Apparatus, method and computer program for identifying defective devices

An apparatus for identifying a path pattern of devices that produces a defective product in a production line where a product is produced via a plurality of device is provided. The device is configured to estimate a path pattern quality indicating a quality of a group of products produced through a production path included in a path pattern, based on a production path quality and an association relationship between a path pattern and a production path indicating devices via which the product is produced and an order of passing through the devices; and to identify a path pattern suspected to be defective based on the estimated path pattern quality.

TECHNICAL FIELD

The present invention relates to an apparatus, method and computer program for identifying a pattern of devices that produces a defective product in a production line where a product is produced via a plurality of devices.

BACKGROUND ART

Hitherto, there has been known a technology of identifying a device suspected to be defective such as failure or cyberattack from the outside, in a production line where a product is produced via a plurality of devices (e.g., refer to Patent Literature 1).

In Patent Literature 1, there is described a method for identifying a device suspected to be defective, in a production line of a factory or a plant, by visualizing a product quality for each device based on a quality of a product and a production path indicating devices through which the product has been produced.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

Now, consideration a case in which, in a production line where a product is produced via a plurality of devices, e.g. Device 1 and Device 2 are configured to perform a drilling process, and Device 3 and Device 4 are configured to perform a screwing process. In this case, a combination of the drilling process and the screwing process may be changed flexibly depending on an operation status of each device.

However, there may be a path pattern that produces a defective product depending on a combination of the devices. As an example, there may occur a phenomenon that the quality of a product passing through Device 3 after Device 1, the quality of a product passing through Device 4 after Device 1 and the quality of a product passing through Device 3 after Device 2 are all normal, but only the quality of a product passing through Device 4 after Device 2 is defective.

The phenomenon described above may occur, e.g. when a hole made in Device 1 falls within a range of an allowable error but deviates to the left a little, a hole made in Device 2 falls within a range of an allowable error but deviates to the right a little, a screw inserted in Device 3 is accurately inserted at the center, and a screw inserted in Device 4 falls within a range of an allowable error but deviates to the left a little. This phenomenon can be said that a defective product is produced due to a negative interaction between Device 2 and Device 4.

With the method described in Patent Literature 1, it is possible to identify a single device that produce a defective product. However, it is not possible to identify a path pattern of devices that produces a defective product. In the above-mentioned example, it is not possible to identify a path pattern that produces a defective product when there is a pattern in which a product passes through Device 4 after Device 2.

Meanwhile, there may be not only a path pattern in which Device 2 and Device 4 are next to each other, but also a path pattern in which one or more other devices are arranged between Device 2 and Device 4. Then, also in a path pattern including one or more other devices between Device 2 and Device 4 in this manner, a defective product may be produced through a path pattern in which Device 2 precedes Device 4 due to the negative interaction between Device 2 and Device 4. Further, the number of devices having a negative interaction is not limited to two, and there may be a situation in which a defective product is produced when the product passes through three or more devices.

More generally, when there is a sequential order of two or more devices having a negative interaction in a path pattern of devices that produces a defective product, it is important to identify such a sequential order of the plurality of devices. However, with the related art described in Patent Literature 1, the sequential order of two or more devices having the negative interaction cannot be identified.

The present invention has been made to solve the above-mentioned problem, and has an object to provide an apparatus, method and computer program, which can identify a sequential order of two or more devices that produces a defective product in a production line where a product is produced via a plurality of devices.

Solution to Problem

In order to achieve the above-mentioned object, according to one embodiment of the present invention, there is provided an apparatus for identifying a path pattern of devices that produces a defective product in a production line where a product is produced via a plurality of devices, the apparatus comprising: a production path extractor configured to extract a production path indicating devices via which the product is produced and an order of passing through the devices; a production path quality generator configured to generate a production path quality indicating a quality of a group of products produced through the production path; a path pattern generator configured to generate a possible path pattern indicating devices via which the product is produced and an order of passing through the devices, in accordance with a number of indispensable devices indicating a number of devices that must be included in the path pattern; an association relationship generator configured to generate an association relationship between the production path and the path pattern; a path pattern quality estimator configured to estimate a path pattern quality indicating a quality of a group of products produced through a production path included in the path pattern, based on the association relationship and the production path quality; and a defective path pattern identifier configured to identify a defective path pattern for which a value of the path pattern quality is equal to or larger than a predetermined threshold value.

Advantageous Effects of Invention

The apparatus, method and computer program according to the present invention have a configuration which can identify a sequential order of two or more devices that produces a defective product based on known data on the production path and the production path quality. As a result, it is possible to identify the sequential order of two or more devices that produces a defective product in the production line where the product is produced via the plurality of devices.

DESCRIPTION OF EMBODIMENTS

Now, details of embodiments of the present invention are described with reference to the accompanying drawings. However, it should be noted that the embodiments described below are merely examples, and the present invention is not limited to those embodiments.

First Embodiment

FIG. 1is a configuration diagram of a first embodiment of the present invention. A factory301includes various kinds of devices10to15for processing a product. Further, the factory301includes an apparatus for monitoring quality302configured to monitor a production path and a quality of a product to be produced. The apparatus for monitoring quality302transmits, to an apparatus for identifying defective101, information containing the production path and the quality of a product to be produced in the factory301.

(Configuration of Apparatus for Monitoring Quality302)

First, the configuration of the apparatus for monitoring quality302is described. The apparatus for monitoring quality302is constructed by a well-known computer. The apparatus for monitoring quality302comprises a quality monitor303and a quality transmitter304. Those components303and304of the apparatus for monitoring quality302may be constructed by hardware, or may be implemented as software of programs to be executed by a CPU (not shown) of the apparatus for monitoring quality302.

The quality monitor303is configured to monitor the production path and the quality of a product to be produced in the factory301, and to create information containing the production path and the quality of a product. The quality transmitter304is configured to transmit, to the apparatus for identifying defective101, information containing the production path and the quality of a product, which has been created by the apparatus for monitoring quality302.

InFIG. 1, the apparatus for identifying Defective101may be connected to a plurality of apparatus for monitoring quality302of a plurality of factories301. Further, the apparatus for identifying defective101may be connected to the plurality of apparatus for monitoring quality302through a network configuration in which the plurality of apparatus for monitoring quality302form hierarchical structure.

(Configuration of Apparatus for Identifying Defective101)

Next, the configuration of the apparatus for identifying defective101is described. The apparatus for identifying defective101is constructed by a well-known computer. The apparatus for identifying defective101comprises a product information receiver111, a production path extractor112, a production path quality generator113, a path pattern generator114, an association relationship generator115, a path pattern quality estimator116, an defective path pattern identifier117and a storage region120.

Those components111to117of the apparatus for identifying defective101may be constructed by hardware, or may be implemented as software of programs to be executed by a CPU (not shown) of the apparatus for identifying defective101.

The product information receiver111is configured to receive information containing the production path and the quality of a product, which has been transmitted from the apparatus for monitoring quality302, and to store the received information into product information121of the storage region120.

FIG. 2Ashows an example of data structure of the product information121. The product information121contains a product ID211, a production path212and a product quality213.

The product ID211is a unique identifier for identifying a product. The production path212is a character string representing devices via which the product is produced and an order of passing through those devices. For example, the production path212is a character string of “{Device 1, Device 2, Device 3}.” The product quality213is information representing the quality of the product. The product quality213takes a real number equal to or larger than 0 and equal to or smaller than 1, and a larger value indicates a higher quality.

The production path and the quality of a product may not be received at the same time. In other words, the production path and the quality may be received in any order as long as the production path and the quality can be associated with each other by a separate product ID.

The production path extractor112is configured to extract, for each product, a production path through which the product is produced based on the product information121ofFIG. 2A, to merge overlapped production paths, and to store the merged production path into production path information122of the storage region120.

The production path quality generator113is configured to generate, for each production path extracted and merged by the production path extractor112, a production path quality indicating a quality of a group of products produced through the production path, and to store the generated production path quality into the production path information122of the storage region120.

FIG. 2Bshows an example of data structure of the production path information122. The production path information122contains a production path ID221, a production path222and a production path quality223.

The production path ID221is a unique identifier for identifying a production path through which a product is produced. The production path222is a character string representing devices via which the product is produced and an order of passing through those devices. The production path quality223is information indicating a quality of a group of products produced through the production path.

For example, the production path quality223is defined by the following expression.

In the expression given above, the production path quality223takes a value of 0 when the production path quality223is normal, whereas the production path quality223takes a value other than 0 when the production path quality223is defective. When the production path quality223takes a value other than 0, the magnitude of the value indicates a degree of defectiveness of a group of products produced through the production path.

The path pattern generator114is configured to generate a possible “path pattern(s)” representing devices via which a product is produced and an order of passing through those devices, based on the production path222of the production path information122ofFIG. 2B, and to store the path pattern(s) into path pattern information123of the storage region120.

Now, the concept of the “path pattern(s)”, which is a feature of the invention of the present application, is described. Each of the “path pattern(s)” is a possible pattern representing devices via which a product is produced and an order of passing through those devices. The path pattern(s) can be generated when the devices included in the production path information ofFIG. 2Band the “number of indispensable devices,” which is the number of devices that must be included in the pattern(s), are specified.

Further, when a certain Path Pattern A is included in a certain Production Path B, it is said that “Path Pattern A matches Production Path B.” Further, when a certain Path Pattern A is not included in a certain Production Path B, it is said that “Path Pattern A does not match Production Path B.”

The symbol “*” in the above-mentioned path patterns is a Wild Card indicating that any number of devices including zero device may be included. For example, regarding Path Pattern (Device 1, *, Device 2), this pattern matches two production paths, i.e. {Device 1, Device 2, Device 3, Device 5} and {Device 1, Device 3, Device 2} among the production paths ofFIG. 2B. In other words, Path Pattern (Device 1, *, Device 2) matches a production path(s) in which the sequential order of Device 1 and Device 2 is included.

FIG. 2Cshows an example of data structure of the path pattern information123. The path pattern information123contains a path pattern ID231, a path pattern232and a path pattern quality233.

The path pattern ID231is a unique identifier for identifying a path pattern. As described above, the path pattern232is a character string which represents a possible pattern(s) representing devices via which a product is produced and an order of passing through those devices. There may be a path pattern that does not match any one of production paths ofFIG. 2B, and such a path pattern is excluded so as to reduce the amount of calculation.

The path pattern quality233is information indicating the quality of a group of products produced through a production path(s) matching the path pattern.

The path pattern quality233takes a value equal to or smaller than a predetermined threshold value when the path pattern quality233is normal, whereas the path pattern quality233takes a value larger than the threshold value when the path pattern quality233is defective. When the path pattern quality233takes a value larger than the threshold value, the magnitude of the value indicates a degree of defectiveness of a group of products produced through the production path(s) matching the path pattern.

The path pattern quality233is unknown at the time of generation of a path pattern(s) by the path pattern generator114, and is initialized by an expression enabling distinction from invalidity, for example “N/A”.

The association relationship generator115is configured to extract an association relationship between the production path222and the path pattern232based on the production path information122ofFIG. 2Band the path pattern information123ofFIG. 2C, and to store the extracted association relationship into association relationship information124of the storage region120.

FIG. 2Dshows an example of data structure of the association relationship information124. The association relationship information124contains a production path ID241and a path pattern ID242.

The production path ID241is an arrangement of production path IDs stored in the production path ID221of the production path information122ofFIG. 2Bin a row direction. The path pattern ID242is an arrangement of path pattern IDs stored in the path pattern ID231of the path pattern information123ofFIG. 2Cin a column direction.

Regarding the association relationship information124ofFIG. 2D, considering a cell at which the production path ID241and the path pattern ID242intersect with each other, for example a cell243at which Production Path 1 and Path Pattern 1 intersect with each other. When Production Path 1 matches Path Pattern 1, “1” is stored in the cell243. When Production Path 1 does not match Path Pattern 1, “0” is stored in the cell243.

Alternatively, when Production Path 1 matches Path Pattern 1, a value that is larger than 0 and depends on the degree of Production Path 1 matching Path Pattern 1 may be stored.

The path pattern quality estimator116is configured to estimate the quality of each path pattern, i.e. the quality of a group of products produced through the production path(s) matching the path pattern based on the association relationship information124ofFIG. 2Dand the production path quality223of the production path information122ofFIG. 2B, and to store the estimated quality of each path pattern into the path pattern quality233of the path pattern information123ofFIG. 2C.

An example of the method of estimating the path pattern quality233is estimating the path pattern quality on the assumption that the production path quality is obtained as a linear observation of the path pattern quality based on the association relationship between the production path and the path pattern.

Specifically, the production path quality223of the production path information122ofFIG. 2B, the path pattern quality233of the path pattern information123ofFIG. 2Cand the association relationship information124ofFIG. 2Dare set as a constant vector y, a variable vector x and a matrix A, respectively, and these are substituted into a definition expression of linear observation. As a result, the following equation is obtained.
∥y−Ax∥

On the basis of the equation given above, the variable vector x is estimated by solving an optimization problem of calculating x that minimizes the following cost function under a constraint condition x≥0.
∥y−Ax∥

The defective path pattern identifier117is configured to identify a path pattern(s) for which the value of the path pattern quality is equal to or larger than a predetermined threshold value as a “defective path pattern(s)” based on the path pattern information123ofFIG. 2Cincluding the estimated path pattern quality.

Further, the defective path pattern identifier117is configured to extract a device(s) commonly included in the defective path pattern(s) as a device(s) suspected to be defective, and to identify the extracted device(s) in an order of degree of defectiveness. A method of setting the order of degree of defectiveness is considered to be, for example setting the order by prioritizing devices commonly included in the defective path pattern(s) having a larger value of the path pattern quality. The defective path pattern identifier117outputs the identified device(s) to a monitor (not shown) as a device(s) suspected to be defective such as failure or cyberattack from the outside.

(Operation of Apparatus for Identifying Defective101)

Next, an operation of the apparatus identifying Defective101according to the first embodiment of the present invention is given, with reference to the flow chart illustrated inFIG. 3. It is assumed that, at the time of start of the flow chart ofFIG. 3, information containing the production path and the quality of a product, which has been transmitted from the apparatus for monitoring quality302, is previously received by the product information receiver111, and the storage region120has stored the received information as the product information121(FIG. 2A).

In Step S101, for each product, the production path extractor112extracts a production path through which the product is produced based on the product information121ofFIG. 2A, and merges overlapped production paths. The production path extractor112stores the extracted and merged production path into the production path information122ofFIG. 2Bas the production path ID221and the production path222.

In Step S102, for each production path, the production path quality generator113generates a production path quality indicating the quality of a group of products produced through the production path. The production path quality generator113stores the generated production path quality into the production path information122ofFIG. 2Bas the production path quality223.

In Step S103, the path pattern generator114specifies “1” as the “number of indispensable devices” described above based on the production path222of the production path information122ofFIG. 2B, and generates a possible path pattern(s). There may be a path pattern that does not match any one of production paths ofFIG. 2B, and such path pattern is excluded so as to reduce the amount of calculation. The path pattern generator114stores the generated path pattern(s) into the path pattern information123ofFIG. 2Cas the path pattern ID231and the path pattern232. At this time, the path pattern quality233is initialized by an expression enabling distinction from invalidity, for example “N/A”.

In Step S104, the association relationship generator115extracts an association relationship between the production path222and the path pattern232based on the production path information122ofFIG. 2Band the path pattern information123ofFIG. 2C, and stores the extracted association relationship into the association relationship information124ofFIG. 2D.

In Step S105, the path pattern quality estimator116estimates the quality of each path pattern based on the association relationship information124ofFIG. 2Dand the production path quality223of the production path information122ofFIG. 2B. The path pattern quality estimator116stores the estimated quality of each path pattern into the path pattern information123ofFIG. 2Cas the path pattern quality233.

In Step S106, the path pattern generator114determines whether a predetermined exit condition is satisfied. Specifically, the path pattern generator114extracts, from the path pattern information123ofFIG. 2C, all the path patterns for which the value of the path pattern quality is equal to or larger than a predetermined threshold value.

If the number of path patterns extracted in Step S106is equal to or larger than a predetermined value, or the number of times of execution of Step S105, i.e. the number of times of estimation of the path pattern quality is equal to or larger than a predetermined number of times, the path pattern generator114determines that the exit condition has been satisfied, and the process goes to Step S107. Otherwise, the path pattern generator114determines that the exit condition has not been satisfied, and the process goes to Step S108.

Alternatively, the path pattern generator114may compare the tendency of the path pattern quality estimated at the previous iteration with the tendency of the path pattern quality estimated at the current iteration to determine whether the comparison result converges to a predetermined range.

Further alternatively, the path pattern generator114may record the number of path patterns extracted in Step S106while incrementing the “number of indispensable devices” by one. And when the “number of indispensable devices” with the least number of extracted path patterns is identified, the path pattern generator114may determine that the exit condition is satisfied.

In general, when considering a graph with the number of indispensable devices as the horizontal axis and the number of extracted path patterns as the vertical axis, this graph tends to be convex downward. Further, identifying the number of indispensable devices with the least number of extracted path patterns means that identifying the number of indispensable devices with the minimum value of the graph.

In Step S107, the path pattern generator114increments the “number of indispensable devices” by one, and generates a possible path pattern(s). The path pattern generator114stores the generated path pattern(s) into the path pattern information123ofFIG. 2C. At this time, the path pattern quality233is initialized by an expression enabling distinction from invalidity, for example “N/A”. After that, the process returns to Step S104.

In Step S108, the defective path pattern identifier117identifies, based on the path pattern information123ofFIG. 2C, a path pattern(s) for which the value of the path pattern quality is equal to or larger than a predetermined threshold value, as a “defective path pattern(s)” suspected to produce a defective product.

In Step S109, the defective path pattern identifier117identifies a device(s) commonly included in the defective path pattern(s) identified in Step S108. The defective path pattern identifier117outputs the identified device(s) to the monitor (not shown) as a device(s) suspected to be defective such as failure or cyberattack from the outside.

Next, description is made of a specific example of identifying a “defective path pattern(s)” suspected to produce a defective product by the apparatus for identifying defective101according to the first embodiment of the present invention with reference toFIG. 4toFIG. 7.

In the example of the production path information122shown inFIG. 4, there are twenty production paths, i.e. Path 1 to Path20, and Device 1 to Device 5 are arranged on the way of those production paths.

For example, if “2” is specified as the “number of indispensable devices”, the path pattern information123shown inFIG. 5is obtained from the production path information122ofFIG. 4. InFIG. 5, a path pattern(s) that does not match any one of production paths ofFIG. 4is excluded.

Further, the association relationship information124shown inFIG. 6is obtained from the production path information122ofFIG. 4and the path pattern information123ofFIG. 5. The description of “PT” inFIG. 6means “Pattern”.

The path pattern quality233shown inFIG. 7is estimated fromFIG. 4toFIG. 6. Referring toFIG. 7, it can be understood that a product produced through a production path(s) matching a Path Pattern (Device 2, *, Device 3), i.e. a path pattern in which Device 3 is arranged after Device 2 and zero or more devices are arranged between Device 3 and Device 2, has low quality. Whereas, products produced through other production paths has high quality.

The defective path pattern identifier117of the apparatus for identifying defective101identifies (Device 2, *, Device 3) as a “defective path pattern” suspected to produce a defective product.

As described above, the apparatus for identifying defective according to the first embodiment of the present invention estimates a path pattern quality indicating the quality of a group of products produced through a production path matching a path pattern based on the association relationship between the production path and the path pattern and the production path quality, and identifies a path pattern suspected to produce a defective product based on the estimated path pattern quality.

With the above-mentioned feature, if there is a path pattern(s) including a device(s) that produces a defective product in a production line where a product is produced via a plurality of devices, it is possible to identify such a pattern(s).

Second Embodiment

FIG. 8is a configuration diagram of a second embodiment of the present invention. In the second embodiment, it is possible to handle a defective situation in which the path pattern quality worsens over time.

(Configuration of Apparatus for Monitoring Quality2302)

An apparatus for monitoring quality2302comprises a quality monitor2303and a quality transmitter2304. The quality monitor2303is configured to monitor the production path and the quality of a product produced in the factory301as well as the time of measuring the quality, and to create information containing the production path and the quality of a product as well as the time of measuring the quality. The quality transmitter2304transmits, to the apparatus for identifying defective2101, the information containing the production path and the quality of a product as well as the time of measuring the quality which has been created by the apparatus for monitoring quality2303.

(Configuration of Apparatus for Identifying Defective2101)

The apparatus for identifying defective2101comprises a product information receiver2111, a production path extractor2112, a production path quality generator2113, a path pattern generator2114, an association relationship generator2115, a path pattern quality estimator2116and a defective path pattern identifier2117. Those components are constructed by adding a concept of the time of measuring the product quality to the apparatus for identifying defective101in the first embodiment.

Next, the data structure in the second embodiment is described with reference toFIG. 9AtoFIG. 9D. The data structure in the second embodiment is constructed by adding the concept of the time of measuring the product quality to the data structure in the first embodiment.

FIG. 9Ashows an example of data structure of a product information1010in the second embodiment. The product information1010contains a product ID1011, a production path1012, a quality measurement time1013and a product quality1014.

The product ID1011, the production path1012and the product quality1014are the identical as those contained in the product information121in the first embodiment. The quality measurement time1013is a time at which the product quality has been measured.

FIG. 9Bshows an example of data structure of a production path information1020in the second embodiment. The production path information1020contains a production path ID1021, a production path1022, a measurement start time1023, a measurement end time1024and a production path quality1025.

The production path ID1021, the production path1022and the production path quality1025are the identical as those contained in the production path information122in the first embodiment.

The measurement start time1023and the measurement end time1024are specified by the defective path pattern identifier2117described in detail later, and specify a range of time period of measuring the product qualities to be aggregated into the production path quality1025. For example, if the measurement start time is specified as t1 and the measurement end time is specified as t2 respectively, only the product qualities measured between the time t1 and the time t2 are aggregated into the production path quality.

FIG. 9Cshows an example of data structure of a path pattern information1030in the second embodiment. The path pattern information1030contains a path pattern ID1031, a path pattern1032, a measurement start time1033, a measurement end time1034and a path pattern quality1035.

The path pattern ID1031, the path pattern1032and the path pattern quality1035are the identical as those contained in the path pattern information123in the first embodiment.

The measurement start time1033is a time of starting to measure a production path quality matching the path pattern. The measurement end time1034is a time of finishing to measure the production path quality matching the path pattern.

FIG. 9Dshows an example of data structure of an association relationship information1040in the second embodiment. The association relationship information1040contains a production path ID1041and a path pattern ID1042.

The production path ID1041and the path pattern ID1042are the identical as those contained in the association relationship information124in the first embodiment.

(Operation of Apparatus for Identifying Defective2101)

Next, an operation of the apparatus for identifying Defective2101according to the second embodiment of the present invention is given, with reference to flow charts illustrated inFIG. 10andFIG. 11. It is assumed that, at the time of start of the flow charts ofFIG. 10andFIG. 11, information containing the production path and the quality of a product, which has been transmitted from the apparatus for monitoring quality2302, and the time of measuring the quality is previously received by the product information receiver2111, and a storage region2120has stored the received information as the product information2121(FIG. 9A).

First, the process of the flow chart illustrated inFIG. 10is described. The flow chart ofFIG. 10is created by adding the concept of the time of measuring the product quality to the flow chart ofFIG. 3in the first embodiment. The process of the flow chart ofFIG. 10is repeatedly called from Step S2201of the flow chart ofFIG. 11described next.

In Step S2101, for each product that the quality has been measured between the measurement start time and the measurement end time specified by the defective path pattern identifier2117, the production path extractor2112extracts, a production path through which the product is produced based on the product information1010ofFIG. 9A, and merges overlapped production paths. The production path extractor2112stores the extracted and merged production path into the production path information2020ofFIG. 9Bas the production path ID1021, the production path1022, the measurement start time1023and the measurement end time1024.

In Step S2102, for each production path extracted and merged in Step S2101, the production path quality generator2113generates, a production path quality indicating the quality of a group of products produced through the production path. The production path quality generator2113stores the generated production path quality into the production path information1020ofFIG. 9Bas the production path quality1025.

In Step S2103, the path pattern generator2114specifies “1” as the “number of indispensable devices” and generates a possible path pattern(s) based on the production path1022of the production path information1020ofFIG. 9B. The path pattern generator2114stores the generated path pattern(s) into the path pattern information1030ofFIG. 9Cas the path pattern ID1031, the path pattern1032, the measurement start time1033and the measurement end time1034. At this time, the path pattern quality1035is initialized by an expression enabling distinction from invalidity, for example “N/A”.

In Step S2104, the association relationship generator2115extracts an association relationship between the production path1022and the path pattern1032based on the production path information1020ofFIG. 9Band the path pattern information1030ofFIG. 9C, and stores the extracted association relationship into the association relationship information1040ofFIG. 9D.

In Step S2105, the path pattern quality estimator2116estimates the quality of each path pattern based on the association relationship information1040ofFIG. 9Dand the production path quality1025of the production path information1020ofFIG. 9B. The path pattern quality estimator2116stores the estimated quality of each path pattern into the path pattern information1030ofFIG. 9Cas the path pattern quality1035.

In Step S2106, the path pattern generator2114determines whether a predetermined exit condition is satisfied. Specifically, the path pattern generator2114extracts, from the path pattern information1030ofFIG. 9C, all the path patterns for which the value of the path pattern quality is equal to or larger than a predetermined threshold value. If the number of extracted path patterns is equal to or larger than a predefined value, or the number of times of execution of Step S2105, i.e. the number of times of estimation of the path pattern quality is equal to or larger than a predetermined of number of times, the path pattern generator2114determines that the exit condition has been satisfied, and the process goes to Step S2108. Otherwise, the path pattern generator2114determines that the exit condition has not been satisfied, and the process goes to Step S2107.

In Step S2107, the path pattern generator2114increments the “number of indispensable devices” by one, and generates a possible path pattern(s). The path pattern generators2114stores the generated path pattern(s) into the path pattern information1030ofFIG. 9C. At this time, the path pattern quality1035is initialized by an expression enabling distinction from invalidity, for example “N/A”. After that, the process returns to Step S2104.

In Step S2108, the defective path pattern identifier2117identifies, based on the path pattern information1030ofFIG. 9C, a path pattern(s) for which the value of the path pattern quality is equal to or larger than a predetermined threshold value, as a “defective path pattern(s)” suspected to produce a defective product.

In Step S2109, the defective path pattern identifier2117identifies a device(s) commonly included in the defective path pattern(s) identified in Step S2108. The defective path pattern identifier2117outputs the identified device(s) to the monitor (not shown) as a device(s) suspected to be defective such as failure or cyberattack from the outside.

Next, the process of the flow chart illustrated inFIG. 11is described. As described above, the process of the flow chart ofFIG. 10is repeatedly called from Step S2201of the flow chart ofFIG. 11.

In Step S2201, the defective path pattern identifier2117specifies a plurality of time ranges, and calls the process of the flow chart ofFIG. 10in the plurality of number of times. In each call, the defective path pattern identifier2117obtains all the path patterns included inFIG. 9Cwhen the exit condition of Step S2106ofFIG. 10is satisfied.

For example, the following process is executed if first to third time ranges are specified, and the process of the flow chart ofFIG. 10is called in three times.

First, in the first time, the defective path pattern identifier2117specifies a measurement start time t0 and a measurement end time t1 as the first time range, and calls the process ofFIG. 10. Then, the defective path pattern identifier2117obtains all the path patterns included inFIG. 9Cwhen the exit condition of Step S2106ofFIG. 10is satisfied.

Next, in the second time, the defective path pattern identifier2117specifies the measurement start time t1 and a measurement end time t2 as the second time range, and calls the process ofFIG. 10. Then, the defective path pattern identifier2117obtains all the path patterns included inFIG. 9Cwhen the exit condition of Step S2106ofFIG. 10is satisfied.

Finally, in the third time, the defective path pattern identifier2117specifies the measurement start time t2 and a measurement end time t3 as the third time range, and calls the process ofFIG. 10. Then, the defective path pattern identifier2117obtains all the path patterns included inFIG. 9Cwhen the exit condition of Step S2106ofFIG. 10is satisfied.

In Step S2202, the defective path pattern identifier2117goes to Step S2203if there is a path pattern(s) for which the temporal transition of the path pattern quality for the past three times deviates from a predetermined range. Otherwise, the defective path pattern identifier2117finishes the process.

In Step S2203, the defective path pattern identifier2117identifies the path pattern(s) for which the temporal transition of the path pattern quality for the past three times deviates from the predetermined range as a “defective path pattern(s)”.

In Step S2204, the defective path pattern identifier2117identifies a device(s) commonly included in the defective path pattern(s) identified in Step S2203. The defective path pattern identifier2117outputs the identified device(s) to the monitor (not shown) as a device(s) suspected to be defective such as failure or cyberattack from the outside.

FIG. 12shows an example of the temporal transition of the path pattern quality obtained by the apparatus for identifying defective2101according to the second embodiment of the present invention.

The circles represent a case in which the value of the path pattern quality in each of time ranges T1 to T3 and the temporal transition of the value of the path pattern quality are both normal. The symbol “Th” ofFIG. 12represents a predetermined threshold value, which is used in Step S2106ofFIG. 10.

The triangles represent a case in which the value of the path pattern quality in the time range T2 is defective.

The squares represent a case in which the temporal transition of the value of the path pattern quality in each of the time ranges T1 to T3 is defective. A region below the line R ofFIG. 12is a predetermined range, which is used in Step S2202ofFIG. 11.

As described above, the apparatus for identifying defective2101according to the second embodiment of the present invention further identifies a path pattern(s) for which the temporal transition of the value of the path pattern quality deviates from a predetermined range as a defective path pattern(s). With this, in addition to the advantageous effects obtained in the first embodiment, it is possible to handle a defective situation in which the path pattern quality worsens over time.

REFERENCE SIGNS LIST

101,2101apparatus for identifying defective,112,2112production path extractor,113,2113production path quality generator,114,2114path pattern generator,115,2115association relationship generator,116,2116path pattern quality estimator,117,2117defective path pattern identifier