JP7154922B2 - Failure factor priority display device - Google Patents

Description

The present invention relates to a fault factor priority presentation device in a fault tree.

Fault tree analysis (FTA) is known as a technique for preventing product defects. FTA is an analysis technique that systematically searches for the source of the defect by picking up the defect phenomenon of the product and sequentially identifying and developing the cause of the defect in a hierarchical manner. The result of this analysis has a tree structure in which the defect event of the product is at the top and the cause of the failure is in the lower hierarchy. This tree-structured analysis result is called a “fault tree”. A failure event of a product to be analyzed is called a "top event" because it is positioned at the top of the fault tree. A fault tree consists of multiple layers. A fault factor at the end of the fault tree is called a "terminal event" because it is positioned at the end of the fault tree. The terminal event represents the root cause of the apex event.

For example, when analyzing the failure factors of a certain system, the failure event of the system is described as the top event, and then the failure of the subsystem that is the cause of the failure of the system is identified and described in the hierarchy below the top event. Next, component failures, which are the causes of subsystem failures, are identified and described in the lower hierarchy of the subsystem failure factors. In this way, the root cause, ie, the failure factors down to the terminal event, are clarified.

FTA can be used to incorporate product reliability in the design stage and to investigate the cause of a product defect. When used at the design stage, set failure events that you do not want to occur in the product in the top event, and take measures to prevent the occurrence of the end event that is the root cause obtained as the analysis result. to improve In the failure factor analysis after the occurrence of failure, the failure event that occurred is set as the top event, FTA is performed, and it is confirmed whether the terminal event is actually the failure factor of the top event.

At this time, if there are many terminal events that have been identified, it is more efficient to prioritize them and consider the ones with the highest priority first.

For example, Patent Document 1 has been proposed as a technique for searching for the cause of failure. In the technique described in Patent Document 1, the priority is calculated based on the number of occurrences of the cause of failure and the freshness calculated by the number of days elapsed since the date of the latest occurrence.

JP 2009-217457 A

In Patent Document 1, failure factors, that is, the number of occurrences of terminal events are accumulated, and priority is determined based on this. This is based on the idea that the greater the number of occurrences of terminal events, the higher the probability that they are the cause of apex events.

However, since a failure is caused by a chain of multiple events, for example, "initial crack" → "crack growth" → "failure", not only the failure rate of the end event but also the path between the top event and the end event It is necessary to consider the probability of In other words, in the above example, the inter-event probability is given by (probability that the cause of the top event “failure” is “crack growth”) × (probability that the cause of “crack growth” is “initial crack”) multiplication is required. The technique described in Patent Document 1 has a problem that only the terminal event is considered, and the probability of the path between the top event and the terminal event is not considered.

In addition, the probabilities of all combinations between events such as (probability that the cause of the top event “failure” is “crack growth”) and (probability that the cause of “crack growth” is “initial crack”) are prepared in advance. It takes time to keep it. Furthermore, this probability changes depending on the surrounding environment and usage of the target product/part. Even if the same product or part is used, the probability will differ depending on whether it is used in the nuclear field or as a home appliance. In other words, the probability changes depending on the field such as nuclear power and home appliances.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a failure factor priority presentation apparatus capable of evaluating and presenting the priority of failure factors contained in a failure tree, thereby speeding up identification of the failure factors.

In order to achieve the above object, the present invention is characterized by a causal relationship database storing causal relationships representing a chain of a plurality of elements including parts and phenomena regarding the occurrence of defects in products, and an output device for displaying a failure tree related to the occurrence of defects in a product, branching out toward them; and an inter-event causal probability calculator for calculating the probability of a path from the top event to the terminal event from the causal relationship stored in the causal relationship database. and an intermediate event before the terminal event and after the top event, wherein the inter-event causal probability calculation unit calculates the probability of a path between the top event and the intermediate event in the middle of the fault tree. The event is displayed in the event, and the probability of the path between the intermediate event and the terminal event and the probability calculated by multiplication by the inter-event causal probability calculation unit are displayed together and distinguished in the terminal event of the fault tree . That's what it is.

According to the present invention, since the priority of the failure factors included in the failure tree is evaluated and presented, it is possible to provide a failure factor priority presentation device capable of speeding up identification of failure factors.

1 is a diagram illustrating the configuration of a fault factor priority presentation device in a fault tree according to a first embodiment of the present invention; FIG. It is a figure explaining the causal relationship concerning 1st Example of this invention. It is a figure which shows the concrete causal relationship based on 1st Example of this invention. FIG. 4 is a diagram showing an example of a field input screen according to the first embodiment of the present invention; FIG. 4 is a diagram showing an example of a fault tree input screen according to the first embodiment of the present invention; FIG. FIG. 4 is a diagram showing an example of a fault tree to be input according to the first embodiment of the present invention; FIG. 10 is a diagram showing an output example of the inter-event causal probability and the probability of the path from the top event to the terminal event according to the first embodiment of the present invention; FIG. 10 is a diagram showing an example of inputting the probability of a path between a top event and a terminal event according to the first embodiment of the present invention; FIG. 7B is a diagram showing an example of displaying only factors equal to or greater than the threshold input in FIG. 7A; It is a figure which shows the example which displayed the causal relationship based on 2nd Example of this invention by the number of cases.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Equipment configuration)

FIG. 1 is a diagram for explaining the configuration of a fault factor priority presentation device in a fault tree according to an embodiment of the present invention.

The failure factor priority presentation device in the fault tree has a failure factor priority presentation device 101 and a terminal device 102 in the fault tree. These are connectable via a network 103 . The fault factor priority presentation device 101 in the fault tree is a general computer and has a central control device 104 (control device), an input device 105, an output device 106, a main storage device 107 and an auxiliary storage device . These are interconnected by a bus. The auxiliary storage device 108 stores a causality database 112 (DB) (details will be described later).

The auxiliary storage device 108 is an external storage device independent of the failure factor priority presentation device 101 in the fault tree, and a configuration in which both are connected via the network 103 is also possible.

The field input unit 109, the fault tree input unit 110, and the inter-event causal probability calculation unit 111 in the main storage device 107 are programs. Hereinafter, if the subject is described as "○○ part", the central control unit 104 reads each program from the auxiliary storage device 108, loads it into the main storage device 107, and then performs the function of each program (details will be described later). shall be realized. The field input unit 109 receives input by the user of the field of the product/part to be evaluated for the fault tree. The fault tree input unit 110 receives input of a fault tree by the user. The inter-event causal probability calculation unit 111 calculates an event based on the field input by the field input unit 109 , the fault tree input by the fault tree input unit 110 , and the causal relationships accumulated in the causal relationship database 112 . Priorities are presented by finding the probability between and calculating the probability of the path from the top event to the terminal event. A calculation method will be described separately.

The terminal device 102 is also a typical computer and has a central controller, input device, output device, main memory and auxiliary memory (not shown). These are interconnected by a bus.

The main storage device and auxiliary storage device in the terminal device 102 may not have the programs of the main storage device 107 and auxiliary storage device 108 in the failure factor priority presentation device 101 . In that case, the terminal device 102 may directly access the programs in the main storage device 107 and the auxiliary storage device 108 to identify the cause of the failure.
(Causal relationship)
A plurality of causal relationships are stored in the causal relationship database 112 . A causal relationship represents a chain of causal effects leading up to the occurrence of a product defect. This causal relationship is created using information extracted from individual failure cases that occurred in the past. Also, the information is updated every time a problem occurs. In the first embodiment, the cause-and-effect relationship is represented by a chain of a plurality of elements including parts and phenomena regarding the occurrence of product defects.

FIG. 2A is a diagram showing causality according to the first embodiment of the present invention. A causal relationship 200 is composed of three or more (plurality) elements 201a, 201b, 201c, . . . Elements 201a, 201b, and 201c that constitute the causal relationship 200 are composed of a part A 202, phenomenon A 203, part B 205, phenomenon B 206, part C 208, and phenomenon C 209, respectively. Each element is connected by directed segments 204, 207, . . . Among a set (two) elements connected by one directed line segment, the element on the starting point side of the directed line segment is the cause, and the element on the end point side is the effect. For example, element 201b is the cause from the perspective of element 201a. Similarly, element 201b is the effect from the point of view of element 201c, and element 201c is the cause from the point of view of element 201b. In FIG. 2A, the causal order is represented in a daisy chain, where the right element causes the left element. Note that the starting point side (cause side) of a directed segment is called "upstream", and the end point side (result side) is sometimes called "downstream".

In the example of FIG. 2A, the occurrence of phenomenon C209 in component C208 causes phenomenon B206 to occur in component B205. Furthermore, this represents that the phenomenon A203 occurs in the part A202. Here, the component A 202, component B 205, and component C 208 may be not only component names, but also product names, system names, and subsystem names.

The causal relationship database 112 stores a plurality of causal relationships 200, each of which has a causal relationship ID 200a that uniquely identifies itself. Furthermore, the product name, title, representative part, etc. may be displayed together with the causal relationship ID 200a. For example, piping as a component may be used in the field of nuclear power or home appliances such as heat pump water heaters. It is then easy to identify.

FIG. 2B is a diagram showing specific causal relationships according to the first embodiment of the present invention. FIG. 2B shows an example of a causal relationship related to "XX product cannot be started". The causality 200 generally indicates the following.
- A short circuit 215 occurs in the power supply circuit 214 due to the generation of whiskers 217 in the electronic component 216 .
• An output failure 213 occurs in the power supply 212 due to a short circuit 215 in the power supply circuit 214 .
- Due to the occurrence of an output failure 213 in the power supply 212, a failure to start 211 occurs in the ○○ product 210.

It is assumed that the causal relationship database 112 stores a large amount of data on causal relationships of past failures in such a form.
(User procedure)
A field input screen 301 as shown in FIG. 3 is displayed on the output device 106 by the field input unit 109 . The field input screen 301 is composed of a field field 302 and a keyword field 303 . The field column 302 consists of a check box 304 and a field name column 305 . Keywords corresponding to the field column 302 are displayed in the keyword column 303 . For example, in the field of nuclear energy, "Nuclear power or nuclear reactor or ..." is displayed, and in the field of consumer electronics, "Home appliance or washing machine or refrigerator" is displayed. Similarly, for the automobile field, "automobile..." is displayed, and for the personal computer (PC) field, "PC..." is displayed. This keyword is a field-specific keyword.

The user selects the check box 304 of the product/part field to be evaluated. After that, by pressing the "OK" button 306, the selected field is confirmed as an evaluation target.

Subsequently, the fault tree input screen as shown in FIG. 4 is displayed on the output device 106 by the fault tree input unit 110 . FIG. 4 is a diagram showing an example of a fault tree input screen according to the first embodiment of the present invention. The user inputs the address of the file in which the fault tree to be evaluated, which is saved on the terminal device 102 , is defined in the fault tree address input field 402 . Here, it is assumed that a fault tree as shown in FIG. 5 is defined in the file defining the fault tree to be evaluated. The fault tree may be created automatically by storing a creation program in the main storage device 107 . The fault tree branches from the top event to the terminal event to display causal relationships for product failure. FIG. 5 is a diagram showing an example of a fault tree to be input according to the first embodiment of the present invention. The output device 106 displays a fault tree indicating the cause-and-effect relationship of failures related to the field input by the field input unit 109 . In this failure tree, there are two factors of "pipe breakage" 501 in the nuclear power field, "pipe crack growth" 502 and "pipe corrosion" 505, and furthermore, "pipe crack growth" 502 has " It shows that there are "piping initial crack" 503 and "piping impact" 504, and that "piping corrosion" 505 is caused by "piping seawater inflow" 506 and "piping wet condition" 507.

In evaluating the fault tree, in addition to directly entering an address in the fault tree address input field 402, when the user presses a reference button 403, a file saved on the terminal device 102 can be displayed and a selectable file can be selected. A screen may be displayed and the address of the file selected there may be entered in the fault tree address input field 402 . By pressing the "OK" button 404, the input fault tree is determined as an evaluation target.

As described above, when the field and the fault tree are input by the user, the inter-event causal probability calculation unit 111 calculates the probability of the path from the top event to the terminal event, and the display content 601 is as shown in FIG. displayed on the output device 106 in this format. FIG. 6 is a diagram showing an output example of the inter-event causal probability and the probability of the path from the top event to the terminal event according to the first embodiment of the present invention. The inter-event causal probability calculation method will be described separately.

In FIG. 6, the probabilities between events are displayed under each factor. For example, in FIG. 6 , the probability that the cause of “damage in pipe” 602 is “crack growth in pipe” 603 is displayed as 0.3, and the cause of “crack growth in pipe” 603 is “initial crack in pipe” 604 is displayed as 0.2. The probability between events ranges from 0 to 1, with higher values indicating a higher probability of occurrence.

The probability of the path between the top event and the terminal event is displayed in [ ]. The probability of this path is displayed in the terminal event "Piping Initial Crack" 604 . For example, it indicates that the probability from "piping failure" 602 to "piping initial crack" 604 is 0.2×0.3=0.06. In FIG. 6, the probability of the path between "pipe breakage" 602 and "pipe wetness" 608 is 0.63, which is higher than other factors.

In the first embodiment, the probability of the terminal event "pipe initial crack" 604 is multiplied by the probability of the intermediate event "pipe crack growth" 603 before this terminal event and after the top event. Values are expressed as probabilities of paths from apex events to terminal events. Further, in the first embodiment, the path probability 0.3 between the top event "pipe breakage" 602 and the intermediate event "pipe crack growth" 603 is set to 603, the probability 0.2 of the path between the intermediate event "pipe crack propagation" 603 and the terminal event "pipe initial crack" 604 is set to the terminal event "pipe initial crack 604. That is, the probability of the path between the top event and the intermediate event is displayed within the intermediate event. Other events are similar.

For the terminal event in the first embodiment, the probability of the path between the intermediate event and the terminal event and the probability of the path between the top event and the terminal event (the probability calculated by multiplying by the inter-event causal probability calculation unit 111) are written together. The probability of the path between the top event and the terminal event is displayed in [ ] to distinguish it from the probability of the path between the intermediate event and the terminal event.

By presenting the probabilities of the paths between the top event and the terminal event in this way, the user can efficiently consider the factors with the highest probabilities.
(Inter-event causal probability calculation method)
A method of calculating the inter-event causal probability will be described using the probability that the cause of the “top event” is “factor A” as an example. The probability that the cause of the "top event" is "Factor A" is obtained by the following flow.
(1) Search the causal relationship database 112 with the keyword of the field specified by the user on the field input screen 301, and acquire the causal relationship that matches the keyword conditions. For example, if the field of nuclear power is specified on the field input screen 301, the causal relation database is searched with the keyword "nuclear power or nuclear reactor or ..." to acquire the causal relation that matches the conditions.
(2) Among the causal relationships acquired in (1), acquire causal relationships including "top event" and count the number of such causal relationships. A causal relationship in which the “top event” is the terminal event is also possible, but here we want to find the ratio of “factor A” among the factors of the “top event”, so the factor of the “top event” is included. In other words, causal relationships in which the “top event” is the terminal event are not acquired as the number of cases.
(3) Among the causal relationships acquired in (2), acquire causal relationships in which the cause of the top event is "Factor A", and count the number of such causal relationships.
(4) Divide the number of cases obtained in (3) by the number of cases obtained in (2).

For example, assume that 100 causal relationships in the nuclear power field have been acquired by (1). In (2), it is assumed that the causal relationships obtained in (1) include 20 causal relationships including "top event". Next, in (3), it is assumed that two "top events" whose cause is "factor A" are included. In this case, the probability that the cause of the "top event" is "Factor A" is 2/20, which is 0.1.

By performing the processes (1) to (4) above, obtaining the inter-event causal probability, and multiplying from the top event to the terminal event, the probability of the path between the top event and the terminal event is calculated in consideration of the field. .

When searching for a causal relationship, synonyms and synonym dictionaries may be used to absorb fluctuations in expressions such as "damage" and "destruction" so that they are treated as the same word.

According to the first embodiment, the probability of the path between the top event and the terminal event is calculated, and based on this, the priority of the failure factors included in the failure tree is evaluated and presented. identification can be expedited.

Furthermore, a threshold may be used to search for causal relationships. FIG. 7A is a diagram showing an example of inputting the probability of the path between the top event and the terminal event according to the first embodiment of the present invention, and FIG. 7B is an example of displaying only the factors above the threshold input in FIG. 7A. FIG. 4 is a diagram showing;

As shown in FIG. 7A, the output device 106 is provided with a threshold input screen 701 . The threshold input screen 701 is provided with an input section 702 for inputting a threshold, and an arbitrary numerical value is input to this input section 702 as the probability of the path between the top event and the terminal event. For example, a threshold value of 0.2 is input to the input unit 702 . If there is no error in the numerical values entered in the input unit 702, the user presses the "OK" button 703, and presses the "Cancel" button 704 to cancel. After inputting 0.2 into the input unit 702 , when the “OK” button 703 is pressed, the display content 705 is displayed on the output device 106 .

In FIG. 7B, for the output result of FIG. 6, only the factors that are equal to or greater than the threshold 0.2 input in FIG. 7A are displayed as a fault tree. That is, in FIG. 6, the probability of the path between the top event and the terminal event of "piping impact" 605 is 0.24, and the probability of the path between the top event and the terminal event of "piping wet condition" 608 is 0.24. 63, the probabilities of these two are 0.2 or more, so the display content 705 displays the peak event and the terminal event leading to "pipe impact" 605 and "pipe wetness" 608. "Initial Cracks in Piping" 604 and "Sea Water Intrusion in Piping" 607 are not displayed as display content 705 because the probability of the path between the top event and the terminal event is less than 0.2.

According to the first embodiment, by excluding low-probability factors, only high-probability factors can be examined more efficiently.

A second embodiment will now be described with reference to FIG. The inter-event causal probability calculation unit 111 of the first embodiment performs processes (1) to (4). For example, assume that 100 causal relationships in the nuclear power field have been acquired by process (1). Next, in process (2), assume that the causal relationships obtained in (1) include 20 causal relationships including "top event". Next, in the process (3), it is assumed that two "top events" whose cause is "factor A" are included. In process (4), the number of cases acquired in process (3) is divided by the number of cases acquired in process (2). In this case, the probability that the cause of the "top event" is "Factor A" is 2/20, which is 0.1.

In the second embodiment, instead of calculating the probability, the number of causal relationships in which the cause of the "top event" is "factor A" is evaluated. In other words, in the above example, the number of causal relationships including the "top event" is not divided by 20. ” has priority. Similarly, the priority of each factor from the top event to the terminal event is calculated. An output example is shown in FIG. FIG. 8 is a diagram showing an example in which causal relationships according to the second embodiment of the present invention are displayed by the number of cases. In FIG. 8, the number of causal relationships is displayed instead of the probabilities shown in FIG. Below each factor, the number of causal relationships is displayed.

In the first embodiment, the probabilities between events are multiplied, and the probability of the path between the top event and the terminal event is displayed in [ ] of the terminal event. In the second embodiment, the probability is calculated and displayed. Therefore, only the number of causal relationships is calculated and displayed for each factor, and [ ] of the end event is not displayed. This process is executed by the central controller 104 (controller).

According to the second embodiment, by displaying the number of causal relationships, the user can determine the priority based on the actual number of occurrences.

In the first embodiment, the threshold of the probability of the path between the top event and the terminal event can be input, and only the factors whose probability of the path between the top event and the terminal event is equal to or higher than the threshold are displayed. In the example, a threshold may be input with respect to the number of causal relationships, and only the factors equal to or greater than the threshold may be displayed. In this case, by excluding low-probability factors, only high-probability factors can be examined more efficiently.

DESCRIPTION OF SYMBOLS 101... Failure factor priority presentation apparatus, 102... Terminal device, 103... Network, 104... Central control apparatus (control apparatus), 105... Input device, 106... Output device, 107... Main storage device, 108... Auxiliary storage device, 109 Field input unit 110 Fault tree input unit 111 Inter-event causal probability calculator 112 Causal relationship database 200 Causal relationship

Claims (3)

a causal relationship database that stores causal relationships representing a chain of multiple elements including parts and phenomena regarding the occurrence of product defects;
an output device that branches from the top event to the terminal event and displays a failure tree related to product failure occurrence;
an event-to-event causality probability calculation unit that calculates the probability of a path from the top event to the terminal event from the causality stored in the causality database;
comprising an intermediate event prior to the terminal event and subsequent to the apex event;
The inter-event causal probability calculation unit
causing the path probabilities of the top event and the intermediate event to be displayed within the intermediate event of the fault tree;
A fault characterized in that the probability of a path between the intermediate event and the terminal event and the probability calculated by multiplication by the inter-event causal probability calculation unit are displayed together and distinguished in the terminal event of the fault tree. Factor priority presentation device. In claim 1 ,
1. A fault factor priority presentation device, comprising: a field input unit, wherein the output device displays the fault tree indicating the causal relationship of failures related to the field input by the field input unit. In claim 1 ,
The fault factor priority presentation device, wherein the output device is provided with an input unit capable of inputting a threshold value, and only the factors above the threshold value inputted from the input unit are displayed as the fault tree.

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