CN111272784B - Method for detecting coal and coal gangue - Google Patents

Method for detecting coal and coal gangue Download PDF

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CN111272784B
CN111272784B CN202010246951.2A CN202010246951A CN111272784B CN 111272784 B CN111272784 B CN 111272784B CN 202010246951 A CN202010246951 A CN 202010246951A CN 111272784 B CN111272784 B CN 111272784B
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昝鑫
刘天宝
吴泽鹏
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Xian Jiaotong University
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Abstract

The invention provides a coal gangue detection method, which uses an X-ray emitter, a receiver and a depth camera to process a depth map obtained by the depth camera to obtain thickness information of sub-areas in a visual range of the depth camera, selects a plurality of points, performs curve fitting on the thickness information and the intensity information of X-rays obtained by the X-ray receiver by using a least square method, and distinguishes whether a target object is a coal briquette or gangue according to a fitting result. According to the method, the coal gangue is distinguished by means of the X-ray penetration characteristics of the coal gangue, the penetration characteristics of the coal gangue and the thickness of the coal gangue have a certain functional relationship, a depth camera is adopted to obtain local thickness information of the coal gangue, and then the thickness information of a plurality of target points and the penetration information of the X-ray at corresponding positions of the target points are combined to solve the energy attenuation coefficient of the target to distinguish the coal or the coal gangue.

Description

Method for detecting coal and coal gangue
Technical Field
The invention relates to the field of ore detection, in particular to a method for detecting coal and coal gangue.
Background
The coal gangue is a solid waste discharged in the coal production and processing process, and is a rock with lower carbon content and harder than coal. In order to improve the quality of coal, it is very important to distinguish coal from gangue well. The conventional distinguishing method is a visual distinguishing method, which distinguishes the coal and the gangue according to different surface textures, but is easily affected by surface dust and light, so that the distinguishing method has the problem of wrong distinguishing. The density is extracted by the acquired volume and mass, but a plurality of depth cameras are needed in the process of acquiring the volume, the calculation is complex, and the dead angle is large. Some methods adopt an X-ray detection device and an RGB camera, and calculate the attenuation coefficient by obtaining the overall height through the RGB camera, but the method has great limitation on irregular coal gangue blocks and is easy to obtain wrong thickness information.
Disclosure of Invention
Aiming at the problems that the existing coal and gangue distinguishing method is easy to generate errors and the distinguishing method is complex, the invention provides a coal and gangue detection method, which realizes the rapid and accurate distinguishing of coal and gangue.
The invention is realized by the following technical scheme:
a method for detecting coal and coal gangue comprises the following steps:
step 1, determining a world coordinate system, an X-ray detection device coordinate system and a depth camera coordinate system, wherein the Z axis of the X-ray detection device is parallel to the Z axis of the world coordinate system, and the optical axis of the depth camera is parallel to the Y axis of the world coordinate system;
step 2, obtaining a conversion relation between an image coordinate system of the X-ray receiving image and a coordinate system of the X-ray detection device, and obtaining the conversion relation between the coordinate system of the X-ray detection device and the coordinate system of the depth camera according to the conversion relation and the parameters of the depth camera;
step 3, converting the depth map obtained by the depth camera into the coordinate system of the X-ray detection device according to the position conversion relation between the coordinate system of the X-ray detection device and the coordinate system of the depth camera, and then obtaining three-dimensional points of the depth map of the X-ray detection device in the XY plane detection range to form a point set;
step 4, dividing the point set into a plurality of subsets along the X axis, and acquiring the position range of thickness information which can be obtained by the depth camera in each subset;
step 5, constraining all three-dimensional points in the subset to the middle value of the X coordinate of the area corresponding to the subset, calculating a sampling point set of a two-dimensional profile in the visible range of the depth camera, and acquiring the thickness of the target object in the Z-axis direction at the middle value of the X coordinate of the subset area;
step 6, obtaining X-ray intensity information corresponding to each point on an XY plane of a coordinate system of the X-ray detection device according to the X-ray receiving diagram;
and 7, randomly selecting k coordinate points in the coordinate range in which the depth camera can detect the thickness, obtaining thickness information and X-ray intensity information, calculating the intensity attenuation coefficient of a target, and judging the coal blocks and the coal gangue according to the attenuation coefficient.
Preferably, in step 1, the XY plane of the world coordinate system is the plane of the conveyor belt, the running direction of the conveyor belt is the direction of the X axis, and the direction of the Z axis is perpendicular to the plane of the conveyor belt and upward.
Preferably, the conversion relationship between the image coordinate system of the X-ray receiving map and the X-ray detecting device coordinate system in step 1 is as follows:
Figure BDA0002434210590000021
Figure BDA0002434210590000022
wherein, PxFor a point in the coordinate system of the X-ray detector, pxIs PxProjection on an X-ray reception map, kx，kyAre the scaling factors in the X-direction and Y-direction, respectively.
Preferably, the position conversion relationship between the X-ray detection device coordinate system and the depth camera coordinate system in step 2 is as follows:
Px＝Pd+T
wherein P is a point in the world, PxIs the position coordinate of P in the coordinate system of the X-ray detection device, PdIs PxPosition coordinates in the depth camera coordinate system, T is the translation vector between the coordinate systems.
Preferably, the method for acquiring the point set in step 3 specifically includes:
converting a depth map obtained by a depth camera into a three-dimensional point cloud map, converting the three-dimensional point cloud map into a coordinate system of an X-ray detection device, eliminating three-dimensional points outside an X-ray detection range and close to a conveyor belt plane, and reserving the remaining three-dimensional points to form a point set.
Preferably, the thickness information in step 4 is acquired by the following method:
at each subset
Figure BDA0002434210590000031
Obtaining
Figure BDA0002434210590000032
And
Figure BDA0002434210590000033
y coordinate of
Figure BDA0002434210590000034
And
Figure BDA0002434210590000035
the maximum range of the thickness information on the Y axis is obtained
Figure BDA0002434210590000036
Wherein the content of the first and second substances,
Figure BDA0002434210590000037
and
Figure BDA0002434210590000038
the points where the Z coordinate is the largest and smallest,
Figure BDA0002434210590000039
and
Figure BDA00024342105900000310
are respectively as
Figure BDA00024342105900000311
And
Figure BDA00024342105900000312
y coordinate value of (a).
Preferably, the method in step 5 specifically comprises the following steps:
firstly, the following components are mixed
Figure BDA00024342105900000313
All points in (2i-1) X are constrained to X coordinatesmax(2t) in the column, simultaneously, taking unit centimeters as intervals on the Z axis, and solving the coordinate value of Y of each point at each unit centimeter on the Z axis by a linear interpolation method to obtain a sampling point set of the two-dimensional section;
then, at each
Figure BDA00024342105900000314
In the Y-axis, a sample interval is givenIf not, the value of the Y coordinate can be 0 from small to large, and Y can be1 i,y2 i…yn iWherein
Figure BDA00024342105900000315
For any one
Figure BDA00024342105900000316
Counting that Y coordinate in the restrained YZ plane is less than Yj iThe number of points of (2) is a coordinate value ((2i-1) x) on the XY planemax/(2t),yj i) The thickness of the spot, i.e. the thickness of the target at the spot location.
Preferably, the method for obtaining the X-ray intensity information in step 6 is as follows:
let the initial intensity of the X-ray be X0Intensity X of the radiation after penetrating the target with thickness hTIs composed of
XT＝X0e-uh
Wherein u has different values according to different attributes of the object;
the brightness information in the X-ray detection map is proportional to the intensity of the X-rays received by the X-ray detection device, and the coefficient is KrWhen the pixel value of the X-ray receiving image at the position with the pixel coordinates of (a, b) is represented by X (a, b), the coordinates in the coordinate system of the X-ray detecting device corresponding to the pixel coordinates are obtained through the conversion relation between the image coordinate system of the X-ray receiving image and the coordinate system of the X-ray detecting device, and the X-ray intensity is KrX(a,b)。
Preferably, the method for judging the coal briquettes and the coal gangue in the step 7 is as follows:
the energy attenuation coefficient of the target is calculated by adopting a least square method,
Figure BDA0002434210590000041
wherein X0Is the initial intensity of the X-ray, XTIs attenuated by an X-ray detectorU represents the attenuation coefficient of the object, and h represents the thickness of the object;
the attenuation function is written as follows
Hr＝b
Wherein
Figure BDA0002434210590000042
b＝[xs1 … xsk]T，thiThickness value, xs, representing the ith pointiRepresents the attenuated X-ray intensity value of the ith point,
Figure BDA0002434210590000043
wherein H and b are both known amounts and are readily available
r＝(HTH)-1HTb
And the fitting result u is the second element of the r vector, the difference between the value of u obtained by fitting and the actually measured value of u when the target is coal or coal gangue is calculated, an absolute value is obtained, and the resolution result with the smaller absolute value is taken as the target.
Compared with the prior art, the invention has the following beneficial technical effects:
according to the coal gangue detection method provided by the invention, the X-ray emitter, the receiver and the depth camera are used, the energy attenuation coefficient of the target is obtained through the thickness information of partial points and the energy information of the X-ray, the calculated amount is small, the influence of dead angles is avoided, the least square method is adopted for fitting parameters for a plurality of random points, and the reliability is high. Compared with a method using surface features, the method has higher robustness to dust interference, and because the penetration characteristics of different positions of coal or gangue under X-rays are the same, a depth camera side-view method is used for calculating the coordinate relation of a sensor to obtain a region capable of accurately obtaining the thickness, and the penetration characteristics are calculated by randomly sampling points without being influenced by the environment on the surface characteristics of coal blocks or coal gangue. Compared with a method for acquiring the height by using an RGB camera, the method can deal with various irregular coal or gangue blocks. Compared with a method for modeling the volume of the stone block, the method is simple to use and is not influenced by dead angles.
Drawings
FIG. 1 is a diagram of a coordinate system of the present invention;
FIG. 2 is a block diagram of the present invention;
FIG. 3 is a schematic diagram of a point cloud of the present invention prior to constraint;
FIG. 4 is a schematic diagram of a point cloud after the inventive arrangements;
Detailed Description
The present invention will now be described in further detail with reference to the attached drawings, which are illustrative, but not limiting, of the present invention.
A method for detecting coal and coal gangue comprises the following steps:
step 1, determining a world coordinate system and an X-ray detection device coordinate system, and acquiring a conversion relation between an image coordinate system of an X-ray receiving image and the X-ray detection device coordinate system.
Firstly, determining a world coordinate system, taking a plane where a conveyor belt is located as a plane formed by XY axes, taking the running direction of the conveyor belt as the direction of an X axis, and unfolding a right-hand rectangular coordinate system, wherein the direction of a Z axis is vertical to the plane of the conveyor belt and upwards.
And enabling the X-ray detection device to emit X-rays along the opposite direction of the Z axis, wherein an XY plane in a coordinate system of the X-ray detection device is superposed with an XY plane in a world coordinate system, the directions of the X axis and the Y axis are the same as the world coordinate system, the direction of the Z axis is also vertical to the conveying belt, and the origin is the origin of the X-ray receiving diagram.
Specifically, the point on the X-ray receiving diagram is the orthographic projection of the point in the coordinate system of the X-ray detection device, and P isxIs a point in the coordinate system of the X-ray detection device whose projection on the X-ray reception map is pxWhich is a projective transformation on the OXY plane, with PxIs independent of the Z coordinate of (a).
Let Px＝[P1 P2 P3]T，PxParallel projection on the OXY plane along the Z axis is
Figure BDA0002434210590000061
Figure BDA0002434210590000062
Let p bex＝[p1 p2]TThen the conversion relationship is as follows:
Figure BDA0002434210590000063
wherein the content of the first and second substances,
Figure BDA0002434210590000064
kx，kyare the scaling factors in the X-direction and Y-direction, respectively.
Two small rods with different widths and suitable heights are vertically placed at different positions on the conveyor belt, and the difference between the X coordinate and the Y coordinate of the two small rods is ensured. Measuring the distance c between two small bars along the X-axisxAnd a distance c along the Y axisy。
Taking n X-ray receiving graphs with two short rods, wherein each graph has two obvious point blocks, and each point block corresponds to one short rod. Averaging the X coordinate and the Y coordinate of each point block to obtain the position of the short bar, wherein the horizontal coordinate difference and the vertical coordinate difference of two points of the ith image are respectively
Figure BDA0002434210590000071
And
Figure BDA0002434210590000072
k can be calculated from thisxAnd kyAre respectively
Figure BDA0002434210590000073
Figure BDA0002434210590000074
And 2, placing the depth camera according to the requirement to obtain the position conversion relation between the coordinate system of the X-ray detection device and the coordinate system of the depth camera.
The optical axis direction of the depth camera is the Y-axis direction of the world coordinate system, and the directions of the X-axis and the Z-axis in the depth camera coordinate system are the same as the world coordinate system.
Specifically, as shown in fig. 1, the X-ray detection device coordinate system is omitted, where xyz represents the world coordinate system, O 'X' Y 'Z' is the depth camera coordinate system, and S is the phase plane of the depth camera, which is parallel to the OXZ plane. The coordinate system of the X-ray detection device has no rotational relation with the world coordinate system, and only shifts on an X-axis and a Y-axis exist.
Let P be a point in the world, PxFor its position coordinates in the X-ray detector coordinate system, PdIs its position coordinate in the depth camera coordinate system. Then P isxAnd PdConversion relationship between them
Px＝Pd+T (4)
Wherein T ═ T1 t2 t3]TIn the three-dimensional coordinate system, only one point is needed to solve T, and in order to improve the accuracy of the result, the average value of multiple points is adopted.
The intrinsic parameters of the depth camera are generally known, and the three-dimensional coordinates of points in the depth map in the depth camera coordinate system can be recovered from the intrinsic parameters of the depth camera and the depth information.
Let dxAnd dyThe sampling distances from the phase plane to the image pixel points are respectively the distances between two adjacent pixel points on the X axis and the Y axis of the image plane. The phase plane is parallel to the OXZ plane in this example, so it is set to dxAnd dz. Order (u)0,v0) Is the coordinate of the principal point, f is the focal length of the camera, kdIs the ratio of the pixel value in the depth map to the actual depth.
If PdRepresents a projected point of a point P in the camera coordinate system on its phase plane with Z coordinate f. Its corresponding point in the depth map is pdBy MdRepresents PdCoordinates in the camera coordinate system, Md＝[X Z f]T. By mdRepresents pdOn the depth mapPosition coordinates, md＝[x z]T。
Figure BDA0002434210590000081
Figure BDA0002434210590000082
Is mdA homogeneous form of (a). For convenience of calculation, use
Figure BDA0002434210590000083
To represent PdThe coordinate information of (2).
Figure BDA0002434210590000084
Figure BDA0002434210590000085
The depth map is denoted by D, D (p)d) Represents a point pdThe depth of the point P and the value of its Y coordinate are PY＝kdD(pd) Abscissa P of point P in the camera coordinate systemXAnd ordinate PZAre respectively as
PX＝XPY/f (6)
PZ＝ZPY/f (7)
And acquiring n pairs of an X-ray detection image and a depth image which simultaneously have two small rods, and taking the mean value of the X coordinate and the Y coordinate of each point block for the X-ray detection image so as to acquire the position coordinate of the short rod in the X-ray detection image. And then converted into the X-ray detection apparatus coordinate system by the conversion relation (formula 1) of the image coordinate system of the X-ray reception map and the X-ray detection apparatus coordinate system.
And (4) setting the position coordinate of each short rod as the highest point position, and setting the Z coordinate of each short rod in the coordinate system of the X-ray detection device as the height of the short rod. By XW＝[xwx xwy xwz]TIndicating the position coordinates of the small bar in the X-ray detection device.
For the depth map, two parallel rectangle-like areas exist in the map, for each rectangle-like block of each depth map, each point in the rectangle-like block is firstly converted into a three-dimensional point in a camera coordinate system through equations (5), (6) and (7), and then the X coordinate, the Y coordinate and the Z coordinate of all points in the area are respectively averaged to obtain the position coordinate of the middle point of the small bar in the camera coordinate system. Multiplying the Z coordinate by 2 to obtain the position coordinate of the highest point, and using DW＝[dwx dwy dwz]TRepresenting the position coordinates of the highest point of the small stick in the depth camera coordinate system.
After the above operations are successively performed on n pairs of images, 2n pairs of points can be obtained, which can be distinguished by the difference in the positions of two small bars on the same image, and then T can be calculated by the following formula (8)
Figure BDA0002434210590000091
And 3, converting the depth map obtained by the depth camera into a three-dimensional point cloud map in a depth camera coordinate system through the formulas (5), (6) and (7), and then converting the three-dimensional point cloud map into an X-ray detection device coordinate system through the formula (4). According to the size of the X-ray reception map and kxAnd kyObtaining the detection range [ (X) of the X-ray detector on the XY planemin,ymin),(xmax,ymax)]Obviously xmin,＝0，y min0. And removing the three-dimensional points out of the X-ray detection range and close to the plane of the conveyor belt in the conversion process, leaving the remaining points to form a point set Cp。
Step 4, selecting proper interval t on the X axis, and adding CpDivision into xmaxT zones, each zone being CpA subset of
Figure BDA0002434210590000092
Denotes, i ∈ [1, t ∈ >]As shown in fig. 2.
FIG. 3 is
Figure BDA0002434210590000093
The position of the unprocessed point. At each one
Figure BDA0002434210590000094
Finding the point where the Z coordinate is maximum and minimum
Figure BDA0002434210590000095
And
Figure BDA0002434210590000096
step 5, obtaining each subset
Figure BDA0002434210590000097
Wherein the range of positions for the thickness information is obtainable by the depth camera.
In order to obtain the thickness, the highest and lowest points at the same depth must be observed simultaneously, in each subset
Figure BDA0002434210590000098
Obtaining
Figure BDA0002434210590000099
And
Figure BDA00024342105900000910
y coordinate of
Figure BDA00024342105900000911
And
Figure BDA00024342105900000912
the maximum range of the thickness information on the Y-axis can be observed as
Figure BDA00024342105900000913
Let Y be minimum for simplicity
Figure BDA00024342105900000914
I.e. can be obtained on the Y axis
Figure BDA00024342105900000915
A thickness within the range.
Step 6, mixing
Figure BDA0002434210590000101
All points in the region are constrained to the middle of the region's X coordinate range, i.e., the X coordinate is (2i-1) XmaxAnd (2t) the column, and the coordinate value of Y for each point is found by linear interpolation at each unit cm on the Z-axis at intervals of unit cm on the Z-axis, as shown in fig. 4. At each time
Figure BDA0002434210590000102
The X coordinate is fixed, and the Z coordinates have the same unit interval, and actually a sampling point set of a two-dimensional profile within the visible range of a depth camera is obtained, that is, the projection on the XZ plane in fig. 4.
Step 7, at each
Figure BDA0002434210590000103
In the method, a sampling interval is given on the Y axis, the value of the Y coordinate can be 0 from small to large, and Y is1 i,y2 i…yn i. Wherein
Figure BDA0002434210590000104
For any one
Figure BDA0002434210590000105
Counting that Y coordinate in the restrained YZ plane is less than Yj iThe number of points of (2) is a coordinate value ((2i-1) x) on the XY planemax/(2t),yj i) I.e. the thickness of the object at that point along the Z-axis.
And 8, uniformly processing all the areas, so that the thickness of part of points in the visible area of the depth camera can be obtained. And carrying out bilateral filtering on the result to filter out partial singular points.
And 9, acquiring X-ray energy information corresponding to each point on the XY plane of the coordinate system of the X-ray detection device according to the X-ray receiving diagram.
The intensity of the X-rays decays exponentially with the thickness of the object to be penetrated. Let the initial intensity of the X-ray be X0Intensity X of the radiation after penetrating the target with thickness hTIs composed of
XT＝X0e-uh (9)
Wherein u has different values according to different attributes of the object.
The brightness information in the X-ray detection map is proportional to the intensity of the X-rays received by the X-ray detection device, and the coefficient is KrIt is generally known that when a pixel value of an X-ray reception image at a position having pixel coordinates of (a, b) is represented by X (a, b), coordinates in an X-ray detector corresponding thereto can be obtained by equation (1) with X-ray intensity KrX(a,b)。
Step 10, randomly selecting k coordinate points in the coordinate range where the thickness can be detected, and obtaining thickness information th at each coordinate pointmAnd X-ray intensity information xsm，m∈[1,k]. And calculating the energy attenuation coefficient of the target by adopting a least square method. And judging the coal blocks and the coal gangue according to the attenuation coefficient.
Logarithm of formula (9) is obtained
Figure BDA0002434210590000111
The attenuation function is written as follows
Hr＝b
Wherein
Figure BDA0002434210590000112
b＝[xs1 … xsk]T，thiThickness value, xs, representing the ith pointiRepresenting the attenuated X-ray intensity value at the ith point.
Figure BDA0002434210590000113
Wherein H and b are both known amounts and are readily available
r＝(HTH)-1HTb
And the fitting result u is the second element of the r vector, the difference between the value of u obtained by fitting and the actually measured value of u when the target is coal or gangue is calculated, an absolute value is obtained, and the resolution result with the smaller absolute value as the target is obtained.
According to the coal gangue detection method provided by the invention, the depth camera is fixed according to the requirement, and the position relation between the depth camera coordinate system and the X-ray detection device coordinate system is obtained. And processing the depth map obtained by the depth camera to obtain the thickness information of the sub-area in the visual range of the depth camera. And selecting a plurality of points, performing curve fitting on the thickness information of the points and the strength information of the X-ray obtained by using the X-ray receiver by using a least square method, and distinguishing whether the target object is a coal block or gangue according to a fitting result. The method carries out resolution on the coal gangue by means of the X-ray penetration characteristic of the coal gangue. The penetration characteristic of the coal gangue and the thickness of the coal gangue have a certain functional relationship, a depth camera is adopted to obtain the local thickness information of the coal gangue, and then the thickness information of a plurality of target points and the penetration information of X-rays at corresponding positions are combined to solve the energy attenuation coefficient of a target to distinguish the coal or the coal gangue.
The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.

Claims (6)

1. A method for detecting coal and coal gangue is characterized by comprising the following steps:
step 1, determining a world coordinate system, an X-ray detection device coordinate system and a depth camera coordinate system, wherein the Z axis of the X-ray detection device is parallel to the Z axis of the world coordinate system, and the optical axis of the depth camera is parallel to the Y axis of the world coordinate system;
step 2, obtaining a conversion relation between an image coordinate system of the X-ray receiving image and a coordinate system of the X-ray detection device, and obtaining the conversion relation between the coordinate system of the X-ray detection device and the coordinate system of the depth camera according to the conversion relation and the parameters of the depth camera;
step 3, converting the depth map obtained by the depth camera into the coordinate system of the X-ray detection device according to the position conversion relation between the coordinate system of the X-ray detection device and the coordinate system of the depth camera, then obtaining three-dimensional points of the depth map of the X-ray detection device in the XY plane detection range, and forming a point set Cp；
Step 4, dividing the point set into a plurality of subsets along the X axis, and acquiring the position range of thickness information which can be obtained by the depth camera in each subset;
step 5, subset
Figure FDA0002999984200000011
All the three-dimensional points are constrained to the middle value of the X coordinate of the area corresponding to the subset, a sampling point set of a two-dimensional section in the visible range of the depth camera is calculated, and the thickness of the target object in the Z-axis direction at the middle value of the X coordinate of the subset area is obtained;
will be provided with
Figure FDA0002999984200000012
All points in (2i-1) X are constrained to X coordinatesmax(2t) in the column, simultaneously, taking unit centimeters as intervals on the Z axis, and solving the coordinate value of Y of each point at each unit centimeter on the Z axis by a linear interpolation method to obtain a sampling point set of the two-dimensional section;
then, at each
Figure FDA0002999984200000013
In the method, a sampling interval is given on the Y axis, the value of the Y coordinate can be 0 from small to large, and Y is1 i，y2 i…yn iWherein
Figure FDA0002999984200000014
For any one yj iAnd counting that the Y coordinate in the constrained YZ plane is smaller than Yj iThe number of points is the coordinate value on the XY planeIs ((2i-1) x)max/(2t)，yj i) The thickness of the target, i.e. the thickness of the target at the point;
uniformly processing all the areas, obtaining the thickness of partial points in the visible area of the depth camera, and performing bilateral filtering on the result to filter out partial singular points;
step 6, obtaining X-ray intensity information corresponding to each point on an XY plane of a coordinate system of the X-ray detection device according to the X-ray receiving diagram;
let the initial intensity of the X-ray be X0Intensity X of the radiation after penetrating the target with thickness hTIs composed of
XT＝X0e-uh
Wherein u has different values according to different attributes of the object;
the brightness information in the X-ray detection map is proportional to the intensity of the X-rays received by the X-ray detection device, and the coefficient is KrWhen the pixel value of the X-ray receiving image at the position with the pixel coordinates of (a, b) is represented by X (a, b), the coordinates in the coordinate system of the X-ray detecting device corresponding to the pixel coordinates are obtained through the conversion relation between the image coordinate system of the X-ray receiving image and the coordinate system of the X-ray detecting device, and the X-ray intensity is KrX(a，b)；
Step 7, randomly selecting k coordinate points in the coordinate range where the depth camera can detect the thickness, obtaining thickness information and X-ray intensity information, calculating the intensity attenuation coefficient of a target, and judging the coal blocks and the coal gangue according to the attenuation coefficient;
the energy attenuation coefficient of the target is calculated by adopting a least square method,
Figure FDA0002999984200000021
wherein X0Is the initial intensity of the X-ray, XTIs the attenuated X-ray intensity obtained by the X-ray detection device, u represents the attenuation coefficient of the target object, h represents the thickness of the target object;
the attenuation function is written as follows
Hr＝b
Wherein
Figure FDA0002999984200000031
b＝[xs1 … xsk]T，thiThickness value, xs, representing the ith pointiRepresents the attenuated X-ray intensity value of the ith point,
Figure FDA0002999984200000032
wherein H and b are both known amounts and are readily available
r＝(HTH)-1HTb
And the fitting result u is the second element of the r vector, the difference between the value of u obtained by fitting and the actually measured value of u when the target is coal or coal gangue is calculated, an absolute value is obtained, and the resolution result with the smaller absolute value is taken as the target.
2. The coal and coal refuse detection method as set forth in claim 1, wherein the XY plane of the world coordinate system in step 1 is the plane of the conveyor belt, and the direction of the X axis is the running direction of the conveyor belt, and the direction of the Z axis is perpendicular to the plane of the conveyor belt and upward.
3. The coal and coal refuse detection method according to claim 1, wherein the conversion relationship between the image coordinate system of the X-ray reception map and the coordinate system of the X-ray detection device in step 1 is as follows:
Figure FDA0002999984200000033
Figure FDA0002999984200000034
wherein, PxFor a point in the coordinate system of the X-ray detector, pxIs PxProjection on X-ray reception map，kx，kyAre the scaling factors in the X-direction and Y-direction, respectively.
4. The coal and coal refuse detection method according to claim 3, wherein the position conversion relationship between the X-ray detection device coordinate system and the depth camera coordinate system in step 2 is as follows:
Px＝Pd+T
wherein P is a point in the world coordinate system, PxIs the position coordinate of P in the coordinate system of the X-ray detection device, PdIs PxPosition coordinates in the depth camera coordinate system, T is the translation vector between the coordinate systems.
5. The method for detecting coal and coal gangue as claimed in claim 4, wherein the method for obtaining the point set in step 3 is as follows:
converting a depth map obtained by a depth camera into a three-dimensional point cloud map, converting the three-dimensional point cloud map into a coordinate system of an X-ray detection device, eliminating three-dimensional points outside an X-ray detection range and close to a conveyor belt plane, and reserving the remaining three-dimensional points to form a point set.
6. The method for detecting coal and coal gangue as claimed in claim 5, wherein the method for obtaining the thickness information in step 4 is as follows:
at each subset
Figure FDA0002999984200000041
Obtaining
Figure FDA0002999984200000042
And
Figure FDA0002999984200000043
y coordinate of
Figure FDA0002999984200000044
And
Figure FDA0002999984200000045
the maximum range of the thickness information on the Y axis is obtained
Figure FDA0002999984200000046
Wherein the content of the first and second substances,
Figure FDA0002999984200000047
and
Figure FDA0002999984200000048
the points where the Z coordinate is the largest and smallest,
Figure FDA0002999984200000049
and
Figure FDA00029999842000000410
are respectively as
Figure FDA00029999842000000411
And
Figure FDA00029999842000000412
y coordinate value of (a).
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102915559A (en) * 2012-08-22 2013-02-06 北京航空航天大学 Real-time transparent object GPU (graphic processing unit) parallel generating method based on three-dimensional point cloud
CN109118582A (en) * 2018-09-19 2019-01-01 东北大学 A kind of commodity three-dimensional reconstruction system and method for reconstructing
CN110811654A (en) * 2019-11-12 2020-02-21 飞瑞医疗器械(嘉兴)有限公司 X-ray exposure control system and control method thereof

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102915559A (en) * 2012-08-22 2013-02-06 北京航空航天大学 Real-time transparent object GPU (graphic processing unit) parallel generating method based on three-dimensional point cloud
CN109118582A (en) * 2018-09-19 2019-01-01 东北大学 A kind of commodity three-dimensional reconstruction system and method for reconstructing
CN110811654A (en) * 2019-11-12 2020-02-21 飞瑞医疗器械(嘉兴)有限公司 X-ray exposure control system and control method thereof

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
A Pareto-based genetic algorithm for multi-objective scheduling of automated manufacturing systems;Xin Zan等;《Advances in Mechanical Engineering》;20200106;第1-15页 *
双进双出磨煤机出粉量的一种新估计方法;段松涛等;《Proceedings of the 32nd Chinese Control Conference》;20130731;第4799-4802页 *

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