CN114777888A - Liquid level measurement error compensation correction method based on fiber bragg grating pressure sensor - Google Patents
Liquid level measurement error compensation correction method based on fiber bragg grating pressure sensor Download PDFInfo
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Abstract
The invention provides a liquid level measurement error compensation correction method based on a fiber bragg grating pressure sensor, which is characterized in that liquid level data obtained by a unitary linear regression model for liquid level measurement of the fiber bragg grating pressure sensor are taken as processing objects, the strong correlation characteristic of the measured liquid level data is obtained by calculating the Pearson correlation coefficient among all groups of measured liquid level height data, and the initial liquid level value is automatically corrected to be corrected liquid level height; and comparing the obtained measured liquid level data with the real data, and finally performing arithmetic average processing on each section of error data on the liquid level measurement height to perform error compensation correction on the measured liquid level data, so that the liquid level measurement precision is greatly improved.
Description
Technical Field
The invention relates to the field of liquid level measurement of large equipment such as aviation aircrafts, ships, automobiles and the like, in particular to a method for compensating and correcting liquid level measurement errors based on a fiber bragg grating pressure sensor.
Background
Liquid level measurement is an important factor for ensuring the safety of daily life and urban development. In liquid level measurement, high measurement accuracy, high measurement reliability, safety and low measurement cost are always important research directions. The fiber grating sensing technology is used as a newly developed sensing technology, the precision and the safety of liquid level measurement are guaranteed by the excellent sensing characteristics of the fiber grating sensing technology, and the advantages of the measured liquid level are obvious by utilizing the grating to sense the liquid level in liquid level monitoring under some special environments.
At present, the pressure sensitivity characteristic of fiber bragg gratings is mostly adopted for measuring the liquid level based on the fiber bragg grating sensing, and the liquid level height is obtained by utilizing the linear relation between the Bragg wavelength drift amount of the fiber bragg grating pressure sensor immersed in liquid and the height from the liquid level. However, the current liquid level measurement based on the fiber bragg grating pressure sensor has the problems of strong wave property of wavelength drift of a restricted fiber bragg grating device, uneven pressure and the like, so that the measurement precision is not high, the requirements in the field of industrial and large-scale equipment liquid level measurement cannot be met, the development of the liquid level measurement field is limited, and the practicability is not strong. Therefore, the improvement of the liquid level measurement precision of the fiber bragg grating pressure sensor is a key for breaking through the limitation of the fiber bragg grating pressure sensor in practical application, and the development prospect of the fiber bragg grating pressure sensor in the field of liquid level measurement is directly determined.
Usually, an error compensation mode is adopted to improve the measurement precision and reduce errors, and the error compensation is also an important content in the processing and application of a precision instrument. Error compensation in principle, an error data or compensation factor given by human is used to offset the original error of the current instrument or problem, so as to achieve the purpose of reducing the error. Currently, there are three main ways for error compensation in precision measurement: error separation techniques, error correction techniques, and error suppression techniques. The core of the error separation technology is to separate a useful signal from an error signal; the core of the error correction technology is to obtain an error correction quantity, namely a compensation factor, in a certain way so as to eliminate an error component in measurement data; the core of the error suppression technology is that an input and output mechanism or a circuit design which is automatically regulated and controlled along with the change of an error source is preset to counteract or eliminate the error. In the invention, the liquid level measurement data is obtained by a liquid level algorithm, the liquid level data and the error data are not easy to separate, and an error separation technology cannot be adopted; the liquid level error is caused by the fact that the Bragg wavelength drift of the fiber bragg grating sensor has a certain fluctuation problem, is related to the material of the device and the test environment, is not easy to offset or eliminate the error from the source, and cannot adopt an error inhibition technology.
Disclosure of Invention
Aiming at the problems that the fluctuation of the wavelength drift of a fiber grating device is strong and the measurement precision is not high due to uneven pressure in the liquid level measurement of a fiber grating-based pressure sensor in the prior art, the requirements in the liquid level measurement field of industrial and large-scale equipment cannot be met, and the development in the liquid level measurement field is limited and the practicability is not strong, the invention provides a liquid level measurement error compensation correction method based on the fiber grating-based pressure sensor, which utilizes the linear relation between the wavelength drift amount and the liquid level height to obtain the liquid level height data and automatically corrects the initial liquid level value to the same measurement height by calculating the Pearson correlation coefficient; and comparing the obtained liquid level data with the real data, and finally performing error compensation correction on the liquid level measurement data by performing arithmetic average processing on the sections of error data on the liquid level measurement height, so that the liquid level measurement precision is greatly improved, the liquid level measurement performance of the fiber bragg grating pressure sensor is improved, and the application requirements in the liquid level measurement of large-scale equipment such as aerocrafts, ships and automobiles are met.
The specific implementation content of the invention is as follows:
the invention provides a liquid level measurement error compensation correction method based on a fiber bragg grating pressure sensor, which comprises the following steps of:
step 1: acquiring liquid level height data in the fiber grating pressure sensor by using a linear relation between the wavelength drift amount and the liquid level height;
and 2, step: performing segmentation processing on the acquired liquid level height data, drawing a liquid level height data-measured liquid level height comparison graph, and calculating Pearson correlation coefficients among the measured liquid level heights;
and step 3: automatically correcting the initial liquid level height to a corrected liquid level height according to the Pearson correlation coefficient, taking the currently measured liquid level height as a real liquid level height, and calculating an error between the corrected liquid level height and the real liquid level height;
and 4, step 4: and performing arithmetic mean processing on the error between the corrected liquid level height and the real liquid level height, and performing error compensation on data obtained by the arithmetic mean processing to obtain the compensated measured liquid level height.
In order to better implement the present invention, further, the specific operations of step 1 are: the Bragg wavelength drift amount of the fiber bragg grating pressure sensor immersed in liquid is linearly related to the height from the liquid level, and a unitary linear regression algorithm is combined to obtain liquid level height data.
In order to better implement the present invention, further, the step 2 specifically includes the following steps:
step 2.1: and (3) carrying out sectional processing on the acquired liquid level height data, taking every 1cm as a processing interval, and expressing the measured liquid level height as:
Hi＝{h1，h2，h3......，hk|k∈Z}
wherein HiFor the measured level height obtained at the i-th time, hkThe measured liquid level height corresponding to the real liquid level height of kcm;
step 2.2: drawing a liquid level height data-measured liquid level height comparison graph;
step 2.3: respectively calculating the height H of the measured liquid level1With other groups measuring the height H of the liquid levelmPearson correlation coefficient therebetween; wherein m is greater than or equal to 2 and less than or equal to i, and m and i are positive integers.
In order to better implement the present invention, further, the operation of step 2.3 is: by calculating the measuring liquidHeight of bit H1Measuring the level height H with other groupsmCovariance of (2), other group measurement level height HmVariance of (1), other group measured level height HmAfter averaging, the measured level height H is calculated1Measuring the level height H with other groupsmPearson correlation coefficient therebetween; wherein m is greater than or equal to 2 and less than or equal to i, and m and i are positive integers.
In order to better implement the present invention, further, the step 3 specifically includes the following steps:
step 3.1: obtaining the correlation among the liquid level heights of each group of measurement according to the calculated Pearson correlation coefficient among the liquid level heights of each group of measurement;
step 3.2: automatically correcting the initial liquid level height to a corrected liquid level height;
step 3.3: taking the currently measured liquid level height as a real liquid level height;
step 3.4: let the initial true level height of the liquid level be kcm, and represent the ith corrected measured level height as:
H′i＝Hi-(hk-k)
wherein, H'iThe corrected measured liquid level height for the ith time is Hi, the measured liquid level height obtained for the ith time is hk, the measured liquid level height corresponds to the real liquid level height of kcm, and k is the initial real liquid level height of the liquid level;
step 3.5: and calculating the error between the corrected liquid level height and the real liquid level height.
In order to better implement the present invention, further, the specific operations of step 3.5 are: measuring for n times, calculating the corrected liquid level height of the n times of measurement, and calculating the error between the corrected liquid level height and the real liquid level height of the n times of measurement according to the corrected liquid level height and the real liquid level height of the n times of measurement; wherein 1 ≦ i ≦ n and n, i are positive integers.
In order to better implement the present invention, further, the step 4 specifically includes the following steps:
step 4.1: carrying out arithmetic average on the error between the corrected measured liquid level height and the actual liquid level height;
step 4.2: and (4) taking the arithmetic mean value of the error between the corrected measured liquid level height and the real liquid level height as a compensation factor to compensate the ith corrected measured liquid level height, and obtaining the final measured liquid level height.
In order to better implement the present invention, further, the specific operations of step 4.2 are: and compensating the ith corrected measured liquid level height by taking the arithmetic mean value of the error between the corrected measured liquid level height and the real liquid level height as a compensation factor, and calculating the difference value of the ith corrected measured liquid level height and the arithmetic mean value of the error between the measured liquid level height and the real liquid level height, wherein the calculated difference value is the final measured liquid level height.
In order to better implement the present invention, further, after the compensation factor is compensated in step 4, a residual error calculation process is performed on the compensated measured liquid level height and the real liquid level height, and the specific operations are as follows: and calculating the average value of the difference value between the final measured liquid level height and the real liquid level height of the n times of measurement, and taking the calculated average value as the error value of the measured liquid level height.
The invention has the following beneficial effects:
(1) the method takes the liquid level data obtained by an unary linear regression model for the liquid level measurement of the fiber bragg grating pressure sensor as a processing object, obtains the strong correlation characteristic of the liquid level measurement data by calculating the Pearson correlation coefficient, and automatically corrects the initial value of the liquid level to the same measurement height; comparing the obtained measured liquid level data with the real liquid level height data, and finally performing error compensation correction on the liquid level measured data by a segmented arithmetic average processing method of error data of each segment on the liquid level measured height, thereby greatly improving the liquid level measurement precision;
(2) the error range of the liquid level measurement by using the fiber bragg grating pressure sensor is mostly within +/-15-25 mm at present, the error can be reduced to +/-5 mm by using the algorithm, the algorithm is good in real-time performance, the liquid level measurement performance of the fiber bragg grating pressure sensor is greatly improved, and the application requirements of the fiber bragg grating pressure sensor in the liquid level measurement of large-scale equipment such as aircrafts, ships and automobiles are met;
(3) the invention adopts the error correction technology to carry out error compensation, finds that the liquid level measurement data has strong correlation and the data has the same variation trend in the test process, and adopts the compensation factor to carry out self-compensation correction on the data.
Drawings
FIG. 1 is a schematic diagram of wavelength shift of a fiber grating;
FIG. 2 is a schematic view of the pressure sensing membrane deformed by force;
FIG. 3 is a schematic diagram of liquid level height measurement of a fiber grating-based pressure sensing device;
FIG. 4 is a graph of liquid level height data results obtained by the system set-up;
FIG. 5 is a result graph of the process of correcting the measured liquid level height to the same initial height;
FIG. 6 is a diagram showing the results of the sectional compensation process for the measured liquid level height;
FIG. 7 is a residual plot of measured liquid level height after compensation and actual liquid level height;
FIG. 8 is a flow chart of a processing algorithm for self-compensating correction of liquid level measurement errors based on a fiber grating pressure sensor.
Detailed Description
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and therefore should not be considered as a limitation to the scope of protection. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
Example 1:
the embodiment provides a method for compensating and correcting a liquid level measurement error of a pressure sensor based on fiber bragg grating, as shown in fig. 1, 2 and 8, the method comprises the following steps:
step 1: acquiring liquid level height data in the fiber grating pressure sensor by using a linear relation between the wavelength drift amount and the liquid level height;
and 2, step: performing segmentation processing on the acquired liquid level height data, drawing a liquid level height data-measured liquid level height comparison graph, and calculating a Pearson correlation coefficient among each group of liquid level height data;
and 3, step 3: automatically correcting the initial liquid level height to the same measurement height according to the calculated Pearson correlation coefficient among the liquid level height data of each group, taking the current measurement height as the real liquid level height, and calculating the error between the corrected liquid level height and the real liquid level height;
and 4, step 4: and performing arithmetic mean processing on the error between the corrected liquid level height and the real liquid level height, and performing error compensation on data obtained by the arithmetic mean processing to obtain the compensated liquid level measurement height.
The working principle is as follows: FIG. 8 is a flow chart of a process of a fiber grating pressure sensor-based liquid level measurement error compensation algorithm. The overall operation process of the compensation algorithm is systematically introduced, the initial liquid level data is firstly obtained, the initial liquid level height is corrected to be the same numerical value according to the characteristic of strong correlation, the error between the processed data and the real liquid level data height is calculated to obtain a correction factor, and the processed data is compensated by the correction factor, so that the measurement precision is greatly improved, and the error range is controlled within +/-5 mm.
Fig. 1 shows a schematic diagram of the fiber grating pressure sensing principle and the grating wavelength drift. The left side of fig. 1 illustrates that when the external pressure changes, the period of the fiber grating and the fiber core of the optical fiber will be changed, thereby causing the shift of the central wavelength of the fiber grating. The rear-end signal demodulation equipment can realize high-precision monitoring on the wavelength drift amount, so that the pressure change can be accurately reflected. The right side is a schematic diagram of the stress deformation of the pressure sensing film of the fiber bragg grating pressure sensor. When the liquid level increases, the pressure difference of two sides of the pressure sensing film increases, the pressure sensing film with the diameter of 2r and the thickness of t deforms, the fiber grating embedded in the pressure sensing film deforms and bends, the central wavelength of the fiber grating drifts, the pressure difference of two sides of the pressure sensing film can be obtained by measuring the central wavelength drift of the fiber grating, and the liquid level height is further obtained.
Fig. 2 is a schematic diagram for measuring the liquid level height of the pressure sensing device based on the fiber bragg grating. All sensors in the fiber bragg grating pressure sensor liquid level measuring device are arranged at equal intervals, and each fiber bragg grating pressure sensor is placed at a fixed height. The amount of bragg wavelength drift of the fiber grating pressure sensor immersed in the liquid is linear with the height from the liquid level, while the amount of bragg wavelength drift of the fiber grating pressure sensor not immersed in the liquid is zero. The linear fitting equation of the fiber bragg grating pressure sensor is obtained by measuring the Bragg wavelength value of the fiber bragg grating pressure sensor immersed in liquid and combining a unary linear regression algorithm for calculation. The intercept of the linear fitting equation is the current liquid level value, and the two parameters of the density and the gravity acceleration of the liquid only change the slope of the linear fitting equation, so that the liquid level measurement precision is not influenced.
Example 2:
based on the foregoing embodiment 1, as shown in fig. 3, the specific operations of step 1 are as follows: the method comprises the following steps of utilizing the Bragg wavelength drift amount of a fiber grating pressure sensor immersed in liquid to form a linear relation with the height from the liquid level, combining a unitary linear regression algorithm to obtain liquid level height data h, and obtaining a specific calculation formula as follows:
h＝k*Δλ+h0
wherein h is liquid level height data, k is sensor sensitivity, delta lambda is fiber grating central wavelength variation, h0Is the current liquid level height value when Δ λ is 0.
Further, the specific steps of step 2 are:
step 2.1: the acquired liquid level height data is processed in sections, and each 1cm is taken as a processing interval, and the liquid level height is expressed as:
Hi＝{h1，h2，h3......，hk|k∈Z}
wherein HiFor the measured level height data obtained at the ith time, hkThe measured liquid level height corresponding to the real liquid level height of kcm;
step 2.2: drawing a liquid level height data-measured liquid level height comparison graph;
step 2.3: respectively calculating the height data H of the measured liquid level1With other sets of measured data HiPearson correlation coefficient between i ≠ 1.
Further, the specific calculation formula of step 2.3 is:
wherein, r (H)1，Hi) Represents H1And HiPearson's correlation coefficient, Cov (H)1，Hi) Is represented by H1And HiCovariance of (1), Var (H)i) Is represented by HiThe variance of (a) is determined,
is represented by HiAverage value of (a).
The working principle is as follows: FIG. 3 is a graph of liquid level height data results obtained by the system set-up.
By the formula
h＝k*Δλ+h0
A delta lambda curve when the liquid level height changes is obtained through a measurement spectrometer, and then the change curves of the fiber grating pressure sensor arrays immersed in the liquid at different heights are estimated through a linear fitting mode. The obtained liquid level height data is processed in sections, each 1cm of the real liquid level height is taken as a processing interval, and the liquid level height is divided into
Hi＝{h1，h2，h3……，hk|k∈Z}
HiMeasured level height data for the ith measurement，hkKcm, the corresponding measured liquid level height. And drawing a comparison graph of measurement data and the real liquid level height. The experiment totally carries out 6 times of data acquisition, and the real height of the initial liquid level measured each time is 90 cm.
In actual measurement, because each time Δ λ has a certain fluctuation, a measurement error is large, and a certain fitting correction needs to be performed on a measurement result. Respectively calculating the height data H of the measured liquid level1With other sets of measured data HiAnd the Pearson correlation coefficient between i ≠ 1, and the specific calculation formula is as follows:
wherein r (H)1，Hi) Represents H1And HiPearson's correlation coefficient of (Cov) (H)1，Hi) Is represented by H1And HiCovariance of (2), Var (H)i) Represents HiThe variance of (a) is calculated,
represents HiThe calculated pearson correlation coefficient is shown in table 1.
TABLE 1H1And HiPearson's correlation coefficient
| r(H1，H2) | r(H1，H3) | r(H1，H4) | r(H1，H5) | r(H1，H5) |
| 0.999856311 | 0.999813559 | 0.99990512 | 0.999856885 | 0.999882952 |
It can be obtained that the six groups of data have strong correlation, the variation trend of the data is linear and the same, and only because the obtained intercept is different due to the fluctuation of the delta lambda, so that the data are corrected.
Other parts of this embodiment are the same as those of embodiment 1, and thus are not described again.
Example 3:
in this embodiment, on the basis of any one of the above embodiments 1-2, as shown in fig. 4, the specific steps of step 3 are:
step 3.1: obtaining the correlation among the liquid level height data according to the calculated Pearson correlation coefficient among the liquid level height data;
step 3.2: automatically correcting the initial liquid level height to the same measurement height;
step 3.3: taking the current measurement height as the real liquid level height;
step 3.4: let the initial true height of the liquid level be kcm, and represent the height of the liquid level measurement after the ith correction as:
H′i＝Hi-(hk-k)
step 3.5: and calculating the error between the corrected liquid level height and the real liquid level height.
In order to better implement the present invention, further, the specific calculation formula of step 3.5 is:
ρi＝{H′i-R|i＝1......n}
where ρ isiAnd n is the number of measurement times, and R is the real liquid level height R ═ 1, 2, 3.
The working principle is as follows: FIG. 4 is a graph of the results of the calibration of the level measurement height to the same starting height. The initial true liquid level height is kcm, where we take k 90, then the ith corrected liquid level measurement height H'i＝Hi-(hk-k). The corrected liquid level height H'iAnd drawing a comparison graph with the real liquid level height. At this point, we found H'iThe coincidence ratio between the two liquid levels is already high, but a certain error exists between the two liquid levels and the real liquid level height R {1, 2, 3. Calculating the error rho, rho between the corrected liquid level measurement height and the true liquid level height Ri＝{H′iN is the number of measurements, this time we take n 6.
Other parts of this embodiment are the same as any of embodiments 1-2 described above, and thus are not described again.
Example 4:
in this embodiment, on the basis of any one of the above embodiments 1 to 3, as shown in fig. 5, the specific steps of step 4 are as follows:
step 4.1: error rhoiArithmetic mean was performed to obtain:
wherein the content of the first and second substances,
is the error piArithmetic mean of (1) () piN is the measurement frequency for the error between the corrected liquid level height and the real liquid level height;
and 4.2: will be provided with
As compensation factor to H'iAnd (5) compensating to obtain the final liquid level measurement height H.
In order to better implement the present invention, further, the specific calculation formula of step 4.2 is:
wherein, H'iThe height is measured for the liquid level after the ith correction,
is the error piIs calculated as the arithmetic average of (a).
The working principle is as follows: FIG. 5 is a diagram showing the results of a process of compensating the height of the liquid level measurement by stages. Error rhoiPerforming arithmetic mean to obtain
Will be provided with
As compensation factor to H'iAnd (5) compensating to obtain the final liquid level measurement height H. The specific compensation algorithm is
After compensation, we can see that the goodness of fit of H and R is very high, and the two curves almost coincide.
Other parts of this embodiment are the same as any of embodiments 1 to 3, and thus are not described again.
Example 5:
on the basis of any one of the foregoing embodiments 1 to 4, as shown in fig. 6, after the compensation factor in step 4 is compensated, the present embodiment further performs residual error calculation processing on the compensated liquid level height and the actual liquid level height, where the specific calculation formula is as follows:
wherein, σ is a liquid level measurement height error value, H is a final liquid level measurement height, R is a real liquid level height, and n is the number of measurements.
The working principle is as follows: FIG. 6 is a residual plot of compensated level measurement height versus actual level height. In order to further obtain the lifting condition of the measurement precision, residual error calculation processing is carried out on the compensated liquid level height and the actual liquid level height, and the specific calculation formula is
The integral error does not exceed 10mm, and the measurement precision reaches within +/-5 mm. The measured liquid level accurately reflects the true value of the liquid level, and the algorithm has excellent real-time performance.
Other parts of this embodiment are the same as any of embodiments 1 to 4, and thus are not described again.
Example 6:
on the basis of any one of the above embodiments 1 to 5, as shown in fig. 1, fig. 2, fig. 3, fig. 4, fig. 5, fig. 6, fig. 7, fig. 8, and the accompanying drawings, the present embodiment further provides a method for compensating and correcting an error in liquid level measurement based on a fiber bragg grating pressure sensor, including the following steps:
step 1: acquiring liquid level height data in the fiber bragg grating pressure sensor by using a linear relation between the wavelength drift amount and the liquid level height;
and 2, step: performing segmentation processing on the acquired liquid level height data, drawing a liquid level height data-measured liquid level height comparison graph, and calculating a Pearson correlation coefficient between the heights of all groups of measured liquid levels;
and 3, step 3: automatically correcting the initial liquid level height to a corrected liquid level height according to the Pearson correlation coefficient, taking the currently measured liquid level height as a real liquid level height, and calculating an error between the corrected liquid level height and the real liquid level height;
and 4, step 4: and performing arithmetic mean processing on the error between the corrected liquid level height and the real liquid level height, and performing error compensation on data obtained by the arithmetic mean processing to obtain the compensated measured liquid level height.
Further, the specific operation of step 1 is: the Bragg wavelength drift amount of the fiber bragg grating pressure sensor immersed in the liquid is linearly related to the height from the liquid level, and a unitary linear regression algorithm is combined to obtain liquid level height data.
Further, the step 2 specifically includes the following steps:
step 2.1: and (3) carrying out sectional processing on the acquired liquid level height data, taking every 1cm as a processing interval, and expressing the measured liquid level height as:
Hi＝{h1，h2，h3......，hk|k∈Z}
wherein Hi is the height of the measured liquid level obtained at the ith time, and hk is the height of the measured liquid level corresponding to the real liquid level height of kcm;
step 2.2: drawing a liquid level height data-measured liquid level height comparison diagram;
step 2.3: respectively calculating Pearson correlation coefficients between the measured liquid level height H1 and the other groups of measured liquid level heights Hm; wherein m is greater than or equal to 2 and less than or equal to i, and m and i are positive integers.
Further, the operation of step 2.3 is: by calculating the height H of the measured liquid level1Measuring the level height H with other groupsmCovariance of (2), other set of measured level heights HmVariance of (1), other group measured level height HmAfter averaging, the measured liquid level height H is calculated1Measuring the level height H with other groupsmPearson correlation coefficient therebetween; wherein m is greater than or equal to 2 and less than or equal to i, and m and i are both positive integers.
Further, the step 3 specifically includes the following steps:
step 3.1: obtaining the correlation among the liquid level heights of each group of measurement according to the calculated Pearson correlation coefficient among the liquid level heights of each group of measurement;
step 3.2: automatically correcting the initial liquid level height to a corrected liquid level height;
step 3.3: taking the currently measured liquid level height as a real liquid level height;
step 3.4: let the initial true level height of the liquid level be kcm, and represent the corrected measured level height after the ith time as:
H′i＝Hi-(hk-k)
wherein, H'iThe corrected measured liquid level height at the ith time is Hi, the measured liquid level height obtained at the ith time is hk, the true liquid level height is kcm, and the k is the initial true liquid level height of the liquid level;
step 3.5: and calculating the error between the corrected liquid level height and the real liquid level height.
Further, the specific operation of step 3.5 is: measuring for n times, calculating the corrected liquid level height of the n times of measurement, and calculating the error between the corrected liquid level height and the real liquid level height of the n times of measurement according to the corrected liquid level height and the real liquid level height of the n times of measurement; wherein 1 ≦ i ≦ n and n, i are positive integers.
Further, the step 4 specifically includes the following steps:
step 4.1: carrying out arithmetic mean on the error between the corrected measured liquid level height and the actual liquid level height;
step 4.2: and (4) taking the arithmetic mean value of the error between the corrected measured liquid level height and the real liquid level height as a compensation factor to compensate the ith corrected measured liquid level height, and obtaining the final measured liquid level height.
Further, the specific operation of step 4.2 is: and compensating the ith corrected measured liquid level height by taking the arithmetic mean value of the error between the corrected measured liquid level height and the real liquid level height as a compensation factor, and calculating the difference value of the ith corrected measured liquid level height and the arithmetic mean value of the error between the measured liquid level height and the real liquid level height, wherein the calculated difference value is the final measured liquid level height.
Furthermore, after the compensation factor in step 4 is compensated, a residual error calculation process is performed on the compensated measured liquid level height and the real liquid level height, and the method specifically operates as follows: and calculating the average value of the difference value between the final measured liquid level height and the real liquid level height of the n times of measurement, and taking the calculated average value as the error value of the measured liquid level height.
The working principle is as follows: the embodiment provides an error self-compensation correction algorithm applied to fiber grating pressure sensor liquid level measurement, liquid level data obtained by a unitary linear regression model of the fiber grating pressure sensor liquid level measurement are taken as processing objects, the strong correlation characteristic of the measured liquid level height data is obtained by calculating Pearson correlation coefficients of all groups of measured liquid level heights, and the initial liquid level value is automatically corrected to be the same measured height. And comparing the obtained liquid level data with the real data, and finally performing arithmetic average processing on each section of error data on the liquid level measurement height in a segmentation manner to perform error compensation correction on the liquid level measurement data, thereby greatly improving the liquid level measurement precision. The error range of the liquid level measurement by using the fiber bragg grating pressure sensor is mostly within +/-15-25 mm at present, the error can be reduced to +/-5 mm by using the algorithm, the algorithm is good in real-time performance, the performance of the liquid level measurement of the fiber bragg grating pressure sensor is greatly improved, and the application requirements of the liquid level measurement of large-scale equipment such as aircrafts, ships and automobiles are met.
Other parts of this embodiment are the same as any of embodiments 1 to 5, and thus are not described again.
The embodiment of the invention lists a specific implementation method based on a fiber grating pressure sensor liquid level measurement error self-compensation correction algorithm, the data acquisition times in the algorithm steps of the method can be selected and adjusted according to actual conditions, and the method can be used for self-compensation correction based on the fiber grating pressure sensor liquid level measurement error and can also be used for other error processing based on data obtained by a unitary linear regression algorithm.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and all simple modifications and equivalent variations of the above embodiments according to the technical spirit of the present invention are included in the scope of the present invention.
Claims (9)
1. A liquid level measurement error compensation correction method based on a fiber bragg grating pressure sensor is characterized by comprising the following steps:
step 1: acquiring liquid level height data in the fiber bragg grating pressure sensor by using a linear relation between the wavelength drift amount and the liquid level height;
step 2: performing segmentation processing on the acquired liquid level height data, drawing a liquid level height data-measured liquid level height comparison graph, and calculating Pearson correlation coefficients among the measured liquid level heights;
and step 3: automatically correcting the initial liquid level height to a corrected liquid level height according to the Pearson correlation coefficient, taking the currently measured liquid level height as a real liquid level height, and calculating an error between the corrected liquid level height and the real liquid level height;
and 4, step 4: and performing arithmetic mean processing on the error between the corrected liquid level height and the real liquid level height, and performing error compensation on data obtained by the arithmetic mean processing to obtain the compensated measured liquid level height.
2. The fiber bragg grating pressure sensor-based liquid level measurement error compensation correction method as claimed in claim 1, wherein the specific operations of the step 1 are as follows: the Bragg wavelength drift amount of the fiber bragg grating pressure sensor immersed in the liquid is linearly related to the height from the liquid level, and a unitary linear regression algorithm is combined to obtain liquid level height data.
3. The fiber bragg grating pressure sensor-based liquid level measurement error compensation and correction method of claim 1, wherein the step 2 specifically comprises the following steps:
step 2.1: the acquired liquid level height data is processed in a segmented mode, each 1cm is taken as a processing interval, and the measured liquid level height is expressed as:
Hi＝{h1，h2，h3......，hk|k∈Z}
wherein HiFor the measured level height obtained for the ith time, hkThe measured liquid level height corresponding to the real liquid level height of kcm;
step 2.2: drawing a liquid level height data-measured liquid level height comparison diagram;
step 2.3: respectively calculating the height H of the measured liquid level1With other groups measuring the height H of the liquid levelmPearson correlation coefficient therebetween; wherein m is greater than or equal to 2 and less than or equal to i, and m and i are positive integers.
4. A fiber grating pressure sensor based liquid level measurement error compensation correction method as claimed in claim 3, characterized in that the operation of step 2.3 is: by calculating the height H of the measured liquid level1Measuring the level height H with other groupsmCovariance of (2), other group measurement level height HmVariance of (2), other group measurement level height HmAfter averaging, the measured liquid level height H is calculated1Measuring the level height H with other groupsmPearson correlation coefficient therebetween; wherein m is greater than or equal to 2 and less than or equal to i, and m and i are both positive integers.
5. The fiber grating pressure sensor-based liquid level measurement error compensation correction method of claim 3, wherein the step 3 specifically comprises the following steps:
step 3.1: obtaining the correlation among the liquid level heights of each group of measurement according to the calculated Pearson correlation coefficient among the liquid level heights of each group of measurement;
step 3.2: automatically correcting the initial liquid level height to a corrected liquid level height;
step 3.3: taking the currently measured liquid level height as a real liquid level height;
step 3.4: let the initial true level height of the liquid level be kcm, and represent the ith corrected measured level height as:
Hi＝Hi-(hk-k)
wherein, H'iFor the height of the measured level after the i-th correction, HiIs the ith timeHeight of the measured liquid level obtained, hkThe measured liquid level height corresponding to the real liquid level height of kcm, and k is the initial real liquid level height of the liquid level;
step 3.5: and calculating the error between the corrected liquid level height and the real liquid level height.
6. The fiber grating pressure sensor based liquid level measurement error compensation correction method of claim 5, wherein the specific operations of step 3.5 are as follows: measuring for n times, calculating the corrected liquid level height of the n times of measurement, and calculating the error between the corrected liquid level height and the real liquid level height of the n times of measurement according to the corrected liquid level height and the real liquid level height of the n times of measurement; wherein 1 ≦ i ≦ n and n, i are positive integers.
7. The fiber bragg grating pressure sensor based liquid level measurement error compensation correction method as claimed in claim 6, wherein the step 4 specifically comprises the following steps:
step 4.1: carrying out arithmetic mean on the error between the corrected measured liquid level height and the actual liquid level height;
step 4.2: and compensating the ith corrected measured liquid level height by taking the arithmetic average value of the error between the corrected measured liquid level height and the real liquid level height as a compensation factor to obtain the compensated measured liquid level height.
8. The fiber bragg grating pressure sensor based liquid level measurement error compensation correction method as claimed in claim 7, wherein the specific operations of the step 4.2 are as follows: and compensating the ith corrected measured liquid level height by taking the arithmetic mean value of the error between the corrected measured liquid level height and the real liquid level height as a compensation factor, calculating the difference value of the ith corrected measured liquid level height and the arithmetic mean value of the error between the measured liquid level height and the real liquid level height, and taking the calculated difference value as the compensated measured liquid level height.
9. The fiber grating pressure sensor-based liquid level measurement error compensation and correction method of claim 8, wherein after the compensation factor is compensated in step 4, a residual error calculation process is further performed on the compensated measured liquid level height and the true liquid level height, and the method is specifically operated as follows: and calculating the average value of the difference value between the compensated measured liquid level height and the real liquid level height after n times of measurement, and taking the calculated average value as the error value of the measured liquid level height.
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