Method for calculating the vibration of a ship hull under the influence of a device

Abstract

The present application relates to a kind of equipment excitation under ship body vibration calculation method, by means of test, numerical calculation etc., obtain necessary data, according to the data obtained, the vibration acceleration of equipment excitation under ship body response point is calculated.The A in the present application is the transfer matrix of upper layer vibration isolator group, by the acceleration impedance Z u of upper layer vibration isolator.The B is the transfer matrix of floating raft, by the acceleration admittance Y b of floating raft.The C is the transfer matrix of lower layer vibration isolator group, by the acceleration impedance Z d of upper layer vibration isolator.The D is the acceleration admittance of ship body structure excitation point.L is the transfer function of ship body structure response point acceleration a d compared to ship body structure excitation point force F.By a p ,Y0,Y p , a0 is calculated, if equipment is directly installed in ship body structure, by a0,Y0,Y g , F is calculated, if equipment is installed in ship body structure through vibration isolator floating raft, G is obtained according to a0,Y0,Y g first, then G,A,B,C,D is calculated to obtain F, finally, F,L is used to calculate a d .

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ship vibration calculation, and particularly relates to a calculation method of hull vibration under equipment excitation. BACKGROUND

[0002] For a ship structure, as a structure floating freely on water, it will inevitably be subjected to various excitations during its operation, causing overall vibration and local vibration of the ship. The excitations at this time can be divided into external excitations and internal excitations, the internal excitations including various equipment, propellers, personnel activities, etc., and the external excitations including external wind, waves, flow, etc. When the frequencies of these excitations are close to the natural frequencies of the ship, resonance will occur, causing damage and leading to excessive vibration of the ship. Excessive vibration of the ship may cause fatigue failure of the ship structure or mechanical parts at the stress excessive part, affecting the safety of navigation; excessive vibration will affect the normal work of the equipment and instruments on the ship, reduce the use precision, and shorten the service life; at the same time, it will produce noise, affect the physical and mental health of the personnel on the ship, reduce the living comfort, affect the work efficiency of the crew, and the riding experience of the passengers. Therefore, the vibration response of the ship is one of the important indicators of the ship, and needs to be concerned throughout the entire cycle of the ship operation.

[0003] In order to solve the problem of excessive vibration of the ship, a vibration reduction and isolation measure is taken, that is, the equipment is not directly connected with the ship body, but is connected with the ship structure through a vibration isolator raft, so as to reduce the excitation force of the equipment acting on the ship structure, thereby reducing the response of the ship structure.

[0004] In the design stage, the ship vibration needs to be calculated and predicted to evaluate whether the equipment selection, ship structure design, and vibration reduction and isolation scheme design are reasonable. At this time, a numerical calculation method is generally used, that is, a unit force is applied at the excitation position of the ship structure, the vibration at the position of the researcher's concern, i.e. the response point, is calculated, which is generally characterized by acceleration, and the average acceleration at the excitation point position can also be calculated. The acceleration a i at the response point is divided by the average acceleration a s at the connection point position to obtain the transfer function H, and then the acceleration a e at the response point under the equipment excitation is obtained by multiplying the transfer function H by the average acceleration value a r of the equipment factory test machine foot. The whole calculation process is represented by the formula as follows:

[0005] a r =a e ·H

[0006] H=a i / a s

[0007] The above method has two problems, on the one hand, if the vibration isolation measure is adopted, the equipment is connected with the ship body structure through the vibration isolator and the floating raft, and the ship body vibration under the equipment excitation cannot be calculated by the above method; on the one hand, the equipment factory test machine foot acceleration cannot be simply considered as equal to the machine foot acceleration of the equipment installed on the ship body structure. SUMMARY

[0008] The present application aims at the above-mentioned shortcomings in the prior production technology, and provides a calculation method of ship body vibration under equipment excitation, necessary data are obtained through testing and numerical calculation, and the ship body vibration when the equipment is installed on the ship body structure through the vibration isolator and the floating raft is calculated according to the obtained data.

[0009] The technical scheme adopted by the present application is as follows:

[0010] A calculation method of ship body vibration under equipment excitation comprises the following steps:

[0011] Obtaining equipment factory machine foot acceleration a p ,

[0012] Obtaining equipment machine foot acceleration admittance Y0,

[0013] Obtaining acceleration admittance Y of the equipment factory installation rack, p ,

[0014] Calculating the equipment machine foot free acceleration a0 through the above parameters,

[0015] Judging whether the equipment is directly installed on the ship body structure or installed on the ship body structure through the vibration isolator and the floating raft,

[0016] If the equipment is directly installed on the ship body structure, obtaining the ship body structure excitation point acceleration admittance matrix D, and calculating the excitation force F through the matrix,

[0017] If the equipment is installed on the ship body structure through the vibration isolator and the floating raft, obtaining the upper vibration isolator acceleration impedance Z u , the floating raft acceleration admittance Y b , the lower vibration isolator group acceleration impedance Z d , the ship body structure excitation point acceleration admittance D, obtaining the matrices A, B, C and Y g through the parameters, calculating the equipment machine foot input force G, and calculating the excitation force F,

[0018] After the excitation force F is calculated, obtaining the transfer function L,

[0019] Calculating the ship body structure response point acceleration A d through the transfer function.

[0020] Equipment factory machine foot acceleration ap The acquisition step is as follows:

[0021] The device is directly installed on the rack, acceleration sensors are arranged at the device foot positions and numbered, the acceleration sensors are connected with the data acquisition and analysis system, after the installation is completed, the device is started,

[0022] The accelerations at the measuring points are collected and assembled into a matrix a p .

[0023] The acquisition step of the acceleration mobility Y0 of the device foot is as follows:

[0024] The device is hoisted by an elastic rope, acceleration sensors are arranged at the foot mounting points of the rack and numbered, a force hammer or a vibration exciter, the acceleration sensors and the data acquisition and analysis system are connected,

[0025] After the installation is completed, the measuring points are sequentially excited by the force hammer or the vibration exciter, force and acceleration signals are collected, the force and the acceleration are processed by the analysis system, and the acceleration mobility at the foot mounting points of the rack is obtained, and the formula is Y=S aa / S fa ,

[0026] In the formula, S aa is the self-power spectrum of the acceleration signal during excitation, S fa is the cross-power spectrum of the force signal and the acceleration signal during excitation,

[0027] The measured acceleration mobility is assembled into a matrix Y0.

[0028] The acquisition step of the acceleration mobility Y p of the device factory-installed rack is as follows:

[0029] The device is hoisted by an elastic rope, acceleration sensors are arranged at the foot mounting points of the rack and numbered, a force hammer or a vibration exciter, the acceleration sensors and the data acquisition and analysis system are connected,

[0030] After the installation is completed, the measuring points are sequentially excited by the force hammer or the vibration exciter, force and acceleration signals are collected, the force and the acceleration are processed by the analysis system, and the acceleration mobility at the foot mounting points of the rack is obtained, and the formula is Y=S aa / S fa ,

[0031] In the formula, S aa is the self-power spectrum of the acceleration signal during excitation, S fa is the cross-power spectrum of the force signal and the acceleration signal during excitation,

[0032] The measured acceleration mobility is assembled into a matrix Y p .

[0033] The formula of the free acceleration a0 of the computing device is as follows:

[0034] a0 = (Y p + Y0) · Y p -1 · a p .

[0035] The steps of calculating the exciting point force of the computing device directly installed on the ship structure are as follows:

[0036] The acceleration admittance of the exciting point of the ship structure is obtained by numerical calculation,

[0037] The finite element model of the ship structure is established, the exciting points of the ship structure are numbered in turn, and a unit point force load is applied to calculate the acceleration response results of each exciting point, that is, the acceleration admittance of the installation foundation structure device installation point, which is assembled into a matrix D,

[0038] The exciting point force F of the ship structure is calculated by the formula F = (D + Y0) -1 · a f .

[0039] The steps of calculating the exciting point force of the device installed on the ship structure through the vibration isolator floating raft are as follows: the acceleration impedance Z u of the upper vibration isolator group is obtained by experimental test means,

[0040] The vibration isolator is placed on the impedance platform, the lower end is clamped on the force plate, and the upper end is connected to the impedance head,

[0041] The force sensor in the impedance head is connected to the exciter, the exciter is connected to the power amplifier and the signal generator, and the force plate and the impedance head are connected to the data acquisition system,

[0042] The signal generator is turned on, the exciter excites the vibration isolator, and the data acquisition system collects signals, and after the collection is completed, the signal generator is turned off,

[0043] The vibration isolator is removed and installed in reverse, the upper end is clamped on the force plate, and the lower end is connected to the impedance head,

[0044] The acceleration impedance test is performed,

[0045] After the data acquisition is completed, the acceleration impedance Z u11 , Z u12 , Z u21 , Z u22 of the vibration isolator is obtained by analyzing and processing the data with the data analysis system,

[0046] The impedance is calculated by the formula Z = S ff / Sfa The calculation yields S in the formula. ff To determine the self-power spectrum of the excitation force signal, S fa To determine the cross-power spectrum of the force signal and the acceleration signal during excitation,

[0047] The acceleration impedance Z of the lower-level vibration isolator group was obtained through experimental testing. d The acceleration impedance measured multiple times is recorded as Z. d11 Z d12 Z d21 Z d22 ,

[0048] A finite element model of the floating raft is established. The installation points of the upper-level vibration isolators are numbered sequentially: 1, 2, ..., n, where n is the number of upper-level vibration isolators. The installation points of the lower-level vibration isolators are numbered sequentially: n+1, n+2, ..., n+m, where m is the number of lower-level vibration isolators. A unit point force load is applied to each measuring point sequentially, and the acceleration response results of each measuring point are calculated, which is the acceleration admittance of the floating raft. These results are then assembled into a matrix Y. b ,

[0049] A finite element model of the hull structure is established, the excitation points of the hull structure are numbered sequentially, and a unit point force load is applied. The acceleration response results of each excitation point are calculated, which are the acceleration admittances of the installation points of the foundation structure equipment. These are then assembled into matrix D.

[0050] The admittance steps for the mounting foundation beneath the computer equipment feet are as follows:

[0051] Through formula Y g =Z u22 / (Z u11 ·Z u22 -Z u12 ·Z u21 Y is calculated using the formula )·I. g Let I be an n-order identity matrix.

[0052] The transfer matrix of the upper vibration isolator is obtained from the acceleration impedance of the upper vibration isolator group.

[0053] Let Z u11 =Z u11 ·I, Z u12 =Z u12 ·I, Z u21 =Z u21 ·I, Z u22 =Z u22 • I, where I is an n-order identity matrix. The transfer matrix A of the upper vibration isolator can be calculated using the following formula:

[0054]

[0055] The lower vibration isolator transfer matrix is obtained from the acceleration impedance of the lower vibration isolator group,

[0056] Let Z d11 = Z d11 · I, Z d12 = Z d12 · I, Z d21 = Z d21 · I, Z d22 = Z d22 · I, I is an m-order unit matrix. The upper vibration isolator transfer matrix C can be calculated by the following formula:

[0057]

[0058] The raft transfer matrix B is obtained from the acceleration admittance of the raft,

[0059] The raft acceleration admittance Let

[0060]

[0061]

[0062]

[0063]

[0064] The raft transfer matrix B can be calculated by the following formula:

[0065]

[0066] The equipment foot input force G is calculated by the formula G = (Y g + Y0) -1 · a f

[0067] The matrices A, B, and C are expressed in the following form:

[0068]

[0069] The new matrix T is obtained by multiplying A, B, and C, and the matrix T is expressed in a similar form:

[0070]

[0071] The ship structure excitation force F is calculated by the formula F = (T 11 + T 12 · D) -1 · G.

[0072] ​The steps for obtaining the transfer function of the acceleration of the response point of the ship structure to the force of the excitation point of the ship structure by numerical calculation are as follows:

[0073] A finite element model of the ship structure is established, and a unit point force load is applied to the excitation point of the ship structure in sequence, and the acceleration results of each response point are calculated, that is, the transfer function of the acceleration of the response point of the ship structure to the force of the excitation point of the ship structure, which is assembled into a matrix L,

[0074] The acceleration a of the response point of the ship structure is calculated by the formula a d =L·F. d .

[0075] The beneficial effects of the present application are as follows:

[0076] The calculation method of the present application is applicable to any installation mode, whether the equipment is directly installed on the ship structure or installed on the ship structure through a vibration isolator floating raft, the ship vibration under the excitation of the equipment can be calculated.

[0077] By substituting the free acceleration of the machine foot into the calculation, compared with the way of substituting the factory-out machine foot acceleration into the calculation, the calculation method of the present application is more accurate. BRIEF DESCRIPTION OF DRAWINGS

[0078] Figure 1 It is the overall idea framework diagram of the present application.

[0079] Figure 2-1 It is the working condition schematic diagram of the present application in which the equipment is directly installed on the ship structure.

[0080] Figure 2-2 It is the working condition schematic diagram of the present application in which the equipment is installed on the ship structure through a vibration isolator floating raft. DETAILED DESCRIPTION

[0081] The specific implementation mode of the present application will be described below in combination with the drawings.

[0082] The present application discloses a calculation method of ship vibration under equipment excitation, and the specific process is as follows:

[0083] (1) The acceleration of the machine foot of the equipment installed on the rack at the factory is obtained by test testing:

[0084] The equipment is directly installed on the rack, acceleration sensors are arranged at the equipment machine foot positions and numbered, the acceleration sensors are connected with a data acquisition and analysis system, after installation is completed, the equipment is started, the accelerations at each measuring point are collected, and a matrix a p is assembled.

[0085] (2) The acceleration admittance of the equipment machine foot is obtained by test testing:

[0086] The equipment is hoisted by elastic ropes, the acceleration sensor is arranged at the foot mounting point of the test stand, each measuring point is numbered, the force hammer or exciter, the acceleration sensor and the data acquisition and analysis system are connected. After installation, the force hammer or exciter is used to excite each measuring point in turn, and the force and acceleration signals are collected. The analysis system is used to process the force and acceleration to obtain the acceleration admittance at the foot mounting point of the test stand, and the formula is Y=S aa / S fa , wherein S aa is the self-power spectrum of the acceleration signal when excited, and S fa is the mutual power spectrum of the force signal and the acceleration signal when excited. The measured acceleration admittance is assembled into a matrix Y0.

[0087] (3) The acceleration admittance of the equipment factory installation test stand is obtained by a test test method:

[0088] The acceleration admittance matrix Y p of the equipment factory installation test stand is obtained by the test test method in (2).

[0089] (4) The free acceleration of the equipment foot is obtained by formula calculation:

[0090] The free acceleration a0 of the equipment foot is calculated by the formula a0=(Y p +Y0)·Y p -1 ·a p .

[0091] (5) The structure excitation point force of the ship body is calculated. The structure excitation point is the position where the ship body structure is connected with the lower layer vibration isolator or the position where the ship body structure is directly connected with the equipment.

[0092] a. In the case that the equipment is directly installed on the ship body structure, the calculation process is as follows:

[0093] (a-1) The acceleration admittance of the ship body structure excitation point is obtained by a numerical calculation method.

[0094] The finite element model of the ship body structure is established, the excitation points of the ship body structure are numbered in turn, and a unit point force load is applied, and the acceleration response results of each excitation point are calculated, that is, the acceleration admittance of the equipment installation point of the installation foundation structure, which is assembled into a matrix D.

[0095] (a-2) The ship body structure excitation point force is calculated by formula.

[0096] The ship body structure excitation point force F is calculated by the formula F=(D+Y0) -1 ·a f .

[0097] b. In the case of the equipment mounted on the ship structure by the isolator floating raft, the calculation process is as follows:

[0098] (b-1) The acceleration impedance of the upper isolator group is obtained by the test means.

[0099] The isolator is placed on the impedance platform, the lower end is clamped on the force plate, the upper end is connected to the impedance head, the force sensor in the impedance head is connected to the exciter, the exciter is connected to the signal generator through the power amplifier, and the force plate and the impedance head are connected to the data acquisition system. Turn on the signal generator, the exciter excites the isolator, the data acquisition system collects the signal, and after the collection is completed, the signal generator is turned off. The isolator is removed, and the isolator is installed in reverse, the upper end is clamped on the force plate, and the lower end is connected to the impedance head. The acceleration impedance test is carried out. After the data acquisition is completed, the data analysis system is used for analysis and processing to obtain the acceleration impedance Z u11 , Z u12 , Z u21 , Z u22 of the isolator. The formula is Z=S ff / S fa , wherein S ff is the self-power spectrum of the force signal when excited, and S fa is the cross-power spectrum of the force signal and the acceleration signal.

[0100] (b-2) The acceleration impedance of the lower isolator group is obtained by the test means.

[0101] The test means in (b-1) is used to test the acceleration impedance Z d11 , Z d12 , Z d21 , Z d22 of the lower isolator.

[0102] (b-3) The admittance of the floating raft is obtained by numerical calculation.

[0103] A finite element model of the floating raft is established, and the upper isolator mounting points of the floating raft are numbered in sequence: 1, 2, …, n, n is the number of upper isolators, and the lower isolator mounting points of the floating raft are numbered in sequence: n+1, n+2, …, n+m, m is the number of lower isolators. A unit point force load is applied to each measuring point in sequence, and the acceleration response result of each measuring point is calculated, that is, the acceleration admittance of the floating raft, which is assembled into a matrix Y b .

[0104] (b-4) The acceleration admittance of the ship structure excitation point is obtained by numerical calculation.

[0105] A finite element model of the hull structure is established, the excitation points of the hull structure are numbered sequentially, and a unit point force load is applied. The acceleration response results of each excitation point are calculated, which are the acceleration admittances of the installation points of the foundation structure equipment. These are then assembled into matrix D.

[0106] (b-5) Calculate the admittance of the mounting foundation under the equipment feet.

[0107] Through formula Y g =Z u22 / (Z u11 ·Z u22 -Z u12 ·Z u21 Y is calculated using the formula )·I. g I is an n-order identity matrix.

[0108] (b-6) The transfer matrix of the upper vibration isolator is obtained from the acceleration impedance of the upper vibration isolator group.

[0109] Let Z u11 =Z u11 ·I, Z u12 =Z u12 ·I, Z u21 =Z u21 ·I, Z u22 =Z u22 • I, where I is an n-order identity matrix. The transfer matrix A of the upper vibration isolator can be calculated using the following formula:

[0110]

[0111] (b-7) The transfer matrix of the lower vibration isolator is obtained from the acceleration impedance of the lower vibration isolator group.

[0112] Let Z d11 =Z d11 ·I, Z d12 =Z d12 ·I, Z d21 =Z d21 ·I, Z d22 =Z d22 • I, where I is an m-order identity matrix. The transfer matrix C of the upper vibration isolator can be calculated using the following formula:

[0113]

[0114] (b-8) Obtain the raft transfer matrix from the raft acceleration admittance.

[0115] Floating raft acceleration admittance make

[0116]

[0117]

[0118]

[0119]

[0120] The floating raft transfer matrix B can be calculated by the following formula:

[0121]

[0122] (b-9) The equipment foot input force is calculated by the formula.

[0123] The equipment foot input force G is calculated by the formula G = (Y g + Y0) -1 · a f

[0124] (b-10) The ship structure excitation point force is calculated by the formula.

[0125] The matrices A, B, and C can be represented as follows:

[0126]

[0127] The new matrix T is obtained by multiplying A, B, and C, and the matrix T can be represented in a similar form:

[0128]

[0129] The ship structure excitation force F is calculated by the formula F = (T 11 + T 12 · D) -1 · G.

[0130] (6) The transfer function of the ship structure response point acceleration to the ship structure excitation point force is obtained by numerical calculation.

[0131] A finite element model of the ship structure is established, and unit point force loads are applied to the excitation points of the ship structure in sequence. The acceleration results of each response point are calculated, which are the transfer functions of the ship structure response point acceleration to the ship structure excitation point force. These are assembled into a matrix L.

[0132] (7) The ship structure response point acceleration is calculated by the formula.

[0133] The ship structure response point acceleration a d is calculated by the formula a d .

[0134] ​The calculation result obtained by the calculation method of the present application is obviously more accurate than the theoretical value of the factory foot acceleration because the inevitable influence of the engine is considered by using the free acceleration of the foot to substitute the calculation.

[0135] The above description is an explanation of the present application, not a limitation of the application, the scope of the present application is defined in the claims, within the protection scope of the present application, any form of modification can be made.

Claims

1. A method of calculating the excitation of a ship's hull vibration by a device, characterized by: It comprises the following steps: Acquisition of device out-of-the-box acceleration a p , Obtaining the acceleration mobility Y0 of the equipment feet, Obtaining the acceleration mobility Y of a factory installation bench of a device p , Obtaining the free acceleration a0 of the equipment feet by the above parameters, Judging whether the equipment is directly installed on the hull structure or installed on the hull structure through the vibration isolator and the raft, If the equipment is directly installed on the hull structure, obtaining the acceleration mobility matrix D of the excitation point of the hull structure, and calculating the excitation force F through the matrix, If the equipment is installed on the hull structure through the isolator, the upper isolator acceleration impedance Z u , the raft acceleration admittance Y b , the lower isolator group acceleration impedance Z d , the hull structure excitation point acceleration admittance D, through these parameters to obtain the matrix A, B, C, Y g , the equipment foot input force G is calculated, the excitation force F is calculated, After the excitation force F is calculated, obtaining the transfer function L, The ship body structure response point acceleration A is calculated by the transfer function d .

2. A method of calculating the excitation of a ship's hull vibrations by a device as claimed in claim 1, characterized in that: Factory device foot acceleration a p The acquisition step is as follows: The device is directly installed on the rack, the acceleration sensor is arranged at the device foot position and numbered, the acceleration sensor is connected with the data acquisition and analysis system, after the installation is completed, the device is started, the acceleration at each measuring point is collected, and a matrix a is assembled p .

3. A method of calculating the excitation of a ship's hull vibrations by a device as claimed in claim 1, characterized in that: The steps of obtaining the acceleration mobility Y0 of the equipment feet are as follows: The equipment is hoisted by elastic ropes, the acceleration sensor is arranged at the foot mounting point of the rack, each measuring point is numbered, the force hammer or exciter, the acceleration sensor and the data acquisition and analysis system are connected, After installation, force hammer or exciter to stimulate each measuring point in turn, and collect force and acceleration signals, and use analysis system to process force and acceleration to obtain acceleration mobility at the installation point of the machine foot of the rack, formula Y=S aa / S fa , where S aa is the auto-power spectrum of the acceleration signal at the excitation, S fa is the cross-power spectrum of the force and acceleration signals at the excitation, The measured acceleration mobility is assembled into a matrix Y0.

4. A method of calculating the excitation of a ship's hull vibrations by a device as claimed in claim 1, characterized in that: Acceleration admittance Y of the device installation bench at factory p The acquisition step is as follows: The equipment is hoisted by elastic ropes, the acceleration sensor is arranged at the foot mounting point of the rack, each measuring point is numbered, the force hammer or exciter, the acceleration sensor and the data acquisition and analysis system are connected, After installation, force hammer or exciter to stimulate each measuring point in turn, and collect force and acceleration signals, and use analysis system to process force and acceleration to obtain acceleration mobility at the installation point of the machine foot of the rack, formula Y=S aa / S fa , where S aa is the auto-power spectrum of the acceleration signal at the excitation, S fa is the cross-power spectrum of the force and acceleration signals at the excitation, Assemble the measured acceleration admittance into a matrix Y p .

5. A method of calculating the excitation of a ship's hull vibrations by a device as claimed in claim 1, characterized in that: The formula for calculating the free acceleration a0 of the equipment feet is as follows: a0 = (Y p + Y0) · Y p -1 · a p .

6. A method of calculating the vibration of a ship's hull under the excitation of a device as claimed in claim 1, characterized in that: The steps of calculating the excitation force of the equipment directly installed on the hull structure are as follows: The acceleration mobility of the excitation point of the hull structure is obtained by numerical calculation, A finite element model of the hull structure is established, the excitation points of the hull structure are numbered in turn, and a unit point force load is applied, the acceleration response results of each excitation point are calculated, that is, the acceleration mobility of the installation foundation structure equipment installation point, which is assembled into a matrix D, The point force F on the ship structure is calculated by the formula F = (D + Y0) -1 ·a f The point force F on the ship structure is calculated by the formula F = (D + Y0) 7. A method of calculating the vibration of a ship's hull under the excitation of a device as claimed in claim 1, characterized in that: The steps of calculating the exciting point force of the equipment mounted on the hull structure by the isolator buoyant raft are as follows: obtaining the acceleration impedance Z of the upper isolator group by the experimental test means u , The vibration isolator is placed on the impedance platform, the lower end is clamped on the force plate, and the upper end is connected to the impedance head, the force sensor in the impedance head is connected to the exciter, the exciter is connected to the power amplifier and the signal generator through the power amplifier, and the force plate and the impedance head are connected to the data acquisition system, The signal generator is turned on, the exciter excites the vibration isolator, and the data acquisition system collects the signal, After the collection is completed, the signal generator is turned off, The vibration isolator is removed and installed in reverse, the upper end is clamped on the force plate, and the lower end is connected to the impedance head, The acceleration impedance test is performed, After the data acquisition is completed, the acceleration impedance Z of the vibration isolator is obtained by using a data analysis system to analyze and process u11 u12 u21 u22 ,​​​ Impedance is calculated by the formula Z = S ff / fa where S ff is the auto-power spectrum of the force signal during excitation, S fa is the cross-power spectrum between the force signal during excitation and the acceleration signal. The acceleration impedance Z of the lower vibration isolator group is obtained by means of test testing d and the acceleration impedance measured multiple times is denoted by Z d11 , Z d12 , Z d21 , Z d22 , A finite element model of the raft is established, and the installation points of the upper layer vibration isolators of the raft are numbered in sequence: 1, 2, …, n, n being the number of the upper layer vibration isolators, and the installation points of the lower layer vibration isolators of the raft are numbered in sequence: n+1, n+2, …, n+m, m being the number of the lower layer vibration isolators, and a unit point force load is applied to each measuring point in sequence, and the acceleration response results of each measuring point are calculated, that is, the acceleration admittance of the raft, which is assembled into a matrix Y b , A finite element model of the hull structure is established, the excitation points of the hull structure are numbered in turn, and a unit point force load is applied, the acceleration response results of each excitation point are calculated, that is, the acceleration mobility of the installation foundation structure equipment installation point, which is assembled into a matrix D.

8. A method of calculating the vibration of a ship's hull under the excitation of a device as claimed in claim 7, characterized in that: The steps of calculating the mobility of the installation foundation under the equipment feet are as follows: Y = Z g = Z u22 · Z u11 · Z u22 · Z u12 · Z u21 · I g , I being the n-order identity matrix, The upper layer vibration isolator transfer matrix is obtained from the acceleration impedance of the upper layer vibration isolator group, Let Z u11 = Z u11 · I, Z u12 = Z u12 · I, Z u21 = Z u21 · I, Z u22 = Z u22 · I, I is an n-order unit matrix, and the transfer matrix A of the upper vibration isolator can be calculated by the following formula: The lower layer vibration isolator transfer matrix is obtained from the acceleration impedance of the lower layer vibration isolator group, Let Z d11 = Z d11 · I, Z d12 = Z d12 · I, Z d21 = Z d21 · I, Z d22 = Z d22 · I, I is an m-order unit matrix, and the transfer matrix C of the upper vibration isolator can be calculated by the following formula: The raft transfer matrix B is calculated by the following formula: Buoyant Acceleration Admittance Let The matrices A, B and C are represented in the following form:

9. A method of calculating the vibration of a ship's hull under the excitation of a device as claimed in claim 1, characterized in that: The device foot input force G is calculated by the formula G = (Y g + Y0) -1 · a f The device foot input force G is calculated by the formula G = (Y The new matrix T is obtained by multiplying A, B and C, and the matrix T is represented in the similar form: The steps of obtaining the transfer function of the hull structure response point acceleration ratio the hull structure excitation force by numerical calculation are as follows: The ship body structure exciting force F is calculated by the formula F = (T 11 + T 12 · D) -1 · G.

10. A method of calculating the vibration of a ship's hull under the excitation of a device as claimed in claim 9, characterized in that: ​ A finite element model of the ship structure is established, and unit point force loads are applied to the excitation points of the ship structure in sequence. The acceleration results of the response points are calculated, i.e. the transfer functions of the acceleration of the response points of the ship structure to the force of the excitation points of the ship structure. The transfer functions are assembled into a matrix L, The ship structure response point a is calculated by the formula a d = L · F d .

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