Method and apparatus for evaluating health state of marine alternating current motor, and device

Abstract

A method and apparatus for evaluating the health state of a marine alternating current motor, and a device. The method comprises: using Clarke transformation to transform a plurality of fault-free three-phase current signals of a normal alternating-current motor into a standard stator current circular signal scatter diagram, and to transform a plurality of three-phase current signals under test of an alternating current motor under test into a stator current circular signal scatter diagram under test; performing region division on a target stator current circular signal scatter diagram under test to obtain a plurality of first scatter regions, and dividing the standard stator current circular signal scatter diagram to obtain a plurality of second scatter regions; determining health evaluation parameters on the basis of first coordinates of each signal point in each first scatter region and second coordinates of each signal point in each second scatter region; and on the basis of the health evaluation parameters, determining a health score of the alternating current motor under test, so as to evaluate the health state of the alternating current motor under test. In this way, the health score of an alternating current motor is quantified by using health evaluation parameters, so that the health state of the motor can be accurately evaluated on the basis of the health score.

Description

A method, device and apparatus for evaluating the health status of a marine AC motor Technical Field

[0001] The present application relates to the technical field of ship motor status monitoring, and in particular to a method, device and equipment for evaluating the health status of a ship AC motor. Background Art

[0002] As the main power and traction equipment in production activities of various industries, the working status of the motor will directly affect the production accuracy and efficiency. The motor system is an important part of rotating machinery. Accurate motor fault diagnosis is of great significance to ensure the safe operation of rotating machinery.

[0003] Temperature and vibration diagnostic methods are currently the most commonly used in mechanical fault diagnosis. The temperature diagnostic method directly measures the temperature signal changes caused by the fault by connecting a temperature sensor to the mechanical equipment. However, this method is often not sensitive enough to initial minor faults, resulting in low fault diagnosis accuracy. The vibration diagnostic method was originally a relatively direct fault diagnosis method, providing more fault information. However, due to the limitations of the motor's operating environment and working conditions, the vibration signal collected is not simply a fault signal quantity. It is also affected by the external environment and the vibration of other components during operation. Therefore, the signal extracted by the vibration detection method is significantly affected by other interference signals. Therefore, for motor fault diagnosis, the diagnostic effect of the vibration detection method is not very ideal and its applicability is not very high.

[0004] Therefore, when evaluating the health status of an AC motor using the existing technology, accuracy cannot be guaranteed.

[0005] Summary of the Invention

[0006] In response to the problems existing in the prior art, embodiments of the present invention provide a method, device and equipment for evaluating the health status of a marine AC motor, so as to solve or partially solve the technical problem in the prior art that the fault status of a marine AC motor cannot be accurately determined, resulting in an inability to accurately evaluate the health status of the motor.

[0007] A first aspect of the present invention provides a method for evaluating the health status of a marine AC motor, the method comprising:

[0008] Acquire multiple fault-free three-phase current signals of a normal AC motor, and convert the multiple fault-free three-phase current signals into a standard stator current circular signal scatter plot using Clarke transform;

[0009] Acquire multiple three-phase current signals to be measured of the AC motor to be measured, and convert the multiple three-phase current signals to be measured into an initial quantum current circular signal graph to be measured;

[0010] Determine the angle between each signal point in the initial quantum current circular signal scatter diagram and a preset direction vector, and sort the signal points according to the angle to obtain a target quantum current circular signal scatter diagram;

[0011] Dividing the target stator current circular signal scatter plot into regions according to a preset angle threshold to obtain a plurality of first scatter regions, and dividing the preprocessed standard stator current source signal scatter plot into regions according to the angle threshold to obtain a plurality of second scatter regions;

[0012] determining a health assessment parameter according to the first coordinates of each signal point in each of the first scatter point areas and the second coordinates of each signal point in each of the second scatter point areas;

[0013] A health score of the AC motor to be tested is determined according to the health assessment parameter; and a health status of the AC motor to be tested is evaluated according to the health score.

[0014] In the above solution, determining the angle between each signal point in the circular signal scatter diagram of the initial quantum current to be measured and the preset direction vector includes:

[0015] For a current vector formed by any current signal point and the origin in the circular signal scatter diagram of the initial quantum current to be measured, determining a modulus value of the current vector according to the coordinates of the current signal point and the coordinates of the origin in the circular signal scatter diagram of the initial quantum current to be measured;

[0016] Determining a modulus of the preset direction vector;

[0017] Determining a dot product between the preset direction vector and the current vector;

[0018] An angle between the current vector and the preset direction vector is determined according to the module of the current vector, the module value of the preset direction vector, and a dot product between the preset direction vector and the current vector.

[0019] In the above solution, when the health assessment parameters include: center of gravity offset and radius standard deviation, determining the health assessment parameters based on the first coordinates of each signal point in each first scatter point area and based on the second coordinates of each signal point in each second scatter point area includes:

[0020] determining a first center-of-gravity offset of each first scatter point area and a first radius of each signal point in each first scatter point area according to the first coordinates of each signal point in each first scatter point area; determining an average of each of the first center-of-gravity offsets as a current center-of-gravity offset of the circular signal scatter plot of the target sub-current to be measured;

[0021] determining a second center-of-gravity offset of each second scatter point area and a second radius of each signal point in each second scatter point area according to the second coordinates of each signal point in each second scatter point area; and determining an average of each of the second center-of-gravity offsets as a reference center-of-gravity offset;

[0022] Determining a first radius standard deviation of each first scatter point area according to the first radius of each signal point in each first scatter point area; determining a mean of each of the first radius standard deviations as a current radius standard deviation of the target to-be-measured sub-current circular signal scatter plot;

[0023] The second radius standard deviation of each second scatter point area is determined according to the second radius of each signal point in the second scatter point area; and the mean of each second radius standard deviation is determined as the reference radius standard deviation of the preprocessed standard stator current circular signal scatter plot.

[0024] In the above solution, when the health assessment parameters include: a kurtosis value, a skewness value, and a root mean square value, determining the health assessment parameters based on the first coordinates of each signal point in each of the first scatter point areas and based on the second coordinates of each signal point in each of the second scatter point areas includes:

[0025] determining first radii of all signal points in each of the first scatter point areas, and determining a minimum first radius from the first radii of all signal points;

[0026] Obtaining a distance difference between the first radius and the minimum first radius of each remaining signal point in the first scatter point area; the remaining signal points in the first scatter point area are all signal points in the first scatter point area except the signal point corresponding to the minimum first radius;

[0027] Determine, based on all the distance differences in the first scatter point areas, a kurtosis value, a skewness value, and a root mean square value of the distance differences in each first scatter point area;

[0028] determining the second radius of all signal points in each of the second scattering areas, and determining a minimum second radius from the second radii of all signal points;

[0029] Obtaining a distance difference between the second radius and the minimum second radius of each remaining signal point in the second scatter point area; the remaining signal points in the second scatter point area are all signal points in the second scatter point area except the signal point corresponding to the minimum second radius;

[0030] Based on all the distance difference values ​​in each of the second scatter point areas, a kurtosis value, a skewness value, and a root mean square value of the distance difference value in each of the second scatter point areas are determined.

[0031] In the above solution, determining the health score of the AC motor to be tested according to the health assessment parameters includes:

[0032] According to the formula Determining a reference evaluation value η of a scatter plot of a preprocessed standard stator current source signal;

[0033] According to the formula Determining a current evaluation value η′ of the circular signal scatter diagram of the target sub-current to be measured;

[0034] According to the formula Determine the health score of the AC motor under test in,

[0035] The R U is the reference radius standard deviation, the R T is the reference center of gravity offset, the R′ U is the current radius standard deviation, the R′ T is the current center of gravity offset, and γ is the reference score corresponding to the preprocessed standard stator current source signal scatter plot.

[0036] In the above solution, determining the health score of the AC motor to be tested according to the health assessment parameters includes:

[0037] Constructing a parameter matrix to be measured according to the kurtosis value, the skewness value and the root mean square value of the distance difference value in each of the first scatter point areas;

[0038] constructing a reference parameter matrix according to the kurtosis value, the skewness value and the root mean square value of the distance difference value in each of the second scatter point areas;

[0039] Determining a similarity coefficient between the parameter matrix to be measured and the reference parameter matrix;

[0040] Based on the formula Determine the health score of the AC motor to be tested, where η″ is the similarity coefficient.

[0041] In the above solution, determining the similarity coefficient between the parameter matrix to be measured and the reference parameter matrix includes:

[0042] Determining the covariance between the parameter matrix to be measured and the reference parameter matrix;

[0043] Determining a first standard deviation of the parameter matrix to be measured and a second standard deviation between the reference parameter matrix;

[0044] determining a product value between the first standard deviation and the second standard deviation;

[0045] The similarity coefficient between the parameter matrix to be measured and the reference parameter matrix is ​​determined according to the product value between the covariance, the first standard deviation and the second standard deviation; the similarity coefficient is the quotient of the covariance and the product value.

[0046] In the above solution, determining the kurtosis value, skewness value, and root mean square value of the distance difference value in each first scatter point area includes:

[0047] According to the formula Determine a kurtosis value χ of the distance difference in each first scatter point area;

[0048] According to the formula Determine a skewness value γ of the distance difference in each first scatter point area;

[0049] According to the formula Determine the root mean square value X of the distance difference in each first scatter point area rms ;in,

[0050] N is the number of distance differences in the first scatter point area, i is the sequence number of the distance differences in the first scatter point area, and d i is the i-th distance difference.

[0051] A second aspect of the present invention provides a device for evaluating the health status of a marine AC motor, the device comprising:

[0052] a conversion unit, configured to obtain a plurality of fault-free three-phase current signals of a normal AC motor, and convert the plurality of fault-free three-phase current signals into a standard stator current circular signal scatter plot using Clarke transform; obtain a plurality of three-phase current signals to be tested of the AC motor to be tested, and convert the plurality of three-phase current signals to be tested into an initial stator current circular signal plot to be tested;

[0053] a first determining unit, configured to determine an angle between each signal point in the initial to-be-measured quantum current circular signal scatter diagram and a preset direction vector, sort the signal points according to the angle to obtain a target to-be-measured quantum current circular signal scatter diagram; divide the target to-be-measured quantum current circular signal scatter diagram into regions according to a preset angle threshold to obtain a plurality of first scatter regions, and divide the preprocessed standard stator current source signal scatter diagram according to the angle threshold to obtain a plurality of second scatter regions;

[0054] A second determination unit is configured to determine a health assessment parameter based on the first coordinates of each signal point in each of the first scatter point areas and the second coordinates of each signal point in each of the second scatter point areas, determine a health score of the AC motor to be tested based on the health assessment parameter; and evaluate a health status of the AC motor to be tested based on the health score.

[0055] According to a third aspect of the present invention, a computer device is provided, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the steps of any one of the methods described in the first aspect are implemented.

[0056] The present invention provides a method, device, and apparatus for evaluating the health status of a marine AC motor. The method comprises: obtaining multiple fault-free three-phase current signals of a normal AC motor, and converting the multiple fault-free three-phase current signals into standard stator current circular signal scatter plots using Clarke transform; obtaining multiple three-phase current signals to be tested of an AC motor to be tested, and converting the multiple three-phase current signals to be tested into initial stator current circular signal plots to be tested; determining the angle between each signal point in the initial stator current circular signal scatter plot and a preset direction vector, and sorting each signal point according to the angle to obtain a target stator current circular signal scatter plot to be tested; dividing the target stator current circular signal scatter plot into regions according to a preset angle threshold to obtain multiple first scatter point regions, and dividing the preprocessed standard stator current source signal scatter plot into multiple second scatter point regions according to the angle threshold; determining a health assessment parameter according to the first coordinate of each signal point in each first scatter point region and the second coordinate of each signal point in each second scatter point region; determining a health score of the AC motor to be tested according to the health assessment parameter; and evaluating the health status of the AC motor to be tested according to the health score. In this way, based on the collected stator current, the Clarke transform is used to convert multiple fault-free three-phase current signals of a normal AC motor into a standard stator current circular signal scatter plot, and multiple three-phase current signals to be tested of the AC motor to be tested are converted into a stator current circular signal plot to be tested; the health assessment parameters are determined according to the coordinates of each signal point in each scatter point area, and the health score of the AC motor is quantified using the health assessment parameters, so that the health status of the motor can be accurately assessed based on the health score. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present invention. The same reference symbols are used throughout the drawings to represent the same components. In the drawings:

[0058] FIG1 is a schematic flow chart of a method for evaluating the health status of a marine AC motor according to one embodiment of the present invention;

[0059] FIG2 shows a waveform diagram of a fault-free three-phase AC signal according to an embodiment of the present invention;

[0060] FIG3 shows a standard stator current circular signal diagram corresponding to a fault-free three-phase AC signal according to an embodiment of the present invention;

[0061] 4 to 10 show circular signal diagrams of sub-currents to be measured corresponding to different types of faults occurring in an AC motor according to an embodiment of the present invention;

[0062] FIG11 is a schematic diagram showing the angle between the current vector and the direction vector in the initial to-be-measured quantum current circular signal scatter diagram according to one embodiment of the present invention;

[0063] FIG12 shows a schematic structural diagram of a device for evaluating the health status of a marine AC motor according to an embodiment of the present invention. DETAILED DESCRIPTION

[0064] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0065] The present invention provides a method for evaluating the health status of a marine AC motor, as shown in FIG1 , the method comprising the following steps:

[0066] S110, obtaining multiple fault-free three-phase current signals of a normal AC motor, and converting the multiple fault-free three-phase current signals into a standard stator current circular signal scatter plot using Clarke transform; obtaining multiple three-phase current signals to be tested of the AC motor to be tested, and converting the multiple three-phase current signals to be tested into an initial stator current circular signal diagram to be tested.

[0067] In the embodiments of this specification, multiple fault-free three-phase current signals (U, V, and W signals) of an AC motor can be obtained by using a current transformer based on a preset acquisition frequency. Alternatively, multiple fault-free three-phase current signals can be obtained through simulation experiments, without limitation. A waveform diagram of the three-phase current signal is shown in FIG2 .

[0068] The multiple fault-free three-phase current signals are then converted into a standard stator current circular signal graph using the Clarke transform. The Clarke transform is a mathematical transformation method that converts three-phase voltage or current into components on two orthogonal axes. Its purpose is to convert complex variations in three-phase voltage or current into simple variations on two orthogonal axes, enabling more accurate analysis and calculations, and improving the stability and efficiency of subsequent data processing.

[0069] In one embodiment, converting a plurality of fault-free three-phase current signals into a standard stator current circular signal diagram includes:

[0070] For any three-phase current signal without fault, according to the formula Convert the three-phase current signal into the d-axis component I of the orthogonal axis d ;

[0071] According to the formula Convert the three-phase current signal into the q-axis component I of the orthogonal axis q ;

[0072] Establish an orthogonal coordinate system with the d-axis component I of each fault-free three-phase current d As the horizontal axis, the q-axis component I of each fault-free three-phase current q Plot the corresponding standard electron current circular signal diagram for the vertical axis.

[0073] Specifically, assuming that the three-phase current signal I includes: a-phase current signal I a , b-phase current signal I b and c-phase current signal I c , then it can be expressed as a complex vector: I=I a +jI b +j 2 I c (1)

[0074] In formula (1), j is an imaginary unit.

[0075] The complex vector is then transformed to convert the complex vector into components on two orthogonal axes, where the orthogonal axes include a d-axis and a q-axis.

[0076] First, define the d-axis component as the average value of the three-phase current, that is:

[0077] Then, define the q-axis component as the imbalance of the three-phase current, that is:

[0078] Using the above method, we perform a Clarke transform on the fault-free three-phase current signals corresponding to all sampling points to obtain the d-axis and q-axis components of each fault-free three-phase current signal. In this paper, the d-axis signal is used as the Alpha signal, and the q-axis signal as the Beta signal. We then plot the corresponding standard stator current circular signal using the Alpha signal as the horizontal axis and the Beta signal as the vertical axis, as shown in Figure 3.

[0079] Similarly, for the AC motor to be tested, multiple three-phase current signals to be tested of the AC motor to be tested are obtained, and the multiple three-phase current signals to be tested are converted into an initial quantum current circular signal graph to be tested.

[0080] Among them, the method of converting multiple three-phase current signals to be measured into the initial stator current circular signal diagram to be measured can refer to the method of converting multiple fault-free three-phase current signals into the standard stator current circular signal diagram above, which will not be repeated here.

[0081] Here, the corresponding quantum current circular signals to be measured for AC motors with different faults are shown in Figures 4 to 10. It is understandable that for an AC motor with the same fault, the quantum current circular signals to be measured determined using current data sampled at different times will vary.

[0082] S111 , determining the angle between each signal point in the initial quantum current circular signal scatter diagram and a preset direction vector, and sorting the signal points according to the angle to obtain a target quantum current circular signal scatter diagram.

[0083] It's understood that the standard stator current circular signal scatter plot represents the ideal operating state of an AC motor. Therefore, the stator current circular signal plot corresponding to the three-phase current signal under test can be compared with the standard stator current circular signal scatter plot. If the two circular signal plots are very close, the motor under test can be assumed to be operating normally. If the two circular signal plots differ significantly, it may indicate a fault or abnormality in the motor under test.

[0084] In practical applications, multiple three-phase current signals to be measured are generated after the motor rotates multiple times. In order to more accurately detect the health status of the motor to be measured, the present invention needs to reorder the signal points in the initial scatter diagram of the quantum current circular signal to be measured to obtain the scatter diagram of the target quantum current circular signal to be measured.

[0085] Then, in one embodiment, determining the angle between each signal point in the initial to-be-measured quantum current circular signal scatter diagram and the preset direction vector includes:

[0086] For a current vector formed by any current signal point and the origin in the initial quantum current circular signal scatter diagram, a modulus value of the current vector is determined according to the coordinates of the current signal point and the coordinates of the origin in the initial quantum current circular signal scatter diagram;

[0087] Determine the modulus of the preset direction vector;

[0088] Determine the dot product between the preset direction vector and the current vector;

[0089] The angle between the current vector and the preset direction vector is determined according to the modulus of the current vector, the modulus of the preset direction vector, and the dot product between the preset direction vector and the current vector.

[0090] Specifically, a direction vector, such as (0, -1), is preset. The angles between each signal point in the initial circular scatter plot of the quantum current to be measured and the direction vector are then determined. The signal points are then reordered in ascending order of angle. This reordered signal point pattern more accurately describes the rotation of the motor under test, allowing for a more precise determination of the motor's operating status.

[0091] It can be understood that the coordinates of each signal point in the initial circular signal scatter diagram of the quantum current to be measured are consistent, and a vector can be formed between each signal point and the origin. Therefore, for any current signal point, the current vector formed by the current signal point and the origin in the initial circular signal scatter diagram of the quantum current to be measured can be determined based on the coordinates of the signal point, and then the direction vector and the modulus of the current vector can be determined respectively. The angle between the current vector and the direction vector can be determined based on the click between the modulus, the direction vector and the current vector.

[0092] For example, referring to FIG11 , for any current signal point A, assuming that the coordinates of A are (x1, y1), the origin coordinates O are (0, 0), and the direction vector OB is (0, -1); then the modulus value |OA| of the current vector OA is:

[0093] The modulus of the direction vector |OB| is:

[0094] The dot product OA·OB between the current vector OA and the direction vector OB is: OA·OB=x1*0+y1*(-1) (3)

[0095] Then, the arc angle θ between the current vector and the direction vector is determined according to formula (4):

[0096] Since the calculated θ is in radians, it is also necessary to convert the radians into the corresponding angle θ′ according to formula (5):

[0097] According to the above method, the angle of each signal point in the initial to-be-measured quantum current circular signal scatter diagram can be determined.

[0098] It should be noted that when calling the function to calculate the angle of each signal point, if the angle of the signal point is greater than 180, the output value of the function is the complementary angle between the angle between the signal point and the direction vector. This situation cannot accurately reflect the angular difference between all signal points and the direction vector. To avoid this situation, when determining the angle of each signal point, the present invention divides the initial circular signal scatter plot of the quantum current to be measured into a positive half-zone and a negative half-zone, and calculates the angle of each signal point separately. The positive half-zone range is 180 degrees counterclockwise from the 270-degree axis (the area to the right of the vertical axis); the negative half-axis, on the contrary, is the area to the left of the vertical axis.

[0099] After the angle of each signal point is determined, the direction vector is used as the starting point and the signal points are reordered in ascending order of angle to form a circular signal scatter plot of the target quantum current to be measured.

[0100] Similarly, for the standard stator current source signal scatter plot, the same method as above is required to determine the standard stator current source signal scatter plot for preprocessing. Specifically, the angle of each signal point in the standard stator current source signal scatter plot must be determined, and then the signal points in the standard stator current source signal scatter plot must be reordered from smallest to largest angle. The determination method is exactly the same as above, so it will not be repeated here.

[0101] S112, dividing the target stator current circular signal scatter plot into regions according to a preset angle threshold to obtain a plurality of first scatter regions, and dividing the preprocessed standard stator current source signal scatter plot into regions according to the angle threshold to obtain a plurality of second scatter regions;

[0102] To reduce errors in determining the health status of the motor under test, the present invention divides the target stator current circular signal scatter plot into regions according to a preset angle threshold, generating multiple first scatter regions. Furthermore, the preprocessed standard stator current source signal scatter plot is divided into regions according to the angle threshold, generating multiple second scatter regions. The number of first scatter regions and second scatter regions is the same.

[0103] For example, when the angle threshold is 40 degrees, the number of the first scatter point areas and the number of the second scatter point areas are both 9. When the angle threshold is 45 degrees, the number of the first scatter point areas and the number of the second scatter point areas are both 8.

[0104] This allows subsequent analysis of the data within each scatter plot area to ensure thorough analysis and minimize errors. For example, by dividing the circular signal scatter plot of the quantum current to be measured into multiple parts, we can more comprehensively understand the data characteristics within each angular range, analyze the data trends within each angular range, identify any subtle differences or anomalies, and improve the reliability of the assessment.

[0105] S113, determining a health assessment parameter according to the first coordinates of each signal point in each of the first scatter point areas and the second coordinates of each signal point in each of the second scatter point areas;

[0106] The health assessment parameters in the present invention may include multiple types, such as the center of gravity offset and radius standard deviation; they may also include kurtosis value, skewness value and root mean square value. Different types of health assessment parameters are determined in different ways, and the specific implementation is as follows:

[0107] In one embodiment, when the health assessment parameters include: center of gravity offset and radius standard deviation, determining the health assessment parameters based on the first coordinates of each signal point in each first scatter point area and based on the second coordinates of each signal point in each second scatter point area includes:

[0108] determining a first center-of-gravity offset of each first scatter point area and a first radius of each signal point in each first scatter point area according to the first coordinates of each signal point in each first scatter point area; determining an average of each first center-of-gravity offset as a current center-of-gravity offset of the circular signal scatter plot of the target sub-current to be measured;

[0109] determining a second center-of-gravity offset of each second scatter point area and a second radius of each signal point in each second scatter point area according to the second coordinates of each signal point in each second scatter point area; and determining an average of the second center-of-gravity offsets as a reference center-of-gravity offset;

[0110] Determine the first radius standard deviation of each first scatter point area according to the first radius of each signal point in each first scatter point area; determine the mean of each first radius standard deviation as the current radius standard deviation of the circular signal scatter plot of the target to-be-measured sub-current;

[0111] The second radius standard deviation of each second scatter point area is determined according to the second radius of each signal point in each second scatter point area; and the mean of each second radius standard deviation is determined as the reference radius standard deviation of the preprocessed standard stator current circular signal scatter diagram.

[0112] Specifically, since the current center of gravity offset and the reference center of gravity offset are determined in exactly the same way, the current center of gravity offset is used as an example for detailed explanation:

[0113] It can be understood that after the Clarke transform, the first coordinates of each signal point in each first scatter point area can be directly obtained. Then, for any first scatter point area, the horizontal coordinate x of the center of gravity of the first scatter point area can be determined based on formula (6): ak , determine the vertical coordinate y of the center of gravity of the first scattered point area according to formula (7) ak :

[0114] Among them, m j The quality of the jth signal point in each first scatter point area, the default value is 1; x j is the horizontal coordinate of the jth signal point in each first scatter point area, y j is the ordinate of the jth signal point in each first scatter point area.

[0115] Then, the center of gravity offset R of each first scatter point area is determined according to formula (8): t :

[0116] In formula (8), x0 is the abscissa of the center of the circular signal scatter diagram of the target sub-current to be measured, and y0 is the ordinate of the center of the circular signal scatter diagram of the target sub-current to be measured.

[0117] If the first scatter point area includes multiple points, multiple center of gravity offsets R can be determined. t , take the average value of multiple center of gravity offsets as the current center of gravity offset R T .

[0118] The reference center of gravity offset R′ can be determined in the same way as above T , I will not go into details here.

[0119] Since the current radius standard deviation and the reference radius standard deviation are determined in exactly the same way, the current radius standard deviation is used as an example for detailed explanation:

[0120] First, determine the first radius deviation R of each signal point in each first scatter point area according to formula (9): u :

[0121] In formula (9), r j is the first radius of the jth signal point in the first scatter area, μ k is the radius mean of all signal points in the kth first scatter area, σ k is the radius variance of all signal points in the kth first scatter point area.

[0122] Then the mean of the first radius deviations in each first scatter point area is taken as the second radius deviation R′ of the first scatter point area.u ;

[0123] Finally, the mean value of the second radius deviation of each first scatter point area is determined as the current radius deviation R of the target to-be-measured electron current circular signal scatter diagram. U .

[0124] The reference radius deviation R′ can be determined in the same way as above U , I will not go into details here.

[0125] In one embodiment, when the health assessment parameters include a kurtosis value, a skewness value, and a root mean square value, determining the health assessment parameters according to the first coordinates of each signal point in each of the first scatter point areas and according to the second coordinates of each signal point in each of the second scatter point areas includes:

[0126] determining first radii of all signal points in each first scatter point area, and determining a minimum first radius from the first radii of all signal points;

[0127] Obtaining a distance difference between the first radius and the minimum first radius of the remaining signal points in each first scatter point area; the remaining signal points are all signal points in the first scatter point area except the signal point corresponding to the minimum first radius;

[0128] Determine, based on all the distance differences in each first scatter point area, a kurtosis value, a skewness value, and a root mean square value of the distance difference in each first scatter point area;

[0129] determining the second radius of all signal points in each second scatter point area, and determining a minimum radius from the second radii of all signal points;

[0130] Obtaining a distance difference between the second radius of the remaining signal points in each second scatter point area and the minimum second radius; the remaining signal points are all signal points in the second scatter point area except the signal point corresponding to the minimum second radius;

[0131] Based on all the distance difference values ​​in each second scatter point area, a kurtosis value, a skewness value, and a root mean square value of the distance difference value in each second scatter point area are determined.

[0132] In one embodiment, determining the kurtosis value, the skewness value, and the root mean square value of the distance difference value in each first scatter point area includes:

[0133] The kurtosis value χ of the distance difference value in each first scatter point area is determined according to formula (10):

[0134] Determine the skewness value γ of the distance difference value in each first scatter point area according to formula (11):

[0135] Determine the root mean square value X of the distance difference in each first scatter point area according to formula (12): rms :

[0136] Where N is the number of distance differences in the first scatter point area, i is the sequence number of the distance difference in the first scatter point area, d i is the i-th distance difference.

[0137] Specifically, the method of determining the parameter matrix to be measured and the reference parameter matrix is ​​the same. Here we take the parameter matrix to be measured as an example:

[0138] In each first scatter point area, the number of signal points contained in the first scatter point area can be determined. For example, in a first scatter point area of ​​0 to 40 degrees, the number of signal points within the first scatter point area of ​​0 to 40 degrees can be determined by counting the number of signal points with an angle less than 40 degrees.

[0139] Then, since the coordinates of each signal point in the circular signal scatter diagram of the target sub-current to be measured are also known, the corresponding first radius can be determined according to the coordinates of each signal point.

[0140] In each first scatter point area, a minimum first radius is determined, and a distance difference between the remaining first radii and the minimum first radius is determined.

[0141] In order to accurately describe the difference between the target stator current circular signal scatter diagram and the standard stator current circular signal scatter diagram, the present invention uses the kurtosis value, skewness value and root mean square value of the distance difference to characterize the difference.

[0142] Therefore, for each first scatter point area, it is necessary to determine the kurtosis value, skewness value and root mean square value of the distance difference in the scatter point area according to the above formulas (10) to (12). Assuming that the number of first scatter point areas is 9, then 9 groups of kurtosis values, skewness values ​​and root mean square values ​​of distance differences can be obtained in the end. The parameter matrix to be measured is constructed based on the kurtosis values, skewness values ​​and root mean square values ​​of these 9 groups of distance differences.

[0143] For example, when the kurtosis value of the distance difference in the first scatter point area is χ1, the skewness value is γ1, and the root mean square value is X rms1 , and so on, the kurtosis value of the distance difference in the ninth first scatter point area is χ9, the skewness value is γ9, and the root mean square value is X rms9 , then the parameter matrix P1 to be measured is:

[0144] Similarly, for each second scatter point area in the standard stator current circular signal scatter diagram, a reference parameter matrix can be constructed in the same manner as above, which will not be described in detail here.

[0145] This determines all health assessment parameters.

[0146] S114 , determining a health score of the AC motor to be tested according to the health assessment parameters; and evaluating a health status of the AC motor to be tested according to the health score.

[0147] After the health assessment parameters are determined, a health score of the AC motor to be tested is determined according to the health assessment parameters; and a health status of the AC motor to be tested is evaluated according to the health score.

[0148] It should be noted that when different types of health assessment parameters are used to determine the health score of the AC motor to be tested, the determination method is also different.

[0149] If the health assessment parameters include: center of gravity offset and radius standard deviation, the health score of the AC motor to be tested is determined based on the health assessment parameters, including:

[0150] According to the formula Determining a reference evaluation value η of a scatter plot of a preprocessed standard stator current source signal;

[0151] According to the formula Determine the current evaluation value η′ of the circular signal scatter diagram of the target to-be-measured electron current;

[0152] According to the formula Determine the health score of the AC motor under test in,

[0153] R U is the standard deviation of the reference radius, R T is the reference center of gravity offset, R′ U is the current radius standard deviation, R′ T is the current center of gravity offset, and γ is the reference score corresponding to the scatter plot of the preprocessed standard stator current source signal.

[0154] If the health assessment parameters include: the kurtosis value, the skewness value, and the root mean square value of the distance difference, in one embodiment, determining the health score of the AC motor to be tested according to the health assessment parameters includes:

[0155] Constructing a parameter matrix to be measured according to the kurtosis value, skewness value and root mean square value of the distance difference value in each first scatter point area;

[0156] Constructing a reference parameter matrix according to the kurtosis value, the skewness value and the root mean square value of the distance difference value in each second scatter point area;

[0157] Determine the similarity coefficient between the parameter matrix to be measured and the reference parameter matrix;

[0158] Based on the formula Determine the health score S of the AC motor to be tested, where η″ is the similarity coefficient.

[0159] In one embodiment, determining a similarity coefficient between a parameter matrix to be measured and a reference parameter matrix includes:

[0160] Determine the covariance between the parameter matrix to be measured and the reference parameter matrix;

[0161] Determining a first standard deviation of the parameter matrix to be measured and a second standard deviation between the reference parameter matrix;

[0162] determining a product value between the first standard deviation and the second standard deviation;

[0163] The similarity coefficient between the parameter matrix to be measured and the reference parameter matrix is ​​determined according to the product value between the covariance, the first standard deviation and the second standard deviation; the similarity coefficient is the quotient of the covariance divided by the product value.

[0164] Specifically, when determining the first standard deviation of the parameter matrix to be measured, the mean of all elements in the parameter matrix to be measured can be determined first, and then the square of the difference between each element and the mean can be determined. All square values ​​are summed, and the sum is divided by the number of elements in the parameter matrix to be measured to obtain the first standard deviation of the parameter matrix to be measured.

[0165] Similarly, the second standard deviation of the reference parameter matrix can be determined in the above manner, which will not be described in detail here.

[0166] The product value between the first standard deviation and the second standard deviation is then determined, and the covariance is divided by the product value to obtain the similarity coefficient.

[0167] Finally, the health status of the AC motor under test can be evaluated based on the health score of the AC motor under test, including:

[0168] If it is determined that the health score is greater than or equal to a preset health threshold, it is determined that the health status of the AC motor is good;

[0169] If it is determined that the health score is less than the preset health threshold, it is determined that the health status of the AC motor is poor and may be in an abnormal working state.

[0170] The health threshold can be set based on actual conditions, such as 60, which is not limited here.

[0171] Based on the collected stator current, Clarke transform is used to convert multiple fault-free three-phase current signals of a normal AC motor into a standard stator current circular signal scatter plot, and multiple three-phase current signals to be tested of the AC motor to be tested are converted into a stator current circular signal diagram to be measured. Then, the similarity between the stator current circular signal diagram to be measured and the standard stator current circular signal diagram is compared, and the health score of the AC motor is quantified using the similarity measure, so that the health status of the motor can be accurately assessed based on the health score.

[0172] Based on the same inventive concept as the previous embodiment, this embodiment further provides a device for evaluating the health status of a marine AC motor, as shown in FIG12 . The device includes:

[0173] The conversion unit 121 is configured to obtain a plurality of fault-free three-phase current signals of a normal AC motor, and convert the plurality of fault-free three-phase current signals into a standard stator current circular signal scatter plot using a Clarke transform; obtain a plurality of three-phase current signals to be tested of the AC motor to be tested, and convert the plurality of three-phase current signals to be tested into an initial stator current circular signal plot to be tested;

[0174] a first determining unit 122 configured to determine an angle between each signal point in the initial to-be-measured sub-current circular signal scatter diagram and a preset direction vector, sort the signal points according to the angle to obtain a target to-be-measured sub-current circular signal scatter diagram; divide the target to-be-measured sub-current circular signal scatter diagram into regions according to a preset angle threshold to obtain a plurality of first scatter regions, and divide the preprocessed standard stator current source signal scatter diagram according to the angle threshold to obtain a plurality of second scatter regions;

[0175] The second determination unit 123 is configured to determine a health assessment parameter based on the first coordinates of each signal point in each of the first scatter point areas and the second coordinates of each signal point in each of the second scatter point areas, determine a health score of the AC motor to be tested based on the health assessment parameter; and evaluate a health status of the AC motor to be tested based on the health score.

[0176] Since the device described in the embodiments of the present invention is used to implement the method for evaluating the health status of a marine AC motor according to the embodiments of the present invention, the specific structure and variations of the device are readily apparent to those skilled in the art based on the methods described in the embodiments of the present invention, and thus will not be further described herein. All devices used in the methods according to the embodiments of the present invention are within the scope of protection of the present invention.

[0177] Based on the same inventive concept, this embodiment provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, any step of the method described above is implemented.

[0178] Based on the same inventive concept, this embodiment provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of any of the above methods are implemented.

[0179] Through one or more embodiments of the present invention, the present invention has the following beneficial effects or advantages:

[0180] The present invention provides a method, device, medium and equipment for evaluating the health status of a marine AC motor. The method comprises the following steps: obtaining a plurality of fault-free three-phase current signals of a normal AC motor, and converting the plurality of fault-free three-phase current signals into a standard stator current circular signal scatter diagram using Clarke transform; obtaining a plurality of three-phase current signals to be measured of the AC motor to be measured, and converting the plurality of three-phase current signals to be measured into an initial stator current circular signal diagram to be measured; determining an angle between each signal point in the initial stator current circular signal scatter diagram and a preset direction vector, and sorting each signal point according to the angle to obtain a target stator current circular signal scatter diagram to be measured; dividing the target stator current circular signal scatter diagram into regions according to a preset angle threshold to obtain a plurality of first scatter point regions, and sorting the preprocessed standard stator current circular signal scatter diagram according to the angle threshold. The stator current source signal scatter plot is divided to obtain multiple second scatter areas; the health assessment parameters are determined according to the first coordinates of each signal point in each of the first scatter areas and the second coordinates of each signal point in each of the second scatter areas; the health score of the AC motor to be tested is determined according to the health assessment parameters; the health status of the AC motor to be tested is evaluated according to the health score; in this way, based on the collected stator current, the Clarke transform is used to convert multiple fault-free three-phase current signals of the normal AC motor into standard stator current circular signal scatter plots, and the multiple three-phase current signals to be tested of the AC motor to be tested are converted into stator current circular signal diagrams to be tested; the health assessment parameters are determined according to the coordinates of each signal point in each scatter area, and the health score of the AC motor is quantified using the health assessment parameters, so that the health status of the motor can be accurately evaluated according to the health score.

[0181] The algorithm and display provided herein are not inherently related to any particular computer, virtual system or other device. Various general-purpose systems can also be used together with the teachings based on this. According to the above description, it is obvious that the structure required for constructing this type of system. In addition, the present invention is not directed to any specific programming language. It should be understood that various programming languages ​​can be utilized to realize the content of the present invention described herein, and the above description of specific languages ​​is for the purpose of disclosing the best mode of the present invention.

[0182] In the description provided herein, numerous specific details are described. However, it is understood that embodiments of the present invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques are not shown in detail so as not to obscure the understanding of this description.

[0183] Similarly, it should be understood that in order to streamline the present disclosure and aid in understanding one or more of the various inventive aspects, in the above description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, this disclosed method should not be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as reflected in the claims below, inventive aspects lie in less than all the features of the individual embodiments disclosed above. Accordingly, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of the invention.

[0184] Those skilled in the art will appreciate that the modules in the devices in the embodiments may be adaptively changed and arranged in one or more devices different from the embodiments. The modules or units or components in the embodiments may be combined into one module or unit or component, and in addition may be divided into multiple submodules or subunits or subcomponents. All features disclosed in this specification (including the accompanying claims, abstracts and drawings) and all processes or units of any method or device disclosed herein may be combined in any combination, except that at least some of such features and / or processes or units are mutually exclusive. Unless expressly stated otherwise, each feature disclosed in this specification (including the accompanying claims, abstracts and drawings) may be replaced by an alternative feature providing the same, equivalent or similar purpose.

[0185] Furthermore, those skilled in the art will appreciate that although some embodiments herein include certain features included in other embodiments but not other features, combinations of features from different embodiments are intended to be within the scope of the present invention and to form different embodiments. For example, in the claims below, any of the claimed embodiments may be used in any combination.

[0186] The various component embodiments of the present invention can be implemented in hardware, or in software modules running on one or more processors, or in a combination thereof. It will be appreciated by those skilled in the art that a microprocessor or digital signal processor (DSP) can be used in practice to implement some or all of the functions of some or all of the components in the gateway, proxy server, or system according to an embodiment of the present invention. The present invention can also be implemented as a device or apparatus program (e.g., a computer program and a computer program product) for executing part or all of the methods described herein. Such a program implementing the present invention can be stored on a computer-readable medium, or can have the form of one or more signals. Such a signal can be downloaded from an Internet website, or provided on a carrier signal, or provided in any other form.

[0187] It should be noted that the above embodiments illustrate rather than limit the invention, and that those skilled in the art may devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between brackets should not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The present invention may be implemented by means of hardware comprising several different elements and by means of appropriately programmed computers. In a unit claim enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third etc. does not indicate any order. These words may be interpreted as names.

[0188] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present application.

[0189] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for evaluating the health status of a marine AC motor, characterized in that: The method comprises: Acquire multiple fault-free three-phase current signals of a normal AC motor, and convert the multiple fault-free three-phase current signals into a standard stator current circular signal scatter plot by using Clarke transformation; Acquire a plurality of three-phase current signals to be measured of the AC motor to be measured, and convert the plurality of three-phase current signals to be measured into a scatter plot of an initial quantum current circular signal to be measured; Determine the angle between each signal point in the initial quantum current circular signal scatter diagram and a preset direction vector, sort each signal point according to the angle, and obtain the target quantum current circular signal scatter diagram; Dividing the target to-be-measured stator current circular signal scatter plot into regions according to a preset angle threshold to obtain a plurality of first scatter plot regions, and dividing the preprocessed standard stator current source signal scatter plot according to the angle threshold to obtain a plurality of second scatter plot regions; Determine a health assessment parameter according to the first coordinates of each signal point in each of the first scattered point areas and the second coordinates of each signal point in each of the second scattered point areas; Determine the health score of the AC motor to be tested according to the health assessment parameter; evaluate the health status of the AC motor to be tested according to the health score; wherein, When the health assessment parameter includes: a center of gravity offset and a radius standard deviation, determining the health assessment parameter according to the first coordinates of each signal point in each of the first scatter point areas and according to the second coordinates of each signal point in each of the second scatter point areas includes: Determine the first center of gravity offset of each first scatter point area and the first radius of each signal point in each first scatter point area according to the first coordinates of each signal point in each first scatter point area; determine the average of each first center of gravity offset as the current center of gravity offset of the circular signal scatter diagram of the target sub-current to be measured; Determine a second gravity center offset of each second scatter point area and a second radius of each signal point in each second scatter point area according to the second coordinates of each signal point in each second scatter point area; determine an average of each of the second gravity center offsets as a reference gravity center offset; Determine each first scatter point area according to the first radius of each signal point in the first scatter point area The first radius standard deviation is determined as the current radius standard deviation of the circular signal scatter diagram of the target to-be-measured electron current; The second radius standard deviation of each second scatter point area is determined according to the second radius of each signal point in each second scatter point area; and the mean of each second radius standard deviation is determined as the reference radius standard deviation of the preprocessed standard stator current circular signal scatter point diagram.

2. The method according to claim 1, characterized in that The determining of the angle between each signal point in the initial to-be-measured quantum current circular signal scatter diagram and a preset direction vector comprises: For a current vector formed by any current signal point and the origin in the circular signal scatter diagram of the initial quantum current to be measured, a modulus value of the current vector is determined according to the coordinates of the current signal point and the coordinates of the origin in the circular signal scatter diagram of the initial quantum current to be measured; Determining the modulus of the preset direction vector; Determining a dot product between the preset direction vector and the current vector; The angle between the current vector and the preset direction vector is determined according to the module of the current vector, the module value of the preset direction vector, and the dot product between the preset direction vector and the current vector.

3. The method according to claim 1, characterized in that When the health assessment parameter includes: a kurtosis value, a skewness value, and a root mean square value, determining the health assessment parameter according to the first coordinates of each signal point in each of the first scatter point areas and according to the second coordinates of each signal point in each of the second scatter point areas includes: Determine the first radius of all signal points in each of the first scattered point areas, and determine the minimum first radius from the first radii of all signal points; Obtaining a distance difference between the first radius of the remaining signal points in each of the first scatter point areas and the minimum first radius; the remaining signal points in the first scatter point area are all signal points in the first scatter point area except the signal point corresponding to the minimum first radius; Based on all the distance difference values ​​in each of the first scatter point areas, determine a kurtosis value, a skewness value, and a root mean square value of the distance difference value in each of the first scatter point areas; Determine the second radius of all signal points in each of the second scattered point areas, and determine the minimum second radius from the second radii of all signal points; Obtaining a distance difference between the second radius of each of the remaining signal points in the second scatter point area and the minimum second radius; the remaining signal points in the second scatter point area are all signal points in the second scatter point area except the signal point corresponding to the minimum second radius; Based on all the distance difference values ​​in each of the second scatter point areas, a kurtosis value, a skewness value and a root mean square value of the distance difference value in each of the second scatter point areas are determined.

4. The method according to claim 1, characterized in that: Determining the health score of the AC motor to be tested according to the health assessment parameter includes: According to the formula Determine a reference evaluation value η of a scatter plot of a preprocessed standard stator current source signal; According to the formula Determine the current evaluation value η′ of the circular signal scatter diagram of the target sub-current to be measured; According to the formula Determine the health score of the AC motor under test in, The R U is the reference radius standard deviation, the R T is the reference center of gravity offset, the R′ U is the current radius standard deviation, the R′ T is the current center of gravity offset, and γ is the reference score corresponding to the scatter diagram of the preprocessed standard stator current source signal.

5. The method according to claim 3, characterized in that Determining the health score of the AC motor to be tested according to the health assessment parameter includes: Constructing a parameter matrix to be measured according to the kurtosis value, the skewness value and the root mean square value of the distance difference value in each of the first scatter point areas; Constructing a reference parameter matrix according to the kurtosis value, the skewness value and the root mean square value of the distance difference value in each of the second scatter point areas; Determining a similarity coefficient between the parameter matrix to be measured and the reference parameter matrix; Based on the formula Determine the health score S of the AC motor to be tested, where n″ is the similarity coefficient.

6. The method according to claim 5, characterized in that The determining of the similarity coefficient between the parameter matrix to be measured and the reference parameter matrix comprises: Determining the covariance between the parameter matrix to be measured and the reference parameter matrix; Determine a first standard deviation of the parameter matrix to be measured and a second standard deviation between the reference parameter matrix; determining a product value between the first standard deviation and the second standard deviation; The similarity coefficient between the parameter matrix to be measured and the reference parameter matrix is ​​determined according to the product value between the covariance, the first standard deviation and the second standard deviation; the similarity coefficient is the quotient value between the covariance and the product value.

7. The method according to claim 3, characterized in that Determining the kurtosis value, the skewness value and the root mean square value of the distance difference value in each first scatter point area includes: According to the formula Determine a kurtosis value x of the distance difference in each first scatter point region; According to the formula Determine a skewness value γ of the distance difference in each first scatter point area; According to the formula Determine the root mean square value X of the distance difference in each first scatter point area rms ;in, N is the number of distance differences in the first scatter point area, i is the sequence number of the distance differences in the first scatter point area, and d i is the i-th distance difference.

8. A device for evaluating the health status of a marine AC motor, characterized in that: The device comprises: The conversion unit is used to obtain multiple fault-free three-phase current signals of the normal AC motor, and use Clarke transformation to convert the multiple fault-free three-phase current signals into a standard stator current circular signal scatter diagram; obtain multiple three-phase current signals to be tested of the AC motor to be tested, and convert the multiple three-phase current signals to be tested into a standard stator current circular signal scatter diagram; Change to the initial circular signal scatter diagram of the current to be measured; a first determination unit, for determining an angle between each signal point in the initial quantum current circular signal scatter diagram and a preset direction vector, and sorting each signal point according to the angle to obtain a target quantum current circular signal scatter diagram; dividing the target quantum current circular signal scatter diagram into regions according to a preset angle threshold to obtain a plurality of first scatter regions, and dividing the preprocessed standard stator current source signal scatter diagram according to the angle threshold to obtain a plurality of second scatter regions; The second determination unit is used to determine a health assessment parameter according to the first coordinates of each signal point in each of the first scatter point areas and the second coordinates of each signal point in each of the second scatter point areas, determine a health score of the AC motor to be tested according to the health assessment parameter; and evaluate the health status of the AC motor to be tested according to the health score; wherein, When the health assessment parameter includes: a center of gravity offset and a radius standard deviation, determining the health assessment parameter according to the first coordinates of each signal point in each of the first scatter point areas and according to the second coordinates of each signal point in each of the second scatter point areas includes: Determine the first center of gravity offset of each first scatter point area and the first radius of each signal point in each first scatter point area according to the first coordinates of each signal point in each first scatter point area; determine the average of each first center of gravity offset as the current center of gravity offset of the circular signal scatter diagram of the target sub-current to be measured; Determine a second gravity center offset of each second scatter point area and a second radius of each signal point in each second scatter point area according to the second coordinates of each signal point in each second scatter point area; determine an average of each of the second gravity center offsets as a reference gravity center offset; Determine the first radius standard deviation of each first scatter point area according to the first radius of each signal point in each first scatter point area; determine the mean of each of the first radius standard deviations as the current radius standard deviation of the circular signal scatter point diagram of the target to-be-measured sub-current; The second radius standard deviation of each second scatter point area is determined according to the second radius of each signal point in each second scatter point area; and the mean of each second radius standard deviation is determined as the reference radius standard deviation of the preprocessed standard stator current circular signal scatter point diagram.

9. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the steps of the method according to any one of claims 1 to 7 are implemented.

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