A diesel engine reliability evaluation method based on repairable dynamic fault tree

Abstract

The application discloses a diesel engine reliability evaluation method based on a repairable dynamic fault tree, which simultaneously considers the maintenance and fault dynamic characteristics of a diesel engine system when modeling the reliability of the diesel engine system, adopts a repairable dynamic fault tree, is designed based on a repairable system probability state transition model, can simultaneously consider the maintenance and fault dynamic characteristics of a Markov type repairable system, and has the advantages of short running time, simple analysis steps and the like.In addition, the application adopts a Markov model to deduce a quantitative calculation formula, and finally can obtain a transient availability change curve of the diesel engine system, so as to obtain quantitative analysis of the reliability of the system, and two kinds of qualitative analysis of the reliability of the minimum cut set of the fault tree and the maintenance importance of the components.According to the qualitative analysis result, the maintenance importance of the components is calculated again by using a multi-criteria compromise solution sequencing method, the weak link of the diesel engine electronic control system is judged through comprehensive analysis, and therefore more accurate guidance is provided for the design and maintenance of a new diesel engine system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of diesel engine reliability analysis, and particularly relates to a diesel engine reliability evaluation method based on a repairable dynamic fault tree. BACKGROUND

[0002] The diesel engine for vehicle is mainly used in the transportation industry and is the main motive power of heavy vehicles. When selecting the diesel engine for heavy vehicles, various factors are considered, some of which include the reliability and availability of the engine, the maintenance and installation cost of the engine, and the operation cost of the engine. However, the operation and maintenance cost of each diesel engine is very important in the operation of the vehicle. This is the reason why transportation companies are committed to developing and improving the performance of the engine to adapt to the operation and optimize the performance of the engine. Improving the performance of the engine is the key to ensuring the best results during use and timely predicting failures to prolong the service life of the vehicle. Therefore, it is necessary to focus on improving the reliability of the engine of the vehicle.

[0003] The most effective means to improve the reliability of the diesel engine is to introduce the reliability concept in the design stage of the diesel engine, and to achieve the effect of preventing problems from occurring by performing corresponding reliability calculation and analysis (reducing the cost in the manufacturing process of the product and improving the reliability of the product in the whole life cycle). Therefore, improving the reliability of the diesel engine system can avoid significant personnel casualties and economic losses caused by system reliability problems.

[0004] When modeling the dynamic fault tree of the repairable system, the availability calculated by the dynamic fault tree considering only the failure rate is not accurate. For example, in practice, in order to improve the reliability of the repairable system, a maintenance strategy is usually used to maintain the repairable system to improve the service life of the repairable system. It is assumed that the repairable system is composed of a plurality of components and a plurality of repair devices. The repair devices repair the components that have failed, and the repaired components can continue to work normally. At this time, the reliability analysis of the repairable system by the dynamic fault tree considering only the failure rate will have a large error and is not of reference value.

[0005] In the prior art, for the reliability analysis of the repairable system such as the diesel engine system, a dynamic fault tree of a repairable dynamic fault tree is generally constructed by using the time operator minimal cut set numerical solution method. The time operator minimal cut set and its sequential failure region are coupled, and the Monte Carlo simulation method is used to obtain the quantitative analysis result of the repairable dynamic fault tree. However, the minimal cut sequence set is susceptible to the influence of the simulation times and random fluctuations when the Monte Carlo simulation method is used to solve it, and the calculation time is too long, which reduces the availability of the dynamic fault tree of the repairable dynamic fault tree.

[0006] Therefore, in the case of the above prior art and defects, the accuracy of the diesel engine reliability evaluation still needs to be continuously improved. SUMMARY

[0007] The present application aims to provide a diesel engine reliability evaluation method based on a repairable dynamic fault tree, which solves the problem of inaccurate diesel engine reliability evaluation in the prior art; the method can ensure that the dynamic fault tree can consider the repair rate and failure rate at the same time when analyzing the reliability of the diesel engine system, thereby improving the accuracy of the quantitative calculation of the repairable dynamic fault tree of the diesel engine and providing a reference for the growth of the reliability of the diesel engine system throughout the life cycle.

[0008] To achieve the above object, the technical scheme adopted by the present application is as follows:

[0009] The present application provides a diesel engine reliability evaluation method based on a repairable dynamic fault tree, comprising the following steps:

[0010] S1, analyzing the principle and structure of the diesel engine system to determine the top event of the repairable dynamic fault tree;

[0011] S2, based on the top event of the repairable dynamic fault tree, using Markov repairable system to derive a quantitative calculation formula of the repairable dynamic fault tree;

[0012] S3, determining the failure rate and repair rate of each component in the diesel engine system: determining the repair and failure logic relationship between components, using a direct algorithm and using the derived quantitative calculation formula of the repairable dynamic fault tree to obtain the transient availability of the top event of the repairable dynamic fault tree;

[0013] S4, using a time operator to describe the failure timing logic, expressing the failure behavior of the logic gate of the repairable dynamic fault tree, using a time operator structure function to process the top event of the repairable dynamic fault tree, and obtaining the minimal cut set of the repairable fault tree;

[0014] S5, calculating the structure importance of the repairable dynamic fault tree;

[0015] S6, based on the minimal cut set of the repairable fault tree and the structure importance of the repairable dynamic fault tree, using a multi-criteria compromise solution sorting method to calculate the component repair importance;

[0016] S7, based on the transient availability of the top event of the repairable dynamic fault tree and the component repair importance, analyzing and evaluating the diesel engine system.

[0017] Further, the step S1 comprises:

[0018] S11, using the diesel engine electronic control system to monitor the real-time running state of the diesel engine oil;

[0019] S12, regarding the diesel engine electric control system as a series unit of the diesel engine, selecting a diesel engine electric control system fault as a repairable dynamic fault tree top event.

[0020] Further, the step S2 comprises: obtaining a failure logic state transition graph by combining a Markov repairable system and a fault tree analysis method; and deriving a quantitative calculation formula of the repairable dynamic fault tree according to the failure logic state transition graph.

[0021] The derived quantitative calculation formula of the repairable dynamic fault tree specifically comprises:

[0022] S21, deriving an OR logic gate quantitative calculation formula;

[0023] S22, deriving an AND logic gate quantitative calculation formula;

[0024] S23, deriving a cold standby logic gate quantitative calculation formula;

[0025] S24, deriving a function logic gate quantitative calculation formula;

[0026] S25, deriving a hot standby logic gate quantitative calculation formula.

[0027] Further, the step S3 comprises:

[0028] S31, determining a repair rate of each component in the diesel engine system: establishing a repairable component state transition matrix, and obtaining an availability of the repairable component at time t by state transition;

[0029] S32, determining a failure rate of each component in the diesel engine system: using a direct algorithm and utilizing the derived quantitative calculation formula of the repairable dynamic fault tree, to obtain a transient availability of the repairable dynamic fault tree top event.

[0030] Further, in the step S4, a time operator is used to describe a failure timing logic, comprising: using a time operator rule to describe a failure behavior of the repairable dynamic fault tree, and the specific basic rules are as follows:

[0031] Rule 1: represents OR logic, and represents AND logic;

[0032] Rule 2: X1 < X2 represents that components X1 and X2 fail at the same time;

[0033] Rule 3: represents that component X1 fails before component X2, and the rule contains dynamic failure logic;

[0034] Rule 4: This indicates that component X1 fails before component X2, and this rule does not contain dynamic failure logic.

[0035] Furthermore, in step S4, the failure behavior of the repairable dynamic fault tree logic gate is described, including:

[0036] Assuming there are repairable components X1 and X2, the OR gate timing operator expression is:

[0037] The AND gate time operator expression is: T AND =X1⊙X2;

[0038] Assuming there are repairable components X1 and X2, and X1 fails before X2, the priority AND gate timing operator expression is as follows:

[0039] Assuming there are repairable components X1 and X2, where X2 is a spare component for X1, and X2 was not activated before X1 failed, then the cold standby time operator expression is:

[0040] Assuming there are repairable components X1 and X2, where X2 is a backup component of X1, and X2 was activated before X1 failed, then the hot standby gate time operator expression is T. HSP =X1⊙X2;

[0041] Assuming there are repairable components X, X1, and X2, and the failure of X causes the failure of X1 and X2, then the function gate timing operator expression is:

[0042] Furthermore, in step S4:

[0043] The time operator structure function is: In the formula, CSS r It is a cut set;

[0044] The formula for calculating the minimum cut set is:

[0045]

[0046] In the above formula, TE_min q For the minimum cut set, assuming r = 1 initially, the minimum cut set calculation formula iterates q times until TE_min is reached. q Not satisfied r represents the component index value; h represents the number of iterations in the minimum cut set calculation formula.

[0047] Further, in step S5, calculating the importance of the repairable dynamic fault tree structure includes:

[0048] Assuming the state of the bth component X changes from 0 to 1, the state change of the diesel engine system is Q b (X);

[0049] The structural importance of the component is:

[0050] In the formula, a represents the number of cut sequences.

[0051] Further, in the step S6, the component maintenance importance is calculated by using a multi-criteria compromise solution ranking method, comprising: setting v df is an evaluation index, d is the component sequence number, and f is the evaluation index sequence number.

[0052] According to the actual situation of the diesel engine system, the unit component importance v 1f , the maintenance rate v 2f , the maintenance cost v 3f , and the occurrence frequency v 4f are selected as the evaluation indexes of the maintenance importance; wherein v 3f and v 4f index scores are obtained by expert scoring;

[0053] The structural importance of each component obtained in step S5 is substituted into the unit component importance;

[0054] A decision matrix D is established:

[0055]

[0056] In the above formula, v 11 , v 12 ,...v df are evaluation indexes, respectively corresponding to the fth evaluation index in the component with sequence number d;

[0057] The v df in the above formula is substituted into the following formula for standardization:

[0058] p is the number of components participating in evaluation, and g is the number of participating evaluation;

[0059] The standardized decision matrix r df is obtained;

[0060] The positive ideal solution r + and the negative ideal solution r - of each evaluation index are calculated:

[0061]

[0062]

[0063] F is the minimum value of the evaluation index sequence number, and F' is the maximum value of the evaluation index sequence number.

[0064] S d The absolute value of the positive and negative ideal solution is calculated by the following formula, and the distance ratio R of the positive and negative ideal solution of each component is calculated d :

[0065]

[0066]

[0067] l is the number of evaluation indexes, w df is the weight of the centrality criterion of the evaluation index with the sequence number f in the dth component;

[0068] The benefit ratio v is calculated d is the decision mechanism coefficient of the majority criterion strategy of the dth component;

[0069]

[0070] wherein,

[0071] Finally, the benefit ratio Q d of each component is calculated, and the maintenance importance is sorted.

[0072] Compared with the prior art, the present application has the following beneficial effects:

[0073] The present application considers the maintenance and failure dynamic characteristics of the diesel engine system when modeling the reliability of the diesel engine system, and the repairable dynamic fault tree adopted is designed based on the probability state transition model of the repairable system, which can consider the maintenance and failure dynamic characteristics of the Markov type repairable system, and has the advantages of short running time and simple analysis steps. In addition, the present application uses the Markov model to derive the quantitative calculation formula, and finally obtains the instantaneous availability change curve of the diesel engine system, so as to obtain the quantitative analysis of the reliability of the system, and the two kinds of qualitative analysis of the reliability of the minimum cut set of the fault tree and the maintenance importance of the component. According to the qualitative analysis results, the maintenance importance of the component is calculated by using the multi-criteria compromise solution sorting method, the weak link of the diesel engine electronic control system is judged through comprehensive analysis, so as to provide more accurate guidance for the design and maintenance of the new diesel engine system. BRIEF DESCRIPTION OF DRAWINGS

[0074] Figure 1 The present application is a flow chart of the diesel engine reliability evaluation method based on the repairable dynamic fault tree.

[0075] Figure 2 The present application is a flow chart of the diesel engine reliability evaluation method based on the repairable dynamic fault tree.

[0076] Figure 3 The cold standby gate of the repairable dynamic fault tree in the application is converted into a state transition graph of a Markov model.

[0077] Figure 4 The function gate of the repairable dynamic fault tree in the application is converted into a state transition graph of a Markov model.

[0078] Figure 5 The hot standby gate of the repairable dynamic fault tree in the application is converted into a state transition graph of a Markov model.

[0079] Figure 6 It is a schematic diagram of the diesel engine electronic control system of the embodiment.

[0080] Figure 7 It is a repairable dynamic fault tree modeling diagram of the diesel engine electronic control system of the embodiment.

[0081] Figure 8 It is a comparison diagram of a repairable dynamic fault tree and a Monte Carlo simulation of one million times.

[0082] Figure 9 It is a comparison diagram of a repairable dynamic fault tree and a Monte Carlo simulation of one million times.

[0083] Figure 10 It is a comparison diagram of repairable dynamic fault tree maintenance importance of the diesel engine electronic control system of the embodiment. DETAILED DESCRIPTION

[0084] In order to make the technical means, creative features, purposes and effects achieved by the application easy to understand, the application will be further described below in combination with specific embodiments.

[0085] In the description of the application, it should be noted that the directions or position relationships indicated by the terms "upper", "lower", "inner", "outer", "front end", "rear end", "two ends", "one end", "the other end" and the like are based on the directions or position relationships shown in the drawings, and are only for the convenience of describing the application and simplifying the description, and therefore cannot be understood as limiting the application. The application must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the application. In addition, the terms "first" and "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0086] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "provided with", "connection" and the like should be understood in a broad sense, for example, "connection" can be fixed connection, can also be detachable connection, or integrally connected; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0087] Referring to Figure 1 The present application provides a diesel engine reliability evaluation method based on a repairable dynamic fault tree, comprising the following specific steps S1-S7: the principle is as shown in Figure 2 The present application provides a diesel engine reliability evaluation method based on a repairable dynamic fault tree, comprising the following specific steps S1-S7: the principle is as shown in

[0088] S1, analyzing the principle and structure of the diesel engine system, determining the top event of the repairable dynamic fault tree; that is, confirming the failure logic characteristics of the diesel engine system, determining the failure criteria of the diesel engine system; Step S1 specifically includes:

[0089] S11, using the diesel engine electronic control system to monitor the real-time running state of the diesel engine;

[0090] The device for monitoring the running state of the diesel engine by the diesel engine electronic control system can monitor the change of the diesel engine running in real time during the running process of the diesel engine, timely feedback the conditions caused by the diesel engine and take corresponding measures for the conditions. The diesel engine electronic control system has one start signal, one control signal, one foot pedal signal, one dialogue device, one power supply, one standby power supply, one controller, one sensor system, one execution device and one fuel cut-off electromagnetic valve;

[0091] S12, regarding the diesel engine electronic control system as a series unit of the diesel engine, selecting the diesel engine electronic control system failure as the top event of the repairable dynamic fault tree.

[0092] In addition to assisting the diesel engine running, the diesel engine electronic control system also plays a role in monitoring the real-time state of the diesel engine and timely adjusting the power source of the diesel engine, so when modeling, the diesel engine electronic control system is regarded as a series unit and the "diesel engine electronic control system failure" is selected as the top event;

[0093] S2, based on the top event of the repairable dynamic fault tree, using the Markov repairable system to derive the quantitative calculation formula of the repairable dynamic fault tree;

[0094] The failure logic state transition diagram is obtained by combining the Markov repairable system and the fault tree analysis method; the quantitative calculation formula of the repairable dynamic fault tree is derived according to the failure logic state transition diagram; the quantitative calculation formula of the repairable dynamic fault tree is derived, specifically including:

[0095] S21, Derivation of OR logic gate quantitative calculation formula;

[0096] S x(i) (t) represents the OR gate input event x i The probability of normal operation at time t, F x(i) (t) is the OR gate input event x i The probability of failure state at time t, μ x(i) The repair rate of input event x i , λ x(i) The failure rate of input event x i , S y (t) represents the OR gate output event y at time t The probability of normal operation, F y (t) is the OR gate output event y at time t The probability of failure state, μ y The repair rate of output event y, λ y The failure rate of output event y. The OR gate quantitative calculation formula is as follows:

[0097]

[0098] S22, Derivation of AND logic gate quantitative calculation formula;

[0099] S x(i) (t) represents the AND gate input event x i The probability of normal operation at time t, F x(i) (t) is the AND gate input event x i The probability of failure state at time t, μ i The repair rate of input event x i , λ i The failure rate of input event x i , S y (t) represents the AND gate output event y at time t The probability of normal operation, F y (t) is the AND gate output event y at time t The probability of failure state, μ y The repair rate of output event y, λ y The failure rate of output event y. The AND logic gate quantitative calculation formula is as follows:

[0100]

[0101] S23, Derivation of cold standby logic gate quantitative calculation formula; as Figure 3 shown, wherein μ i Δt is the possibility of system state transition caused by repair rate μ i of input event x i in Δt time, λ iΔt is the input event x i In Δt time by the failure rate λ i The possibility of system state transition. Wherein, Figure 3 0 corresponds to the table rule 1, 1 corresponds to the table rule 2, 2 corresponds to the table rule 3.

[0102] Cold standby gate quantitative operation rule list

[0103]

[0104] S x(i) (t) represents the cold standby gate input event x i The probability of normal operation at time t, F x(i) (t) is the cold standby gate input event x i The probability of failure state at time t, S y (t) represents the cold standby gate output event y The probability of normal operation at time t, F y (t) is the cold standby gate output event y The probability of failure state at time t, μ y The repair rate of output event y, λ y The failure rate of output event y. From the cold standby gate failure logic, the cold standby gate state transition matrix of the repairable dynamic fault tree is:

[0105]

[0106] In the formula, μ1, μ2 represent the repair rate of input events x1, x2, λ1, λ2 represent the failure rate of input events x1, x2;

[0107] From the state transition matrix A, the state probability of the cold standby logic gate of the repairable dynamic fault tree can be calculated by the following formula:

[0108]

[0109] P0(t), P1(t), P2(t) respectively represent the three solutions of the equation group; P'0(t), P'1(t), P'2(t) are the derivatives of P0(t), P1(t), P2(t) respectively.

[0110] Solving the above equation group, the quantitative calculation formula of the cold standby logic gate is obtained:

[0111]

[0112] Where e is the exponential function, n is the number of components; Δ(s) = s 2 +2(λ+μ)s+(λ 2 +λμ+μ 2), s1, s2 are two roots of Δ(s) = 0, μ represents repair rate, λ represents failure rate, and

[0113]

[0114] S24, a quantitative calculation formula of the feedback logic gate is derived; as shown in the following table, wherein μ Figure 4 i Δt is the probability of the system state transition caused by the repair rate μ i of the input event x i in Δt time. i Δt is the probability of the system state transition caused by the failure rate λ i of the input event x i in Δt time. Figure 4 As shown in the following table, 0 corresponds to rule 1 of the following table, 1 corresponds to rule 2 of the following table, 2 corresponds to rule 3 of the following table, and so on.

[0115] A list of quantitative operation rules of the feedback logic gate

[0116]

[0117] A failure of a component in a diesel engine system (trigger event x3) occurs. When event x3 occurs, components x1 and x2 simultaneously fail. It is generally used to describe the relationship between the feedback link and the failure of the components on the path. x(i) (t) represents the normal working probability of the functional gate input event x i at t time, F x(i) (t) is the failure state probability of the functional gate input event x i at t time, S y (t) represents the normal working probability of the functional gate output event y at t time, F y (t) is the failure state probability of the functional gate output event y at t time, λ1, λ2 and λ3 are the failure rates of components x1, x2 and x3 respectively. μ1, μ2 and μ3 are the equivalent repair rates of components x1, x2 and x3 respectively. According to the failure logic of the functional gate, the state transition matrix of the repairable dynamic fault tree functional gate is;

[0118]

[0119] In the formula, μ1, μ2, μ3 represent the repair rates of input events x1, x2, x3, and λ1, λ2, λ3 represent the failure rates of input events x1, x2, x3.

[0120] According to the state transition matrix A of the functional gate failure logic, the state probability of the repairable dynamic fault tree functional logic gate can be calculated by the following formula:

[0121] ​

[0122] P0(t), P1(t), P2(t), P3(t), and P4(t) represent the five solutions to the system of equations; P'0(t), P'1(t), P'2(t), P'3(t), and P'4(t) are the derivatives of P0(t), P1(t), P2(t), P4(t), and P5(t), respectively.

[0123] Solving the above system of equations yields the quantitative calculation formula for cold standby logic gates:

[0124]

[0125] S25, Derive the quantitative calculation formula for hot standby logic gates; such as Figure 5 As shown, where μ i Δt is the input event x i Within time Δt, the maintenance rate μ i The probability of causing a system state transition, λ i Δt is the input event x i Within time Δt, the failure rate λ i The possibility of causing a system state transition. For example... Figure 5 As shown in the table below, 0 corresponds to rule 1, 1 corresponds to rule 2, 2 corresponds to rule 3, and so on.

[0126] Hot standby door status combination table

[0127]

[0128] S x(i) (t) represents the hot standby gate input event x. i The probability of normal operation at time t, F x(i) (t) represents the hot standby gate input event x. i The probability of failure at time t, μ i For input event x i The maintenance rate, λ i For input event x i Failure rate. S y F(t) represents the probability of the hot standby gate output event y working normally at time t. y (t) represents the failure state probability of the hot standby gate output event y at time t, μ y To output the repair rate of event y, λ y The failure rate of output event y is given. Based on the hot standby gate failure logic, the state transition matrix of the repairable dynamic fault tree hot standby gate is:

[0129]

[0130] The standby door quantitative calculation formula is as follows:

[0131]

[0132] S3, determining the failure rate and maintenance rate of each component in the diesel engine system: determining the maintenance and failure logic relationship between components, using a direct algorithm and utilizing the derived quantitative calculation formula of the repairable dynamic fault tree, obtaining the transient availability of the top event of the repairable dynamic fault tree;

[0133] That is, a repairable component state transition matrix is established, the availability of the repairable component at time t is obtained by state transition, and the transient availability of the top event of the repairable dynamic fault tree (i.e., the success probability of the diesel engine electronic control system) is obtained by a direct algorithm; step S3 specifically includes:

[0134] S31, determining the maintenance rate of each component in the diesel engine system: establishing a repairable component state transition matrix, and obtaining the availability of the repairable component at time t by state transition;

[0135] Assuming that there are only two states of components in a complex repairable system: normal available state and failure state, respectively λ A and μ B , the available state and failure state of the repairable component are 0 and 1, respectively.

[0136] The state transition matrix of the repairable component is:

[0137]

[0138] According to the Markov theorem of the repairable system, the state matrix of the repairable component can be converted to:

[0139]

[0140] Where P0'(t), P1'(t) are the derivatives of P0(t), P1(t). P0(t), P1(t) represent two solutions of the equation set, respectively.

[0141] Taking L transform on both ends of the above formula, the equation set is obtained:

[0142]

[0143] According to (P0(0), P1(0))=(1, 0), the solution is obtained as:

[0144]

[0145] According to the initial condition, the availability of the repairable component at time t is:

[0146]

[0147] S32, determining the failure rate of each component in the diesel engine system: using a direct algorithm and utilizing the derived quantitative calculation formula of the repairable dynamic fault tree, the transient availability of the top event of the repairable dynamic fault tree is obtained.

[0148] Assuming that the normal working probability of the unit is A(t), the shutdown state probability is P(t) = A1(t)·A2(t)·...·An(t). Then there are n bottom event units under the top event, and the failure logic of the bottom event unit is OR. The shutdown state probability of the top event at time t is n P(t) = A1(t)·A2(t)·...·An(t). Then there are n bottom event units under the top event, and the failure logic of the bottom event unit is AND. The shutdown state probability of the top event at time t is

[0149] S4, using time operator to describe the failure timing logic, the failure behavior of the repairable dynamic fault tree logic gate is represented, the repairable dynamic fault tree top event is processed by using the time operator structure function, and the minimal cut set of the repairable fault tree is obtained; this step S4 specifically includes:

[0150] S41, repairable dynamic fault tree time operator rule; the time operator rule is used to describe the failure behavior of the repairable dynamic fault tree, and the specific basic rules are as follows:

[0151] Rule 1: represents OR logic, and represents AND logic;

[0152] Rule 2: X1 < X2 represents that components X1 and X2 fail at the same time;

[0153] Rule 3: represents that component X1 fails before component X2, and the dynamic failure logic is included in this rule;

[0154] Rule 4: represents that component X1 fails before component X2, and the dynamic failure logic is not included in this rule.

[0155] S42, the failure behavior of the repairable dynamic fault tree logic gate is represented, including:

[0156] Assuming that there are repairable components X1 and X2, the OR gate time operator expression is:

[0157] The AND gate time operator expression is: AND = X1⊙X2;

[0158] Assuming that there are repairable components X1 and X2, and X1 fails before X2, then the priority AND gate time operator expression is:

[0159] Assuming there are repairable components X1 and X2, X2 is the standby component of X1, X2 is not activated before X1 fails, then the cold standby gate time operator expression is:

[0160] Assuming there are repairable components X1 and X2, X2 is the standby component of X1, X2 is activated before X1 fails, then the hot standby gate time operator expression is T HSP = X1 o X2;

[0161] Assuming there are repairable components X, X1 and X2, and the failure of X will cause the failure of X1 and X2, then the function gate time operator expression is:

[0162] S43, using the time operator structure function to normalize the top event of dynamic fault tree, and obtaining the minimal cut set of repairable fault tree;

[0163] The standard form of repairable dynamic fault tree structure function is:

[0164] In the formula, CSS r is the cut set;

[0165] Then the minimum cut set calculation formula is:

[0166]

[0167] Assuming that the initial r = 1, then the minimum cut set calculation formula is iterated q times, until TE_min q Does not satisfy r represents the component index value; h represents the iteration number of the minimum cut set calculation formula.

[0168] S5, calculate the repairable dynamic fault tree structure importance;

[0169] Assuming that the state of the bth component X changes from 0 to 1, the state change of the diesel engine system is Q b (X);

[0170] Then the structure importance of the component is:

[0171] In the formula, a represents the number of cut sets.

[0172] S6, based on the minimum cut set and repairable dynamic fault tree structure importance of the repairable fault tree, use multi-criteria compromise solution ranking method to calculate the component maintenance importance;

[0173] According to the actual situation of the system unit, select the unit component importance v 1f , maintenance rate v2f v 3f , frequency of occurrence 4f as an evaluation index of repair importance; wherein v 3f and v 4f index score is the weight of the expert score obtained according to the experience of the expert. The structural importance of each component obtained in step S5 is substituted into the unit component importance.

[0174] A decision matrix D is established.

[0175]

[0176] In the above formula, v 11 , v 12 ,...v df are evaluation indexes, respectively corresponding to the fth evaluation index of the component with serial number d.

[0177] The decision matrix D is normalized by the following formula.

[0178]

[0179] In the above formula, p is the number of components participating in the evaluation, and g is the number of participating evaluations.

[0180] The normalized decision matrix r df is obtained.

[0181] The positive ideal solution r + and the negative ideal solution r - of each evaluation index are calculated.

[0182]

[0183] In the above formula, F is the minimum value of the evaluation index serial number, and F' is the maximum value of the evaluation index serial number.

[0184] S d is the absolute value of the positive and negative ideal solutions, and the distance ratio R d of the positive and negative ideal solutions of each component is calculated by the following formula:

[0185]

[0186] In the above formula, l is the number of evaluation indexes, and w df is the weight of the centrality criterion of the evaluation index with serial number f in the dth component.

[0187] The benefit ratio v d is calculated by the following formula: v d is the decision mechanism coefficient of the "majority criterion" strategy of the dth component.

[0188]

[0189] Finally, according to the benefit ratio Q of each component d The maintenance importance ranking is performed.

[0190] S7, based on the transient availability of the repairable dynamic fault tree top event and the component maintenance importance, analyzing and evaluating the diesel engine system, so as to find out the weak component unit of the diesel engine system, and help the growth of the reliability of the diesel engine system in the whole life cycle.

[0191] The application provides a diesel engine reliability evaluation method based on a repairable dynamic fault tree. First, the system input, output boundary, reliability parameter and system failure criterion are confirmed according to the structure of the diesel engine electronic control system, and the calculation formula of the repairable dynamic fault tree logic gate is established by using the Markov repairable system theory. In order to determine the weak link of the diesel engine system, the time operator minimal cut set algorithm is used to obtain the minimal cut set of the fault component of the diesel engine system. In order to better judge the maintenance importance of the diesel engine system, the multi-criteria compromise solution ranking method is used to select the unit component importance v 1f , the maintenance rate v 2f , the maintenance cost v 3f and the occurrence frequency v 4f as the evaluation indexes of the maintenance importance. In addition, the comparison of the Monte Carlo simulation results shows that the repairable dynamic fault tree method designed improves the reliability analysis efficiency of the diesel engine electronic control system.

[0192] In the embodiment, MATLAB 2019b can be used as a simulation calculation software, the reliability evaluation of the diesel engine electronic control system considering the dynamic maintenance and fault characteristics at the same time is simulated, the repairable dynamic fault tree of the application is compared with Monte Carlo simulation of 10,000 times and Monte Carlo simulation of 1,000,000 times respectively, and the availability quantitative analysis value of the diesel engine electronic control system based on the repairable dynamic fault tree modeling is output.

[0193] In the embodiment, it is assumed that the working state of the diesel engine electronic control system and the components is two states of fault and normal, and the component failure rate and the repair rate obey the exponential distribution. As shown in the figure, Figure 6 the principle diagram of the diesel engine electronic control system is shown, then the component start signal x1, the control signal x2, the foot pedal signal x3, the dialogue device x4, the power supply x5, the standby power supply x6, the controller x7, the sensor system x8, the execution device x9, the fuel cut-off electromagnetic valve x 10 , the failure rates (10 -3 / h -1 ) are 0.082, 0.07, 0.05, 0.064, 0.04, 0.04, 0.05, 0.01, 0.022 and 0.07 respectively, and the repair rates ( / h -11.3, 1.5, 0.8, 0.5, 0.6, 0.6, 1.5, 0.85, 0.96 and 0.8, respectively. The established repairable dynamic fault tree is shown in Figure 7

[0194] In the Monte Carlo simulation method for quantitative reliability analysis of diesel engine electronic control system, according to the failure rate λ and repair rate μ of the system unit, the availability formula of each unit in the system is obtained and input into the simulation, a 0-1 uniform distribution random number array is generated, and whether each unit is in failure is judged according to the unit availability and the random number array. According to the minimum cut set and the minimum path set of the system and the failure condition of the system unit, whether the system is in failure is determined, the simulation is performed for M times, the number of times m that the system is in success state is recorded, and when the simulation times M are large enough, the system reliability availability is closer to the actual value.

[0195]

[0196] In the above formula, t is a time variable, and the unit is h.

[0197] In the calculation of the repair importance of the repairable dynamic fault tree, the evaluation index value is determined according to the expert scoring, and the weight of the score is allocated according to the expert experience. This time, three experts who have been working in this field for 15 years, 10 years and 5 years are invited, and the scoring weights of the three experts are 0.4, 0.3 and 0.3 respectively. The evaluation index value of the minimum cut set of the electronic control system is converted into a decision matrix as follows:

[0198]

[0199] This decision matrix only gives the evaluation index value of the minimum cut set X1, X2, X3 and X4.

[0200] Figure 8 The repairable dynamic fault tree and the Monte Carlo simulation of 10,000 times in 30h of the electronic control system availability change curve are given, the black hollow circle point line is the repairable dynamic fault tree in 30h of the electronic control system availability change trend, the triangle point line is the 10,000 times Monte Carlo simulation in 30h of the electronic control system availability change trend. The 10,000 times Monte Carlo simulation calculation time is 15.34S, and it can be seen from Figure 8 that the random fluctuation of 10,000 times Monte Carlo simulation is very large.

[0201] Figure 9 ​The availability change curve of the electric control system in 30 hours is given by the repairable dynamic fault tree and Monte Carlo simulation of one million times, the black hollow dot line is the availability change trend of the electric control system in 30 hours by the repairable dynamic fault tree, and the triangular point line is the availability change trend of the electric control system in 30 hours by Monte Carlo simulation of one million times. Figure 9 It can be seen from the above simulation results that the random fluctuation of Monte Carlo simulation of one million times gradually tends to be stable, and is close to the calculated value of the repairable dynamic fault tree.

[0202] Figure 10 The maintenance importance of the minimal cut sets of the diesel engine electric control system is given. Figure 10 It can be seen from the above simulation results that the random fluctuation of Monte Carlo simulation of one million times gradually tends to be stable, and is close to the calculated value of the repairable dynamic fault tree. 10 The components X8, X9 and X

[0203] From the above simulation results, it can be seen that the diesel engine electric control system reliability evaluation method based on the repairable dynamic fault tree can quickly and accurately evaluate the system reliability, and the precision and calculation speed are obviously better than Monte Carlo simulation.

[0204] In summary, the diesel engine electric control system reliability evaluation method based on the repairable dynamic fault tree has high precision and strong universality, and can accurately evaluate the reliability of the diesel engine electric control system.

[0205] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Therefore, if these modifications and variations of the present application belong to the scope of the claims of the present application and their equivalent technologies, the present application also intends to include these modifications and variations.

Claims

1. A diesel engine reliability assessment method based on a repairable dynamic fault tree, characterized in that, Includes the following steps: S1. Analyze the principle and structure of the diesel engine system to identify the repairable top event of the dynamic fault tree; S2. Based on the top event of the repairable dynamic fault tree, derive the quantitative calculation formula of the repairable dynamic fault tree using the Markov repairable system. S3. Determine the failure rate and repair rate of each component in the diesel engine system: Determine the repair and failure logic relationship between components, use a direct algorithm and the derived quantitative calculation formula of the repairable dynamic fault tree to obtain the transient availability of the top event of the repairable dynamic fault tree; S4. Use time operators to describe the fault timing logic, describe the failure behavior of the logic gates of the repairable dynamic fault tree, use time operator structure functions to process the top event of the repairable dynamic fault tree, and obtain the minimum cut set of the repairable fault tree. S5. Calculate the importance of the repairable dynamic fault tree structure; S6. Based on the minimum cut set of the repairable fault tree and the structural importance of the repairable dynamic fault tree, the component maintenance importance is calculated using the multi-criteria compromise solution ranking method. S7. Based on the transient availability and component maintenance importance of the repairable dynamic fault tree top event, analyze and evaluate the diesel engine system; Step S2 includes: obtaining a failure logic state transition diagram by combining Markov repairable systems and fault tree analysis methods; and deriving a quantitative calculation formula for a repairable dynamic fault tree based on the failure logic state transition diagram. The derived quantitative calculation formula for the repairable dynamic fault tree specifically includes: S21. Derive the quantitative calculation formula for OR logic gates; S22. Derive the quantitative calculation formula for AND logic gates; S23. Derive the quantitative calculation formula for cold standby logic gates; S24. Derive the quantitative calculation formula for functional logic gates; S25. Derive the quantitative calculation formula for hot standby logic gates; Step S3 includes: S31. Determine the repairability of each component in the diesel engine system: Establish the state transition matrix of the repairable component, and obtain the availability of the repairable component at time t from the state transition; S32. Determine the failure rate of each component in the diesel engine system: using a direct algorithm and the derived quantitative calculation formula for the repairable dynamic fault tree, obtain the transient availability of the top event of the repairable dynamic fault tree; In step S4, the fault timing logic is described using time operators, including: using time operator rules to describe the failure behavior of the repairable dynamic fault tree, the specific basic rules are as follows: Rule 1: Representation or logic, Representation and Logic; Rule 2: Representation Component and components Simultaneous failure; Rule 3: Representation Component Prior to components A failure has occurred, and this rule contains dynamic failure logic; Rule 4: Representation Component Prior to components A failure occurs, and this rule does not contain dynamic failure logic; In step S4, the failure behavior of the repairable dynamic fault tree logic gate is described, including: Assuming there are repairable components and The OR gate timing operator expression is: ; The expression for the AND gate time operator is: ; Assuming there are repairable components and ,and Prior to If a failure occurs, the priority AND gate timing operator expression becomes: ; Assuming there are repairable components and , for spare components exist If the system was not activated before the fault, the cold standby door time operator expression is: ; Assuming there are repairable components and , for spare components exist If the system was activated before the fault, the hot standby door time operator expression is: ; Assuming there are repairable components , and ,and Failure will lead to and If it fails, the function gate time operator expression is: .

2. The diesel engine reliability assessment method based on a repairable dynamic fault tree according to claim 1, characterized in that, Step S1 includes: S11. A diesel engine electronic control system is used to monitor the real-time operating status of the diesel engine oil; S12. The diesel engine electronic control system is regarded as a unit connected in series with the diesel engine, and the fault of the diesel engine electronic control system is selected as the top event of the repairable dynamic fault tree.

3. The diesel engine reliability assessment method based on a repairable dynamic fault tree according to claim 1, characterized in that, In step S4: The time operator structure function is: In the formula, It is a cut set; The formula for calculating the minimum cut set is: ； In the above formula, For the minimum cut set, assume that initially... The minimum cut set calculation formula is iterated q times until... Not satisfied ; r represents the component index value; h represents the number of iterations in the minimum cut set calculation formula.

4. The diesel engine reliability assessment method based on a repairable dynamic fault tree according to claim 3, characterized in that, In step S5, the importance of the repairable dynamic fault tree structure is calculated, including: Assume the first Components The state changes from 0 to 1, corresponding to the state change of the diesel engine system. ； The structural importance of the component is: ; In the formula, a represents the number of cut order sets.

5. The diesel engine reliability assessment method based on a repairable dynamic fault tree according to claim 4, characterized in that, In step S6, the component maintenance importance is calculated using a multi-criteria compromise solution ranking method, including: setting... The evaluation index is d, where d is the component ordinal number and f is the evaluation index ordinal number. The importance of the unit components needs to be selected based on the actual situation of the diesel engine system. Repair rate Repair costs Frequency of occurrence As an evaluation indicator of the importance of maintenance; among which and The indicator scores are obtained from expert ratings; Substitute the structural importance of each component obtained in step S5 into the unit component importance; Establish a decision matrix : ； In the above formula, The evaluation indicators are respectively numbered as follows: The first component One evaluation indicator; In the above formula Standardize by substituting into the following formula: p represents the number of components participating in the evaluation, and g represents the number of components participating in the evaluation. Obtain the standardized decision matrix ; Calculate the positive ideal solution for each evaluation index. and negative ideal solution : ； F is the minimum ordinal value of the evaluation index. The maximum ordinal value of the evaluation index; Given the absolute values ​​of the positive and negative ideal solutions, the distance ratio between the positive and negative ideal solutions of each component is calculated using the following formula. : ； The number of evaluation indicators, Let f be the weight of the centrality criterion for the evaluation index with ordinal number f in the d-th component; Calculate the benefit ratio: For the decision mechanism coefficients of the majority criterion strategies of the d-th component; ； in, , , , ; Finally, based on the profit ratio of each component Rank the maintenance importance.

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