Speed ​​measurement method, system, electronic equipment and medium based on oblique scanning staggered transformation

Abstract

The present invention provides a speed measurement method, system, electronic device and medium based on oblique scanning staggered transformation. The speed measurement method is used in a speed measurement system; the speed measurement system is used to measure the speed of a target object on a conveyor belt; the speed measurement system includes a linear array camera for collecting images, the linear array camera is fixed above the conveyor belt, and the scanning line of the linear array camera is not perpendicular to the moving direction of the target object; the method includes: obtaining an image of the target object, the image includes multiple lines of pixel data collected in sequence by the linear array camera, and the time interval between any two adjacent lines of pixel data collected by the linear array camera in the multiple lines of pixel data is a preset time length; determining the actual geometric parameter information of the target object and the image geometric parameter information of the target object in the image; determining the moving speed of the target object based at least on the image geometric parameter information of the target object in the image, the actual geometric parameter information of the target object and the preset time length. This method can determine the moving speed of the target object more accurately.

Description

Technical Field

[0001] The present invention relates to the technical field of speed measurement, and more specifically to a speed measurement method, system, electronic equipment and medium based on oblique scanning and shear transformation. Background Art

[0002] When materials are placed flat on a conveyor belt and move, it is often necessary to measure the speed of the materials or the conveyor belt. The speed measuring equipment is required to be installed vertically to the measuring plane and at a certain distance to achieve non-contact speed measurement of the moving plane.

[0003] In the related art, a laser Doppler velocimeter is usually used to measure the speed of a moving plane (i.e., a conveyor belt). The laser Doppler velocimeter can utilize the Doppler effect to emit a laser beam to illuminate the moving plane or the material on the moving plane, receive the reflected laser signal, and analyze the change in the frequency of the laser signal to calculate the speed of the moving plane. However, this speed measurement method is greatly affected by the surface of the moving plane or the material. When the laser Doppler velocimeter measures the speed of the moving plane, if the surface reflectivity is low or the surface is rough, the intensity of the laser signal received by the laser Doppler velocimeter will be weakened, which may increase the measurement error or even make it impossible to perform effective speed measurement.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] The present invention is proposed in view of the above problems. According to one aspect of the present invention, a speed measurement method based on oblique scanning staggered transformation is provided, which is used in a speed measurement system; the speed measurement system is used to measure the speed of a target object on a conveyor belt; the speed measurement system includes a linear array camera for collecting images, the linear array camera is fixed above the conveyor belt, and the scanning line of the linear array camera is not perpendicular to the moving direction of the target object; The method comprises: Acquire an image of the target object, the image comprising a plurality of lines of pixel data sequentially acquired by the line array camera, wherein the time interval between any two adjacent lines of pixel data acquired by the line array camera in the plurality of lines of pixel data is a preset time length; Determine actual geometric parameter information of the target object and image geometric parameter information of the target object in the image; The moving speed of the target object is determined based at least on the image geometric parameter information of the target object in the image, the actual geometric parameter information of the target object and the preset time length.

[0006] Exemplarily, determining the moving speed of the target object based at least on the image geometric parameter information of the target object in the image, the actual geometric parameter information of the target object, and the preset time duration includes: Determine a transformation matrix between the spatial coordinate system and the image coordinate system based on the image geometric parameter information, the actual geometric parameter information, and a coordinate transformation relationship between the spatial coordinate system where the target object is located and the image coordinate system where the image is located, wherein the transformation matrix includes a plurality of elements, and a first element of the plurality of elements is positively correlated with a speed of the target object; The moving speed of the target object is determined based on the ratio of the first element in the transformation matrix to the preset time length.

[0007] Exemplarily, the target object is a speed measuring target, and the speed measuring target includes a plurality of target points; The determining the actual geometric parameter information of the target object and the image geometric parameter information of the target object in the image includes: determining the image coordinates of each target point of the plurality of target points in the image; determining the spatial coordinates of each target point among the plurality of target points; The number of target points in the plurality of target points is greater than or equal to two; the origin of the spatial coordinate system coincides with the origin of the image coordinate system; the actual geometric parameter information includes the spatial coordinates of each target point in the plurality of target points, and the image geometric parameter information includes the image coordinates of each target point in the image; The determining of the transformation matrix between the spatial coordinate system and the image coordinate system based on the image geometric parameter information, the actual geometric parameter information, and the coordinate transformation relationship between the spatial coordinate system where the target object is located and the image coordinate system where the image is located comprises: A transformation matrix is ​​determined based on the image coordinates and the space coordinates of each target point in the plurality of target points and the coordinate transformation relationship.

[0008] Exemplarily, determining the transformation matrix based on the image coordinates and the spatial coordinates of each target point in the multiple target points and the coordinate transformation relationship includes: determining the transformation matrix by the following formula:

[0009]

[0010]

[0011] in, is the transformation matrix T In vector form, , ; represents the abscissa of each of the plurality of target points in the spatial coordinates, represents the ordinate in the spatial coordinates of each of the plurality of target points, represents the abscissa of each of the plurality of target points in the image coordinates, The vertical coordinate of each of the plurality of target points in the image coordinates is represented.

[0012] Exemplarily, the target object is a round object, the round object is laid flat on the conveyor belt, and the radius of the round object is a preset radius; The determining of the actual geometric parameter information of the target object and the image geometric parameter information of the target object in the image includes: Determine the major axis radius, minor axis radius and axis inclination angle of the target object in the image; The actual geometric parameter information is the radius of the circular object, and the image geometric parameter information includes the major axis radius, minor axis radius and axis inclination angle of the target object in the image; The determining of the transformation matrix between the spatial coordinate system and the image coordinate system based on the image geometric parameter information, the actual geometric parameter information, and the coordinate transformation relationship between the spatial coordinate system where the target object is located and the image coordinate system where the image is located comprises: A transformation matrix is ​​determined based on the coordinate transformation relationship, the major axis radius, the minor axis radius and the axis inclination angle of the target object in the image, and the preset radius.

[0013] Exemplarily, determining the transformation matrix based on the coordinate transformation relationship, the major axis radius, the minor axis radius and the axis inclination angle of the target object in the image and the preset radius includes: determining the transformation matrix by the following formula:

[0014]

[0015]

[0016] in, T represents the transformation matrix; represents the major axis radius, b represents the minor axis radius, α represents the axis inclination angle, r Indicates the preset radius.

[0017] Exemplarily, determining the moving speed of the target object based on the ratio of the first element in the transformation matrix to the preset time length includes: determining the moving speed by the following formula:

[0018] in, represents the moving speed, represents the first element in the transformation matrix, is the preset duration.

[0019] Exemplarily, an angle between a scanning line direction of the line array camera and a vertical line direction of the speed of the target object is a first preset angle; the scanning line of the line array camera includes a plurality of scanning sampling points, and a distance between any two adjacent sampling points among the plurality of scanning sampling points is a preset distance; after determining the moving speed of the target object, the method further includes: Determine the error of the moving speed based on the first preset angle, the preset distance and the transformation matrix; When the error is less than or equal to the error threshold, determining that the moving speed is reliable; The second element in the transformation matrix is ​​negatively correlated with the sine of the first preset angle and the preset distance, and the third element in the transformation matrix is ​​positively correlated with the cosine of the first preset angle and the preset distance.

[0020] Exemplarily, the angle between the scanning line direction of the line array camera and the vertical line direction of the speed of the target object is a first preset angle; the scanning line of the line array camera includes a plurality of scanning sampling points, and the interval between any two adjacent sampling points in the plurality of scanning sampling points is a preset interval; the target object is an object with a straight edge; The determining of the actual geometric parameter information of the target object and the image geometric parameter information of the target object in the image includes: determining an actual angle of the straight edge and an image angle of the straight edge in the image; Wherein, the actual geometric parameter information is the actual angle, and the image geometric parameter information is the image angle; The determining the moving speed of the target object based at least on the image geometric parameter information of the target object in the image, the actual geometric parameter information of the target object and the preset time duration includes: The moving speed is determined based on the actual angle, the image angle, the preset duration, the first preset angle, and the preset distance.

[0021] Exemplarily, determining the moving speed based on the actual angle, the image angle, the preset duration, the first preset angle, and the preset interval includes: determining the moving speed by the following formula:

[0022] in, is the moving speed, is the first preset angle, is the actual angle, is the image angle, is the preset duration, is the preset spacing.

[0023] Exemplarily, the sum of the tangent value of the first preset angle and the tangent value of the actual angle is not zero.

[0024] Exemplarily, the preset distance is within a target distance range.

[0025] Exemplarily, the preset duration is within a target duration range.

[0026] According to another aspect of the present invention, there is provided a speed measurement system for measuring the speed of a target object on a conveyor belt; the speed measurement system comprises a controller and a linear array camera for acquiring images, the linear array camera is fixed above the conveyor belt, and the scanning line of the linear array camera is not perpendicular to the moving direction of the target object; the controller is used to implement the above method.

[0027] According to another aspect of the present invention, there is provided an electronic device, including a processor and a memory, wherein a computer program is stored in the memory, and the processor is used to execute the computer program to implement the above method.

[0028] According to another aspect of the present invention, a computer-readable storage medium is provided, storing a computer program / instruction, and the computer program / instruction implements the above method when executed by a processor.

[0029] The above technical solution can use the image geometric parameter information of the target object in the image captured by the linear array camera and the actual geometric parameter information of the target object to more accurately determine the moving speed of the target object. This speed measurement method can be used to measure the speed of any moving target object on a plane (such as a speed measurement target, an object with an edge line, or an object with a standard geometric shape on the surface). At the same time, due to the strong image stability, the solution is not easily affected by the difference in reflectivity and roughness of the target surface, ensuring the reliability of the speed measurement results. In addition, the image information has strong robustness and can be widely used in non-contact speed measurement of materials transported on production lines such as printing, textiles, and plates and strips.

[0030] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The above and other purposes, features and advantages of the present invention will become more apparent by describing the embodiments of the present invention in more detail in conjunction with the accompanying drawings. The accompanying drawings are used to provide a further understanding of the embodiments of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings, the same reference numerals generally represent the same components or steps.

[0032] Figure 1 A schematic flow chart of a speed measurement method according to an embodiment of the present invention is shown; Figure 2 A schematic diagram showing the transformation relationship between a space coordinate system and an image coordinate system according to an embodiment of the present invention is shown; Figure 3 A schematic diagram showing the transformation relationship between the space coordinate system and the image coordinate system when the target object is a speed measurement target according to one embodiment of the present invention; Figure 4 A schematic diagram showing the transformation relationship between the space coordinate system and the image coordinate system when the target object is a round object according to one embodiment of the present invention; Figure 5 A schematic diagram showing the transformation relationship between the space coordinate system and the image coordinate system when the target object is an object with a straight edge according to an embodiment of the present invention; Figure 6 A schematic block diagram of an electronic device according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the present invention more obvious, the exemplary embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments of the present invention, and it should be understood that the present invention is not limited to the exemplary embodiments described herein. Based on the embodiments of the present invention described in the present invention, all other embodiments obtained by those skilled in the art without creative work should fall within the protection scope of the present invention.

[0034] As mentioned above, the speed measurement method of the laser Doppler velocimeter commonly used in the related art is greatly affected by the moving plane or the surface of the material, and the accuracy of the speed measurement result is low. In some technologies, it is considered to adopt the method of continuous shooting of the array camera to achieve non-contact speed measurement by calculating the translation amount of the target between image frames, but the algorithm of this speed measurement method is relatively complex. In view of this, the present invention provides a speed measurement method, system, electronic device and medium based on oblique scanning shear transformation. The method is simple to operate and can quickly and accurately measure the moving speed of the material (i.e., the target item hereinafter) on the conveyor belt.

[0035] According to one aspect of an embodiment of the present invention, a speed measurement method based on oblique scanning shear transformation is provided, and the method is used in a speed measurement system; the speed measurement system is used to measure the speed of target items on a conveyor belt; the speed measurement system includes a linear array camera for capturing images, and the linear array camera is fixed above the conveyor belt.

[0036] In this paper, the scanning line of the line scan camera is not perpendicular to the moving direction of the target object.

[0037] Figure 1 FIG. 2 is a schematic flow chart of a speed measurement method according to an embodiment of the present invention. Figure 1 As shown, the method may include the following steps S110, S120 and S130.

[0038] In step S110, an image of the target object is acquired, the image including multiple lines of pixel data sequentially acquired by the line array camera, and the time interval between any two adjacent lines of pixel data acquired by the line array camera in the multiple lines of pixel data is a preset time length.

[0039] It can be understood that the target object moves with the conveyor belt, and the moving speed of the target object is the speed of the conveyor belt. When the target object passes under the linear array camera, the linear array camera can continuously scan multiple lines of pixel data during the movement of the target object on the conveyor belt, thereby forming an image of the target object. Those skilled in the art can understand the principle of the linear array camera collecting the image of the target object, which will not be described in detail.

[0040] In step S120, actual geometric parameter information of the target object and image geometric parameter information of the target object in the image are determined.

[0041] After obtaining the image of the target object, the actual geometric parameter information of the target object and the image geometric parameter information of the target object in the image can be determined first. The actual geometric parameter information is used to represent the actual parameter information of the target object, and the type of the actual geometric parameter information may include but is not limited to the position of multiple feature points on the target object (when the target object is a speed measurement target, the feature point may be a target point) in the spatial coordinate system, the real edge angle of the target object (such as the actual angle below), and the shape parameter of the target object (for example, when the target object is circular, the diameter of the target object). The image geometric parameter information is used to represent the parameter information of the target object in the image, and the type of the image geometric parameter information may include but is not limited to the position of multiple feature points of the target object in the image coordinate system, the edge angle of the target object in the image, and the shape parameter of the target object in the image.

[0042] In step S130, the moving speed of the target object is determined based at least on the image geometric parameter information of the target object in the image, the actual geometric parameter information of the target object, and the preset time.

[0043] The inventors have discovered that when the scanning line of the linear array camera is not perpendicular to the moving direction of the target object, the image captured by the linear array camera will produce a shear distortion phenomenon. Figure 2 The figure shows a schematic diagram of the transformation relationship between the spatial coordinate system and the image coordinate system according to an embodiment of the present invention. The left side of the figure shows a schematic diagram of the target object in the spatial coordinate system, and the right side shows a schematic diagram of the target object in the image coordinate system. Figure 2 As shown, when the geometric shape of the target object collected is a rectangle, due to the shear distortion phenomenon, the geometric shape of the target object in the collected image is a parallelogram. When the geometric shape of the target object collected is a circle, due to the shear distortion phenomenon, the geometric shape of the target object in the collected image is an ellipse.

[0044] In the present invention, it is considered to define a space coordinate system and an image coordinate system. Figure 2 As shown, consider the space coordinate system that defines right-handedness y - x ,That y Axis and speed v Parallel and reverse x Axis and y The axis is vertical. At the same time, a right-handed image coordinate system is defined on the image of the target object. t - u , where the column coordinates are recorded from left to right as u =1~ m Corresponding to each scanning sampling point, the row coordinates are recorded from top to bottom as t =1~ n Corresponding to each scanning moment. y - x In t =1At the initial moment, the scan line is the first line, along y Axis speed reverses with spacing vdt Arrange in order t =2~ n At each scan line at the moment, a global scan sampling point array is established, and the row and column direction vectors of the array are , There is a one-to-one correspondence between the sampling points of each row and column of the array and the pixels of each row and column of the image. Among them, the row and column direction vectors of the global scan sampling point array , With coordinate system y - x Basis Vectors , There is a basis transformation relationship, the spatial coordinate system y - x With the image coordinate system t - uThere is a coordinate transformation relationship between the coordinate points.

[0045] The basis transformation relationship can be expressed as: (1) (2) The coordinate transformation relationship can be expressed as: (3) (4) In the formula, is the spatial coordinate system y - x With the image coordinate system t - u The transformation matrix between .

[0046] in, (5) (6) In the formula, is the moving speed, and the angle between the scanning direction of the linear array camera and the speed direction of the target object is 90°+ (That is, the angle between the scanning line direction and the vertical line direction of the velocity is ,like Figure 2 The scan lines shown are counterclockwise for positive and clockwise for negative). The time interval between any two adjacent lines of pixel data collected by the line array camera (i.e., the line array camera scans line by line at a fixed time interval to obtain multiple lines of pixel data). It is the distance between any two adjacent sampling points among the multiple scanning sampling points included in the scanning line.

[0047] From this, it can be seen that the spatial coordinate system y - x With the image coordinate system t - u There is a relationship between the transformation matrix between the image and the moving speed of the target object. Therefore, by establishing a basis transformation relationship or a coordinate transformation relationship, and using the relationship between the transformation matrix and the moving speed of the target object, the moving speed of the target object can be determined. In the scheme of this example, the moving speed can be obtained based on at least the image geometry parameter information of the target object in the image, the actual geometry parameter information of the target object, and the basis transformation relationship or the coordinate transformation relationship. For example, the image geometry parameter information and the actual geometry parameter information can be substituted into the basis transformation relationship or the coordinate transformation relationship, and substituted into a preset time length for further solution, so as to obtain the moving speed of the target object.

[0048] In summary, the above technical solution can use the image geometric parameter information of the target object in the image captured by the linear array camera and the actual geometric parameter information of the target object to more accurately determine the moving speed of the target object. This speed measurement method can be used to measure the speed of any moving target object on a plane (such as a speed measurement target, an object with an edge line, or an object with a standard geometric shape on the surface). At the same time, due to the strong image stability, the solution is not easily affected by the difference in reflectivity and roughness of the target surface, ensuring the reliability of the speed measurement results. In addition, the image information has strong robustness and can be widely used in non-contact speed measurement of materials transported on production lines such as printing, textiles, and plates and strips.

[0049] Exemplarily, step S130, determining the moving speed of the target object based at least on the image geometric parameter information of the target object in the image, the actual geometric parameter information of the target object and the preset duration, may specifically include the following steps S131 and S132.

[0050] In step S131, based on the image geometric parameter information, the actual geometric parameter information and the coordinate transformation relationship between the spatial coordinate system where the target object is located and the image coordinate system where the image is located, a transformation matrix between the spatial coordinate system and the image coordinate system is determined.

[0051] In step S132, the moving speed of the target object is determined based on the ratio of the first element in the transformation matrix to the preset time length.

[0052] As mentioned above, the spatial coordinate system y - x With the image coordinate system t - u There is a coordinate transformation relationship between the coordinate points in the space coordinate system and the image coordinate system, and the first element in the transformation matrix is ​​positively correlated with the moving speed. In the scheme of this example, it is considered to first substitute the image geometric parameter information and the actual geometric parameter information into the coordinate transformation relationship between the spatial coordinate system and the image coordinate system to determine the transformation matrix. Then, the moving speed of the target object is determined according to the ratio of the first element in the transformation matrix to the preset time length. This scheme is simple to operate and can quickly and accurately determine the moving speed of the target object.

[0053] Exemplarily, the target object is a speed measuring target, which includes multiple target points. Step S120 determines the actual geometric parameter information of the target object and the image geometric parameter information of the target object in the image, including: determining the image coordinates of each target point in the image; determining the spatial coordinates of each target point in the multiple target points; wherein the number of target points in the multiple target points is greater than or equal to two; the origin of the spatial coordinate system coincides with the origin of the image coordinate system; the actual geometric parameter information includes the spatial coordinates of each target point in the multiple target points, and the image geometric parameter information includes the image coordinates of each target point in the image.

[0054] Step S131, based on the image geometric parameter information, the actual geometric parameter information and the coordinate transformation relationship between the spatial coordinate system where the target object is located and the image coordinate system where the image is located, determine the transformation matrix between the spatial coordinate system and the image coordinate system, including: determining the transformation matrix based on the image coordinates and spatial coordinates of each target point among multiple target points and the coordinate transformation relationship.

[0055] It can be understood that a speed target is a plane figure used for speed measurement (usually a checkerboard or a dot matrix), and its surface is distributed with m≥2 target points (such as checkerboard corner points) in different lateral positions in both the horizontal and vertical directions, including the speed target origin, and the exact position of other target points relative to the origin is known. In actual application scenarios, the speed target can be attached to the object to be measured. Since the moving speed of the speed target is the same as the moving speed of the object, the speed measurement of the object can be simplified to measuring the speed of the speed target carried on the object. In this article, for the sake of simplicity, the speed target on the object to be measured is used as the target object.

[0056] In the solution of this example, the origin of the speed measuring target is the origin of the spatial coordinate system. Since the accurate positions of other target points on the speed measuring target relative to the origin are known, the coordinates of each target point on the speed measuring target can be obtained through user input. Optionally, determining the spatial coordinates of each target point among the multiple target points includes: determining the spatial coordinates of each target point among the multiple target points according to the coordinate information input by the user.

[0057] Optionally, determining the image coordinates of each target point in the image among the multiple target points includes: using an image algorithm to calculate the image coordinates of each target point in the image. The image algorithm may be a feature point recognition algorithm.

[0058] Figure 3 The figure shows the transformation relationship between the spatial coordinate system and the image coordinate system when the target object is a speed measuring target according to an embodiment of the present invention. The left side of the figure shows a schematic diagram of the speed measuring target in the spatial coordinate system, and the right side shows a schematic diagram of the speed measuring target in the image coordinate system. Figure 3As shown in the figure, the origin of the spatial coordinate system and the origin of the image coordinate system are both the upper left corner of the velocity measurement target. The image coordinates of multiple target points can be expressed as ( t 1 ,u 1) ( t 2 ,u 2)……( t m ,u m ).

[0059] Optionally, the method further includes: acquiring an initial image of the speed measuring target; and cropping the initial image to obtain a local image in which the origin of the speed measuring target is at a corner of the image. The image acquired in step S110 is the local image. By cropping the initial image of the speed measuring target, it is convenient to establish an image coordinate system in the subsequent process, thereby facilitating the determination of the image coordinates of each target point in the image coordinate system.

[0060] After the image coordinates and the space coordinates of each target point are determined, the image coordinates and the space coordinates can be substituted into the coordinate transformation relationship to determine the transformation matrix.

[0061] In the above technical solution, the image coordinates and space coordinates of each target point on the speed measuring target are determined, and the transformation matrix is ​​determined according to the coordinate transformation relationship between the space coordinate system and the image coordinate system. This solution is simple to calculate and can quickly and accurately determine the transformation matrix, thereby providing an accurate basis for determining the moving speed in subsequent steps.

[0062] Exemplarily, determining the transformation matrix based on the image coordinates and the space coordinates of each target point in the plurality of target points and the coordinate transformation relationship includes: determining the transformation matrix by the following formula: (7) (8) (9) in, is the transformation matrix T In vector form, , ; Represents the horizontal coordinates of the spatial coordinates of multiple target points. Represents the ordinate of each of the multiple target points in the spatial coordinates, Represents the horizontal coordinates of the image coordinates of multiple target points. Represents the vertical coordinates of each of the multiple target points in the image coordinates.

[0063] In this example, formula (2) can be expanded as follows: (10) Further expansion yields: (11) Simplifying formula (11) yields: (12) From this, we can deduce formula (7).

[0064] According to equations (7), (8), and (9), we can obtain: (13) After obtaining the spatial coordinates and image coordinates of at least two target points, the coordinates can be substituted into equation (13) to obtain the actual value of each element in the transformation matrix.

[0065] The above solution can determine the transformation matrix more accurately, thereby providing an accurate basis for determining the moving speed in subsequent steps.

[0066] Exemplarily, the target object is a circular object, which is laid flat on a conveyor belt, and the radius of the circular object is a preset radius; step S120, determining actual geometric parameter information of the target object and image geometric parameter information of the target object in the image, including: determining the major axis radius, minor axis radius and axis inclination angle of the target object in the image; wherein the actual geometric parameter information is the radius of the circular object, and the image geometric parameter information includes the major axis radius, minor axis radius and axis inclination angle of the target object in the image.

[0067] Step S131, based on the image geometric parameter information, the actual geometric parameter information and the coordinate transformation relationship between the spatial coordinate system where the target object is located and the image coordinate system where the image is located, determine the transformation matrix between the spatial coordinate system and the image coordinate system, including: determining the transformation matrix based on the coordinate transformation relationship, the major axis radius, minor axis radius and axis inclination angle of the target object in the image and a preset radius.

[0068] In this example, the target object is a round object. The round object is an object whose upper surface is round and whose round surface is parallel to the conveyor belt surface when placed on the conveyor belt. The object includes but is not limited to bottle caps, cans, etc.

[0069] As described above, the circular surface appears as an ellipse in the image captured by the linear array camera due to the shear distortion phenomenon. Figure 4 The figure shows the transformation relationship between the spatial coordinate system and the image coordinate system when the target object is a circular object according to an embodiment of the present invention. The left side of the figure shows a schematic diagram of a circular object in the spatial coordinate system, and the right side shows a schematic diagram of a circular object in the image coordinate system. Figure 4 As shown, the radius of the circular object is r , the radius of the major axis of the ellipse is , the minor axis radius is b , the axis inclination angle is α .

[0070] In order to make the coordinates of the image coordinate system coincide with the coordinates of the spatial coordinate system, in this example, for the convenience of calculation, consider scaling the ellipse in the image coordinate system and the circle in the spatial coordinate system to the origin of the corresponding coordinate system. In some embodiments, an auxiliary unit circle with a radius of 1 can be established at the origin of the spatial coordinate system. C r ' , the expression of the auxiliary unit circle is: (14) At the same time, an auxiliary ellipse can be created at the origin of the image coordinate system, which is proportional to the ellipse (target object) in the image. For example, an auxiliary ellipse can be created at the origin of the image coordinate system. , its major axis radius, minor axis radius, and axis inclination angle are , b / r , , whose expression is: (15) in, A , W is the parameter matrix of the auxiliary ellipse.

[0071] Since the auxiliary ellipse, the auxiliary unit circle and the original figure only have translation and proportional relationships, the auxiliary ellipse and the auxiliary unit circle still have the same offset coordinate transformation relationship. Substituting equation (4) into equation (14), the parameter expression of the auxiliary ellipse in the image coordinate system can be obtained: (16) In the solution of this example, the radius of the circular object can be obtained by pre-measurement, which is not described in detail. Determining the long axis radius, short axis radius and axis inclination angle of the target object in the image can specifically include the following steps: using an image algorithm to calculate the long axis radius, short axis radius and axis inclination angle of the target object in the image. The image algorithm can be Hough transform, least squares method, etc.

[0072] In the above technical solution, the long axis radius, short axis radius and axis inclination angle of the target object in the image and the preset radius of the target object are determined, and the transformation matrix is ​​determined according to these parameters. The solution is simple to calculate and can quickly and accurately determine the transformation matrix, thereby providing an accurate basis for determining the moving speed in the subsequent steps.

[0073] Exemplarily, determining the transformation matrix based on the coordinate transformation relationship, the major axis radius, the minor axis radius and the axis inclination angle of the target object in the image and the preset radius includes: determining the transformation matrix by the following formula: (17) (18) (19) in, T represents the transformation matrix; represents the major axis radius, b represents the minor axis radius, α represents the axis inclination angle, r represents the preset radius. Formula (17) can be expressed as there is a unique solution transformation matrix T Make the Cholesky decomposition valid.

[0074] According to the above description, after obtaining equation (16), combining equation (15) and equation (16), we can get: (20) Since the matrix containing known geometric parameters is a positive definite real symmetric matrix, which can be decomposed into a unique upper triangular matrix using the matrix Cholesky decomposition method T (That is, formula (17)). Thus, the transformation matrix can be determined.

[0075] The above solution can determine the transformation matrix more accurately, thereby providing an accurate basis for determining the moving speed in subsequent steps.

[0076] Exemplarily, determining the moving speed of the target object based on the ratio of the first element in the transformation matrix to the preset time length includes: determining the moving speed by the following formula: (twenty one) in, Indicates the moving speed, Represents the first element in the transformation matrix, The preset duration.

[0077] After determining the transformation matrix, the actual value of each element in the transformation matrix can be determined. And as can be seen from formula (5), the first element in the transformation matrix is ​​positively correlated with the moving speed. In this case, the moving speed of the target object can be further determined based on the ratio of the first element in the transformation matrix to the preset time length. This solution is simple to calculate and can determine the moving speed of the target object more accurately.

[0078] Exemplarily, the angle between the scanning line direction of the linear array camera and the perpendicular line direction of the speed of the target object is a first preset angle; the scanning line of the linear array camera includes multiple scanning sampling points, and the spacing between any two adjacent sampling points in the multiple scanning sampling points is a preset spacing; after determining the moving speed of the target object, the method also includes: determining the error of the moving speed based on the first preset angle, the preset spacing and the transformation matrix; when the error is less than or equal to the error threshold, determining that the moving speed is reliable; wherein the second element in the transformation matrix is ​​negatively correlated with the sine of the first preset angle and the preset spacing, and the third element in the transformation matrix is ​​positively correlated with the cosine of the first preset angle and the preset spacing.

[0079] The inventors have found through research that the second element in the transformation matrix is ​​negatively correlated with the sine of the first preset angle and the preset spacing, and the third element in the transformation matrix is ​​positively correlated with the cosine of the first preset angle and the preset spacing. As shown in formula (5), the second element , the third element Since the first preset angle and the preset distance are both known quantities, in the solution of this example, the inventor considers calculating the difference between the theoretical value and the actual first preset angle and preset distance through the above correlation, and evaluating the reliability of the calculated moving speed based on the difference.

[0080] Optionally, the error of the moving speed includes an angle error and a spacing error. When the error is less than or equal to an error threshold, determining that the moving speed is reliable includes: when the angle error is less than or equal to a first error threshold, and the spacing error is less than or equal to a second error threshold, determining that the moving speed is reliable. The first error threshold and the second error threshold can be determined according to actual needs, and will not be repeated.

[0081] Optionally, based on the first preset angle, the preset distance and the transformation matrix, determining the error of the moving speed includes determining the distance error and the angle error by the following formula: (twenty two) (twenty three) In the above technical solution, the error of the moving speed is determined by the first preset angle, the preset distance and the transformation matrix, and the error is used to evaluate whether the determined moving speed is reliable. Therefore, the solution helps to improve the reliability of the determined moving speed.

[0082] Exemplarily, a scanning line direction of the linear array camera and a perpendicular line direction of the speed of the target object are at a first preset angle; the scanning line of the linear array camera includes a plurality of scanning sampling points, and a spacing between any two adjacent sampling points among the plurality of scanning sampling points is a preset spacing; the target object is an object with a straight edge; step S120, determining actual geometric parameter information of the target object and image geometric parameter information of the target object in the image, includes: determining an actual angle of the straight edge and an image angle of the straight edge in the image; wherein the actual geometric parameter information is an actual angle, and the image geometric parameter information is an image angle.

[0083] Step S130, determining the moving speed of the target object based at least on the image geometric parameter information of the target object in the image, the actual geometric parameter information of the target object and the preset time, including: determining the moving speed based on the actual angle, image angle, preset time, first preset angle and preset spacing.

[0084] As mentioned above, there is a basis transformation relationship between the vector in the space coordinate system and the vector in the image coordinate system. In the solution of this example, it is considered to establish a basis transformation relationship based on the real angle of the straight line edge (i.e., the actual angle) and the angle of the straight line edge in the image (i.e., the image angle), and determine the moving speed based on the basis transformation relationship and the relationship between each element in the transformation matrix and the moving speed.

[0085] Optionally, determining the actual angle of the straight edge includes: determining the actual angle of the straight edge according to angle information input by the user. In this example, the user can predetermine the actual angle of the straight edge according to actual conditions, that is, the actual angle is a known quantity.

[0086] Determining the image angle of the straight edge in the image includes: using an image algorithm to calculate the image angle of the straight edge in the image. The image algorithm includes but is not limited to an image feature line recognition algorithm or a Hough transform method.

[0087] Figure 5 The figure shows the transformation relationship between the spatial coordinate system and the image coordinate system when the target object is an object with straight edges according to an embodiment of the present invention. The left side of the figure is a schematic diagram of an object with straight edges in the spatial coordinate system, and the right side of the figure is a schematic diagram of an object with straight edges in the image coordinate system. Figure 5 As shown, the actual angle is (When the edge is tilted in the clockwise direction, the angle Take positive value), the image angle is .

[0088] In the above technical scheme, by determining the actual angle of the straight edge and the image angle of the straight edge in the image, and determining the moving speed of the target object based on the actual angle, image angle, preset duration, first preset angle and preset spacing, the scheme is simple to calculate and can quickly and accurately determine the moving speed of the target object.

[0089] Exemplarily, determining the moving speed based on the actual angle, the image angle, the preset duration, the first preset angle, and the preset spacing includes: determining the moving speed by the following formula: (twenty four) in, is the moving speed, is the first preset angle, is the actual angle, is the image angle, For the preset duration, The preset spacing.

[0090] In this example, the edge line vector corresponding to the straight edge in the image coordinate system is proportional to the row and column direction vectors of the array. , The following relationship exists: (25) That is, the vector coordinates of the edge line in the image coordinate system are: .

[0091] Edge line vector and basis vector corresponding to the edge of the straight line in the spatial coordinate system , The following relationship exists: (26) Substituting equation (2) and equation (6) into equation (26), we can obtain: (27) Therefore, the vector coordinates of the edge line vector in the image coordinate system are .

[0092] Substituting the vector coordinates of the edge line vector in the image coordinate system into equation (25), we can obtain: (28) Therefore, according to formula (28), formula (24) can be derived.

[0093] In some embodiments, the direction of the edge line in the spatial coordinate system is perpendicular to the moving speed direction of the target object. ω= 0. In this case, equation (24) can be simplified as: (29) The above technical solution can accurately determine the moving speed of the target object, which helps to improve the calculation efficiency of the moving speed. According to equations (24) and (29), it can be seen that the moving speed is inversely proportional to the tangent value of the image angle. The faster the speed, the smaller the edge angle in the image. Therefore, this method is more suitable for solving the moving speed of target objects in medium and high speed scenes.

[0094] Exemplarily, the first preset angle The tangent value and the actual angle The sum of the tangent values ​​of is not 0. The first preset angle The actual angle The angle expansion direction is as follows Figure 5 As shown. According to formula (24) and formula (29), it can be seen that increasing the size of the first preset angle and the actual angle is helpful to improve the sensitivity of the speed measurement formula (i.e., formula (24)). The actual angle When the values ​​are the same but have opposite signs, , the above formula cannot determine the moving speed. This solution can ensure the effectiveness of the method by making the first preset angle different from the actual angle, and thus can more accurately determine the moving speed of the target object.

[0095] Exemplarily, the preset spacing is within the target spacing range. It is understandable that when the sampling point spacing increases, the sensitivity of the above-mentioned speed measurement formula can be improved. However, too large a sampling point spacing may result in reduced image recognition. In the scheme of this example, by making the preset spacing within the target spacing range, it helps to ensure that the image has enough recognizable details and that the speed measurement formula has better sensitivity. The target spacing range can be set according to actual needs and will not be elaborated.

[0096] Exemplarily, the preset duration is within the target duration range. It is understandable that when the preset duration is reduced, the sensitivity of the above speed measurement formula can be improved. However, if the preset duration is too short, the image data flow may be too large, and it can be set according to the actual needs based on the performance of the linear array camera and other related hardware, which will not be described in detail.

[0097] According to another aspect of an embodiment of the present invention, a speed measurement system is provided, which is used to measure the speed of a target object on a conveyor belt; the speed measurement system includes a controller and a linear array camera for acquiring images, the linear array camera is fixed above the conveyor belt, and the scanning line of the linear array camera is not perpendicular to the moving direction of the target object; the controller is used to implement the speed measurement method in any of the above embodiments.

[0098] According to yet another aspect of the embodiments of the present invention, an electronic device is provided. Figure 6 FIG. 2 shows a schematic block diagram of an electronic device according to an embodiment of the present invention. Figure 6 As shown, the electronic device 600 includes: a processor 610 and a memory 620. The memory 620 stores a computer program, and the processor 610 is used to execute the computer program to implement the above method.

[0099] According to another aspect of an embodiment of the present invention, a computer-readable storage medium is also provided. The storage medium stores a computer program / instruction, and the computer program / instruction implements the above method when executed by a processor. The storage medium may include, for example, a read-only memory (ROM), an erasable programmable read-only memory (EPROM), a portable compact disk read-only memory (CD-ROM), a USB memory, or any combination of the above storage media. The computer-readable storage medium may be any combination of one or more computer-readable storage media.

[0100] A person skilled in the art can easily understand the implementation structure, working principle and beneficial effects of the speed measurement system, electronic device and computer-readable storage medium by reading the above method. For the sake of brevity, no further description is given here.

[0101] Although example embodiments have been described herein with reference to the accompanying drawings, it should be understood that the above example embodiments are merely exemplary and are not intended to limit the scope of the present invention thereto. Various changes and modifications may be made therein by one of ordinary skill in the art without departing from the scope and spirit of the present invention. All such changes and modifications are intended to be included within the scope of the present invention as required by the appended claims.

[0102] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0103] In the several embodiments provided by the present invention, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic, for example, the division of units is only a logical function division, and there may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another device, or some features can be ignored or not executed.

[0104] In the description provided herein, a large number of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

[0105] Similarly, it should be understood that in order to streamline the present invention and help understand one or more of the various inventive aspects, in the description of the exemplary embodiments of the present invention, the various features of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, the method of the present invention should not be interpreted as reflecting the following intention: the claimed invention requires more features than the features explicitly stated in each claim. More specifically, as reflected in the corresponding claims, the inventive point is that the corresponding technical problem can be solved with less than all the features of a single disclosed embodiment. Therefore, the claims following the specific embodiment are hereby expressly incorporated into the specific embodiment, wherein each claim itself serves as a separate embodiment of the present invention.

[0106] Those skilled in the art will understand that, except for mutually exclusive features, all features disclosed in this specification (including the accompanying claims, abstract and drawings) and all processes or units of any method or device disclosed in this specification may be combined in any combination. Unless otherwise explicitly stated, each feature disclosed in this specification (including the accompanying claims, abstract and drawings) may be replaced by an alternative feature that provides the same, equivalent or similar purpose.

[0107] In addition, those skilled in the art will appreciate that, although some embodiments described herein include certain features included in other embodiments but not other features, the combination of features of different embodiments is meant to be within the scope of the present invention and form different embodiments. For example, in the claims, any one of the claimed embodiments may be used in any combination.

[0108] The various component embodiments of the present invention may be implemented in hardware, or in software modules running on one or more processors, or in a combination thereof. It should be understood by those skilled in the art that a microprocessor or a digital signal processor (DSP) may be used in practice to implement some or all functions of some modules in an electronic device according to an embodiment of the present invention. The present invention may also be implemented as a device program (e.g., a computer program and a computer program product) for executing part or all of the methods described herein. Such a program implementing the present invention may be stored on a computer-readable medium, or may be in the form of one or more signals. Such a signal may be downloaded from an Internet website, or provided on a carrier signal, or provided in any other form.

[0109] It should be noted that the above embodiments illustrate the present invention rather than limit it, and that those skilled in the art may devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference symbol between brackets shall not be construed as a limitation on the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "one" or "an" preceding an element does not exclude the presence of a plurality of such elements. The present invention may be implemented by means of hardware comprising a number of different elements and by means of a suitably programmed computer. In a unit claim enumerating a number of devices, several of these devices may be embodied by the same hardware item. The use of the words first, second, and third, etc., does not indicate any order. These words may be interpreted as names.

[0110] The above is only a specific embodiment of the present invention or an explanation of a specific embodiment. The protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. The protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A speed measurement method based on oblique scanning and shearing transformation, characterized in that: Used in a speed measurement system; the speed measurement system is used to measure the speed of a target object on a conveyor belt; the speed measurement system comprises a line array camera for collecting images, the line array camera is fixed above the conveyor belt, and the scanning line of the line array camera is not perpendicular to the moving direction of the target object; The method comprises: Acquire an image of the target object, the image comprising a plurality of lines of pixel data sequentially acquired by the line array camera, wherein the time interval between any two adjacent lines of pixel data acquired by the line array camera in the plurality of lines of pixel data is a preset time length; Determine actual geometric parameter information of the target object and image geometric parameter information of the target object in the image; The moving speed of the target object is determined based at least on the image geometric parameter information of the target object in the image, the actual geometric parameter information of the target object and the preset time length.

2. The speed measurement method according to claim 1, characterized in that: The determining the moving speed of the target object based at least on the image geometric parameter information of the target object in the image, the actual geometric parameter information of the target object and the preset time duration includes: Determine a transformation matrix between the spatial coordinate system and the image coordinate system based on the image geometric parameter information, the actual geometric parameter information, and a coordinate transformation relationship between the spatial coordinate system where the target object is located and the image coordinate system where the image is located, wherein the transformation matrix includes a plurality of elements, and a first element of the plurality of elements is positively correlated with a speed of the target object; The moving speed of the target object is determined based on the ratio of the first element in the transformation matrix to the preset time length.

3. The speed measurement method according to claim 2, characterized in that: The target object is a speed measuring target, and the speed measuring target includes a plurality of target points; The determining of the actual geometric parameter information of the target object and the image geometric parameter information of the target object in the image includes: determining the image coordinates of each target point of the plurality of target points in the image; determining the spatial coordinates of each target point among the plurality of target points; The number of target points in the plurality of target points is greater than or equal to two; the origin of the spatial coordinate system coincides with the origin of the image coordinate system; the actual geometric parameter information includes the spatial coordinates of each target point in the plurality of target points, and the image geometric parameter information includes the image coordinates of each target point in the image; The determining of the transformation matrix between the spatial coordinate system and the image coordinate system based on the image geometric parameter information, the actual geometric parameter information, and the coordinate transformation relationship between the spatial coordinate system where the target object is located and the image coordinate system where the image is located comprises: A transformation matrix is ​​determined based on the image coordinates and the space coordinates of each target point in the plurality of target points and the coordinate transformation relationship.

4. The speed measurement method according to claim 3, characterized in that: The determining of the transformation matrix based on the image coordinates and the spatial coordinates of each target point in the plurality of target points and the coordinate transformation relationship comprises: determining the transformation matrix by the following formula: in, is the transformation matrix T In vector form, , ; represents the abscissa of each of the plurality of target points in the spatial coordinates, represents the ordinate in the spatial coordinates of each of the plurality of target points, represents the abscissa of each of the plurality of target points in the image coordinates, The vertical coordinate of each of the plurality of target points in the image coordinates is represented.

5. The speed measurement method according to claim 2, characterized in that: The target object is a round object, the round object is laid flat on the conveyor belt, and the radius of the round object is a preset radius; The determining of the actual geometric parameter information of the target object and the image geometric parameter information of the target object in the image includes: Determine the major axis radius, minor axis radius and axis inclination angle of the target object in the image; The actual geometric parameter information is the radius of the circular object, and the image geometric parameter information includes the major axis radius, minor axis radius and axis inclination angle of the target object in the image; The determining of the transformation matrix between the spatial coordinate system and the image coordinate system based on the image geometric parameter information, the actual geometric parameter information, and the coordinate transformation relationship between the spatial coordinate system where the target object is located and the image coordinate system where the image is located comprises: Determine a transformation matrix based on the coordinate transformation relationship, the major axis radius, the minor axis radius and the axis inclination angle of the target object in the image, and the preset radius; Preferably, determining the transformation matrix based on the coordinate transformation relationship, the major axis radius, the minor axis radius and the axis inclination angle of the target object in the image and the preset radius includes: determining the transformation matrix by the following formula: in, T represents the transformation matrix; represents the major axis radius, b represents the minor axis radius, α represents the axis inclination angle, r Indicates the preset radius.

6. The speed measurement method according to any one of claims 2 to 5, characterized in that: The determining the moving speed of the target object based on the ratio of the first element in the transformation matrix to the preset time length includes: determining the moving speed by the following formula: in, represents the moving speed, represents the first element in the transformation matrix, is the preset duration; Preferably, the angle between the scanning line direction of the line array camera and the vertical line direction of the target object speed is a first preset angle; the scanning line of the line array camera includes a plurality of scanning sampling points, and the spacing between any two adjacent sampling points among the plurality of scanning sampling points is a preset spacing; after determining the moving speed of the target object, the method further includes: Determine the error of the moving speed based on the first preset angle, the preset distance and the transformation matrix; When the error is less than or equal to the error threshold, determining that the moving speed is reliable; The second element in the transformation matrix is ​​negatively correlated with the sine of the first preset angle and the preset distance, and the third element in the transformation matrix is ​​positively correlated with the cosine of the first preset angle and the preset distance.

7. The speed measurement method according to claim 1, characterized in that: The angle between the scanning line direction of the linear array camera and the vertical line direction of the target object speed is a first preset angle; the scanning line of the linear array camera includes a plurality of scanning sampling points, and the spacing between any two adjacent sampling points among the plurality of scanning sampling points is a preset spacing; The target object is an object with a straight edge; The determining of the actual geometric parameter information of the target object and the image geometric parameter information of the target object in the image includes: determining an actual angle of the straight edge and an image angle of the straight edge in the image; Wherein, the actual geometric parameter information is the actual angle, and the image geometric parameter information is the image angle; The determining the moving speed of the target object based at least on the image geometric parameter information of the target object in the image, the actual geometric parameter information of the target object and the preset time duration includes: Determining the moving speed based on the actual angle, the image angle, the preset duration, the first preset angle, and the preset distance; Preferably, determining the moving speed based on the actual angle, the image angle, the preset duration, the first preset angle and the preset interval includes: determining the moving speed by the following formula: in, is the moving speed, is the first preset angle, is the actual angle, is the image angle, is the preset duration, is the preset spacing; Preferably, the sum of the tangent value of the first preset angle and the tangent value of the actual angle is not 0; Preferably, the preset spacing is within the target spacing range; Preferably, the preset duration is within a target duration range.

8. A speed measurement system, characterized in that: Used to measure the speed of target objects on a conveyor belt; the speed measurement system includes a controller and a linear array camera for acquiring images, the linear array camera is fixed above the conveyor belt, and the scanning line of the linear array camera is not perpendicular to the moving direction of the target object; the controller is used to implement the method described in any one of claims 1-7.

9. An electronic device, characterized in that: The method comprises a processor and a memory, wherein the memory stores a computer program, and the processor is used to execute the computer program to implement the method according to any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that: A computer program / instruction is stored, and when the computer program / instruction is executed by a processor, the method according to any one of claims 1 to 7 is implemented.

Images