AU2022430004A1 - Method and System for Active Detection of Door Sealing Performance and Leakage Point Location - Google Patents
Method and System for Active Detection of Door Sealing Performance and Leakage Point Location Download PDFInfo
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Abstract
The present invention discloses a method and system for active detection of a leakage point
location, and the method of active detection includes: Step Sl: obtaining a reference sound pressure
setting threshold; step S2: transmitting a pulsed ultrasonic signal by a pulsed ultrasonic generator
placed on one side of a protection door, acquiring four-channel raw signals with an array detector at
different detection distances respectively, extracting sound pressure feature values of four channels
after processing, and acquiring a video image and a detection distance; step S3: setting different
leakage level thresholds based on the extracted sound pressure feature values of the four channels
and the reference sound pressure setting threshold; and step S4: detecting a sound pressure value
with the array detector at the other side of the protection door, when the measured sound pressure
value exceeds a first level leakage threshold, performing an envelope cross-correlation operation
based on adaptive filtering on the four-channel raw signals to obtain three time delay differences
between three channels and another channel, and combining the test distance and a sound pressure
amplitude ratio with the measured sound pressure values of the four channels to calculate
three-dimensional space coordinates of a leakage point.
1
Description
Method and System for Active Detection of Door Sealing Performance and Leakage Point Location
Cross Reference to Related Applications This application claims the benefit of the Chinese Patent Application No. 202210181445.9, filed on February 25, 2022, the contents of which are incorporated herein by reference.
Field of the Invention The present invention relates to the technical field of leakage detection, and more particularly to a method and system for active detection of a leakage point location.
Background of the Invention Civil air defense engineering is a special underground building with strict protection requirements, which not only meets the needs of economic construction, urban construction and people's life in peacetime, but also plays an important role in air defense and disaster prevention in wartime. It has dual functions in peacetime and wartime. If the sealing work during the protection is not in place, it will cause huge losses to the national economy and even threaten people's life safety. Therefore, it is very important to detect the sealing performance of civil air defense engineering facilities. At present, ultrasonic testing of concrete defects is mainly based on measuring the relative changes of acoustic parameters such as velocity, amplitude and main frequency of ultrasonic pulse waves propagating in concrete, so as to judge the defects of concrete. However, for testing the sealing performance of concrete protection doors, it is necessary to pay more attention to the sealing state of door cracks and rubber strip bonding positions, which is more different from the principle of detecting defects by the conventional ultrasonic method. In addition, the structure of a civil air defense basement is closed, the structure of the concrete protection door facility is huge, and the engineering quantity is huge. Rapid and accurate detection and indication of the leakage position put forward higher requirements for ultrasonic detection technology. The information disclosed in this background section is only intended to increase understanding of the general background of the invention and should not be taken to acknowledge or in any form imply that this information constitutes the prior art already known to those of ordinary skill in the art.
Summary of the Invention
An objective of the present invention is to provide a method and system for active detection of a leakage point location in order to solve the above-mentioned problems of the background art. To achieve the above objective, the present invention provides a method for active detection of a leakage point location, including the following steps: Step SI: detecting, by sound pressure receivers disposed at four corners of a protection door, four background sound pressure values of a current environment, and taking an average of the four background sound pressure values as a reference sound pressure setting threshold; Step S2: transmitting a pulsed ultrasonic signal at regular intervals by a pulsed ultrasonic generator placed on one side of the protection door, acquiring four-channel raw signals with an array detector at different detection distances respectively, converting the four-channel raw signals into four-channel voltage signals, extracting sound pressure feature values of four channels based on the four-channel voltage signals, and acquiring a video image about the protection door and the different detection distances; Step S3: setting different leakage level thresholds based on the extracted sound pressure feature values of the four channels and the reference sound pressure setting threshold; and Step S4: detecting a sound pressure value with the array detector moving along a guide line of a video image at the other side of the protection door to acquire measured sound pressure values of the four channels; comparing an average measured sound pressure value of the four channels with different leakage level thresholds; when the average measured sound pressure value exceeds a first level leakage threshold, indicating that there is a leakage in the current environment, performing an envelope cross-correlation operation based on adaptive filtering on the four-channel raw signals to obtain three time delay differences between three channels and another one of the four channels, and combining test distances and the measured sound pressure values of the four channels to calculate three-dimensional space coordinates of a leakage point in a fusion mode. In a preferred embodiment, the method further includes the following steps: Step S5: when the measured sound pressure value is less than or equal to the first level leakage threshold value, a leakage quantity of the current environment is minute, moving a linear array of four analog microphones in space until the measured sound pressure value exceeds the first level leakage threshold value, repeating the step S4; and Step S6: subjecting the three-dimensional space coordinates and image coordinates to a mapping process, transparently superimposing a point displayed in a color contour on the video image to visualize the leakage point. In a preferred embodiment, in step S2, extracting the sound pressure feature values of the four channels includes the following steps:
Step S2.1: performing waveform selection and smoothing filtering: performing segmented extraction on the signal-conditioned four-channel voltage signals; for each channel voltage signal, sorting by amplitude in a time domain, choosing a segment of data having an amplitude between %-90% of a maximum value to form a valid data segment corresponding to each channel voltage signal (i.e., to reject other data points); Step S2.2: performing cubic spline interpolation on each valid data segment in order to increase data sampling points; and Step S2.3: counting frequency distribution of data, taking a peak value of the each valid data segment as a voltage feature value U of a corresponding channel, and obtaining a sound pressure feature value SPL of the corresponding channel with a voltage-to-sound pressure conversion formula, wherein the voltage-to-sound pressure conversion formula is as follows: (0.707u/675)/o.oos) SPL (dB) = 12 x log 2XO
In a preferred embodiment, in step S3, setting the different leakage level thresholds based on the extracted sound pressure feature values of the four channels and the reference sound pressure setting threshold includes the following steps. Step S3.1: taking an average of the sound pressure feature values of the four channels obtained in step S2 to obtain an attenuation curve of the sound pressure feature value with a detection distance; and Step S3.2: at each detection distance, taking a difference between the sound pressure feature value and the reference sound pressure setting threshold value obtained in step Sl, taking the sums of %, 30%, and 50% of the difference and the reference sound pressure setting threshold as a first level leakage threshold, a second level leakage threshold, and a third level leakage threshold, respectively, wherein the first level leakage threshold indicates negligible leakage, the second level leakage threshold indicates non-negligible leakage, but no immediate repair is required, and the third level leakage threshold indicates non-negligible leakage, and immediate repair is required. In a preferred embodiment, in step S4, calculating the three-dimensional space coordinates of the leakage point in a fusion mode includes the following steps: Step S4.1: extracting valid data segments for the four-channel raw signals obtained in step S2, comparing differences in averages of amplitudes of two segments of data every 100 data points to find a segment of data where a pulse signal occurs, and taking 100 data points before and after the segment of data; the process of extracting the valid data segments in step S4.1 being similar to the process of forming the valid data segments in step S2.1;
Step S4.2: extracting an envelope for the selected data segment, and performing a cross-correlation calculation on the envelopes of two channels, wherein the cross-correlation calculation formula of the two channels is as follows:
R ((r) = x (n)x2 (n + r)
wherein xl (n), x2 (n) are the signal sequences of a first channel and a second channel, respectively, T is a delay point number;
Step S4.3: inputting the envelopes of the two channels into an adaptive filter; assigning a weight vector to one of the channels, based on an adaptive filtering algorithm, constantly updating a weight coefficient by calculating an iteration error until the iteration error is minimal, at this point, considering that the correlation of the two channels is maximum, and at this time, obtaining the delay point numbers of the two channels by the formula in step S4.2; performing feature conversion on the three delay point numbers to obtain three arrival time differences in a case that three delay point numbers of the three channels and another channel are obtained; and then multiplying the three arrival time differences by the speed of sound respectively to obtain three arrival distance differences; Step S4.4: performing feature conversion on the measured sound pressure values of the four channels to obtain three arrival distance ratios; and Step S4.5: taking a test distance as one component of the three-dimensional space coordinates of the leakage point, establishing a first system of spherical coordinate equations with respect to the three-dimensional space coordinates having the center of the linear array as an origin according to the three arrival distance differences, establishing a second system of spherical coordinate equations with respect to the three-dimensional space coordinates having the center of the linear array as an origin according to the three arrival distance ratios, and solving the three-dimensional space coordinates with a fusion algorithm according to results of the first system of spherical coordinate equations and the second system of spherical coordinate equations. In a preferred embodiment, in step S4.4, performing feature conversion on the measured sound pressure values of the four channels to obtain three arrival distance ratios includes: firstly, converting the measured sound pressure values of the four channels into corresponding four distances by using the attenuation curve obtained in step S3.1, and then calculating the ratios of three distances of the four distances corresponding to the three channels to another distance corresponding to another channel. In a preferred embodiment, the mapping process in step S6 includes the following steps:
Step S6.1: dividing a video picture into 320*180 grids, and each pixel point corresponding to each three-dimensional space coordinate; Step S6.2: taking the center of the video picture as an origin, mapping the origin at the center of the linear array, moving a reference target, establishing a mapping relationship of an interval point number and a test distance, wherein, the interval point number is a pixel point number corresponding to a unit distance along an abscissa axis direction or an ordinate axis direction in the video picture; and Step S6.3: converting the three-dimensional space coordinates calculated in step S4.5 into a pixel coordinate point according to the established mapping relationship, and superimposing the pixel coordinate point on a screen. In a preferred embodiment, the method further includes the following step: when a leakage point is detected in space but is not in the display range of the video picture, moving leftward or rightward until a positioning point appears on the screen, then performing step S4. In a preferred embodiment, the linear array of the four analog microphones has a sampling frequency of 100 kHz, the sound pressure receiver includes a power supply module and a wireless transmission module, and the sound pressure receiver is attracted on the protection door by a magnet, and the collected background sound pressure value of the current environment is transmitted to the computer using the wireless transmission module. In a preferred embodiment, the step of taking the average of the four background sound pressure values as the reference sound pressure setting threshold is performed in the case that fluctuation of the four background sound pressure values does not exceed a preset range. The present invention also provides a system for active detection of a leakage point location, the system for active detection includes: four sound pressure receivers, disposed at four corners of a protection door, configured to detect four background sound pressure values of a current environment, and taking an average of the four background sound pressure values as a reference sound pressure setting threshold; a pulsed ultrasonic generator, disposed at one side of the protection door for transmitting a pulsed ultrasonic wave signal at regular intervals; an array detector, configured to acquire four-channels raw signals at different detection distances, and convert the four-channel raw signals into four-channel voltage signals, extract sound pressure feature values of four channels based on the four-channel voltage signals, and acquire a video image about the protection door and the different detection distances; and a setting apparatus, configured to set different leakage level thresholds based on the extracted sound pressure feature values of the four channels and the reference sound pressure setting threshold, the array detector is further configured to detect a sound pressure value with the array detector moving along a guide line of a video image at the other side of the protection door to acquire measured sound pressure values of the four channels; compare an average measured sound pressure value of the four channels with different leakage level thresholds; when the average measured sound pressure value exceeds a first level leakage threshold, indicate that there is a leakage in the current environment, perform an envelope cross-correlation operation based on adaptive filtering on the four-channel raw signals to obtain three time delay differences between three channels and another one of the four channels; and combine test distances and the measured sound pressure values of the four channels to calculate the three-dimensional space coordinates of a leakage point in a fusion mode. In a preferred embodiment, the array detector includes a linear array of four analog microphones, a computer processing unit, a signal conditioning circuit board, a camera module and a ranging module. In a preferred embodiment, the linear array of the four analog microphones has a sampling frequency of 100kHz, the sound pressure receiver includes a power supply module and a wireless transmission module, and the sound pressure receiver is attracted on the protection door by a magnet. Compared with the prior art, the beneficial effects of the present invention are: 1. The present invention utilizes actively transmitted pulsed ultrasonic signals, and acquires four-channel raw signals using the linear array of four analog microphones, extracts stable sound pressure feature values through waveform selection, smoothing filtering, and interpolation operation optimization algorithm; each channel delay difference is calculated by signal envelope cross-correlation; the three-dimensional space coordinates of the leakage position are iteratively calculated by data fusion, thereby improving accuracy and stability of positioning. 2. The present invention utilizes the mapping process of the three-dimensional space coordinates and pixel coordinates to visualize the leakage position, and performs positioning by moving the linear array, it is possible to detect the situation that multiple leakage points occur, thus greatly improving the detection efficiency. 3. The present invention sets different leakage level thresholds based on the extracted sound pressure feature values of the four channels, and the leakage level thresholds can be self-set and judged according to the current detection environment to adapt to test scenarios under different environmental noises. Other features and advantages of the present invention will be described in detail in the detailed description section that follows.
Brief Description of Drawings The accompanying drawings are included to provide a further understanding of embodiments of the invention and constitute a part of this specification, and together with the detailed description below serve to explain, but not limit, the embodiments of the invention. In the drawings: FIG. 1 is a system block diagram of a preferred embodiment of the present invention. FIG. 2 is a flowchart of a data fusion algorithm in a positioning algorithm of the preferred embodiment of the present invention. FIG. 3 is a diagram of a visual positioning result of an interface of the system of the present invention.
Detailed Description of the Embodiments The technical solutions in the embodiments of the present invention will be clearly and completely described below. The embodiments of the present invention, and all other embodiments obtained by those of ordinary skill in the art without making inventive labor, belong to the scope of protection of the present invention. Embodiment 1: As shown in FIGS. 1-2, a method for active detection of door sealing performance and a leakage point location according to a preferred embodiment of the present invention includes the following steps. Step S1: four background sound pressure values of a current environment are detected by sound pressure receivers disposed at four corners of a protection door, and an average of the four background sound pressure values is taken as a reference sound pressure setting threshold. In step S1, the step that the average of the four background sound pressure values is taken as the reference sound pressure setting threshold is performed in a case that the fluctuation of the four background sound pressure values does not exceed a preset range. For example, when the fluctuation of the four background sound pressure values does not exceed 5%, the average of the four background sound pressure values is taken as the reference sound pressure setting threshold. Step S2: a pulsed ultrasonic signal is transmitted at regular intervals by a pulsed ultrasonic generator placed on one side of the protection door, four-channel raw signals are acquired by a linear array of four analog microphones at different detection distances respectively, the four-channel raw signals are converted into four-channel voltage signals on one side of the protection door, the signal-conditioned four-channel voltage signals are transmitted to a computer processing unit, sound pressure feature values of the four channels are extracted by the computer processing unit, and a video image and the different detection distances are acquired by using a camera module and a ranging module simultaneously. Specifically, the step that the sound pressure feature values of the four channels are extracted includes the following steps: Step S2.1: waveform selection: segmented extraction is performed on the signal-conditioned four-channel voltage signals; for each channel voltage signal, sorting is performed by amplitude in a time domain, a segment of data having an amplitude between 80%-90% of a maximum value is selected to form a valid data segment corresponding to each channel voltage signal (i.e., to remove other data points); Step S2.2: balanced filtering: cubic spline interpolation is performed on each valid data segment in order to increase data sampling points; Step S2.3: frequency distribution of data is counted, a peak value of the each valid data segment is taken as a voltage feature value U of a corresponding channel, and a sound pressure feature value SPL of the corresponding channel is obtained with a voltage-to-sound pressure conversion formula, wherein the voltage-to-sound pressure conversion formula is as follows: (0.707U/675)/0.005 SPL (dB) = 12 x log 2X1O_
Step S3: different leakage level thresholds are set based on the extracted sound pressure feature values of four channels and the reference sound pressure setting threshold. In particular, the step that the different leakage level thresholds are set based on the extracted sound pressure feature values of the four channels and the reference sound pressure setting threshold includes the following steps: Step S3.1: an average of the sound pressure feature values of the four channels obtained in step S2 is taken to obtain an attenuation curve of the sound pressure feature value with a detection distance; and Step S3.2: at each detection distance, a difference between the sound pressure feature value and the reference sound pressure setting threshold value obtained in step SI is taken, the sums of 10%, %, and 50% of the difference and the reference sound pressure setting threshold are taken as a first level leakage threshold, a second level leakage threshold, and a third level leakage threshold, respectively. Wherein the first level leakage threshold indicates negligible leakage, the second level leakage threshold indicates non-negligible leakage, but no immediate repair is required, and the third level leakage threshold indicates non-negligible leakage, and immediate repair is required.
Step S4: a sound pressure value is detected with the array detector moving along a guide line of a video image at the other side of the protection door to acquire measured sound pressure values of the four channels; an average measured sound pressure value of the four channels is compared with different leakage level thresholds; when the average measured sound pressure value exceeds a first level leakage threshold, it is indicated that there is a leakage in the current environment, an envelope cross-correlation operation is performed based on adaptive filtering on the four-channel raw signals to obtain three time delay differences between three channels and another one of the four channels; the tests distance and the measured sound pressure values of the four channels are combined to calculate three-dimensional space coordinates of a leakage point in a fusion mode. In particular, the step that the three-dimensional spatial coordinates of the leakage point are calculated in a fusion mode includes the following steps. Step S4.1: valid data segments are extracted for the four-channel raw signals obtained in step S2, differences in averages of amplitudes of two segments of data are compared every 100 data points to find a segment of data where a pulse signal occurs, and 100 data points before and after the segment of data are taken. Step S4.2: an envelope for the selected data segment is extracted, and a cross-correlation calculation is performed on the envelopes of two channels, wherein the cross-correlation calculation formula of the two channels is as follows:
() x , (n)x, (n+ r)
wherein xi(n), xj(n) are signal sequences of channel i and channel j respectively, i, j = 1, 2, 3, 4 and i is not equal to j, T is a delay point number. In various embodiments, the first channel is taken as the reference channel (i.e., another channel of the four channels), the cross-correlation calculation formula between any one of the three channels of the four channels (e.g., the second channel) and the reference channel is as follows:
Rx1x2 (T) x(n)X 2 (n + T)
wherein xi(n), x2(n) are the signal sequences of a first channel and a second channel, respectively, ' is a delay point number. Step S4.3: the envelopes of the two channels are input into an adaptive filter, a weight vector is assigned to one of the channels, a weight coefficient is constantly updated by calculating an iteration error based on an adaptive filtering algorithm until the iteration error is minimal, at this point, it is considered that the correlation of the two channels is maximum.
At this time, the delay point numbers of the two channels are obtained by the formula in step S4.2, feature conversion is performed on the three delay point numbers to obtain three arrival time differences in a case that three delay point numbers of the three channels and another channel are obtained, and then the three arrival time differences are multiplied by the speed of sound respectively to obtain three arrival distance differences. Step S4.4: feature conversion is performed on the measured sound pressure values of the four channels to obtain three arrival distance ratios. Step S4.5: a test distance is taken as one component of the three-dimensional space coordinates of the leakage point, a first system of spherical coordinate equations with respect to the three-dimensional space coordinates having the center of the linear array as an origin is established according to the three arrival distance differences, a second system of spherical coordinate equations with respect to the three-dimensional space coordinates having the center of the linear array as an origin is established according to the three arrival distance ratios, and the three-dimensional space coordinates are solved with a fusion algorithm according to results of the first system of spherical coordinate equations and the second system of spherical coordinate equations. Further, the step S4.4 that feature conversion is performed on the measured sound pressure values of the four channels to obtain three arrival distance ratios includes: firstly, the measured sound pressure values of the four channels are converted into corresponding four distances by using the attenuation curve obtained in step S3.1, and then the ratios of three distances of the four distances corresponding to the three channels to another distance corresponding to another channel are calculated. Step S5: when the measured sound pressure value is less than or equal to the first level leakage threshold value, a leakage quantity of the current environment is minute, a linear array of four analog microphones is moved in space until the measured sound pressure value exceeds the first level leakage threshold value, the step S4 is repeated. Step S6: the three-dimensional space coordinates and image coordinates are subjected to a mapping process, a point displayed in a color contour is transparently superimposed on the video image to visualize the leakage point. Specifically, the mapping process in step S6 includes the following steps: Step S6.1: a video picture is divided into 320*180 grids, and each pixel point corresponds to each three-dimensional space coordinate. Step S6.2: the center of the video picture is taken as an origin, the origin is mapped at the center of the corresponding linear array, and a reference target is moved, a mapping relationship of an interval point number and a test distance is established, wherein the interval point number is a pixel point number corresponding to a unit distance along an abscissa axis direction or an ordinate axis direction in the video picture. Step S6.3: the three-dimensional space coordinates calculated in step S4.5 are converted into a pixel coordinate point according to the established mapping relationship, and the pixel coordinate point is superimposed on a screen. Further, the method further includes the following step: when a leakage point is detected in space but is not in the display range of the video picture, leftward or rightward moving is performed until a positioning point appears on the screen, then step S4 is performed. Further, the linear array of the four analog microphones has a sampling frequency of100kHz, the sound pressure receiver includes a power supply module and a wireless transmission module, and the sound pressure receiver is attracted on the protection door by a magnet, and the collected background sound pressure value of the current environment is transmitted to the computer using the wireless transmission module. Embodiment 2: As shown in FIG. 1, the present invention also provides a system for active detection of door sealing performance and a leakage point location, including: a linear array 301 of four analog microphones (the detection frequency is from audible sound to 80kHz), a pulsed ultrasonic generator 302 with adjustable frequency and amplitude, a sound pressure receiver 303, an array detector 304, a computer 305, a signal conditioning circuit board, a camera module and a ranging module. The sound pressure receivers 303 are disposed on four corners of the protection door 300 to detect background sound pressure values of the current environment, and when the fluctuation of the four background sound pressure values does not exceed 5%, an average is taken as a reference sound pressure setting threshold. The sampling frequency of the linear array 301 of the four analog microphones is 100kHz, the sound pressure receiver 303 includes a power supply module and a wireless transmission module, the sound pressure receiver 303 is attracted on the protection door 300 by a magnet, and transmits the collected background sound pressure value of the environment to the computer 305 using the wireless transmission module. A pulsed ultrasonic generator 302 is placed on the side of the protection door for transmitting a pulsed ultrasonic wave signal at regular intervals, four-channel raw signals are acquired with four analog microphones of the linear array 301 at different detection distances on the other side of the protection door, respectively, and the four-channel raw signals are converted into four-channel voltage signals, the signal-conditioned four-channel voltage signals are transmitted to the computer 305 processing unit, sound pressure feature values of the four channels are extracted, and a video image and a detection distance are acquired by using the camera module and the ranging module simultaneously.
Further, a sound pressure value is detected with the array detector 304 (which includes a linear array 301 of four analog microphones, a computer processing unit, a signal conditioning circuit board, a camera module, and a ranging module) moving along a guide line of a video image at the other side of the protection door, the measured sound pressure value is compared with set different leakage level thresholds (the sums of 10%, 30%, and 50% of the difference and the reference sound pressure setting threshold are taken as a first level leakage threshold, a second level leakage threshold, and a third level leakage threshold, respectively), when the measured sound pressure value exceeds the first-level leakage threshold, it is indicated that leakage exists in the current environment, an envelope cross-correlation operation based on adaptive filtering is performed on the four-channel raw signals to obtain time delay differences of the channels, and test distances and the measured sound pressure values of the four channels are combined to calculate the three-dimensional space coordinates of a leakage point in a fusion mode. The three-dimensional space coordinates and the image coordinates are then subjected to a mapping process, a point displayed in a color contour is transparently superimposed on the image to visualize the leakage point, thereby visualizing the positioning result on the human-machine interface of the computer, as shown in FIG. 3. Embodiment 3: A specific embodiment of the method for active detection of door sealing performance and a leakage point location according to the present invention is described in detail below. Step SI: the sound pressure receivers are adsorbed at the four corners of the protection door with magnets, background sound pressure values of the current environment are detected, and are transmitted into the computer through wireless communication technology, the four sound pressure values are 29.2dB, 29dB, 28.8dB, 29dB respectively, fluctuation dose not exceed 5%, and the average of 29dB is taken as the reference sound pressure setting threshold. Step S2, a pulsed ultrasonic generator is placed, the frequency is set to 40kHz, the amplitude is set to 5V, a pulsed ultrasonic signal is transmitted every Is, sound signals are acquired at a distance of 100mm-3m using a linear array of four analog microphones and are converted into voltage signals, a sampling frequency is 100kHz, and the voltage signals are transmitted to a computer after signal conditioning, sound pressure feature values of four channels are extracted, and a video image and and the different detection distances are acquired by using a camera module and a ranging module simultaneously. Further, the step S2 that the sound pressure values are extracted includes the following steps. Step S2.1: waveform selection and smoothing filtering are performed: segmented extraction is performed on the obtained four-channel voltage signals; for each channel voltage signal, sorting is performed by amplitude in a time domain, a segment of data having an amplitude between 80%-90% of a maximum value is selected to form a valid data segment corresponding to each channel voltage signal (i.e., to remove other data points), 100 data points are reserved for each channel of data. Step S2.2: cubic spline interpolation is performed on each valid data segment in order to increase data sampling points. Step S2.3: frequency distribution of data is counted, a peak value of the each valid data segment is taken as a voltage feature value U of a corresponding channel, and a sound pressure feature value SPL of the corresponding channel is obtained with the following formula. (0.707U/675)/0.005 SPL (dB) = 12 x log 2X1O
Step S3: different leakage level thresholds are set by taking a detection distance of 100mm as an example. Further, the step S3 that the leakage level thresholds are set is achieved by the following steps. Step S3.1: an average of the sound pressure feature values of the four channels obtained in step S2.3 is taken to obtain an attenuation curve of the sound pressure feature value with a detection distance; wherein the sound pressure feature average is 55.6dB when the detection distance is 100mm. Step S3.2: at a detection distance of 100mm, a difference between the sound pressure feature value and the reference value obtained in step Si is taken to be 26.6dB, the sums of 10%, 30%, and % of the difference and the reference value are taken as a first level leakage threshold, a second level leakage threshold, and a third level leakage threshold, respectively,, i.e., the leakage thresholds of three levels are 31.66dB, 36.98dB, and 42.3dB, respectively, wherein the three levels represent negligible leakage, non-negligible leakage (no immediate repair is required), and non-negligible leakage (immediate repair is required), respectively. Step S4: a pulsed ultrasonic generator is placed on one side of the protection door, the frequency is set to be 40kHz, and the amplitude is set to be 5V, a pulsed ultrasonic signal is transmitted every Is, an array detector on the other side of the protection door performs detection, the test distance is 100mm, the measured sound pressure value is 34.7dB and exceeds the first level leakage threshold, it is indicated that there is leakage in the current environment, the array detector moves to detect along a guide line of a video image, an envelope cross-correlation operation is performed based on adaptive filtering on the four-channel raw signals obtained in step S2 to obtain the time delay differences of the channels, and test distances and the measured sound pressure values of the four channels are combined to calculate three-dimensional space coordinates of a leakage point in a fusion mode.
Further, the step S4 that the three-dimensional spatial coordinates of the leakage point are calculated in a fusion mode is performed by the following steps. Step S4.1: valid data segments are extracted for the four-channel raw signals obtained in step S2, differences in averages of amplitudes of two segments of data (from the same channel) are compared every 100 data points to find a segment of data where a pulse signal occurs, and 100 data points before and after the segment of data are taken, there are 300 data points in total. Step S4.2: an envelope for the selected data segment is extracted, and a cross-correlation calculation is performed on the envelopes of two channels, the first channel and the second channel are taken as an example, wherein the cross-correlation calculation formula of the two channels is as follows:
R (r)(= x1 (n)x 2 (n + r)
wherein xi(n), x2(n) are signal sequences of the first channel and the second channel respectively, and T is a delay point number; the delay point number T 12 between the second channel and the first channel is calculated to be 12, and similarly, the delay point number between the third channel and the first channel and the delay point number between the fourth channel and the first channel can be calculated. Step S4.3: the envelopes of the two channels are input into an adaptive filter; a weight vector is assigned to one of the channels; a weight coefficient is constantly updated by calculating an iteration error until the iteration error is minimal, at this point, it is considered that the correlation of the two channels is maximum, based on an adaptive filtering algorithm, the formula as follows:
y 1 (n) = wT(n)x 1 (n)
e (n)= X2(n)-yx(()
w(n)= w(n)+ e(n) X(n) x1(n)* x'(n)
wherein w(n) represents the weight coefficient, e(n) represents the error per iteration, and y1(n) is the sequence of the first channel sequence multiplied by the weight coefficient. At this point, the delay point number112 = 6 between two channels is re-obtained by the formula in step S4.2, the delay point number obtained in step S4.2 is calculated before passing through the adaptive filter, and after the step S4.3, the delay point number is changed when the error is minimal due to the constant updating to minimize the iteration error, and the delay point number 112 = 6 is obtained after the filtering algorithm. After feature conversion, the arrival time difference of the second channel and the first channel At 12 = 60[s is obtained, and then is multiplied by the speed of sound 343m/s to obtain an arrival distance difference between the second channel and the first channel Ad 12 = 20.58mm, and so on, the arrival distance difference between the third channel and the first channel one Ad13 = 24.35mm, and the arrival distance difference between the fourth channel and the first channel Ad 14 = 13.67mm are obtained; Step S4.4: feature conversion is performed on the measured sound pressure values of the four channels to obtain three arrival distance ratios. i.e. the measured sound pressure values of the four channels are first converted into corresponding four distances using the attenuation curve of step S3.1, ratios of three of the four distances corresponding to the three channels to another distance corresponding to another channel, respectively, are calculated. For example, the arrival distance ratio ki2 between the second channel and the first channel is calculated to be 1.18, the arrival distance ratio k 1 3 between the third channel and the first channel is calculated to be 1.23, and the arrival distance ratio k 14 between the fourth channel and the first channel is calculated to be 1.07. Step S4.5: a test distance is taken as one component of the three-dimensional space coordinates of the leakage point, a first system of spherical coordinate equations with respect to the three-dimensional space coordinates having the center of the linear array as an origin is established according to the three arrival distance differences, a second system of spherical coordinate equations with respect to the three-dimensional space coordinates having the center of the linear array as an origin is established according to the three arrival distance ratios, and the positioning coordinates (11.3mm, 9.78mm, 102.05mm) are solved with a fusion algorithm according to results of the first system of spherical coordinate equations and the second system of spherical coordinate equations. That is, the coordinates of the leakage point are taken as unknowns, systems of equations are respectively established according to the arrival distance difference and the arrival distance ratio to obtain data of two sets of three-dimensional space coordinates, and the average of the two sets of data is taken to calculate thefinal three-dimensional space position of the leakage point. Step S6: the positioning coordinates (i.e., the three-dimensional space coordinates) calculated in step S4 and the image coordinates are subjected to a mapping process. a point displayed in a color contour is transparently superimposed on the video image to visualize the leakage point. Further, the mapping process in the step S6 is performed by the following steps: Step S6.1: a video picture is divided into 320*180 grids, and each pixel point corresponds to each space coordinate; Step S6.2: the center of the video picture is taken as an origin, corresponding to the center of the linear array; a reference target is moved, and a mapping relationship of an interval point number and a distance is established; wherein the interval point number is a pixel point number corresponding to a unit distance along an abscissa axis direction or an ordinate axis direction in the video picture. For example, when the test distance is 100mm (102.05mm of the three-dimensional space coordinates (11.3mm, 9.78mm, 102.05mm) calculated at step S4.5 is approximately equal to 100mm), the mapping relationship between the interval point number and the distance is N= 2*d. Step S6.3: the three-dimensional space coordinates calculated in step S4.5 are converted into a pixel coordinate point (23, 20) according to the mapping relationship, and the pixel coordinate point is superimposed on a screen. Through step S6.2, it can be determined that when the test distance is determined to be 100mm, the mapping relationship between the interval point number and the distance is N=2*d, and the corresponding coordinate point (22.6, 20) can be determined by substituting the distance 11.3 mm on the abscissa axis and the distance 9.78 mm on the ordinate axis in the three-dimensional space coordinates (11.3 mm, 9.78 mm, 102.05 mm) calculated in step S4.5 into the mapping relationship. Since the pixel point can only be an integer, the pixel coordinate point (23, 20) can be obtained by rounding. The present invention also provides a system for active detection of a leakage point location, the active detection system includes: four sound pressure receivers, disposed at four corners of a protection door, configured to detect background sound pressure values of a current environment, and taking an average of the four background sound pressure values as a reference sound pressure setting threshold; a pulsed ultrasonic generator, disposed at one side of the protection door for transmitting a pulsed ultrasonic wave signal at regular intervals; an array detector, configured to acquire four-channels raw signals at different detection distances, and convert the four-channel raw signals into four-channel voltage signals, extract sound pressure feature values of four channels based on the four-channel voltage signals, and acquire a video image and a detection distance about the protection door; and a setting apparatus, configured to set different leakage level thresholds based on the extracted sound pressure feature values of the four channels and the reference sound pressure setting threshold, the array detector is further configured to detect a sound pressure value with the array detector moving along a guide line of a video image at the other side of the protection door to acquire measured sound pressure values of the four channels, and compare an average measured sound pressure value of the four channels with different leakage level thresholds, when the average measured sound pressure value exceeds a first level leakage threshold, indicate that there is a leakage in the current environment, perform an envelope cross-correlation operation based on adaptive filtering on the four-channel raw signals to obtain three time delay differences between three channels and another one of the four channels, and combine test distances and the measured sound pressure values of the four channels to calculate the three-dimensional space coordinates of a leakage point in a fusion mode. The steps performed by the setting apparatus may be performed by a computer. In one embodiment, the present invention provides the method for active detection of door sealing performance and a leakage point location, including the following steps: Step SI: background sound pressure values of the current environment are detected by sound pressure receivers arranged at four corners of the protection door, an average is taken as a reference sound pressure setting threshold when the fluctuation of the four background sound pressure values does not exceed 5%; Step S2: a pulsed ultrasonic generator is arranged on one side of the protection door, a pulsed ultrasonic signal is transmitted at regular intervals, four-channel raw signals are acquired with an array detector of four analog microphones at different detection distances respectively, the four-channel raw signals are converted into voltage signals and then are transmitted to a computer processing unit after signal conditioning, sound pressure feature values of four channels are extracted, and a video image and a current detection distance are acquired by a camera module and a ranging module simultaneously; Step S3: different leakage level thresholds are set based on the extracted sound pressure feature values of the four channels; Step S4: a sound pressure value is detected with the array detector moving along a guide line of a video image at the other side of the protection door; a measured sound pressure value is compared with different leakage level thresholds, when the measured sound pressure value exceeds a first level leakage threshold, it is indicated that there is a leakage in the current environment; an envelope cross-correlation operation based on adaptive filtering is performed on the four-channel raw signals to obtain channel delay differences, and test distances and sound pressure amplitude ratios are combined to calculate three-dimensional space coordinates of a leakage point in a fusion mode. Preferably, the method further includes the following steps: Step S5: when the measured sound pressure value is less than or equal to the first level leakage threshold value, the leakage quantity of the current environment is minute; a linear array is moved in space until the measured sound pressure value exceeds the first level leakage threshold value, the step S4 is repeated; and Step S6: the three-dimensional space coordinates and image coordinates are subjected to a mapping process, a point displayed in a color contour is transparently superimposed on the image to visualize the leakage point.
Preferably, the step S2 that the sound pressure feature values of the four channels are extracted includes the following steps: Step S2.1: segmented extraction is performed on the four-channel voltage signals, sorting is performed by amplitude in a time domain, a segment of data having an amplitude between 80%-90% of a maximum value is chosen to remove other data points; Step S2.2: cubic spline interpolation is performed on each data segment in order to increase data sampling points; and Step S2.3: frequency distribution of data is counted, a peak value is taken as a voltage feature value of a channel, and a sound pressure feature value of the corresponding channel is obtained with a voltage-to-sound pressure conversion formula, wherein the voltage-to-sound pressure conversion formula is as follows: (0.707u/675)/o.oos) SPL (dB) = 12 x log 2XO
Preferably, the step S3 that the different leakage level thresholds are set based on the extracted sound pressure feature values of the four channels includes the following steps: Step S3.1: an average of the sound pressure feature values of the four channels obtained in step S2 is taken to obtain an attenuation curve of the sound pressure feature value with a distance; and Step S3.2: at each detection distance, a difference between the sound pressure feature value and the reference sound pressure setting threshold value obtained in step S Iis taken, the sums of 10%, %, and 50% of the difference and the reference sound pressure setting threshold are taken as a first level leakage threshold, a second level leakage threshold, and a third level leakage threshold, respectively. Wherein the first level leakage threshold indicates negligible leakage, the second level leakage threshold indicates non-negligible leakage, but no immediate repair is required, and the third level leakage threshold indicates non-negligible leakage, and immediate repair is required. Preferably, the step 4 that the three-dimensional space coordinates of the leakage point are calculated in a fusion mode includes the following steps: Step S4.1: valid data segments are extracted for the four-channel raw signals obtained in step S2, differences in averages of amplitudes of two segments of data are compared every 100 data points to find a segment of data where a pulse signal occurs, and 100 data points before and after the segment of data are taken; Step S4.2: an envelope for each of the selected data segments is extracted, and a cross-correlation calculation is performed on the envelopes of two channels. Wherein the cross-correlation calculation formula of the two channels is as follows:
R (r)= x 1 (n)x 2 (n + r)
wherein xi(n), x2(n) are the signal sequences of the first channel and the second channel, respectively, T is the delay point number; Step S4.3: the envelopes of the two channels are input into an adaptive filter, a weight vector is assigned to one of the channels; based on an adaptive filtering algorithm, a weight coefficient is constantly updated by calculating an iteration error until the iteration error is minimal, at this point, it is considered that the correlation of the two channels is maximum; at this time, the delay point numbers of the two channels are obtained by the formula in step S4.2, after feature conversion, arrival time differences are obtained, and then the arrival time differences are multiplied by the speed of sound respectively to obtain arrival distance differences; Step S4.4: feature conversion is performed on the measured sound pressure values of the four channels to obtain arrival distance ratios; Step S4.5: a test distance is taken as one component of the three-dimensional space coordinates of the leakage point, a spherical coordinate equation system of multi-dimensional scale is established with the center of the linear array as the origin, and the three-dimensional space coordinates is solved with a fusion algorithm. Preferably, the step S4.4 that feature conversion is performed on the sound pressure feature values of the four channels to obtain the arrival distance ratios includes: firstly, the sound pressure feature value is corresponding to a distance using the attenuation curve of the step S3.1, and then ratio calculation is performed. Preferably, the mapping process in step S6 includes the following steps: Step S6.1: a video picture is divided into 320*180 grids, and each pixel point corresponds to each three-dimensional space coordinate. Step S6.2: the center of the video picture is taken as an origin which is corresponding to the center of the linear array, and a reference target is moved, a mapping relationship of an interval point number and a test distance is established. Step S6.3: the three-dimensional space coordinates calculated in step S4.5 are converted into a pixel coordinate point according to the established mapping relationship, and the pixel coordinate point is superimposed on a screen. Preferably, the method further includes the following step: when a leakage point is detected in space but is not in the display range of the video picture, leftward or rightward moving is performed until a positioning point appears on the screen, then step S4 is performed.
Preferably, the linear array of the four analog microphones has a sampling frequency of 100 kHz, the sound pressure receiver includes a power supply module and a wireless transmission module, and the sound pressure receiver is attracted on the protection door by a magnet, and the collected background sound pressure value of the current environment is transmitted to the computer using the wireless transmission module. The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, however, the present invention is not limited to the specific details in the above embodiments, and many simple variations can be made to the technical solutions of the present invention within the scope of the technical idea of the present invention, and these simple variations all belong to the protection scope of the present invention. It should also be noted that the various specific features described in the above detailed description can be combined in any suitable manner without contradiction, and in order to avoid unnecessary duplication, the invention is not further described with respect to the possible combinations. Additionally, although the embodiments of the present invention have been illustrated and described, it would be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (14)
1. A method for active detection of a leakage point location, comprising the following steps: Step SI: detecting, by sound pressure receivers disposed at four corners of a protection door, four background sound pressure values of a current environment, and taking an average of the four background sound pressure values as a reference sound pressure setting threshold; Step S2: transmitting a pulsed ultrasonic signal at regular intervals by a pulsed ultrasonic generator placed on one side of the protection door, acquiring four-channel raw signals with an array detector at different detection distances respectively, converting the four-channel raw signals into four-channel voltage signals, extracting sound pressure feature values of four channels based on the four-channel voltage signals, and acquiring a video image about the protection door and the different detection distances; Step S3: setting different leakage level thresholds based on the extracted sound pressure feature values of the four channels and the reference sound pressure setting threshold; and Step S4: detecting a sound pressure value with the array detector moving along a guide line of a video image at the other side of the protection door to acquire measured sound pressure values of the four channels; comparing an average measured sound pressure value of the four channels with different leakage level thresholds; when the average measured sound pressure value exceeds a first level leakage threshold, indicating that there is a leakage in the current environment, performing an envelope cross-correlation operation based on adaptive filtering on the four-channel raw signals to obtain three time delay differences between three channels and another one of the four channels; and combining test distances and the measured sound pressure values of the four channels to calculate three-dimensional space coordinates of a leakage point in a fusion mode.
2. The method for active detection of a leakage point location according to claim 1, further comprising the following steps: Step S5: when the measured sound pressure value is less than or equal to the first level leakage threshold value, a leakage quantity of the current environment is minute, moving a linear array of four analog microphones in space until the measured sound pressure value exceeds the first level leakage threshold value, repeating the step S4; and Step S6: subjecting the three-dimensional space coordinates and image coordinates to a mapping process, transparently superimposing a point displayed in a color contour on the video image to visualize the leakage point.
3. The method for active detection of a leakage point location according to claim 2, wherein in step S2, extracting the sound pressure feature values of the four channels comprises the following steps: Step S2.1: performing segmented extraction on the signal-conditioned four-channel voltage signals; for each channel voltage signal, sorting by amplitude in a time domain, choosing a segment of data having an amplitude between 80%-90% of a maximum value to form a valid data segment corresponding to each channel voltage signal; Step S2.2: performing cubic spline interpolation on each valid data segment in order to increase data sampling points; and Step S2.3: counting frequency distribution of data, taking a peak value of the each valid data segment as a voltage feature value U of a corresponding channel, and obtaining a sound pressure feature value SPL of the corresponding channel with a voltage-to-sound pressure conversion formula, wherein the voltage-to-sound pressure conversion formula is as follows: (0.707u/675)0.00s SPL (dB) = 12 x log 2X1O
4. The method for active detection of a leakage point location according to claim 3, wherein in step S3, setting the different leakage level thresholds based on the extracted sound pressure feature values of the four channels and the reference sound pressure setting threshold comprises the following steps: Step S3.1: taking an average of the sound pressure feature values of the four channels obtained in step S2 to obtain an attenuation curve of the sound pressure feature value with a detection distance; and Step S3.2: at each detection distance, taking a difference between the sound pressure feature value and the reference sound pressure setting threshold value obtained in step Sl, taking the sums of %, 30%, and 50% of the difference and the reference sound pressure setting threshold as a first level leakage threshold, a second level leakage threshold, and a third level leakage threshold, respectively, wherein the first level leakage threshold indicates negligible leakage, the second level leakage threshold indicates non-negligible leakage, but no immediate repair is required, and the third level leakage threshold indicates non-negligible leakage, and immediate repair is required.
5. The method for active detection of a leakage point location according to claim 4, wherein in step 4, calculating the three-dimensional space coordinates of the leakage point in a fusion mode comprises the following steps:
Step S4.1: extracting corresponding valid data segments for the four-channel raw signals obtained in step S2, comparing differences in averages of amplitudes of two segments of data in the same valid data segment every 100 data points to find a segment of data where a pulse signal occurs, and taking 100 data points before and after the segment of data; Step S4.2: extracting an envelope for each of the selected data segments, and performing a cross-correlation calculation on the envelopes of two channels, wherein the cross-correlation calculation formula of the two channels is as follows:
(T)=x, (n)x, (n+ c)
wherein xi(n), xj(n) are signal sequences of channel i and channel j respectively, i, j = 1, 2, 3, 4 and i is not equal to j, T is a delay point number;
Step S4.3: inputting the envelopes of the two channels into an adaptive filter; assigning a weight vector to one of the channels; based on an adaptive filtering algorithm, constantly updating a weight coefficient by calculating an iteration error until the iteration error is minimal, at this point, considering that the correlation of the two channels is maximum, and at this time, obtaining the delay point numbers of the two channels by the formula in step S4.2; performing feature conversion on the three delay point numbers to obtain three arrival time differences in a case that three delay point numbers of the three channels and another channel are obtained; and then multiplying the three arrival time differences by the speed of sound respectively to obtain three arrival distance differences; Step S4.4: performing feature conversion on the measured sound pressure values of the four channels to obtain three arrival distance ratios; and Step S4.5: taking a test distance as one component of the three-dimensional space coordinates of the leakage point, establishing a first system of spherical coordinate equations with respect to the three-dimensional space coordinates having the center of the linear array as an origin according to the three arrival distance differences, establishing a second system of spherical coordinate equations with respect to the three-dimensional space coordinates having the center of the linear array as an origin according to the three arrival distance ratios, and solving the three-dimensional space coordinates with a fusion algorithm according to results of the first system of spherical coordinate equations and the second system of spherical coordinate equations.
6. The method for active detection of a leakage point location according to claim 5, wherein in step S4.4, performing feature conversion on the measured sound pressure values of the four channels to obtain the three arrival distance ratios comprises: firstly, converting the measured sound pressure values of the four channels into corresponding four distances by using the attenuation curve obtained in step S3.1, and then calculating the ratios of three distances of the four distances corresponding to the three channels to another distance corresponding to another channel.
7. The method for active detection of a leakage point location according to claim 6, wherein the mapping process in step S6 comprises the following steps: Step S6.1: dividing a video picture into 320*180 grids, and each pixel point corresponding to each three-dimensional space coordinate; Step S6.2: taking the center of the video picture as an origin, mapping the origin at the center of the linear array, moving a reference target, establishing a mapping relationship of an interval point number and a test distance, wherein the interval point number is a pixel point number corresponding to a unit distance along an abscissa axis direction or an ordinate axis direction in the video picture; and Step S6.3: converting the three-dimensional space coordinates calculated in step S4.5 into a pixel coordinate point according to the established mapping relationship, and superimposing the pixel coordinate point on a screen.
8. The method for active detection of a leakage point location according to claim 7, further comprising the following step: when a leakage point is detected in space but is not in the display range of the video picture, moving leftward or rightward until a positioning point appears on the screen, then performing step S4.
9. The method for active detection of a leakage point location according to claim 1, wherein the array detector comprises a linear array of four analog microphones, a computer processing unit, a signal conditioning circuit board, a camera module and a ranging module.
10. The method for active detection of a leakage point location according to claim 9, wherein the linear array of the four analog microphones has a sampling frequency of 100kHz, the sound pressure receiver comprises a power supply module and a wireless transmission module, and the sound pressure receiver is attracted on the protection door by a magnet.
11. The method for active detection of a leakage point location according to claim 1, wherein the step of taking the average of the four background sound pressure values as the reference sound pressure setting threshold is performed in the case that fluctuation of the four background sound pressure values does not exceed a preset range.
12. A system for active detection of a leakage point location, comprising: four sound pressure receivers, disposed at four corners of a protection door, configured to detect four background sound pressure values of a current environment, and taking an average of the four background sound pressure values as a reference sound pressure setting threshold; a pulsed ultrasonic generator, disposed at one side of the protection door for transmitting a pulsed ultrasonic wave signal at regular intervals; an array detector, configured to acquire four-channels raw signals at different detection distances, and convert the four-channel raw signals into four-channel voltage signals, extract sound pressure feature values of four channels based on the four-channel voltage signals, and acquire a video image about the protection door and the different detection distances; and a setting apparatus, configured to set different leakage level thresholds based on the extracted sound pressure feature values of the four channels and the reference sound pressure setting threshold, the array detector is further configured to detect a sound pressure value with the array detector moving along a guide line of a video image at the other side of the protection door to acquire measured sound pressure values of the four channels; compare an average measured sound pressure value of the four channels with different leakage level thresholds; when the average measured sound pressure value exceeds a first level leakage threshold, indicate that there is a leakage in the current environment, perform an envelope cross-correlation operation based on adaptive filtering on the four-channel raw signals to obtain three time delay differences between three channels and another one of the four channels; and combine test distances and the measured sound pressure values of the four channels to calculate the three-dimensional space coordinates of a leakage point in a fusion mode.
13. The system for active detection of a leakage point location according to claim 11, wherein the array detector comprises a linear array of four analog microphones, a computer processing unit, a signal conditioning circuit board, a camera module and a ranging module.
14. The system for active detection of a leakage point location according to claim 13, wherein the linear array of the four analog microphones has a sampling frequency of 100 kHz, the sound pressure receiver comprises a power supply module and a wireless transmission module, and the sound pressure receiver is attracted on the protection door by a magnet.
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