Method and system for dividing the impact load cutoff frequency of a floating device

Abstract

The application relates to a method and system for dividing the impact load cutoff frequency of a floating device, which comprises the following steps: obtaining the original impact load of the floating device; pre-decomposing the original impact load to obtain a time domain graph; performing variable modal decomposition on the original impact load according to the degree of cutting index K; performing fast Fourier transform on each intrinsic modal function to obtain the frequency spectrum of each intrinsic modal function and the corresponding impact load acceleration amplitude; performing normalization processing on the impact load acceleration amplitude; performing Fourier inverse transform on the low-frequency part to obtain a new impact load. The above scheme provided by the application can greatly reduce the cutoff frequency of the new impact load compared with the original impact load, and the new impact load is closer to the actual impact load suffered by the pipeline in the pipeline impact resistance design of the floating device, so that the anti-impact calculation efficiency of the floating device can be effectively improved on the premise of ensuring the accuracy of the calculation result.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mechanical engineering, in particular to a method and system for dividing impact load cutoff frequency of a floating device. BACKGROUND

[0002] There are mainly two forms of offshore wind power devices: fixed type and floating type. The floating device refers to a foundation platform which is not in direct contact with the seabed, but is connected to the seabed through a floating platform and a mooring system. The wind turbine generator set freely floats and moves within the local area control range of the floating platform. Different floating platform forms can adapt to different marine environments.

[0003] The floating device can provide sufficient electric power and thermal energy and fresh water supply for offshore resource exploitation, island resident life and production activities, and lay a solid energy foundation for the development activities in the surrounding sea area. At the same time, the floating device has great development potential. Relying on small floating devices to supply energy for remote islands will be a new development trend for marine powers in the future. However, the influence of earthquake events needs to be considered for land power generation devices, and similarly, the floating device is more susceptible to impact response caused by collisions with other ships. Therefore, the safety of the pipeline system of the floating device after the collision is an important factor for the floating device. At the same time, due to the particularity of the floating device, the platform engineering layout space is very compact, and the adjustable space is very limited. If it is not analyzed and optimized, the excessively high cutoff frequency will bring great design difficulties to the subsequent design work. Therefore, it is necessary to analyze the impact response of the platform, give a reasonable cutoff frequency determination method, and optimize and reconstruct the impact load. SUMMARY

[0004] Based on this, the present application provides a method and system for dividing impact load cutoff frequency of a floating device, so as to facilitate the analysis of the impact response of the platform, give a reasonable cutoff frequency determination method, and optimize and reconstruct the impact load.

[0005] The present application provides a method for dividing impact load cutoff frequency of a floating device, which comprises: obtaining an original impact load of the floating device;

[0006] The original impact load is pre-decomposed to obtain a time domain graph, and a degree of curvature index K is selected according to the curvature change of the mean instantaneous frequency in the time domain graph;

[0007] The original impact load is decomposed according to the degree of curvature index K to obtain K-1 groups of intrinsic mode functions, wherein K-1 is the number of decomposition layers;

[0008] The fast Fourier transform is performed on each intrinsic mode function to obtain the frequency spectrum of each intrinsic mode function and the corresponding impact load acceleration amplitude;

[0009] normalizing the impact load acceleration amplitude, wherein the normalized acceleration amplitude less than 0.01 is high frequency, and the normalized acceleration amplitude greater than 0.01 is low frequency;

[0010] performing Fourier inverse transform on the low frequency part to obtain a new impact load.

[0011] the impact load cutoff frequency division method of the floating device,

[0012] The new impact load obtained by the original impact load after the corresponding transformation is compared with the original impact load, and the cutoff frequency is greatly reduced. The new impact load is more close to the actual impact load suffered by the pipeline in the pipeline impact resistance design of the floating device, and can effectively improve the impact resistance calculation efficiency of the floating device under the premise of ensuring the accuracy of the calculation result.

[0013] In one embodiment, the pre-decomposition of the original impact load to obtain a time domain graph includes: pre-decomposing the original impact load to obtain a time domain graph by a VMD algorithm.

[0014] In one embodiment, the selection of the degree of cutting index K according to the curvature change of the instantaneous frequency mean in the time domain graph includes:

[0015] calculating each slope corresponding to each instantaneous frequency mean in the time domain graph;

[0016] When the difference between the adjacent two slopes exceeds a preset value, the larger value of the adjacent two slopes is selected as the degree of cutting index K.

[0017] In one embodiment, the selection of the larger value of the adjacent two slopes as the degree of cutting index K includes:

[0018] determining whether the larger value of the slope is an integer, if it is an integer, the degree of cutting index K is equal to the larger value of the slope; if it is a decimal, the degree of cutting index K is the value after removing the decimal point.

[0019] In one embodiment, the variational mode decomposition of the original impact load according to the degree of cutting index K includes:

[0020] The original impact load is decomposed by a VMD algorithm according to the degree of cutting index K.

[0021] In one embodiment, the Fourier inverse transform of the low frequency part to obtain a new impact load includes:

[0022] Each eigenmode function with a normalized impact load acceleration amplitude greater than 0.01 is used to reconstruct the impact load.

[0023] In one of the embodiments, after the inverse Fourier transform of the low frequency part is performed to obtain the new impact load, the method further comprises:

[0024] applying the new impact load to each pipe support and hanger in the floating device;

[0025] performing transient analysis on each pipe support and hanger by using the finite element method to obtain the dynamic response of each pipe support and hanger;

[0026] redesigning each pipe support and hanger according to the dynamic response.

[0027] In one of the embodiments, the redesigning each pipe support and hanger according to the dynamic response comprises:

[0028] redesigning the spatial arrangement structure of each pipe support and hanger according to the dynamic response.

[0029] In one of the embodiments, the obtaining the original impact load of the floating device comprises: obtaining the original impact load according to the preset acting force applied to the floating device in the initial design.

[0030] The application further provides an impact load cutoff frequency division system of a floating device, which comprises:

[0031] an obtaining unit configured to obtain an original impact load of the floating device;

[0032] a first decomposition unit configured to perform pre-decomposition on the original impact load to obtain a time domain graph, and select a kurtosis index K according to the curvature change of the mean instantaneous frequency in the time domain graph;

[0033] a second decomposition unit configured to perform variational modal decomposition on the original impact load according to the kurtosis index K to obtain K-1 groups of intrinsic modal functions, wherein K-1 is the number of decomposition layers;

[0034] a transforming unit configured to perform fast Fourier transform on each intrinsic modal function to obtain the frequency spectrum of each intrinsic modal function and the corresponding impact load acceleration amplitude;

[0035] a processing unit configured to perform normalization processing on the impact load acceleration amplitude, wherein the normalized acceleration amplitude less than 0.01 is high frequency, and the normalized acceleration amplitude greater than 0.01 is low frequency;

[0036] an inverse transforming unit configured to perform inverse Fourier transform on the low frequency part to obtain a new impact load. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1A schematic diagram of the impact load cutoff frequency division method of the floating device provided in an embodiment of the present application;

[0038] Figure 2 A schematic diagram of the original impact load along the X-axis direction;

[0039] Figure 3 A schematic diagram of the original impact load along the Y-axis direction;

[0040] Figure 4 A schematic diagram of the original impact load along the Z-axis direction;

[0041] Figure 5 A schematic diagram of the X-axis direction of the time history curve of the impact load received by the pipeline in the floating device;

[0042] Figure 6 A schematic diagram of the Y-axis direction of the time history curve of the impact load received by the pipeline in the floating device;

[0043] Figure 7 A schematic diagram of the Z-axis direction of the time history curve of the impact load received by the pipeline in the floating device;

[0044] Figure 8 A schematic diagram of the pipeline system finite element model of the platform part of the floating device;

[0045] Figure 9 A schematic diagram of the dynamic response along the X-axis direction of the model in Figure 8 after receiving each impact load;

[0046] Figure 10 A schematic diagram of the dynamic response along the Y-axis direction of the model in Figure 8 after receiving each impact load;

[0047] Figure 11 A schematic diagram of the dynamic response along the Z-axis direction of the model in Figure 8 after receiving each impact load;

[0048] Figure 12 A schematic diagram of the stress response envelope of the PART1-E1 unit in Figure 8 based on impact loads with different cutoff frequencies. DETAILED DESCRIPTION

[0049] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. In the following description, a large number of specific details are set forth in order to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the spirit of the present application, so the present application is not limited to the specific embodiments disclosed below.

[0050] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0051] In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise explicitly specified and limited.

[0052] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting", "fixing" and the like should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0053] In the present application, unless otherwise explicitly specified and limited, the first feature is "on" or "under" the second feature, which can be direct contact between the first and second features, or indirect contact between the first and second features through an intermediate medium. Moreover, the first feature "above", "above" and "above" the second feature can be directly above or obliquely above the first feature, or only indicate that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "below" and "below" the second feature can be directly below or obliquely below the first feature, or only indicate that the horizontal height of the first feature is less than that of the second feature.

[0054] It is to be understood that when an element such as a layer, region or substrate is referred to as being "on" or "connected to" another element, it can be directly on or connected to the other element or intervening elements can be present. In contrast, when an element is referred to as being "directly on" or "directly connected to" another element, there are no intervening elements present. It will be understood that, when a part is referred to as being "formed on" or "formed on" another part, it can be directly on the other part or there can be an intervening part. It will be understood that the terms "vertical", "horizontal", "upper", "lower", "left", "right", and similar expressions are used for explanation only and are not intended to be limiting.

[0055] As shown in the embodiment of the present application, a method for dividing the impact load cutoff frequency of a floating device is provided, and the method comprises the following steps: Figure 1

[0056] Step S101: obtaining an original impact load of the floating device; specifically, the original impact load can be obtained according to a preset force applied to the floating device in the initial design, and the preset force is selected by the designer according to the experience value.

[0057] Step S102: pre-decomposing the original impact load to obtain a time-domain graph, and selecting a degree of curvature index K according to the curvature change of the instantaneous frequency mean in the time-domain graph;

[0058] Step S103: performing variational modal decomposition on the original impact load according to the degree of curvature index K to obtain K-1 groups of intrinsic mode functions, wherein K-1 is the number of decomposition layers;

[0059] Step S104: performing fast Fourier transform on each intrinsic mode function to obtain the frequency spectrum of each intrinsic mode function and the corresponding impact load acceleration amplitude;

[0060] Step S105: performing normalization processing on the impact load acceleration amplitude, wherein the normalized acceleration amplitude less than 0.01 is high frequency, and the normalized acceleration amplitude greater than 0.01 is low frequency;

[0061] Step S106: performing inverse Fourier transform on the low frequency part to obtain a new impact load.

[0062] The original impact load can obtain a new impact load after corresponding transformation, and the new impact load has a significantly reduced cutoff frequency compared with the original impact load. The new impact load is more close to the actual impact load suffered by the pipeline in the impact resistance design of the pipeline of the floating device, and can effectively improve the impact resistance calculation efficiency of the floating device under the premise of ensuring the accuracy of the calculation result.

[0063] ​In some embodiments, the pre-decomposition of the original impact load in step S102 obtains a time-domain graph: the original impact load is pre-decomposed by a VMD algorithm to obtain a time-domain graph. Since the specific principle of pre-decomposing the original impact load by the VMD algorithm is prior art, it will not be repeated here.

[0064] The VMD (Variational mode decomposition) in the embodiment is a self-adaptive, completely non-recursive mode variation and signal processing method. The technology has the advantage of being able to determine the number of mode decompositions. Its adaptability is reflected in determining the number of mode decompositions of a given sequence according to actual conditions, adaptively matching the best center frequency and limited bandwidth of each mode in the subsequent search and solution process, and realizing effective separation of intrinsic mode components (IMF), frequency domain division of signals, and further obtaining effective decomposition components of the given signal, and finally obtaining the optimal solution of the variation problem.

[0065] In some embodiments, according to the curvature change of the instantaneous frequency mean in the time-domain graph, the degree of cutting index K is selected, including: calculating each slope corresponding to each instantaneous frequency mean in the time-domain graph; when the difference between the adjacent two slopes exceeds a preset value, the larger value of the adjacent two slopes is selected as the degree of cutting index K.

[0066] Further, the above selecting the larger value of the adjacent two slopes as the degree of cutting index K includes: judging whether the larger value is an integer, if it is an integer, the degree of cutting index K is equal to the larger value; if it is a decimal, the degree of cutting index K is the value after removing the decimal point.

[0067] Since the selection of K is crucial in the VMD algorithm. For example, if the K value is too large or too small in the K value selection process, it will cause over-decomposition or under-decomposition in the signal decomposition process, and then affect the reconstruction of the impact load. Therefore, by observing the change of the instantaneous frequency mean represented by different K values, it can be judged whether the VMD decomposition is in an over-decomposition or under-decomposition state under different K value selection, so as to select an appropriate K value to ensure that the VMD decomposition is in a reasonable state.

[0068] In the selection of K value in the present application, first, the slopes corresponding to each instantaneous frequency mean in the time-domain graph are calculated, and when the difference between the adjacent two slopes exceeds a preset value, the slope suddenly becomes large at this time, and the slope suddenly becomes large at this time. The value of K can be obtained.

[0069] In some embodiments, the original impact load is decomposed by a VMD algorithm according to the degree of cutting index K, including: decomposing the original impact load by a VMD algorithm according to the degree of cutting index K.

[0070] In some embodiments, after the Fourier inverse transform of the low frequency part is performed to obtain the new impact load, the method further comprises:

[0071] applying the new impact load to each pipe support and hanger in the floating device;

[0072] performing transient analysis on each pipe support and hanger using the finite element method to obtain the dynamic response of each pipe support and hanger;

[0073] redesigning each pipe support and hanger according to the dynamic response, i.e., redesigning the spatial arrangement structure of each pipe support and hanger according to the dynamic response.

[0074] The redesigned floating device can reduce the impact of other ship collisions, thereby improving the safety performance of the floating device.

[0075] For example, the present application needs to select the degree of cutting index before VMD decomposition, analyze the original impact load signal based on the instantaneous frequency mean method, as shown in Figure 2 , Figure 3 and Figure 4 the schematic diagram of the original impact load along the X, Y, Z axis direction, then process the original impact load to obtain the corresponding impact load time history curve X axis, Y axis and Z axis direction curve change diagram as shown in Figure 5 , Figure 6 and Figure 7 .

[0076] In this preprocessing stage, the K value is selected as 30, from Figure 5 it can be seen that for the impact load in the X direction, the frequency mean presents obvious curve change when K=15, so the K value is selected as 14, i.e., the original signal in the X direction is decomposed into 14 modal components. Similarly, referring to Figure 6 and Figure 7 , for the impact load in the Y and Z directions, the K values are selected as 16 and 9 respectively, and the impact load in the Y and Z directions is decomposed.

[0077] The characteristic frequency and maximum acceleration amplitude of each main component of the impact load in the X, Y and Z directions are shown in the following table:

[0078] Table 1 shows the characteristic frequency and maximum impact load of each eigenmode function in the X direction

[0079]

[0080] Table 2 shows the characteristic frequency and maximum impact load of each eigenmode function in the Y direction

[0081]

[0082] Table 3 Characteristic frequency and maximum impact load of each eigenmode function in Z direction

[0083]

[0084] From the results of Tables 1-3, it can be seen that the characteristic frequencies of the impact load obtained by the VMD method are arranged from high to low, and the acceleration amplitude of each component corresponding to the characteristic frequency is normalized by the maximum acceleration amplitude of each component corresponding to the characteristic frequency.

[0085] Subsequently, the dynamic response analysis of the impact load of the piping system was performed, and a part of the piping system of a certain floating device platform was taken as the research object. A finite element model was established based on ABAQUS, as shown in Figure 8 .

[0086] The normalized impact load acceleration amplitude was used as the basis for dividing the cutoff frequency. The eigenmode functions with a normalized impact load acceleration amplitude greater than 0.01 were used to reconstruct the impact load, and the reconstructed impact load with a cutoff coefficient of 0.01 was obtained. Similarly, the eigenmode functions with a normalized impact load acceleration amplitude greater than 0.2 were used to reconstruct the impact load, and the reconstructed impact load with a cutoff coefficient of 0.2 was obtained.

[0087] Table 4 Impact load cutoff frequency corresponding to different cutoff coefficients

[0088]

[0089] Table 4 is the cutoff frequency of each impact load in X, Y, and Z directions when the cutoff coefficient is selected as 0.01 and 0.2. From Table 4, it can be found that when the cutoff coefficient is selected as 0.01, the cutoff frequency can be significantly reduced, and when the cutoff coefficient is selected as 0.2, the cutoff frequency can be more significantly reduced, only about 38% of the original impact load cutoff frequency.

[0090] At this time, the original impact load and the impact load reconstructed based on VMD are respectively applied to each pipe support and hanger, and the transient analysis is performed using ABAQUS software, as shown in Figure 9 , Figure 10 and Figure 11 , the dynamic response of the pipe under the action of the impact load can be numerically simulated.

[0091] Figure 11 , the acceleration response envelope of PART1-N1 node based on impact load with different cutoff frequencies. Figure 12 , the stress response envelope of PART1-E1 unit based on impact load with different cutoff frequencies. From Figure 11 and Figure 12 It can be found that when the cutoff coefficient is 0.01, the reconstructed impact load based on VMD is basically consistent with the original impact load in XYZ acceleration response and stress response. When the cutoff coefficient is 0.2, the reconstructed impact load based on VMD basically maintains the same trend as the original impact load in XYZ acceleration response, but there is a certain gap, especially in the Y direction of the acceleration response and the stress response, which is more obvious than when the cutoff coefficient is 0.01.

[0092] It is found through numerical simulation that when the cutoff coefficient is 0.01, the calculation accuracy of the pipe system impact response can be guaranteed. When the cutoff frequency is 0.2, although there is a certain gap between the optimized reconstructed impact response and the original impact load, the pipe system impact response can be guaranteed to have the same trend. However, considering the particularity of the application site, the dynamic response accuracy of the reconstructed impact load should be guaranteed from a more conservative point of view. Therefore, the cutoff coefficient of 0.01 is more suitable. In actual engineering problems, if the impact response caused by the original impact load has a large safety margin, a larger cutoff coefficient can be selected to obtain a lower cutoff frequency for subsequent design work.

[0093] The application also provides an impact load cutoff frequency division system of a floating device, which comprises: an acquisition unit configured to acquire an original impact load of the floating device; a first decomposition unit configured to pre-decompose the original impact load to obtain a time-domain graph, and select a cutting degree index K according to the curvature change of the mean instantaneous frequency in the time-domain graph; a second decomposition unit configured to perform variational mode decomposition on the original impact load according to the cutting degree index K to obtain K-1 groups of intrinsic mode functions; a transformation unit configured to perform fast Fourier transform on each intrinsic mode function to obtain the frequency spectrum of each intrinsic mode function and the corresponding impact load acceleration amplitude; a processing unit configured to normalize the impact load acceleration amplitude, wherein the acceleration amplitude less than 0.01 is high frequency, and the acceleration amplitude greater than 0.01 is low frequency; and an inverse transformation unit configured to perform inverse Fourier transform on the low frequency part to obtain a new impact load. Since the system corresponds to the above method, it will not be repeated here.

[0094] The technical features of the above-described embodiments can be combined in any manner. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described, but as long as the combinations of the technical features do not exist contradictions, they should be considered as the scope of the present disclosure.

[0095] The above embodiments only express several implementation ways of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation to the patent scope of the application. It should be pointed out that for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, which all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for dividing the impact load cutoff frequency of a floating device, characterized in that: The method includes: Obtain the original impact load of the floating device; The original impact load is pre-decomposed to obtain a bandwidth-limited sub-signal, and a relationship diagram between the instantaneous frequency mean of the bandwidth-limited sub-signal component and K is obtained from the bandwidth-limited sub-signal, wherein the X-axis of the relationship diagram is K and the Y-axis is the instantaneous frequency mean; wherein K is a tapering index; wherein the step of pre-decomposing the original impact load to obtain the bandwidth-limited sub-signal includes: pre-decomposing the original impact load using a VMD algorithm to obtain the bandwidth-limited sub-signal; Selecting a taper index K based on a curvature change of the instantaneous frequency mean in the relationship graph; including calculating each slope corresponding to each instantaneous frequency mean in the relationship graph; when a difference between two adjacent slopes exceeds a preset value, selecting the larger value of the two adjacent slopes as the taper index K, wherein determining whether the larger value is an integer; if it is an integer, the taper index K is equal to the larger value; if it is a decimal, the taper index K is the value without the decimal point; Performing variational modal decomposition on the original impact load according to the tapering index K to obtain K-1 groups of eigenmode functions, where K-1 is the number of decomposition layers; comprising: performing variational modal decomposition on the original impact load using a VMD algorithm according to the tapering index K; Perform fast Fourier transform on each eigenmode function to obtain the spectrum of each eigenmode function and the corresponding impact load acceleration amplitude; Normalizing the acceleration amplitude of the impact load, wherein the acceleration amplitude after normalization is less than 0.01 and the acceleration amplitude after normalization is greater than 0.01 and the acceleration amplitude is low-frequency; Perform inverse Fourier transform on the low-frequency part to obtain a new impact load.

2. The method for dividing the impact load cut-off frequency of a floating device according to claim 1, characterized in that: The inverse Fourier transform of the low-frequency part is performed to obtain a new impact load, including: The eigenmode functions with normalized impact load acceleration amplitude greater than 0.01 are used to reconstruct the impact load.

3. The method for dividing the impact load cut-off frequency of a floating device according to claim 1, characterized in that: After performing inverse Fourier transform on the low-frequency portion to obtain a new impact load, the method further includes: Apply new impact loads to each pipe support and hanger in the floating device; The finite element method is used to conduct transient analysis on each pipe support and hanger to obtain the dynamic response of each pipe support and hanger; Each pipe support and hanger is redesigned based on the dynamic response.

4. The method for dividing the impact load cut-off frequency of a floating device according to claim 3, characterized in that: The redesign of each pipe support and hanger according to the dynamic response includes: The spatial arrangement structure of each pipe support and hanger is redesigned according to the dynamic response.

5. The method for dividing the impact load cut-off frequency of a floating device according to claim 1, characterized in that: The obtaining of the original impact load of the floating device comprises: The original impact load is obtained according to the preset force applied to the floating device in the initial design.

6. A system for dividing the impact load cutoff frequency of a floating device, characterized in that: The system includes: an acquisition unit, used for acquiring an original impact load of the floating device; The first decomposition unit is used to pre-decompose the original impact load to obtain a bandwidth-limited sub-signal, so that the bandwidth-limited sub-signal obtains a relationship diagram of the instantaneous frequency mean of the bandwidth-limited sub-signal component and K, wherein the X-axis in the relationship diagram is K and the Y-axis is the instantaneous frequency mean; wherein K is a taper index; wherein the step of pre-decomposing the original impact load to obtain a bandwidth-limited sub-signal includes: pre-decomposing the original impact load by a VMD algorithm to obtain a bandwidth-limited sub-signal; selecting the taper index K according to the curvature change of the instantaneous frequency mean in the relationship diagram; including: calculating each slope corresponding to each instantaneous frequency mean in the relationship diagram; when the difference between two adjacent slopes exceeds a preset value, selecting the value with the larger slope among the two adjacent slopes as the taper index K, wherein it is judged whether the value with the larger slope is an integer. If it is an integer, the taper index K is equal to the value with the larger slope; if it is a decimal, the taper index K is the value without the decimal point; A second decomposition unit is configured to perform variational modal decomposition on the original impact load according to the tapering index K to obtain K-1 groups of intrinsic mode functions, where K-1 is the number of decomposition levels; the second decomposition unit includes performing variational modal decomposition on the original impact load according to the tapering index K using a VMD algorithm; A transformation unit, configured to perform a fast Fourier transform on each intrinsic mode function to obtain a frequency spectrum of each intrinsic mode function and a corresponding impact load acceleration amplitude; a processing unit, configured to normalize the acceleration amplitude of the impact load, wherein an acceleration amplitude less than 0.01 after normalization is considered high frequency, and an acceleration amplitude greater than 0.01 after normalization is considered low frequency; The inverse transform unit is used to perform inverse Fourier transform on the low-frequency part to obtain a new impact load.

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