A non-steady-state excitation damping performance evaluation method

Abstract

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Description

Technical Field

[0001] This invention relates to the field of ship vibration reduction performance evaluation technology, and in particular to a method for evaluating vibration reduction performance under unsteady excitation. Background Technology

[0002] As the core power equipment of a ship, the vibration characteristics of the main engine directly affect the ship's operational safety, structural fatigue life, and crew comfort. Marine diesel engines, as complex power systems with multiple moving parts and multi-layered combinations, generate typical unsteady-state vibration signals under the influence of uncertain boundaries and unstable operating conditions. Especially during the start-up and shutdown of the main engine, the engine speed changes drastically in a short period, and the system is in a transient transition state, with its excitation characteristics and vibration response significantly different from those during steady-state operation. However, in the field of vibration reduction effect evaluation, existing technologies generally treat the vibration signals during the start-up and shutdown process as interference or outliers and discard them, or simply include them in the overall time-period averaging, failing to conduct targeted vibration reduction effect assessments for this specific unsteady excitation period. In other words, existing technologies lack a method that can specifically evaluate the vibration acceleration signals before and after vibration reduction during the unsteady excitation period of the main engine's start-up and shutdown. Summary of the Invention

[0003] In order to overcome the above-mentioned problems in the prior art, the present invention proposes a method for evaluating the vibration reduction performance of unsteady excitation.

[0004] The technical solution adopted by this invention to solve its technical problem is: a method for evaluating the vibration reduction performance of unsteady-state excitation, comprising the following steps: Step 1: Install vibration sensors on the ship being evaluated and collect vibration signals of the evaluated object before and after vibration reduction under unsteady excitation. Step 2: Determine the start and end times of the unsteady-state excitation based on the amplitude changes of the vibration signals before and after vibration reduction or based on the rotational speed changes of the ship being evaluated. Step 3: During the unsteady excitation time period obtained in Step 2, calculate the time-domain characteristic quantities of the vibration signal before vibration reduction and the vibration signal after vibration reduction, and calculate the time-domain vibration level drop based on the time-domain characteristic quantities; Step 4: Within the time period corresponding to the unsteady excitation obtained in Step 2, perform frequency domain analysis on the vibration signals before and after vibration reduction, and calculate the frequency domain vibration level difference before and after vibration reduction; Step 5: Calculate the comprehensive evaluation value based on the time-domain vibration level difference obtained in Step 3 and the frequency-domain vibration level difference obtained in Step 4, and evaluate the vibration reduction performance under unsteady excitation based on the comparison result between the comprehensive evaluation value and the preset evaluation threshold.

[0005] The above-mentioned method for evaluating vibration reduction performance under unsteady excitation, wherein the ship being evaluated in step 1 includes the ship's main engine, auxiliary machinery, pump set, gearbox, shaft support structure, vibration isolation device, or hull structure connected to the power machinery; the unsteady excitation includes vibration excitation generated during the start-up, shutdown, speed increase, speed decrease, operating condition switching, or speed change of the ship's power machinery.

[0006] In the above-mentioned method for evaluating the vibration reduction performance under unsteady excitation, step 2 specifically involves: when the amplitude of the vibration signal before or after vibration reduction exceeds a preset amplitude threshold, or when the rate of change of the rotational speed of the ship being evaluated is greater than a preset rate of change of rotational speed threshold, the corresponding moment is determined as the start moment of the unsteady excitation; when the amplitude is less than or equal to the preset amplitude threshold or the rate of change of rotational speed is lower than the preset rate of change of rotational speed threshold and continues for a preset time, the corresponding moment is determined as the end moment of the unsteady excitation.

[0007] In the above-mentioned method for evaluating vibration reduction performance under unsteady excitation, the time-domain characteristic quantity in step 3 includes at least one of effective value and peak value, and the time-domain vibration level difference includes at least one of root mean square vibration level difference and peak vibration level difference.

[0008] In the above-mentioned method for evaluating vibration reduction performance under unsteady excitation, step 3 specifically includes: Step 3.1, during the non-steady-state excitation period Within, the vibration acceleration signals before vibration reduction were extracted respectively. Vibration acceleration signal after vibration reduction ; Step 3.2, calculate the effective acceleration value before vibration reduction: ; Step 3.3, calculate the effective acceleration value after vibration reduction: ; Step 3.4, calculate the time-domain vibration level before and after vibration reduction: ; in, For reference acceleration values, The time-domain vibration level corresponding to the vibration signal before vibration reduction. This represents the time-domain vibration level corresponding to the vibration signal after vibration reduction. Step 3.5, calculate the time-domain vibration level drop as follows: .

[0009] The above-mentioned method for evaluating the vibration reduction performance under unsteady excitation includes, in step 4, frequency domain analysis including at least one of fast Fourier transform, short-time Fourier transform, piecewise Fourier transform, octave band analysis, or power spectral density analysis; the preset frequency band corresponding to the frequency domain vibration level drop includes at least one of low-frequency band, mid-frequency band, high-frequency band, and octave band.

[0010] In the above-mentioned method for evaluating vibration reduction performance under unsteady excitation, the specific calculation process of the frequency domain vibration level drop in step 4 is as follows: in, For the first Frequency domain vibration levels within a preset frequency band For the first Effective acceleration values ​​within a preset frequency band For reference acceleration values, For the first Frequency domain vibration level drop within a preset frequency band The vibration signal before vibration reduction is at the first Frequency domain vibration levels within a preset frequency band The vibration signal after vibration reduction is at the first... Frequency domain vibration level within a preset frequency band.

[0011] In the above-described method for evaluating vibration reduction performance under unsteady excitation, the comprehensive evaluation value E in step 5 is: in, and Let be the weighting coefficients, and satisfy: ; This is the weighted average of the frequency domain vibration level differences; For the first Frequency domain vibration level drop within a preset frequency band For the first Weighting coefficients for a preset frequency band To preset the number of frequency bands, This represents the time-domain vibration level difference.

[0012] The beneficial effects of this invention are that it breaks through the limitations of existing standards and technical practices, which are only applicable to steady-state or quasi-steady-state operating conditions. For the first time, it establishes a dedicated vibration reduction effect evaluation path for the non-steady-state vibration excitation during the start-up and shutdown of ship main engines. By identifying and locking onto the transient time periods of drastic speed changes, it transforms previously ignored or excluded start-up and shutdown signals into effective evaluation objects, filling the technical gap in the quantitative assessment of vibration reduction performance under this specific operating condition.

[0013] This invention overcomes the information loss defects of traditional full-time average vibration level evaluation methods. Key non-steady-state characteristics such as instantaneous high-energy impacts and frequency drift during start-up and shutdown are easily obscured in full-time averaging, leading to a severe underestimation or misjudgment of the true performance of the vibration damping device under transient conditions. This invention, by precisely locking onto the non-steady-state excitation time period, preserves the time-varying details of the vibration signal, enabling the evaluation results to truly reflect the actual vibration isolation capability of the vibration damping system under transient impacts.

[0014] This invention breaks through the reliance on steady-state frequency response functions or single transmission force indicators, introducing a comprehensive evaluation mechanism of time-domain and frequency-domain vibration level differences. The time-domain vibration level difference directly reflects the overall attenuation effect of the vibration reduction device on vibration amplitude during transient processes, while the frequency-domain vibration level difference can finely characterize the differences in vibration isolation characteristics of different frequency components during start-up and shutdown, especially the response to transient frequency drift and energy distribution changes. The synergistic evaluation of these two aspects ensures both quantifiable comparison of the overall effect and refined analysis of spectral characteristics, significantly improving the comprehensiveness and accuracy of the evaluation results.

[0015] In summary, this invention effectively overcomes the shortcomings of existing technologies, which are only applicable to steady-state conditions, ignore unsteady-state excitations during start-up and shutdown, and lack comprehensive time-frequency domain evaluation methods. It achieves accurate and comprehensive evaluation of vibration reduction effects during the start-up and shutdown of ship main engines, and has important engineering practical value for improving the vibration isolation design and operation and maintenance level of ship power systems. Attached Figure Description

[0016] Figure 1 This is a flowchart of the non-steady-state excitation vibration reduction performance evaluation method of the present invention; Figure 2 This is a schematic diagram illustrating the determination of the non-steady-state excitation time period in an embodiment of the present invention; Figure 3 This is a flowchart of the time-domain vibration level drop calculation for this invention; Figure 4 This is a flowchart illustrating the calculation of frequency domain vibration level drop and comprehensive evaluation value in this invention. Figure 5 This is a schematic diagram comparing the vibration acceleration signals before and after vibration reduction according to the present invention. Detailed Implementation

[0017] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0018] This embodiment discloses a method for evaluating vibration reduction performance under unsteady excitation, such as... Figure 1 As shown, the specific steps include the following: Step 1, Test Object and Signal Acquisition (1) Take the ship's main engine vibration isolation system or the local structure of the hull as the object of evaluation, and arrange vibration sensors at the key measuring points of the object of evaluation.

[0019] (2) Before implementing vibration reduction measures, collect vibration signals during the start-up and shutdown process of the ship's main engine and record them as vibration acceleration signals before vibration reduction. .

[0020] In this embodiment, the vibration acceleration signal acquired before vibration reduction is the measured signal during the start-up and shutdown process of the ship's main engine from 0 to 3000 to 0 rpm, and the sampling time is [missing information]. The sampling interval is The sampling frequency is .

[0021] (3) After the vibration reduction measures are implemented, the vibration signal is collected again at the same measuring point, the same sampling frequency and the same start-stop conditions, and recorded as the acceleration vibration signal after vibration reduction. .

[0022] Step 2, Determining the non-steady-state excitation time period Collect ship main engine speed signal Calculate the rate of change of rotational speed: in, For the first Rotational speed values ​​at each sampling time. This represents the time interval between adjacent sampling points.

[0023] When the rate of change of rotational speed| | Greater than the preset speed change rate threshold When the time is determined, the corresponding moment is identified as the start time of the unsteady-state excitation. When the rate of change of rotational speed | | Less than or equal to the preset speed change rate threshold and continue for a preset time. Then, the corresponding time is determined to be the end time of the unsteady-state excitation. .

[0024] In this embodiment, the ship's main engine speed is determined by... Accelerate to Then by slow down to Among them, the former The acceleration phase is followed by a deceleration phase, such as... Figure 2 As shown. Therefore, the acceleration unsteady-state excitation time period is determined as: ; The deceleration unsteady-state excitation time period is defined as: ; If the entire start-up and shutdown process is evaluated comprehensively, the total time period of non-steady-state excitation is: ; The average speed change rate during the acceleration phase is: ; The average speed change rate during the deceleration phase is: .

[0025] Since this invention uses the absolute value of the rate of change of rotational speed to determine the unsteady excitation process, the absolute value of the rate of change of rotational speed during the deceleration phase is: .

[0026] When the preset speed change rate threshold Pick At that time, both the acceleration and deceleration phases meet the requirements. Therefore, all of these belong to the non-steady-state excitation time period.

[0027] Step 3, Time-domain vibration level difference calculation, such as Figure 3 As shown.

[0028] (1) During the non-steady-state excitation period Within, the vibration acceleration signals before vibration reduction were extracted respectively. Vibration acceleration signal after vibration reduction .

[0029] (2) Calculate the effective acceleration value before vibration reduction: ; (3) Calculate the effective acceleration value after vibration reduction: ; Calculate the time-domain vibration level before and after vibration reduction: ; in, For reference acceleration values, in accordance with the explicit provisions of my country's "Environmental Protection Design Code for Machinery Industry", in this embodiment, the reference acceleration value can be taken as... .

[0030] The time-domain vibration level difference is: ; when When the vibration level is lower than before the vibration reduction, it indicates that the vibration reduction measures have a vibration reduction effect during the non-steady-state start-up and shutdown process.

[0031] In this embodiment, the same bandpass filtering process is applied to both the vibration acceleration signals before and after vibration reduction. The filtering range is 10–100 Hz, the sampling frequency is 2000 Hz, and the filter order is 256. Calculations show that the vibration acceleration signal before vibration reduction in the acceleration phase… The effective acceleration value within is: ; The corresponding time-domain vibration level before vibration reduction is: ; During the deceleration phase Inside, the effective acceleration value before vibration reduction is: ; The corresponding time-domain vibration level before vibration reduction is: ; If the entire start-stop process is considered... For evaluation, the effective acceleration value before vibration reduction is: ; The corresponding time-domain vibration level before vibration reduction is: ; During the acceleration phase Internally, the effective acceleration value after vibration reduction is: ; The corresponding time-domain vibration level after vibration reduction is: ; Therefore, the time-domain vibration level drop during the acceleration phase is: ; During the deceleration phase Internally, the effective acceleration value after vibration reduction is: ; The corresponding time-domain vibration level after vibration reduction is: ; Therefore, the time-domain vibration level drop during the deceleration phase is: .

[0032] If the entire start-stop process is considered... The effective acceleration value after vibration reduction is as follows: ; The corresponding time-domain vibration level after vibration reduction is: ; Therefore, the time-domain vibration level drop during the entire start-up and shutdown process is: .

[0033] Step 4, frequency domain vibration level difference calculation, such as Figure 4 As shown.

[0034] (1) During the non-steady-state excitation period, frequency domain analysis is performed on the vibration acceleration signals before and after vibration reduction. Since the rotational speed and excitation frequency change with time during the start-up and shutdown process, short-time Fourier transform is used to analyze the signals. The frequency domain analysis includes at least one of fast Fourier transform, short-time Fourier transform, piecewise Fourier transform, octave band analysis, or one-third octave band analysis.

[0035] In this embodiment, since the signal has already undergone bandpass filtering in the 10–100 Hz range, the frequency domain evaluation mainly focuses on analyzing the vibration components within the 10–100 Hz frequency band. The maximum speed of the ship's main engine is... The corresponding host frequency conversion is: ; Therefore, the following preset frequency bands can be selected for frequency domain analysis: , , .in, The frequency band corresponds to the frequency change segment of the host machine. The frequency band corresponds to the frequency band near the second harmonic.

[0036] (2) Let the first Within a preset frequency band, the effective acceleration value corresponding to the vibration signal before vibration reduction is The effective acceleration value corresponding to the vibration signal after vibration reduction is .

[0037] Then the vibration reduction before the first The frequency domain vibration levels within a preset frequency band are: ; After vibration reduction The frequency domain vibration levels within a preset frequency band are: ; No. The frequency domain vibration level drop within a preset frequency band is: ; The preset frequency band can be a full frequency band, an octave band, or a third octave band, etc.

[0038] In this embodiment: The calculated vibration level in the frequency domain before vibration reduction during the acceleration period is as follows: Frequency band 1: 10-20 Hz = 0.0000486 , = 33.74 dB; Frequency band 2: 20-50 Hz = 0.002439 , = 67.74 dB; Frequency band 3: 50-100 Hz = 0.002317 , = 67.30 dB; The calculated vibration level in the frequency domain before vibration reduction during the deceleration period is as follows: Frequency band 1: 10-20 Hz = 0.0000640 , = 36.12 dB; Frequency band 2: 20-50 Hz = 0.001572 , = 63.93 dB; Frequency band 3: 50-100 Hz =0.002703 , = 68.64 dB; The results of frequency domain vibration level calculation before vibration reduction throughout the entire process are as follows: Frequency band 1: 10-20 Hz = 0.0000434 , = 32.76 dB; Frequency band 2: 20-50 Hz = 0.001421 , = 63.05 dB; Frequency band 3: 50-100 Hz = 0.003002 , = 69.55 dB; ④ The frequency domain vibration level calculation results after vibration reduction during the acceleration period are as follows: Band 1: The effective acceleration value after vibration reduction is: ; The corresponding frequency domain vibration level after vibration reduction is: ; The frequency domain vibration level drop is: .

[0039] Band 2: The effective acceleration value after vibration reduction is: ; The corresponding frequency domain vibration level after vibration reduction is: ; The frequency domain vibration level drop is: .

[0040] Band 3: The effective acceleration value after vibration reduction is: ; The corresponding frequency domain vibration level after vibration reduction is: ; The frequency domain vibration level drop is: .

[0041] Therefore, the frequency domain vibration level drops of each preset frequency band during the acceleration period are as follows: , and .

[0042] ⑤ The frequency domain vibration level calculation results after vibration reduction during the deceleration period are as follows: Band 1: The effective acceleration value after vibration reduction is: ; The corresponding frequency domain vibration level after vibration reduction is: ; The frequency domain vibration level drop is: .

[0043] Band 2: The effective acceleration value after vibration reduction is: ; The corresponding frequency domain vibration level after vibration reduction is: ; The frequency domain vibration level drop is: .

[0044] Band 3: The effective acceleration value after vibration reduction is: ; The corresponding frequency domain vibration level after vibration reduction is: ; The frequency domain vibration level drop is: .

[0045] Therefore, the frequency domain vibration level drops of each preset frequency band during the deceleration period are as follows: , and

[0046] ⑥ The calculated results of the frequency domain vibration level and frequency domain vibration level drop after vibration reduction during the entire start-up and shutdown process are as follows: Band 1: The effective acceleration value after vibration reduction is: ; The corresponding frequency domain vibration level after vibration reduction is: ; The frequency domain vibration level drop is: .

[0047] Band 2: The effective acceleration value after vibration reduction is: ; The corresponding frequency domain vibration level after vibration reduction is: ; The frequency domain vibration level drop is: .

[0048] Band 3: The effective acceleration value after vibration reduction is: ; The corresponding frequency domain vibration level after vibration reduction is: ; The frequency domain vibration level drop is: .

[0049] Therefore, the frequency domain vibration level drops of each preset frequency band during the entire start-up and shutdown process are 5.06dB, 9.38dB, and 8.79dB, respectively.

[0050] Step 5, Comprehensive Evaluation When multiple preset frequency bands exist, calculate the weighted average of the frequency domain vibration level difference: ; in, To preset the number of frequency bands, For the first Frequency domain vibration level drop within a preset frequency band For the first Weighting coefficients for each preset frequency band.

[0051] When the following conditions are met: ; When the above formula is used, it can be simplified to: ; The comprehensive evaluation value is calculated based on the time-domain vibration level difference and the frequency-domain vibration level difference: ; in, For comprehensive evaluation, and Let be the weighting coefficients, and satisfy: .

[0052] When the comprehensive evaluation value When the vibration reduction measure is greater than or equal to the preset evaluation threshold, it is determined that the vibration reduction performance meets the requirements during the unsteady start-up and shutdown of the ship's main engine; when the comprehensive evaluation value is greater than or equal to the preset evaluation threshold, it is determined that the vibration reduction performance meets the requirements. If the value is less than the preset evaluation threshold, the vibration reduction performance is deemed not to meet the requirements.

[0053] In this embodiment, the following is selected: , and Three preset frequency bands. Weights are assigned to each of these three frequency bands: And satisfy: 。

[0054] Based on the previous calculations: (1) The frequency domain vibration level drops of each preset frequency band during the acceleration period are as follows: ; ; ; The weighted average of the frequency domain vibration level drop during the acceleration period is: ; ; The time-domain vibration level drop during the acceleration period is: ; The weighting coefficients for the time-domain vibration level difference and the frequency-domain vibration level difference are as follows: ; And it satisfies: ; The comprehensive evaluation value for the acceleration period is: ; .

[0055] (2) The frequency domain vibration level drops of each preset frequency band during the deceleration period are as follows: ; ; ; The weighted average of the frequency domain vibration level drop during the deceleration period is: ;

[0056] The time-domain vibration level drop during the deceleration period is: ; The comprehensive evaluation value for the deceleration period is: .

[0057] (3) The entire start-up and shutdown process Based on a comprehensive evaluation, the frequency domain vibration level drops of each preset frequency band during the entire start-up and shutdown process are as follows: ; ; ; The weighted average value of the frequency domain vibration level drop during the entire start-up and shutdown process is: ; .

[0058] The time-domain vibration level drop during the entire start-up and shutdown process is: ; The overall evaluation value of the entire start-stop process is: ; .

[0059] Let the preset evaluation threshold be: ; because: ; ; ; Therefore, it was determined that the vibration reduction measure was effective during the ship's main engine acceleration and deceleration phases, as well as throughout the entire process. It exhibits good vibration reduction effects during unsteady start-up and shutdown processes, and its vibration reduction performance meets the requirements, such as... Figure 5 As shown.

[0060] The above embodiments are merely exemplary embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art can make various modifications or equivalent substitutions to the present invention within its scope and spirit, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of the present invention.

Claims

1. A method for evaluating vibration reduction performance under unsteady excitation, characterized in that, Includes the following steps: Step 1: Install vibration sensors on the ship being evaluated and collect vibration signals of the evaluated object before and after vibration reduction under unsteady excitation. Step 2: Determine the start and end times of the unsteady-state excitation based on the amplitude changes of the vibration signals before and after vibration reduction or based on the rotational speed changes of the ship being evaluated. Step 3: During the unsteady excitation time period obtained in Step 2, calculate the time-domain characteristic quantities of the vibration signal before vibration reduction and the vibration signal after vibration reduction, and calculate the time-domain vibration level drop based on the time-domain characteristic quantities; Step 4: Within the time period corresponding to the unsteady excitation obtained in Step 2, perform frequency domain analysis on the vibration signals before and after vibration reduction, and calculate the frequency domain vibration level difference before and after vibration reduction; Step 5: Calculate the comprehensive evaluation value based on the time-domain vibration level difference obtained in Step 3 and the frequency-domain vibration level difference obtained in Step 4, and evaluate the vibration reduction performance under unsteady excitation based on the comparison between the comprehensive evaluation value and the preset evaluation threshold. Step 3 specifically involves: Step 3.1, during the non-steady-state excitation period Within, the vibration acceleration signals before vibration reduction were extracted respectively. Vibration acceleration signal after vibration reduction ; Step 3.2, calculate the effective acceleration value before vibration reduction: ; Step 3.3, calculate the effective acceleration value after vibration reduction: ; Step 3.4, calculate the time-domain vibration level before and after vibration reduction: ； in, For reference acceleration values, The time-domain vibration level corresponding to the vibration signal before vibration reduction. This represents the time-domain vibration level corresponding to the vibration signal after vibration reduction. Step 3.5, calculate the time-domain vibration level drop as follows: ; The specific calculation process for the frequency domain vibration level drop in step 4 is as follows: ； in, For the first Frequency domain vibration levels within a preset frequency band For the first Effective acceleration values ​​within a preset frequency band For reference acceleration values, For the first Frequency domain vibration level drop within a preset frequency band The vibration signal before vibration reduction is at the first Frequency domain vibration levels within a preset frequency band The vibration signal after vibration reduction is at the first... Frequency domain vibration level within a preset frequency band.

2. The method for evaluating the vibration reduction performance under unsteady excitation according to claim 1, characterized in that, The ship being evaluated in step 1 includes the ship's main engine, auxiliary machinery, pump sets, gearboxes, shaft support structures, vibration isolation devices, or hull structures connected to the power machinery; the unsteady excitation includes vibration excitation generated during the start-up, shutdown, acceleration, deceleration, operating condition switching, or speed change of the ship's power machinery.

3. The method for evaluating the vibration reduction performance under unsteady excitation according to claim 1, characterized in that, Step 2 specifically involves: when the amplitude of the vibration signal before or after vibration reduction exceeds a preset amplitude threshold, or when the rate of change of the rotational speed of the ship being evaluated is greater than a preset rate of change of rotational speed threshold, the corresponding moment is determined as the start moment of the unsteady-state excitation; when the amplitude is less than or equal to the preset amplitude threshold or the rate of change of rotational speed is lower than the preset rate of change of rotational speed threshold and continues for a preset time, the corresponding moment is determined as the end moment of the unsteady-state excitation.

4. The method for evaluating the vibration reduction performance under unsteady excitation according to claim 1, characterized in that, In step 3, the time-domain characteristic quantity includes at least one of effective value and peak value, and the time-domain vibration level difference includes at least one of root mean square vibration level difference and peak vibration level difference.

5. The method for evaluating vibration reduction performance under unsteady excitation according to claim 1, characterized in that, In step 4, the frequency domain analysis includes at least one of Fast Fourier Transform, Short-Time Fourier Transform, Piecewise Fourier Transform, Octave Band Analysis, or Power Spectral Density Analysis; the preset frequency band corresponding to the frequency domain vibration level drop includes at least one of low-frequency band, mid-frequency band, high-frequency band, and octave band.

6. The method for evaluating the vibration reduction performance under unsteady excitation according to claim 1, characterized in that, The comprehensive evaluation value E in step 5 is: ； ; in, and Let be the weighting coefficients, and satisfy: ; This is the weighted average of the frequency domain vibration level differences; For the first Frequency domain vibration level drop within a preset frequency band For the first Weighting coefficients for a preset frequency band To preset the number of frequency bands, This represents the time-domain vibration level difference.

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