CN108277720B - Asphalt mixing station aggregate grading online detection and anti-overflow control method and system - Google Patents
Asphalt mixing station aggregate grading online detection and anti-overflow control method and system Download PDFInfo
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- CN108277720B CN108277720B CN201810063153.9A CN201810063153A CN108277720B CN 108277720 B CN108277720 B CN 108277720B CN 201810063153 A CN201810063153 A CN 201810063153A CN 108277720 B CN108277720 B CN 108277720B
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- 238000000034 method Methods 0.000 title claims abstract description 58
- 239000010426 asphalt Substances 0.000 title claims abstract description 44
- 238000002156 mixing Methods 0.000 title claims abstract description 41
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- 230000033228 biological regulation Effects 0.000 claims abstract description 12
- 239000002245 particle Substances 0.000 claims description 73
- 238000012545 processing Methods 0.000 claims description 33
- 239000004567 concrete Substances 0.000 claims description 20
- 239000000203 mixture Substances 0.000 claims description 20
- 239000011384 asphalt concrete Substances 0.000 claims description 16
- 238000004458 analytical method Methods 0.000 claims description 14
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- 238000004364 calculation method Methods 0.000 claims description 8
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- 238000011068 loading method Methods 0.000 claims description 8
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- 238000011160 research Methods 0.000 claims description 2
- 238000003756 stirring Methods 0.000 abstract description 5
- 230000001276 controlling effect Effects 0.000 description 5
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- 238000004519 manufacturing process Methods 0.000 description 4
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- 230000001133 acceleration Effects 0.000 description 1
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- 238000005265 energy consumption Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
- E01C19/00—Machines, tools or auxiliary devices for preparing or distributing paving materials, for working the placed materials, or for forming, consolidating, or finishing the paving
- E01C19/02—Machines, tools or auxiliary devices for preparing or distributing paving materials, for working the placed materials, or for forming, consolidating, or finishing the paving for preparing the materials
- E01C19/10—Apparatus or plants for premixing or precoating aggregate or fillers with non-hydraulic binders, e.g. with bitumen, with resins, i.e. producing mixtures or coating aggregates otherwise than by penetrating or surface dressing; Apparatus for premixing non-hydraulic mixtures prior to placing or for reconditioning salvaged non-hydraulic compositions
- E01C19/1059—Controlling the operations; Devices solely for supplying or proportioning the ingredients
- E01C19/1068—Supplying or proportioning the ingredients
- E01C19/1072—Supplying or proportioning the ingredients the solid ingredients
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- Preparation Of Clay, And Manufacture Of Mixtures Containing Clay Or Cement (AREA)
Abstract
The invention provides an on-line detection and anti-overflow control method and system for aggregate grading of an asphalt mixing plant, wherein the system comprises the following steps: the device comprises a plurality of feeding bins, a plurality of aggregate conveyor belts, terminal equipment, a PLC (programmable logic controller), a frequency converter and a plurality of motors; the quantity of the feeding bin, the aggregate conveyor belt and the motor is the same; an aggregate conveyor belt is arranged right below each feeding bin; a camera bellows is fixedly arranged on the guide rail of each aggregate conveyor belt; the camera bellows is internally provided with lighting equipment; the top of the camera bellows is provided with an image collector; the terminal equipment is connected with the image collector to receive and process the collected images; the terminal equipment is connected with the PLC to send the speed ratio which needs to be achieved by each aggregate conveyor belt; the PLC is connected with the frequency converter; the frequency converter is connected with all motors; each motor is connected with an aggregate conveyor belt for speed regulation control. The invention can make the aggregate grading qualified and meet the proportioning requirement, and can effectively prevent the overflow phenomenon in the asphalt stirring process.
Description
Technical Field
The invention relates to the technical field of detection and the field of engineering machinery, in particular to an on-line detection and anti-overflow control method and system for aggregate grading of an asphalt mixing station.
Background
How the quality of the asphalt mixing plant is, is a key factor influencing the quality of engineering. The flash problem is a serious problem frequently encountered in mixing building production, and is also an important factor for limiting construction progress and construction quality. If the flash phenomenon is slight, the flash material is wasted, the energy consumption is increased, and the yield is reduced; if the flash phenomenon is serious, the intermittent shutdown and ignition startup of the mixing plant are caused, so that on one hand, the stable production and paving are influenced, in particular, the intermittent shutdown of the paver influences the flatness, and on the other hand, the stability of the quality of the asphalt mixture is influenced. The reasons for the flash mainly comprise that the aggregate is unqualified in grading and the aggregate is improperly proportioned.
Aggregate grading is an important parameter for machine-made sand quality management, and the aggregate grading is not up to standard, so that the problems of high water consumption of concrete, large cement (gel material) consumption, poor durability and the like are caused; the porosity is increased, the more the gaps are, the larger the consumption of cement paste is needed, the cohesive force between aggregates is reduced, and the strength of concrete is reduced. The mixture with better grading composition is used, so that on one hand, higher productivity can be ensured in the process of producing asphalt concrete, and on the other hand, the phenomenon of waiting or overflowing of a hot bin caused by unqualified grading of the mixture can be avoided in the production.
The mixing ratio of the aggregate also has obvious influence on the economy and quality of the concrete. The granularity and the grain shape quality of the sand produced by the machine are uneven, and the grading monitoring is very necessary.
The aggregate is used as the main material of asphalt mixture and cement concrete, and accounts for more than 3/4 of the volume and mass of the concrete, and plays a role in skeleton and filling in the concrete. The characteristics of the concrete mixture have important influence on the workability of the concrete mixture, and are mainly reflected in three aspects of flow energy, cohesiveness and water retention. The good aggregate grain size grading reduces the stacking porosity of the concrete, ensures that the concrete has better workability, has good stability and durability, reduces the consumption of cement paste and reduces the cost of the concrete. The aggregate grading is monitored before the concrete is stirred, so that the particle grading of the aggregate meets national or industry standards, and the high-quality and high-performance concrete with higher quality can be obtained.
However, the existing concrete aggregate detection equipment has many problems, such as time and labor waste, sampling detection only, and incapability of truly reflecting the granularity detection data of the aggregate in the actual operation state. And the detection result of the sample often has time lag phenomenon with the actual production state of the concrete aggregate, so that the on-line detection cannot be realized.
Therefore, the method realizes the on-line detection of the grading of the stacked aggregate, and has great significance for monitoring and proportioning the grading of the aggregate, preventing the overflow in the asphalt stirring process and obtaining the concrete with higher quality.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides an on-line detection and anti-overflow control method and system for aggregate grading of an asphalt mixing plant; the aggregate can be directly detected in granularity without sample selection detection, the aggregate particles can be further subjected to statistical distribution analysis of the granularity, and meanwhile, aggregate mixtures consisting of aggregate particles with different grades can be generated according to the aggregate grading required by actual concrete, so that the aggregate grading is qualified and meets the proportioning requirement, and the phenomenon of flash in the asphalt stirring process is effectively prevented.
The technical scheme adopted for solving the technical problems is as follows:
an asphalt mixing plant aggregate grading control system comprising: the device comprises a plurality of feeding bins, a plurality of aggregate conveyor belts, terminal equipment, a PLC (programmable logic controller), a frequency converter and a plurality of motors; the number of the feeding bins, the aggregate conveyor belts and the motors is the same; an aggregate conveyor belt is arranged right below each feeding bin to convey stacked aggregates subjected to manual loading screening; a camera bellows is fixedly arranged on the guide rail of each aggregate conveyor belt; the camera bellows is internally provided with lighting equipment for adjusting the brightness of light rays in the camera bellows; the top of the camera bellows is provided with an image collector for collecting images of the aggregate to be tested; the terminal equipment is connected with the image collector to receive and process the collected images; the terminal equipment is connected with the PLC to send the speed ratio which needs to be achieved by each aggregate conveyor belt; the PLC is connected with the frequency converter; the frequency converter is connected with all motors; each motor is connected with an aggregate conveyor belt for speed regulation control.
Preferably, the terminal device includes: the system comprises an image processing module, a geometric feature analysis module, an aggregate granularity distribution result display module and a conveyor belt speed calculation module; the image processing module is used for processing the collected stacked aggregate images; the geometric feature analysis module is used for analyzing the aggregate image processed by the image processing module to obtain the geometric feature of each aggregate particle; the aggregate granularity distribution result display module is used for counting the geometric characteristics obtained by the geometric characteristic analysis module to obtain the grading result of aggregate; the conveyor belt speed calculation module calculates the speed ratio which needs to be achieved by each conveyor belt according to the particle size content of each grade of aggregate particles and the requirement of actual concrete on the proportion of each grade of aggregate particles.
An on-line detection method for aggregate grading of an asphalt mixing station, which is based on the aggregate grading control system of the asphalt mixing station, comprises the following steps:
the image collector collects images of the stacking aggregates subjected to manual loading and screening and sends the images to the terminal equipment;
the terminal equipment processes the collected stacked aggregate images;
the terminal equipment performs geometric feature analysis on the processed stacked aggregate image, and calculates geometric features of each aggregate particle in the stacked aggregate image;
and the terminal equipment analyzes and obtains the granularity distribution statistical information of the stacked aggregate according to the geometric characteristics of each aggregate particle in the stacked aggregate image.
Preferably, the image collector performs image collection on the stacking aggregate subjected to manual loading screening, and the image collector comprises:
setting an image acquisition area; the image acquisition area irradiates to the surface layer of the stacked aggregate in a certain area on the stacked aggregate conveyor belt.
Preferably, the processing of the acquired stacked aggregate image by the terminal device includes:
converting the collected stacked aggregate image into a gray scale image;
carrying out smooth image processing on the image subjected to graying by adopting a median filtering method;
performing threshold segmentation processing on the filtered stacked aggregate image by adopting a Niblack local threshold method based on clustering global threshold improvement, and converting the image into a binary image;
performing iterative morphological erosion operation on the stacked aggregate image subjected to the threshold segmentation treatment to separate particles in contact with each other in the image;
carrying out cavity treatment in the middle of filling particles on the stacked aggregate images subjected to morphological corrosion operation so as to eliminate noise formed by segmentation treatment of surface textures of the aggregate particles;
and (5) performing image calibration processing by adopting a pellet calibration method.
Preferably, the image calibration process further includes:
and (3) removing incomplete particles at the boundary, repeatedly identifying the aggregate by adopting a constant pitch for repeatedly shooting the particles, and then removing the particles.
Preferably, the threshold segmentation processing is performed on the filtered stacked aggregate image by adopting a Niblack local threshold method based on clustering global threshold improvement, surface aggregate is taken as a research object, and the lower incomplete aggregate is taken as a background, which specifically comprises the following steps:
a global threshold T1 of the stacked aggregate image after median filtering is obtained by using a clustering global threshold method;
dividing the whole image into nine subgraphs, and solving a local threshold T2 by using a Niblack algorithm for each subgraph;
weighting and summing a threshold value T1 obtained by a clustering method and a threshold value T2 obtained by a Niblack method to obtain a threshold value of each subgraph: t3=αt1+ (1- α) T2, where α represents a weighting coefficient.
Preferably, the image calibration processing is performed by adopting a pellet calibration method, which specifically comprises the following steps:
under the same image acquisition environment, carrying out image acquisition on a plurality of standard pellets with known diameters;
after the pellet image is subjected to image processing, calculating and obtaining a pixel area value of each pellet in the image;
and comparing the real area value of each small sphere with the pixel area value in the image, and taking the average value of the ratio as a calibration coefficient.
The control method for the aggregate grading anti-overflow material of the asphalt mixing station is based on the aggregate grading control system of the asphalt mixing station and comprises the following steps:
according to the requirements of actual asphalt concrete on the aggregate particle proportion of each level, the terminal equipment calculates the speed ratio which needs to be achieved by each conveyor belt and sends the speed ratio to the PLC;
the PLC controller sends various required speeds to the frequency converter according to the speed ratio so as to control the frequency converter to work;
the frequency converter provides voltage and frequency regulation power supply for the motor, and the speed of the motor is changed to control the speed of each aggregate conveyor belt.
Preferably, the calculating the speed ratio that each conveyor belt needs to reach includes:
the particle size content corresponding to different particle size intervals in each bin is respectively marked as A 1 、A 2 …A i ，B 1 、B 2 …B j ，C 1 、C 2 …C m … the width of the bin is s, the height of the bin from the aggregate conveyor is h, and the speed of each aggregate conveyor is V n In the mixture grading required by the asphalt concrete formulation, the conveying time of the aggregate conveyor belt is marked as t, and the content required by each aggregate grading is marked as M 1 、M 2 …M l The total mass of the asphalt concrete is Q; wherein n is a positive integer;
according to the aggregate content of the same grading in each bin corresponding to the aggregate content of each grading in the asphalt concrete, overlapping aggregate grading contents in each bin are overlapped to obtain the following formula:
M l ＝k 1 ·A 1 +…+k i ·A i +p 1 ·B 1 +…+p j ·B j +q 1 ·C 1 +…+q m ·C m +…
wherein,i. j and m are positive integers; k (k) 1 …k i Indicating that each bin contains particle size content A i The corresponding graded aggregate content coefficient ratio; p is p 1 …p j The representation shows that each bin contains particle size content B j The corresponding graded aggregate content coefficient ratio; q 1 …q m The representation shows that each bin contains particle size content C m The corresponding graded aggregate content coefficient ratio;
substituting each parameter into the above formula, the following formula can be obtained by mass conservation:
s·h·t·Fet[(A 1 +A 2 +…)V 1 +(B 1 +B 2 +…)V 2 +…]＝Q·M l
wherein, l is a positive integer,fet represents the content of the aggregate grading interval which is required to be the same as that in the asphalt concrete formula in each bin, and the overlapped aggregate grading content in each bin is overlapped;
calculate all V's meeting the equation n Solutions, and selecting a set of most appropriate solutions.
Compared with the prior art, the invention has the following beneficial effects:
(1) According to the aggregate gradation control system of the asphalt mixing station, disclosed by the invention, the image acquisition of stacked aggregates is realized by installing the image acquisition device on the aggregate conveying guide rail, and the aggregate gradation control of the asphalt mixing station is realized by the terminal equipment connected with the image acquisition device;
(2) According to the online detection method for aggregate gradation of the asphalt mixing plant, disclosed by the invention, a machine vision combined digital image processing technology is adopted, sample selection detection is not needed, the rapid online detection of aggregate granularity can be realized, the aggregate gradation condition can be reflected in time, and the instantaneity and the accuracy are improved;
(3) The aggregate grading anti-flash control method for the asphalt mixing plant adopts the aggregate conveyor belt with adjustable speed, and realizes the proportioning of aggregate particles matched with different levels by controlling the speed of the aggregate conveyor belt, thereby realizing the serious consequences caused by the flash prevention phenomenon in the asphalt mixing and stirring process.
The invention is further described in detail below with reference to the accompanying drawings and examples, but the method and the system for controlling aggregate grading on-line detection and anti-overflow of an asphalt mixing plant are not limited to the examples.
Drawings
FIG. 1 is a schematic diagram of an aggregate gradation control system of an asphalt mixing plant according to the present invention;
FIG. 2 is a schematic flow chart of an on-line detection method for aggregate gradation of an asphalt mixing plant;
FIG. 3 is a flow chart of an image processing method according to the present invention;
FIG. 4 is a schematic flow chart of a method for controlling aggregate grading overflow prevention in an asphalt mixing plant according to the invention;
FIG. 5 is a flow chart of a belt speed ratio calculation method according to the present invention;
fig. 6 is a flow chart of aggregate conveyor speed control according to the present invention.
Reference numerals: 101. the device comprises a feeding bin, 102, an aggregate conveyor belt, 103, a camera bellows, 104, lighting equipment, 105, an image collector, 106, a PLC (programmable logic controller), 107, a frequency converter, 108, a motor, 109, a recycled aggregate conveyor belt, 110 and terminal equipment.
Detailed Description
For a better understanding of the technical solution of the present invention, the embodiments provided by the present invention are described in detail below with reference to the accompanying drawings.
Referring to fig. 1, the aggregate grading control system of the asphalt mixing plant comprises: a plurality of feeding bins 101, a plurality of aggregate conveyor belts 102, terminal equipment 110, a PLC controller 106, a frequency converter 107 and a plurality of motors 108; the number of the feeding bins 101, the aggregate conveyor belt 102 and the motors 108 is the same; an aggregate conveyor belt 102 is arranged right below each feeding bin 101 to convey stacked aggregates subjected to manual loading screening; a camera bellows 103 is fixedly arranged on the guide rail of each aggregate conveyor belt 102; a lighting device 104 is arranged in the camera bellows 103 to adjust the brightness of the light rays in the camera bellows 103; an image collector 105 is arranged at the top of the camera bellows 103 to collect images of the aggregate to be tested; the terminal device 110 is connected to the image collector 105 to receive and process the collected image; the terminal equipment 110 is connected with the PLC controller 106 to send the speed ratio that each aggregate conveyor 102 needs to reach; the PLC 106 is connected with the frequency converter 107; the frequency converter 107 is connected with all motors 108; each motor 108 is connected to one aggregate conveyor 102 for timing control.
Specifically, the feeding bin 101 can be divided into six different bins (only three bins are shown in fig. 1) according to the international standard for conveying the stacked aggregates subjected to manual loading and screening onto the aggregate conveyor 102.
The lighting device 104 is in communication connection with the terminal device 110, and the lighting device 104 adjusts the brightness control parameters according to the information fed back by the terminal device 110.
The image collector 105 is used for collecting images of the aggregate to be tested. In this embodiment, the image collector 105 comprises an industrial camera. The image collector 105 is mounted in a position such that the field of view of the industrial camera covers the entire width of the conveyor belt so that each particle on the aggregate conveyor belt 102 is photographed. The frame rate of the selected industrial camera should meet the image acquisition speed requirement, the camera is connected with the terminal equipment 110 through a USB3.0 data line, and the acquisition interval time of the industrial camera is controlled by a parameter setting module in the terminal equipment 110.
The PLC controller 106 operates in a cyclic sequential scanning manner under the control and command of the terminal device 110, and indicates the system operating state by the digital output of the PLC controller 106, and controls the operation of the frequency converter 107 by a program.
The frequency converter 107, the main circuit of the frequency converter 107 provides voltage and frequency regulating power for the asynchronous motor 108, and various speed controls of the motor 108 are changed according to various frequency changes of the frequency converter 107, specifically, the power frequency alternating current power supply is firstly converted into direct current power supply through a rectifier, and then the direct current power supply is converted into alternating current power supply with controllable frequency and voltage so as to be supplied to the motor 108.
The motor 108 can realize speed regulation control of the conveyor belt by changing the power supply frequency of the cage type asynchronous motor 108, namely, changing the synchronous revolution number of the motor 108.
In this embodiment, the aggregate grading control system of the asphalt mixing plant further includes a recycled aggregate conveyor belt 109, which is used for recycling the finally obtained aggregate mixture meeting the grading requirement, and finally sending the aggregate mixture into asphalt mixing.
The terminal device 110, which may be a PC or a mobile terminal, is connected to the image collector 105 to control the exposure time and the collection frequency of the industrial camera; is connected with a backlight source to control the brightness of the light source of the lighting device 104; the device comprises an image processing module, a geometric characteristic analysis module, an aggregate granularity distribution result display module and a conveyor belt speed calculation module.
The image processing module is used for processing aggregate images acquired by the image acquisition device 105, and the image processing mainly uses a median filtering and Niblack local threshold method based on clustering global threshold improvement, so that each aggregate contour is clear and visible, and aggregate particle size distribution results are counted.
The geometric feature analysis module is connected with the image processing module, and analyzes the processed aggregate images to obtain geometric features of each aggregate particle, including projection perimeter, projection area and each direction diameter; the geometric characteristic analysis module is the basis of an aggregate particle size distribution result display module.
And the aggregate granularity distribution result display module is used for counting aggregate images calculated by the geometric characteristic analysis module to obtain and display aggregate grading results. The display items include a particle size distribution and a cumulative particle size distribution, expressed as the aggregate ratio of each fraction in the mix and the cumulative fractional screen of the mix, respectively.
The conveyor belt speed calculation module calculates the speed ratio which needs to be achieved by each conveyor belt according to the particle size content of each grade of aggregate particles with different orders of magnitude calculated by the aggregate particle size distribution result display module and the requirement of actual concrete on the proportion of each grade of aggregate particles.
In this embodiment, the terminal device 110 further includes an image real-time display module. The image real-time display module is used for displaying aggregate images acquired by the image acquisition device 105 in real time in the aggregate detection process, and confirming whether the conveying process stably runs or not and working states of the light source and the industrial camera. The user can also zoom in the image locally as required to observe the details of the aggregate on the conveyor belt.
Referring to fig. 2, the on-line detection method for aggregate grading of an asphalt mixing station provided by the invention is based on the aggregate grading control system of the asphalt mixing station, and comprises the following steps:
step 201, an image collector collects images of the manually loaded and screened stacked aggregates and sends the images to the terminal equipment;
step 202, processing the collected stacked aggregate image by a terminal device;
step 203, the terminal equipment performs geometric feature analysis on the processed stacked aggregate image, and calculates the geometric feature of each aggregate particle in the stacked aggregate image; the geometric features comprise a projection perimeter, a projection area and various direction diameters;
and 204, analyzing and obtaining the statistical information of the particle size distribution of the stacked aggregate by the terminal equipment according to the geometric characteristics of each aggregate particle in the stacked aggregate image and displaying the statistical information. Specifically, the display items include a particle size distribution and a particle size cumulative distribution, which are expressed as an aggregate ratio of each particle size fraction in the mix and a cumulative screen fraction of the mix, respectively.
Further, the image collector carries out image acquisition to the stacking aggregate subjected to manual loading screening, and the image collector comprises:
setting an image acquisition area; the image acquisition area irradiates to the surface layer of the stacked aggregate in a certain area on the stacked aggregate conveyor belt.
Referring to fig. 3, the processing, by the terminal device, the acquired stacked aggregate image includes:
step 301, converting the collected stacked aggregate image into a gray scale image;
in this embodiment, the gray value of each pixel is calculated by the following formula:
Gray＝R×0.299+G×0.587+B×0.114
wherein R, G, B represents the values of the three channels of red, green and blue of the pixel, respectively, and Gray represents the Gray value.
Step 302, carrying out smooth image processing on the image after graying by adopting a median filtering method so as to eliminate noise caused by rough textures on the surfaces of bricks and concrete;
in this embodiment, the median filtering replaces each pixel of the image with a 3 x 3 neighborhood (square area centered on the current pixel) pixel median.
The method specifically comprises the following steps:
the image is copied into a slightly larger image, with the new image being added one row and one column each, up and down and left and right, duplicating the nearest row or column in the original image to fill in the pixels.
And searching each 3X 3 pixel area in the image from left to right and from top to bottom in sequence, and taking the median value among the 9 pixel gray values in the area to replace the gray value of the central pixel of the 3X 3 area.
After all the areas are operated, deleting the added boundary to return the image to the original size.
Step 303, performing threshold segmentation processing on the filtered stacked aggregate image by adopting a Niblack local threshold method based on clustering global threshold improvement, and converting the image into a binary image;
in this embodiment, the surface aggregate is taken as a study object, and the incomplete aggregate in the lower layer is regarded as a background, and the steps specifically include:
a global threshold T1 of the stacked aggregate image after median filtering is obtained by using a clustering global threshold method;
dividing the whole image into nine subgraphs, and solving a local threshold T2 by using a Niblack algorithm for each subgraph;
weighting and summing a threshold value T1 obtained by a clustering method and a threshold value T2 obtained by a Niblack method to obtain a threshold value of each subgraph: t3=αt1+ (1- α) T2, where α represents a weighting coefficient.
Niblack is a common local dynamic thresholding method that can adaptively determine the threshold value in different image regions. However, the Niblack can generate pseudo noise when the aggregate is sparse, and the Niblack local threshold method based on the clustering global threshold improvement can avoid the generation of pseudo noise. Multiple experiments show that the image binarization effect is optimal when alpha=0.4 is taken, and the aggregate contour can be accurately distinguished.
Step 304, performing iterative morphological erosion operation on the stacked aggregate image subjected to the threshold segmentation treatment to separate particles in contact with the image;
step 305, carrying out cavity treatment in the middle of filling particles on the stacked aggregate images subjected to morphological corrosion operation so as to eliminate noise formed by segmenting surface textures of the aggregate particles;
step 306, removing incomplete particles at the boundary, repeatedly identifying the aggregate by adopting a constant distance for repeatedly shooting the particles, and then removing the particles;
in this embodiment, the steps specifically include:
removing incomplete particles at the boundary, and adopting the condition that the area perimeter ratio is smaller than 1 to judge whether the boundary particles are boundary particles or not, and removing the boundary particles from the outline;
in the image acquisition process, each particle may be photographed 1, 2 times, and the aggregate is repeatedly identified using invariant moment, so that the same aggregate appearing in different positions in both pictures is identified.
Step 307, performing image calibration processing by adopting a pellet calibration method;
in this embodiment, the steps specifically include:
under the same image acquisition environment, acquiring images of a plurality of standard pellets with known diameters;
after the pellet image is subjected to image processing, calculating and obtaining a pixel area value of each pellet in the image;
and comparing the real area value of each small sphere with the pixel area value in the image, and taking the average value of the ratio as the calibration coefficient of the system.
Referring to fig. 4, the method for controlling aggregate grading and overflow prevention of an asphalt mixing station according to the invention comprises the following steps:
step 401, according to the requirement of actual asphalt concrete on the proportion of aggregate particles distributed at each level, a terminal device calculates the speed ratio required to be achieved by each conveyor belt and sends the speed ratio to a PLC (programmable logic controller);
step 402, the PLC controller sends various speeds required to the frequency converter according to the speed ratio to control the frequency converter to work;
step 403, the frequency converter provides voltage and frequency regulation power supply for the motor, and the speed of the motor is changed to control the speed of each aggregate conveyor belt;
step 404, controlling the quantity of aggregate matched with each level to finish the matching, thereby realizing the purpose of preventing material overflow in the asphalt mixing and stirring process.
Referring to fig. 5, in this embodiment, the calculating the speed ratio that needs to be achieved by each conveyor belt includes:
step 501, respectively marking the particle size contents corresponding to different particle size intervals in each bin as A 1 、A 2 …A i ，B 1 、B 2 …B j ，C 1 、C 2 …C m …; a, B and C represent three different bins, and of course, other bins may be included according to actual requirements; the subscripts i, j, and m denote the types of aggregate contained in the respective bins, respectively.
Step 502, the width of the bin is denoted as s, the height of the bin from the aggregate conveyor is denoted as h, and the speed of each aggregate conveyor is denoted as V n The conveying time of the aggregate conveyor belt is recorded as t; wherein n is a positive integer;
in step 503, in the mixture grading required by the asphalt concrete formulation, the content required by each aggregate grading is recorded as M 1 、M 2 …M l The total mass of the asphalt concrete is Q;
step 504, adding the aggregate contents with the same grading in each bin according to the aggregate contents of each grade of the asphalt concrete actually required, and superposing the grading contents of the overlapped aggregates in each bin; the following formula is obtained:
M l ＝k 1 ·A 1 +…+k i ·A i +p 1 ·B 1 +…+p j ·B j +q 1 ·C 1 +…+q m ·C m +…
wherein i, j and m are positive integers; k (k) 1 …k i Indicating that each bin contains particle size content A i The corresponding graded aggregate content coefficient ratio; p is p 1 …p j The representation shows that each bin contains particle size content B j The corresponding graded aggregate content coefficient ratio; q 1 …q m The representation shows that each bin contains particle size content C m The corresponding graded aggregate content coefficient ratio;
in step 505, the parameters are substituted into the above formula, and the following formula can be obtained by mass conservation:
s·h·t·Fet[(A 1 +A 2 +…)V 1 +(B 1 +B 2 +…)V 2 +…]＝Q·M l
wherein, l is a positive integer,fet represents the content of the aggregate grading interval which is required to be the same as that in the asphalt concrete formula in each bin, and the overlapped aggregate grading content in each bin is overlapped;
step 506, calculate all V's that satisfy the equation n Solutions, and selecting a set of most appropriate solutions.
Referring to fig. 6, which shows a flow chart of aggregate conveyor speed control, for conveyor speed control, the main steps include:
according to the communication protocol of the PLC controller and the frequency converter, the working state of the system is indicated by the digital output quantity of the PLC controller, and the frequency converter is controlled to work by a program;
the main circuit of the frequency converter provides voltage and frequency regulating power supply for the asynchronous motor, and various speed control of the motor is changed according to various frequency changes of the frequency converter, wherein the various speed control is realized by changing the power supply frequency of the cage type asynchronous motor, namely changing the synchronous revolution of the motor;
the motor is connected with the conveyor belt shaft through a coupler, so that the conveyor belt can realize various speed changes such as forward rotation, reverse rotation, starting, stopping, acceleration, deceleration and the like.
Specifically, when the asynchronous motor is operated by the frequency converter in a speed regulation way, a main circuit of the frequency converter generally provides a voltage and frequency regulation power supply for the asynchronous motor, and in an AC-DC-AC frequency conversion speed regulation system, an uncontrollable rectifier is adopted for rectification, and a PWM inverter is adopted for voltage regulation, namely a full-control power switch element which can be controlled to be turned off is adopted.
The speed regulation can be realized by changing the power supply frequency of the cage type asynchronous motor, namely, changing the synchronous revolution of the motor.
The above embodiment is only used for further explaining an on-line detection and anti-overflow control method and system for aggregate gradation of an asphalt mixing plant, but the invention is not limited to the embodiment, and any simple modification, equivalent variation and modification to the above embodiment according to the technical substance of the invention falls within the protection scope of the technical scheme of the invention.
Claims (9)
1. An asphalt mixing plant aggregate grading control system, comprising: the device comprises a plurality of feeding bins, a plurality of aggregate conveyor belts, terminal equipment, a PLC (programmable logic controller), a frequency converter and a plurality of motors; the number of the feeding bins, the aggregate conveyor belts and the motors is the same; an aggregate conveyor belt is arranged right below each feeding bin to convey stacked aggregates subjected to manual loading screening; a camera bellows is fixedly arranged on the guide rail of each aggregate conveyor belt; the camera bellows is internally provided with lighting equipment for adjusting the brightness of light rays in the camera bellows; the top of the camera bellows is provided with an image collector for collecting images of the aggregate to be tested; the terminal equipment is connected with the image collector to receive and process the collected images; the terminal equipment is connected with the PLC to send the speed ratio which needs to be achieved by each aggregate conveyor belt; the PLC is connected with the frequency converter; the frequency converter is connected with all motors; each motor is connected with one aggregate conveyor belt to carry out speed regulation control;
the calculation method of the speed ratio to be achieved by each aggregate conveyor belt comprises the following steps:
the particle size content corresponding to different particle size intervals in each bin is respectively marked as A 1 、A 2 ···A i ，B 1 、B 2 ···B j ，C 1 、C 2 ···C m The width of the bin is denoted as s, the height of the bin from the aggregate conveyor belts is denoted as h, and the speed of each aggregate conveyor belt is denoted as V n In the mixture grading required by the asphalt concrete formulation, the conveying time of the aggregate conveyor belt is marked as t, and the content required by each aggregate grading is marked as M 1 、M 2 ···M l The total mass of the asphalt concrete is Q; wherein n is a positive integer;
according to the aggregate content of the same grading in each bin corresponding to the aggregate content of each grading in the asphalt concrete, overlapping aggregate grading contents in each bin are overlapped to obtain the following formula:
M l ＝k 1 ·A 1 +···+k i ·A i +p 1 ·B 1 +···+p j ·B j +q 1 ·C 1 +···+q m ·C m +···
wherein i, j and m are positive integers; k (k) 1 ···k i Indicating that each bin contains particle size content A i The corresponding graded aggregate content coefficient ratio; p is p 1 ···p j Indicating that each bin contains particle size content B j The corresponding graded aggregate content coefficient ratio; q 1 ···q m Indicating that each bin contains particle size content C m The corresponding graded aggregate content coefficient ratio;
substituting each parameter into the above formula, the following formula can be obtained by mass conservation:
s·h·t·Fet[(A 1 +A 2 +···)V 1 +(B 1 +B 2 +···)V 2 +···]＝Q·M l
wherein, l is a positive integer,fet represents the content of the aggregate grading interval which is required to be the same as that in the asphalt concrete formula in each bin, and the overlapped aggregate grading content in each bin is overlapped;
calculate all V n Solutions, and selecting a set of most appropriate solutions.
2. The asphalt plant aggregate grading control system according to claim 1, wherein the terminal device comprises: the system comprises an image processing module, a geometric feature analysis module, an aggregate granularity distribution result display module and a conveyor belt speed calculation module; the image processing module is used for processing the collected stacked aggregate images; the geometric feature analysis module is used for analyzing the aggregate image processed by the image processing module to obtain the geometric feature of each aggregate particle; the aggregate granularity distribution result display module is used for counting the geometric characteristics obtained by the geometric characteristic analysis module to obtain the grading result of aggregate; the conveyor belt speed calculation module calculates the speed ratio which needs to be achieved by each conveyor belt according to the particle size content of each grade of aggregate particles and the requirement of actual concrete on the proportion of each grade of aggregate particles.
3. An on-line detection method for aggregate gradation of an asphalt mixing plant, based on the aggregate gradation control system of an asphalt mixing plant according to any one of claims 1 to 2, characterized by comprising:
the image collector collects images of the stacking aggregates subjected to manual loading and screening and sends the images to the terminal equipment;
the terminal equipment processes the collected stacked aggregate images;
the terminal equipment performs geometric feature analysis on the processed stacked aggregate image, and calculates geometric features of each aggregate particle in the stacked aggregate image;
and the terminal equipment analyzes and obtains the granularity distribution statistical information of the stacked aggregate according to the geometric characteristics of each aggregate particle in the stacked aggregate image.
4. The on-line detection method for aggregate grading in asphalt mixing plant according to claim 3, wherein the image collector performs image collection of the manually loaded and sieved stacked aggregates, comprising:
setting an image acquisition area; the image acquisition area irradiates to the surface layer of the stacked aggregate in a certain area on the stacked aggregate conveyor belt.
5. The on-line detection method for aggregate gradation of asphalt mixing plant according to claim 3, wherein the terminal device processes the collected stacked aggregate image, comprising:
converting the collected stacked aggregate image into a gray scale image;
carrying out smooth image processing on the image subjected to graying by adopting a median filtering method;
performing threshold segmentation processing on the filtered stacked aggregate image by adopting a Niblack local threshold method based on clustering global threshold improvement, and converting the image into a binary image;
performing iterative morphological erosion operation on the stacked aggregate image subjected to the threshold segmentation treatment to separate particles in contact with each other in the image;
carrying out cavity treatment in the middle of filling particles on the stacked aggregate images subjected to morphological corrosion operation so as to eliminate noise formed by segmentation treatment of surface textures of the aggregate particles;
and (5) performing image calibration processing by adopting a pellet calibration method.
6. The on-line detection method for aggregate gradation of asphalt mixing plant according to claim 5, further comprising, before the image calibration process:
and (3) removing incomplete particles at the boundary, repeatedly identifying the aggregate by adopting a constant pitch for repeatedly shooting the particles, and then removing the particles.
7. The on-line detection method for aggregate grading of asphalt mixing plant according to claim 5, wherein the threshold segmentation processing is performed on the filtered stacked aggregate image by using a Niblack local threshold method based on clustering global threshold improvement, surface aggregate is taken as a research object, and the lower incomplete aggregate is taken as a background, and the method specifically comprises the following steps:
a global threshold T1 of the stacked aggregate image after median filtering is obtained by using a clustering global threshold method;
dividing the whole image into nine subgraphs, and solving a local threshold T2 by using a Niblack algorithm for each subgraph;
and (3) weighting and summing a global threshold T1 obtained by a clustering method and a T2 obtained by a Niblack method to obtain a threshold of each sub-graph: t3=αt1+ (1- α) T2, where α represents a weighting coefficient.
8. The on-line detection method for aggregate grading of asphalt mixing plant according to claim 5, wherein the image calibration processing by adopting the pellet calibration method specifically comprises the following steps:
under the same image acquisition environment, carrying out image acquisition on a plurality of standard pellets with known diameters;
after the pellet image is subjected to image processing, calculating and obtaining a pixel area value of each pellet in the image;
and comparing the real area value of each small sphere with the pixel area value in the image, and taking the average value of the ratio as a calibration coefficient.
9. A control method for aggregate grading and overflow prevention of an asphalt mixing plant, based on the aggregate grading control system of the asphalt mixing plant according to any one of claims 1-2, characterized by comprising:
according to the requirements of actual asphalt concrete on the aggregate particle proportion of each level, the terminal equipment calculates the speed ratio which needs to be achieved by each conveyor belt and sends the speed ratio to the PLC;
the PLC controller sends various required speeds to the frequency converter according to the speed ratio so as to control the frequency converter to work;
the frequency converter provides voltage and frequency regulation power supply for the motor, and the speed of the motor is changed to control the speed of each aggregate conveyor belt.
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