Method for testing vibration transmissibility of autonomously excited active vibration isolator

Abstract

The invention belongs to the technical field of vibration isolation testing, and particularly relates to a method for testing the vibration transmissibility of an autonomous excitation active vibration isolator. The method comprises the steps of excitation signal generation and input, vibration signal acquisition, signal coherence analysis and vibration transmissibility calculation. Due to the fact that ultra-precision equipment is sensitive to environmental vibration, an active vibration isolator is usually needed when the ultra-precision equipment is used, and low-frequency vibration such as ground vibration is isolated. In order to evaluate the vibration isolation performance of the active vibration isolator, the vibration transmissibility of the active vibration isolator needs to be tested and analyzed. According to the test method, an actuator and a sensor of the active vibration isolator are adopted, and an additional excitation device and a test sensor are not needed. The method provided by the invention is simple and convenient to implement, short in time consumption and good in test effect, and can solve the technical problem of testing the vibration transmissibility of the active vibration isolator.

Description

Technical Field

[0001] The invention relates to the technical field of vibration isolation testing, and in particular to a vibration transmissibility testing method for an autonomously excited active vibration isolator. Background Art

[0002] As the precision of ultra-precision processing, measurement and manufacturing equipment continues to improve, precision equipment is becoming more sensitive to environmental vibrations. Active vibration isolators are usually used in precision equipment because of their good vibration isolation effect in the low frequency band, and can isolate low-frequency vibrations such as ground vibration.

[0003] As an evaluation index for the vibration isolation performance of active vibration isolators, vibration transmissibility indicates their vibration isolation performance at different frequencies. The transmissibility test of active vibration isolators usually uses an exciter or hammer method, which requires an external excitation device and a test sensor, and faces the problems of complex testing, high cost, long time consumption, and poor results. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a vibration transmissibility test method for an autonomously excited active vibration isolator; the present invention uses its own built-in actuator and sensor to realize signal excitation and acquisition functions according to the characteristics of the active vibration isolator itself, and performs vibration transmissibility test while performing closed-loop control of active vibration reduction, without introducing additional costs, the test is short in time and has good results. The technical solution of the present invention is specifically described as follows.

[0005] The present invention provides a vibration transmissibility testing method for an autonomously excited active vibration isolator, comprising the following steps:

[0006] 1) Design an excitation signal x and use the excitation device of the active vibration isolator itself to perform vibration excitation on the active vibration isolator.

[0007] 2) The active vibration isolator itself is used for signal acquisition to obtain the vibration signal y of the active vibration isolator under the excitation signal.

[0008] 3) According to the applied excitation signal x and the vibration signal y of the active vibration isolator collected under excitation, the frequency response X of the excitation signal and the frequency response Y of the vibration signal are calculated by Fourier transform. The auto-power spectrum density Sxx of the excitation signal, the auto-power spectrum density Syy of the vibration signal and the cross-power spectrum density Sxy of the two are calculated respectively, so as to calculate the coherence Cxy of the two and judge the credibility of this test method. If the coherence is poor, it is necessary to consider increasing the amplitude of the excitation signal or changing the type of excitation signal;

[0009] 4) Calculate the transfer function Gxy from the excitation signal to the vibration signal based on the obtained excitation signal frequency response X and the vibration signal frequency response Y. Combined with the known force transfer function GF, the vibration transmissibility T of the active vibration isolator is calculated.

[0010] Furthermore, the above step 1) is specifically as follows:

[0011] 11) According to the target frequency band and response size of the test, design an excitation signal {x=x(n)} that can fully excite the system vibration, where n=0,1,…,N-1, and N is the length of the signal sequence. The sampling frequency of the test system is Fs, and the expression of the time T of the excitation signal is T=N / Fs.

[0012] Commonly used excitation signal forms include Gaussian white noise signal, band-limited white noise signal and swept frequency sine signal.

[0013] 12) Add the generated excitation signal {x=x(n)} to the actuator signal input position of the control loop of the active vibration isolator. Further, the above step 2) is specifically as follows:

[0014] 21) During the vibration excitation process, the sensor in the active vibration isolator control loop is used to collect the vibration signal of the active vibration isolator {y=y(n)}, where n=0, 1, ..., N-1, and N is the signal length. The current excitation signal value and the current vibration signal value are recorded in real time, that is, at the i-th moment, the excitation signal is x(i), and the corresponding vibration signal is y(i).

[0015] Furthermore, the above step 3) is specifically as follows:

[0016] 31) According to the applied excitation signal {x=x(n)} and the collected vibration signal {y=y(n)} of the active vibration isolator, the frequency response X(f) of the excitation signal and the frequency response Y(f) of the vibration signal are obtained by discrete Fourier transform, and the formula is as follows:

[0017]

[0018]

[0019] 32) According to the obtained frequency response X(f) of the excitation signal and the frequency response Y(f) of the vibration signal, the auto-power spectrum density Sxx(f) of the excitation signal, the auto-power spectrum density Syy(f) of the vibration signal and the cross-power spectrum density Sxy(f) of the two are calculated respectively, and the formula is as follows:

[0020]

[0021]

[0022]

[0023] 33) According to the obtained self-power spectrum density Sxx(f) of the excitation signal, the self-power spectrum density Syy(f) of the vibration signal and the cross-power spectrum density Sxy(f), the coherence Cxy(f) of the two can be calculated to determine the credibility of this test method. The formula is as follows:

[0024]

[0025] The value range of Cxy(f) is between 0 and 1. Usually the coherence exceeds 0.95, and the test data at this frequency point is considered credible.

[0026] Furthermore, the above step 4) is specifically as follows:

[0027] 41) According to the calculated frequency response X(s) of the excitation signal and the frequency response Y(s) of the vibration signal, the transfer function Gxy(s) from the excitation signal to the vibration signal can be obtained. The formula is as follows:

[0028]

[0029] 42) For a common isolator transfer function model Gplant(s), it is defined as the ratio of the frequency response F(s) of the force signal applied to the isolator to the frequency response Aplant(s) of the vibration acceleration signal on it. A second-order spring damping model is usually used, where the system mass m, system damping coefficient c, and system stiffness coefficient k are all known quantities. The expression is as follows:

[0030]

[0031] Then the expression of the force transfer function GF(s) is as follows:

[0032]

[0033] 43) The vibration transmissibility T(s) is usually defined as the ratio of the frequency response Xground(s) of the ground vibration displacement signal to the frequency response Xplant(s) of the tabletop vibration displacement signal. It can also be expressed as the ratio of the frequency response Accground(s) of the ground vibration acceleration signal to the frequency response Accplant(s) of the tabletop vibration acceleration signal. The actuator converts the voltage output U(s) of the excitation signal into a force F(s) applied to the vibration isolator. The transfer function of the actuator is usually regarded as a constant proportional gain k0, that is, the actuator transfer function Gv(s) = k0. The expression of the vibration transmissibility T(s) is as follows:

[0034]

[0035] As mentioned above, the vibration transmissibility test method of a self-excited active vibration isolator proposed in the present invention requires the design of an excitation signal, and the use of the actuator of the active vibration isolator itself for vibration excitation. While the vibration excitation is in progress, the sensor of the active vibration isolator itself is used to collect the vibration signal of the vibration isolator. After completing a test, a series of discrete excitation signals and the vibration signals of the vibration isolator at the corresponding moments can be obtained. The excitation signal and the vibration signal are subjected to a discrete Fourier transform to obtain the frequency responses of the two, and the auto-power spectral density and the cross-power spectral density of the two are calculated, and the coherence of the two is further calculated. The credibility of this test can be judged by the coherence. On the basis of the credibility of this test, the transfer function from the excitation signal to the vibration signal is calculated according to the frequency response of the excitation signal and the frequency response of the vibration signal. The vibration transmissibility can be calculated by the known actuator transfer function and the force transfer function. Compared with the prior art, the beneficial effects of the present invention are:

[0036] The present invention proposes a vibration transmissibility test method for an autonomously excited active vibration isolator, which uses the actuator of the active vibration isolator itself as a vibration excitation device, and uses the sensor of the active vibration isolator itself as a vibration signal acquisition device. Traditional vibration transmissibility tests usually use an exciter or a hammer method. Since an external excitation device and a test sensor are required to perform multi-point distributed testing, the testing process is complicated, the testing cost is high, the testing time is long, and the coherence obtained from the test is poor. The present invention proposes a vibration transmissibility test method for an autonomously excited active vibration isolator, which does not require additional devices and has low testing costs. Only one round of excitation signal input and vibration signal collection needs to be completed, and the testing process is simple, the time is short, and the coherence obtained from the test is good. The present invention uses the actuator and sensor of the active vibration isolator itself to complete the vibration transmissibility test, which has clear ideas, convenient implementation, short testing time and good results, and has universality and applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The test process of the present invention is shown in FIG.

[0038] Figure 2 Schematic diagram of the control loop of the testing method of the present invention.

[0039] Figure 3 It is a schematic diagram of the time domain response of the excitation signal and the time domain response of the vibration signal.

[0040] Figure 4 It is a schematic diagram of the frequency response of the excitation signal and the frequency response of the vibration signal.

[0041] Figure 5 Schematic diagram of the auto-power spectrum density and cross-power spectrum density of the excitation signal and the vibration signal.

[0042] Figure 6 This is an illustration of the coherence between the excitation signal and the vibration signal.

[0043] Figure 7 Schematic diagram of the transfer function from excitation signal to vibration signal.

[0044] Figure 8 Schematic diagram of the vibration transmissibility obtained by the test method of the present invention.

[0045] Fig. 9 The figure shows the comparison between the transfer function from the excitation signal to the vibration signal and the simulated interference sensitivity function.

[0046] Fig.10 The figure is a comparison diagram of the vibration transmissibility obtained by the test method of the present invention and the simulated vibration transmissibility.

[0047] Fig.11 Schematic diagram of the coherence between the excitation signal and the vibration signal in the passive vibration isolation test.

[0048] Fig.12 The figure shows the comparison between the vibration transmissibility of active control and that of passive vibration isolation. DETAILED DESCRIPTION

[0049] The present invention is described below in conjunction with specific embodiments.

[0050] The present invention discloses a method for testing the vibration transmissibility of an autonomously excited active vibration isolator, which includes the generation and input of an excitation signal, vibration signal acquisition, signal coherence analysis and vibration transmissibility calculation. Since ultra-precision equipment is relatively sensitive to environmental vibrations, it is usually necessary to use active vibration isolators to isolate low-frequency vibrations such as ground vibrations when in use. In order to evaluate the vibration isolation performance of active vibration isolators, it is necessary to test and analyze the vibration transmissibility of the active vibration isolators. The test method adopted in the present invention uses the actuator and sensor of the active vibration isolator itself, and does not require additional excitation devices and test sensors. The method proposed in the present invention is simple to implement, short in time, and has good test effect, and can solve the technical problem of how to test the vibration transmissibility of active vibration isolators.

[0051] Example 1

[0052] In the vibration transmissibility test of the active vibration isolator of the present invention, the active vibration isolation platform is composed of four supporting active vibration isolators and a marble platform, and each active vibration isolator is installed with multiple voice coil motors as actuators and multiple acceleration sensors as vibration sensors.

[0053] The present invention discloses a vibration transmissibility test method for an autonomously excited active vibration isolator, which mainly includes:

[0054] S1) Design the excitation signal x according to the test frequency band and response size, and use the actuator of the active vibration isolator itself for excitation; the excitation signal needs to include the target frequency band and have a certain amplitude. If the vibration test response is too small, that is, the excitation signal does not fully excite the vibration of the system, it is necessary to adjust the amplitude of the excitation signal according to the test response size so that it can fully excite the vibration of the system.

[0055] S2) The sensor of the active vibration isolator itself is used to collect signals to obtain the vibration signal y of the active vibration isolator under the excitation signal.

[0056] S3) According to the applied excitation signal x and the vibration signal y of the active vibration isolator collected under the excitation, the frequency response X of the excitation signal and the frequency response Y of the vibration signal are calculated by Fourier transform. The auto-power spectrum density Sxx of the excitation signal, the auto-power spectrum density Syy of the vibration signal and the cross-power spectrum density Sxy of the two are calculated respectively, so as to calculate the coherence Cxy of the two and judge the credibility of this test method.

[0057] S4) Calculate the transfer function Gxy from the excitation signal to the vibration signal based on the obtained excitation signal frequency response X and the vibration signal frequency response Y. Combined with the known force transfer function GF and actuator transfer function Gv, the vibration transmissibility T of the active vibration isolator is obtained by solution.

[0058] Furthermore, the above step S1) is specifically as follows:

[0059] S1001) The sampling frequency of the active vibration isolator used in this example is Fs = 5000 Hz, and the vibration transmissibility frequency band of interest is 1-100 Hz. Design a swept frequency sinusoidal excitation signal {x = x(n)}, where n = 0, 1, ..., 500000-1, 500000 is the length of the signal sequence, n represents the order of the discrete signal sequence, dimensionless; x(1) represents the first value, and x(2) represents the second value. n itself represents the dimensionless order. The time T of the excitation signal is N / Fs = 100s.

[0060] S1002) Adding the generated excitation signal x to the actuator signal input position of the control loop of the active vibration isolator, and using the actuator of the active vibration isolator to perform vibration excitation.

[0061] Furthermore, the above step S2) is specifically as follows:

[0062] S2001) During the vibration excitation process, the sensor in the active vibration isolator control loop is used to collect the vibration signal of the active vibration isolator {y=y(n)}, where n=0,1,…,500000-1. The current excitation signal value and the current vibration signal value are recorded in real time, that is, at the i-th moment, the excitation signal is x(i), and its corresponding vibration signal is y(i). The time domain response of the excitation signal and the time domain response of the vibration signal are finally obtained as shown in Figure 3 shown.

[0063] Furthermore, the above step S3) is specifically as follows:

[0064] S3001) According to the applied excitation signal {x=x(n)} and the collected vibration signal {y=y(n)} of the active vibration isolator, a discrete Fourier transform is used to obtain the frequency response X(f) of the excitation signal and the frequency response Y(f) of the vibration signal, and the formula is as follows:

[0065]

[0066]

[0067] The calculation results are as follows Figure 4 shown.

[0068] S3002) According to the obtained frequency response X(f) of the excitation signal and the frequency response Y(f) of the vibration signal, the auto-power spectrum density Sxx(f) of the excitation signal, the auto-power spectrum density Syy(f) of the vibration signal and the cross-power spectrum density Sxy(f) of the two are calculated respectively, and the formula is as follows:

[0069]

[0070]

[0071]

[0072] The calculation results are as follows Figure 5 shown.

[0073] S3003) According to the obtained self-power spectrum density Sxx(f) of the excitation signal, the self-power spectrum density Syy(f) of the vibration signal and the cross-power spectrum density Sxy(f) of the two, the coherence Cxy(f) of the two can be calculated to determine the credibility of this test method. The formula is as follows:

[0074]

[0075] The calculation results are as follows Figure 6The horizontal axis is the frequency value, and the vertical axis is the coherence. The value indicates the coherence of the frequency response, which can be understood as whether the phase difference between the frequency component in the output signal and the frequency component in the input signal is constant.

[0076] The value range of Cxy(f) is between 0 and 1. Usually, the coherence exceeds 0.95, and the test data at this frequency point is considered to be credible. In this example, the vibration transmissibility test is mainly carried out for 1-100Hz. From the coherence calculation results, it can be seen that within the 1-100Hz frequency band, the signal coherence obtained by this test method exceeds 0.99.

[0077] Furthermore, the above step S4) is specifically as follows:

[0078] S4001) According to the calculated excitation signal frequency response X(s) and vibration signal frequency response Y(s), the transfer function Gxy(s) from the excitation signal to the vibration signal can be obtained. The formula is as follows:

[0079]

[0080] The calculation results are as follows Figure 7 Shown

[0081] S4002) For the transfer function model Gplant(s) of the active vibration isolator in this example, it is defined as the ratio of the frequency response F(s) of the force signal applied to the vibration isolator to the frequency response Aplant(s) of the vibration acceleration signal thereon. A second-order spring damping model is usually used, in which the system mass m, the system damping coefficient c, and the system stiffness coefficient k are all known quantities. These three values ​​are the inherent characteristics of the system and are also the parameters determined during the mechanism design. The expressions are as follows:

[0082] m=1740kg

[0083] c=1.09×10Ns / m

[0084] k=1.011×107N / m

[0085]

[0086] Then the expression of the force transfer function GF(s) is as follows:

[0087]

[0088] S4003) The vibration transmissibility T(s) is usually defined as the ratio of the frequency response Xground(s) of the ground vibration displacement signal to the frequency response Xplant(s) of the tabletop vibration displacement signal. It can also be expressed as the ratio of the frequency response Accground(s) of the ground vibration acceleration signal to the frequency response Accplant(s) of the tabletop vibration acceleration signal. The actuator converts the voltage output U(s) of the excitation signal into a force F(s) applied to the vibration isolator. The transfer function of the actuator is usually regarded as a constant proportional gain of 33.6 (indicating that the motor used in the system generates a force of 33.6N under an input signal of 1V), that is, the actuator transfer function Gv(s) = 33.6. The expression of the vibration transmissibility T(s) is as follows:

[0089]

[0090] The calculation results are as follows Figure 8 shown.

[0091] Example 2

[0092] Example 2 is a comparison between the vibration transmissibility obtained by the test method proposed in the present invention in Example 1 and the vibration transmissibility obtained by simulation under ideal conditions.

[0093] S1) According to the known transfer function model Gplant(s) of the active vibration isolator and the known controller transfer function Gcontrol(s), the disturbance sensitivity function Tdy(s) of the active vibration isolation control system can be calculated by simulation, and the expression is as follows:

[0094]

[0095] The transfer function Gxy(s) from the excitation signal to the vibration signal obtained by the test method proposed in the present invention and the interference sensitivity function Tdy(s) obtained under simulation conditions are as follows: Fig. 9 As shown, the two have a high degree of similarity.

[0096] S2) According to the known force transfer function GF(s) and actuator transfer function Gv(s), the ideal vibration transmissibility can be obtained through simulation, and the expression is as follows:

[0097]

[0098] The vibration transmissibility T(s) obtained by the test method proposed in the present invention is compared with the ideal vibration transmissibility Tideal(s) obtained under simulation conditions. Fig.10As shown, the two have a high degree of similarity. The transmissibility test result obtained by the test method proposed in the present invention has a high degree of credibility and a good test effect. The test method proposed in the present invention does not require an external excitation device and a sensor device. In this example, the test time is only 100 seconds, which is low in cost and time.

[0099] Example 3

[0100] Example 3 is a comparison of the vibration transmissibility of the vibration isolation platform obtained by the test method proposed in the present invention in Example 1 when active control is adopted and the vibration transmissibility of the vibration isolation platform obtained by the test method proposed in the present invention when no active control is adopted.

[0101] S1) The active control loop of the active vibration isolator is closed, and only the passive vibration isolation link in the active vibration isolator provides the vibration isolation effect, and the input signal of the actuator only includes the excitation signal.

[0102] S2) Using the same excitation signal {x=x(n)} as in Example 1, the actuator of the active vibration isolator itself is used for excitation.

[0103] S3) Using the sensor of the active vibration isolator itself to collect signals, a vibration signal {yp=yp(n)} of the active vibration isolator under the excitation signal is obtained.

[0104] S4) According to the applied excitation signal x and the vibration signal yp of the active vibration isolator collected under excitation, the frequency response X(f) of the excitation signal and the frequency response YP(f) of the vibration signal are calculated by Fourier transform. The auto-power spectrum density Sxx(f) of the excitation signal, the auto-power spectrum density Sypyp(f) of the vibration signal and the cross-power spectrum density Sxyp(f) of the two are calculated respectively, so as to calculate the coherence Cxyp(f) of the two and judge the credibility of this test.

[0105] The signal coherence of passive vibration isolation obtained by testing is as follows: Fig.11 As shown, within the frequency band of interest, 1-100 Hz, the signal coherence exceeds 0.98.

[0106] S5) According to the obtained excitation signal frequency response X(s) and vibration signal frequency response YP(s), the transfer function Gxyp(s) from the excitation signal to the vibration signal is calculated. Combined with the known force transfer function GF(s) and actuator transfer function Gv(s), the vibration transmissibility Tp(s) of the vibration isolator is obtained by solution.

[0107] The comparison between the vibration transmissibility of active control and passive vibration isolation is shown in the following figure. Fig.12As shown, the vibration transmissibility of passive vibration isolation and active vibration isolation under classical theory is the same. Based on the actuator and sensor of the active vibration isolator itself, the test method proposed in the present invention can test the vibration transmissibility under active control, and can also test the vibration transmissibility of passive vibration isolation of its passive link.

Claims

1. A vibration transmissibility test method for an autonomously excited active vibration isolator, characterized in that: The following steps are involved: 1) Design the excitation signal x, and use the actuator of the active vibration isolator as the excitation device to vibrate the active vibration isolator; 2) Using the sensor of the active vibration isolator itself to collect signals, and obtaining the vibration signal y of the active vibration isolator under the excitation signal; 3) According to the applied excitation signal x and the vibration signal y of the active vibration isolator collected under the excitation, the frequency response X of the excitation signal and the frequency response Y of the vibration signal are calculated by Fourier transform; the auto-power spectrum density Sxx of the excitation signal, the auto-power spectrum density Syy of the vibration signal and the cross-power spectrum density Sxy of the two are calculated respectively, so as to calculate the coherence Cxy of the two and judge the credibility of this test; if the coherence is not good, return to step 1) to increase the amplitude of the excitation signal or change the type of excitation signal; 4) On the basis of the test credibility, the transfer function Gxy from the excitation signal to the vibration signal is calculated according to the obtained excitation signal frequency response X and the vibration signal frequency response Y; combined with the known force transfer function GF and actuator transfer function Gv, the vibration transmissibility T of the active vibration isolator is solved.

2. The vibration transmissibility test method of the self-excited active vibration isolator according to claim 1, characterized in that: In step 1), the excitation signal is in the form of a Gaussian white noise signal, a band-limited white noise signal or a swept frequency sine signal.

3. The vibration transmissibility test method of the self-excited active vibration isolator according to claim 1, characterized in that: The step 1) is specifically as follows: 11) According to the target frequency band and response size of the test, design an excitation signal {x=x(n)} that can fully excite the system vibration, where n=0,1,…,N-1, n represents the dimensionless order, and N is the length of the signal sequence; the sampling frequency of the test system is Fs, then the expression of the time T of the excitation signal is T=N / Fs; 12) The generated excitation signal {x=x(n)} is added to the actuator signal input position of the control loop of the active vibration isolator, and the excitation device is used to perform vibration excitation.

4. The vibration transmissibility test method of the self-excited active vibration isolator according to claim 1, characterized in that: Step 2) is specifically as follows: 21) During the vibration excitation process, a sensor is used to collect the vibration signal of the active vibration isolator {y=y(n)}, where n=0, 1,…, N-1, and N is the signal length. The current excitation signal value and the current vibration signal value are recorded in real time, that is, at the i-th moment, the excitation signal is x(i), and the corresponding vibration signal is y(i).

5. The vibration transmissibility test method of the self-excited active vibration isolator according to claim 1, characterized in that: Step 3) is specifically: 31) According to the applied excitation signal {x=x(n)} and the collected vibration signal {y=y(n)} of the active vibration isolator, the time domain signal is transformed by discrete Fourier transform to obtain the frequency response X(f) of the excitation signal and the frequency response Y(f) of the vibration signal, where f represents the frequency; 32) According to the obtained frequency response X(f) of the excitation signal and the frequency response Y(f) of the vibration signal, the auto-power spectrum density Sxx(f) of the excitation signal, the auto-power spectrum density Syy(f) of the vibration signal and the cross-power spectrum density Sxy(f) of the two are calculated respectively, and the formula is as follows: Where: X * (f) is the conjugate of X(f), Y * (f) is the conjugate of Y(f); 33) According to the obtained self-power spectrum density Sxx(f) of the excitation signal, the self-power spectrum density Syy(f) of the vibration signal and the cross-power spectrum density Sxy(f), the coherence Cxy(f) of the two is calculated to determine the credibility of this test method. The formula is as follows: 34) When the coherence Cxy(f) exceeds 0.95, the test data of this frequency point is determined to be credible; otherwise, increase the amplitude of the excitation signal or change the type of excitation signal to re-vibrate the active vibration isolator.

6. The vibration transmissibility test method of the self-excited active vibration isolator according to claim 1, characterized in that: Step 4) is specifically as follows: 41) Based on Laplace transform, according to the frequency response X(f) of the excitation signal and the frequency response Y(f) of the vibration signal, the frequency response X(s) of the excitation signal and the frequency response Y(s) of the vibration signal are calculated, where s represents a complex variable, and then the transfer function Gxy(s) from the excitation signal to the vibration signal is obtained; the formula is as follows: s=j·2π·f, 42) For an active vibration isolator transfer function model Gplant(s), which is defined as the ratio of the frequency response F(s) of the force signal applied to the vibration isolator to the frequency response Aplant(s) of the vibration acceleration signal on it, the mass-spring-damper system transfer function model is used to describe the dynamic characteristics of the system. Combined with the system mass m, system damping coefficient c, and system stiffness coefficient k, which are all known quantities, the force transfer function GF(s) is solved; 43) The vibration transmissibility T(s) is defined as the ratio of the frequency response Xground(s) of the ground vibration displacement signal to the frequency response Xplant(s) of the tabletop vibration displacement signal; it can also be expressed as the ratio of the frequency response Accground(s) of the ground vibration acceleration signal to the frequency response Accplant(s) of the tabletop vibration acceleration signal; the actuator converts the voltage output U(s) of the excitation signal into a force F(s) applied to the vibration isolator, and the transfer function of the actuator is regarded as a constant proportional gain k0, that is, the actuator transfer function Gv(s) = k0, then the expression of the vibration transmissibility T(s) is as follows:

7. The vibration transmissibility test method of the self-excited active vibration isolator according to claim 6, characterized in that: Using the second-order spring damping transfer function model as the transfer function model Gplant(s), we have: Then the expression of the force transfer function GF(s) is as follows:

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