CN112212997A - Ultrasonic wave flight time detection method under multipath condition for power station boiler temperature measurement - Google Patents

Ultrasonic wave flight time detection method under multipath condition for power station boiler temperature measurement Download PDF

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CN112212997A
CN112212997A CN202010980707.9A CN202010980707A CN112212997A CN 112212997 A CN112212997 A CN 112212997A CN 202010980707 A CN202010980707 A CN 202010980707A CN 112212997 A CN112212997 A CN 112212997A
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expression
boiler
temperature measurement
flight time
ultrasonic wave
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王免免
刘文红
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Shanghai Dianji University
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Shanghai Dianji University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
    • G01K11/22—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using measurement of acoustic effects
    • G01K11/24—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using measurement of acoustic effects of the velocity of propagation of sound

Abstract

The invention discloses an ultrasonic wave flight time detection method under a multipath condition for power station boiler temperature measurement, which comprises the following steps: decomposing the observed data r (t) into component quantity forms; and initializing each parameter, and iterating by adopting an EM algorithm until the parameters are converged. According to the method, Alpha stable distribution is adopted to describe signals and noise in the large boiler, and EM multipath time delay algorithm is adopted to process observation data, so that a correct time delay estimation value can be obtained, the temperature condition in the boiler can be better known, a large amount of manpower and material resources are reduced, and the working efficiency of the boiler is improved.

Description

Ultrasonic wave flight time detection method under multipath condition for power station boiler temperature measurement
Technical Field
The invention belongs to the field of signal processing, and particularly relates to an ultrasonic wave flight time detection method under a multipath condition for power station boiler temperature measurement.
Background
At present, the temperature measurement system of a large power station boiler in China is still relatively laggard, the traditional contact measurement method is single-point measurement, is not suitable for the working environment of the boiler, cannot quickly reconstruct the temperature field in the boiler, and cannot realize real-time monitoring of the temperature of the boiler. Acoustic temperature measurement is used as a non-contact temperature measurement technology, the temperature in the furnace can be monitored in real time, and consumption of manpower and material resources can be reduced.
The existing contact type temperature measurement method needs to consume a large amount of manpower and material resources, and needs workers to work in high-noise and high-intensity operation for a long time, so that the physical health of the workers is seriously influenced. And obvious multipath time delay effect exists in the boiler, the signal received by the receiver is formed by superposition of the source signal and each echo thereof, meanwhile, the interference of various noises exists, the measured temperature cannot accurately reflect the real-time temperature in the boiler, errors are easy to generate, and the working efficiency of the boiler is influenced. The correlation method is not suitable for the case that the multipath time delay interval is smaller than the reciprocal of the signal bandwidth, so the time delay estimation problem under the multipath environment at present mainly studies the high-resolution time delay estimation under the condition that the correlation cannot be solved.
Disclosure of Invention
The invention aims to provide a method for detecting ultrasonic wave flight time under a multipath condition for measuring temperature of a power station boiler, which aims to solve the problems in the prior art.
The technical scheme of the invention is that the ultrasonic wave flight time detection method under the multipath condition for the temperature measurement of the utility boiler comprises the following steps: decomposition of the observed data r (t)
Figure BDA0002687418570000011
Where s (t) is expressed as the signal source, n (t) represents the noise of unknown distribution, DkAnd mkRepresenting the time delay and attenuation factor of the K-th propagation path, K representing the number of propagation paths; for each mkAnd DkInitializing and iterating until the parameters are converged; performing the nth iteration includes the steps of:
(S1) calculating the component for each propagation path
Figure BDA0002687418570000012
The expression is as follows:
Figure BDA0002687418570000021
in the formula, betakSatisfy the constraint condition
Figure BDA0002687418570000022
(S2) optimizing the parameters of each propagation path to obtain a new one
Figure BDA0002687418570000023
And
Figure BDA0002687418570000024
and judges whether the parameters are converged, and proceeds to step (S1) if not.
In a further improvement of the present invention, in the step (S2), a new propagation path is acquired for each k-th propagation path
Figure BDA0002687418570000025
And
Figure BDA0002687418570000026
the expression of (a) is:
Figure BDA0002687418570000027
the step of solving the expression includes:
(S21) as given
Figure BDA0002687418570000028
To obtain
Figure BDA0002687418570000029
The expression is as follows:
Figure BDA00026874185700000210
(S22) according to
Figure BDA00026874185700000211
Calculating new values of
Figure BDA00026874185700000212
The expression is as follows:
Figure BDA00026874185700000213
wherein the content of the first and second substances,
Figure BDA00026874185700000214
the expression of (a) is:
Figure BDA00026874185700000215
the invention has the beneficial effects that: the method can obtain the correct time delay estimated value, so that the temperature condition in the boiler can be better known, a large amount of manpower and material resources are reduced, and the working efficiency of the boiler is improved.
Drawings
FIG. 1 is a flow chart of an ultrasonic wave flight time detection method under multipath conditions for power station boiler temperature measurement.
Detailed Description
As shown in fig. 1, an embodiment of the present invention provides a method for detecting an ultrasonic wave flight time under a multipath condition for measuring temperature of a utility boiler. The method is used for improving the accuracy of temperature measurement in the boiler and improving the working efficiency of the boiler.
In large boilers, the signal and noise are most characterized by significant spikes, so a gaussian noise model cannot be used to describe the process, and Alpha stable distributions can be used to describe the signal and noise. Since the Alpha stationary distribution does not have limited second-order statistics, time delay estimation algorithms based on limited second-order statistics cannot be used.
In the method of the embodiment, in order to measure the real-time temperature in the furnace more accurately, a multipath time delay algorithm is applied under the condition of fractional low-order Alpha stable distribution, an Expectation-Maximum algorithm is adopted, and an EM algorithm is an iterative optimization strategy, and because each iteration in the calculation method is divided into two steps, one of the two steps is an expected step (E step), and the other step is a Maximum step (M step), the basic idea is as follows: firstly, estimating the value of a model parameter according to the given observation data; and then estimating the value of the missing data according to the parameter value estimated in the last step, estimating the parameter value again according to the estimated missing data and the data observed before, then iterating repeatedly until the last convergence is reached, and ending the iteration.
Specifically, the method of the present embodiment is used to solve the maximum likelihood estimation of incomplete data. The algorithm comprises the following specific steps:
the observed data r (t) is decomposed into
Figure BDA0002687418570000031
Where s (t) is expressed as a signal source and n (t) represents the noise of unknown distribution, which are generally independent of each other. DkAnd mkRepresents the time delay and attenuation factor of the K-th propagation path, K representing the number of propagation paths. For each mkAnd DkInitializing, and iterating by adopting an EM algorithm until the parameters are converged; performing the nth iteration includes the steps of:
(S1) extraction Step of calculating the component of each propagation path
Figure BDA0002687418570000032
The expression is as follows:
Figure BDA0002687418570000033
in the formula, betakSatisfy the constraint condition
Figure BDA0002687418570000034
βkCan be used to control the convergence rate of the algorithm to avoid algorithm failure by entering local extreme points.
(S2) maximum optimization of parameters to obtain new
Figure BDA0002687418570000035
And
Figure BDA0002687418570000036
and judges whether the parameters are converged, and proceeds to step (S1) if not.
In step (S2), a new propagation path is acquired for each k-th propagation path
Figure BDA0002687418570000037
And
Figure BDA0002687418570000038
the expression of (a) is:
Figure BDA0002687418570000039
the step of solving the expression includes:
first step according to given
Figure BDA00026874185700000310
To obtain
Figure BDA00026874185700000311
The second step is based on
Figure BDA00026874185700000312
Calculating new values of
Figure BDA00026874185700000313
Can be composed of
Figure BDA00026874185700000314
To estimate the time of the arrival of the measured data,
Figure BDA00026874185700000315
derived by derivation
Figure BDA0002687418570000041
It can be seen that
Figure BDA0002687418570000042
Is that
Figure BDA0002687418570000043
Is estimated, and
Figure BDA0002687418570000044
can be regarded as
Figure BDA0002687418570000045
Correlated output with s (t-D), thus
Figure BDA0002687418570000046
The value of (d) is the corresponding time instant at the correlation output peak.
In the traditional signal processing, a Gaussian signal model occupies a dominant position, the noise problem in a large power station boiler is considered, and Alpha stable distribution is adopted to describe the signals and the noise. The Alpha stable distribution is the only distribution which meets the generalized central limit theorem, can more accurately describe non-Gaussian noise, has stability and can accurately describe data in the boiler. Because Alpha stable distribution has no finite second-order statistic, a time delay algorithm based on the second-order statistic cannot be used, and an estimation result generates a large error, so that the multipath delay is accurately estimated by adopting an EM multipath delay method.
Fig. 1 is a flowchart of the algorithm of the present embodiment. As can be seen, r (t) is the observed signal, which is decomposed and then iterated N times, as given
Figure BDA0002687418570000047
Find out
Figure BDA0002687418570000048
Then again according to
Figure BDA0002687418570000049
Calculate out new
Figure BDA00026874185700000410
Is the time corresponding to the maximum value of the correlation output.
The foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.

Claims (2)

1. A method for detecting ultrasonic wave flight time under the multipath condition for power station boiler temperature measurement is characterized by comprising the following steps: decomposition of the observed data r (t)
Figure FDA0002687418560000011
Where s (t) is expressed as the signal source, n (t) represents the noise of unknown distribution, DkAnd mkRepresenting the time delay and attenuation factor of the K-th propagation path, K representing the number of propagation paths; for each mkAnd DkInitializing and iterating until the parameters are converged; performing the nth iteration includes the steps of:
(S1) calculating the component for each propagation path
Figure FDA0002687418560000012
The expression is as follows:
Figure FDA0002687418560000013
in the formula, betakSatisfy the constraint condition
Figure FDA0002687418560000014
(S2) optimizing the parameters of each propagation path to obtain a new one
Figure FDA0002687418560000015
And
Figure FDA0002687418560000016
and judges whether the parameters are converged, and proceeds to step (S1) if not.
2. The method for detecting the ultrasonic flight time under the multipath condition for the temperature measurement of the utility boiler according to claim 1, characterized by comprising the following steps(S2), a new path is acquired for each k-th propagation path
Figure FDA0002687418560000017
And
Figure FDA0002687418560000018
the expression of (a) is:
Figure FDA0002687418560000019
the step of solving the expression includes:
(S21) as given
Figure FDA00026874185600000110
To obtain
Figure FDA00026874185600000111
The expression is as follows:
Figure FDA00026874185600000112
(S22) according to
Figure FDA00026874185600000113
Calculating new values of
Figure FDA00026874185600000114
The expression is as follows:
Figure FDA00026874185600000115
wherein the content of the first and second substances,
Figure FDA00026874185600000116
the expression of (a) is:
Figure FDA00026874185600000117
CN202010980707.9A 2020-09-17 2020-09-17 Ultrasonic wave flight time detection method under multipath condition for power station boiler temperature measurement Pending CN112212997A (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120142375A1 (en) * 2008-11-26 2012-06-07 Andrew, Llc System and Method for Multiple Range Estimation Location
CN107870046A (en) * 2016-09-26 2018-04-03 中国石化扬子石油化工有限公司 A kind of boiler sound wave thermometric system and method
CN111537101A (en) * 2020-06-02 2020-08-14 上海电机学院 Ultrasonic wave flight time estimation method for power station boiler temperature measurement system

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120142375A1 (en) * 2008-11-26 2012-06-07 Andrew, Llc System and Method for Multiple Range Estimation Location
CN107870046A (en) * 2016-09-26 2018-04-03 中国石化扬子石油化工有限公司 A kind of boiler sound wave thermometric system and method
CN111537101A (en) * 2020-06-02 2020-08-14 上海电机学院 Ultrasonic wave flight time estimation method for power station boiler temperature measurement system

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
冯丹: "ALPHA稳定分布噪声下多径时间延迟估计算法的研究", 《中国优秀硕士学位论文全文数据库 信息科技辑》 *

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Application publication date: 20210112