CN115096494B - Large-scale cable-stayed bridge cable force on-line monitoring system - Google Patents
Large-scale cable-stayed bridge cable force on-line monitoring system Download PDFInfo
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- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L5/00—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes
- G01L5/04—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes for measuring tension in flexible members, e.g. ropes, cables, wires, threads, belts or bands
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Abstract
The cable force on-line monitoring system of the large cable-stayed bridge comprises an acceleration sensor, a field acquisition station and a remote monitoring center, wherein the acceleration sensor is arranged on a guy cable of the cable-stayed bridge, a cable force acquisition industrial personal computer and a data integration industrial personal computer are arranged in the field acquisition station, the cable force acquisition industrial personal computer is connected with the acceleration sensor, and the cable force acquisition industrial personal computer and the data integration industrial personal computer are respectively connected with the remote monitoring center; and a cable force acquisition program for acquiring acceleration signals is loaded on the cable force acquisition industrial personal computer, the remote monitoring center is provided with a WEB server and a database server, the cable force acquisition program acquires the acceleration signals and sends the acceleration signals to a bridge acquisition client program loaded by the data integration industrial personal computer in batches, the bridge acquisition client program processes the acceleration signals and calculates cable force in real time, the calculation speed is high, the visualization of dynamic distribution of the cable force of the full bridge can be realized, and convenience is provided for cable force monitoring of the cable-stayed bridge.
Description
Technical Field
The invention relates to the technical field of cable force monitoring, in particular to an online monitoring system for cable force of a large cable-stayed bridge.
Background
With the continuous perfection of the traffic infrastructure in China, more and more large cable-stayed bridges are put into operation. Large cable-stayed bridges generally comprise hundreds of stay cables, and cable force measurement and evaluation are important contents for bridge health monitoring. Different from monitoring of physical quantities such as temperature, displacement, wind speed, strain and the like, the cable force on-line monitoring is more complex in design and implementation. In the bridge operation process, the cable force dynamic change can be caused no matter the stress concentration, corrosion, fatigue and damage of the structure, or the external wind, frost, rain and snow and vehicle passing, and the change can be shown by the vibration mode of the cable. Because the vibration mode of the cable is dynamic, the real-time requirement of bridge health monitoring is hardly met through manual analysis, so that the on-line monitoring has important significance.
The currently used cable force measuring method comprises an oil pressure method, a magnetic flux method, a vibration frequency method and the like, wherein the magnetic flux method and the vibration frequency method are applied to the field of dynamic cable force monitoring, and the vibration frequency method is one of the most widely applied cable force measuring technologies due to the fact that the implementation is simple and the precision basically meets the application requirements.
However, the vibration frequency method-based cable force measurement has several difficulties:
(1) The data volume is huge, the vibration frequency method is to analyze cable force by picking up high-frequency vibration signals of stay cables, the acquisition frequency of the signals is at least more than 50Hz, the number of the stay cables of a large-scale cable-stayed bridge is generally tens of stay cables, and hundreds of stay cables are more, the generated data volume is huge, and the traditional processing method is difficult to meet the requirements;
(2) The vibration mode is complex, the vibration spectrum of the inhaul cable comprises a fundamental frequency and a high-order self-vibration frequency, wherein the fundamental frequency is an intermediate value for calculating the cable force, but for different inhaul cables, the positions, the amplitudes and the forms of the vibration fundamental frequency and the high-order self-vibration frequency are different, so that great difficulty is brought to vibration mode analysis;
(3) The fundamental frequency identification accuracy is low, and due to the influence of factors such as environment and installation conditions, the fundamental frequency in the frequency spectrum is often submerged by noise, and the fundamental frequency cannot be directly identified; meanwhile, because the high-order self-oscillation frequency can be seriously lost or distorted, the fundamental frequency can be calculated only by means of limited high-order self-oscillation frequency, and the success rate is low, the manual identification is the main method at present;
(4) The cable force calculation results are not visual, only a series of values are needed after the cable forces of all the inhaul cables are calculated respectively, the cable force distribution state of the full bridge cannot be visually reflected, and particularly the cable force needs to be calculated dynamically, so that the requirement on the visualization of the cable force distribution is higher.
Disclosure of Invention
The technical problem solved by the invention is to provide an online monitoring system for the cable force of a large cable-stayed bridge, so as to solve the problems in the background technology.
The technical problems solved by the invention are realized by adopting the following technical scheme:
the cable force on-line monitoring system of the large cable-stayed bridge comprises an acceleration sensor, a field acquisition station and a remote monitoring center, wherein the acceleration sensor is arranged on a guy cable of the cable-stayed bridge, a cable force acquisition industrial personal computer and a data integration industrial personal computer are arranged in the field acquisition station, the cable force acquisition industrial personal computer is connected with the acceleration sensor, and the cable force acquisition industrial personal computer and the data integration industrial personal computer are respectively connected with the remote monitoring center; and a cable force acquisition program for acquiring acceleration signals is loaded on the cable force acquisition industrial personal computer, the remote monitoring center is provided with a WEB server and a database server, the cable force acquisition program acquires the acceleration signals and transmits the acceleration signals to a bridge acquisition client program of the data integration industrial personal computer in batches, and the bridge acquisition client program processes the acceleration signals to calculate cable force in real time so as to monitor cable force of the cable-stayed bridge.
In the invention, the acceleration sensor is connected with the cable force acquisition industrial personal computer through the signal conditioning instrument.
In the invention, the cable force acquisition industrial personal computer and the data integration industrial personal computer are connected with a central switch of a remote monitoring center through a field switch.
In the invention, the acceleration sensor adopts a CA-YD-188 piezoelectric acceleration sensor.
In the invention, the WEB server is loaded with a data service end program.
An on-line monitoring system for the cable force of a large-scale cable-stayed bridge monitors the cable force of the cable-stayed bridge on line, and comprises the following concrete implementation steps:
the first step: build on-line monitoring system
Setting up an acceleration sensor, a site acquisition station and a remote monitoring center, wherein the acceleration sensor is arranged on a guy cable of a cable-stayed bridge so as to acquire the vibration condition of the guy cable at a high speed in real time; the acceleration vibration signal is accessed to a signal conditioning instrument of a field acquisition station by a cable nearby and then transmitted to a cable force acquisition industrial personal computer, a cable force acquisition program is loaded on the cable force acquisition industrial personal computer, the acceleration signal acquired by the program is sent to a bridge acquisition client program of a data integration industrial personal computer in batches, and the bridge acquisition client program processes the acceleration signal and calculates the cable force in real time; the acceleration original data are locally stored and regularly cleaned by the data integration industrial personal computer, and the cable force data are sent to a database server of a remote monitoring center for permanent storage;
and a second step of: development software platform
(1) The software platform consists of a cable force acquisition program, a bridge acquisition client program, a data service end program and a WEB display platform, wherein the cable force acquisition program, the bridge acquisition client program, the data service end program and the WEB display platform are realized by adopting a WPF technology of a NET Framework platform, and the WEB display platform is realized by adopting a Java EE technology;
(2) The online monitoring system is designed with two acquisition ends: one is a cable force acquisition program and the other is a bridge acquisition client program;
and a third step of: design data processing flow
(I) The method comprises the steps of data acquisition, carrying out real-time high-speed acquisition on vibration signals of a inhaul cable through an API interface by a cable force acquisition program, wherein the obtained data is an encapsulated two-dimensional matrix structure analog wave form (double), the structure comprises channel numbers, voltage values and acquisition time, the cable force acquisition program traverses the matrix, establishes a mapping relation between the channel numbers and acceleration sensor numbers, then sends the data to a bridge acquisition client program through a TCP protocol, and the bridge acquisition client program receives and processes the data;
(II) data caching, which is important content of data preprocessing, is performed in a bridge acquisition client program, and meanwhile, in order to avoid access conflict, a cache space is realized by adopting a ConcurrentQueue object with thread safety;
(III) spectrum analysis, namely firstly detecting the data quantity in a buffer space, starting to carry out multi-thread spectrum analysis after the buffer space is filled, timing by a timer, triggering callback once every timing time T, and completing spectrum analysis once by a thread and outputting a cable force value;
fourth step: fundamental frequency extraction
According to the relation between the cable force and each order of self-vibration frequency, each peak value on the cable power spectrum is theoretically equidistant, the value of the distance is the fundamental frequency of the cable, according to the principle, a self-vibration frequency searching algorithm based on frequency spectrum grouping is designed, and then the fundamental frequency is obtained according to the searched self-vibration frequency, and the method specifically comprises the following steps:
1) Data acquisition, assuming M sets of cable vibration time domain signals, each set of signals contains N sampling points (n=2 n ) Represented by matrix a:
2) Performing frequency spectrum transformation, performing FFT (fast Fourier transform) on each group of inhaul cable vibration time domain signals to obtain M groups containing 2 n The discrete spectrum sequence of data points is only half of the discrete spectrum sequence B, namely
3) Window-shifting grouping, grouping each group of spectrums of the discrete spectrum sequence B again, wherein the point number of each group is p, the value of p is required to be an integer power of 2, for example, p= 2,4,8,16,32,64 … …, and each group of spectrums can obtain 2 n-1 Group/p subvectors, wherein the last subvector may have a number of elements less than p, i.e
4) Extracting peak value, and obtaining maximum value of each group of sub-vectors in step 3), and forming a new vector C 'by using maximum value of each group'
Wherein c 11 ＝max{b 11 b 12 b 13 … b 1p }，c 12 ＝max{b 1(p+1) b 1(p+2) b 1(p+3) … b 1(2p) -and so on;
5) Removing direct current, wherein the first column in C' is the direct current and near direct current components in the frequency spectrum sequence, so that the peak value vector C is obtained
6) Identifying the main amplitude, taking the global maximum of the peak vector C matrix in the step 5), namely the amplitude of the main amplitude frequency:
E＝max(max(C)) (6)
7) Extracting effective amplitude, screening peak vector C vector, and only preserving the value larger than m, wherein m is a constant between [0,1] to obtain a new vector G:
8) Extracting the self-vibration frequency, and taking the frequency corresponding to each element value in the new vector G to obtain a self-vibration frequency vector F, namely the self-vibration frequency of each order:
F＝{f 1 f 2 f 3 … f k } (8)
9) Assuming that k elements are included in the self-oscillation frequency vector F and k > =2, starting from the 2 nd self-oscillation frequency extracted, subtracting the extracted self-oscillation frequency from the previous self-oscillation frequency in turn to obtain a frequency difference vector D
D＝diff(F)＝{d 1 d 2 d 3 … d k-1 }，d i ＝f j -f j-1 ，j＝2，3，4…k (9)
10 Extracting fundamental frequency, and obtaining mode of the frequency difference vector D in the step 9), namely the fundamental frequency f 1
f 1 ＝mode(D) (10)
11 Soxhlet force T)
The vibration frequency method is deduced according to a string vibration theory, and a free vibration equation of the stay cable is solved to obtain the cable force:
wherein T is the cable force, k=4wl 2 The ratio of the weight to the length of the cable is equal to the ratio of the weight to the length of the cable, the weight is equal to the weight acceleration, and the weight is equal to the weight acceleration n For the nth order natural vibration frequency of the cable, it is obvious that the key to find the cable force is to find the fundamental frequency f 1 According to the formula, each peak value on the cable power spectrum is in theory equidistant, and the value of the distance is the fundamental frequency f of the cable 1 The higher order frequencies are integer multiples of the fundamental frequency, so:
T＝K(f 1 ) 2 ；
fifth step: visualization of results
And extracting fundamental frequencies of all inhaul cables, calculating Quan Qiaosuo force according to the extracted fundamental frequencies, and performing visual presentation monitoring by a WEB display platform.
The beneficial effects are that:
(1) According to the invention, through the design of the high-performance acquisition system and the acquisition program, the high-efficiency acquisition and transmission of mass acceleration data can be completed;
(2) The invention adopts a multithreading programming technology, and improves the calculation speed of the cable force on the basis of not increasing the hardware cost;
(3) The self-vibration frequency searching algorithm based on the frequency spectrum grouping ensures that the self-vibration frequency searching is concise, and the fundamental frequency extraction can be accurately and rapidly completed only by adjusting two parameters;
(4) The invention realizes the visualization of the dynamic distribution of the full-bridge cable force and provides convenience for the cable force monitoring of the cable-stayed bridge.
Drawings
Fig. 1 is a general architecture diagram of an embodiment of the present invention.
Fig. 2 is a schematic diagram of system software and data flow in an embodiment of the invention.
Fig. 3 is a flow chart of the multi-line Cheng Pinpu analysis in an embodiment of the invention.
Fig. 4 is a schematic diagram of a packet pickup maximum value during a baseband extraction algorithm according to an embodiment of the present invention.
Fig. 5 is a schematic diagram of screening natural vibration frequencies in the process of the fundamental frequency extraction algorithm in the embodiment of the invention.
Fig. 6 is a schematic diagram of a cable time domain vibration signal according to an embodiment of the invention.
Fig. 7 is a schematic diagram of a cable signal spectrum distribution in an embodiment of the invention.
Fig. 8 is a schematic diagram of frequency extraction of natural vibration in a cable signal spectrum analysis in an embodiment of the invention.
Fig. 9 is a schematic diagram of a fundamental frequency distribution of a stay cable according to an embodiment of the present invention.
Fig. 10 is a schematic diagram of a cable force distribution visualization of a stay cable in an embodiment of the invention.
Detailed Description
The invention is further described with reference to the following detailed drawings in order to make the technical means, the creation characteristics, the achievement of the purpose and the effect of the implementation of the invention easy to understand.
An on-line monitoring system for the cable force of a large-scale cable-stayed bridge monitors the cable force of the cable-stayed bridge on line, and comprises the following concrete implementation steps:
the first step: build on-line monitoring system
The on-line monitoring system comprises an acceleration sensor, a field acquisition station and a remote monitoring center, as shown in figure 1, the acceleration sensor of the system adopts a CA-YD-188 piezoelectric acceleration sensor (IEPE), the built-in low-noise IEPE is excited by a 12-24 VDC/2-10 mA constant current source, the constant current source adopts a YE3826 multichannel IEPE constant current adapter and is connected with the sensor through a BNC connector, an acceleration signal is acquired by an NI 9205 acquisition board card, the acquisition board card is provided with 32 channels, rated input voltage is +/-0.2 to +/-10V and can be matched, the acquisition board card is directly inserted into an NI cDAQ-9139 controller clamping groove of a cable force acquisition industrial personal computer through a detachable spring terminal connector, an Intel Core 7 dual-Core processor is arranged in the NI cDAQ-9139 controller, a USB high-speed interface, a gigabit Ethernet interface and a serial interface are arranged, and a self-carrying WES7 and LabEW Real-Time operation system can independently finish the signal acquisition of the acceleration sensor, but the acquisition board card is difficult to be used as a local area network for the acquisition data acquisition platform to be expanded, and the acquisition data is difficult to be transmitted to the local area network controller through the implementation of the control platform;
the acceleration sensor is arranged on a guy cable of the cable-stayed bridge so as to acquire the vibration condition of the guy cable at a high speed in real time; the acceleration vibration signal is accessed to a signal conditioning instrument of a field acquisition station by a cable nearby and then transmitted to a cable force acquisition industrial personal computer, a cable force acquisition program is loaded on the cable force acquisition industrial personal computer, the acceleration signal acquired by the program is sent to a bridge acquisition client program of a data integration industrial personal computer in batches, and the bridge acquisition client program processes the acceleration signal and calculates the cable force in real time; the acceleration original data are locally stored and regularly cleaned by the data integration industrial personal computer, and the cable force data are sent to a database server of a remote monitoring center for permanent storage;
and a second step of: development software platform
(1) The software platform consists of a cable force acquisition program, a bridge acquisition client program, a data service end program and a WEB display platform, wherein the cable force acquisition program, the bridge acquisition client program, the data service end program and the WEB display platform are realized by adopting the WPF technology of a NET Framework platform, the WEB display platform is realized by adopting the Java EE technology, and the structure of the software system is shown in figure 2;
(2) The online monitoring system is designed with two acquisition ends: the system mainly considers that an NI acquisition system is an independent platform, and the independent acquisition program can be developed to avoid the coupling with the bridge acquisition client program, so that the program development and the later operation and maintenance are facilitated;
and a third step of: design data processing flow
(I) The method comprises the steps of data acquisition, carrying out real-time high-speed acquisition on a vibration signal of a inhaul cable through an API (application program interface) provided by an NI (wireless interface) company by a cable force acquisition program, wherein the obtained data is an encapsulated two-dimensional matrix structure analog wave form < double >, the structure comprises information such as channel numbers, voltage values, acquisition time and the like, the cable force acquisition program traverses the matrix, establishes a mapping relation between the channel numbers and acceleration sensor numbers, then sends the data to a bridge acquisition client program through a TCP (transmission control protocol), carries out subsequent processing such as denoising, spectrum analysis and cable force calculation after the bridge acquisition client program receives the data, and finally sends the data to a data server program to finish higher-level data analysis work such as statistics, early warning and repository;
(II) data caching, data preprocessing is performed in a bridge acquisition client program, preprocessing content is mainly data caching control, FFT transformation is needed in subsequent spectrum analysis work, and in order to improve efficiency and accuracy, a base 2FFT algorithm is adopted in the embodiment, and a time domain signal of an acceleration sensor is required to have 2 n The program uses the buffer space as input data of FFT transformation by establishing buffer and limiting the buffer space to a fixed length, and the data in the buffer is dynamically updated although the capacity of the buffer space is fixed, and the old data can be covered by new data; considering the requirement of a plurality of threads for accessing a data cache space, and simultaneously meeting a data first-in first-out principle, in order to avoid access conflict, the cache space is realized by adopting a ConcurrentQueue object of thread safety;
(III) spectrum analysis, namely firstly detecting the data quantity in a buffer space, starting spectrum analysis after the buffer space is filled, and realizing multi-thread spectrum analysis by software programming, wherein as shown in figure 3, assuming that the number of stay cables is M, the number of FFT calculation points is N, the timing operation interval is T, after the program is started, M working threads are directly opened up, each thread is responsible for cable force calculation of one stay cable, and the M threads work in parallel to improve the CPU utilization rate and realize real-time calculation and online monitoring of cable force; in each working thread, 3 sub-threads are opened up respectively, wherein a thread a is responsible for data cache control, a thread b is responsible for spectrum analysis, and a thread c is responsible for timing triggering operation; the spectrum analysis function in the thread b is a callback function of the thread c, the callback is triggered once by each time T, and the thread b completes spectrum analysis once and outputs a cable force value;
fourth step: fundamental frequency extraction
According to the relation between the cable force and each order of self-vibration frequency, each peak value on the cable power spectrum is theoretically equidistant, the value of the distance is the fundamental frequency of the cable, according to the principle, a self-vibration frequency searching algorithm based on frequency spectrum grouping is designed, and then the fundamental frequency is obtained according to the searched self-vibration frequency, and the method specifically comprises the following steps:
1) Data acquisition as shown in fig. 6, assuming M sets of cable vibration time domain signals, each set of signals contains N sampling points (n=2 n ) Represented by matrix a:
2) Performing frequency spectrum transformation, performing FFT (fast Fourier transform) on each group of inhaul cable vibration time domain signals to obtain M groups containing 2 n The discrete spectrum sequence of data points, due to the symmetry of the spectrum, is shown in FIG. 7, i.e. only half of the discrete spectrum sequence B is taken in this embodiment
3) Window-shifting grouping, grouping each group of spectrums of the discrete spectrum sequence B again, wherein the point number of each group is p, the value of p is required to be an integer power of 2, for example, p= 2,4,8,16,32,64 … …, and each group of spectrums can obtain 2 n-1 Group/p subvectors, wherein the last subvector may have a number of elements less than p, i.e
4) Extracting peak value, and obtaining maximum value of each group of sub-vectors in step 3), and forming a new vector C 'by using maximum value of each group'
Wherein c 11 ＝max{b 11 b 12 b 13 … b 1p }，c 12 ＝max{b 1(p+1) b 1(p+2) b 1(p+3) … b 1(2p) And so on as shown in fig. 4;
5) Removing direct current, wherein the first column in C' is the direct current and near direct current components in the frequency spectrum sequence, so that the peak value vector C is obtained
6) Identifying the main amplitude, taking the global maximum of the peak vector C matrix in the step 5), namely the amplitude of the main amplitude frequency:
E＝max(max(C)) (6)
7) Extracting effective amplitude, screening peak vector C vector, and only preserving the value larger than m, wherein m is a constant between [0,1] to obtain a new vector G:
8) Extracting the self-vibration frequency, and taking the frequency corresponding to each element value in the new vector G to obtain a self-vibration frequency vector F, namely the self-vibration frequency of each order:
F＝{f 1 f 2 f 3 … f k } (8)
as shown in fig. 5, f= {3.1250,4.6875,5.4688,6.2500,7.0313,7.6563,8.2813,9.0625,10.4688,11.2500,12.1875,12.9688,13.7500,14.5313,15.3125,16.2500,17.0313}
9) Assuming that k elements are included in the self-oscillation frequency vector F and k > =2, starting from the 2 nd self-oscillation frequency extracted, subtracting the extracted self-oscillation frequency from the previous self-oscillation frequency in turn to obtain a frequency difference vector D
D＝diff(F)＝{d 1 d 2 d 3 … d k-1 }，d i ＝f j -f j-1 ，j＝2，3，4…k (9)
Calculated as d= {1.5625,0.7813,0.7813,0.7813,0.6250,0.6250,0.7813,1.4063,0.7813,0.9375,0.7813,0.7813,0.7813,0.7813,0.9375,0.7813}
10 Extracting fundamental frequency, and obtaining mode of the frequency difference vector D in the step 9), namely the fundamental frequency f 1
f 1 ＝mode(D) (10)
Calculated fundamental frequency f1, f 1 ＝0.7813(Hz)
11 Soxhlet force T)
The vibration frequency method is deduced according to a string vibration theory, and a free vibration equation of the stay cable is solved to obtain the cable force:
wherein T is the cable force, k=4wl 2 The ratio of the weight to the length of the cable is equal to the ratio of the weight to the length of the cable, the weight is equal to the weight acceleration, and the weight is equal to the weight acceleration n For the nth order natural vibration frequency of the cable, it is obvious that the key to find the cable force is to find the fundamental frequency f 1 According to the formula, each peak value on the cable power spectrum is in theory equidistant, and the value of the distance is the fundamental frequency f of the cable 1 The higher order frequency is an integer multiple of the fundamental frequency, and the scaling factor K of the cable is 5630 according to engineering data, so:
T＝K(f 1 ) 2 ＝5630×(0.7813) 2 ＝3437；
fifth step: visualization of results
According to the flow shown in fig. 3, the fundamental frequencies of all inhaul cables are extracted, as shown in fig. 9, quan Qiaosuo force is calculated according to the extracted fundamental frequencies, and then visual display monitoring is carried out by a WEB display platform, as shown in fig. 10, the full-bridge cable force distribution is clear at a glance.
Claims (9)
1. The cable force on-line monitoring system of the large cable-stayed bridge comprises an acceleration sensor, a field acquisition station and a remote monitoring center, and is characterized in that the acceleration sensor is arranged on a cable of the cable-stayed bridge, a cable force acquisition industrial personal computer and a data integration industrial personal computer are arranged in the field acquisition station, the cable force acquisition industrial personal computer is connected with the acceleration sensor, and the cable force acquisition industrial personal computer and the data integration industrial personal computer are respectively connected with the remote monitoring center; the cable force acquisition process is used for acquiring acceleration signals, the remote monitoring center is provided with a WEB server and a database server, the acceleration signals acquired by the cable force acquisition process are sent to a bridge acquisition client program loaded by the data integration industrial personal computer in batches, and the bridge acquisition client program processes the acceleration signals to calculate cable force in real time so as to monitor cable force of the cable stayed bridge;
the cable force of the cable-stayed bridge is monitored on line through the large-scale cable-stayed bridge cable force on-line monitoring system, and the specific implementation steps are as follows:
the first step: build on-line monitoring system
Setting up an acceleration sensor, a site acquisition station and a remote monitoring center, wherein the acceleration sensor is arranged on a guy cable of a cable-stayed bridge, acceleration vibration signals are connected into a signal conditioning instrument of the site acquisition station through a cable, and then transmitted to a cable force acquisition industrial personal computer, a cable force acquisition program is loaded on the cable force acquisition industrial personal computer, and the program acquires acceleration signals and sends the acceleration signals to a bridge acquisition client program loaded by a data integration industrial personal computer in batches, and the bridge acquisition client program processes the acceleration signals and calculates the cable force in real time;
and a second step of: development software platform
(1) The software platform consists of a cable force acquisition program, a bridge acquisition client, a data server program and a WEB display platform;
(2) The online monitoring system is designed with two acquisition ends: a cable force acquisition program and a bridge acquisition client program;
and a third step of: design data processing flow
(I) The method comprises the steps of data acquisition, namely, carrying out real-time high-speed acquisition on vibration signals of a inhaul cable through an API interface by a cable force acquisition program, wherein the obtained data is of a packaged two-dimensional matrix structure, the structure comprises channel numbers, voltage values and acquisition time, the cable force acquisition program traverses the matrix, a mapping relation is established between the channel numbers and the acceleration sensor numbers, then the data is sent to a bridge acquisition client program through a TCP protocol, and the bridge acquisition client program receives the data and then processes the data;
(II) data caching, wherein data caching control is carried out in a bridge acquisition client program;
(III) spectrum analysis, namely firstly detecting the data quantity in a buffer space, starting to carry out multi-thread spectrum analysis after the buffer space is filled, timing by a timer, triggering callback once every timing time T, and completing spectrum analysis once by a thread and outputting a cable force value;
fourth step: fundamental frequency extraction
According to the relation between the cable force and the frequency of each order of natural vibration, the peak values on the cable power spectrum are theoretically equidistant, the value of the distance is the fundamental frequency of the cable, according to the principle, a self-vibration frequency searching algorithm based on frequency spectrum grouping is designed, and then the fundamental frequency f is obtained according to the searched self-vibration frequency 1 ；
Fifth step: visualization of results
And extracting fundamental frequencies of all inhaul cables, calculating Quan Qiaosuo force according to the extracted fundamental frequencies, and performing visual presentation monitoring by a WEB display platform.
2. The on-line monitoring system for the cable force of the large cable-stayed bridge according to claim 1, wherein the acceleration sensor is connected with the cable force acquisition industrial computer through a signal conditioning instrument.
3. The system for on-line monitoring of cable force of large cable-stayed bridge according to claim 1, wherein the cable force acquisition industrial personal computer and the data integration industrial personal computer are connected with a central switch of a remote monitoring center through a field switch.
4. The on-line monitoring system for the cable force of the large cable-stayed bridge according to claim 1, wherein the acceleration sensor is a CA-YD-188 piezoelectric acceleration sensor.
5. The system for monitoring the cable force of the large cable-stayed bridge on line according to claim 1, wherein the WEB server is loaded with a data service end program.
6. The system for online monitoring of cable force of a large cable-stayed bridge according to claim 1, wherein in the second step, the cable force acquisition program, the bridge acquisition client program and the data service program are implemented by adopting a WPF technology of a NET Framework platform, and the WEB display platform is implemented by adopting a Java EE technology.
7. The system for online monitoring of cable force of a large cable-stayed bridge according to claim 1, wherein in the third step, the data buffer space is implemented by using a thread-safe ConcurrentQueue object.
8. The on-line monitoring system for cable tension of a large cable-stayed bridge according to claim 1, wherein in the fourth step, the fundamental frequency extraction is specifically as follows:
1) Data acquisition, wherein M groups of inhaul cable vibration time domain signals are assumed, and each group of signals comprises N sampling points N=2 n Represented by matrix a:
2) Performing frequency spectrum transformation, performing FFT (fast Fourier transform) on each group of inhaul cable vibration time domain signals to obtain M groups containing 2 n The discrete spectrum sequence of data points is only half of the discrete spectrum sequence B, namely
3) The window is shifted to group, each group of frequency spectrums of the discrete frequency spectrum sequence B are grouped again, the point number of each group is p, the value of p is required to be the integer power of 2, and each group of frequency spectrums can obtain 2 n-1 Group/p subvectors, wherein the last subvector may have a number of elements less than p, i.e
4) Extracting peak value, and obtaining maximum value of each group of sub-vectors in step 3), and forming a new vector C 'by using maximum value of each group'
Wherein c 11 ＝max{b 11 b 12 b 13 … b 1p }，c 12 ＝max{b 1(p+1) b 1(p+2) b 1(p+3) … b 1(2p) -and so on;
5) Removing direct current, wherein the first column in C' is the direct current and near direct current components in the frequency spectrum sequence, so that the peak value vector C is obtained
6) Identifying the main amplitude, taking the global maximum of the peak vector C matrix in the step 5), namely the amplitude of the main amplitude frequency:
C＝max(max(c)) (6)
7) Extracting effective amplitude, screening peak vector C vector, and only preserving the value larger than m, wherein m is a constant between [0,1] to obtain a new vector G:
8) Extracting the self-vibration frequency, and taking the frequency corresponding to each element value in the new vector G to obtain a self-vibration frequency vector F, namely the self-vibration frequency of each order:
F＝{f 1 f 2 f 3 … f k } (8)
9) Assuming that k elements are included in the self-oscillation frequency vector F and k > =2, starting from the 2 nd self-oscillation frequency extracted, subtracting the extracted self-oscillation frequency from the previous self-oscillation frequency in turn to obtain a frequency difference vector D
D＝diff(F)＝{d 1 d 2 d 3 … d k-1 }，d i ＝f j -f j-1 ，j＝2,3,4…k (9)
10 Extracting fundamental frequency, and obtaining mode of the frequency difference vector D in the step 9), namely the fundamental frequency f 1
f 1 ＝mode(D) (10)。
9. The on-line monitoring system for cable force of large cable-stayed bridge according to claim 1, wherein in the fourth step, the cable force T is calculated as follows:
deducing according to a string vibration theory, and solving a free vibration equation of the stay cable to obtain the cable force:
wherein T is the cable force, k=4wl 2 The ratio of the weight to the length of the cable is equal to the ratio of the weight to the length of the cable, the weight is equal to the weight acceleration, and the weight is equal to the weight acceleration n For the nth order natural vibration frequency of the cable, it is obvious that the key to find the cable force is to find the fundamental frequency f 1 According to the formula, each peak value on the cable power spectrum is in theory equidistant, and the value of the distance is the fundamental frequency f of the cable 1 The higher order frequencies are integer multiples of the fundamental frequency, so:
T＝K(f 1 ) 2 。
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| CN101963536B (en) * | 2010-08-13 | 2012-08-15 | 重庆大学 | Cable tension real-time monitoring method |
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