JP2019168412A - Abnormality detector and abnormality detection method - Google Patents

Abstract

To provide an abnormality detector with which it is possible to detect the abnormality of a ball screw with good accuracy.SOLUTION: An abnormality detector 1 comprises a generation unit 10 and a determination unit 14. The generation unit 10 executes an envelope process and a time- and amplitude-domain normalization process on vibration data measured by a vibration sensor 4 in a period when a ball screw 20 is continuously operated, thereby generating waveform data that indicates a time change of vibration. The determination unit 14 calculates the degree of deviation of a determination object waveform indicated by determination object waveform data generated when determining whether or not there is abnormality of a target device 2 to a reference waveform indicated by reference waveform data generated when the target device 2 is normal. The determination unit 14 determines whether or not there is abnormality of the target device 2 on the basis of the degree of deviation.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an abnormality detection device and an abnormality detection method for a target device including a ball screw.

  2. Description of the Related Art Conventionally, a method for detecting an abnormality in a rotating machine by analyzing vibration data obtained from a vibration sensor attached to the rotating machine is known. For example, Japanese Patent Laying-Open No. 2006-133162 (Patent Document 1) uses a tendency that the magnitude of vibration (vibration level) increases as an abnormality (for example, damage) generated in a rolling bearing progresses. A method for detecting an abnormality in the above is disclosed. Japanese Patent Laid-Open No. 2013-257253 (Patent Document 2) discloses a ball screw by filtering vibration data of an abnormal detection frequency of a ball screw from vibration data measured by a vibration sensor attached to a target device including the ball screw. A method for detecting an abnormality in the above is disclosed.

JP 2006-133162 A JP 2013-257253 A

  The vibration data measured by the vibration sensor attached to the target device including the ball screw includes data on the natural vibration of the nut included in the ball screw. Due to the natural vibration of the nut, the vibration data above a certain frequency hardly changes depending on whether there is an abnormality. Therefore, when the frequency band resulting from the abnormality of the ball screw and the frequency band due to the natural vibration of the nut overlap, the abnormality detection method based on the frequency analysis described in JP2013-257253A accurately detects the abnormality of the ball screw. Can not do it.

  Furthermore, the vibration generated in the ball screw depends on environmental conditions such as load and temperature applied to the ball screw. That is, the vibration level changes according to environmental conditions. For this reason, the ball screw abnormality cannot be detected with high accuracy simply by applying the technique described in Japanese Patent Application Laid-Open No. 2006-133162 to the ball screw abnormality detection method.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an abnormality detection device and an abnormality detection method capable of accurately detecting an abnormality of a ball screw.

  The abnormality detection device of the present disclosure determines whether there is an abnormality in the target device by using a vibration sensor installed in the target device including the ball screw. The abnormality detection device includes a generation unit and a determination unit. The generator generates waveform data indicating temporal changes in vibration by performing envelope processing and time domain and amplitude domain normalization processing on the vibration data measured by the vibration sensor during a period in which the ball screw is continuously operated. Is generated. The determination unit is indicated by the determination target waveform data generated by the generation unit when determining whether the target device is abnormal with respect to the waveform indicated by the reference waveform data generated by the generation unit when the target device is normal. The degree of divergence of the waveform to be calculated is calculated. The determination unit determines whether an abnormality has occurred in the target device based on the degree of deviation.

  Preferably, the target device includes a ball screw shaft, a nut screwed to the ball screw shaft, a fixed support unit that rotatably supports one end of the ball screw shaft, and the other end of the ball screw shaft. And a support side support unit. The vibration sensor is installed in at least one of the nut, the fixed side support unit, and the support side support unit.

  Preferably, the generation unit performs low-pass filter processing on the vibration data subjected to envelope processing before performing normalization processing.

  Preferably, the determination unit has an abnormality in the target device when the degree of deviation exceeds the first threshold value and the effective value of the vibration data before performing the normalization process exceeds the second threshold value. Is determined.

  Preferably, the generation unit generates a plurality of reference candidate waveform data when the target device is normal. The plurality of reference candidate waveform data is generated in a state where the operation conditions of the target device are different from each other. The determination unit selects one of the plurality of reference candidate waveform data as reference waveform data in accordance with the operating condition of the target device when determining whether there is an abnormality.

  Preferably, the determination unit calculates an integrated value of a difference between the waveform indicated by the reference waveform data and the waveform indicated by the determination target waveform data as the degree of divergence.

  Preferably, the ball screw has a ball screw shaft and a nut screwed to the ball screw shaft. The determination unit specifies a portion different from the waveform indicated by the reference waveform data from the waveforms indicated by the determination target waveform data, and based on the position of the nut when the vibration sensor measures the vibration corresponding to the specified portion. The position where the abnormality in the ball screw has occurred is estimated.

  An abnormality detection method according to another aspect of the present disclosure uses a vibration sensor installed in a target device including a ball screw to determine whether there is an abnormality in the target device. The abnormality detection method includes the following two steps. The first step is to perform an envelope process and a time domain and amplitude domain normalization process on the vibration data measured by the vibration sensor during a period in which the ball screw is continuously operated, thereby changing the time change of the vibration. This is a step of generating the waveform data shown. In the second step, the waveform indicated by the determination target waveform data generated when determining whether there is an abnormality in the target device with respect to the waveform indicated by the reference waveform data generated when the target device is normal. This is a step of calculating a divergence degree and determining whether or not an abnormality has occurred in the target device based on the divergence degree.

  According to the abnormality detection device and the abnormality detection method of the present disclosure, it is possible to accurately detect abnormality of the ball screw.

It is a figure which shows the abnormality detection system which concerns on Embodiment 1. FIG. It is a flowchart which shows the flow of a production | generation process of reference | standard waveform data. It is a flowchart which shows the flow of a detection process of abnormality of a target apparatus. It is a figure which shows an example of reference | standard waveform data and determination object waveform data. It is a figure which shows another example of reference | standard waveform data and determination object waveform data. It is a figure which shows the correspondence of the effective value of acceleration, the deviation degree, and the determination result in the abnormality detection apparatus which concerns on Embodiment 2. FIG. It is a figure which shows an example of the image shown by the normal waveform data which the production | generation part of the modification 2 produced | generated. It is a figure which shows an example of the image shown by the determination object waveform data which the production | generation part of the modification 2 produced | generated.

  Embodiments of the present invention will be described below with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated. Further, the embodiments and modifications described below may be combined appropriately and selectively.

[Embodiment 1]
(Ball screw abnormality detection system)
FIG. 1 is a diagram showing an abnormality detection system according to Embodiment 1 of the present invention. The abnormality detection system according to Embodiment 1 includes an abnormality detection device 1, a target device 2, a controller 3, and a vibration sensor 4.

  The target device 2 is a device that is a target of abnormality detection by the abnormality detection device 1. The target device 2 includes a ball screw 20, a fixed side support unit 23, a support side support unit 24, and a motor 25 that rotates the ball screw shaft 21.

  The ball screw 20 includes a ball screw shaft 21 and a nut 22 screwed onto the ball screw shaft 21 via a plurality of balls (not shown).

  The fixed-side support unit 23 is a fixed-side bearing that rotatably supports one end of the ball screw shaft 21 and fixes the position of the ball screw shaft 21 in the axial direction. The fixed support unit 23 is, for example, a thrust angular ball bearing. The support side support unit 24 is a support side bearing that supports the other end of the ball screw shaft 21 so as to be rotatable and movable in the axial direction. The support side support unit 24 is, for example, a deep groove ball bearing.

  The controller 3 generates a timing signal for applying a current to the motor 25 in order to move the nut 22 from the current position to the specified position based on a command from the host control unit, and supplies a current to the motor 25 according to the generated timing signal. Apply. Specifically, the controller 3 applies a current to the motor 25 when the timing signal is active. The controller 3 generates a timing signal that is active for a time corresponding to the distance from the current position of the nut 22 to the designated position and the moving speed of the nut 22. Each time the controller 3 generates a timing signal, it outputs the generated timing signal to the abnormality detection device 1.

  The controller 3 may change the value of the current flowing through the motor 25 based on a command from the upper control unit. As the current flowing through the motor 25 changes, the moving speed of the nut 22 changes.

  The vibration sensor 4 is installed in the housing of the fixed support unit 23 and measures vibration. The vibration sensor 4 measures acceleration indicating the magnitude of vibration as vibration data, and outputs the measured vibration data to the abnormality detection device 1.

  The abnormality detection device 1 detects an abnormality of the target device 2 based on the vibration data measured by the vibration sensor 4. The abnormality detection device 1 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). These parts are connected to each other via an internal bus. The CPU executes the program stored in the ROM by expanding it in the RAM or the like. The program stored in the ROM is a program that describes the processing method of the abnormality detection device 1. The abnormality detection device 1 includes a generation unit 10, a storage unit 13, and a determination unit 14. The generation unit 10 and the determination unit 14 are configured by a CPU. The storage unit 13 is configured by a ROM or a RAM.

  The generation unit 10 generates waveform data indicating a temporal change in vibration (acceleration) measured by the vibration sensor 4 from the start to the end of a period in which the ball screw 20 is continuously operated. The generation unit 10 includes a data acquisition unit 11 and a data processing unit 12. The waveform data is data in CSV (Comma Separated Values) format in which the elapsed time from the start of the period in which the ball screw 20 is continuously operated and the acceleration are associated with each other.

  The data acquisition unit 11 acquires vibration data measured by the vibration sensor 4 from the start time to the end time of the period for each period in which the timing signal received from the controller 3 is continuously active.

  The data processing unit 12 performs the above-described envelope processing (envelope processing), low-pass filter processing, and time domain and amplitude domain normalization processing on the vibration data acquired by the data acquisition unit 11. Generate waveform data.

  The storage unit 13 stores the reference waveform data generated by the generation unit 10 when the target device 2 is normal.

  The determination unit 14 calculates the degree of divergence of the determination target waveform indicated by the determination target waveform data generated by the generation unit 10 when determining whether or not the target device 2 is abnormal with respect to the reference waveform indicated by the reference waveform data. . The determination unit 14 determines that an abnormality has occurred in the target device 2 when the calculated degree of divergence exceeds a predetermined first threshold value Th1. The determination unit 14 outputs a determination result. For example, the determination unit 14 displays the determination result on a display device (not shown).

(Generation processing of fundamental waveform data)
The flow of the reference waveform data generation process will be described with reference to FIG. FIG. 2 is a flowchart showing a flow of processing for generating reference waveform data.

  First, in step S <b> 1, the data acquisition unit 11 acquires vibration data from the vibration sensor 4 during a period in which the timing signal is continuously active when the target device 2 is normal. The vibration data is data in CSV format in which the elapsed time from the start of the period in which the timing signal is continuously active is associated with the acceleration measured by the vibration sensor 4.

  Next, in step S2, the data processing unit 12 generates envelope waveform data by executing envelope processing on the vibration data. Envelope processing is processing that inverts the negative portion of the waveform indicated by the vibration data positively to form an envelope, and is processing that extracts the outer shape of the amplitude of the waveform indicated by the vibration data.

  Next, in step S3, the data processing unit 12 executes low-pass filter processing for removing high-frequency components from the envelope waveform data using a low-pass filter. As a result, the noise component included in the envelope waveform data and the vibration change in the minute section are removed. As a result, the envelope waveform indicated by the envelope waveform data is smoothed.

  Next, in step S4, the data processing unit 12 normalizes the envelope waveform data subjected to the filter process in the time domain. Specifically, the data processing unit 12 divides the elapsed time from the start of the period in which the timing signal is continuously active by the time length of the period.

  Next, in step S5, the data processing unit 12 normalizes the envelope waveform data normalized in the time domain in the amplitude domain. Specifically, the data processing unit 12 divides the acceleration indicated by the envelope waveform data normalized in the time domain by the maximum value of the acceleration indicated by the envelope waveform data.

  In step S6, the data processing unit 12 stores the data obtained in step S5 in the storage unit 13 as reference waveform data.

  The reference waveform data generation process (steps S1 to S6) is executed in advance before performing the process of determining whether the target device 2 is abnormal. For example, it is executed at the timing when the target device 2 is newly installed or when the target device 2 is maintained.

  The generation unit 10 may generate a plurality of normalized waveform data by executing Steps S1 to S6 a plurality of times when the target device 2 is normal, and use the average data as reference waveform data. .

(Detection process for target device abnormality)
With reference to FIG. 3, the flow of the abnormality detection process of the target apparatus 2 will be described. FIG. 3 is a flowchart showing a flow of an abnormality detection process for the target device 2.

  First, in step S <b> 11, the data acquisition unit 11 acquires vibration data from the vibration sensor 4 during a period in which the timing signal is continuously active when determining whether there is an abnormality in the target device 2. The data processing unit 12 sequentially performs envelope processing (step S12), low-pass filter processing (step S13), time domain normalization processing (step S14), and amplitude domain normalization processing (step S15) on the vibration data. Execute to generate judgment target waveform data. Steps S12 to S15 are the same as steps S2 to S5 described above. Therefore, detailed description of the processing of steps S12 to S15 is omitted.

  Next, in step S <b> 16, the determination unit 14 calculates the degree of divergence of the determination target waveform indicated by the determination target waveform data obtained in step S <b> 15 with respect to the reference waveform indicated by the reference waveform data stored in the storage unit 13. . The determination unit 14 calculates an integral value of a difference between the reference waveform data and the determination target waveform data as a deviation degree.

  Next, in step S <b> 17, the determination unit 14 determines whether there is an abnormality in the target device 2 by comparing the calculated degree of divergence with the first threshold value Th <b> 1. Specifically, the determination unit 14 determines that an abnormality has occurred in the target device 2 when the degree of deviation exceeds the first threshold value Th1, and when the degree of deviation is equal to or less than the first threshold value Th1. It is determined that the target device 2 is normal.

(Example of detection processing)
FIG. 4 is a diagram illustrating an example of the reference waveform data and the determination target waveform data. On the left side of FIG. 4, reference waveform data Wc1 generated by the generation unit 10 when the target apparatus 2 is normal without being damaged is shown. The right side of FIG. 4 shows determination target waveform data Wc2 generated by the generation unit 10 when the target device 2 is damaged.

  The data processing unit 12 generates smoothed envelope waveform data Wb1 by performing envelope processing and low-pass filter processing on the vibration data Wa1 acquired by the data acquisition unit 11 when the target device 2 is normal. The data processing unit 12 generates the reference waveform data Wc1 by performing normalization processing of the time domain and the amplitude domain on the envelope waveform data Wb1.

  Similarly, the data processing unit 12 performs envelope processing and low-pass filter processing on the vibration data Wa2 acquired by the data acquisition unit 11 when diagnosing the target device 2, thereby generating smooth envelope waveform data Wb2. To do. The data processing unit 12 generates determination target waveform data Wc2 by performing time domain and amplitude domain normalization processing on the envelope waveform data Wb2.

  The vibration data output from the vibration sensor 4 slightly changes according to the environmental conditions (load, temperature, lubrication state, etc.) of the ball screw. However, by performing the low pass filter process and the normalization process, the reference waveform data Wc1 and the determination target waveform data Wc2 contain almost no component of slight change according to such an operating environment. However, each waveform indicated by the data when the target device 2 is damaged has a portion P different from the waveform indicated by the data when the target device 2 is normal. The size of the portion P is proportional to the size of damage of the target device 2. Therefore, the determination unit 14 calculates the area of the difference region D1 (the integrated value of the difference) between the reference waveform data Wc1 and the determination target waveform data Wc2 as a deviation degree, and compares the deviation degree with the first threshold value Th1. Thus, it is possible to determine whether the target device 2 is abnormal.

  FIG. 5 is a diagram illustrating another example of the reference waveform data and the determination target waveform data. FIG. 5 shows data when the rotational speed of the ball screw shaft 21 is slower than when the data shown in FIG. 4 is generated and the active period of the timing signal is long. On the left side of FIG. 5, vibration data Wa3, smoothed envelope waveform data Wb3, and reference waveform data Wc3 when the target apparatus 2 is normal without being damaged are shown. The right side of FIG. 5 shows vibration data Wa4 when the target device 2 is damaged, smoothed envelope waveform data Wb4, and determination target waveform data Wc4.

  Also in FIG. 5, each waveform indicated by the data when the target device 2 is damaged has a portion P different from the waveform indicated by the data when the target device 2 is normal. Therefore, the determination unit 14 calculates the area of the difference region D2 (difference integrated value) between the reference waveform data Wc3 and the determination target waveform data Wc4 as a deviation degree, and compares the deviation degree with the first threshold value Th1. Thus, it is possible to determine whether the target device 2 is abnormal.

  As shown in FIG. 4 and FIG. 5, even if the length of the active period of the timing signal is different, the reference waveform data Wc1 and Wc3 are obtained by normalizing the envelope waveform data in the time domain and the amplitude domain. The waveform shown has a similar shape. Therefore, data obtained by averaging the reference waveform data Wc1 and Wc3 may be used as common reference waveform data. Thereby, the determination unit 14 calculates the divergence degree of the determination target waveform data with respect to the common reference waveform data even when the length of the period in which the ball screw 20 is operated (active period of the timing signal) is different. The presence / absence of abnormality can be determined based on the degree of deviation.

(advantage)
As described above, the abnormality detection device 1 includes the generation unit 10 and the determination unit 14. The generation unit 10 performs an envelope process and a time domain and amplitude domain normalization process on the vibration data measured by the vibration sensor 4 during a period in which the ball screw 20 is continuously operated, thereby changing the time change of the vibration. The waveform data shown is generated. The determination unit 14 determines the determination target waveform data generated when determining whether or not the target device 2 is abnormal with respect to the reference waveform indicated by the reference waveform data generated when the target device 2 is normal. The degree of deviation of the target waveform is calculated. The determination unit 14 determines whether an abnormality has occurred in the target device 2 based on the degree of deviation.

  According to the above configuration, waveform data is generated by performing envelope processing on vibration data. The waveform shown by the waveform data indicates a time change of the amplitude of the vibration data. If any abnormality occurs in the target device 2, the amplitude of the vibration data is changed due to the abnormality. In particular, since the ball screw has a moving nut, the amplitude is changed depending on the position of the nut. That is, when the nut is located at a location where an abnormality has occurred, the change in amplitude becomes large. Therefore, the waveform shown by the waveform data when the target device 2 is abnormal partially changes from the waveform shown by the waveform data when the target device 2 is normal. Therefore, the abnormality of the target device 2 can be accurately detected based on the degree of deviation of the determination target waveform from the reference waveform. Also, a partial abnormality of the ball screw 20 can be detected stably.

  In the technique described in Japanese Patent Application Laid-Open No. 2006-133162, since vibration data is subjected to frequency analysis, it is necessary to consider the influence of the frequency band of the natural vibration of the nut. However, according to the above configuration, since the presence / absence of abnormality is determined based on the waveform data indicating the time variation of the amplitude, there is no limitation due to the natural vibration of the nut. Therefore, the abnormality of the target device 2 can be detected with high accuracy.

  Furthermore, waveform data is generated by performing normalization processing of the time domain and the amplitude domain on the vibration data. Thereby, the influence on the vibration by the fluctuation | variation of the environmental conditions (a load, temperature, a lubrication state, etc.) of the object apparatus 2 can be suppressed. As a result, the abnormality of the target device 2 can be detected with high accuracy.

  The generation unit 10 performs low-pass filter processing on the vibration data subjected to envelope processing before performing normalization processing. As a result, it is possible to remove the noise component included in the vibration data subjected to the envelope processing and the vibration change in the minute section.

  The determination unit 14 calculates an integrated value of the difference between the reference waveform indicated by the reference waveform data and the determination target waveform indicated by the determination target waveform data as the degree of divergence. Thereby, the divergence degree can be easily calculated.

[Embodiment 2]
In said Embodiment 1, the determination part 14 determined the presence or absence of abnormality of the target apparatus 2 based only on the deviation degree. On the other hand, the determination unit 14 of the abnormality detection device 1 according to the second embodiment is based on the effective value of the vibration (acceleration) indicated by the envelope waveform data subjected to the low-pass filter processing and the above divergence degree. The presence or absence of an abnormality in the device 2 is determined.

  FIG. 6 is a diagram illustrating a correspondence relationship between effective values and deviations of acceleration and determination results in the abnormality detection device according to the second embodiment.

  The effective value of acceleration indicated by the envelope waveform data subjected to the low-pass filter processing represents the magnitude of vibration (vibration level). When the effective value of acceleration is sufficiently small, the possibility that an abnormality has occurred in the target device 2 is low. Therefore, as shown in FIG. 6, the determination unit 14 determines that the effective value of the acceleration in the envelope waveform data before the normalization process is greater than the first threshold value Th1 and the second threshold value. When it exceeds Th2, it is determined that an abnormality has occurred in the target device 2.

  On the contrary, when the effective value of the acceleration in the envelope waveform data subjected to the low-pass filter processing is sufficiently large, there is a high possibility that some abnormality has occurred in the target device 2. Therefore, as illustrated in FIG. 6, the determination unit 14 determines whether the effective value of the acceleration in the envelope waveform data subjected to the low-pass filter exceeds the third threshold value Th3 regardless of the value of the divergence degree. 2 is determined to be abnormal. The third threshold value Th3 is larger than the second threshold value Th2.

  As described above, according to the abnormality detection device 1 according to the second embodiment, the determination unit 14 determines that the divergence exceeds the first threshold Th1 and the effective value of the envelope waveform data is the second threshold Th2. It is determined that an abnormality has occurred in the target device 2 when the number exceeds. Thereby, the presence or absence of abnormality of the target device 2 can be determined with higher accuracy.

[Embodiment 3]
The abnormality detection device 1 according to Embodiment 3 stores a plurality of reference candidate waveform data in advance, and among the plurality of reference candidate waveform data according to the operating conditions of the target device 2 when determining the presence or absence of abnormality. Is selected as reference waveform data.

  As shown in FIGS. 4 and 5, when the difference in the period for operating the ball screw 20 is small, the reference waveform data generated in each period is similar. However, when the operating conditions of the target device 2 (such as the moving distance and moving speed of the nut 22) are greatly different, the waveform data also changes. For example, when the target device 2 is applied as a part of a production line, the operating conditions of the target device 2 may vary greatly depending on the model of the product to be manufactured. Hereinafter, a case where the target device 2 is applied to a production line will be described as an example.

  In the abnormality determination system according to the third embodiment, the controller 3 determines the operating condition of the target device 2 in accordance with the product type instructed by the host control unit, and drives the motor 25 according to the determined operating condition. . The controller 3 outputs model information indicating the model of the product instructed from the control unit to the abnormality detection device 1.

  The generation unit 10 generates a plurality of reference candidate waveform data when the target apparatus 2 is normal, and stores the generated plurality of reference candidate waveform data in the storage unit 13. The plurality of reference candidate waveform data is generated in a state where the operation conditions of the ball screw 20 are different from each other. The generation unit 10 stores each reference candidate waveform data in the storage unit 13 in association with the model information received from the controller 3. The model information is information that indirectly indicates the operating conditions of the target device 2.

  The determination unit 14 selects one reference candidate waveform data corresponding to the type information received from the controller 3 from among a plurality of reference candidate waveform data stored in the storage unit 13. The determination unit 14 uses the selected reference candidate waveform data as reference waveform data, calculates the divergence degree of the determination target waveform data with respect to the reference waveform data, and determines the target device 2 according to the comparison result between the divergence degree and the first threshold value Th1. Determine whether there is any abnormality.

  According to said structure, the reference waveform data suitable for driving | running conditions can be used, and abnormality of the target apparatus 2 can be detected more accurately.

[Embodiment 4]
In addition to the above processing, the determination unit 14 of the abnormality detection device 1 according to Embodiment 4 estimates a position where an abnormality has occurred in the ball screw 20 based on the difference between the reference waveform and the determination target waveform.

  As shown in FIGS. 4 and 5, the determination target waveform data Wc2 and Wc4 may have portions P different from the reference waveform data Wc1 and Wc3, respectively. In this case, when the vibration corresponding to the portion P is measured, there is a high possibility that the portion of the ball screw shaft 21 screwed with the nut 22 is damaged. Therefore, the abnormality detection device 1 according to the fourth embodiment performs the following processing.

  The abnormality detection device 1 acquires a position signal indicating the current position of the nut 22 from the controller 3 together with the timing signal. For example, the target device 2 includes a position sensor (not shown) that detects whether or not the nut 22 is located at the reference position. The controller 3 may generate a position signal based on the number of rotations of the ball screw shaft 21 after the position sensor detects that the nut 22 is positioned at the reference position.

  The determination unit 14 specifies the time at which the vibration of a portion different from the reference waveform indicated by the reference waveform data is measured from the determination target waveforms indicated by the determination target waveform data. For example, the determination unit 14 specifies the time when the portion where the difference between the reference waveform data and the determination target waveform data is maximized is measured. The determination unit 14 estimates the position of the nut 22 indicated by the position signal received at the specified time as a position where an abnormality has occurred in the ball screw 20. The determination unit 14 outputs an estimation result. For example, the determination unit 14 displays the estimation result on a display device (not shown).

  According to the fourth embodiment, the user can easily grasp the location where the abnormality of the ball screw 20 occurs.

(Modification 1)
In the above-described first to fourth embodiments, the determination unit 14 calculates the integrated value of the difference between the reference waveform data and the determination target waveform data as the degree of divergence. However, the determination unit 14 may calculate the divergence degree by another method. For example, the determination unit 14 may calculate a correlation coefficient σ between the reference waveform data and the determination target waveform data, and set 1−σ as the degree of divergence.

(Modification 2)
In the above-described first to fourth embodiments, the determination unit 14 calculates an integrated value of a difference between the CSV format reference waveform data and the CSV format determination target waveform data as a divergence degree. However, the generation unit 10 may generate the reference waveform data and the determination target waveform data as N × M pixel image data.

  In step S4 shown in FIG. 2 and step S14 shown in FIG. 3, the data processing unit 12 divides the envelope waveform data subjected to the low-pass filter processing into a predetermined number N (for example, 256) sections in a certain time unit. A certain time unit is a time obtained by dividing a period in which the timing signal is continuously active by a predetermined number N. The data processing unit 12 calculates an average value of acceleration indicated by the envelope waveform data for each section.

  Further, in step S5 shown in FIG. 2 and step S15 shown in FIG. 3, the data processing unit 12 sets the acceleration indicated by the envelope waveform data normalized in the time domain to the maximum value of the acceleration indicated by the envelope waveform data. Divide by. Thereafter, the data processing unit 12 multiplies all the accelerations by M (M is 256, for example) and rounds them to an integer value. Thereby, the data processing unit 12 generates data in which each of the N sections is associated with the normalized acceleration.

  Next, the data processing unit 12 generates N × M pixel image data as waveform data as follows. That is, when the acceleration corresponding to the n-th section is m, the data processing unit 12 sets the pixel value of coordinates (n, 1) to coordinates (n, m) to 1, and coordinates (n, m + 1) to coordinates The pixel value of (n, M) is set to 0. The nth section is a section close to the nth at the start of a period in which the timing signal is continuously active.

  FIG. 7 is a diagram illustrating an example of an image represented by normal waveform data generated by the generation unit 10 according to the second modification. FIG. 8 is a diagram illustrating an example of an image indicated by the determination target waveform data generated by the generation unit 10 according to the second modification. In FIG. 7 and FIG. 8, the hatched portion indicates a region where the pixel value is 1. As shown in FIGS. 7 and 8, by using waveform data as image data, the difference between the normal waveform indicated by the normal waveform data and the determination target waveform indicated by the determination target waveform data can be easily confirmed visually. can do.

  The determination unit 14 calculates the area of the portion of the first image indicated by the determination target waveform data that does not overlap the second image indicated by the normal waveform data as the degree of divergence. Alternatively, the determination unit 14 calculates the total value of the first area of the portion of the first image that does not overlap the second image and the second area of the portion of the second image that does not overlap the first image as the degree of divergence. May be.

(Modification 3)
In the first to fourth embodiments described above, the vibration sensor 4 is installed on the fixed support unit 23. However, the vibration sensor 4 may be installed on the support side support unit 24 or the nut 22. However, when the vibration sensor 4 is installed on the nut 22, the vibration sensor 4 may be detached from the nut 22 due to the movement of the nut 22. Therefore, the vibration sensor 4 is preferably installed on the stationary support unit 23 or the support side support unit 24 that is stationary.

  Alternatively, the vibration sensor 4 may be installed in each of the fixed-side support unit 23, the support-side support unit 24, and the nut 22, and the abnormality of the target device 2 may be detected based on the vibration data from each vibration sensor 4. Thereby, it becomes easy to specify which part of the fixed side support unit 23, the support side support unit 24, and the nut 22 is abnormal. For example, when bearing damage has occurred in the fixed side support unit 23, the vibration level of the vibration sensor 4 installed in the fixed side support unit 23 is higher than the vibration level of the other vibration sensors 4. It can be identified that an abnormality has occurred in the support unit 23.

(Modification 4)
In the above-described first to fourth embodiments, the controller 3 outputs the generated timing signal to the abnormality detection device 1 every time a timing signal for operating the target device 2 is generated. However, the controller 3 may output only a timing signal for operating the target device 2 in a specific operation pattern to the abnormality detection device 1. The specific operation pattern is preferably a pattern in which the nut 22 is moved at a constant speed from the end on the fixed support unit 23 side to the end on the support side support unit 24 side. Thereby, the partial abnormality of the ball screw shaft 21 can be detected with high accuracy.

  For example, the controller 3 may operate the target device 2 in accordance with a timing signal for operating in a specific operation pattern when the target device 2 is activated, and output the timing signal to the abnormality detection device 1.

(Modification 5)
A program for causing the abnormality detection apparatus 1 to execute the above-described operation may be provided. Such a program is recorded on a computer-readable recording medium such as a flexible disk attached to the computer, a CD-ROM (Compact Disk-Read Only Memory), a ROM, a RAM, and a memory card, and provided as a program product. You can also. Alternatively, the program can be provided by being recorded on a recording medium such as a hard disk built in the computer. A program can also be provided by downloading via a network.

  The provided program product is installed in a program storage unit such as a hard disk and executed. The program product includes the program itself and a recording medium on which the program is recorded.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiment but by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

DESCRIPTION OF SYMBOLS 1 Abnormality detection apparatus, 2 Target apparatus, 3 Controller, 4 Vibration sensor, 10 Generation part 11 Data acquisition part, 12 Data processing part, 13 Storage part, 14 Judgment part, 20 Ball screw, 21 Ball screw shaft, 22 Nut, 23 Fixed side support unit, 24 Support side support unit, 25 Motor.

Claims (8)

Using a vibration sensor installed in a target device including a ball screw, an abnormality detection device that determines whether there is an abnormality in the target device,
Generates waveform data indicating the time change of vibration by performing envelope processing and normalization processing of the time domain and amplitude domain on the vibration data measured by the vibration sensor during the period of continuous operation of the ball screw A generator to
Indicated by the determination target waveform data generated by the generation unit when determining whether or not the target device is abnormal with respect to the waveform indicated by the reference waveform data generated by the generation unit when the target device is normal An abnormality detection apparatus comprising: a determination unit that calculates a divergence degree of a waveform to be determined and determines whether or not an abnormality has occurred in the target apparatus based on the divergence degree. The target device includes a ball screw shaft, a nut screwed to the ball screw shaft, a stationary support unit that rotatably supports one end of the ball screw shaft, and the other end of the ball screw shaft. A support side support unit that supports it,
The abnormality detection device according to claim 1, wherein the vibration sensor is installed in at least one of the nut, the fixed support unit, and the support support unit.   The abnormality detection device according to claim 1, wherein the generation unit performs low-pass filter processing on the vibration data subjected to the envelope processing before performing the normalization processing.   The determination unit causes an abnormality in the target device when the degree of divergence exceeds a first threshold value and an effective value of the vibration data before the normalization process exceeds a second threshold value. The abnormality detection device according to claim 1, wherein the abnormality detection device determines that the error has occurred. The generation unit generates a plurality of reference candidate waveform data when the target device is normal,
The plurality of reference candidate waveform data is generated in a state in which operating conditions of the target device are different from each other,
2. The determination unit according to claim 1, wherein the determination unit selects one of the plurality of reference candidate waveform data as the reference waveform data in accordance with an operation condition of the target device when determining whether there is an abnormality. Anomaly detection device.   The abnormality detection device according to claim 1, wherein the determination unit calculates an integrated value of a difference between a waveform indicated by the reference waveform data and a waveform indicated by the determination target waveform data as the divergence degree. The ball screw has a ball screw shaft and a nut screwed to the ball screw shaft,
The determination unit specifies a portion different from the waveform indicated by the reference waveform data from among the waveforms indicated by the determination target waveform data, and the nut when the vibration sensor measures vibration corresponding to the specified portion The abnormality detection device according to claim 1, wherein a position where an abnormality has occurred in the ball screw is estimated based on the position of. An abnormality detection method for determining presence or absence of abnormality of the target device using a vibration sensor installed in the target device including a ball screw,
Generates waveform data indicating the time change of vibration by performing envelope processing and normalization processing of the time domain and amplitude domain on the vibration data measured by the vibration sensor during the period of continuous operation of the ball screw And steps to
The degree of divergence of the waveform indicated by the determination target waveform data generated when determining whether or not the target device is abnormal is calculated with respect to the waveform indicated by the reference waveform data generated when the target device is normal. And determining whether or not an abnormality has occurred in the target device based on the degree of divergence.

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