CN108051074B - A kind of frequency measurement method of vibrating string type sensor - Google Patents
A kind of frequency measurement method of vibrating string type sensor Download PDFInfo
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- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H13/00—Measuring resonant frequency
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Abstract
The present invention provides a kind of frequency measurement method of vibrating string type sensor, this method it is preceding measure twice when, according to sensor factory characteristic and installation site, use a wide range of sweep frequency technique and wide window intermediate value sweep frequency technique, rapidly find out substantially measurement frequency, and measurement result is left using memory, in subsequent measurement, it uses a kind of using historical data as the dynamic window Frequency Sweeping Method of intermediate value, frequency sweep intermediate value is determined by the last data recorded in memory, frequency sweep window ranges are obtained by the fluctuation situation weighted calculation of historical data, each frequency sweep window ranges are smaller and smaller, precision is higher and higher.When occurring in swept frequency range without resonance result, swept frequency range is expanded using upward backtracking method and original resetting method.The method overcome conventional high-tension energisation mode precision is low, the shortcomings that damaging big disadvantage and conventional low sweep method time-consuming, there is high-precision, when low consumption, the characteristics of damage low to sensor.
Description
Technical field
The invention belongs to engineering monitoring technical fields, more particularly to a kind of frequency measurement method of vibrating string type sensor.
Background technique
Vibrating string type sensor has reliable simple structure, sturdy and durable, strong antijamming capability, measured value, precision and resolving power
The advantages that high and stability is good.In addition, its output is frequency signal, convenient for remote transmission, can directly and microcomputer interface, because
This, in the safety monitoring of projects, especially outdoor large building, bridge, in ground project, generally use type vibration wire biography
Sensor carrys out the pressure of monitoring works, displacement, temperature, deformation quantity, and the physical quantitys such as leakage determine the operation shape of engineering project with this
Condition predicts some geological disasters or project loophole.
Vibrating string type sensor is the resonant transducer using the metallic cord of tension as sensing element.When the length of string determines
Later, the variable quantity of eigentone can characterize the size of pulling force suffered by metallic cord, by corresponding measuring circuit, just
Available and pulling force at certain relationship electric signal.The core of vibrating string type sensor fixed by a both ends, the string wire group of homogeneous
At under the action of external force F, string wire can generate the deformation of Δ L, it is contemplated that variation of the temperature to length, in elastic range, steel
The eigentone f and the relationship of pulling force T of chord length and vibratory string beWherein Δ L=T-T0, α
For linear expansion coefficient, T0, α, K be known constant number.And it is understood that the mechanical oscillation formula for natural frequency of string wire isL is the length of vibratory string in formula, and E is the elasticity modulus of string wire, and ρ is single
The quality (density) of position chord length, λ is the Poisson's coefficient of string wire material, these are constants.We can be according to above-mentioned two public affairs
Formula eliminates public variableShow that the frequency f of string wire is the function of pulling force F and temperature T, therefore, the case where knowing temperature
Under, as long as measuring string wire frequency, external pull size F can be calculated.As the above analysis, for the survey of string wire frequency f
Amount is the measurement core of vibrating string type sensor.
Vibrating string type sensor mainly has two kinds of structures of unicoil and twin coil, wherein unicoil refers to excitation coil and picks up
Vibration coil is the structure of the same coil, and vibratory string one end is fixed, and the other end is attached on elastic pressure-sensitive diaphragm.The middle part of string fills
There is one block of soft iron, is placed in the magnetic field for the driver that magnet and coil are constituted.Driver doubles as vibration pickup when stopping excitation.Work
When making, vibratory string vibrates under the excitation of driver, and vibration frequency is related with the size of diaphragm pressure, is stopping motivating
When, which can regard pick-up coil again, detect the electromotive force that vibratory string vibration generates.By surveying the frequency of the electromotive force, i.e.,
The frequency of vibratory string can be measured.The shortcomings that single coil structure is continuously to measure, but device simple and stable.Two coil configuration is
Referring to that excitation coil and pick-up coil separate, generally takes electromagnetic method, electromagnetic method is equipped with the magnet of coil using two, respectively as
Excitation coil and pick-up coil.The inductive signal of pick-up coil is amplified rear and send the energy for going supplement to vibrate to excitation coil.
Influence for reduction sensor nonlinear to measurement accuracy needs to select moderate best effort frequency range and setting prestressing force, or
Using the differential structure for respectively setting a vibratory string in the two sides of pressure sensitive film.Two coil configuration can be measured continuously, and measurement accuracy is also more
It is good, but structure is complex, and stability is bad.
Either unicoil or twin coil technology, core are all that vibratory string is allowed to generate vibration under the effect of external voltage,
And vibratory string is allowed to generate there are mainly two types of the modes of intrinsic vibration, respectively high pressure activation and low pressure frequency sweep.High pressure activation is to pass through
Transformer generates the pulse of high pressure exciting and string wire is vibrated, voltage > 100V when excitation.Low pressure frequency sweep is comprising target frequency
In one band frequency, with certain step value, scanning frequency pulse string signal from small to large is applied to sensor, when signal frequency and
When string wire intrinsic frequency is close, string wire resonates, and can generate maximum induced electromotive force at this time, this electromotive force frequency is mesh
Mark frequency.Both measurement methods respectively have advantage and disadvantage, and high pressure activation mode speed is fast, it is only necessary to primary excitation can be obtained as a result,
But the vibration duration generated is short, signal is not easy to obtain, and measurement accuracy is poor, and high voltage easily makes string wire aging, and damage passes
The sensor service life；In contrast, the vibration signal that conventional low frequency sweep obtains is stronger, and precision is higher, but conventional low frequency sweep needs
Frequency range is known in advance, and often can just be obtained by multiple frequency sweep as a result, time of measuring is very long, it is inefficient.
In engineer application, sensor needs to be chronically exposed to open air, inclement condition, to sensor stability, durability,
Service life, measurement accuracy and speed all have high requirements.High pressure activation and conventional low sweep method have very big defect, not
The requirement being able to satisfy in reliability and precision speed.
Summary of the invention
For the deficiency of the frequency measurement mode of existing vibrating string type sensor, the present invention provides a kind of vibrating string type sensor
Frequency measurement method, substantially increase measurement accuracy, measurement efficiency and the stability of measurement, while reducing sensor
Loss.
A kind of frequency measurement method of vibrating string type sensor, comprising the following steps:
Step 1, when measuring for the first time, low-voltage frequency sweep is carried out according to the maximum frequency range of sensor factory setting, is measured
It response frequency f1 and is stored in memory for the first time.
Step 2, when second of measurement, frequency sweep window ranges are reduced according to sensor mounting location and application index.
Step 3, using frequency f1 for the first time as intermediate value, frequency sweep is carried out according to current frequency sweep window ranges.
Step 4, response frequency is judged whether there is, and if it exists, after in the frequency f2 deposit memory for then obtaining measurement
Step 5 is executed, otherwise, expands return step 3 after frequency sweep window ranges.
Step 5, when subsequent measurement, the frequency sweep window further reduced is weighted according to historical frequency data
Range.
Step 6, the above one-shot measurement result is intermediate value, carries out frequency sweep according to current frequency sweep window ranges.
Step 7, response frequency is judged whether there is, and if it exists, 8 are thened follow the steps, otherwise, after expanding scanning window range
Return step 6.
Step 8, measurement result is stored in memory, judges whether measurement result reaches specified accuracy, reached, then complete to survey
Amount, otherwise, returns to step 5.
Wherein, in step 5, frequency sweep window is weighted by the fluctuation situation of recent history frequency sweep data and is obtained, is added
The weighted factor that power calculates is the difference of the adjacent data of frequency sweep twice of history, and the weight of each difference is by long apart from the current time
Short decision, we take the fluctuation of nearly 10 historical datas as calculating the factor, weight from closely to it is remote be respectively 10,9,8 ... 1.Tool
When body calculates, frequency sweep window size calculation formula is as follows:
Wherein Δ fnIt is the difference of each history adjacent data, xnIt is the weight of each difference, with the increasing of Distance Time
Add, weight is successively decreased from 10 to 1.By formula it is found that the history frequency sweep data for participating in calculating are more, determining window is more excellent, frequency sweep
Efficiency is higher.
In step 4 and step 6, the method for the expansion scanning window range has trace back back up method and original resetting method.
The detailed process of the upward backtracking method are as follows: the above one-shot measurement result is intermediate value, expands frequency sweep window to upper
Window used in frequency sweep carries out frequency sweep；Response frequency is not obtained yet after expanding frequency sweep window, and frequency sweep window continues up
Backtracking, until there is response frequency in frequency sweep window；Frequency sweep window ranges are expanded to the frequency sweep window for response frequency occur.
The detailed process of the original resetting method are as follows: in current frequency sweep window, when not occurring the vibration of sufficient intensity, depending on
Too small for current window, still using last time result as intermediate value, frequency sweep window is disposably expanded to the window for measuring use for the first time, i.e.,
The window size determined by sensor factory characteristic.
The present invention is measured each time in subsequent sweep measurement using last time result as intermediate value, can determine substantially frequency rapidly
Rate range avoids traditional sweep measurement positioning slowly, needs the disadvantage that measuring speed is slow, meanwhile, the frequency sweep window of each frequency sweep
It is influenced by recent measurement result, the fluctuation of historical results can be fed back in window size, and when actual measurement, historical data is increasingly
More, frequency sweep window is smaller and smaller, and in the case where each frequency sweep sampling number is certain, frequency sweep precision is all more primary than preceding each time
It is high.With high-precision, efficient feature.
It, can be using upward when in swept frequency range without satisfactory vibration frequency using measurement method of the invention
Backtracking method and original resetting method expand swept frequency range, upward backtracking method and the original each have their own application scenarios of resetting method, it is ensured that
The reliability of this method measurement.
Detailed description of the invention
Fig. 1 is the flow diagram of the frequency measurement method of vibrating string type sensor of the present invention.
Specific embodiment
Embodiments of the present invention are described with reference to the accompanying drawings of the specification.
As shown in Figure 1, the present invention is a kind of frequency measurement method of vibrating string type sensor, comprising the following steps:
S01 when measuring for the first time, carries out low-voltage frequency sweep according to the maximum frequency range of sensor factory setting, measures head
Secondary response frequency f1 is simultaneously stored in memory.
S02 when measuring for the second time, reduces frequency sweep window ranges according to sensor mounting location and application index.
S03 carries out frequency sweep according to current frequency sweep window ranges using frequency f1 for the first time as intermediate value.
S04 judges whether there is response frequency, and if it exists, executes step 5, otherwise, returns after expanding frequency sweep window ranges
S03。
S05, the frequency f2 that measurement is obtained are stored in memory.
When subsequent measurement, the frequency sweep window model further reduced is weighted according to historical frequency data by S06
It encloses.
S07, the above one-shot measurement result are intermediate value, carry out frequency sweep according to current frequency sweep window ranges.
S08 judges whether there is response frequency, and if it exists, thens follow the steps 9, otherwise, returns after expanding scanning window range
Return S07.
Measurement result is stored in memory by S09, judges whether measurement result reaches specified accuracy, is reached, then executes S10,
Otherwise, it returns and executes S06.
S10 completes measurement.
Give an actual example explanation below, the type vibration wire displacement meter produced in example using Hua Yan pre-stress sensor Co., Ltd,
Its number is 101, specification 50mm, and resistance is 628.7 ohm, wire length 18m.By factory Line Chart it is found that the normal model of its frequency
Enclose about 1500HZ-2500HZ.
Firstly, apply pressure by the acquisition system of sensor installation at the scene to sensor, it is allowed to be displaced 20mm,
Theoretical frequency is because of 1876HZ at this time.When acquisition system works, measurement starts for the first time, and the low pressure frequency sweep of use carries out coil
Excitation, swept frequency range 1500HZ-2500HZ, sweep is 20 times, step value 50HZ, i.e., with 1500,1550,1600 ...
The low voltage signal of the frequencies such as 2500HZ successively stimulus sensor coil.The single coil excitement of this single line coil sensor is pick-up line
Circle is measured by pick-up coil when sweep voltage is 1850HZ, and resonance amplitude is maximum, and its electromotive force intensity that resonates is greater than
Minimum strength, therefore measurement frequency result is 1850HZ, f1=1850HZ for the first time.
Then, the embedded controller in system, by the memory of the f1 access system of acquisition；
When second of measurement frequency, controller reads the historical data in memory, f1=1850HZ.At this point, second
The frequency sweep intermediate value of sweep measurement is previous as a result, i.e. intermediate value is equal to f1, and frequency sweep window size is determined by sensor mounting location
Fixed, actual displacement range is 0-50mm known to installation site, i.e. frequency fluctuation range does not exceed 100HZ.Therefore frequency sweep is taken
Window size is 200HZ, system frequency sweep 20 times within the scope of 1750HZ-1950HZ, step value 10HZ, i.e., with 1750,1760,
The low voltage signal of the frequencies such as 1770 ... 1950 successively stimulus sensor coil, obtaining maximum resonant frequency is 1880HZ, simultaneously
Confirm that the resonance electromotive force intensity under the frequency is greater than minimum strength, therefore f2=1880HZ, f2 is stored in memory.
Then, third time measurement is carried out, the historical data in controller access to memory, f1=1850HZ, f2=1880HZ,
At this point, the intermediate value of low pressure frequency sweep is last frequency sweep as a result, as 1880HZ, frequency sweep window is by historical volatility result weighted calculation
It obtains, f2-f1=30HZ, 30HZ of historical volatility, weight 10, therefore, after weighted calculation, window size is 2* (30*
10)/10=60HZ, swept frequency are 1850HZ to 1910HZ,.Sweep remains as 20 times, step value 3HZ is used
The low voltage signal of the frequencies such as 1850,1853,1856,1859 ... 1910 successively stimulus sensor coil obtains maximum resonance frequency
Rate is 1877HZ, therefore f3=1877HZ, and f3 is stored in memory.
In measurement primary later, ibid method, obtains historical data f1, f2, f3, and frequency sweep intermediate value is f3=1877HZ,
Historical volatility value be f3-f2=3HZ, weight 10, f2-f1=30HZ, weight 9, therefore, after weighted calculation, window size
It can be obtained for 2* (30*9+3*10)/19=31.5HZ, swept frequency range 1861.22HZ to 1892.78HZ, step value 1.575HZ
To more accurate f4=1875.4HZ, f4 is stored in memory.
Therefore increasing with historical data, frequency sweep window size is smaller and smaller, in the situation that sweep is constant
Under, measurement accuracy is higher and higher, and the theoretical value error measured from theoretical value 1876HZ for four times is respectively 26HZ, 4HZ, 1HZ,
0.6HZ, error is smaller and smaller, when historical data reaches or at arrange greater than us 10 of participations weighted calculation, energy base
This elimination error reaches accurate 1876HZ.
At this point, we change pressure, so that displacement is 22mm, target frequency theory is 1905HZ at this time.At this point, continue into
When row measurement, frequency sweep intermediate value is last result 1875.4HZ, and swept frequency range is obtained by historical data weighted calculation, is found at this
In range, all frequencies all do not make string wire resonate, that is, the resonance electromotive force generated is both less than minimum strength.Therefore, with upward
Backtracking method or original resetting method expand swept frequency range.
Upward backtracking method: frequency sweep intermediate value is last result 1875.4HZ, and first expanding frequency sweep window is last frequency sweep window
Mouth 31.5HZ has found that all frequencies in frequency range all do not make string wire resonate, backtracking is continued up at this time, so that frequency sweep window
Mouth size is 60HZ, as a result there is satisfactory resonance in frequency range, that is, being successfully found target frequency is 1905.4HZ,
It is deposited into memory.Operation later returns to the S07 of this method.
Original resetting method: frequency sweep intermediate value is last result 1875.4HZ, and directly expansion frequency sweep window is frequency sweep window for the first time
Mouth 1500-2500HZ, being successfully found target frequency is 1900.4HZ, is deposited into memory.Operation later returns to we
The S07 of method.
Be employed many times it can be seen from above-mentioned actual measured results the method for the present invention measurement, result from 1850HZ to
1880HZ to 1877HZ arrives 1875.4HZ again, and precision is high time by time, and the frequency sweep time due to controlling always at 20 times, consumption
When it is very short always, whole process only measurement result occur compared with macromutation exceed window ranges when, just use upward backtracking method
Expand swept frequency range with original resetting method, therefore overall precision is very high always.
In conclusion it is of the present invention using historical data as the dynamic window Frequency Sweeping Method of intermediate value, with insertion
Formula controller judges the frequency sweep intermediate value of each moment frequency sweep use, and dynamic calculates the window ranges of each frequency sweep, realizes
In high precision, high efficiency, low-loss requirement.Invention introduces external memories to store historical measurement, and controller passes through
Analyze measurement result is lasted, can it is customized participate in frequency sweep window calculation historical data range and data weighting, tool
There are very big independence and elasticity, adapt to the demand of different Practical Projects, realizes the high-precision frequency sweep in the short time.Meanwhile it examining
Consider emergency case, in frequency sweep failure, and have a set of backtracking or resetting strategy, the strategy ensure that frequency sweep each time at
Function increases the stability of this method.
Embodiments of the present invention are explained in detail above in conjunction with attached drawing, but the present invention is not limited to above-mentioned implementations
Mode within the knowledge of a person skilled in the art can also be without departing from the purpose of the present invention
It makes a variety of changes.
Claims (6)
1. a kind of frequency measurement method of vibrating string type sensor, which comprises the following steps:
Step 1, when measuring for the first time, low-voltage frequency sweep is carried out according to the maximum frequency range of sensor factory setting, is measured for the first time
Response frequency f1 is simultaneously stored in memory；
Step 2, when second of measurement, frequency sweep window ranges are reduced according to sensor mounting location and application index；
Step 3, using frequency f1 for the first time as intermediate value, frequency sweep is carried out according to current frequency sweep window ranges；
Step 4, response frequency is judged whether there is, and if it exists, execute after in the frequency f2 deposit memory for then obtaining measurement
Step 5, otherwise, return step 3 after expansion frequency sweep window ranges；
Step 5, when subsequent measurement, the frequency sweep window model further reduced is weighted according to historical frequency data
It encloses；
Step 6, the above one-shot measurement result is intermediate value, carries out frequency sweep according to current frequency sweep window ranges；
Step 7, response frequency is judged whether there is, and if it exists, then follow the steps 8, otherwise, return after expanding frequency sweep window ranges
Step 6；
Step 8, measurement result is stored in memory, judges whether measurement result reaches specified accuracy, reached, then complete to measure,
Otherwise, 5 are returned to step.
2. the frequency measurement method of vibrating string type sensor according to claim 1, which is characterized in that described in step 4
The method for expanding frequency sweep window ranges is upward backtracking method or original resetting method.
3. the frequency measurement method of vibrating string type sensor according to claim 1, which is characterized in that in step 5, added
Power calculates used formula are as follows:
Wherein Δ fnIt is the difference of each history adjacent data, xnIt is the weight of each difference, with the increase of Distance Time, power
Weight successively decreases from 10 to 1.
4. the frequency measurement method of vibrating string type sensor according to claim 1, which is characterized in that described in step 6
The method for expanding frequency sweep window ranges is upward backtracking method or original resetting method.
5. the frequency measurement method of vibrating string type sensor according to claim 2 or 4, which is characterized in that described is upward
The detailed process of backtracking method are as follows: the above one-shot measurement result is intermediate value, expands frequency sweep window ranges and is used to last frequency sweep
Frequency sweep window ranges carry out frequency sweep；Do not obtain response frequency yet after expanding frequency sweep window ranges, frequency sweep window ranges continue to
Upper backtracking, until there is response frequency in frequency sweep window ranges；Frequency sweep window ranges are expanded to the frequency sweep for response frequency occur
Window ranges.
6. the frequency measurement method of vibrating string type sensor according to claim 2 or 4, which is characterized in that described is original
The detailed process of resetting method are as follows: frequency sweep window ranges are disposably expanded to the frequency sweep window ranges for measuring use for the first time.
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| CN109506716B (en) * | 2018-12-25 | 2021-03-19 | 岩联(武汉)科技有限公司 | Vibrating wire type acquisition terminal and excitation frequency band acquisition method thereof |
| CN112986391B (en) * | 2021-02-26 | 2023-05-26 | 北京龙鼎源科技股份有限公司 | Method and device for determining excitation frequency |
| CN113899388B (en) * | 2021-10-08 | 2022-05-20 | 招商局重庆交通科研设计院有限公司 | Self-adaptive data acquisition method for vibrating wire sensor |
| CN113899444A (en) * | 2021-10-08 | 2022-01-07 | 招商局重庆交通科研设计院有限公司 | Resonance frequency measurement method of vibrating wire sensor based on Hanning double windows |
| CN114526810A (en) * | 2021-12-28 | 2022-05-24 | 福建省永正工程质量检测有限公司 | Frequency measurement method of vibrating wire type sensor |
| CN114485735A (en) * | 2022-03-14 | 2022-05-13 | 哈尔滨工业大学 | Self-adaptive sweep frequency excitation string type wireless sensor |
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| JPS61105438A (en) * | 1984-10-29 | 1986-05-23 | Nippon Denso Co Ltd | Oscillation testing device |
| JP3031788B2 (en) * | 1992-07-22 | 2000-04-10 | アルプス電気株式会社 | Sweep frequency generator and tuner adjustment method using the same |
| JPH11113039A (en) * | 1997-10-03 | 1999-04-23 | Kokusai Electric Co Ltd | Reception frequency sweeping method for radio calling receiver |
| CN103968973B (en) * | 2014-05-23 | 2017-01-11 | 重庆建工第三建设有限责任公司 | Shock excitation method for vibrating wire sensor |
| CN105182099B (en) * | 2015-06-17 | 2019-04-12 | 国家电网公司 | Deformation of transformer winding degree and fault method are diagnosed based on frequency response analysis |
| CN105136281B (en) * | 2015-10-14 | 2018-03-02 | 基康仪器股份有限公司 | The frequency measuring equipment and method of vibrating string type sensor |
| CN105628185B (en) * | 2015-12-28 | 2018-11-06 | 江西飞尚科技有限公司 | A kind of vibrating wire sensor frequency tripling screen method |
| CN106289034B (en) * | 2016-08-01 | 2018-04-13 | 长安大学 | A kind of low-power consumption vibration wire sensor and its excitation detection method |
| CN106225656B (en) * | 2016-08-01 | 2018-04-13 | 长安大学 | The excitation detection device and excitation detection method of a kind of low-power consumption vibration wire sensor |
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