is an LRU damage failure or a random failure;

[0017] Then, a fault statistical mathematical model is constructed based on the single-point fault type and the statistical model verification modeling semantics of timed automata. If the single-point fault type is an LRU damage fault, its probability distribution is an exponential distribution. If the single-point fault type is a random fault, its probability distribution is a proportional distribution. The parameters of the exponential distribution and the proportion of the proportional distribution are specified according to the statistical model verification modeling semantics of timed automata.

[0018] Preferably, step 3 includes: analyzing the reliability of the triple-redundant flight control system based on a probability estimation method, or analyzing the reliability of the triple-redundant flight control system based on a hypothesis testing method.

[0019] Preferably, in step 3, when analyzing the reliability of the triple-redundant flight control system based on the probability estimation method, first, the confidence interval width and confidence level of the probability estimation are determined based on the reliability analysis indicators; then, based on the confidence interval width and confidence level, a sequential sampling method is used to perform Monte Carlo simulation and statistical model testing on the triple-redundant flight control system model to obtain a reliability probability estimate of the triple-redundant flight control system, wherein the confidence interval width and confidence level are set according to the formal verification semantics of the timed automaton.

[0020] Preferably, in step 3, when analyzing the reliability of the triple-redundant flight control system based on the hypothesis testing method, first, the threshold of the hypothesis test, the maximum probability of the first type error, and the maximum probability of the second type error are determined based on the reliability analysis indicators; then, based on the threshold of the hypothesis test, the maximum probability of the first type error, and the maximum probability of the second type error, a sequential sampling method is used to perform Monte Carlo simulation and statistical model testing on the triple-redundant flight control system model to obtain a comparative conclusion between the reliability of the triple-redundant flight control system and the threshold, wherein the threshold of the hypothesis test, the maximum probability of the first type error, and the maximum probability of the second type error are set according to the formal verification semantics of the timed automaton.

[0021] Preferably, in step 4, if the system reliability is less than the MTBF index, it means that under this system operating time and single-point failure probability, the probability of failure of the triple-redundant flight control system is higher than expected, then the system operating time is reduced or the probability of single-point failure is reduced, and the reliability of the triple-redundant flight control system is re-analyzed until the system MTBF meets expectations. The system operating time and single-point failure probability at this time are used as reference indicators for system designers.

[0022] Preferably, the method further includes: returning the system running time that satisfies the system MTBF and the probability of single point failure.

[0023] Beneficial effects:

[0024] The technical solution provided by the embodiment of the present invention uses a fault formal modeling and verification method for a triple-redundant flight control system, and utilizes statistical methods and Monte Carlo simulation to simulate various asynchronous clock trigger timings and staggered execution sequences of the triple-redundant flight control system, thereby ensuring the reliability of the system design; specifically, it has the following beneficial effects: 1. It reduces the cost of system experiments; 2. It provides sufficient evidence for airworthiness confidence review; 3. It is highly versatile and can be applied to analysis methods of similar systems in other fields; 4. It returns the system operating time that meets the system MTBF and the probability of single-point failure to system designers and component procurement personnel, thereby assisting system design and component procurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions implemented in the present invention, the following briefly explains the drawings required for the description of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.

[0026] Figure 1 A schematic diagram of analyzing the reliability and MTBF of a triple-redundant flight control system based on a statistical model checking method provided by an embodiment of the present invention.

[0027] Figure 2 A schematic diagram of the principle of constructing a single-point failure statistical mathematical model provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0028] To make the purpose, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that, unless there is a conflict, the embodiments and features in the embodiments of the present application can be combined with each other in any manner.

[0029] As explained in the above background technology, the reliability and MTBF analysis of triple-redundant flight control systems is highly subjective, and is generally calculated based on formulas according to the connection status of system components. However, for triple-redundant flight control systems with dynamic reconfiguration characteristics, fault timing correlation, and logic correlation, the comprehensiveness and accuracy of calculation and analysis based on formulas are difficult to guarantee. However, if sufficient reliability and MTBF analysis of the triple-redundant flight control system cannot be performed, it will be difficult to meet the airworthiness confidence review of the flight control system.

[0030] The technical solution provided by the embodiment of the present invention uses a formal fault modeling and verification method for a triple-redundant flight control system, and utilizes statistical methods and Monte Carlo simulation to simulate the various asynchronous clock trigger timings and interleaved execution sequences of the triple-redundant flight control system, thereby ensuring the reliability of the system design; reducing the cost of system experiments; and providing sufficient evidence for airworthiness confidence review. The solution is highly versatile and can be applied to the analysis of similar systems in other fields.

[0031] The present invention provides the following specific embodiments that can be combined with each other. The same or similar concepts or processes may not be described in detail in some embodiments.

[0032] This method has the characteristics of strong design operability and good analysis effect, and can greatly improve the reliability of the triple-redundant flight control system and the effect of MTBF analysis.

[0033] The following is a schematic illustration of the reliability and MTBF analysis method of a triple-redundant flight control system based on a timed automaton provided by the present invention through specific examples.

[0034] like Figure 1 The reliability and MTBF analysis method of the triple-redundant flight control system based on statistical model testing of the present invention includes the following steps:

[0035] Step 1: Construct an integrated formal model of the triple-redundant flight control system and its faults;

[0036] Step 2: Based on the integrated formal model of the triple-redundant flight control system and the fault, a single-point fault statistical mathematical model is constructed, and the integrated formal model and the single-point fault statistical mathematical model are integrated into a triple-redundant flight control system model;

[0037] Step 3: Analyze the triple-redundant flight control system model using a statistical model testing method to obtain the reliability of the triple-redundant flight control system model;

[0038] Step 4: Set different system operating times and single point failure probability, and execute step 3 multiple times to obtain the reliability under different system operating times and failure probability, that is, MTBF.

[0039] Specifically, in step 1, a formalized model of triple-redundant flight control system and fault integration is constructed as follows:

[0040] First, a formal model of the triple-redundant flight control system is constructed based on its characteristics and functions. Then, a formal model of faults is constructed based on the types and characteristics of faults. Finally, the formal model of faults is injected into the formal model of the triple-redundant flight control system to form an integrated formal model.

[0041] Specifically, in step 2, refer to Figure 2 ,Construct a single point failure statistical mathematical model, specifically: First, analyze the type of single point failure, including whether it is an LRU damage failure or a random failure, and then construct a fault statistical mathematical model based on the single point failure type and the statistical model verification modeling semantics of the timed automaton. Figure 2 As shown in the figure, if the single point fault type is LRU damage fault, its probability distribution is exponential distribution. If the single point fault type is random fault, its probability distribution is proportional distribution. The parameters of exponential distribution and the proportion of proportional distribution can be specified according to the statistical model verification modeling semantics of timed automata.

[0042] Specifically, if Figure 1 In step 3, the statistical model testing method is used to analyze the triple-redundant flight control system model to obtain the reliability of the triple-redundant flight control system model, specifically:

[0043] The reliability of the triple-redundant flight control system can be analyzed based on the probability estimation method or the hypothesis testing method.

[0044] When analyzing the reliability of a triple-redundant flight control system using a probability estimation approach, the confidence interval width and confidence level of the probability estimate are first determined based on the reliability analysis indicators. Then, based on the confidence interval width and confidence level, a sequential sampling method is used to perform Monte Carlo simulation and statistical model testing on the triple-redundant flight control system model to obtain a probability estimate of the reliability of the triple-redundant flight control system. The confidence interval width and confidence level can be set based on the formal verification semantics of timed automata.

[0045] When analyzing the reliability of a triple-redundant flight control system based on hypothesis testing, the following steps are performed: first, the hypothesis testing threshold, the maximum probability of type 1 error, and the maximum probability of type 2 error are determined based on the reliability analysis indicators. Then, based on the hypothesis testing threshold, the maximum probability of type 1 error, and the maximum probability of type 2 error, a sequential sampling method is used to perform Monte Carlo simulation and statistical model testing on the triple-redundant flight control system model to obtain a comparative conclusion between the reliability of the triple-redundant flight control system and the threshold. The hypothesis testing threshold, the maximum probability of type 1 error, and the maximum probability of type 2 error can be set based on the formal verification semantics of timed automata.

[0046] Specifically, if the system reliability in step 4 is less than the MTBF index, it means that the probability of failure of the triple-redundant flight control system is higher than expected under this system operation time and single-point failure probability. In this case, the system operation time is reduced or the probability of single-point failure is reduced, and the reliability of the triple-redundant flight control system is re-analyzed until the system MTBF meets expectations. The system operation time and single-point failure probability at this time serve as reference indicators for system designers.

[0047] The system operating time and probability of single-point failure that meet the system MTBF are returned to system designers and component purchasers to assist system design and component purchase.

[0048] In some possible implementations of the embodiments of the present invention, the specified reliability and MTBF analysis method of the triple-redundant flight control system based on statistical model checking is all tools that can support model checking based on probability modeling and statistical model.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should all be covered by the scope of protection of the present invention.

Claims

1. A reliability and MTBF analysis method for a triple-redundant flight control system, characterized in that: include: Step 1: Construct an integrated formal model of the triple-redundant flight control system and its faults; Step 2: Based on the integrated formal model of the triple-redundant flight control system and faults, a single-point fault statistical mathematical model is constructed, and the integrated formal model and the single-point fault statistical mathematical model are combined into a triple-redundant flight control system model; Step 3: Analyze the triple-redundant flight control system model using the statistical model testing method to obtain the reliability of the triple-redundant flight control system model; Step 4: Set different system operating times and single-point failure probabilities, and perform step 3 multiple times to obtain the reliability under different system operating times and failure probabilities, that is, MTBF.

2. The method according to claim 1, characterized in that Step 1, specifically: Firstly, a formal model of the triple-redundant flight control system is constructed based on its characteristics and functions; Then, a formal model of the fault is constructed based on the type and characteristics of the fault; Finally, the formal model of the fault is injected into the formal model of the triple-redundant flight control system to form an integrated formal model.

3. The method according to claim 1, characterized in that In step 2, a single point failure statistical mathematical model is constructed, specifically: First, analyze the type of single point failure, including whether it is an LRU damage failure or a random failure; Then, a fault statistical mathematical model is constructed based on the single-point fault type and the statistical model verification modeling semantics of timed automata. If the single-point fault type is an LRU damage fault, its probability distribution is an exponential distribution. If the single-point fault type is a random fault, its probability distribution is a proportional distribution. The parameters of the exponential distribution and the proportion of the proportional distribution are specified according to the statistical model verification modeling semantics of timed automata.

4. The method according to claim 1, wherein Step 3 includes: analyzing the reliability of the triple-redundant flight control system based on a probability estimation method, or analyzing the reliability of the triple-redundant flight control system based on a hypothesis testing method.

5. The method according to claim 1, wherein In step 3, when analyzing the reliability of the triple-redundant flight control system based on the probability estimation method, first, the confidence interval width and confidence level of the probability estimation are determined based on the reliability analysis indicators; then, based on the confidence interval width and confidence level, the triple-redundant flight control system model is subjected to a sequential sampling method, Monte Carlo simulation and statistical model testing are performed to obtain the reliability probability estimation of the triple-redundant flight control system, where the confidence interval width and confidence level are set according to the formal verification semantics of the timed automaton.

6. The method according to claim 1, characterized in that In step 3, when analyzing the reliability of the triple-redundant flight control system based on the hypothesis testing method, first, the threshold of the hypothesis test, the maximum probability of type 1 error, and the maximum probability of type 2 error are determined based on the reliability analysis indicators; then, based on the threshold of the hypothesis test, the maximum probability of type 1 error, and the maximum probability of type 2 error, the triple-redundant flight control system model is subjected to a sequential sampling method, Monte Carlo simulation and statistical model testing are performed to obtain a comparative conclusion between the reliability of the triple-redundant flight control system and the threshold, wherein the threshold of the hypothesis test, the maximum probability of type 1 error, and the maximum probability of type 2 error are set according to the formal verification semantics of the timed automaton.

7. The method according to claim 1, characterized in that In step 4, if the system reliability is less than the MTBF index, it means that the probability of failure of the triple-redundant flight control system is higher than expected under this system operation time and single-point failure probability. In this case, reduce the system operation time or reduce the probability of single-point failure, and re-analyze the reliability of the triple-redundant flight control system until the system MTBF meets expectations. The system operation time and single-point failure probability at this time serve as reference indicators for system designers.

8. The method according to claim 1, characterized in that Also includes: Returns the system uptime and probability of single point failure that meets the system MTBF.

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