阅读说明：本技术 一种垃圾填埋场hdpe膜损伤定位系统及方法 (System and method for positioning damage of HDPE (high-density polyethylene) film in refuse landfill ) 是由 陈亚宇 马天行 王宏达 王凯 于 2021-08-19 设计创作，主要内容包括：本发明公开了一种垃圾填埋场HDPE膜损伤定位系统及装置,其是利用了超声波散射特性。借助以规则的平面几何方式铺设在HDPE膜待检测区域上表面的波压电片,由波压电片形发生器控制半数压电片自激振荡产生超声波,且较佳的,为防止检测系统相互干扰,再由指定对边压电片接收超声波信号。依据上述过程完成扫描并得到模拟量损伤信号,经模数变换与小波分析提取时间-能量密度特征,根据有无损伤时能量密度差异,结合概率成像实现损伤定位,经系统控制发出损伤警报,且能显示损伤位置。该系统能解决现有裸膜检测方法时效性低、气体泄露、人工工作量大等问题,并通过诱振压电片实现HDPE膜主动检测,有效降低漏检率。(The invention discloses a system and a device for locating damage of HDPE (high-density polyethylene) films in a refuse landfill, which utilize the ultrasonic scattering property. By means of the wave piezoelectric sheets laid on the upper surface of the HDPE film area to be detected in a regular plane geometric mode, the wave piezoelectric sheet generator controls half of the piezoelectric sheets to generate ultrasonic waves through self-oscillation, and preferably, in order to prevent mutual interference of detection systems, the piezoelectric sheets on the appointed opposite sides receive ultrasonic signals. Scanning is completed according to the process, an analog quantity damage signal is obtained, time-energy density characteristics are extracted through analog-to-digital conversion and wavelet analysis, damage positioning is achieved by combining probability imaging according to energy density difference when damage exists, damage alarm is given out through system control, and damage positions can be displayed. The system can solve the problems of low timeliness, gas leakage, large workload and the like of the existing bare membrane detection method, and can realize the active detection of the HDPE membrane through the induced vibration piezoelectric plate, thereby effectively reducing the omission factor.)

1. A refuse landfill HDPE membrane damage positioning method is characterized in that piezoelectric patches are arranged in a to-be-detected area on an HDPE membrane in a preset regular plane geometric shape, then a part of piezoelectric patches are selected to generate ultrasonic waves, the rest of piezoelectric patches are used as receivers to obtain a plurality of sensing path detection networks covering a rectangular detection area, analog quantity damage signals are obtained through scanning, ultrasonic scattering signals passing through the HDPE membrane damage position are extracted, time-energy density characteristics are extracted through analog-to-digital conversion and wavelet analysis, damage positioning is achieved through probability imaging according to the energy density difference when damage exists, data superposition is conducted on damage probability values of any position in the detection area, and the coordinate of a point with the maximum numerical value is the damage position.

2. The method of claim 1, wherein the regular planar geometry is: rectangular, parallel, circular or triangular.

3. The method as claimed in claim 2, wherein when the rectangular arrangement is adopted, the piezoelectric sheets on two adjacent sides are selected to generate ultrasonic waves, and the piezoelectric sheets on the opposite sides are selected as receivers; when the piezoelectric sheets are arranged in a parallel line mode, the upper half part of the piezoelectric sheets are controlled to sequentially generate ultrasonic waves, and the opposite side of the piezoelectric sheets are selected as ultrasonic receivers; when the piezoelectric sheets are arranged in a circular mode in the area to be detected of the HDPE film, the piezoelectric sheets sequentially generate ultrasonic waves, and the rest piezoelectric sheets are used as receivers; when the piezoelectric sheets are arranged in a triangular mode, the piezoelectric sheets are controlled to sequentially generate ultrasonic waves, and under the condition that the ultrasonic waves are not mutually influenced, the rest piezoelectric sheets are selected as receivers.

4. The refuse landfill HDPE membrane damage locating method according to any one of claims 1-3, characterized in that the calculation method of data superposition is as follows:

wavelet transforming the ultrasonic signal as a function of a scale parameter a and a time parameter b:

f (t) represents the ultrasonic signal measured by the piezoelectric sheet, psi (t) represents the wavelet basis function, psi^*(t) denotes the complex conjugate of ψ (t), WT (a, b) being a function after wavelet transform processing;

according to the equidistant characteristic of the wavelet transform, the energy conservation in the wavelet transform process of the signal f (t) can obtain:

C_ψrepresents a solubility condition, | WT (a, b) & gtY luminous²dadb/C_ψa²Representing the energy of the signal with the scale a and the time b as the origin, the scale interval da and the time interval db;

writing equation (2) as:

wherein:

e (b) is the energy value of the ultrasonic signal at the moment b, which is a time-energy density function and reflects the energy distribution condition of the signal frequency;

equation (5) represents the transformation of energy with parameter b in the interval of scale a,

e' (b) is expressed in the scale [ a ]₁,a₂]The local time-energy density function is obtained by changing the value of the scale a, so that the distribution of the ultrasonic signals along with the time is obtained;

after the HDPE film lossless and lossy signals are subjected to wavelet transform processing, the energy density difference of the ultrasonic signals is compared, and the damage index DI in a time-frequency domain is as follows:

b (t) represents an ultrasonic reference signal when the HDPE film is not damaged, and D (t) represents an ultrasonic signal in a damaged state. A larger DI value indicates that the lesion is close to the sensing path; the smaller the DI value is, the farther the damage position is from the sensing path;

and corresponding DI values on the sensing path to positions in the rectangular detection area through a weighted distribution function, wherein a spatial distribution function R (x, y) of DI is as follows:

wherein (x)_a,y_a) To excite the piezoelectric patch coordinates, (x)_t,y_t) To receive the piezoelectric patch coordinates, (x)_k,y_k) Is the coordinate of any point in the rectangular area, d_kD represents a parameter of each sensing path influenced by the size of the divided grid, and the smaller D is, the influence degree is, the distance between the sensing path and the sum of the distances from any point of the detection area to the voltage generating and emitting sheet is, and the distance between the sensing path and the sum of the distances from the detection area to the voltage generating and emitting sheet is the ratio of the distance between the detection area and the sum of the distances from any point of the detection area to the voltage generating and emitting sheet to the sensing path;

and performing data superposition on the damage probability values of the multiple sensing paths, wherein the point with the maximum superposition value is the damage position.

5. The method of claim 4, wherein the calculation method includes an enhancement factor for solving the problem of dispersion of positioning results, and the algorithm is as follows:

wherein n is the number of sensing paths participating in superposition; DI_kThe damage index of the kth sensing path is; u is an enhancement factor, and I is a damage probability value;

and (3) the coordinate (x, y) when the value I is maximum is the damage position of the HDPE film.

6. A HDPE membrane damage positioning system for a refuse landfill is characterized by mainly comprising an ultrasonic generating module and an ultrasonic receiving and processing module,

the ultrasonic wave generation module mainly comprises a plurality of piezoelectric sheets and a waveform generator; the receiving processing module mainly comprises a piezoelectric sheet, an A/D converter and a processor;

the processor scans each piezoelectric plate to obtain the received ultrasonic signal as an analog quantity damage signal, extracts time-energy density characteristics through analog-to-digital conversion and wavelet analysis, and combines probability imaging to realize damage positioning according to energy density difference when damage exists.

7. The landfill HDPE film damage localization system of claim 6, wherein the regular planar geometry is: rectangular, parallel, circular or triangular, and the piezoelectric sheets with assigned opposite sides receive ultrasonic signals to prevent mutual interference of detection systems.

8. The refuse landfill HDPE membrane damage positioning system according to claim 6, wherein the receiving processing module further comprises an upper computer, the processor stores the ultrasonic signal generated by the piezoelectric sheet on one hand, and on the other hand, after the HDPE membrane damage is detected, transmits the obtained HDPE membrane damage position information to the upper computer, so that the damage position is displayed by the upper computer.

9. The landfill HDPE membrane damage locating system according to claim 6 or 8, wherein the receiving and processing module further comprises an alarm, and when the HDPE membrane damage is detected, the alarm is controlled by the system to give a damage alarm.

Technical Field

The invention relates to the field of environmental engineering, in particular to a garbage landfill HDPE film damage positioning system utilizing ultrasonic scattering characteristics.

Background

In order to solve the problem that the leachate leaks and pollutes the underground water, the domestic garbage landfill site usually adopts the laying of an HDPE film to realize seepage prevention. However, due to various reasons such as irregular construction and welding, the HDPE film of the landfill is damaged before operation, so that the HDPE film needs to be damaged and positioned in advance before being put into use so as to be repaired in time.

At present, the traditional method for detecting HDPE bare membrane damage in the refuse landfill mainly comprises an infrared detection method, a vacuum box detection method, a dipole method and the like. The infrared detection method needs to preheat the HDPE film and positions a damaged area through the temperature difference characteristic between the damaged area and the complete area, and has the defect that damage identification can be realized only when the temperature of the damaged area and the temperature of the complete area are greatly different, so that the detection efficiency of the method is low; the vacuum box method needs to humidify the surface of the HDPE film by using soapy water, judges whether the HDPE film is damaged or not through the pressure change in the box, and has the defect that detection leakage is caused by easy air leakage in the box; the dipole method needs to prewet the HDPE film, and judges the damage position through the potential abnormal area, and has the defect of large labor workload.

Aiming at the defects that the HDPE film is subjected to preheating treatment by an existing HDPE film damage detection method, the HDPE film is easy to leak air in a box by a vacuum box detection method, detection is missed, the film has conductive characteristics due to the fact that a dipole method needs humidifying treatment, and the like, the HDPE film damage positioning system utilizing the ultrasonic wave scattering characteristic is provided by the invention, the HDPE film damage positioning system utilizes the fact that ultrasonic waves are scattered when passing through a damage position, and has the characteristics that the closer the damage and the sensing path are, the more serious the energy attenuation is, the accurate positioning of the HDPE film damage position is realized, and the defects of low timeliness, gas leakage, large manual workload and the like can be effectively overcome.

Disclosure of Invention

In order to solve the above problems, the present invention provides a system for locating damage to HDPE film in a landfill site by using ultrasonic scattering characteristics, which can extract ultrasonic scattering signals passing through the damaged location of HDPE film, and finally realize accurate location of damage to HDPE bare film through data processing.

In order to achieve the above object, the present invention provides a method for locating damage to HDPE film in a landfill, which mainly utilizes the ultrasonic scattering property, and uses the wave piezoelectric sheets laid on the upper surface of the HDPE film to be detected in a rectangular manner (or in other regular geometric shapes), and uses the wave piezoelectric sheet generator to control half of the (designated) piezoelectric sheets to generate ultrasonic waves by self-oscillation, and preferably, to prevent the mutual interference of the detection systems, the other (e.g. opposite) piezoelectric sheets are designated to receive ultrasonic signals. Scanning is completed according to the process, an analog quantity damage signal is obtained, time-energy density characteristics are extracted through analog-to-digital conversion and wavelet analysis, damage positioning is achieved by combining probability imaging according to energy density difference when damage exists, damage alarm is given out through system control, and damage positions can be displayed. The system can solve the problems of low timeliness, gas leakage, large workload and the like of the existing bare membrane detection method, and can realize the active detection of the HDPE membrane through the induced vibration piezoelectric plate, thereby effectively reducing the omission factor.

The invention also provides a HDPE film damage positioning system using the method, which mainly comprises an ultrasonic generation module and an ultrasonic receiving and processing module, wherein the ultrasonic generation module mainly comprises a plurality of piezoelectric sheets and a waveform generator; the receiving processing module mainly comprises a piezoelectric sheet, an A/D converter and a processor; the processor scans each piezoelectric piece to obtain the received ultrasonic signal as an analog quantity damage signal, extracts time-energy density characteristics through analog-to-digital conversion and wavelet analysis, and combines probability imaging to realize damage positioning according to energy density difference when damage exists.

Preferably, above-mentioned scheme still can include host computer and siren, and wherein, the treater on the one hand with the ultrasonic signal storage that the piezoelectric patches produced, on the other hand with the HDPE membrane damage position information transmission that obtains to the host computer, after detecting the HDPE membrane damage, the siren reports to the police, and the host computer shows the damaged position, makes things convenient for the constructor to repair.

The invention has the beneficial effects that by means of the technical scheme, the detection method has the following advantages by utilizing the characteristics of rapid ultrasonic signal transmission, small clutter interference and the like:

(1) the system has short detection period and strong timeliness.

(2) The invention can induce the piezoelectric plate to realize the active detection of the damage of the HDPE film and can effectively reduce the omission factor.

(3) The detection process is high in intelligence, and the manual workload can be reduced.

(4) The system does not relate to material properties, has no requirements on the wave velocity of signals before and after damage, and greatly avoids the defects of the existing geometric positioning method.

Drawings

FIG. 1 is a schematic view of an HDPE film piezoelectric plate arrangement of an HDPE film damage positioning system of a refuse landfill;

FIG. 2 is a schematic diagram of a monitoring network sensing path of a refuse landfill HDPE membrane damage locating system of the present invention;

FIG. 3 is a schematic plan view of the affected area of the sensing path of a HDPE film damage locating system for a landfill of the present invention;

FIG. 4 is a schematic view of a landfill damage detection according to an embodiment of the present invention;

FIG. 5 is a circuit diagram of an ultrasonic generator according to an embodiment of the present invention;

FIG. 6 is a signal conversion circuit diagram according to an embodiment of the present invention;

FIG. 7 is a circuit diagram of a processor according to an embodiment of the present invention;

FIG. 8 is an alarm circuit according to an embodiment of the present invention;

FIG. 9 is a host computer circuit diagram according to an embodiment of the present invention;

FIG. 10 is a schematic diagram of an embodiment of a parallel line piezoelectric patch arrangement and sensing paths;

FIG. 11 is a schematic diagram of a circular piezoelectric patch arrangement and sensing paths according to an embodiment

FIG. 12 is a schematic diagram of the triangular piezoelectric patch arrangement and sensing paths according to an embodiment.

Wherein: 1-18 are piezoelectric patches.

Detailed Description

The HDPE film damage detecting system according to the present invention will be described in three aspects of function, composition and operation principle by way of examples and with reference to the accompanying drawings, and the technical solution of the present invention will be further described in detail.

The technical scheme of the invention is to detect the damage position of the HDPE film by acquiring ultrasonic parameters. The key point is that the HDPE film damage location of the refuse landfill is realized by means of a rectangular piezoelectric sheet laid on the HDPE film, utilizing the ultrasonic scattering characteristic in the nondestructive state and combining wavelet transformation and probability damage imaging. In addition, the ultrasonic wave utilized by the invention is scattered when passing through the damaged position, and the characteristic that the closer the damaged and sensing path is, the more serious the energy attenuation is, thereby realizing the active detection of the damaged position of the HDPE film and being capable of accurately positioning. The method can effectively overcome the defects of low timeliness, gas leakage, large manual workload and the like of the existing detection method.

The system is realized by laying piezoelectric sheets on the upper surface of an area to be detected of the HDPE film in a rectangular arrangement, controlling self-oscillation of half of the piezoelectric sheets to generate ultrasonic waves by a waveform generator, and appointing opposite piezoelectric sheets to receive ultrasonic signals in order to prevent mutual interference of detection systems. Scanning is completed according to the process, an analog quantity damage signal is obtained, time-energy density characteristics are extracted through analog-to-digital conversion and wavelet analysis, damage positioning is achieved by combining probability imaging according to energy density difference when damage exists, damage alarm is given out through system control, and damage positions can be displayed. The system can solve the problems of low timeliness, gas leakage, large workload and the like of the existing bare membrane detection method, and can realize the active detection of the HDPE membrane through the induced vibration piezoelectric plate, thereby effectively reducing the omission factor.

The main functions of the refuse landfill HDPE membrane damage positioning system utilizing the ultrasonic scattering characteristic are as follows: and the active detection of the damage of the HDPE film is realized by utilizing the ultrasonic scattering characteristic.

The main components are as follows: the invention mainly comprises a piezoelectric sheet and an arbitrary waveform generator.

The working principle is as follows: piezoelectric plates are arranged on an HDPE film in a rectangular mode and are sequentially numbered, and as shown in figure 1, the system is a schematic diagram of the arrangement of the HDPE film piezoelectric plates of the HDPE film damage positioning system for the refuse landfill utilizing the ultrasonic scattering property. The waveform generator controls the adjacent two edge piezoelectric sheets to generate ultrasonic waves, and the opposite edge piezoelectric sheets are selected as receivers, as shown in fig. 2: the 1 st to 10 th piezoelectric plates 1 to 10 carry out self-excited oscillation to generate ultrasonic waves, and 55 sensing path detection networks covering the rectangular detection area are obtained.

The scattering of a single sensing path caused by damage of the HDPE film occurs, and the mesh division in the form of an elliptical track on a damage detection area is shown in fig. 3, that is, the ultrasonic scattering characteristics of different damage positions on the same elliptical track are the same, and the damage probability value is larger as the mesh (the shaded part in fig. 3) is closer to the elliptical axis. And (4) performing data superposition on the damage probability values of any position in the detection area, wherein the coordinate of the point with the maximum value is the damage position.

Wavelet transforming the ultrasonic signal as a function of a scale parameter a and a time parameter b:

f (t) represents the ultrasonic signal measured by the piezoelectric sheet, psi (t) represents the wavelet basis function, psi^*(t)Denotes the complex conjugate of ψ (t), WT (a, b) being the function after wavelet transform processing.

According to the equidistant characteristic of the wavelet transform, the energy conservation in the wavelet transform process of the signal f (t) can obtain:

C_ψrepresents a solubility condition, | WT (a, b) & gtY luminous²dadb/C_ψa²Representing the signal as a function of a and time bPoint, energy with a scale interval da and a time interval db;

equation (2) can be written as:

wherein:

e (b) is the energy value of the ultrasonic signal at the moment b, which is a time-energy density function and reflects the energy distribution condition of the signal frequency;

equation (5) represents the transformation of energy with parameter b in the interval of scale a,

e' (b) is expressed in the scale [ a ]₁,a₂]The local time-energy density function is obtained by changing the value of the scale a, so that the distribution of the ultrasonic signals along with the time is obtained;

after the HDPE film lossless and lossy signals are subjected to wavelet transform processing, the energy density difference of the ultrasonic signals is compared, and the damage index DI in a time-frequency domain is as follows:

b (t) represents an ultrasonic reference signal when the HDPE film is not damaged, and D (t) represents an ultrasonic signal in a damaged state. A larger DI value indicates that the lesion is close to the sensing path; the smaller the DI value is, the farther the damage position is from the sensing path;

and corresponding DI values on the sensing path to positions in the rectangular detection area through a weighted distribution function, wherein a spatial distribution function R (x, y) of DI is as follows:

wherein (x)_a,y_a) To excite the piezoelectric patch coordinates, (x)_t,y_t) To receive the piezoelectric patch coordinates, (x)_k,y_k) Is the coordinate of any point in the rectangular area, d_kD represents a parameter of each sensing path influenced by the size of the divided grid, and the smaller D is, the influence degree is, the distance between the sensing path and the sum of the distances from any point of the detection area to the voltage generating and emitting sheet is, and the distance between the sensing path and the sum of the distances from the detection area to the voltage generating and emitting sheet is the ratio of the distance between the detection area and the sum of the distances from any point of the detection area to the voltage generating and emitting sheet to the sensing path;

and performing data superposition on the damage probability values of the multiple sensing paths, wherein the point with the maximum superposition value is the damage position. In order to solve the problem of dispersed positioning results, an enhancement factor is introduced to realize accurate positioning of the damage position, and the algorithm is as follows:

wherein n is the number of sensing paths participating in superposition; DI_kThe damage index of the kth sensing path is; u is an enhancement factor, and I is a damage probability value;

and (3) the coordinate (x, y) when the value I is maximum is the damage position of the HDPE film.

The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

Fig. 4 is a schematic diagram of detection of damage to a landfill site based on ultrasonic scattering characteristics, which is a specific embodiment of the present invention, and the area of a HDPE film detection region is 5m × 4m, 5 piezoelectric patches are horizontally laid, 4 piezoelectric patches are longitudinally laid, and the adjacent distance is 1 m. The detection system comprises an ultrasonic wave generation module and an ultrasonic wave receiving and processing module. The ultrasonic wave generation module consists of a piezoelectric sheet and a waveform generator; the receiving and processing module consists of a piezoelectric plate, an A/D converter, a processor, an upper computer and an alarm.

In the specific embodiment, the piezoelectric plate is CZ 25437-0015-.

As shown in fig. 5, a circuit diagram of an ultrasonic generator according to an embodiment of the present invention is shown, the ultrasonic generator employs an IC555 type integrated circuit, the circuit is connected to a multivibrator, an RP potentiometer controls an oscillation frequency, an ultrasonic signal is output from a pin 3 of the IC555 integrated circuit, and a piezoelectric plate B is driven to emit an ultrasonic wave after capacitive coupling by a C3 and boosting by a transformer T.

Referring to fig. 6, a signal conversion circuit diagram according to an embodiment of the invention is shown, in which a successive approximation type a/D converter is used to convert an ultrasonic analog signal collected by a piezoelectric patch ultrasonic probe into a digital signal through an AIN3 interface, wherein 2046A pins 1, 2, and 3 are connected to pins P3.3, P3.2, and P3.1 of a processor, pin 5 is connected to VCC, pin 12 is connected to the ultrasonic probe, pin 13 is connected to a reference voltage VCC2, and pin 16 is connected to pin P3.4.

The processor system of this particular embodiment:

fig. 7 is a circuit diagram of a processor of this embodiment, the processor is an STC single chip microcomputer with a 32-bit address bus, the processor stores the ultrasonic signal generated by the piezoelectric sheet, and transmits the obtained HDPE film damage position information to an upper computer, and an operating circuit of the processor is as shown in fig. 7. The resistor R9, the capacitor C14 and the reset button RSTK1 form a reset circuit; the capacitors C12, C13 and the 12MHZ crystal oscillator Y2 form a crystal oscillator circuit; the power supply is realized by connecting the USB interface with an external power supply.

When the HDPE film damage is detected, the alarm gives an alarm, the circuit is shown in fig. 8, the J7 interface is connected with a P3.0 pin of the processor, and the alarm of the passive alarm is realized by continuously outputting high and low levels through the processor.

Simultaneously, the damaged position of host computer demonstration makes things convenient for constructor to repair. The upper computer circuit is shown in fig. 9, wherein the 7 th to 14 th pins are connected with a port P0 of the processor, the 21 st to 28 th pins are connected with a port P1, and the 4 th, 5 th, 6 th, 15 th and 16 th pins are connected with pins P2.6, P2.5, P2.7, P3.3 and P3.4 of the processor respectively.

The above is exemplified by the piezoelectric sheet arrangement method and the transceiving manner shown in fig. 1 and fig. 2, but the piezoelectric sheet arrangement and the transceiving manner can form a plurality of shape detection areas, and the positioning model can be applied, in order to achieve full area coverage and convenient calculation when establishing a mathematical model, the arrangement should preferably be a single regular geometric figure, for example, a planar polygon or a parallel line arrangement manner can be adopted, wherein the planar polygon includes a rectangle, parallel lines, a circle (regular infinite polygon), a triangle, and the like, and the following other arrangement manners are briefly described as follows:

fig. 10 is a schematic diagram of piezoelectric sheets arranged in parallel lines and sensing paths thereof in another embodiment. The piezoelectric sheets are arranged in a parallel line mode, the upper half portion of the piezoelectric sheets are controlled to sequentially generate ultrasonic waves, and the opposite side piezoelectric sheets are used as ultrasonic receivers.

Fig. 11 is a schematic diagram of a piezoelectric sheet and its sensing path arranged in a circular manner in another embodiment. The piezoelectric patches are arranged in a circular mode in an area to be detected of the HDPE film, the piezoelectric patches generate ultrasonic waves in sequence, and the rest piezoelectric patches are used as receivers.

FIG. 12 is a schematic diagram of a triangular arrangement of piezoelectric patches and their sensing paths in another embodiment. The piezoelectric sheets are arranged in a triangular mode, the piezoelectric sheets are controlled to sequentially generate ultrasonic waves according to numbers, and under the condition that the piezoelectric sheets are not mutually influenced, the rest piezoelectric sheets are selected as receivers.

When the piezoelectric sheets are arranged in different regular geometric shapes, n in the formula (9) is correspondingly modified, and when the piezoelectric sheets are arranged in a rectangular mode, a parallel line, a circle or a triangle, n is 55, 25, 45 and 55 respectively.

In any way, the number of the piezoelectric sheets and the density of the sensing paths will affect the positioning accuracy.

Although the present invention has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the spirit and scope of the invention.