WO2020188696A1 - 異常検知装置および異常検知方法 - Google Patents
異常検知装置および異常検知方法 Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M99/00—Subject matter not provided for in other groups of this subclass
- G01M99/008—Subject matter not provided for in other groups of this subclass by doing functionality tests
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M99/00—Subject matter not provided for in other groups of this subclass
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F11/00—Error detection; Error correction; Monitoring
- G06F11/07—Responding to the occurrence of a fault, e.g. fault tolerance
- G06F11/0703—Error or fault processing not based on redundancy, i.e. by taking additional measures to deal with the error or fault not making use of redundancy in operation, in hardware, or in data representation
- G06F11/0706—Error or fault processing not based on redundancy, i.e. by taking additional measures to deal with the error or fault not making use of redundancy in operation, in hardware, or in data representation the processing taking place on a specific hardware platform or in a specific software environment
- G06F11/0736—Error or fault processing not based on redundancy, i.e. by taking additional measures to deal with the error or fault not making use of redundancy in operation, in hardware, or in data representation the processing taking place on a specific hardware platform or in a specific software environment in functional embedded systems, i.e. in a data processing system designed as a combination of hardware and software dedicated to performing a certain function
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F11/00—Error detection; Error correction; Monitoring
- G06F11/07—Responding to the occurrence of a fault, e.g. fault tolerance
- G06F11/0703—Error or fault processing not based on redundancy, i.e. by taking additional measures to deal with the error or fault not making use of redundancy in operation, in hardware, or in data representation
- G06F11/0751—Error or fault detection not based on redundancy
- G06F11/0754—Error or fault detection not based on redundancy by exceeding limits
- G06F11/076—Error or fault detection not based on redundancy by exceeding limits by exceeding a count or rate limit, e.g. word- or bit count limit
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06N—COMPUTING ARRANGEMENTS BASED ON SPECIFIC COMPUTATIONAL MODELS
- G06N3/00—Computing arrangements based on biological models
- G06N3/02—Neural networks
- G06N3/08—Learning methods
Definitions
- the present invention relates to an abnormality detection device and an abnormality detection method for determining an abnormality in an object for abnormality detection such as equipment such as a factory, a chemical plant, and a steel plant.
- control systems for controlling equipment such as air conditioning equipment and electric lighting in the equipment have been introduced.
- Control systems for controlling processes have also been introduced in facilities such as power plants, chemical plants, and steel plants, including thermal power, hydraulic power, and nuclear power.
- factory equipment, automobiles, railroad vehicles, and the like are often equipped with a logging system for recording the state of these equipment.
- the state of the equipment includes the state of the equipment provided in the equipment, the state indicating the environment inside or outside the equipment, and the like.
- Logging systems and control systems generally store time-series data, measured by sensors, that indicates the state of the equipment over time.
- Patent Document 1 describes an abnormality detection method in which features are extracted from time-series data, and when the distance between the extracted features and the features extracted from training data that does not include anomalies exceeds a threshold value, anomalies are determined. Is disclosed.
- the tendency of time series data may differ depending on the equipment in the equipment or the sensor that measures the state. Therefore, when performing a determination using a threshold value as in the method described in Patent Document 1, there is a problem that the threshold value needs to be evaluated and verified for each device and sensor. Further, the evaluation and verification of this threshold value requires external information such as the knowledge of a skilled operator and the knowledge of the equipment designer, so that the load on the operator and the designer is high and it takes time. Therefore, it is desired to suppress the workload for setting the threshold value.
- the present invention has been made in view of the above, and an object of the present invention is to obtain an abnormality detection device capable of detecting an abnormality of an object for abnormality detection by suppressing a workload for setting a threshold value. To do.
- the abnormality detection device has a data division unit that divides time-series data into a learning section and a test section, and a portion of the time-series data in the learning section. It includes a subsequence generation unit that generates columns as training data. Further, the abnormality detection device includes a prediction distribution calculation unit that obtains a probability distribution corresponding to a data point in a test section using learning data, and an abnormality detection unit that detects an abnormality using the probability distribution.
- the abnormality detection device has the effect of suppressing the workload for setting the threshold value and detecting the abnormality of the object for abnormality detection.
- FIG. 1 is a diagram showing a functional configuration example of the abnormality detection device according to the embodiment of the present invention.
- the abnormality detection device 100 of the present embodiment includes a data acquisition unit 101, a data division unit 102, a subsequence generation unit 103, a prediction distribution calculation unit 104, a credit interval calculation unit 105, and an abnormality score calculation.
- a unit 106 and an abnormality detection unit 107 are provided.
- the abnormality detection device 100 of the present embodiment acquires time-series data indicating the state of the object of abnormality detection, and detects the abnormality of the object of abnormality detection based on the acquired time-series data.
- the object of abnormality detection data on facilities such as factories, chemical plants, steel plants, water and sewage plants, automobiles, railroad vehicles, economy or management can be exemplified.
- the time series data is a data string including data corresponding to a plurality of different times, and is a data string in which the time change of the data can be grasped.
- the time series data may be any data, for example, a data string containing data observed at a plurality of different times, or data processed at a plurality of different times. It may be a data string containing the results.
- the time series data may be feedback data or the like used for control. That is, the time series data includes a plurality of data points corresponding to different times.
- the data point corresponds to one point when the time information indicating the time and the value such as the sensor value corresponding to the time are represented by the two-dimensional coordinate system.
- the time-series data is data in which sensor values measured by sensors at regular time intervals are arranged together with the acquisition time of the sensor values.
- the sensors include, for example, a temperature sensor that measures the temperature of equipment, equipment, etc., a sensor that detects the rotational position of a motor provided in a factory machine, a force sensor that measures the acceleration of a factory machine, a current sensor, and the like.
- a voltage sensor or the like Time-series data on exchange rates, stock prices, futures prices, etc. are exemplified as time-series data on the economy or management. Examples of the anomaly of these data include anomalies such as a sharp drop in price.
- Time-series data may be stored in, for example, processing machines that are equipment on the factory line, manufacturing equipment such as robot pumps, equipment such as automobiles and railroad vehicles, air conditioning equipment such as factories and buildings, electricity, and so on. It may be data stored in a control system such as lighting and water supply / drainage. Further, the time series data may be data accumulated in a control system for controlling processes of a power plant such as thermal power, hydraulic power, nuclear power, a chemical plant, a steel plant, a water and sewage plant, and the like. Further, the time series data may be data accumulated in an information system related to economy, management, or the like.
- the data acquisition unit 101 of the abnormality detection device 100 receives input of data such as settings used for the abnormality detection process.
- the data acquisition unit 101 may accept input of time series data.
- the data division unit 102 divides the time series data into a learning section and a test section, which will be described later.
- the subsequence generation unit 103 generates learning data that is a subsequence of the learning section of the time series data.
- the prediction distribution calculation unit 104 obtains the probability distribution corresponding to the data points in the test section based on the learning data.
- the credible interval calculation unit 105 calculates the credible interval corresponding to the data points of the test interval based on the probability distribution.
- the anomaly score calculation unit 106 calculates an anomaly score indicating the degree of deviation between the credit interval and the time series data of the test interval.
- the anomaly detection unit 107 detects an abnormality using the probability distribution calculated by the prediction distribution calculation unit 104.
- the abnormality detection unit 107 detects an abnormality based on, for example, an abnormality degree score. Details of the operation of each part of the abnormality detection device 100 will be described later.
- FIG. 2 is a diagram showing a configuration example of a computer system that realizes the abnormality detection device 100.
- the computer system includes a computer 20 and an input device 209 and a display 210 connected to the computer 20.
- the computer 20 includes a processor 201, an auxiliary storage device 202, a memory 203, an input interface (hereinafter abbreviated as I / F) 204, a display I / F 205, an alarm output device 206, and a network I / F 207.
- the processor 201 is connected to the auxiliary storage device 202, the memory 203, the input I / F 204, the display I / F 205, the alarm output device 206, and the network I / F 207 via the signal line 208.
- the processor 201 is, for example, a CPU (Central Processing Unit), an MPU (Micro Processing Unit), or the like.
- the auxiliary storage device 202 and the memory 203 are a RAM (Random Access Memory), a ROM (Read Only Memory), an HDD (Hard Disk Drive), and the like.
- the input I / F 204 is connected to the input device 209 via the cable 211.
- the input I / F 204 is a circuit for exchanging data with the input device 209.
- the input device 209 is a device that receives input from the user, and includes a keyboard, a mouse, and the like.
- the display I / F 205 is connected to the display 210 via the cable 212.
- the display I / F 205 is a circuit for exchanging data with the display 210.
- the input device 209 and the display 210 may be integrated and realized by a touch panel.
- the display 210 is an example of an output device, but in addition to the display 210, an output device such as a printer may be connected via the I / F of the output device.
- the alarm output device 206 is an indicator light such as an LED (Light Emitting Diode) pilot lamp, a speaker, and the like. Note that FIG. 2 shows an example in which the alarm output device 206 is provided inside the computer 20, but the present invention is not limited to this, and the alarm output device 206 is provided outside the computer 20 like the display 210 and has a cable. It may be connected to the computer 20 via.
- LED Light Emitting Diode
- the network I / F207 is a communication circuit for communicating with the outside, and is connected to a network (not shown) via a wired line or a wireless line. Other devices such as a computer (not shown) and a database server having a database are connected to the network.
- the network I / F 207 sends / receives e-mail to / from another device, receives data stored in the database of the other device, and stores data in the database of the other device. Send to the device of.
- each functional unit of the abnormality detection device 100 shown in FIG. 1 are realized by software, firmware, or a combination of software and firmware.
- the software, firmware, or software and firmware for realizing the functions of each functional unit of the abnormality detection device 100 are described as a program.
- This program is stored in the auxiliary storage device 202.
- This program causes the computer 20 to execute the procedure or method of each functional unit. Specifically, when the processor 201 executes the program, each functional unit of the abnormality detection device 100 shown in FIG. 1 is realized.
- the input device 209 is also used to realize the function of the data acquisition unit 101.
- at least one of the display 210 and the alarm output device 206 is used to realize the function of the abnormality detection unit 107.
- This program may be provided by a recording medium or a communication medium and stored in the auxiliary storage device 202.
- the above-mentioned time series data is stored in the auxiliary storage device 202.
- the time series data is transmitted from another device and stored in the auxiliary storage device 202 via the network I / F 207.
- the time series data may be stored in the auxiliary storage device 202 by being recorded on the recording medium and read from the recording medium, or may be input by the user via the input device 209.
- the program stored in the auxiliary storage device 202 is loaded from the auxiliary storage device 202 into the memory 203 and read into the processor 201 to be executed. By executing the program, the functions of each functional unit shown in FIG. 1 are realized. Further, when the program is executed, data used for executing the program such as time series data is also loaded from the auxiliary storage device 202 into the memory 203. The execution result of the program is written in the memory 203, stored in the auxiliary storage device 202, displayed on the display 210 via the display I / F 205, or displayed on the display 210 via the network I / F 207, depending on the description content of the program. It may be sent to other devices on the network.
- time-series data data measured by a plurality of types of sensors installed in a manufacturing apparatus continuously operating on a factory line
- the object of abnormality detection is a manufacturing apparatus
- the time series data is not limited to the data measured by the sensor.
- FIGS. 3 to 5 are diagrams showing an example of time series data.
- the sensor values 303 shown in FIGS. 3 to 5 are sensor values that are data measured at regular intervals by a plurality of types of sensors installed in a manufacturing apparatus that continuously operates on a factory line.
- the sensor value 303 is associated with time information 301 indicating the time when each data is acquired.
- the set of the time information 301 and the sensor value 303 is time series data.
- the plurality of types of sensors include the acceleration sensor A.
- the sensor value is not limited to the value measured by the acceleration sensor A, and the measured values of the current, voltage, vibration, acceleration, pressure, etc. of the manufacturing apparatus can be exemplified.
- time information 301 indicating the time when each data of the sensor value 303 is acquired and control information 302 indicating the control conditions of the manufacturing apparatus are shown together with the sensor value 303.
- the control information 302 is, for example, recipe information which is a command value related to the number of manufactured products, which is the number of manufactured products, and the manufacturing conditions.
- the command value is, for example, the command value of the motor speed in the case of a rotating mechanism, the command value of the temperature at the time of welding in the case of a welding device, and the laser in the case of a laser processing machine. This is the command value of the output voltage.
- the recipe information will be explained. Depending on the product, the command value may be changed in several stages.
- Some command value change patterns, a set of processing conditions, and the like are called recipes.
- An example of a rotating mechanism is a vacuum pump in semiconductor manufacturing. In a vacuum pump, air is discharged by rotating a motor to create a vacuum state.
- chemicals, gas, etc. are applied to the wafer.
- the types of chemicals, gases, etc. differ depending on the product type.
- the application timing of chemicals, gas, etc. differs depending on the product, and the rotation speed of the motor differs depending on the product. For example, the rotation speed of the motor is A before the gas is charged, the rotation speed of the motor is B when the gas is charged, and the rotation speed of the motor is C after the gas is charged.
- Recipe information is information that indicates these procedures.
- the control information 302 includes the command value 1.
- the control information 302 is recorded as state information together with the time information 301 and the sensor value 303 which are time series data.
- the state information is recorded by, for example, a control device that controls the manufacturing device, and the abnormality detection device 100 acquires the state information from this control device via the network.
- the time information 301 is indicated by the time, but the time information is not limited to the time itself, and may be a continuous number assigned mechanically. It may be a numerical value such as a row number of a matrix.
- the time information may not be added to each sensor as long as the data are arranged in the order of acquisition time.
- the start time of the time-series data is managed separately by being described in the file name of the data file containing the time-series data, for example, and the information indicating the acquisition interval of each sensor value is managed.
- the acquisition time of each data can be known from the start time and the number of the data in the time series data.
- the time information is not added for each data point in this way, but may be given indirectly.
- the state information is described as one table in FIG. 3, the format of the state information is not limited to the example shown in FIG.
- the time information and the control information may be created as one table, and the set of the time information 301 and the sensor value 303, which are time series data, may be created as another table. Further, the time series data may be created as a separate table for each sensor type. In this way, the state information may be divided into a plurality of states as long as the correspondence between the information can be performed.
- the time series data may be a summarized summary value instead of the measured value itself measured by the sensor.
- a value that summarizes the data measured by the sensor according to a certain rule may be recorded.
- the term "summary" as used herein means that data with a smaller amount of data than the original data is generated by performing processing using the original data.
- the specific processing content of the summary is not particularly limited, but may be, for example, statistical processing, Fourier transform processing, or the like.
- the sensor acquires the measured value from every second, and the control device of the manufacturing apparatus generates one representative value per hour based on the measured value.
- the representative value may be the average value of the measured values for one hour, the median value of the measured values for one hour, or the mode value of the measured values for one hour. Good. Further, the abnormality detection device 100 may acquire the measured values measured by the sensor, summarize the acquired measured values, and generate time series data.
- the time series data is data every second.
- the value of the command value 1 is not changed.
- the time series data is data every hour.
- the command value 1 is changed from 20 to 40 at 14:00:00 on December 01, 2018, from 40 to 80 at 16:00:00 on December 01, 2018, and 2018. / 12/01 It was changed from 80 to 20 at 17:00:00.
- the command value may be changed depending on the production status and the like.
- data can be extracted according to the command value and the abnormality detection process can be performed using the time series data for each command value so that the tendency of the time series data can be easily predicted.
- the extracted data will be defective. For example, in the example shown in FIG. 4, if the command value 1 value of 20 is extracted, it will be at three time points from 2018/12/01 14:00:00 to 2018/12/01 16:00:00. The corresponding data will be lost.
- FIG. 5 shows an example in which the time series data is missing.
- the data corresponding to the two time points of 2018/12/01 14:00:00 and 2018/12/01 15:00:00 are missing.
- the abnormality detection device 100 may interpolate the missing data by the interpolation process.
- FIG. 6 is a flowchart showing an example of the abnormality detection processing procedure in the abnormality detection device 100.
- the data acquisition unit 101 accepts the selection of time-series data to be processed (step S1). As described above, when the measured values of a plurality of types of sensors are used as time series data, the time series data is generated for each sensor.
- the user receives a selection of which of these time series data is to be processed.
- the data acquisition unit 101 displays information for identifying selectable time-series data, for example, a name indicating a sensor corresponding to the time-series data, on the display 210, and the user selects the displayed name from the displayed names. You may accept the selection.
- the processing condition for example, it is possible to specify whether to perform the processing of extracting the data for each command value as described above.
- the processing condition also determines which command value the data corresponding to which command value is to be processed.
- step S2 the data acquisition unit 101 performs preprocessing according to the processing conditions (step S2).
- the data acquisition unit 101 performs a process of extracting the time-series data of the processing target specified in step S1 from the state information as a preprocessing.
- the data acquisition unit 101 is instructed in step S2 from the time-series data to be processed as preprocessing. Extract the data corresponding to the command value.
- the data acquisition unit 101 may make up for the missing data by the interpolation process as preprocessing.
- the data acquisition unit 101 receives the ratio of the learning section and the test section (step S3).
- the time series data is divided into a learning section and a test section, and the data in the test section is predicted using the time series data in the learning section.
- the data acquisition unit 101 receives input from the user of the ratio of the learning section and the test section used at the time of this division.
- the learning interval and the test interval may be the ratio of the time length corresponding to the data or the ratio of the data points, but here, as described above, the case where the time series data is missing is considered. Then, the ratio of the data points is used.
- the data division unit 102 divides the time series data into a learning section and a test section based on the ratio of the learning section and the test section (step S4). Specifically, the data division unit 102 calculates the division position for dividing the time series data into the learning section and the test section based on the ratio of the learning section and the test section. For example, suppose that the number of data points of the time-series data to be processed is N all , and the ratio of the learning section to the test section is R t : R d for the learning section: test section.
- the data dividing unit 102 among the N all pieces of data, the beginning of N all ⁇ a (R t / (R t + R d)) pieces of data as training interval, the time series data after the learning period Let it be a test section.
- N all ⁇ (R t / (R t + R d )) is not an integer
- learning is performed by rounding, rounding, rounding up, etc. to N all ⁇ (R t / (R t + R d )).
- N all ⁇ (R t / (R t + R d )) is not an integer
- learning is performed by rounding, rounding, rounding up, etc. to N all ⁇ (R t / (R t + R d )).
- n be the data length of the learning section obtained in this way, that is, the number of data points
- m be the data length of the test section.
- n + m N all .
- the division position between the learning section and the test section is between the nth and n + 1th of the time series data.
- the learning section is a section in which the time corresponding to the time series data precedes the test section.
- the number of data points in the learning section and the number of data points in the test section are also hereinafter referred to as learning data length and test data length, respectively.
- the data division unit 102 notifies the subsequence generation unit 103 of the training data length and the test data length.
- the subsequence generation unit 103 generates learning data, which is a subsequence of the learning section, based on the division result of step S4, that is, the division position calculated in step S4 (step S5). That is, the subsequence generation unit 103 generates a subsequence of the learning section by extracting the first n points from the time series data, and extracts the remaining m points of the time series data to generate the subsequence of the test section. Generate.
- the subsequence generation unit 103 outputs the generated subsequence of the learning section to the prediction distribution calculation unit 104.
- the learning section is updated in the process of step S9 later.
- the learning section divided in step S5 is also referred to as an initial learning section.
- the prediction distribution calculation unit 104 obtains the probability distribution and the predicted value at point j of the test section based on the learning data which is a subsequence of the learning section (step S6).
- j is a natural number indicating the number of data in the subsequence in the initial test interval, and the initial value is 1.
- the j-time point indicates a time point corresponding to the j-th data point in the subsequence in the test interval, that is, the j-th time point.
- the prediction distribution calculation unit 104 is a test corresponding to the next data point of the learning data, that is, the n + 1 point from the beginning, based on the learning data which is a subsequence of the initial learning section.
- the prediction distribution calculation unit 104 calculates a conditional distribution at the next point of the training data based on the training data, for example, using a model by Gaussian process regression (GPR: Gaussian Process Regression).
- GPR Gaussian Process Regression
- Y (y 1, y 2, ..., y n)
- p (Y ) the Gaussian distribution.
- C n + 1 in the equation (1) is a covariance matrix of (n + 1) ⁇ (n + 1) and can be expressed in the form shown in the equation (2).
- C n is the covariance matrix of n ⁇ n, can be expressed using a kernel function k (x i, x j) .
- j is n + 1.
- the kernel function is a function that expresses the degree of similarity, that is, the correlation between two variables, x i and x j .
- K is a vector having an element of k (x n , x n + 1 ).
- c is a scalar as shown in the equation (3).
- ⁇ is a constant.
- Gauss kernel shown in equation (4) is used as the kernel function.
- An exponential kernel or a linear kernel may be used, and the kernel function is not limited to the Gauss kernel.
- the prediction distribution calculation unit 104 uses the above equations (1) to (4) to obtain (x 1 , y 1 ), (x 2 , y 2 ), ..., (x n ,) the time series data of the learning interval.
- y n the average value ⁇ of the conditional distribution p (x n + 1
- Y) can be expressed by the equation (7).
- the probability distribution at the time point corresponding to x n + 1 is a Gaussian distribution with a mean value ⁇ and a variance ⁇ 2 .
- FIG. 7 is a diagram showing an example of a Gaussian distribution.
- the predicted value of the time series data at time j can be the average value of the Gaussian distribution.
- the credit interval is, for example, a 95% credit interval
- the range excluding the left and right 2.5% in the Gaussian distribution is the credit interval at time j.
- the 95% credible interval is the interval in which the probability that the true value exists in the credible interval is 95%.
- the prediction distribution calculation unit 104 calculates the probability distribution and then calculates the prediction value, that is, the average value of the Gaussian distribution based on the probability distribution. Further, the prediction distribution calculation unit 104 passes the calculated probability distribution to the credit interval calculation unit 105.
- the credible interval calculation unit 105 calculates the credible interval at time j based on the probability distribution (step S7). The credible interval calculation unit 105 stores the calculated credible interval in the auxiliary storage device 202.
- the credible interval calculation unit 105 determines whether or not the credible intervals of all the points in the test section have been calculated (step S8). When there is a time point in the test section where the credit interval is not calculated (step S8 No), the credit interval calculation unit 105 instructs the subsequence generation unit 103 to learn the learning interval, and the subsequence generation unit 103 determines the learning interval. Update (step S9). Specifically, in step S9, the subsequence generation unit 103 updates the learning section by sliding the learning section backward, that is, by one data point toward the test section side, and updates the subsequence of the updated learning section. It is generated and output to the prediction distribution calculation unit 104.
- Prediction 1 in the second stage of FIG. 8 shows how the predicted value is calculated in step S6 of the first time, that is, the first loop.
- the dark hatched circles indicate the measured values in the learning section
- the light hatched circles indicate the measured values in the test section.
- the measured value is data input as time series data.
- the time-series data may be a summary value or the like instead of the measured value as described above, but since the sensor value is illustrated here, it is described as the measured value.
- the actually measured value in FIG. 8 is a summary value.
- Prediction 1 based on the learning section, that is, the initial learning section, which is the time point 14 points from the left in the time series data, it corresponds to the time point next to the initial learning section, that is, the first time point of the test section, which is indicated by a square mark.
- the predicted value to be calculated is calculated.
- Prediction 2 in the third stage of FIG. 8 shows how the prediction value is calculated in step S6 of the second loop after the learning section is updated in step S9 of the first loop.
- step S9 of the first loop the learning section is updated so as to be slid to the left by one point. That is, the subsequence generation unit 103 updates the learning section so that the corresponding time shifts to a later time, and generates the subsequence corresponding to the updated learning section as the updated learning data. Further, in the updated learning section, the predicted value is used instead of the measured value at the time point when the test section is deviated by one point to the left. That is, in the third stage of FIG.
- the updated learning section includes the actually measured values of 13 points from the second to the 14th from the left in the time series data and one predicted value of the test section.
- the learning interval updated in this way includes the predicted value of the test interval calculated according to the probability distribution.
- the probability distribution of the update point which is the next data point of the updated learning interval, that is, the next time point of the updated learning interval, is calculated by using the subsequence of the updated learning interval.
- the predicted value based on the distribution is calculated.
- the data points next to the initial learning section that is, the test section, indicated by the square marks. The predicted value corresponding to the first data point is calculated.
- step S9 the learning section of step S9 is updated and steps S6 to S8 are carried out until the credit intervals of all the points of the test section are calculated, that is, the m-th prediction m, which is the number of data points of the test section, is executed. Until then, the processes of prediction 3 to prediction m are carried out in the same manner.
- the update of the learning section in step S9 the learning section is sequentially shifted to the left side, and along with this, the predicted value is added one point at a time to the learning section.
- the credible interval calculation unit 105 passes the credible interval data of each point in the test section to the abnormality score calculation unit 106.
- the abnormality degree score calculation unit 106 calculates the abnormality degree score of the test section (step S10).
- the anomaly score is a value indicating the degree of deviation between the training data and the time series data of the test interval. That is, the anomaly degree score is a value indicating the relative degree of divergence between the behavior of the time series data in the learning section and the behavior of the time series data in the test section.
- the anomaly degree score is expressed by a numerical value from 0.0 to 1.0, for example, and the larger the degree of deviation, the closer to 1.0.
- the anomaly degree score becomes low.
- the definition of the anomaly score is not limited to this, and any degree of deviation between the behavior of the time series data in the learning section and the behavior of the time series data in the test section may be expressed.
- the abnormality degree score calculation unit 106 determines at each point whether or not the measured value of the test section is within the credible interval, and the measured value is within the credible interval. It is assumed that a method of calculating the anomaly degree score by dividing the data score by the total data score of the test interval is used. That is, the abnormality degree score calculation unit 106 calculates the abnormality degree score based on the credit interval corresponding to the plurality of data points of the test section and the time series data of the test section.
- the anomaly degree score calculation unit 106 may calculate the anomaly degree score based on the variance of the probability distribution calculated by the prediction distribution calculation unit 104.
- the abnormality detection unit 107 outputs the abnormality determination result according to the abnormality degree score (step S11). For example, the abnormality detection unit 107 determines that the abnormality is normal when the abnormality score is 0.0 or more and less than 0.5, and needs attention when the abnormality score is 0.5 or more and less than 0.7. If the anomaly score is 0.7 or more, it is determined that the abnormality requires a warning. Although caution is also included here as a part of the abnormality, only the abnormality that requires a warning may be defined as the abnormality.
- the abnormality detection unit 107 transmits the abnormality determination result to another device via the network I / F 207 by e-mail, or displays the abnormality determination result on the display 210 via the display I / F 205. If the determination result is an abnormality that requires a warning, the abnormality detection unit 107 may issue an alarm by the alarm output device 206. Further, the abnormality detection unit 107 may treat the transition of the abnormality degree score as time-series data, and display the trend graph on the display 210 via the display I / F 205.
- the abnormality detection unit 107 determines the abnormality using the abnormality degree score, but the abnormality determination method is a method using the calculated credit interval or predicted value, in other words, the probability distribution. Any method may be used to determine an abnormality, and the method is not limited to the above-mentioned example.
- the abnormality detection unit 107 may determine that there is an abnormality if there is even one actually measured value that deviates from the credible interval in the test section. That is, the abnormality detection unit 107 may determine an abnormality based on the probability distribution calculated by the prediction distribution calculation unit 104.
- the subsequence generation unit 103 may generate the subsequence of the learning section of the time series data as the learning data. Then, when the test section has a plurality of points, the subsequence generation unit 103 updates the learning section as described above.
- the abnormality detection unit 107 may display information including the credible interval and the abnormality degree score shown in FIG. 9 on the display 210 via the display I / F 205. Further, data such as a credible interval and an abnormality degree score may be transmitted to an external display via the network I / F 207 and displayed on the external display. By constantly displaying this information on the display 210 or an external display, the operator can confirm the presence or absence of an abnormality and an abnormality sign in real time on a factory line or the like.
- the processing shown in FIG. 6 may be performed for each time series data, or the processing shown in FIG. 6 may be performed for the specific time series data. May be good. Further, when time-series data is extracted for each control condition such as a command value and the process shown in FIG. 6 is performed, the process shown in FIG. 6 may be performed for each command value or specified. The processing shown in FIG. 6 may be carried out with respect to the command value of.
- the above information may be recorded and displayed as a graph on a regular basis.
- it can be dealt with by weighting or the like when calculating the abnormality degree score, so that it is a case where a plurality of types of indicated values are switched according to the production plan with the same device.
- the processing shown in FIG. 6 above can be performed for each command value.
- the abnormality detection method of the present embodiment does not matter the equipment such as a factory, the type of sensor, the tendency of time series data, etc., which are the objects of abnormality detection. Therefore, it is not necessary to evaluate for setting the threshold value for determining the abnormality for each object of abnormality detection, so that the workload for setting the threshold value can be suppressed. Further, in the present embodiment, since the abnormality can be detected based on the tendency of the change such as the gradual change of the time series data and the abnormality in which the tendency suddenly changes, the abnormality can be detected by a simple comparison between the time series data and the threshold value. Compared to the detection method, it is possible to respond to the detection of various abnormalities.
- anomaly detection device 101 data acquisition unit, 102 data division unit, 103 sub-column generation unit, 104 prediction distribution calculation unit, 105 credit section calculation unit, 106 abnormality degree score calculation unit, 107 abnormality detection unit, 201 processor, 202 auxiliary Storage device, 203 memory, 204 input I / F, 205 display I / F, 206 alarm output device, 207 network I / F, 209 input device, 210 display.
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Abstract
Description
図1は、本発明の実施の形態にかかる異常検知装置の機能構成例を示す図である。図1に示すように、本実施の形態の異常検知装置100は、データ取得部101、データ分割部102、部分列生成部103、予測分布算出部104、信用区間算出部105、異常度スコア算出部106および異常検知部107を備える。
Claims (7)
- 時系列データを、学習区間とテスト区間に分割するデータ分割部と、
前記時系列データのうち前記学習区間の部分列を学習データとして生成する部分列生成部と、
前記学習データを用いて、前記テスト区間のデータ点に対応する確率分布を求める予測分布算出部と、
前記確率分布を用いて異常を検知する異常検知部と、
を備えることを特徴とする異常検知装置。 - 前記確率分布に基づいて、前記テスト区間のデータ点に対応する信用区間を算出する信用区間算出部と、
前記信用区間を用いて、前記学習データと前記テスト区間の前記時系列データとの間の外れ度合いを示す異常度スコアを算出する異常度スコア算出部と、
を備え、
前記異常検知部は、前記異常度スコアに基づいて異常を検知することを特徴とする請求項1に記載の異常検知装置。 - 前記学習区間は、前記テスト区間より、前記時系列データに対応する時刻が前となる区間であり、
前記予測分布算出部は、前記確率分布として、前記学習区間の次のデータ点に対応する確率分布を求め、
前記部分列生成部は、前記学習区間を、対応する時刻が後の時刻へずれるように更新し、更新後の学習区間に対応する部分列を更新後の学習データとして生成し、
前記予測分布算出部は、前記更新後の学習データを用いて、前記更新後の学習区間の次のデータ点である更新点の確率分布を求め、
前記信用区間算出部は、前記更新点の確率分布に基づいて、前記更新点の信用区間を算出し、
前記異常度スコア算出部は、前記テスト区間の複数のデータ点に対応する前記信用区間
と、前記テスト区間の前記時系列データとに基づいて前記異常度スコアを算出することを特徴とする請求項2に記載の異常検知装置。 - 前記更新後の学習区間は、前記確率分布に応じて算出される前記テスト区間の予測値を含むことを特徴とする請求項3に記載の異常検知装置。
- 異常度スコア算出部は、前記テスト区間の前記時系列データのうち、対応する前記信用区間内に存在しないデータの点数に基づいて、前記異常度スコアを算出することを特徴とする請求項3または4に記載の異常検知装置。
- 前記異常度スコア算出部は、前記予測分布算出部で算出された確率分布の分散に基づいて、前記異常度スコアを算出することを特徴とする請求項2から5のいずれか1つに記載の異常検知装置。
- 異常検知装置における異常検出方法であって、
時系列データを、学習区間とテスト区間に分割する第1のステップと、
前記時系列データのうち前記学習区間の部分列を学習データとして生成する第2のステップと、
前記学習データを用いて、前記テスト区間のデータ点に対応する確率分布を求める第3のステップと、
前記確率分布を用いて異常を検知する第4のステップと、
を含むことを特徴とする異常検知方法。
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