State monitoring method for mechanical device, state monitoring device, and program

Abstract

This state monitoring method for a mechanical device that performs a rotation operation comprises an acquisition step for acquiring rotation speed data and vibration data during a rotation operation of the mechanical device, a conversion step for converting the vibration data from a time domain to an angle domain by using the acquired rotation speed data and the vibration data, a re-conversion step for reconverting the converted vibration data into a time domain based on a predetermined reference speed, and a diagnosis step for diagnosing a state of the mechanical device by using the converted vibration data. In the conversion step, when a section where a rotation speed is zero or approximately equal to zero is included in the rotation speed data, the rotation speed data is corrected so that the rotation speed is varied in the section, and then the vibration data is converted into an angle domain.

Description

Mechanical device status monitoring method, status monitoring device, and program

[0001] The present invention relates to a method, a device, and a program for monitoring the status of a machine.

[0002] Conventionally, the condition of various components constituting a mechanical device has been monitored to ensure proper operation of the device. For example, the mechanical device is equipped with bearings for rotational operation. To diagnose the condition of the bearings, there is a method of acquiring vibration information during operation and analyzing the vibration information.

[0003] For example, Patent Document 1 discloses a method of taking into consideration changes in the rotational speed of a bearing, applying an order tracking method to detect a desired frequency spectrum from vibration information, and using the frequency spectrum for abnormality diagnosis.

[0004] Japanese Patent Application Publication No. 2023-75685

[0005] As disclosed in Patent Document 1, by using the order tracking method, it is possible to identify the desired frequency spectrum even when there is a change in the rotational speed of the bearing. However, there are cases where the rotational speed of the bearing temporarily becomes zero or close to zero during rotation. In such a state, the method described in Patent Document 1 cannot capture the characteristics of the vibration information. Therefore, the method described in Patent Document 1 cannot be used as is for bearings in which such a state may occur.

[0006] In view of the above problems, the present invention aims to accurately monitor the state of a mechanical device even when a change in rotation speed occurs, including a stoppage of rotation, in an environment in which the rotation speed of the mechanical device during rotation operation may change intermittently.

[0007] In order to solve the above problems, the present invention has the following configuration: That is, a condition monitoring method for a mechanical device that performs a rotational operation includes: an acquisition step of acquiring rotational speed data and vibration data during rotational operation of the mechanical device; a conversion step of converting the vibration data from a time domain to an angle domain using the rotational speed data and the vibration data acquired in the acquisition step; a reconversion step of reconverting the vibration data converted in the conversion step into a time domain based on a predetermined reference speed; and a diagnosis step of diagnosing the condition of the mechanical device using the vibration data converted in the reconversion step, wherein in the conversion step, if the rotational speed data includes a section where the rotational speed is zero or approximately equal to zero, the rotational speed data is corrected so that the rotational speed fluctuates in that section, and then the vibration data is converted into the angle domain.

[0008] Another aspect of the present invention has the following configuration: a condition monitoring device for a rotating machine comprising: an acquisition unit that acquires rotational speed data and vibration data during rotational operation of the machine; a conversion unit that converts the vibration data from a time domain to an angle domain using the rotational speed data and the vibration data acquired by the acquisition unit; a reconversion unit that reconverts the vibration data converted by the conversion unit into a time domain based on a predetermined reference speed; and a diagnosis unit that diagnoses the condition of the machine using the vibration data converted by the reconversion unit, wherein when the rotational speed data includes a section where the rotational speed is zero or approximately equal to zero, the conversion unit corrects the rotational speed data so that the rotational speed fluctuates in that section, and then converts the vibration data into the angle domain.

[0009] Another aspect of the present invention has the following configuration: That is, the program causes a computer to execute: an acquisition step of acquiring rotational speed data and vibration data during rotational operation of a mechanical device; a conversion step of converting the vibration data from a time domain to an angle domain using the rotational speed data and the vibration data acquired in the acquisition step; a reconversion step of reconverting the vibration data converted in the conversion step into a time domain based on a predetermined reference speed; and a diagnosis step of diagnosing a state of the mechanical device using the vibration data converted in the reconversion step, wherein in the conversion step, if the rotational speed data includes a section where the rotational speed is zero or approximately equal to zero, the rotational speed data is corrected so that the rotational speed fluctuates in that section, and then the vibration data is converted into the angle domain.

[0010] The present invention makes it possible to accurately monitor the state of a mechanical device even in an environment where the rotational speed of the mechanical device during rotation operation may change intermittently, even if changes in rotational speed occur, including the stop of rotation.

[0011] 1 is a schematic diagram showing an example of a functional configuration according to an embodiment of the present invention. A graph for explaining data conversion according to an embodiment of the present invention. A flowchart of condition monitoring processing according to an embodiment of the present invention. A graph for showing an example of the rotation speed of a bearing. A graph for showing an example of vibration data generated in a bearing. A graph for showing an example of vibration data converted into the angle domain. A graph for showing an example of vibration data reconverted from the angle domain into the time domain. A graph for showing an example of the results of applying envelope FFT processing to vibration data. A graph for explaining the flow of vibration data conversion according to this embodiment. A graph for explaining a problem addressed in this embodiment. A graph for explaining the flow of vibration data conversion according to this embodiment. A graph for explaining an example of a rotation speed according to this embodiment. A graph for showing an example of a processing result by the condition monitoring processing according to this embodiment. A graph for showing an example of a processing result by the condition monitoring processing according to this embodiment.

[0012] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. Note that the embodiment described below is one embodiment for explaining the present invention and is not intended to be interpreted as limiting the present invention. Furthermore, not all of the configurations described in each embodiment are necessarily essential configurations for solving the problems of the present invention. Furthermore, in each drawing, the same components are assigned the same reference numerals to indicate correspondence.

[0013] First Embodiment A first embodiment of the present invention will be described below. The method according to this embodiment is applicable to bearings that operate at low rotation speeds below a certain rotation speed, such as rolling bearings, or bearings that have large fluctuations in rotation speed. Furthermore, there are no particular limitations on the type of mechanical device that serves as a bearing device equipped with a bearing.

[0014] Fig. 1 is a schematic diagram showing an example of the functional configuration according to this embodiment. Fig. 1 shows the configuration of a rolling bearing 100 to be monitored according to this embodiment, and a monitoring device 200 that performs condition monitoring processing. The rolling bearing 100 is provided in a bearing device and rotatably supports a main shaft 105. Note that in this embodiment, the rolling bearing 100 can be, for example, a tapered roller bearing, a cylindrical roller bearing, etc., but is not limited to these.

[0015] The monitoring device 200 may be provided integrally with a mechanical device (not shown) that is equipped with the rolling bearing 100, or may be provided external to that mechanical device. Furthermore, in order to simplify the explanation, Figure 1 shows a configuration in which one monitoring device 200 monitors one rolling bearing 100. However, this configuration is not limiting, and one monitoring device 200 may be configured to monitor the status of a plurality of rolling bearings 100.

[0016] The rolling bearing 100 includes an inner ring 101, which is a rotating ring fitted onto the outside of a main shaft 105; an outer ring 103, which is a fixed ring fitted into a housing (not shown); a plurality of balls (rollers), which are a plurality of rolling elements 102 arranged between the inner ring 101 and the outer ring 103; and a cage 104, which holds the rolling elements 102 so that they can roll freely. In addition, in the rolling bearing 100, friction between the inner ring 101 and the rolling elements 102 and between the outer ring 103 and the rolling elements 102 is reduced by a predetermined lubrication method. The lubrication method is not particularly limited, and grease lubrication, oil lubrication, or the like can be used, for example. The type of lubricant is also not particularly limited.

[0017] A vibration sensor 110 is provided to detect vibrations generated from the rolling bearing 100 while the main shaft 105 is rotating. The vibration sensor 110 is fixed near the outer ring of the housing by bolting, gluing, bolting and gluing, or embedding in a molding material. If the vibration sensor 110 is fixed by bolts, it may be provided with an anti-rotation function. The vibration sensor 110 is not limited to being fixed at a detection position, but may be installed at a position that allows it to detect vibrations caused by the rolling bearing 100 during condition monitoring. Therefore, the vibration sensor 110 may be detachable or movable.

[0018] The vibration sensor 110 may be any sensor capable of detecting vibrations, such as an acceleration sensor, an acoustic emission (AE) sensor, an ultrasonic sensor, or a shock pulse sensor, as long as it can convert detected vibrations, such as acceleration, velocity, strain, stress, or displacement, into an electrical signal. When installing the sensor in a noisy environment, it is preferable to use an insulated sensor, as it is less susceptible to noise. Furthermore, when the vibration sensor 110 uses a vibration detection element, such as a piezoelectric element, the element may be molded in plastic or the like.

[0019] The rolling bearing 100 is also provided with a rotational speed sensor 112 that detects the rotational speed of the inner ring 101 fitted onto the main shaft 105. In this embodiment, the rotational speed and rotational frequency of the inner ring 101, which is a rotating ring, and the main shaft 105 are the same. The rotational speed of the main shaft 105 may vary in response to an external factor or a control command for the mechanical device. Furthermore, the rotational speed may be adjusted by a brake device (not shown). The rotational speed sensor 112 may detect the rotational speed, for example, by detecting an encoder (not shown) provided on the inner ring 101 of the rolling bearing 100. The rotational speed sensor 112 according to this embodiment is configured to be able to detect changes in the rotational speed during one rotation of the rolling bearing 100. Note that the vibration sensor 110 and the rotational speed sensor 112 may be configured to perform detection operations only at designated times (e.g., during a monitoring time period) or may be configured to perform detection operations continuously.

[0020] The amplifier 111 amplifies the electrical signal detected by the vibration sensor 110 and inputs the amplified signal to the monitoring device 200. The degree of amplification is not particularly limited, but is determined in advance. The detection timings of the vibration sensor 110 and the rotation speed sensor 112 correspond to each other, and the detected information is processed in association with each other.

[0021] The monitoring device 200 may be realized, for example, by an information processing device including a control device, a storage device, and an input / output device (not shown). The control device may be composed of a central processing unit (CPU), a micro processing unit (MPU), a digital single processor (DSP), or a dedicated circuit. The storage device is composed of volatile and non-volatile storage media such as a hard disk drive (HDD), a read-only memory (ROM), or a random access memory (RAM), and is capable of inputting and outputting various information in response to instructions from the control device. The input / output device notifies external devices and operators in response to instructions from the control device. The output method of the input / output device is not particularly limited, and may be, for example, an audible notification via voice or a visual notification via screen output. The input / output device may also be a network interface equipped with a communication function, and may perform various input / output operations by sending and receiving data to and from an external device (not shown) via a network (not shown).

[0022] The monitoring device 200 includes an A / D conversion unit 201, a data conversion unit 202, a vibration signal processing unit 203, and a monitoring processing unit 204. Each unit may be realized by the above-mentioned control device reading and executing a corresponding program from a storage device. Furthermore, the control device may realize various functions by controlling an input / output device.

[0023] The A / D converter 201 acquires the electrical signal detected by the vibration sensor 110 as vibration information via the amplifier 111, and performs A / D (Analog / Digital) conversion according to the content of the electrical signal.

[0024] The data conversion unit 202 performs conversion processing on the vibration signal processed by the A / D conversion unit 201 to data to be used for processing by the subsequent vibration signal processing unit 203 and monitoring processing unit 204, based on the rotation speed detected by the rotation speed sensor 112. An example of this conversion processing will be described later. The converted data is output to the vibration signal processing unit 203.

[0025] The vibration signal processing unit 203 performs signal analysis processing using the data output from the data conversion unit 202. In the signal analysis processing, an FFT (Fast Fourier Transform) analysis is performed, followed by an order ratio analysis. The signal analysis processing may also be performed by envelope processing or filtering using a low-pass filter, a band-pass filter, or the like.

[0026] The monitoring processing unit 204 diagnoses the condition of the rolling bearing 100 using the data processed by the vibration signal processing unit 203 and outputs the diagnosis results. For example, a portion of the data processed by the vibration signal processing unit 203 may be extracted and the condition may be diagnosed using this data. There are no particular restrictions on the diagnostic items for the condition monitoring performed by the monitoring processing unit 204, and any diagnostic item may be targeted, such as rotational slippage, orbital slippage, abnormal contact, poor lubrication, and damage or deterioration of parts of each part that makes up the rolling bearing 100.

[0027] The monitoring results of the monitoring processing unit 204 may be notified to the outside via a network (not shown), or may be used to control the operation of a mechanical device.

[0028] [Vibration Data Conversion] Vibration data conversion according to this embodiment will now be described. Note that FIG. 2 and the graphs in FIGS. 4A to 8 (described later) are examples provided for explaining this embodiment. FIG. 2 is a diagram for explaining vibration data conversion according to this embodiment. FIG. 2(a) shows an example of vibration data A obtained from a measurement object via the vibration sensor 110. In FIG. 2(a), the horizontal axis represents time [s], and the vertical axis represents amplitude. Actual bearing vibration data is data in which many different vibrations at different frequencies are superimposed. However, this example uses an example in which vibration data A includes only two vibration data sets, B and C. In the example shown in FIG. 2(a), the angular velocity of the rolling bearing increases over time, and the rotation speed increases proportionally. As a result, of the two vibration data sets, B and C, the frequency of vibration data C gradually increases over time, and the overall waveform of vibration data A shown in FIG. 2(a) also changes. In FIG. 2(a), the envelope shown above the vibration data corresponds to the waveform showing the results of envelope processing. The rotation speed is not limited to the fluctuations shown in FIG. 2(a), and may decrease over time, or may increase or decrease within a certain period of time.

[0029] FIG. 2(b) shows the results of applying envelope processing to the waveform shown in FIG. 2(a) and FFT (Fast Fourier Transform) processing. In FIG. 2(b), the horizontal axis represents frequency [Hz], and the vertical axis represents intensity. At this time, due to fluctuations in the rotation speed in the vibration data C, no frequency peaks can be detected, as shown in region 210 in FIG. 2(b). Therefore, it is not possible to identify the frequency characteristics of the vibration data C, making analysis based on the frequency characteristics difficult.

[0030] For example, frequency analysis is used when monitoring the condition of a rolling bearing. The natural frequency of the vibration of a rolling bearing is proportional to the angular velocity during rotation, and frequency analysis requires the use of data in a state where the rolling bearing is rotating at a constant speed. However, there are cases where the angular velocity fluctuates during one rotation of the rolling bearing, causing the frequency of vibration to change. In this embodiment, vibration data sampled at equal time intervals in a state where the angular velocity fluctuates is converted into vibration data corresponding to a state where the angular velocity is constant, i.e., rotation at a constant speed.

[0031] Fig. 2(c) shows an example of vibration data D obtained by applying processing for removing the influence of fluctuations in the rotation speed according to this embodiment to the vibration data A shown in Fig. 2(a). In Fig. 2(c), the horizontal axis represents time [s] and the vertical axis represents amplitude. In Fig. 2(c), the vibration data A in Fig. 2(a) is converted to correspond to a state in which the angular velocity is constant, i.e., rotation at a constant speed.

[0032] In the conversion method according to this embodiment, first, the original vibration data and a predetermined angular velocity are used to calculate t ０ The predetermined angular velocity here is the initial angular velocity ω in the vibration data. ０ However, the present invention is not limited to this. For example, the angular velocity may be the average value or maximum value of the angular velocity in a predetermined range of the vibration data. Alternatively, the angular velocity may be the angular velocity at a predetermined timing of the vibration data.

[0033]

[0034] Furthermore, the vibration data A before conversion and the vibration data D after conversion are converted using the following equation (2).

[0035] D(t １ ) = A(t ０ ) ... (2) A(t): vibration data before conversion at time t D(t): vibration data after conversion at time t

[0036] By performing the conversion using the above equations (1) and (2), the vibration data D shown in FIG. 2C is obtained. That is, the vibration data D is obtained by converting the vibration data D into the vibration data D at a constant angular velocity (here, the initial angular velocity ω０ 2C, the envelope curve shown above the vibration data D corresponds to the waveform that shows the result of envelope processing.

[0037] Figure 2(d) shows the results of applying envelope processing and FFT processing to the waveform shown in Figure 2(c). In Figure 2(d), the horizontal axis represents frequency [Hz] and the vertical axis represents intensity. Since the rotation speed of the waveform is assumed to be constant, frequency peaks can be detected as shown in region 211 in Figure 2(d), making it possible to perform analysis based on the frequency characteristics.

[0038] In the above flow, an example is shown in which the vibration data is subjected to data conversion processing, envelope processing, and FFT processing in this order, but this is not limited to this. For example, the processing may be performed in the order of envelope processing, data conversion processing, and FFT processing. Alternatively, only data conversion processing and FFT processing may be performed without envelope processing.

[0039] Since the number of samples when acquiring the vibration data A is finite, the time t ０ Vibration data A(t ０ ) may not exist in the vibration data A obtained by the vibration sensor 110, etc. In such a case, a predetermined range a is set in advance, and t ０ t within a predetermined range based on ０ Vibration data A(t ０ The vibration data D may be obtained using the above equation.

[0040] D(t １ ) = A(t ０ ') (t ０ -a<t ０ '<t ０ + a) ... (3)

[0041] Or, t as in the following equation (4): ０ The t before and after (for convenience, t ０ -1, t ０ Alternatively, an interpolation formula based on vibration data A(t) corresponding to the vibration data A(t) may be defined to obtain vibration data D.

[0042] D(t １ ) = {A(t ０ −1) + A(t ０ +1)} / 2 ... (4)

[0043] The data interpolation method used in data conversion may be a method other than those described above, and the interpolation method to be applied may be switched depending on the purpose.

[0044] Furthermore, in this embodiment, in the conversion of vibration data described above, processing is performed assuming that the rotation speed is 0 or close to 0. Details will be described together with processing flows and graphs.

[0045] 3 is a flowchart of the diagnostic process according to this embodiment. This process is executed by the monitoring device 200. For example, a control device (not shown) included in the monitoring device 200 may read out from a storage device (not shown) and execute a program for implementing each component shown in FIG.

[0046] 3 are executed simultaneously in parallel with the steps S301 to S303, i.e., the rotation speed data acquired by the rotation speed sensor 112 and the vibration data acquired by the vibration sensor 110 are acquired in a time-corresponding manner.

[0047] In S301, monitoring device 200 acquires rotational speed data of rolling bearing 100 via rotational speed sensor 112. Fig. 4A is a graph showing an example of rotational speed data. In Fig. 4A, the vertical axis represents rotational speed [rpm], and the horizontal axis represents time [s].

[0048] In S302, the monitoring device 200 upsamples the rotation speed data acquired in S301. The upsampling here is performed to suppress errors that may occur when converting vibration data, as will be described later. Note that the upsampling in S302 can be omitted.

[0049] In S303, the monitoring device 200 uses the data upsampled in S302 to calculate the cumulative number of rotations of the rolling bearing 100. An example of the cumulative number of rotations will be described later with reference to FIG.

[0050] In S304, monitoring device 200 acquires vibration data of rolling bearing 100 via vibration sensor 110. Figure 4B is a graph showing an example of the vibration data. In Figure 4B, the vertical axis represents the vibration value, and the horizontal axis represents time [s].

[0051] In S305, the monitoring device 200 upsamples the vibration data acquired in S304. The upsampling here is performed to suppress errors that may occur when converting the vibration data, as will be described later. The degree of upsampling is the same as in the step of S302. Note that the upsampling in S305 can be omitted.

[0052] In S306, the monitoring device 200 converts the vibration data into the angle domain using the cumulative number of rotations calculated in S303 and the vibration data upsampled in S305. The conversion method will be described later. Fig. 4C is a graph showing an example of vibration data converted into the angle domain. In Fig. 4C, the vertical axis represents the vibration value, and the horizontal axis represents the angle [rev].

[0053] In S307, the monitoring device 200 converts the vibration data converted into the angle domain in S306 back into the time domain at a reference speed. The reference speed here may be, for example, the average speed of the rolling bearing 100. In other words, the conversion is performed so as to correspond to a state in which the rolling bearing 100 is rotating at a constant speed at the reference speed, as shown in FIG. 2(c).

[0054] In S308, the monitoring device 200 downsamples the vibration data reconverted in S307. This downsampling corresponds to the upsampling in the step of S305. FIG. 4D is a graph showing an example of the vibration data after downsampling. In FIG. 4D, the vertical axis represents the vibration value, and the horizontal axis represents time [s]. Note that if the upsampling in S302 and S305 is omitted, the downsampling in S308 is also omitted.

[0055] In S309, the monitoring device 200 applies FFT processing to the vibration data downsampled in S308. A known method may be used for the FFT processing, and detailed description thereof will be omitted here. Known envelope processing, filter processing, and the like may also be performed in conjunction with the FFT processing. Figure 4E shows an example of data obtained by FFT processing. In Figure 4E, the vertical axis represents amplitude, and the horizontal axis represents frequency.

[0056] In S310, monitoring device 200 calculates a characteristic frequency corresponding to the part of rolling bearing 100 to be monitored.

[0057] In S311, the monitoring device 200 acquires a diagnostic spectrum corresponding to the characteristic frequency calculated in S310 from the data obtained by the FFT processing in S309.

[0058] In S312, monitoring apparatus 200 extracts the peak value of the diagnostic spectrum acquired in S311.

[0059] In S313, monitoring apparatus 200 determines whether the peak value extracted in S312 matches the characteristic frequency and its order calculated in S310.

[0060] In S314, the monitoring device 200 determines whether or not an abnormality has occurred in the rolling bearing 100 based on the result of the match determination in S313. For example, if the peak value matches a characteristic frequency and its order, it may be determined that an abnormality exists in the part corresponding to that characteristic frequency. Note that the diagnostic items here are not limited to the presence or absence of an abnormality. For example, any diagnostic item may be targeted, such as rotational slippage or orbital slippage of the rolling bearing 100, or abnormal contact, poor lubrication, or damage or deterioration of parts that make up the rolling bearing 100.

[0061] In S315, the monitoring device 200 outputs the determination result of S314 as the result of the status monitoring. The output method here is not particularly limited, and may be a visual display on a screen or an audible output from a speaker or the like. Alternatively, when it is determined that an abnormality has occurred, it may be output as a control signal for controlling the operation of the mechanical device. Furthermore, it may be output to a user or the like at the timing when it is determined that an abnormality has occurred, or it may be output at a predetermined timing. Then, this processing flow ends.

[0062] The processing from step S309 onward shown in FIG. 3 may be equivalent to the method described in, for example, Japanese Patent Application Laid-Open No. 2023-75685.

[0063] (Conversion Processing) The conversion of vibration data in the abnormality diagnosis method according to this embodiment will be described below. Fig. 5 is a graph diagram for explaining the conversion of vibration data based on the order tracking method described with reference to Fig. 2 .

[0064] Fig. 5(a) is a graph showing an example of the cumulative number of rotations of the rolling bearing 100. In Fig. 5(a), the vertical axis represents the total number of rotations, and the horizontal axis represents time. The total number of rotations is obtained by cumulatively integrating the rotation speed obtained by the rotation speed sensor 112.

[0065] Fig. 5B is a graph showing an example of vibration data obtained by the vibration sensor 110. In Fig. 5B, the vertical axis represents the vibration value, and the horizontal axis represents time.

[0066] Fig. 5(c) is a graph showing the correspondence relationship between vibration value and total rotation angle. In Fig. 5(c), the vertical axis represents vibration value and the horizontal axis represents total rotation angle. The correspondence relationship shown in Fig. 5(c) is derived from the values ​​of the graph shown in Fig. 5(a) and the values ​​of the graph shown in Fig. 5(b).

[0067] For example, times t1, t2, and t3 corresponding to predetermined total rotation counts b1, b2, and b3 are identified by referring to the graph shown in FIG. 5(a). Next, vibration values ​​a1, a2, and a3 corresponding to the identified times t1, t2, and t3 are identified by referring to the graph shown in FIG. 5(b). Then, the values ​​shown in FIG. 5(c) are derived from these correspondences. The total rotation angle is derived from the total rotation count.

[0068] Here, consider a case where the rotational speed temporarily becomes 0 while the rolling bearing 100 is operating. For example, this corresponds to a timing when there is no change in the rotational speed temporarily in the total number of rotations of the rolling bearing 100 as shown in Figure 5(a).

[0069] FIG. 6 is a graph focusing on the vicinity of the time when the rotation speed is zero. In FIG. 6, the vertical axis represents the total number of rotations, and the horizontal axis represents time. In this example, a section where the speed is zero (hereinafter also referred to as a "zero speed section") is included. When referring to the time when the total number of rotations is b1, any of times t1, t2, and t3 applies. In other words, there is no one-to-one relationship between the total number of rotations and time. Therefore, even if an attempt is made to identify the vibration value based on this value by referring to the graph of FIG. 5(b), it is not possible to uniquely identify the correspondence between the total number of rotations and the vibration value. Therefore, in such a zero speed section of the total number of rotations, the method shown in FIG. 2 cannot be used as is.

[0070] Therefore, in this embodiment, data conversion is possible by correcting the zero speed section so that the speed appears to be changing. Figure 7 is a graph for explaining an example of data conversion according to this embodiment. The configurations of Figures 7(b) and 7(c) are similar to those of Figures 5(b) and 5(c).

[0071] In Figure 7(a), the vertical axis represents the total number of rotations, and the horizontal axis represents time. In this embodiment, first, a zero speed interval is identified in the total number of rotations. If there is no zero speed interval, data conversion is performed as described using Figure 5. On the other hand, if a zero speed interval is included, its time width is identified. Then, based on that time width, the total number of rotations is corrected so that it changes at a predetermined increase rate. Line 701 shows an example of the corrected value of the total number of rotations near the zero speed interval.

[0072] As shown in FIG. 7A, the range (time) to be corrected may include the range before and after the zero speed section. The rate of increase or decrease (amount of change) may be predetermined or may be varied depending on the length of the zero speed section. As described above, since upsampling is applied before data conversion, the rate of increase or decrease may be defined based on the sampling period. The rate of increase or decrease of the rotation speed in the zero speed section may also be determined based on the degree of change in the rotation speed around the zero speed section. For example, if the rotation speed changes rapidly before and after the zero speed section, the rate of increase may be increased.

[0073] 7A shows an example in which correction is made with a monotonically increasing curve as shown by the line 701, but the present invention is not limited to this. For example, the rotation speed may be increased in the first half of the time period depending on the duration of the zero speed section, and may be decreased in the second half. Furthermore, the present invention is not limited to an increase shown by a straight line, and may be corrected with an increase shown by a curve.

[0074] Furthermore, if the duration of the zero speed section exceeds a predetermined threshold, the diagnosis may be interrupted. In this case, the diagnosis may be divided into a period before the zero speed section occurs and a period after the zero speed section occurs, and each period may be diagnosed separately. Furthermore, if the duration of the zero speed section exceeds a predetermined threshold, some of the rotational speed data and vibration data included in that period may be thinned out and used in the diagnosis process. This reduces the amount of data and the processing load.

[0075] Furthermore, in this embodiment, the rotational speed being "0 (zero)" does not necessarily mean that the rolling bearing is stopped, but may also mean that the rotational speed is approximately equal to 0. The range indicated by "approximately" here may be determined according to the measurement accuracy and sampling period of the sensor, etc.

[0076] Furthermore, in this embodiment, it is sufficient to define a unique correspondence between the total number of rotations and the vibration value. Therefore, even if a point where the rotation speed is zero is included, correction may be omitted as long as the above correspondence can be uniquely identified. For example, if the time of the zero speed section where the rotation speed is zero is extremely short, the zero speed section may be treated as not being included.

[0077] FIG. 8 is a graph showing an example of a zero speed section. In FIG. 8( a), the vertical axis represents the rotation speed, and the horizontal axis represents time. In FIG. 8( b), the vertical axis represents the total number of rotations, and the horizontal axis represents time. FIG. 8( a) and FIG. 8( b) correspond to each other. A zero speed section exists at around 2 seconds. In FIG. 8( a), this is section 801, and in FIG. 8( b), this is section 802. Such a zero speed section is identified, and the rotation speed is corrected as described above.

[0078] [Test Result Examples] Test result examples using the method according to this embodiment will be described with reference to FIGS.

[0079] 9 shows an example of test results for a device such as a linear motion machine whose rotational speed changes rapidly over a short period of time. FIG. 9( a) is a graph showing an example of the rotational speed acquired by the rotational speed sensor 112. In FIG. 9( a), the vertical axis represents the rotational speed, and the horizontal axis represents time. FIG. 9( b) is a graph showing an example of the vibration value acquired by the vibration sensor 110. In FIG. 9( b), the vertical axis represents the vibration value, and the horizontal axis represents time. As shown in FIG. 9( a), there is a period in which the rotational speed becomes zero, and a zero speed section exists.

[0080] The results obtained by applying the above-described correction to such detection data and performing FFT processing are shown in Figure 9(c). In Figure 9(c), the vertical axis represents amplitude, and the horizontal axis represents frequency. In Figure 9(c), the hatched area represents an example of a feature frequency of interest and the surrounding area of ​​its order. As indicated by the circles (○) in Figure 9(c), frequency peaks can be captured, and by comparing these with the feature frequency of the part to be diagnosed, it is possible to determine whether an abnormality exists.

[0081] Fig. 10 shows an example of test results for a device whose rotational speed varies moderately, such as a hoist. Fig. 10(a) is a graph showing an example of the rotational speed acquired by the rotational speed sensor 112. In Fig. 10(a), the vertical axis represents the rotational speed, and the horizontal axis represents time. Fig. 10(b) is a graph showing an example of the vibration value acquired by the vibration sensor 110. In Fig. 10(b), the vertical axis represents the vibration value, and the horizontal axis represents time. As shown in Fig. 10(a), there is a period in which the rotational speed is 0, and a zero speed section exists.

[0082] The results obtained by applying the above-described correction to such detection data and performing FFT processing are shown in Figure 10(c). In Figure 10(c), the vertical axis represents amplitude, and the horizontal axis represents frequency. In Figure 10(c), the hatched area represents an example of a feature frequency of interest and the surrounding area of ​​its order. As indicated by the circles (○) in Figure 10(c), frequency peaks can be captured, and by comparing these with the feature frequency of the part to be diagnosed, it is possible to determine whether an abnormality exists.

[0083] Fig. 11 shows an example of test results for a device in which the rotational speed changes gradually. Fig. 11(a) is a graph showing an example of the rotational speed acquired by the rotational speed sensor 112. In Fig. 11(a), the vertical axis represents the rotational speed, and the horizontal axis represents time. Fig. 11(b) is a graph showing an example of the vibration value acquired by the vibration sensor 110. In Fig. 11(b), the vertical axis represents the vibration value, and the horizontal axis represents time. As shown in Fig. 11(a), there is a period in which the rotational speed becomes 0, and a zero speed section exists.

[0084] The results obtained by applying the above-described correction to such detection data and performing FFT processing are shown in Figure 11(c). In Figure 11(c), the vertical axis represents amplitude, and the horizontal axis represents frequency. In Figure 11(c), the hatched area represents an example of a feature frequency of interest and the surrounding area of ​​its order. As indicated by the circles (○) in Figure 11(c), frequency peaks can be captured, and by comparing these with the feature frequency of the part to be diagnosed, it is possible to determine whether an abnormality exists.

[0085] 9 to 11, even when the rotation speed changes and includes a section where the rotation speed is equal to 0, the technique according to this embodiment makes it possible to properly identify the frequency peak position, thereby making it possible to properly determine whether the device being diagnosed has an abnormality.

[0086] When performing an abnormality determination using the vibration data obtained in this embodiment, a trend value may be calculated from the vibration waveform and used. In this case, in addition to the peak value (maximum value), for example, RMS (Root Mean Square), wave efficiency, kurtosis, skewness, etc. may be used as the trend value.

[0087] As described above, this embodiment makes it possible to accurately monitor the state of a mechanical device even in an environment where the rotational speed of the mechanical device during rotational operation may change intermittently, even if a change in rotational speed occurs, including a stop of rotation.

[0088] <Other Embodiments> Furthermore, the present invention can also be realized by supplying a program or application for realizing the functions of one or more of the above-described embodiments to a system or device using a network or a storage medium, etc., and having one or more processors in a computer of the system or device read and execute the program.

[0089] Alternatively, it may be realized by a circuit that realizes one or more functions (for example, an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array)).

[0090] As such, the present invention is not limited to the above-described embodiments, and the present invention also contemplates the mutual combination of the various components of the embodiments, as well as modifications and applications by those skilled in the art based on the description in the specification and well-known techniques, and these modifications and applications are included in the scope of protection sought.

[0091] As described above, this specification discloses the following: (1) A condition monitoring method for a mechanical device (e.g., 100) that performs a rotational operation, comprising: an acquisition step of acquiring rotational speed data and vibration data during rotational operation of the mechanical device; a conversion step of converting the vibration data from a time domain to an angle domain using the rotational speed data and the vibration data acquired in the acquisition step; a reconversion step of reconverting the vibration data converted in the conversion step into a time domain based on a predetermined reference speed; and a diagnosis step of diagnosing the condition of the mechanical device using the vibration data converted in the reconversion step, wherein, in the conversion step, if the rotational speed data includes a section where the rotational speed is zero or approximately equal to zero, the rotational speed data is corrected so that the rotational speed fluctuates in that section, and then the vibration data is converted into the angle domain. This configuration makes it possible to accurately monitor the condition of the mechanical device even when changes in rotational speed, including stops of rotation, occur in an environment where the rotational speed of the mechanical device may change intermittently during rotational operation.

[0092] (2) In the condition monitoring method according to (1), in the conversion step, correction is performed on the section and a range surrounding the section. With this configuration, by performing correction including the area surrounding the zero speed section, it is possible to suppress the influence of abrupt correction while maintaining consistency with the surrounding sections.

[0093] (3) The condition monitoring method according to (1) or (2), wherein the conversion step corrects the rotation speed in the section so that the rotation speed increases monotonically. This configuration makes it possible to correct the rotation speed using a simple method.

[0094] (4) The condition monitoring method according to (1) or (2), wherein the conversion step determines a rate of increase or decrease in the rotation speed for correction according to the time duration of the section. With this configuration, it is possible to correct the rotation speed according to the time duration of the zero speed section.

[0095] (5) The condition monitoring method according to any one of (1) to (4), wherein in the converting step, if the time width of the section is less than a predetermined value, the vibration data is converted into the angle domain without performing the correction. With this configuration, it is possible to switch the implementation of the correction depending on the time width of the zero speed section.

[0096] (6) The condition monitoring method according to any one of (1) to (5), wherein in the diagnosis step, if the section is longer than a predetermined time, the diagnosis is interrupted. With this configuration, it is possible to suppress the influence of correction when the zero speed section is long. In particular, it is possible to suppress a decrease in the accuracy of the diagnosis due to correction.

[0097] (7) The condition monitoring method according to any one of (1) to (6), wherein the mechanical device is a bearing device. With this configuration, it is possible to apply the method to a mechanical device including a bearing device as a diagnostic target.

[0098] (8) A condition monitoring device (e.g., 200) for a mechanical device (e.g., 100) that performs a rotational operation, the condition monitoring device comprising: an acquisition unit (e.g., 110, 112, 201-203) that acquires rotational speed data and vibration data during rotational operation of the mechanical device; a conversion unit (e.g., 202, 203) that converts the vibration data from a time domain into an angle domain using the rotational speed data and the vibration data acquired by the acquisition unit; a reconversion unit (e.g., 202, 203) that reconverts the vibration data converted by the conversion unit into a time domain based on a predetermined reference speed; and a diagnosis unit (e.g., 204) that diagnoses the condition of the mechanical device using the vibration data converted by the reconversion unit, wherein when the rotational speed data includes a section where the rotational speed is zero or approximately equal to zero, the conversion unit corrects the rotational speed data so that the rotational speed fluctuates in that section, and then converts the vibration data into the angle domain. With this configuration, in an environment where the rotational speed of the mechanical device may change intermittently during rotation, it is possible to accurately monitor the state of the mechanical device even when a change in rotational speed occurs, including a stoppage of rotation.

[0099] (9) A program that causes a computer (e.g., 200) to execute: an acquisition step of acquiring rotational speed data and vibration data during rotational operation of a mechanical device (e.g., 100); a conversion step of converting the vibration data from a time domain to an angle domain using the rotational speed data and the vibration data acquired in the acquisition step; a reconversion step of reconverting the vibration data converted in the conversion step into a time domain based on a predetermined reference speed; and a diagnosis step of diagnosing a state of the mechanical device using the vibration data converted in the reconversion step, wherein in the conversion step, if the rotational speed data includes a section where the rotational speed is zero or approximately equal to zero, the rotational speed data is corrected so that the rotational speed fluctuates in that section, and then the vibration data is converted into the angle domain. With this configuration, in an environment where the rotational speed of the mechanical device may change intermittently during rotational operation, it is possible to accurately monitor the state of the mechanical device even when changes in the rotational speed, including stops of rotation, occur.

[0100] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention. Furthermore, the components of the above-described embodiments may be combined in any manner without departing from the spirit of the invention.

[0101] This application is based on a Japanese patent application (Patent Application No. 2024-056324) filed on March 29, 2024, the contents of which are incorporated herein by reference.

[0102] The present invention has the effect of enabling accurate monitoring of the state of a mechanical device even when a change in rotational speed occurs, including a stoppage of rotation, in an environment in which the rotational speed of the mechanical device during rotational operation can change intermittently, and can be used to monitor the state of various mechanical devices, including bearing devices equipped with bearings such as rolling bearings.

[0103] DESCRIPTION OF SYMBOLS 100... Rolling bearing 101... Inner ring 102... Rolling element 103... Outer ring 104... Cage 105... Main shaft 110... Vibration sensor 111... Amplifier 112... Rotational speed sensor 200... Monitoring device 201... A / D conversion unit 202... Data conversion unit 203... Vibration signal processing unit 204... Monitoring processing unit

Claims

1. A condition monitoring method for a mechanical device that performs a rotational operation, comprising: an acquisition step of acquiring rotational speed data and vibration data during rotational operation of the mechanical device; a conversion step of converting the vibration data from a time domain to an angle domain using the rotational speed data and the vibration data acquired in the acquisition step; a reconversion step of reconverting the vibration data converted in the conversion step into a time domain at a predetermined reference speed; and a diagnosis step of diagnosing the condition of the mechanical device using the vibration data converted in the reconversion step, wherein in the conversion step, if the rotational speed data includes a section where the rotational speed is zero or approximately equal to zero, the rotational speed data is corrected so that the rotational speed fluctuates in that section, and the vibration data is then converted into the angle domain.

2. The condition monitoring method according to claim 1, wherein in the conversion step, correction is made to the section and a range surrounding the section.

3. A condition monitoring method according to claim 1, wherein in said conversion step, said rotation speed in said section is corrected so as to monotonically increase.

4. A condition monitoring method according to claim 1, wherein in said conversion step, a rate of increase or decrease in rotational speed for correction is determined according to the time width of said section.

5. A condition monitoring method according to claim 1, wherein in the conversion step, if the time width of the section is less than a predetermined value, the vibration data is converted into the angle domain without performing the correction.

6. The condition monitoring method according to claim 1, wherein in the diagnosing step, if the section is longer than a predetermined time, the diagnosis is interrupted.

7. A condition monitoring method according to any one of claims 1 to 6, wherein the mechanical device is a bearing device.

8. A condition monitoring device for a mechanical device that performs a rotational operation, comprising: an acquisition unit that acquires rotational speed data and vibration data during rotational operation of the mechanical device; a conversion unit that converts the vibration data from a time domain to an angle domain using the rotational speed data and the vibration data acquired by the acquisition unit; a reconversion unit that reconverts the vibration data converted by the conversion unit into a time domain at a predetermined reference speed; and a diagnosis unit that diagnoses the condition of the mechanical device using the vibration data converted by the reconversion unit, wherein when the rotational speed data includes a section where the rotational speed is zero or approximately equal to zero, the conversion unit corrects the rotational speed data so that the rotational speed fluctuates in that section, and then converts the vibration data into the angle domain.

9. A program that causes a computer to execute the following steps: an acquisition step of acquiring rotational speed data and vibration data during rotational operation of a mechanical device; a conversion step of converting the vibration data from a time domain to an angle domain using the rotational speed data and the vibration data acquired in the acquisition step; a reconversion step of reconverting the vibration data converted in the conversion step into a time domain based on a predetermined reference speed; and a diagnosis step of diagnosing the state of the mechanical device using the vibration data converted in the reconversion step; and in the conversion step, if the rotational speed data includes a section where the rotational speed is zero or nearly equal to zero, the rotational speed data is corrected so that the rotational speed fluctuates in that section, and the vibration data is then converted into the angle domain.

Images