CN114526810A - Frequency measurement method of vibrating wire type sensor - Google Patents
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- 238000005259 measurement Methods 0.000 claims abstract description 23
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- 238000010408 sweeping Methods 0.000 claims description 4
- 230000003247 decreasing effect Effects 0.000 claims description 2
- 238000012544 monitoring process Methods 0.000 abstract description 3
- 230000005284 excitation Effects 0.000 description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
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- 229910000831 Steel Inorganic materials 0.000 description 1
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- 230000006698 induction Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
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- G01H13/00—Measuring resonant frequency
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Abstract
The invention discloses a frequency measuring method of a vibrating wire type sensor, and belongs to the technical field of health monitoring. The method comprises the steps of firstly carrying out full-frequency scanning to obtain the response frequency of a sensor, carrying out frequency scanning in a second scanning process by taking the response frequency obtained in the first scanning process as a median value and reducing a frequency scanning range, wherein the obtained frequency is compared with the response frequency obtained in the first scanning process; if the difference value of the two acquired frequencies meets the requirement, determining the initial frequency of the sensor to be the average value of the sum of the first response frequency and the second response frequency; the method has the advantages of short measurement period and high precision, greatly reduces the labor input and labor intensity, improves the measurement efficiency and reduces the application difficulty of the vibrating wire sensor.
Description
Technical Field
The invention relates to a frequency measuring method of a vibrating wire type sensor, and belongs to the technical field of health monitoring.
Background
With the rapid development of economy and science and technology, more and more large-scale complex engineering structures are built, such as large-span bridges, gymnasiums, high-rise buildings, water conservancy facilities and the like, and the engineering structures are very important for guaranteeing the safety of lives and properties of people. Usually, a vibrating wire type sensor is adopted to monitor physical quantities such as pressure, displacement, temperature, deformation quantity, leakage and the like of a project, so that the operation condition of the project is judged, and some geological disasters or project leaks are predicted. In order to ensure the safe use of a large-scale structural body, it is necessary to establish a reliable structural body health monitoring system.
The vibrating string sensor has mainly two structures, one single coil and one double coil, and the single coil has the exciting coil and the vibration pick-up coil in the same structure, and has one vibrating string with one end fixed and the other end connected to elastic pressure sensing film. The middle of the string is provided with a soft iron which is placed in the magnetic field of the exciter consisting of the magnet and the coil. The exciter also serves as a vibration pickup when the excitation is stopped. When the vibration detection device works, the vibrating wire vibrates under the excitation of the exciter, the vibration frequency of the vibrating wire is related to the pressure borne by the diaphragm, and when the excitation is stopped, the coil can be used as a vibration pickup coil to detect the electromotive force generated by the vibration of the vibrating wire. By measuring the frequency of the electromotive force, the frequency of the vibrating wire can be measured. The single coil structure has the disadvantage that continuous measurement cannot be carried out, but the device is simple and stable. The double-coil structure means that an exciting coil and a vibration pickup coil are separated, and generally adopts an electromagnetic method, wherein the electromagnetic method adopts two magnets with coils as the exciting coil and the vibration pickup coil respectively. The induction signal of the vibration pickup coil is amplified and then sent to the exciting coil to supplement the energy of vibration. In order to reduce the influence of the nonlinearity of the sensor on the measurement accuracy, a proper optimal working frequency band needs to be selected and prestress needs to be set, or a differential structure with a vibrating wire arranged on each of two sides of the pressure sensing film needs to be adopted. The double-coil structure can be used for continuous measurement, the measurement precision is better, but the structure is more complex, and the stability is not good.
There is an approximate range of natural frequencies of oscillation of the vibrating wire sensor, typically 400 + 4500 HZ. According to the principle of resonance in physics, a string resonates when the frequency of the excitation signal applied to the sensor is close to or equal to the natural frequency of the string in the sensor. In the resonance state, the amplitude of the steel string oscillation is large. The vibration mode of the vibrating string type sensor has two modes, one mode is high-voltage plucking vibration and the other mode is low-voltage frequency sweeping vibration.
Disclosure of Invention
Aiming at the defects of the frequency measurement mode of the existing vibrating wire sensor, the invention provides the frequency measurement method of the vibrating wire sensor, which greatly improves the measurement precision, the measurement efficiency and the measurement stability and simultaneously reduces the loss of the sensor.
A frequency measurement method of a vibrating wire sensor comprises the following steps:
step 1, during first measurement, performing full-band low-voltage frequency sweeping at a certain stepping frequency according to the frequency range distribution range of the vibrating string type sensor, and executing step 2;
step 2, judging whether a response frequency f exists1If yes, calculating the measured frequency weight to obtain f1Step 3 is executed after the data is stored in the memory; otherwise, the step frequency of the reduced scanning returns to the step 1;
step 3, using the first frequency f1For the median value, the sweep frequency range is narrowed, the step frequency is reduced for sweep frequency, and the measured frequency is subjected to median f2Storing the data into a memory, and executing the step 4;
step 4, judging the frequency f1And frequency f2Whether the difference value meets the requirement or not, if so, executing the step 5; otherwise, returning to the step 1 for execution;
step 5, f is processed3Storing the initial value of the sensor frequency in a memory, and executing the step 6;
step 6, using the first frequency f3For the median value, reducing the sweep frequency range, reducing the step frequency to sweep frequency to obtain the response frequency f of the sensor, and executing the step 7;
step 7, judging whether the frequency f and the frequency f are the same3Whether the difference value meets the requirement or not, if so, executing a step 8; otherwise, returning to the step 1 for execution;
and 8, outputting the frequency f of the sensor.
Preferably, in step 1, the frequency range distribution range of the vibrating wire sensor is 400Hz to 6000 Hz.
Preferably, in step 1 or 3 or 6, the step frequency is Δ f increased for each frequency sweep.
Preferably, in step 2, the weight calculation is = (x)1f1+x2f2+x3f3+…+xkfk）/∑1 kfiWherein x iskIs each time adjacent frequency data, fkIs the weight of each difference, decreasing from 10 to 1 as the distance time increases.
Preferably, 5. the method for measuring a frequency of a vibrating wire sensor according to claim 1, wherein the sweep range in step 3 and step 6 corresponds to (f)110) Hz and (f)3±10）Hz。
Preferably, in step 4 or 7, f1And frequency f2The difference between f and f is required to be less than 5Hz and f3The difference between them is required to be less than 5Hz in absolute value.
Preferably, step 5 f3Is (f)1+f2）/2。
In the subsequent frequency sweep measurement, the initial frequency result of each measurement is the median, the approximate frequency range can be rapidly determined, the defects of slow positioning and low measurement speed of the traditional frequency sweep measurement are overcome, meanwhile, the frequency band of each frequency sweep is influenced by the recent measurement result, during actual measurement, more and more historical data are obtained, the frequency sweep range is smaller and smaller, and the frequency sweep precision of each frequency sweep is higher than that of the previous frequency sweep under the condition that the frequency sweep sampling frequency is fixed. If the current frequency of the sweep differs too much from the initial value, the initial value is recalibrated. Has the characteristics of high precision and high efficiency. The invention has the advantages of short measuring period and high precision, greatly reduces the labor input and labor intensity, improves the measuring efficiency and reduces the application difficulty of the vibrating wire sensor.
By adopting the measuring method, when the vibration frequency meeting the requirement does not exist in the sweep frequency range, the original resetting method of the initial value can be adopted again, and the measuring reliability of the method is ensured.
Drawings
FIG. 1 is a schematic flow chart of a frequency measurement method of a vibrating wire sensor according to the present invention.
Detailed Description
The following describes embodiments of the present invention with reference to the drawings.
As shown in fig. 1, the present invention is a frequency measuring method of a vibrating wire sensor, comprising the following steps:
step 1, during first measurement, performing full-band low-voltage frequency sweeping at a certain stepping frequency according to the frequency range distribution range of the vibrating string type sensor, and executing step 2;
step 2, judging whether a response frequency f exists1If yes, calculating the measured frequency weight to obtain f1Step 3 is executed after the data is stored in the memory; otherwise, the step frequency of the reduced scanning returns to the step 1;
step 3, using the first frequency f1For the median value, the sweep frequency range is narrowed, the step frequency is reduced for sweep frequency, and the measured frequency is subjected to median f2Storing the data into a memory, and executing the step 4;
step 4, judging the frequency f1And frequency f2Whether the difference value meets the requirement or not, if so, executing the step 5; otherwise, returning to the step 1 for execution;
step 5, f is processed3Storing the initial value of the sensor frequency in a memory, and executing the step 6;
step 6, using the first frequency f3For the median value, reducing the sweep frequency range, reducing the step frequency to sweep frequency to obtain the response frequency f of the sensor, and executing the step 7;
step 7, judging whether the frequency f and the frequency f are the same3Whether the difference value meets the requirement or not, if so, executing a step 8; otherwise, returning to the step 1 for execution;
and 8, outputting the frequency f of the sensor.
In the following, the example is illustrated by using a vibrating wire type stress gauge manufactured by Changshikang code measurement and control technologies, Inc., which is numbered 101, has a specification of-1500 mu epsilon, a resistance of 470 ohm and a wire length of 18 m.
First, the sensor was installed in an acquisition system in the field, and the sensor was stressed 500 μ ε, at a theoretical frequency of 1860 Hz. When the acquisition system works, the first measurement is started, the coil is excited by adopting low-voltage frequency sweep, the frequency sweep range is 400HZ-6000HZ, the stepping value is 50HZ, and the sensor coil is sequentially excited by using low-voltage signals with the frequencies of 450, 500, 550 … 6000HZ and the like. The exciting coil of the single coil sensor is a vibration pickup coil, and the vibration pickup coil is used for measuring that when the sweep frequency voltage is 1855HZ, the resonance amplitude is maximum, and the resonance electromotive force intensity is greater than the minimum intensity, so that the first measurement frequency result is 1860HZ, f1＝1850HZ。
Then, an embedded controller in the system obtains f1Accessing a memory of a system;
when measuring the frequency for the second time, the controller reads the historical data in the memory, f11855 HZ. At this time, the median value of the second sweep is the result of the previous sweep, i.e. the median value is equal to f1Sweep frequency range of f1+ -10, step value is 1HZ, i.e. the sensor coil is excited by low voltage signal with frequency of 1745, 1746, 1757 … 1965, etc. to obtain maximum resonance frequency of 1860HZ, and the intensity of resonance electromotive force at the frequency is confirmed to be larger than the minimum intensity, so f21860HZ, mixing2And storing the data into a memory.
Comparison f1And f2Has a frequency difference of less than 5Hz, f3Has a frequency of (f)1+f2) The/2 =1857.5HZ is stored in the memory as the initial frequency of the sensor.
Then, following the measurement, the controller takes the historical data in memory, f31857.5, the median of the low pressure sweep is f3The frequency sweep result is 1857.5HZ, and the frequency sweep frequency band is f3And + -5, the sensor coil is sequentially excited by low voltage signals with a step value of 1HZ, i.e. with frequencies of 1852, 1853, 1854, 1859 … 1830, etc., to obtain a maximum resonance frequency of 1860HZ, so that f is 1860HZ and stored in a memory.
The above-described embodiments only express the preferred embodiments of the present invention, and the description thereof is more specific and detailed, but the present invention is not limited to these embodiments, and it should be noted that it is obvious to those skilled in the art. Any modification falling within the scope of protection of the present invention without departing from the gist of the present invention. Therefore, the protection scope of the present patent should be subject to the appended claims.
Claims (7)
1. A frequency measurement method of a vibrating wire sensor is characterized by comprising the following steps:
step 1, during first measurement, performing full-band low-voltage frequency sweeping at a certain stepping frequency according to the frequency range distribution range of the vibrating string type sensor, and executing step 2;
step 2, judging whether a response frequency f exists1If yes, calculating the measured frequency weight to obtain f1Step 3 is executed after the data is stored in the memory; otherwise, the step frequency of the reduced scanning returns to the step 1;
step 3, using the first frequency f1For the median value, the sweep frequency range is narrowed, the step frequency is reduced for sweep frequency, and the measured frequency is subjected to median f2Storing the data into a memory, and executing the step 4;
step 4, judging the frequency f1And frequency f2Whether the difference value meets the requirement or not, if so, executing the step 5; otherwise, returning to the step 1 for execution;
step 5, f is processed3Storing the initial value of the sensor frequency in a memory, and executing the step 6;
step 6, using the first frequency f3For the median value, reducing the sweep frequency range, reducing the step frequency to sweep frequency to obtain the response frequency f of the sensor, and executing the step 7;
step 7, judging whether the frequency f and the frequency f are the same3Whether the difference value meets the requirement or not, if so, executing a step 8; otherwise, returning to the step 1 for execution;
and 8, outputting the frequency f of the sensor.
2. The method for measuring the frequency of the vibrating wire sensor according to claim 1, wherein in step 1, the frequency range of the vibrating wire sensor is distributed in a range of 400Hz to 6000 Hz.
3. The method of claim 1, wherein the step frequency is Δ f increased for each frequency sweep in step 1, 3 or 6.
4. The method as claimed in claim 1, wherein the weight calculation in step 2 is' x = (x) in the method1f1+x2f2+x3f3+…+xkfk）/∑1 kfi
Wherein xkIs each time adjacent frequency data, fkIs the weight of each difference, decreasing from 10 to 1 as the distance time increases.
5. The method according to claim 1, wherein the sweep frequency range in steps 3 and 6 corresponds to (f)110) Hz and (f)3±10）Hz。
6. The method for measuring the frequency of a vibrating wire sensor according to claim 1, wherein in step 4 or 7, f1And frequency f2The difference between f and f is required to be less than 5Hz and f3The difference between them is required to be less than 5Hz in absolute value.
7. The method of claim 1, wherein f is the step 53Is (f)1+f2）/2。
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