CN113391302B - Dynamic double-threshold echo detection method - Google Patents
Dynamic double-threshold echo detection method Download PDFInfo
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- CN113391302B CN113391302B CN202010173753.8A CN202010173753A CN113391302B CN 113391302 B CN113391302 B CN 113391302B CN 202010173753 A CN202010173753 A CN 202010173753A CN 113391302 B CN113391302 B CN 113391302B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
- G01S7/539—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
- G01S7/52004—Means for monitoring or calibrating
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
- Y02A90/30—Assessment of water resources
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- General Physics & Mathematics (AREA)
- Radar, Positioning & Navigation (AREA)
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- Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
- Measurement Of Velocity Or Position Using Acoustic Or Ultrasonic Waves (AREA)
Abstract
The invention relates to a dynamic dual-threshold echo detection method, which comprises the steps of transmitting 7-10 excitation signals as a first group of excitation signals, and enabling ultrasonic signals to start oscillation to be in a stable state; 7 to 10 excitation signals are transmitted again at the interval time T to serve as a second group of excitation signals; acquiring echo signals corresponding to the first group of excitation signals, and measuring an amplitude value Vpp of a current echo; setting the thresholds of the dual threshold as 50% vpp and 87.5% vpp as threshold 1 and threshold 2, respectively, with the amplitude value measured at step S3 as the base; detecting the echo moment through the threshold 1 and the threshold 2 and the time corresponding to the ultrasonic frequency; and correcting the fixed error in the echo detection moment, and improving the measurement accuracy by using a dynamic dual-threshold echo detection algorithm according to the transmission characteristic of the ultrasonic wave in the river.
Description
Technical Field
The invention relates to the field of echo detection, in particular to a dynamic dual-threshold echo detection method.
Background
The peak value detection method, namely the level comparison method, mainly comprises the steps of setting a sampling window, finding out the time when the peak value of the echo appears in the sampling window, and considering the time as the time when the ultrasonic wave reaches a receiving transducer. In practical measurement, the ultrasonic echo can reach a stable state after 7 driving pulses are transmitted. Due to the characteristics of ultrasonic waves, the time when the echo peak value is generated is different from theoretical analysis to a certain extent, and the time point when the echo peak value appears fluctuates to a certain extent. The threshold detection method comprises two threshold comparisons, a low threshold and a high threshold. The first time of the overhigh threshold value is used as the first time point t of system acquisition 1 Then two points t of the next over-threshold value are collected 2 And t 5 And too low a threshold valueTwo points t of 3 And t 4 A total of 5 points of time were acquired. By comparing the data with the predicted pulse repetition frequency, the time when the ultrasonic wave reaches the receiving transducer is judged by judging whether the ultrasonic wave is distorted due to interference. The dual-threshold detection method is more accurate in measurement in an environment where the amplitude of the ultrasonic echo is relatively stable, but in the actual use process, fluctuation of the amplitude of the ultrasonic echo is caused due to sand content and external interference, and therefore the accuracy of measurement is affected.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a dynamic double-threshold echo detection method which is mainly used for detecting echo signals in flow velocity measurement by a time difference method. According to the characteristic that ultrasonic waves are transmitted in a river, the dynamic dual-threshold echo detection algorithm improves the accuracy of measurement.
The purpose of the invention is realized by the following technical scheme:
a method for dynamic dual threshold echo detection, the method comprising the steps of:
s1: emitting 7-10 excitation signals as a first group of excitation signals, and enabling the ultrasonic signals to start oscillation to be in a stable state;
s2: the interval time T is used for emitting 7-10 excitation signals as a second group of excitation signals again;
s3: acquiring echo signals corresponding to the first group of excitation signals, and measuring an amplitude value Vpp of a current echo;
s4: setting the thresholds of the dual threshold as 50% vpp and 87.5% vpp as threshold 1 and threshold 2, respectively, with the amplitude value measured at step S3 as the base; 50% is just in the middle of the sine wave; because environmental noise exists in the actual environment, the second threshold value is set to be more than 75%,87,5% and 90%, and the probability of error is minimum when the second threshold value is set to be 87.5% after the analysis and comparison of multiple groups of data. When other threshold values are measured for multiple times, the judgment of the time possibly has an error of one period.
S5: detecting the echo moment through a threshold value 1, a threshold value 2 and the time corresponding to the ultrasonic frequency; the measurement of the propagation time of the ultrasonic waves in water is realized, and the measurement is finally converted into the detection of the algorithm on the ultrasonic wave receiving moment. The echo detection time is the time for starting ultrasonic wave emission until the ultrasonic wave is detected to be finished, namely the time for detecting the arrival of the echo.
S6: and correcting the fixed error in the echo detection time.
Further, the interval time T is 5-20 milliseconds.
Further, when the time difference count between the echo point of the threshold 1 and the echo point of the threshold 2 satisfies within 1/4 of the period, the time is determined as the echo arrival time.
Furthermore, the fixed error correction processing means that the starting time of the ultrasonic timing is the first starting point of a plurality of groups of pulse waves, and the starting point of the first waveform of the echo waveform should be theoretically the starting point of the first waveform of the echo waveform when detecting the echo, but in an actual working engineering, the starting point of the first waveform of the echo submerges in early noise and cannot be detected, a fixed time error exists here, and the echo time should be actually detected as the second echo to be corrected, that is, a fixed time error value is obtained through a real environment test, and the measurement result is corrected.
The invention has the beneficial effects that: according to the invention, the measurement accuracy is improved by using a dynamic dual-threshold echo detection algorithm according to the transmission characteristic of ultrasonic waves in a river.
Drawings
FIG. 1 is a simulation diagram of a dynamic dual-threshold echo detection method;
fig. 2 is a schematic diagram of the ultrasonic oscillation starting process.
Detailed Description
The technical solution of the present invention is further described in detail with reference to the following specific examples, but the scope of the present invention is not limited to the following.
A method for dynamic dual threshold echo detection, the method comprising the steps of:
s1: emitting 7-10 excitation signals as a first group of excitation signals, and enabling the ultrasonic signals to start oscillation to be in a stable state;
s2: the interval time T is used for emitting 7-10 excitation signals as a second group of excitation signals again;
s3: acquiring echo signals corresponding to the first group of excitation signals, and measuring an amplitude value Vpp of a current echo;
s4: setting the threshold of the double threshold as 50% and 87.5% by using the amplitude value measured at step S3 as the base, respectively, vpp as threshold 1 and threshold 2;
s5: detecting the echo moment through the threshold 1 and the threshold 2 and the time corresponding to the ultrasonic frequency; when the time difference count of the echo point of the threshold 1 and the echo point of the threshold 2 meets 1/4 period, judging the moment as the arrival moment of the echo;
s6: and correcting the fixed error in the echo detection time.
The fixed error correction processing means that the starting time of ultrasonic timing is the first starting point of a plurality of groups of pulse waves, and the starting point of the first waveform of the echo waveform is theoretically required to be the starting point of the first waveform of the echo waveform when the echo is detected, but in actual working engineering, the starting point of the first waveform of the echo submerges early noise and cannot be detected, a fixed time error exists here, the echo time is actually detected to be the several echoes, correction is performed, namely a fixed time error value is obtained through real environment testing, and correction processing is performed on a measurement result. For example, if the detected echo is the 3 rd echo or the 4 th echo in this embodiment, 3 or 4 echo times should be corrected correspondingly.
In some embodiments, the interval time T is 5-20 milliseconds.
The basic idea of the dynamic dual-threshold detection method is to send two groups of excitation signals in one measurement process, wherein an echo generated by first excitation is used for calibrating an amplitude value of the echo, and meanwhile, the echo is used as a threshold base number of the dual-threshold detection. The threshold was set at 87.5% and 50% of the base, respectively, as the detection of the second excitation producing an echo.
The specific detection method of the echo comprises the following steps: and respectively judging echo points meeting the double thresholds, and when the time difference counts of the threshold 1 echo point (50% base number) and the threshold 2 echo point (87.5% base number) meet within 1/4 period, judging the moment as the arrival moment of the echo. The collected echo signals are subjected to algorithm simulation, and the simulation result is shown in fig. 1.
The basic idea of the dynamic dual-threshold detection method is to send two groups of excitation signals in one measurement process, wherein an echo generated by first excitation is used for calibrating an amplitude value of the echo, and meanwhile, the echo is used as a threshold base number of the dual-threshold detection. The threshold was set to 87.5% and 50% of the base, respectively, as the detection of the echo generated by the second excitation. The method comprises the following specific steps:
1. the ultrasonic wave is a mechanical wave, and a longer process is needed for the start of oscillation to a stable state according to mechanical inertia, and a schematic diagram of the start of oscillation process of the ultrasonic wave is shown in fig. 2. Therefore, 7 to 10 excitation signals are emitted, and the ultrasonic signals are vibrated to a stable state;
2. emitting 7 to 10 excitation signals again at the interval of 10 ms;
3. acquiring echo signals corresponding to the first group of excitation signals, and measuring an amplitude value Vpp of a current echo;
4. the amplitude of the echo does not change greatly in a short time, and the amplitude value measured in the step 3 is taken as a base number to set the threshold of the double threshold values to be 87.5% Vpp and 50% Vpp respectively;
5. detecting the echo moment through a double-threshold and the time corresponding to the ultrasonic frequency;
6. and correcting the fixed error in the echo detection time.
The foregoing is illustrative of the preferred embodiments of this invention, and it is to be understood that the invention is not limited to the precise form disclosed herein and that various other combinations, modifications, and environments may be resorted to, falling within the scope of the concept as disclosed herein, either as described above or as apparent to those skilled in the relevant art. And that modifications and variations may be effected by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (4)
1. A method for dynamic dual threshold echo detection, the method comprising the steps of:
s1: transmitting 7-10 excitation signals as a first group of excitation signals to enable the ultrasonic signals to start oscillation to be in a stable state;
s2: 7-10 excitation signals are transmitted again at the interval T to serve as a second group of excitation signals;
s3: acquiring echo signals corresponding to the first group of excitation signals, and measuring an amplitude value Vpp of a current echo;
s4: setting the thresholds of the dual threshold with the amplitude value measured at S3 as a base to 50% Vpp and 87.5% Vpp as threshold 1 and threshold 2, respectively;
s5: detecting the echo moment through a threshold value 1, a threshold value 2 and the time corresponding to the ultrasonic frequency;
s6: correcting fixed errors in echo detection moments;
the fixed error correcting processing means that the starting time of ultrasonic timing is the first starting point of a plurality of groups of pulse waves, and the starting point of the first waveform of the echo waveform should be theoretically detected when the echo is detected, but in actual working engineering, the starting point of the first waveform of the echo is submerged in noise and cannot be detected, a fixed time error exists, the echo is corrected according to the actual detected echo time, namely, a fixed time error value is obtained through real environment testing, and the measured result is corrected.
2. The method of claim 1, wherein the echo detection time is a time when an ultrasonic wave is transmitted until an end of the ultrasonic wave is detected, i.e. a time when an echo is detected.
3. The method of claim 1, wherein the interval time T is 5-20 ms.
4. A method as claimed in claim 3, wherein the time difference between the threshold 1 echo point and the threshold 2 echo point is determined as the arrival time of the echo when the time difference count is within 1/4 of the period.
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| US3750171A (en) * | 1970-09-24 | 1973-07-31 | Bendix Corp | Diplexed multi-frequency cw doppler radar |
| US4031364A (en) * | 1975-11-10 | 1977-06-21 | Hughes Aircraft Company | Multiple moment video detector |
| US5960097A (en) * | 1997-01-21 | 1999-09-28 | Raytheon Company | Background adaptive target detection and tracking with multiple observation and processing stages |
| US6522396B1 (en) * | 2002-01-08 | 2003-02-18 | Raytheon Company | Dual mode adaptive threshold architecture for 3-D ladar FPA |
| DE102008040219A1 (en) * | 2008-07-07 | 2010-01-14 | Robert Bosch Gmbh | Method for the dynamic determination of the noise level |
| CN101516130B (en) * | 2009-03-09 | 2010-10-13 | 深圳市虹远通信有限责任公司 | WLAN trunk amplifier uplink and downlink signals switching method |
| CN102455423B (en) * | 2011-05-31 | 2013-04-17 | 吉林大学 | Method for eliminating sound reflection interference in ultrasonic location |
| CN102360070B (en) * | 2011-06-10 | 2013-04-03 | 中国科学技术大学 | Receiving apparatus for ultra wideband impulse signal and ultra wideband impulse radar system |
| CN104267413B (en) * | 2014-08-29 | 2016-10-19 | 北京空间飞行器总体设计部 | Lifting Wavelet dual threshold Denoising Algorithm based on signal intensity self adaptation TABU search |
| CN105116378B (en) * | 2015-09-30 | 2018-11-30 | 长沙开山斧智能科技有限公司 | A kind of wireless, the compound positioning system of ultrasonic wave and its localization method |
| CN107261344B (en) * | 2017-06-29 | 2019-10-08 | 哈尔滨医科大学 | A kind of ultrasonic adapted local cosine transform method for sound dynamic therapy |
| CN207691851U (en) * | 2017-12-12 | 2018-08-03 | 成都宝通天宇电子科技有限公司 | ASK amplitude adaptive noise cancellation (anc) sound demodulating equipments |
| GB2572215A (en) * | 2018-03-23 | 2019-09-25 | Short Brothers Ltd | Detection of kiss bonds within composite components |
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