CN117288155A - Working method of in-situ observation equipment based on seabed sliding process - Google Patents
Working method of in-situ observation equipment based on seabed sliding process Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 79
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- 238000007781 pre-processing Methods 0.000 claims description 6
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- 238000012935 Averaging Methods 0.000 claims description 3
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C5/00—Measuring height; Measuring distances transverse to line of sight; Levelling between separated points; Surveyors' levels
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B21/00—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant
- G01B21/02—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant for measuring length, width, or thickness
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L11/00—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
- G01P15/18—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration in two or more dimensions
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
- G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/42—Determining position
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- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
- Y02A90/30—Assessment of water resources
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Abstract
The invention provides a working method of in-situ observation equipment based on a seabed sliding process, which comprises an upper measuring device and a lower fixing device, wherein the in-situ long-term observation of the seabed sliding process can be realized by adopting a mode of assisting the release of a ship water surface unhook and the manual recovery of GPS positioning in deployment and recovery. According to the technical scheme, the in-situ observation equipment for the seabed sliding process can be independently arranged, the high water pressure effect in the deep sea environment is effectively overcome, the power supply device can supply power for the acquisition and storage system for a long time under water, conditions are provided for long periodicity of in-situ observation, the purpose of long-term observation of the seabed long-length sliding process is achieved, and the displacement of the seabed moving along all directions is accurately measured. By arranging the parts such as the acoustic releaser, the glass floating ball and the like, the device is recovered and reused, the characteristic of recycling is achieved, and the observation cost can be greatly saved.
Description
Technical Field
The invention relates to the field of marine geological disaster observation, in particular to a working method of in-situ observation equipment based on a seabed sliding process.
Background
In recent years, development of ocean resources and ocean engineering construction are continuously advanced, and it is very important to ensure safety and stability of various ocean structures. In this context, seabed slip is becoming increasingly important as an important factor in inducing structural instability. The sliding of the seabed can cause problems of pipeline suspension and even fracture, or platform instability and even capsizing, and the like, so that serious life and property loss and potential marine environment disasters are caused. The sea bed sliding process is researched, and the method has important significance for solving the problem of stability of ocean engineering foundation, predicting occurrence of geological disasters and the like.
At present, the soil body sliding observation technology applied to land is very mature at home and abroad, and is widely applied to the field of land engineering, and deformation displacement is monitored mainly by optical fibers and displacement sensors. However, the difficulty of the observation technology in the process of seabed sliding in deep sea is high, and the difficulty and the hot spot of current ocean geological disaster research are already becoming.
Disclosure of Invention
In order to make up the defects of the prior art, the invention provides a working method of in-situ observation equipment based on a seabed sliding process, which comprises an upper measuring device and a lower fixing device, wherein the arrangement and recovery adopts a mode of assisting the release of a ship water surface unhook and the manual recovery of GPS positioning, and can realize the long-term in-situ observation of the seabed sliding process.
The invention is realized by the following technical scheme: the utility model provides a sea bed slip process normal position observation equipment, including measuring device and the fixing device of lower part in upper portion, the outside of observation device is the shell, inside is the pressure-bearing glass cabin, cabin body mid-mounting in pressure-bearing glass cabin has middle part fixed plate and bottom fixed plate, high accuracy triaxial acceleration sensor is run through in the middle part of middle part fixed plate, high accuracy triaxial acceleration sensor's top is provided with pressure sensor, the lower surface mounting of bottom fixed plate has collection storage control system, the upper surface mounting of middle part fixed plate has underwater sound communication device and chargeable battery, unhook mechanism is equipped with on the top of shell, be provided with collection storage control system reservation connector on the pressure-bearing glass cabin outer wall, underwater sound communication device reservation connector, battery reservation connector and fuse device reservation connector;
the fixing device comprises a mounting plate, a counterweight bracket and 5 supporting feet, wherein the counterweight bracket is a square frame, the mounting plate is fixedly mounted at the central position of the upper surface of the counterweight bracket, the mounting plate is connected with the measuring device and the fixing device, and the supporting feet are fixedly mounted at the central position and four corners of the lower surface of the counterweight bracket;
the method specifically comprises the following steps:
s1, assembling a measuring device and a fixing device, connecting the measuring device and the fixing device with observation equipment by using a PC end, and inputting acquisition frequency and acquisition time length;
s2, opening the auxiliary ship to a target point by using a GPS positioning system of the auxiliary ship, lowering equipment to the sea surface by using a cable car on the auxiliary ship, unhooking and releasing, sinking the equipment to the surface of the seabed by self weight, and inserting support legs of the fixing device into the seabed to enable the equipment to move along with the seabed;
s3, starting data acquisition by the high-precision triaxial acceleration sensor and the pressure sensor in the equipment according to the set acquisition frequency and the set acquisition duration;
s4, after in-situ observation is finished, the auxiliary ship is opened to a target point, the acoustic-pass deck unit sends a release instruction, the acoustic-pass underwater part receives a signal and transmits the signal to the control unit, the control unit transmits the instruction to the unhooking mechanism, the unhooking mechanism works to fuse the fuse, the equipment is separated from the fixing device, and the equipment floats to the water surface through self buoyancy;
s5, the PC end is connected with an observation device through a watertight connector, triaxial acceleration data and pressure data in the seabed sliding process are read, and displacement change data in the seabed sliding process are obtained after data processing is carried out;
the method specifically comprises the following steps:
s5-1, preprocessing an acceleration signal: preprocessing by removing background acceleration, direct current components, low-pass filtering and the like to obtain preprocessed acceleration signals; the method for removing the background acceleration and the direct current component is to remove the original signal of the acceleration through a detrend function in MATLAB; the low-pass filtering is to firstly determine the effective frequency of the acceleration signal through Estimatenase function in MATLAB, and then design a low-pass filter through button and filter function in MATLAB to carry out low-pass filtering;
s5-2, determining the optimal cut-off frequency by using a PSD estimation method; calculating the PSD of the acceleration signal by adopting a Welch method, estimating the PSD of the signal, and selecting the optimal cut-off frequency; the method specifically comprises the following steps:
for signal x (t), it is divided into N overlapping segments, each segment having a length L and an overlapping length M; the start time of the nth segment is:
the termination time of the nth segment is:
thus, the time range of the nth segment is:
for each segment, windowing it using a window function w (t);
performing fast Fourier transform on each segment according to the formula (1), and obtaining the power spectral density of each frequency point; averaging the power spectrum density of each frequency point to obtain the PSD of the whole signal; according to the PSD result, selecting an optimal cut-off frequency, and generally selecting a frequency corresponding to a frequency spectrum peak value as the optimal cut-off frequency;
formula (1)
In the method, in the process of the invention,representing a frequency domain signal, representing the intensity or amplitude of the signal at each frequency; />Values representing the signal at various points in time; />The angular frequency is represented, and the speed of signal change is represented;
s5-3, frequency domain integration: the extracted cut-off frequency is applied to the acceleration frequency domain integration process, a speed signal is obtained through primary integration, and a displacement signal is obtained through secondary integration; then converting them into time domain signals by inverse fourier transform;
s5-4, outputting a displacement signal to obtain displacement data;
s5-5, converting the pressure data into height data according to a formula (11) in the process of processing the pressure data to obtain h, and taking all the height data to averageSubtracting an average value from the original height data according to a formula (12) to obtain the height change, wherein P is the pressure intensity, ρ is the sea water density, g is the gravity acceleration of an observation point, and h is the distance between the pressure sensor and the sea water surface;
=ρgh equation (11)
Formula (12)
S5-6, performing fast Fourier transform on the height change data according to a formula (1), determining an initial frequency according to a spectrogram obtained by Fourier transform, performing tidal correction by using a low-pass filter to remove interference of tidal signals, and performing wave correction by subtracting displacement change acquired and calculated by using an acceleration sensor from the obtained data;
s5-7, fitting the tide and wave corrected data according to a formula (13), and subtracting a drift value obtained by fitting from the original data to obtain a corrected seabed height change curve, namely a displacement result.
𝑃(𝑡) = 𝐴 1 exp(−𝐴 2 𝑡) + 𝐴 3 𝑡+ 𝐴 4 Formula (13)
Wherein the method comprises the steps of𝐴 𝑖 Is a free parameter determined by a non-linear fit,𝑡in order to be able to take time,𝑃(𝑡) Is that𝑡The pressure corresponding to the moment.
Preferably, the maximum pressure-resistant depth of the pressure-bearing glass cabin (12) is 6000 m.
Preferably, the rechargeable battery pack (18) is a lithium-ion battery, voltage 7.2V, capacity 236 Ah.
As a preferable scheme, the shell (11) is made of ABS engineering plastics.
Preferably, the fixing device (2) is made of 316L steel.
Preferably, the step S5-3 specifically comprises the following steps: according to the definition of velocity, the velocity is equal to the displacement divided by the time; assuming that the displacement is Δx during the time interval Δt, the velocity is:
formula (2)
The time interval Deltat can be expressed as the interval between two successive moments i-1 and i, i.e.. Thus, the displacement Δx can be expressed as:
formula (3)
Substituting the two formulas into the formula (2) of the speed to obtain:
formula (4)
Acceleration over a time interval may be expressed asI.e. the acceleration is equal to the rate of change of the speed. Substituting it into the definition formula of the speed, obtain:
formula (5)
Since the time interval Δt is a fixed value, substituting it into equation (5) and sorting to obtain the final equation:
formula (6)
Where f is the inverse of the time interval Δt, i.e. This formula shows that the average value of the acceleration multiplied by Δt over a time interval Δt is equal to the amount of change in the speed, and the speed at the previous time is added to the speed at the current time.
From the formula of acceleration, can be obtained
Formula (7)
Substituting the formula of displacement into the definition of speed to obtain
Formula (8)
Substituting the velocity in the above formula into the formula of displacement to obtain the final formula
Formula (9)
Performing Fourier inverse transformation on the obtained displacement data according to the formula (10) to obtain a displacement signal
Equation (10).
The invention adopts the technical proposal, and compared with the prior art, the invention has the following beneficial effects: the in-situ observation equipment for the seabed sliding process can be independently distributed, the high water pressure effect in the deep sea environment is effectively overcome, the power supply device can supply power for the acquisition and storage system for a long time under water, conditions are provided for long periodicity of in-situ observation, the purpose of long-term observation of the seabed long-length sliding process is achieved, and the displacement of the seabed moving along all directions is accurately measured. By arranging the parts such as the acoustic releaser, the glass floating ball and the like, the device is recovered and reused, the characteristic of recycling is achieved, and the observation cost can be greatly saved.
Additional aspects and advantages of the invention will be set forth in part in the description which follows, or may be learned by practice of the invention.
Drawings
The foregoing and/or additional aspects and advantages of the invention will become apparent and may be better understood from the following description of embodiments taken in conjunction with the accompanying drawings in which:
FIG. 1 is a schematic diagram of the in-situ observation device for the sliding process of the seabed according to the present invention;
FIG. 2 is a schematic view of the structure of the observation device;
FIG. 3 is a schematic top view of the fixture;
FIG. 4 is a front view of the fixture;
FIG. 5 is a schematic diagram of a long term in situ observation;
fig. 6 is an acceleration change curve. The left graph is the original data, and the right graph is the graph after other influencing factors are removed;
figure 7 is a fourier transform spectrum diagram,
wherein, the correspondence between the reference numerals and the components in fig. 1 to 4 is:
1 observation device, 11ABS engineering plastic shell, 12 pressure-bearing glass cabin, 13 middle fixing plate, 14 bottom fixing plate, 151 high-precision triaxial acceleration sensor, 152 pressure sensor, 16 acquisition and storage control system, 161 acquisition and control system reserved connector, 17 underwater sound communication device, 171 underwater sound communication reserved connector, 18 chargeable battery pack, 181 battery pack reserved connector, 19 unhook mechanism, 191 unhook mechanism reserved connector.
Detailed Description
In order that the above-recited objects, features and advantages of the present invention will be more clearly understood, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description. It should be noted that, in the case of no conflict, the embodiments of the present application and the features in the embodiments may be combined with each other.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced otherwise than as described herein, and therefore the scope of the present invention is not limited to the specific embodiments disclosed below.
The method of operation of the in-situ observation device based on a seabed slip process according to the embodiment of the present invention will be described in detail with reference to fig. 1 to 7.
The invention provides in-situ observation equipment for a seabed sliding process, which is shown in fig. 1 and comprises an upper measuring device 1 and a lower fixing device 2, wherein the outside of the observation device 1 is a shell 11, and the shell 11 is ABS engineering plastic and plays a role in protecting equipment from collision as shown in fig. 2; the interior is a pressure-bearing glass cabin 12, the maximum pressure-bearing depth of the pressure-bearing glass cabin 12 is 6000 meters, and the pressure-bearing glass cabin has the functions of protecting internal components of the cabin body from being damaged by water pressure in a deep sea environment and smoothly floating after the counterweight bracket is discarded; the middle part of the cabin body of the pressure-bearing glass cabin 12 is provided with a middle fixing plate 13 and a bottom fixing plate 14, which play a role in fixing each component and limiting the movement of the component; the middle part of the middle fixing plate 13 is provided with a high-precision triaxial acceleration sensor 151 in a penetrating manner, a pressure sensor 152 is arranged above the high-precision triaxial acceleration sensor 151, the lower surface of the bottom fixing plate 14 is provided with an acquisition and storage control system 16, the working state of the sensor can be controlled, and acceleration signals and pressure signals are acquired and stored; the upper surface of the middle fixing plate 13 is provided with an underwater sound communication device 17 and a rechargeable battery pack 18, and the underwater sound communication device 17 can receive instructions sent by the shipboard deck unit to the observation equipment; the rechargeable battery pack 18 is a lithium-ion battery, has the voltage of 7.2V and the capacity of 236 Ah, and can be used for continuous operation of equipment for 60 days, so that the purpose of in-situ long-term observation is realized. The top of the shell 11 is provided with a unhooking mechanism 19 which is used for unhooking and releasing according to the floating instruction received by the underwater acoustic communication device 17 after long-term observation is finished, so that the observation device is separated from the fixing device for floating recovery; the outer wall of the pressure-bearing glass cabin 12 is provided with an acquisition and storage control system reserved connector 161, an underwater sound communication device reserved connector 171, a battery pack reserved connector 181 and a fusing device reserved connector 191, the acquisition and storage control system reserved connector 161 is communicated with a PC end to realize the functions of acquisition parameter setting and data reading, and the battery pack reserved connector 181 can realize the rapid charging of the rechargeable battery pack 18;
as shown in fig. 3, the fixing device 2 is a top view, and fig. 4 shows a front view of the fixing device 2, where the fixing device 2 includes a mounting plate 21, a counterweight bracket 22 and 5 supporting legs 23, and the fixing device 2 is made of 316L steel. The counterweight support 22 is a square frame, and the counterweight support 22 has the functions of supporting the observation device and enabling the observation device to sink smoothly in the deep sea; the mounting plate 21 is fixedly arranged at the center of the upper surface of the counterweight bracket 22, the mounting plate 21 is connected with the measuring device 1 and the fixing device 2, and the mounting plate 21 can increase the contact area between the observing device and the fixing device, so that the observing device and the fixing device have better coupling effect; the center position and four corners of the lower surface of the counterweight bracket 22 are fixedly provided with supporting legs 23, so that the equipment can be tightly adhered to the seabed and can move along with the seabed;
as shown in fig. 5, a long-term in-situ observation demonstration diagram of the in-situ observation device in the seabed sliding process specifically comprises the following steps:
s1, assembling a measuring device 1 and a fixing device 2, connecting observation equipment by using a PC end, and inputting acquisition frequency and acquisition duration;
s2, opening the auxiliary ship to a target point by using a GPS positioning system of the auxiliary ship, lowering equipment to the sea surface by using a cable car on the auxiliary ship, unhooking and releasing, sinking the equipment to the surface of the seabed by self weight, and inserting supporting legs (23) of the fixing device (2) into the seabed to enable the equipment to move along with the seabed;
s3, starting data acquisition by a high-precision triaxial acceleration sensor (151) and a pressure sensor (152) in the equipment according to the set acquisition frequency and the set acquisition duration;
s4, after in-situ observation is finished, the auxiliary ship is opened to a target point, the acoustic-pass deck unit sends a release instruction, the acoustic-pass underwater part receives a signal and transmits the signal to the control unit, the control unit transmits the instruction to the unhooking mechanism, the unhooking mechanism works to fuse the fuse, the equipment is separated from the fixing device, and the equipment floats to the water surface through self buoyancy; the salvage of equipment is assisted by a ship and staff;
s5, the PC end is connected with an observation device through a watertight connector, triaxial acceleration data and pressure data in the seabed sliding process are read, and displacement change data in the seabed sliding process are obtained after data processing is carried out;
the device is used for observing the seabed sliding process, acquiring data and then processing the data.
In the processing of pressure data for near shallow sea, there are the following difficulties: (1) The marine signal makes the pressure record noisy, and the pressure data can not be reliably converted into water depth data; (2) The original data processing method for in-situ observation of the pressure sensor has limitation in the shallow sea.
In order to solve the existing problems, a new method is provided in the data processing process to adapt to the requirements of near-shallow sea pressure data processing. The method specifically comprises the following steps:
s5-1, preprocessing an acceleration signal: preprocessing by removing background acceleration, direct current components, low-pass filtering and the like to obtain preprocessed acceleration signals; the method for removing the background acceleration and the direct current component is to remove the original signal of the acceleration through a detrend function in MATLAB; the low-pass filtering is to firstly determine the effective frequency of the acceleration signal through Estimatenase function in MATLAB, and then design a low-pass filter through button and filter function in MATLAB to carry out low-pass filtering;
the operation codes of the steps are as follows:
removing the background acceleration and the direct current component through a detrend function in MATLAB, wherein the fourth behavior calls the detrend function,
t=xlsread('t.xlsx');
acc_x=xlsread('accx.xlsx');
za=detrend(acc_x);
figure
plot(t,za)
xlabel time/s
yabel acceleration
Reading acceleration data, converting into vectors, calling Estimatenase function, returning to effective frequency,
data = xlsread('accx.xlsx');
vector = data(:, 1);
estimatenoise(vector)
ans =0.0038
reading acceleration data, calling button and filter functions, designing a low-pass filter, performing low-pass filtering,
fs=1/1200%
T=1/fs;
L=26;
t=(0:L-1)*T;
A=xlsread(accx.xlsx');
y=A(:,1);
fc=0.0038;
wn=2*fc/fs;
[b,a]=butter(4,wn,'low');
y1=filter(b,a,y);
y2=y1(end:-1:1);
y3=filter(b,a,y2);
y4=y3(end:-1:1)
figure();plot(t,y4);hold on;plot(t,y)
xlabel('Time');ylabel('Amplitude')
xlswrite('afterButter.xlsx',y4);
The removal results are shown in fig. 6;
s5-2, determining an optimal cut-off frequency by using a PSD estimation method (PSD, power Spectral density, power spectral density); calculating the PSD of the acceleration signal by adopting a Welch method, estimating the PSD of the signal, and selecting the optimal cut-off frequency; the method specifically comprises the following steps:
for signal x (t), it is divided into N overlapping segments, each segment having a length L and an overlapping length M; the start time of the nth segment is:
the termination time of the nth segment is:
thus, the time range of the nth segment is:
for each segment, windowing it using a window function w (t);
performing fast Fourier transform on each segment according to the formula (1), and obtaining the power spectral density of each frequency point; averaging the power spectrum density of each frequency point to obtain the PSD of the whole signal; according to the PSD result, selecting an optimal cut-off frequency, and generally selecting a frequency corresponding to a frequency spectrum peak value as the optimal cut-off frequency;
formula (1)
In the method, in the process of the invention,representing a frequency domain signal, representing the intensity or amplitude of the signal at each frequency; />Values representing the signal at various points in time; />The angular frequency is represented, and the speed of signal change is represented;
s5-3, frequency domain integration: the extracted cut-off frequency is applied to the acceleration frequency domain integration process, a speed signal is obtained through primary integration, and a displacement signal is obtained through secondary integration; then converting them into time domain signals by inverse fourier transform; the method specifically comprises the following steps: according to the definition of velocity, the velocity is equal to the displacement divided by the time; assuming that the displacement is Δx during the time interval Δt, the velocity is:
formula (2)
The time interval Deltat can be expressed as the interval between two successive moments i-1 and i, i.e.. Thus, the displacement Δx can be expressed as:
formula (3)
Substituting the two formulas into the formula (2) of the speed to obtain:
formula (4)
Acceleration over a time interval may be expressed asI.e. the acceleration is equal to the rate of change of the speed. Substituting it into the definition formula of the speed, obtain:
formula (5)
Since the time interval Δt is a fixed value, substituting it into equation (5) and sorting to obtain the final equation:
formula (6)
Where f is the inverse of the time interval Δt, i.e. This formula shows that the average value of the acceleration multiplied by Δt is equal to the variation of the speed over the time interval ΔtThe speed at the current time is obtained by adding the speed at the previous time.
From the formula of acceleration, can be obtained
Formula (7)
Substituting the formula of displacement into the definition of speed to obtain
Formula (8)
Substituting the velocity in the above formula into the formula of displacement to obtain the final formula
Formula (9)
Performing Fourier inverse transformation on the obtained displacement data according to the formula (10) to obtain a displacement signal
Equation (10).
S5-4, outputting a displacement signal to obtain displacement data;
s5-5, converting the pressure data into height data according to a formula (11) in the process of processing the pressure data to obtain h, and taking all the height data to averageThen subtracting the average value from the original height data according to the formula (12) to obtain the height change, so that the interference of instantaneous observation data is reduced; wherein P is pressure, ρ is sea water density, g is gravitational acceleration of the observation point, and h is distance between the pressure sensor and sea water surface;
=ρgh equation (11)
Formula (12)
S5-6, performing fast Fourier transform on the height change data according to a formula (1), determining an initial frequency according to a spectrogram obtained by Fourier transform, performing tidal correction by using a low-pass filter to remove interference of tidal signals, and performing wave correction by subtracting displacement change acquired and calculated by using an acceleration sensor from the obtained data;
s5-7, fitting the tide and wave corrected data according to a formula (13), and subtracting a drift value obtained by fitting from the original data to obtain a corrected seabed height change curve, namely a displacement result.
𝑃(𝑡) = 𝐴 1 exp(−𝐴 2 𝑡) + 𝐴 3 𝑡+ 𝐴 4 Formula (13)
Wherein the method comprises the steps of𝐴 𝑖 Is a free parameter determined by a non-linear fit,𝑡in order to be able to take time,𝑃(𝑡) Is that𝑡The pressure corresponding to the moment.
In the description of the present invention, the term "plurality" means two or more, unless explicitly defined otherwise, the orientation or positional relationship indicated by the terms "upper", "lower", etc. are based on the orientation or positional relationship shown in the drawings, merely for convenience of description of the present invention and to simplify the description, and do not indicate or imply that the apparatus or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the present invention; the terms "coupled," "mounted," "secured," and the like are to be construed broadly, and may be fixedly coupled, detachably coupled, or integrally connected, for example; can be directly connected or indirectly connected through an intermediate medium. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
In the description of the present specification, the terms "one embodiment," "some embodiments," "particular embodiments," and the like, mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (6)
1. The working method of the in-situ observation equipment for the seabed sliding process is characterized in that the in-situ observation equipment for the seabed sliding process comprises an upper measuring device (1) and a lower fixing device (2), wherein the outside of the observing device (1) is a shell (11), the inside of the observing device is a pressure-bearing glass cabin (12), a middle fixing plate (13) and a bottom fixing plate (14) are arranged in the middle of a cabin body of the pressure-bearing glass cabin (12), a high-precision triaxial acceleration sensor (151) is arranged in the middle of the middle fixing plate (13) in a penetrating manner, a pressure sensor (152) is arranged above the high-precision triaxial acceleration sensor (151), an acquisition and storage control system (16) is arranged on the lower surface of the bottom fixing plate (14), an underwater sound communication device (17) and a chargeable battery pack (18) are arranged on the upper surface of the middle fixing plate (13), a unhooking mechanism (19) is arranged on the top of the shell (11), and an acquisition and storage system reserved connector (161), an underwater sound communication device reserved connector (171), a battery pack reserved connector (181) and a fuse device connector (191) are arranged on the outer wall of the pressure-bearing glass cabin (12);
the fixing device (2) comprises a mounting plate (21), a counterweight bracket (22) and 5 supporting legs (23), wherein the counterweight bracket (22) is a square frame, the mounting plate (21) is fixedly arranged at the center of the upper surface of the counterweight bracket (22), the mounting plate (21) is connected with the measuring device (1) and the fixing device (2), and the supporting legs (23) are fixedly arranged at the center and four corners of the lower surface of the counterweight bracket (22);
the method specifically comprises the following steps:
s1, assembling a measuring device (1) and a fixing device (2), connecting observation equipment by using a PC end, and inputting acquisition frequency and acquisition duration;
s2, opening the auxiliary ship to a target point by using a GPS positioning system of the auxiliary ship, lowering equipment to the sea surface by using a cable car on the auxiliary ship, unhooking and releasing, sinking the equipment to the surface of the seabed by self weight, and inserting supporting legs (23) of the fixing device (2) into the seabed to enable the equipment to move along with the seabed;
s3, starting data acquisition by a high-precision triaxial acceleration sensor (151) and a pressure sensor (152) in the equipment according to the set acquisition frequency and the set acquisition duration;
s4, after in-situ observation is finished, the auxiliary ship is opened to a target point, the acoustic-pass deck unit sends a release instruction, the acoustic-pass underwater part receives a signal and transmits the signal to the control unit, the control unit transmits the instruction to the unhooking mechanism, the unhooking mechanism works to fuse the fuse, the equipment is separated from the fixing device, and the equipment floats to the water surface through self buoyancy;
s5, the PC end is connected with an observation device through a watertight connector, triaxial acceleration data and pressure data in the seabed sliding process are read, and displacement change data in the seabed sliding process are obtained after data processing is carried out;
the method specifically comprises the following steps:
s5-1, preprocessing an acceleration signal: preprocessing by removing background acceleration, direct current components, low-pass filtering and the like to obtain preprocessed acceleration signals; the method for removing the background acceleration and the direct current component is to remove the original signal of the acceleration through a detrend function in MATLAB; the low-pass filtering is to firstly determine the effective frequency of the acceleration signal through Estimatenase function in MATLAB, and then design a low-pass filter through button and filter function in MATLAB to carry out low-pass filtering;
s5-2, determining the optimal cut-off frequency by using a PSD estimation method; calculating the PSD of the acceleration signal by adopting a Welch method, estimating the PSD of the signal, and selecting the optimal cut-off frequency; the method specifically comprises the following steps:
for signal x (t), it is divided into N overlapping segments, each segment having a length L and an overlapping length M; the start time of the nth segment is:
the termination time of the nth segment is:
thus, the time range of the nth segment is:
for each segment, windowing it using a window function w (t);
performing fast Fourier transform on each segment according to the formula (1), and obtaining the power spectral density of each frequency point; averaging the power spectrum density of each frequency point to obtain the PSD of the whole signal; according to the PSD result, selecting an optimal cut-off frequency, and generally selecting a frequency corresponding to a frequency spectrum peak value as the optimal cut-off frequency;
formula (1)
In the method, in the process of the invention,representing a frequency domain signal, representing the intensity or amplitude of the signal at each frequency; />Values representing the signal at various points in time; />The angular frequency is represented, and the speed of signal change is represented;
s5-3, frequency domain integration: the extracted cut-off frequency is applied to the acceleration frequency domain integration process, a speed signal is obtained through primary integration, and a displacement signal is obtained through secondary integration; then converting them into time domain signals by inverse fourier transform;
s5-4, outputting a displacement signal to obtain displacement data;
s5-5, converting the pressure data into height data according to a formula (11) in the process of processing the pressure data to obtain h, and taking all the height data to averageSubtracting an average value from the original height data according to a formula (12) to obtain the height change, wherein P is the pressure intensity, ρ is the sea water density, g is the gravity acceleration of an observation point, and h is the distance between the pressure sensor and the sea water surface;
=ρgh equation (11)
Formula (12)
S5-6, performing fast Fourier transform on the height change data according to a formula (1), determining an initial frequency according to a spectrogram obtained by Fourier transform, performing tidal correction by using a low-pass filter to remove interference of tidal signals, and performing wave correction by subtracting displacement change acquired and calculated by using an acceleration sensor from the obtained data;
s5-7, fitting the tide and wave corrected data according to a formula (13), subtracting a drift value obtained by fitting from the original data to obtain a corrected seabed height change curve, namely a displacement result,
𝑃(𝑡) = 𝐴 1 exp(−𝐴 2 𝑡) + 𝐴 3 𝑡 + 𝐴 4 formula (13)
Wherein the method comprises the steps of𝐴 𝑖 Is a free parameter determined by a non-linear fit,𝑡in order to be able to take time,𝑃(𝑡) Is that𝑡The pressure corresponding to the moment.
2. A method of operating a seabed sliding process based in situ observation device according to claim 1, wherein the pressure-bearing glass capsule (12) has a maximum pressure-resistant depth of 6000 meters.
3. The method of operation of a seabed slip process based in situ observation device according to claim 1, wherein the rechargeable battery pack (18) is a lithium ion battery with a voltage of 7.2V and a capacity of 236 Ah.
4. A method of operating a seabed sliding process based in situ observation device according to claim 1, wherein the housing (11) is an ABS engineering plastic.
5. The working method of the in-situ observation equipment based on the seabed sliding process according to claim 1, wherein the fixing device (2) is made of 316L steel.
6. The method according to claim 1, wherein the step S5-3 comprises the following steps: according to the definition of velocity, the velocity is equal to the displacement divided by the time; assuming that the displacement is Δx during the time interval Δt, the velocity is:
formula (2)
The time interval Deltat can be expressed as the interval between two successive moments i-1 and i, i.e.；
Thus, the displacement Δx can be expressed as:
formula (3)
Substituting the two formulas into the formula (2) of the speed to obtain:
formula (4)
Acceleration over a time interval may be expressed asI.e. the acceleration is equal to the rate of change of speed;
substituting it into the definition formula of the speed, obtain:
formula (5)
Since the time interval Δt is a fixed value, substituting it into equation (5) and sorting to obtain the final equation:
formula (6)
Where f is the inverse of the time interval Δt, i.e；
The formula shows that in the time interval delta t, the average value of the acceleration is multiplied by delta t which is equal to the variation of the speed, and the speed at the current moment is obtained by adding the speed at the previous moment;
from the formula of acceleration, can be obtained
Formula (7)
Substituting the formula of displacement into the definition of speed to obtain
Formula (8)
Substituting the velocity in the above formula into the formula of displacement to obtain the final formula
Formula (9)
Performing Fourier inverse transformation on the obtained displacement data according to the formula (10) to obtain a displacement signal
Equation (10).
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