CN107064941B - Ultrasonic distance measurement method based on three-stage pulse excitation and feature extraction - Google Patents

Ultrasonic distance measurement method based on three-stage pulse excitation and feature extraction Download PDF

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CN107064941B
CN107064941B CN201710296991.6A CN201710296991A CN107064941B CN 107064941 B CN107064941 B CN 107064941B CN 201710296991 A CN201710296991 A CN 201710296991A CN 107064941 B CN107064941 B CN 107064941B
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ultrasonic
excitation
distance
envelope
sampling
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CN107064941A (en
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王选择
赵治俊
董正琼
杨练根
翟中生
周向东
邬文俊
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Wuhan Puchuang Data Technology Co ltd
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Hubei University of Technology
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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
    • G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
    • G01S15/02—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems using reflection of acoustic waves
    • G01S15/06—Systems determining the position data of a target
    • G01S15/08—Systems for measuring distance only
    • G01S15/10—Systems for measuring distance only using transmission of interrupted, pulse-modulated waves
    • G01S15/102—Systems for measuring distance only using transmission of interrupted, pulse-modulated waves using transmission of pulses having some particular characteristics
    • 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
    • G01S7/523—Details of pulse systems
    • G01S7/524—Transmitters
    • 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
    • G01S7/523—Details of pulse systems
    • G01S7/526—Receivers
    • G01S7/53—Means for transforming coordinates or for evaluating data, e.g. using computers

Abstract

The invention relates to an ultrasonic distance measurement method of three-segment pulse excitation and feature extraction, which comprises the following steps of firstly, carrying out three-segment pulse alternate excitation on an ultrasonic transmitter, and synchronously acquiring ultrasonic receiving signals within a certain time at high speed by utilizing 12-bit A/D; then, envelope extraction is carried out on the ultrasonic receiving and collecting signal, and an envelope curve of the signal is extracted through sine fitting; secondly, on the basis of smoothing the envelope curve, finding out the maximum envelope peak, namely the position of the middle envelope peak through global search; searching for a transition valley point by a method of searching for a minimum value forwards in a local interval by taking the maximum envelope peak as a starting point; and finally, calculating the measured distance according to the calibration relation between the position of the transition valley point and the measured distance. The invention overcomes the problem of slow oscillation attenuation under unidirectional pulse excitation, and adopts a three-section type forward and reverse alternate excitation mode, namely an excitation mode of forward, reverse and forward, so as to ensure that the ultrasonic receiver is in a non-oscillation state before the next measurement.

Description

Ultrasonic distance measurement method based on three-stage pulse excitation and feature extraction
Technical Field
The invention belongs to the technical field of ultrasonic ranging, and particularly relates to an ultrasonic ranging method based on three-section type pulse excitation and feature extraction.
Background
Ultrasonic ranging, as an active non-contact measurement technology, has a series of characteristics of concentrated direction, strong penetrating power, slow energy attenuation and the like, and is widely applied to the fields of modern industrial measurement and control, such as distance measurement, liquid level measurement, ultrasonic flaw detection, automatic parking systems and reversing radar systems. At present, the methods for ultrasonic ranging at home and abroad are mainly classified into a multi-frequency ranging method, a phase difference detection method, a flight time detection method and the like. Of the three measurement methods, the time-of-flight detection method is most widely used because of its simple operation and easy implementation. The method for detecting the flight time achieves distance measurement through the direct proportion relation between the propagation distance of sound waves in a medium and the flight time, for a split correlation type ultrasonic distance measurement system, the distance l is c t, c represents the sound velocity in the current environment, and t is the transit time of ultrasonic waves from a transmitting end to the middle of a receiving end, namely the flight time.
In the traditional flight time detection method, an ultrasonic transmitter sends a certain number of pulse excitation waves at a time, due to energy superposition, an ultrasonic wave received by an ultrasonic transducer is a sine modulation signal with slow fluctuation envelope, and the flight time method distance measurement is realized by detecting the oscillation starting time point or the envelope peak point of the ultrasonic received wave. However, the ultrasonic envelope curve obtained by the traditional ultrasonic excitation method only has one-time envelope wave peak value, and when the change of the peak position of the ultrasonic receiving signal is smooth or tends to be saturated, the peak value point of the envelope curve does not have unique certainty, so that a large error occurs, and the final measurement precision is influenced.
Disclosure of Invention
In order to solve the technical problems, the invention provides a three-section type positive and negative alternative ultrasonic emission probe excitation method and an ultrasonic receiving signal envelope characteristic valley point position extraction method on the basis of a traditional flight time detection method, and the method can realize accurate distance measurement in ultrasonic distance measurement.
The invention mainly adopts the following technical scheme:
an ultrasonic distance measuring system with three-section type pulse excitation and feature extraction is characterized by comprising: TCT40-16R/T type split ultrasonic sensor with the center frequency of 40 kHz; ultrasonic transmitter and receiver are installed on linear guide with the components of a whole that can function independently correlation formula, and the transmitter bottom mounting is in the linear guide bottom, and the receiver removes in 0 ~ 500 mm's within range.
An ultrasonic distance measurement method based on three-section type pulse excitation and feature extraction is characterized by comprising the following steps:
step 1: in the measuring range of the ultrasonic distance measuring system, a group of distance groups L to be measured is selected optionally1,l2,…,lnAt each distance, firstly sending n by using a PWM module of an STM32 singlechip1A pulse with a period of T, delaying T/2, and transmitting n2A pulse with a period of T is delayed by T/2, and finally n is sent3The pulses with the period of T are amplified by the excitation driving circuit and are sequentially loaded to the transmitting end of the ultrasonic transmitter according to the transmitting sequence, the ultrasonic transmitter transmits ultrasonic signals, and the ultrasonic receivers in the same linear direction receive the ultrasonic signals and then convert the ultrasonic signals into electric signals; wherein n is transmitted for the third time3The purpose of each excitation pulse is to cancel the oscillation energy of the previous time, so that the ultrasonic transmitter is in a non-oscillation state when the next excitation period comes, and the influence on the next excitation period is avoided; the number n of pulses selected here1、n2、n3Can ensure that the maximum peak of the envelope appears on the second peak and the most basic relation n between the maximum peak and the second peak is satisfied2>n1、n2>n3；
Step 2: when an excitation signal is sent out, synchronous 12-bit high-speed A/D collection is carried out on the excitation signal and an ultrasonic receiving signal by using an STM32 singlechip and taking delta t as a sampling time interval, the number of sampling points at each time is N, and envelope curve extraction is carried out on the ultrasonic signal sampled at each time to obtain envelope sequence points;
and step 3: smoothing the envelope sequence points by taking every n points as the length, searching the maximum peak point appearing on the smoothed envelope curve, and marking the sampling sequence position x corresponding to the maximum peak point0With x0As a starting point, w is the interval length, the minimum value point of the envelope curve after smoothing is searched forwards, namely a transition valley point, and the sampling sequence position x corresponding to the transition valley point is markedp；
And 4, step 4: in the distance group L ═ L to be measured1,l2,…,lnCalculating corresponding x under the conditionp＝{xp1,xp2,…,xpn}，
The sampling time interval is fixed, so that the flight time of the ultrasonic wave and the sampling sequence position are in a direct proportion relation, and the linear relation of the distance and the flight time is combined to know that the measured distance l and the sampling sequence position x of the transition valley pointpThere is also a linear relationship between; thus, in xpIs independent variable and l is dependent variable, and l and x are fitted by adopting least square method principlepIs the mathematical relational expression of (l ═ ax)p+b；
And 5: for any distance l to be measured, the sampling sequence position x of the transition valley point is calculated by applying the steps 1, 2 and 3pThen x is addedpAnd (4) substituting the distance l into the mathematical expression fitted in the step 4 to obtain the distance l to be measured.
In the above ultrasonic distance measuring method with three-stage pulse excitation and feature extraction, in step 3, n is equal to the number of sampling points in one signal period.
The invention uses the alternate excitation of forward and reverse pulses to make the ultrasonic transmitter generate an oscillation signal which is attenuated and then enhanced to form a transition valley point representing the change of the oscillation direction. Based on the time-of-flight detection principle, the position of the transition valley point is linearly related to the detection distance. Considering that the valley point feature is significant, the detection error for this point position is small. Meanwhile, in order to overcome the problem of slow oscillation attenuation under unidirectional pulse excitation, a three-section type forward and reverse alternate excitation mode, namely an excitation mode of forward, reverse and forward is adopted, so that the ultrasonic receiver is ensured to be in a non-oscillation state before the next measurement.
Drawings
FIG. 1 is a schematic diagram of an ultrasonic ranging system in an embodiment of the invention.
FIG. 2 is a block diagram of a system in an example of the invention.
Figure 3 is a signal diagram of a sample of an improved excitation pulse in an example of the invention.
FIG. 4 improved excitation of an embodiment of the inventionUltrasonic receiving signal sampling diagram, envelope curve diagram and independent variable x under modepSchematic representation of (a).
FIG. 5 shows a set of distances l and an independent variable x according to an embodiment of the present inventionpLeast squares linear fit results of (a).
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the following describes in detail the improved excitation method and the processing of the ultrasonic receiving signal with reference to the accompanying drawings and exemplary embodiments, which are described herein only for explaining the present invention and are not intended to limit the scope of the present invention.
The invention provides an improved ultrasonic ranging excitation mode and a data processing method thereof, comprising the following steps:
step 1: the ultrasonic ranging system in this example is shown in FIG. 1. the measurement system employs a TCT40-16R/T type split ultrasonic sensor with a center frequency of 40 kHz. The ultrasonic transmitter and the transducer are installed on the linear guide rail in a split correlation mode, the bottom end of the transmitter is fixed to the bottom end of the linear guide rail, the receiver can move within the range of 0-500 mm, the measuring system is placed in an air environment with constant temperature, and a frame diagram of the measuring system in the embodiment is shown in fig. 2. In the embodiment, a distance group L is selected to be {0,50,100, …,450,500} mm at a distance of 50mm for calibration, under each distance condition, an STM32 single chip microcomputer is used for sending 3 pulses with a period of 25 mu s to the transmitter, delaying for 12.5 mu s, sending 10 pulses with a period of 25 mu s, delaying for 12.5 mu s and sending 6 pulses with a period of 25 mu s, as shown in fig. 3, the pulses are amplified by an excitation driving circuit and then sequentially loaded to the transmitting end of an ultrasonic transmitter according to the sending sequence, the ultrasonic transmitter then sends ultrasonic signals, and ultrasonic receivers in the same straight line direction receive the ultrasonic signals and then convert the ultrasonic signals into electric signals;
step 2: synchronous 12-bit A/D acquisition is carried out on the excitation signal and the ultrasonic receiving signal by using an STM32 singlechip and taking 1.17 mu s as a sampling interval, and 2000 points are sampled each time. Extracting an envelope curve of the ultrasonic signal sampled every time to obtain envelope sequence points, as shown in fig. 4. In this example, an envelope curve extraction method based on moving sine fitting is selected, but the invention is not limited to this method;
and step 3: smoothing the envelope sequence points by taking every 21 points as length, searching the smoothed maximum envelope peak point, and marking the sampling sequence position group of the maximum envelope peak point
X0= 445,573,687,820,960, 1091,1345,1460,1582,1695 }. With x0As a starting point, 220 is the interval length (220 is the empirical interval length obtained from multiple experiments of the measurement system in this example), and the corresponding interval [ x [ ]0-220,x0]Searching the transition valley point of the envelope curve which can be smoothed inwards and forwards, and marking the sampling sequence position group corresponding to the transition valley point
Xp＝{284,414,532,666,791,919,1045,1177,1301,1424,1543}；
And 4, step 4: the sampling sequence position group X corresponding to the transition valley point by the above-mentioned calibration distance group LpFitting l and x by least square method for sample datapIs expressed as
l＝0.395xp112.664 (unit: mm), the straight line fitting results of the two sets of data are shown in FIG. 5;
and 5: in this example, after the ultrasonic receiver is placed at an arbitrary position, the method of the above steps 1, 2, and 3 is used to extract the envelope sequence points, and calculate the sequence x corresponding to the minimum value of the envelope curve in the above intervalp853, which is substituted into l and x fitted in step 5pIn the mathematical expression of (a), it can be calculated that the currently measured distance is l 224.271 mm.
The specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications or additions may be made to the described embodiments or alternatives may be employed by those skilled in the art without departing from the spirit or ambit of the invention as defined in the appended claims.

Claims (2)

1. The ultrasonic distance measurement method based on three-section type pulse excitation and feature extraction is characterized in that an ultrasonic distance measurement system based on three-section type pulse excitation and feature extraction comprises the following steps: TCT40-16R/T type split ultrasonic sensor with the center frequency of 40 kHz; the ultrasonic transmitter and the receiver are installed on the linear guide rail in a split correlation mode, the bottom end of the transmitter is fixed at the bottom end of the linear guide rail, and the receiver moves within the range of 0-500 mm;
the distance measurement method comprises the following steps:
step 1: in the measuring range of the ultrasonic distance measuring system, a group of distance groups L to be measured is selected optionally1,l2,…,lnAt each distance, firstly sending n by using a PWM module of an STM32 singlechip1A pulse with a period of T, delaying T/2, and transmitting n2A pulse with a period of T is delayed by T/2, and finally n is sent3The pulses with the period of T are amplified by the excitation driving circuit and are sequentially loaded to the transmitting end of the ultrasonic transmitter according to the transmitting sequence, the ultrasonic transmitter transmits ultrasonic signals, and the ultrasonic receivers in the same linear direction receive the ultrasonic signals and then convert the ultrasonic signals into electric signals; wherein n is transmitted for the third time3The purpose of each excitation pulse is to cancel the oscillation energy of the previous time, so that the ultrasonic transmitter is in a non-oscillation state when the next excitation period comes, and the influence on the next excitation period is avoided; the number n of pulses selected here1、n2、n3Can ensure that the maximum peak of the envelope appears on the second peak and the most basic relation n between the maximum peak and the second peak is satisfied2>n1、n2>n3；
Step 2: when an excitation signal is sent out, synchronous 12-bit high-speed A/D collection is carried out on the excitation signal and an ultrasonic receiving signal by using an STM32 singlechip and taking delta t as a sampling time interval, the number of sampling points at each time is N, and envelope curve extraction is carried out on the ultrasonic signal sampled at each time to obtain envelope sequence points;
and step 3: smoothing the envelope sequence points by taking every n points as the length, searching the maximum peak point appearing on the smoothed envelope curve, and marking the sampling sequence position x corresponding to the maximum peak point0With x0As a starting pointW is the minimum value point of the envelope curve after the interval length is searched forward and smoothed, namely a transition valley point, and the sampling sequence position x corresponding to the transition valley point is markedp；
And 4, step 4: in the distance group L ═ L to be measured1,l2,…,lnCalculating corresponding x under the conditionp＝{xp1,xp2,…,xpn}，
The sampling time interval is fixed, so that the flight time of the ultrasonic wave and the sampling sequence position are in a direct proportion relation, and the linear relation of the distance and the flight time is combined to know that the measured distance l and the sampling sequence position x of the transition valley pointpThere is also a linear relationship between; thus, in xpIs independent variable and l is dependent variable, and l and x are fitted by adopting least square method principlepIs the mathematical relational expression of (l ═ ax)p+b；
And 5: for any distance l to be measured, the sampling sequence position x of the transition valley point is calculated by applying the steps 1, 2 and 3pThen x is addedpAnd (4) substituting the distance l into the mathematical expression fitted in the step 4 to obtain the distance l to be measured.
2. The ultrasonic ranging method with three-stage pulse excitation and feature extraction as claimed in claim 1, wherein in the step 3, n is equal to the number of sampling points in one signal period.
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CN108519592B (en) * 2018-04-24 2021-09-03 湖北工业大学 Ultrasonic ranging excitation signal adjusting system and method for reducing blind area
CN110045379B (en) * 2019-04-11 2023-03-31 花瓣云科技有限公司 Distance measuring method, related equipment and system
CN110108797B (en) * 2019-04-30 2021-07-30 天津大学 Medium interface ultrasonic detection method utilizing acoustic impedance change information
CN111442747B (en) * 2020-03-13 2021-11-30 中核武汉核电运行技术股份有限公司 Ultrasonic signal processing method
CN112444800A (en) * 2020-10-19 2021-03-05 中科传启（苏州）科技有限公司 Correction method of ultrasonic distance measuring device
CN116170087B (en) * 2022-12-29 2023-11-10 深圳大学 Microsecond ultra-short pulse underwater sound signal detection method
CN116878599B (en) * 2023-09-06 2024-01-09 青岛鼎信通讯科技有限公司 Flow metering method of ultrasonic water meter

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