CN107064995A - A kind of acoustics method for positioning underground pipeline based on DSP - Google Patents

Abstract

The invention discloses a kind of acoustics method for positioning underground pipeline based on DSP, belong to the technical field of industrial automation and test and measurement.Based on the principle of acoustic localization technique in the PE pipeline detections of underground, D/A module and A/D module using DSP F28335 development boards have designed and Implemented a set of acoustics positioning testing system as main control chip.By the use of Complementary Golay sequences as transmitting sequence, the receiving terminal echo acoustical signal faint to collecting is handled in real time, and the position of target point just can be calculated according to echo time delay.The method of the present invention can be accurately positioned the position of underground utilities, while further exploitation is laid a good foundation for underground PE pipeline locations instrument.

Description

A DSP-Based Acoustic Underground Pipeline Location Method

technical field

The invention relates to the technical fields of industrial automation and testing and measurement, and specifically refers to a DSP-based acoustic underground pipeline positioning method.

Background technique

Underground pipelines are an important part and infrastructure of a city, providing protection for people's normal production and life at all times. Today, with the continuous development of urban modernization, the number and types of underground pipelines are constantly increasing. PE pipe has the advantages of convenient construction, corrosion resistance and impact resistance, so it is more and more widely used in pipeline engineering, but its non-conductivity and non-magnetic conduction make positioning difficult, which increases the possibility of third-party construction damage to the pipeline. According to reports and statistics, in the first half of 2013, there were 11 third-party sabotage accidents of gas pipelines in Shenzhen, causing economic losses of nearly 1 million yuan. There are many other reports of pipelines being damaged during construction. The leakage of the pipeline not only threatens the lives of the people, but also causes losses to the property of the construction party, and also pollutes the living environment of the people. Therefore, the research on the accurate positioning of underground PE pipes is of great significance.

At present, the application of acoustic positioning technology to the positioning and detection of buried pipelines is a new technology. This technology mainly uses the propagation characteristics of sound waves in the medium to detect and locate targets. The principle of acoustic positioning technology is as follows:

Generally, the sound pressure wave can be expressed as the relationship between time and position, see formula (1):

In the formula: p—sound pressure, P _a

x—the location of the sound wave emission point, m

ρ ₀ —medium average density, kg/m ³

μ—compression factor

t—time, s

Generally, the expression form of sound pressure p is a continuous plane wave, which can be decomposed into the form of formula (2):

p(x,t)=P _α cos(2πft+kd) (2)

where P _α —plane wave amplitude, m

f—frequency, _Hz

k—wave number

d—the propagation distance of the wave, m

c—propagation speed of sound wave, m/s

When performing pipeline acoustic positioning detection, the transmitter transmits a beam of short acoustic pulses to the ground, and the echo waves are reflected from any interface that is discontinuous or has a mismatched acoustic impedance, and the receiver receives the ground surface waves and pipeline reflection waves. In general, increasing the frequency of the sound wave can improve its ability to identify small pipes and nearby pipes, but as the frequency increases, the attenuation ability of the soil also increases. For pipelines with different buried depths, the maximum operating frequency should be set based on soil attenuation characteristics. According to different soil types, humidity and compaction conditions, the attenuation value ranges from 0.1 to 0.9d B/(k Hz cm), and the attenuation coefficient depends on on ground conditions.

Contents of the invention

Aiming at the deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide a DSP-based acoustic underground pipeline positioning method to solve the existing high demand for pipeline positioning in urban development, but the current large-scale use of PE pipelines is difficult to locate. A pair of contradictory questions.

In order to achieve the above object, a DSP-based acoustic underground pipeline positioning method of the present invention comprises steps as follows:

The DA module generates a signal, which is amplified by the power amplifier and sent out by the transmitting sound sensor; the receiving end uses the receiving sound sensor to receive the echo signal, and before the AD module processes the received echo signal, the bipolar echo signal is converted by the operational amplifier The wave signal is converted to the range of 0-3V, and the sampling rate of the DA module and AD module is set to be the same; the high-speed floating point operation in the DSP development board is used to process the collected echo signal data in real time, and the upper layer is controlled by CCS software Both work synchronously;

To detect the soil sound velocity, assuming that the distance between the two probes of the receiving and transmitting sound sensors is s, and ΔN is the number of points of the echo peak time delay when the distance s is compared to the time when the two probes are short-circuited s=0, the calculation formula of the sound velocity is :

According to the above-mentioned soil sound velocity, the delay parameter is obtained to obtain the pipeline position; in the actual pipeline positioning process, there will be primary echo and secondary echo, the primary echo is the soil surface wave, and the secondary echo is the reflected echo of the target point; through Read the time delay points N of the secondary echo relative to the primary echo to calculate the position of the target point:

Among them, x is the distance of the target point to be obtained, fs is the sampling rate of AD/DA module of the main control system, is the soil sound velocity after several measurements.

Preferably, the DA module generates 64-bit Gray a and b sequences, which are modulated by a root-raised cosine filter with a roll-off coefficient of 1 and sent out alternately.

Preferably, the AD module uses a root-raised cosine filter to filter the signal, so that the signal-to-noise ratio is the highest at the sampling moment, and can not introduce intersymbol interference in a certain band-limited flat channel; then use the inverted a, b The sequence performs matched filtering on the echo signal respectively, and then adds the two results together to cancel out the noise side lobes to obtain the echo correlation peak.

Beneficial effects of the present invention:

1. Use the DA/AD module of TI's F28335 development board as the main control chip. The DA module realizes signal generation, and the AD module performs data collection. The high-speed floating-point operation enables real-time processing of the collected echo data; the software controls the synchronization of the two The work ensures the real-time and validity of the data collected by the system.

2. According to the different echo delays caused by the different spacing distances of the two probes, the acoustic velocity in the soil can be accurately calculated, which provides the necessary foundation for subsequent pipeline positioning.

3. According to the sound velocity of the soil, the specific location of the underground pipeline can be accurately located; it has the advantages of high precision, good real-time performance, and flexible operation.

Description of drawings

Fig. 1 is a schematic diagram of the system structure of the present invention.

Fig. 2a is a schematic diagram of the simulation of the transmitted signal a.

Fig. 2b is a schematic diagram of the simulation of the transmitted signal b.

FIG. 3 is a schematic diagram of a simulated echo waveform after matching.

Figure 4 is a schematic diagram of the principle of soil sound velocity measurement.

Figure 5 is a schematic diagram of the echo when the soil sound velocity is measured at 60cm.

Figure 6 is a schematic diagram of the echoes of the pipeline positioning results.

detailed description

In order to facilitate the understanding of those skilled in the art, the present invention will be further described below in conjunction with the embodiments and accompanying drawings, and the contents mentioned in the embodiments are not intended to limit the present invention.

A kind of acoustic underground pipeline location method based on DSP of the present invention comprises as follows:

Based on the system structure shown in Figure 1, the TMS320F28335 development board of TI Company is selected, the upper layer application software is CCS6.0, and the emulator uses XDS100v3, 12.6V regulated power supply for power supply. The DA module is used as a signal generator to periodically send signals, which are amplified by the power amplifier and sent out through the transmitting sound sensor; the receiving end uses the AD module for data collection, because the analog input range of the AD module is 0-3V to ensure the safety of the AD chip Therefore, it is necessary to place an operational amplifier with a certain multiple in front of the AD module to raise the bipolar echo signal to positive polarity. The AD module samples, holds, quantizes, and encodes the received echo signal data, converts the analog quantity into a digital quantity, and stores it in the corresponding result register in sequence. Among them, the trigger mode of A/D conversion is software trigger, an interrupt is triggered at the end of each conversion, the sampling mode is sequential sampling by single sequencer, ADCIA0 is selected as the input channel, and ADCRESULT0 is selected as the result register. Among them, the sampling rate of DA module and AD module is set to be the same; the high-speed floating-point operation in the DSP development board enables real-time processing of the collected echo data, and the upper layer controls the synchronous work of the two through the CCS software; ensuring the data collected by the system timeliness and effectiveness.

Gray complementary sequences have good time-domain composition characteristics and frequency-domain complementary characteristics, and can be used as a detection signal for an acoustic positioning system with good performance after proper signal transformation. The raised cosine signal can effectively overcome inter-symbol interference because of its "tailing" sidelobe attenuation is fast. The transmitting end modulates the 64-bit Gray a and b sequences through a root-raised cosine filter with a roll-off coefficient of 1 and transmits them alternately, as shown in Figure 2.

The receiving end uses the same root raised cosine filter as the transmitting end to filter it, which can not only make the signal-to-noise ratio the highest at the sampling time, but also avoid introducing intersymbol interference in a certain band-limited flat channel. Then use the inverted a and b sequences to match and filter the echo signal respectively, and then add the two results together to cancel out the noise side lobes and obtain the echo correlation peak with good performance, as shown in Figure 3.

Before positioning the underground pipeline, first measure and calculate the sound velocity in the soil, as shown in Figure 3, assuming that the distance between the two probes of the receiving and transmitting sound sensors is s, and when ΔN is the distance s, the two probes are shorted (s = 0), the calculation formula of sound velocity is:

Different distances s correspond to different delay points ΔN, and the soil sound velocity c here can be calculated by taking the average value of multiple measurements.

According to the above-mentioned soil sound velocity, the delay parameter is obtained to obtain the pipeline position; in the actual pipeline positioning process, there will be primary echo and secondary echo, the primary echo is the soil surface wave, and the secondary echo is the reflected echo of the target point; Calculate the position of the target point by reading the time delay points N of the secondary echo relative to the primary echo:

Among them, x is the distance of the target point to be obtained, fs is the sampling rate of AD/DA module of the main control system, is the soil sound velocity after several measurements. In order to improve the accuracy of the system, move the two probes back and forth appropriately to find a position perpendicular to the underground pipeline so that the peak value of the echo reaches the highest.

Specifically, the computer control software uses CCS6.0, the DSP is the F28335 development board of TI's TMS320Fx series, and the emulator uses xds100v3. Powered by 12.6V regulated power supply, the signal transmitting and receiving probes are both 50MM resonant sound sensors, and the frequency characteristic range is 0-500Hz.

The software sets the sampling rate of the AD/DA module to 10KHz to ensure the synchronization of signal sending and receiving. The DA module adopts N=64-bit complementary Gray sequence, passes through a raised cosine filter with a roll-off coefficient of 0.1, sampling rate fs=10KHz, signal frequency f=500Hz, and sends a signal every T=1s, wherein, the signal duration T _s =128 ms.

Before locating underground pipelines, the sound velocity in the soil must be measured and calculated. Figure 4 shows a schematic diagram of the soil sound velocity measurement principle. Assuming that the distance between the two probes of the receiving and transmitting sound sensors is s, ΔN is the number of points of the echo peak time delay when the two probes are short-circuited (s=0) at a distance of s.

Figure 5 shows that when s=60cm, the peak point position is at N=46 at this time, so according to formula (3), the sound velocity can be calculated as 194m/s. Table 1 shows the number of time delay points ΔN corresponding to different distances s. According to the above sound velocity calculation formula, the soil sound velocity c=192m/s can be calculated by taking the average value of multiple measurements.

Table 1

S(cm) ΔN c(m/s) 0 0 10 5 200 20 11 182 30 16 188 40 20 200 50 26 192 60 31 194 70 37 189 80 42 190 90 47 191 100 54 186

The transmitting sound sensor and the receiving sound sensor are separated by an appropriate distance to reduce mutual interference when the two work at the same time. Figure 6 is a schematic diagram of the echoes of the pipeline positioning results. The two echoes in the figure are the primary echo and the secondary echo respectively, read the time delay point N of the secondary echo relative to the peak value of the primary echo, according to the formula:

The distance of underground pipelines can be calculated. In order to improve the accuracy of the system, move the two probes back and forth appropriately to find a position perpendicular to the underground pipeline so that the peak value of the echo reaches the highest. After multiple measurements, Figure 6 is a schematic diagram of the echoes of the pipeline positioning results. The two echoes are the primary echo and the secondary echo, the primary echo is a surface wave, and there is a fixed delay N ₀ =14, and the secondary echo is the target point Reflected echo, the time delay of the peak point of the second echo is N=86, so the relative time delay relative to the first echo is ΔN=NN ₀ =72, therefore, the vertical distance of the buried pipeline here is calculated according to formula (5) x=1.38m.

There are many specific application approaches of the present invention, and the above description is only a preferred embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art, some improvements can also be made without departing from the principles of the present invention. Improvements should also be regarded as the protection scope of the present invention.

Claims (3)

1. a DSP-based acoustic underground pipeline location method, is characterized in that, comprises steps as follows: The DA module generates a signal, which is amplified by the power amplifier and sent out by the transmitting sound sensor; the receiving end uses the receiving sound sensor to receive the echo signal, and before the AD module processes the received echo signal, the bipolar echo signal is converted by the operational amplifier The wave signal is converted to the range of 0-3V, and the sampling rate of the DA module and AD module is set to be the same; the high-speed floating point operation in the DSP development board is used to process the collected echo signal data in real time, and the upper layer is controlled by CCS software Both work synchronously; To detect the soil sound velocity, assuming that the distance between the two probes of the receiving and transmitting sound sensors is s, and ΔN is the number of points of the echo peak time delay when the distance s is compared to the time when the two probes are short-circuited s=0, the calculation formula of the sound velocity is : <mrow> <msub> <mi>c</mi> <mn>0</mn> </msub> <mo>=</mo> <mfrac> <mi>s</mi> <mrow> <mi>&amp;Delta;</mi> <mi>N</mi> <mo>&amp;CenterDot;</mo> <mn>1</mn> <mo>/</mo> <mi>f</mi> <mi>s</mi> </mrow> </mfrac> </mrow> According to the above-mentioned soil sound velocity, the delay parameter is obtained to obtain the pipeline position; in the actual pipeline positioning process, there will be primary echo and secondary echo, the primary echo is the soil surface wave, and the secondary echo is the reflected echo of the target point; Calculate the position of the target point by reading the time delay points N of the secondary echo relative to the primary echo: <mrow> <mi>x</mi> <mo>=</mo> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <mo>&amp;CenterDot;</mo> <mfrac> <mi>N</mi> <mrow> <mi>f</mi> <mi>s</mi> </mrow> </mfrac> <mo>&amp;CenterDot;</mo> <mover> <mi>c</mi> <mo>&amp;OverBar;</mo> </mover> </mrow> Among them, x is the distance of the target point to be obtained, fs is the sampling rate of AD/DA module of the main control system, is the soil sound velocity after several measurements. 2. the acoustic underground pipeline location method based on DSP according to claim 1, is characterized in that, described DA module generates 64 gray a, b sequence, after being 1 root raised cosine filter modulation by roll-off coefficient issued alternately. 3. the acoustic underground pipeline location method based on DSP according to claim 1, is characterized in that, described AD module adopts root-raised cosine filter to filter signal, makes the highest signal-to-noise ratio at sampling moment, can be in certain No intersymbol interference is introduced in the band-limited flat channel; then the echo signals are matched and filtered with the inverted a and b sequences respectively, and then the two results are added to cancel each other out the noise side lobes to obtain the echo correlation peak.