CN115683284A - Method for inhibiting false echo and liquid level measuring system - Google Patents
Method for inhibiting false echo and liquid level measuring system Download PDFInfo
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- CN115683284A CN115683284A CN202211704481.5A CN202211704481A CN115683284A CN 115683284 A CN115683284 A CN 115683284A CN 202211704481 A CN202211704481 A CN 202211704481A CN 115683284 A CN115683284 A CN 115683284A
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Abstract
The invention relates to a method for inhibiting false echoes, which comprises the steps of preliminarily screening echo signals to obtain a plurality of alternative echoes, scoring each alternative echo with confidence coefficient, selecting the alternative echo with the highest confidence coefficient score as a real echo, and judging the rest echoes as false echoes, wherein the confidence coefficient score is composed of an echo energy score, an echo time sequence score and an echo width score. The method of the invention carries out preliminary screening on the echo signals, then uses three evaluation standards which can effectively judge whether the echo signals are real signals, and combines and selects the echo which is most likely to be the real signal, thereby automatically inhibiting the false echo without independently learning and configuring a new time change threshold curve aiming at the environment of each liquid level measurement.
Description
Technical Field
The invention belongs to the technical field of liquid level measurement, and particularly relates to a method for inhibiting false echoes and a liquid level measurement system.
Background
When an ultrasonic liquid level meter is used for measurement in a drainage pipe network, the working principle of the ultrasonic liquid level meter is to send ultrasonic waves to liquid and calculate the reflection distance according to the time delay of echo waves. However, the reflected wave energy value fluctuates greatly due to various changes of the liquid level reflecting surface, the underground sewage environment is complex, and a plurality of obstacles are arranged on the well wall, so that real echoes are inevitably superposed with false reflected echoes of various obstacles in the well, the peak values of the ultrasonic echoes are uneven, the ultrasonic echoes are reflected as increased jitter of a liquid level measuring result, and therefore, the influence of the false echoes is restrained by using a corresponding method.
The method for inhibiting the false echo used in the current ultrasonic liquid level meter generally performs a pre-test on the whole sound propagation path in the working environment of equipment in advance, namely, the arrival time and energy of the reflected wave corresponding to all obstacles are obtained, so that the internal algorithm of the liquid level meter learns the false echo in the known obstacle environment, a new time change threshold curve (TVT curve) of background noise is formed, the confidence threshold is improved at the position with large interference, the false echo is automatically covered, and the effect of shielding and fixing the interference echo is achieved.
However, the method has obvious limitations, firstly, reflected wave information of the whole sound propagation path barrier under the current working environment must be obtained, but the requirement is difficult to meet under the actual environment, for example, when the liquid level of a sewage well is measured, the sewage well is difficult to dry so as to expose the whole underground environment for testing; secondly, the TVT curve obtained after each learning is only used for the environment, the universality is not realized, the learning needs to be carried out again after the working place is changed, and the labor cost is increased.
Disclosure of Invention
Based on the above disadvantages and shortcomings of the prior art, it is an object of the present invention to at least solve one or more of the above problems in the prior art, or to provide a method for suppressing false echo and a level measuring system, which satisfy one or more of the above requirements.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a method for suppressing false echoes, where the method specifically includes:
carrying out primary screening on the echo signals to obtain a plurality of alternative echoes;
performing confidence score on each alternative echo respectively;
selecting the alternative echo with the highest confidence score as a real echo, and judging the rest echoes as false echoes;
the confidence score is composed of an echo energy score, an echo timing score and an echo width score.
As a preferred scheme, the preliminary screening of the echo signals specifically includes:
creating an echo suppression threshold curve;
acquiring an envelope curve of an echo signal;
calculating the maximum value of the envelope curve, and creating a relative threshold according to the maximum value;
and keeping the echo which is larger than the echo suppression threshold curve and is larger than the relative threshold as the alternative echo.
As a further preferable scheme, the echo suppression threshold curve is specifically a residual value of the sound intensity of the excitation signal after attenuation by a preset distance.
As a further preferred scheme, the method for calculating the echo energy score specifically comprises the following steps:
acquiring the sound intensity and the echo time delay of an echo;
acquiring an echo suppression threshold corresponding to the echo time delay in an echo suppression threshold curve;
and calculating the score according to the ratio of the sound intensity of the echo to the echo suppression threshold value.
As a preferred scheme, the method for calculating the echo time sequence score specifically includes:
and calculating the score according to the arrival sequence of the echoes, wherein the score is gradually reduced backwards along with the time sequence.
As a preferred scheme, the method for calculating the echo width score specifically includes:
acquiring the width of an echo and the pulse width of an excitation signal;
the score is calculated from the ratio of the width of the echo to the pulse width of the excitation signal.
In a second aspect, the present invention further provides a liquid level measuring system for suppressing false echo, specifically comprising:
the ultrasonic liquid level meter is used for sending an excitation signal and receiving an echo;
the echo screening module is used for primarily screening echo signals to obtain a plurality of alternative echoes;
the echo scoring module is used for scoring the confidence of each alternative echo;
the filtering module is used for selecting the alternative echo with the highest confidence score as a real echo and judging the rest echoes as false echoes;
the calculation module is used for calculating the liquid level according to the real echo;
the echo scoring module consists of an echo energy scoring unit, an echo time sequence scoring unit and an echo width scoring unit.
As a preferred scheme, the echo screening module specifically includes:
the echo suppression threshold curve creating unit is used for creating an echo suppression threshold curve;
the envelope calculation unit is used for acquiring an envelope curve of the echo signal;
the relative threshold setting unit is used for calculating the maximum value of the envelope curve and creating a relative threshold according to the maximum value;
and the filtering unit is used for keeping the echoes which are larger than the echo suppression threshold curve and larger than the relative threshold as the alternative echoes.
Compared with the prior art, the invention has the beneficial effects that:
the method and the liquid level measurement system of the invention carry out preliminary screening on the echo signals, then use three evaluation standards which can effectively judge whether the echo signals are real signals, and combine and select the echo which is most likely to be the real signal, thereby automatically inhibiting false echo without independently learning and configuring a new time change threshold curve aiming at the environment of each liquid level measurement.
Drawings
FIG. 1 is a schematic diagram of a prior art ultrasonic level gauge for dealing with false echoes;
fig. 2 is a schematic diagram of screening real echoes by a method for suppressing false echoes according to an embodiment of the present application.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application.
In the following description, a plurality of embodiments of the present application are provided, and different embodiments may be replaced or combined, and thus the present application is also considered to include all possible combinations of the same and/or different embodiments described. Thus, if one embodiment includes features a, B, C and another embodiment includes features B, D, then this application should also be construed to include embodiments that include all other possible combinations of one or more of a, B, C, D, although such embodiments may not be explicitly recited in the following text.
The following description provides examples, and does not limit the scope, applicability, or examples set forth in the claims. Changes may be made in the function and arrangement of elements described without departing from the scope of the disclosure. Various examples may omit, substitute, or add various procedures or components as appropriate. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Furthermore, features described with respect to some examples may be combined into other examples.
Before explaining specific embodiments of the present application in detail, an application scenario of the present application is described in order to facilitate better understanding of the embodiments of the present application.
Fig. 1 is a schematic diagram of a conventional ultrasonic level gauge for processing false echoes, wherein two signal curves exist, an echo signal curve is positioned below, and an echo suppression threshold curve (TVT curve) for suppressing false echoes, namely an echo suppression threshold curve is positioned above.
As can be seen from the figure, the TVT curve has a complex configuration, and after the detection and simulation of the surrounding environment, the TVT curve is designed specifically to approximately match the trend of the false echo in the echo signal curve, so as to suppress the false echo, and only one peak of the real echo signal higher than the TVT curve is reserved, so as to calculate the level of the medium according to the time delay of the peak.
The TVT curve of the ultrasonic liquid level meter in the prior art needs to simulate the trend of false echo, a large amount of setting and presetting are needed before practical application, and the ultrasonic liquid level meter is inconvenient and complex to use.
The application provides a method for suppressing false echo, which specifically comprises the following steps:
s1, carrying out primary screening on echo signals to obtain a plurality of alternative echoes.
In some preferred embodiments of the present application, the preliminary screening of the echo signals in step S1 specifically includes the following steps:
s11, creating an echo suppression threshold curve, wherein the echo suppression threshold curve is created according to the attenuation theory of sound waves in air.
The sound intensity of the echo gradually decreases in an exponential manner as the propagation distance of the excitation signal and the echo thereof increases, and the law is that the initial sound intensityI 0 At a passing distancedAfter that, the absorption attenuation becomesIThe attenuation formula is shown as follows:
After the function of the attenuation of the echo sound intensity along with the distance is used as the echo suppression threshold curve, because the sound intensity of the real echo signal is certainly greater than the sound intensity after the attenuation of a certain distance, the echo with the sound intensity obviously lower than unreasonable intensity in the echo signal can be easily screened out according to the sound intensity of the real echo signal and the value of the echo suppression threshold curve at the received time point.
S12, acquiring an envelope curve of the echo signal, and converting the received echo signal into the envelope curve for subsequent analysis;
s13, calculating a maximum value of the envelope curve, and creating a relative threshold according to the maximum value;
specifically, step S13 takes the maximum value in the envelope curve, and sets a certain proportion of the maximum value as a relative threshold, and only the echo with the sound intensity greater than the relative threshold has a possibility of being a real echo.
S14, the echoes which are larger than the echo suppression threshold value curve and the relative threshold are reserved as alternative echoes, and only the echoes with the sound intensity simultaneously meeting the echo suppression threshold value curve and the relative threshold are saved as alternative objects for subsequent algorithm judgment.
And S2, performing step S2 by using the alternative echoes obtained in the step S1, and performing confidence score on each alternative echo respectively, wherein the confidence score consists of an echo energy score, an echo time sequence score and an echo width score.
Specifically, in a preferred embodiment of the present application, the method for calculating the echo energy score specifically includes:
acquiring the sound intensity and the echo time delay of an echo;
acquiring an echo suppression threshold corresponding to the echo time delay in an echo suppression threshold curve;
and calculating the score according to the ratio of the sound intensity of the echo to the echo suppression threshold value.
Since the echo intensity is smaller when the sound wave has longer propagation time, if the real energy value is directly used for scoring, it is possible that the propagation time is longer and the amplitude is seriously smaller when the real echo timing sequence is extremely late, and thus the score of the echo energy score is seriously smaller, which is not in accordance with the actual confidence. Therefore, in the embodiment, the relative energy value is used as the echo energy, and since the echo suppression threshold curve is changed according to the attenuation trend of the sound wave, the ratio of the echo energy at different time points to the corresponding echo suppression threshold can reflect the true confidence of the echo energy.
The specific formula can be:
wherein Energy therein n For the true energy corresponding to the nth candidate echo, TVT n For the echo suppression threshold corresponding to that echo,RelativeEnergy n is the relative energy.
Meanwhile, in the preferred embodiment, the method for calculating the echo time sequence score specifically includes:
and calculating the score according to the sequence of the arrival of the echoes, wherein the score is gradually reduced backwards along with the time sequence. Since the earlier an echo arrives the higher the confidence that it is a true echo, the earlier the timing of the echo in the echo timing score the higher the score.
In addition, in the preferred embodiment, the method for calculating the echo width score specifically includes:
acquiring the width of an echo and the pulse width of an excitation signal;
the score is calculated from the ratio of the width of the echo to the pulse width of the excitation signal.
If the sound wave emitted by the ultrasonic probe passes through a large-area reflecting surface, the width of the echo of the sound wave should be close to the pulse width of the excitation signal; but since the echo will inevitably be affected by multipath effects, the latter half of the echo will be broadened in different ranges. In order to solve the influence of this situation on the echo determination, in this embodiment, the maximum value point of each echo to the initial position where the echo energy starts to be accumulated is used as the width of the echo, the pulse width of the excitation signal is simultaneously obtained, and then the echo width score is calculated by using the relative width, that is, the ratio of the width of the echo to the pulse width of the excitation signal.
Since echoes closer to the pulse width of the excitation signal are more likely to be true echoes, the calculation formula for the echo width score can be set as:
After the echo energy score, the echo time sequence score and the echo width score are respectively obtained through calculation by using the method, the three scores are combined to obtain a comprehensive confidence score for evaluating each echo as a real echo.
Specifically, the confidence score may be calculated as:
The following table gives an example of the calculation of confidence scores in one embodiment of the present application:
and S3, selecting the alternative echo with the highest confidence score as a real echo, and judging the rest echoes as false echoes. Fig. 2 is a schematic diagram illustrating that a real echo is obtained by performing the preliminary screening in step S1 and the confidence score screening in step S3 on a candidate echo according to an embodiment of the present application. In the above example of calculating the confidence score, since the confidence score of Echo No5 Echo is the highest, it is determined as a true Echo.
And finally, the real echo obtained by screening can be used for calculating the distance between the liquid level and the ultrasonic liquid level meter, and the distance H between the ultrasonic probe and the liquid level can be calculated by combining the time difference tau of receiving and transmitting the sound wave and the sound velocity c:
in a second aspect of the present invention, the present invention further provides a false echo suppression liquid level measurement system, for performing a false echo suppression method in liquid level measurement, specifically including:
the ultrasonic liquid level meter is used for sending an excitation signal and receiving an echo;
the echo screening module is used for primarily screening echo signals to obtain a plurality of alternative echoes;
the echo scoring module is used for scoring the confidence degree of each alternative echo;
the filtering module is used for selecting the alternative echo with the highest confidence score as a real echo and judging the rest echoes as false echoes;
the calculation module is used for calculating the liquid level according to the real echo;
the echo scoring module consists of an echo energy scoring unit, an echo time sequence scoring unit and an echo width scoring unit.
In a preferred embodiment, the echo screening module specifically includes:
an echo suppression threshold curve creation unit for creating an echo suppression threshold curve;
the envelope calculation unit is used for acquiring an envelope curve of the echo signal;
the relative threshold setting unit is used for calculating the maximum value of the envelope curve and creating a relative threshold according to the maximum value;
and the filtering unit is used for keeping the echoes which are larger than the echo suppression threshold curve and larger than the relative threshold as the alternative echoes.
It is clear to a person skilled in the art that the solution according to the embodiments of the present application can be implemented by means of software and/or hardware. The term "module" in this specification refers to software and/or hardware that can perform a specific function independently or in cooperation with other components, where the hardware may be, for example, a Field-Programmable Gate Array (FPGA), an Integrated Circuit (IC), or the like.
It should be noted that, for simplicity of description, the above-mentioned method embodiments are described as a series of acts or combination of acts, but those skilled in the art will recognize that the present application is not limited by the order of acts described, as some steps may occur in other orders or concurrently depending on the application. Further, those skilled in the art should also appreciate that the embodiments described in the specification are preferred embodiments and that the acts and modules referred to are not necessarily required in this application.
In the foregoing embodiments, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments.
In addition, functional modules in the embodiments of the present application may be integrated into one processing unit, or each module may exist alone physically, or two or more modules are integrated into one unit. The integrated module can be realized in a hardware mode, and can also be realized in a software functional module mode.
The integrated module, if implemented in the form of a software functional module and sold or used as a separate product, may be stored in a computer readable storage medium. Based on such understanding, the present application provides a computer program product, which when run on a computer, causes the computer to execute and implement all or part of the procedures in the above method embodiments.
Those of ordinary skill in the art will appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the technical solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.
The above description is merely an exemplary embodiment of the present disclosure, and the scope of the present disclosure is not limited thereto. That is, all equivalent changes and modifications made in accordance with the teachings of the present disclosure are intended to be included within the scope of the present disclosure. Embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice within the art to which the disclosure pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.
Claims (8)
1. A method for suppressing false echoes, which is used for suppressing false echoes in echo signals, and is characterized in that the method specifically comprises the following steps:
primarily screening echo signals to obtain a plurality of alternative echoes;
performing confidence score on each alternative echo respectively;
selecting the alternative echo with the highest confidence score as a real echo, and judging the rest echoes as false echoes;
the confidence score is composed of an echo energy score, an echo time sequence score and an echo width score.
2. The method for suppressing false echoes according to claim 1, wherein the preliminary screening of the echo signals specifically includes:
creating an echo suppression threshold curve;
acquiring an envelope curve of an echo signal;
calculating a maximum value of the envelope curve, and creating a relative threshold according to the maximum value;
and keeping the echo which is larger than the echo suppression threshold curve and is larger than the relative threshold as a candidate echo.
3. A method of suppressing false echoes according to claim 2, wherein the echo suppression threshold curve is a residual value of the sound intensity of the excitation signal after attenuation over a predetermined distance.
4. The method for suppressing false echoes according to claim 2, wherein the echo energy score is calculated by:
acquiring the sound intensity and the echo time delay of an echo;
acquiring an echo suppression threshold corresponding to the echo time delay in the echo suppression threshold curve;
and calculating a score according to the ratio of the sound intensity of the echo to the echo suppression threshold value.
5. The method for suppressing false echoes according to claim 1, wherein the echo timing score is calculated by:
and calculating the score according to the sequence of the arrival of the echoes, wherein the score is gradually reduced backwards along with the time sequence.
6. The method for suppressing false echoes according to claim 1, wherein the echo width score is calculated by:
acquiring the width of an echo and the pulse width of an excitation signal;
and calculating the score according to the ratio of the width of the echo to the pulse width of the excitation signal.
7. A liquid level measuring system for suppressing false echoes, which is characterized by comprising:
the ultrasonic liquid level meter is used for sending an excitation signal and receiving an echo;
the echo screening module is used for primarily screening echo signals to obtain a plurality of alternative echoes;
the echo scoring module is used for scoring the confidence degree of each alternative echo;
the filtering module is used for selecting the alternative echo with the highest confidence score as a real echo and judging the rest echoes as false echoes;
the calculation module is used for calculating the liquid level according to the real echo;
the echo scoring module is composed of an echo energy scoring unit, an echo time sequence scoring unit and an echo width scoring unit.
8. The system of claim 7, wherein the echo screening module comprises:
an echo suppression threshold curve creation unit for creating an echo suppression threshold curve;
the envelope calculation unit is used for acquiring an envelope curve of the echo signal;
the relative threshold setting unit is used for calculating the maximum value of the envelope curve and creating a relative threshold according to the maximum value;
and the filtering unit is used for reserving the echo which is larger than the echo suppression threshold curve and is larger than the relative threshold as the alternative echo.
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