Scheduling method of large-scale heliostat field artificial light source and camera cooperative calibration heliostat

Abstract

The invention relates to the field of heliostat calibration, and discloses a scheduling method for calibrating heliostats through cooperation of artificial light sources and cameras in a large-scale heliostat field, and the method comprises the following steps: determining the heliostat range covered by each camera, determining the heliostat range covered by each artificial light source, and determining the heliostat range covered by each camera; the method comprises the following steps: determining the center and size of a light spot in an image shot by a camera when the heliostats are calibrated, determining the heliostats which can be calibrated in the coverage range of each artificial light source-camera combination, regarding each effective calibration combination as a node to construct an undirected graph, dividing the nodes into a plurality of groups through a graph grouping algorithm, and ensuring that the nodes in the same group are not connected with each other, therefore, all combinations in the same group can execute calibration in parallel. According to the method disclosed by the invention, the problem of affiliation misjudgment caused by light spot interference between heliostats is solved, possible shadow and shielding problems are avoided, dynamic scheduling of the artificial light source and the camera is realized, and invalid operation time is shortened.

Description

Technical Field

[0001] This invention relates to the field of heliostat calibration, and in particular to a scheduling method for coordinating the calibration of a heliostat using a large-scale artificial light source and a camera. Background Technology

[0002] In tower-type solar thermal mirror fields, artificial light source calibration can make full use of non-heat-collecting periods for calibration. Artificial light source calibration refers to calibrating the parameters of the heliostat's motion model at night by having the heliostat reflect light from an artificial light source onto a camera. The artificial light source calibration method in tower-type solar thermal mirror fields requires installing calibration towers in the center and around the mirror field. Calibration cameras and artificial light sources are mounted on these towers. Alternatively, the absorber tower can be considered a calibration tower, with calibration cameras and artificial light sources also mounted on it. The number and location of calibration towers depend on the size of the mirror field and the height of the calibration towers, with the standard being that they can cover all the heliostats.

[0003] With the development of tower-type photothermal technology, the scale of the heliostat field has gradually expanded, and using multiple calibration towers to shorten calibration time has become an inevitable trend. This brings about problems, such as interference between heliostats when multiple towers are used for calibration. For example, the reflected light spots from artificial light sources in the same camera can overlap, making it difficult to identify which heliostat belongs to which device. Additionally, the obstruction of incident and reflected light by adjacent heliostats can also affect the calibration results. Finally, heliostat calibration sampling requires multiple sets of artificial light sources and cameras to identify calibration devices (cameras, artificial light sources) with larger errors and to calibrate them promptly (see invention patent: A self-correcting heliostat calibration method for calibration equipment, authorization announcement number CN116540788 B). Therefore, this problem needs to be considered during the calibration field scheduling process. To date, existing technologies mainly focus on the calibration method itself and have not considered how to effectively schedule the field during calibration to address the above problems, i.e., avoiding overlapping light spots of heliostats in the camera, shadow obstruction between heliostats, and scheduling conflicts during parallel calibration. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a scheduling method for coordinating the calibration of heliostats with large-scale artificial light sources and cameras. This method solves the problem of misclassification caused by light spot interference between heliostats, avoids potential shadow and occlusion issues, achieves dynamic scheduling of artificial light sources and cameras, and reduces ineffective operation time.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A scheduling method for coordinating the calibration of heliostats using large-scale artificial light sources and cameras in a mirror field includes the following steps: Step 1, Camera Coverage Modeling: Calculate the shooting range of each camera in the lens field through coordinate system transformation, and filter out the heliostats located within the camera's field of view; Step 2, Light Source Coverage Modeling: Based on the visible distance and angular parameters of each artificial light source, determine the heliostats within its effective illumination range; Step 3, Spot Parameter Calculation: The results of Step 1 and Step 2 are superimposed to form a candidate set of heliostats that are covered by the same "artificial light source-camera" combination; for each heliostat in the candidate set, the geometric center and equivalent circle radius of the imaging spot in the corresponding camera image are calculated using the principle of light reflection and the heliostat motion model. Step 4, Calibration Combination Screening: Based on the calculation results of Step 3, select the "artificial light source-camera-heliostat" combination where the light spot is completely located within the effective area of ​​the camera image to form an effective calibration combination set; Step 5, Parallel Calibration Grouping: Treat each valid calibration combination as a node and construct an undirected graph. If two combinations share a heliostat, or share a camera and the light spots may overlap, or there is light occlusion between the heliostats, then establish a connection edge between the corresponding nodes. Divide the nodes into several groups using a graph grouping algorithm to ensure that the nodes in the same group are not connected to each other, so that all combinations in the same group can perform calibration in parallel.

[0007] In the above scheme, the specific method of step 1 is as follows: Step 1.1, determine the camera's shooting range in the lens field: the coordinates of camera c in the lens field coordinate system are... The optical axis vector is The image captured by camera c has a width of W pixels and a height of H pixels. The area captured by the camera in the field of view is a quadrilateral, and the vertex coordinates are as follows: ; ; ; ; ; ; ; ; in, , They represent cameras respectively. The focal length in the x and y directions; , , , These represent the two-dimensional coordinates of the vertices of the quadrilateral within the shooting area; , , Let be the normalization factors of the three column vectors of the rotation matrix that transforms the lens field coordinate system to the camera coordinate system, expressed as: ; ; ; Step 1.2, Determine if the heliostat is within the camera's field of view: Set the heliostat. The coordinates are The method of ray determination is used to determine whether the heliostat is located within the quadrilateral, i.e., from the heliostat... Draw a ray to the right of the position if the ray intersects one and only one side of the quadrilateral, or passes through one and only one vertex of the quadrilateral and When the size of the heliostat is between the sizes of the y-coordinates of the two other vertices connecting the two sides of the given vertex, then the heliostat... It is located inside the quadrilateral; otherwise, it is located outside the quadrilateral.

[0008] In the above scheme, the specific method of step 2 is as follows: Step 2.1, Determine the coverage area of ​​the artificial light source on the mirror field: Artificial light source The coordinates are Its elliptic cone central axis vector is The two subtended angles corresponding to the major and minor axes of the ellipse are and Curve in the z=0 plane The range is the coverage area of ​​the artificial light source L in the mirror field; Represented as: ; in, , , The normalization factors for the three column vectors of the rotation matrix, which transforms the coordinate system between the artificial light source and the mirror field, are expressed as follows: ; ; ; Step 2.2, determine whether the heliostat is within the field of view covered by the artificial light source: heliostat The coordinates are The visible distance of the artificial light source L is Then, when the following two equations are satisfied, the heliostat... Within the coverage area of ​​the artificial light source L, that is: ; .

[0009] In the above scheme, step 3, calculating the geometric center of the light spot and the radius of the equivalent circle, includes: Step 3.1: Iteratively solve for the direction of the heliostat normal corresponding to the vertex of the quadrilateral of the light spot; Step 3.2: Calculate the coordinates of the image of the artificial light source in the heliostat in the mirror field when the reflected light passes through the vertex of the quadrilateral of the light spot; Step 3.3: Calculate the pixel coordinates of the image of the artificial light source in the heliostat and the image in the camera when the reflected light passes through the vertices of the light spot quadrilateral; Step 3.4: Calculate the geometric center of the light spot based on the pixel coordinates of the image of the artificial light source in the heliostat when the reflected light passes through the vertex of the light spot quadrilateral, determine the radius of the circumcircle based on the maximum distance from the vertex to the center, and then multiply it by an expansion factor greater than 1 to obtain the radius of the equivalent circle.

[0010] In the above scheme, the specific method of step 3.1 is as follows: a heliostat within the mirror field. The width and length of the mirror are respectively and The points corresponding to the four corners of the mirror are denoted as , , , The coordinates in the mirror coordinate system are respectively , , , Their coordinates in the mirror field coordinate system are denoted as follows: , , , ; When the artificial light source L forms an image on the surface of the heliostat h and the line connecting it to the camera c passes through the four corners of the mirror surface, the corresponding image points in the camera correspond to the four vertices of the parallelogram light spot formed in the image captured by the camera during the calibration of the heliostat h; for points... Its coordinates are obtained iteratively using the following method, with the initial values ​​as follows: ; ; ; ; ; ; ; ; ; ; Among them, subscript This indicates the first iteration. For the second iteration, the parameter index is changed from... Change to And so on for the rest; This indicates that when the artificial light source L forms an image on the surface of the heliostat h, the line connecting it to the camera c passes through the point [point missing]. The normal vector at time, , , This represents the value of the normal vector during the first iteration, i.e., the initial value of the iteration; and They are points Vectors and points pointing to camera c The normalization factor of the vector pointing to the artificial light source L. and Indicates the iterative solution process and The value at the first iteration; , , The line connecting the artificial light source to the camera in the heliostat passes through a point. At that time, the normalization factor of the three column vectors of the rotation matrix for the transformation between the heliostat coordinate system and the mirror field coordinate system. and Indicates the iterative solution process , The value at the first iteration; Point Coordinates in the mirror field coordinate system , , This represents their values ​​during the first iteration; For the iteration ; ; ; ; ; ; ; ; ; ; ; Among them, subscript and They represent the first Second and third The next iteration; when , , All are less than the specified threshold When the time is reached, the iteration ends, and the parameter value of the last iteration is taken as the final solution; Using the same method, the line connecting the image of the artificial light source L on the surface of the heliostat h and the camera c passes through the corresponding points at the other three corners of the mirror surface. , , The direction of the normal and the coordinates of the corner point.

[0011] In the above scheme, the specific method of step 3.2 is as follows: the line connecting the image of the artificial light source L in the mirror surface of the heliostat h and the camera c passes through the point. At that time, the coordinates of the image of the artificial light source L on the surface of the heliostat h in the mirror field are: ; ; ; in, The time corresponds to the line connecting the image of the artificial light source L in the mirror of the heliostat h and the camera c. , , , The situation at these four points; , , These represent the three components of the coordinates of the image of the artificial light source L in the mirror of the heliostat h under the corresponding conditions; , , This represents the three components of the heliostat h-normal vector under the corresponding conditions.

[0012] In the above scheme, the specific method of step 3.3 is as follows: the optical axis vector of camera c in the lens field coordinate system is... The line connecting the image of the artificial light source L in the mirror of the heliostat h and the camera c passes through the point. hour, The pixel coordinates of the image of the artificial light source L in the heliostat h in the camera. for: ; in, , They represent cameras respectively. The focal length in the x and y directions; and They represent cameras respectively. The pixel coordinates in the x and y directions corresponding to the center point of the captured image.

[0013] In the above scheme, the specific method of step 3.4 is as follows: the geometric center of the light spot Represented as: ; ; The radius of the circumcircle of the light spot is: ; ; Radius of the equivalent circle of the light spot The calculation is as follows: ; in, Indicates the expansion factor. >1.

[0014] In the above scheme, the specific method of step 4 is as follows: If the heliostat h is simultaneously within the coverage area of ​​both the artificial light source L and the camera c, then the heliostat h is within the coverage area of ​​the "artificial light source-camera combination: Lc"; if it is within the coverage area of ​​the "artificial light source-camera combination: Lc", then it is determined whether the image of the artificial light source L in the heliostat h is within the shooting range of the camera c under the boundary conditions; when the following conditions are met, it is considered that the heliostat h can be calibrated using the "artificial light source-camera combination: Lc", that is: ; ; Where W is the number of pixels in the width of the image captured by camera c, and H is the number of pixels in the height of the image; Record all heliostats that can be calibrated for each "artificial light source-camera combination" to form an effective calibration combination set of "artificial light source-camera-heliostat".

[0015] In the above scheme, step 5 uses a degree-first label propagation algorithm for graph grouping. In this algorithm, the degree of a node refers to the number of edges directly connected to that node. The algorithm iteratively executes the following steps until all nodes are grouped: (1) Initialize labels for all ungrouped nodes; (2) Prioritize nodes with low degree and that are not connected to each other, and change their labels to group labels; (3) Perform label propagation and mark the neighboring nodes of the group label node as not belonging to the same group; (4) Group nodes with group labels into the same group and remove them from the graph.

[0016] Through the above technical solution, the scheduling method for large-scale artificial light source and camera collaborative calibration of heliostat provided by the present invention has the following beneficial effects: 1. This invention is based on the principle of light reflection and the motion model of heliostats, and iteratively solves the direction of the normal to the heliostat corresponding to the vertex of the quadrilateral of the light spot; combined with the imaging principle of a pinhole camera, it accurately calculates the geometric center of the light spot and the radius of the equivalent circle, realizes the physical spatial isolation of the heliostat light spot, and solves the problem of misclassification caused by the interference of light spots between heliostats; 2. In the construction of the undirected graph, the present invention assumes that the nearest heliostat nodes are connected, and the subsequent grouping is not in the same group and is not calibrated at the same time, thus avoiding possible shadow and occlusion problems; 3. This invention constructs an undirected graph model of "artificial light source-camera-heliostat combination", and automatically groups the devices through a connected component algorithm (as described above), supporting parallel calibration of devices in the same group and improving calibration efficiency; 4. This invention achieves dynamic scheduling of artificial light sources and cameras through a grouping strategy, reducing ineffective operation time. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0018] Figure 1 This is a schematic diagram of a scheduling method for coordinating the calibration of a heliostat with a large-scale artificial light source and a camera, as disclosed in an embodiment of the present invention.

[0019] Figure 2 The diagram illustrates the ray method for determining whether a heliostat is located inside a quadrilateral. (a) shows the heliostat is inside the quadrilateral, and the ray passes through exactly one side. (b) shows the heliostat is inside the quadrilateral, and the ray passes through exactly one vertex, with the heliostat's y-coordinate between the values ​​of the other two vertices. (c) shows the heliostat is outside the quadrilateral, and the ray passes through both sides of the quadrilateral. (d) shows the heliostat is outside the quadrilateral, and the ray passes through exactly one vertex, but the heliostat's y-coordinate is greater than the y-coordinates of all other vertices.

[0020] Figure 3 Here is an example graph of undirected graph node grouping: (a) initialization, (b) first-choice node label, (c) first-level neighbor label, (d) second-level neighbor label, (e) second-level neighbor state transition, (f) iterative convergence, and (g) group formation and node removal. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0022] This invention provides a scheduling method for coordinating the calibration of heliostats with large-scale artificial light sources and cameras, such as... Figure 1 As shown, it includes the following steps:

[0023] Step 1: Camera Coverage Modeling: Calculate the shooting range of each camera within the lens field through coordinate system transformation, and select the heliostats located within the camera's field of view. This step provides basic spatial range data for subsequent artificial light source-camera combinations.

[0024] The specific method is as follows: Step 1.1, determine the camera's shooting range in the lens field: the coordinates of camera c in the lens field coordinate system are... The optical axis vector is Let the camera coordinate system be defined with the camera center perpendicular to the optical axis (z-axis), the horizontal line passing through the camera center and perpendicular to the optical axis (x-axis), and the third line passing through the camera center and perpendicular to these two lines (y-axis). The lens field coordinate system differs from the camera coordinate system by one translation and one rotation operation. Based on the vector representation of the three axes of the camera coordinate system in the lens field coordinate system, the matrix corresponding to the rotation operation can be obtained. .

[0025] The equation of the xy plane of the camera coordinate system in the mirror field coordinate system is: ; The equation of the x-axis of the camera coordinate system in the lens field coordinate system can be expressed as: ; The vector corresponding to the line is Then the equation of the yz plane of the camera coordinate system in the mirror field coordinate system is: ; The line of intersection between the xy plane and the yz plane of the camera coordinate system is the y-axis of the camera coordinate system. Its equation in the lens field coordinate system can be obtained by solving the equations of these two planes simultaneously, that is: ; Its corresponding vector is Therefore, the rotation matrix can be obtained. for: ; in, , , Let be the normalization factors of the three column vectors of the matrix, expressed as: ; ; ; Let the image captured by camera c have a width of W pixels and a height of H pixels. The heliostats within the field of view corresponding to the pixel coordinates of the four vertices of the image rectangle represent the heliostat range covered by the camera. Based on the relationship between the camera coordinate system coordinates and pixel coordinates at these four field of view positions, we can obtain: ; ; ; ; in, , They represent cameras respectively. The focal length in the x and y directions; , , , These represent the camera coordinates for the four camera positions.

[0026] by For example, solve for the corresponding mirror field coordinate system coordinates. .

[0027] First, based on the relationship between the camera coordinates and pixel coordinates at the aforementioned lens field position, we can see that: ; ; Combined with coordinate system transformation: ; Ignoring the topographical undulations of the mirror field, it can be assumed that Therefore, we can conclude that: ; Solving for the given information yields: ; ;

[0028] Similarly, we can obtain: ; ; ; ; ; ;

[0029] Step 1.2, Determine if the heliostat is within the camera's field of view: Set the heliostat. The coordinates are The method of rays is used to determine whether the heliostat is located inside the quadrilateral, that is, from the heliostat... A ray is drawn to the right from the position. If the ray intersects the quadrilateral on exactly one side (e.g., ...), then the quadrilateral is considered to be in a quadrilateral with a ray that intersects the quadrilateral on exactly one side. Figure 2 (as shown in (a)), or passing through one and only one vertex of the quadrilateral and When the size is between the sizes of the y-coordinates of the two other vertices connecting the two sides of this vertex (e.g.) Figure 2 As shown in (b) in the figure, the heliostat It is located inside the quadrilateral, otherwise it is located outside the quadrilateral (e.g. Figure 2 (as shown in (c, d)).

[0030] The equation of the line containing the ray is expressed as: ; by and Taking a defined edge as an example, the equation of the line containing it is expressed as: ; like or or If the ray does not intersect the edge, then the ray does not intersect the edge. Otherwise, calculate the x-coordinate of the intersection point between the ray and the line containing the ray. ,Right now: ; A ray intersects an edge if the following conditions are met: ; ; Otherwise, they will not intersect.

[0031] Using the same method, determine whether the ray intersects with the other three sides, and count the total number of intersections. If the final intersection count is 1, then the heliostat... Within the shooting range of camera c.

[0032] If it only intersects with two of the sides and ( This represents the y-coordinate of the common endpoint of both sides. (Indicates the index of the vertex of the quadrilateral), indicating that the ray passes through vertex i only, if... If the size of the heliostat is between the sizes of the y-coordinates of the two other vertices connecting the two sides of the given vertex, then the heliostat... Within the shooting range of camera c. For example, as Figure 2 As shown in (b), when the ray passes through vertex 2, it satisfies the following relationship: ; Then the sun diaphragm Within the shooting range of camera c.

[0033] Step 2, Light Source Coverage Modeling: Based on the visible distance and angular parameters of each artificial light source, determine the heliostats within their effective illumination range; the specific method is as follows:

[0034] Step 2.1, determine the coverage area of ​​the artificial light source on the mirror field:

[0035] The coverage of an artificial light source is related to its visibility distance and angular range. For an artificial light source with 360° visibility, only the visibility distance needs to be considered. Here, visibility distance refers to the distance between the artificial light source and the heliostat that achieves good calibration results. This distance is related to the brightness of the artificial light source and atmospheric visibility, and can be obtained through actual field testing. The angular range is related to the shape and installation method of the artificial light source. Here, we consider a more general case: an artificial light source with an elliptical cone angular range. Since the artificial light source with an angular range greater than 180° is generally placed vertically downwards, the effect on the mirror field is the same as that of a 360° visible artificial light source; therefore, we only consider the case where the angular range is less than 180°.

[0036] In this case, this artificial light source The coordinates are Its elliptical cone's central axis vector (direction away from the vertex) is The two subtended angles corresponding to the major and minor axes of the ellipse are and To maximize ground coverage, the long axis is aligned with a horizontal straight line. (Using artificial light sources) The location is the origin, the central axis vector is the z-axis, the line passing through the origin and parallel to the major axis is the x-axis, and the line passing through the origin and parallel to the minor axis is the y-axis. Establish an artificial light source coordinate system. In this coordinate system, the equation of the elliptical cone is: ; in, , , These represent the three components of the coordinates of a point in the artificial light source coordinate system.

[0037] The mirror field coordinate system differs from the artificial light source coordinate system by one translation and one rotation operation. Similar to the transformation between the mirror field coordinate system and the camera coordinate system, the matrix corresponding to the rotation operation can be obtained. for: ; in, , , The normalization factors for the three column vectors of the rotation matrix, which transforms the coordinate system between the artificial light source and the mirror field, are expressed as follows: ; ; ; Coordinates of a point in the mirror field coordinate system Its coordinate transformation relationship in the artificial light source coordinate system is as follows: ; Therefore, we can conclude that: ; Substituting the equation of the elliptic cone into the coordinate system of the artificial light source, we get: ; The intersection curve of the elliptical conic surface and the mirror field reference plane z=0 is: ; That is, curves in the z=0 plane The range is the coverage area of ​​the artificial light source L in the mirror field; Represented as: ; This indicates intersecting curves.

[0038] Step 2.2, determine whether the heliostat is within the field of view covered by the artificial light source: The equation of the straight line connecting the central axis of the elliptic cone is: ; Its intersection point with the mirror field reference plane z=0 is: ; Setting the Sun Mirror The coordinates are The visible distance of the artificial light source L is Then, when the following two equations are satisfied, the heliostat... Within the coverage area of ​​the artificial light source L, that is: ; .

[0039] Step 3: Calculation of light spot parameters: The results of Step 1 and Step 2 are superimposed to form a candidate set of heliostats covered by the same "artificial light source-camera" combination. For each heliostat in the candidate set, the geometric center and equivalent circle radius of its imaging light spot in the corresponding camera image are calculated using the principle of light reflection and the heliostat motion model. The results of this step directly determine the feasibility of subsequent calibration.

[0040] During artificial light source calibration, as the heliostat's normal direction is continuously fine-tuned, the position of the imaging pixels reflected from the heliostat onto the camera also changes. Combined with multiple images, this results in a parallelogram-shaped light spot. During calibration, it's crucial to avoid overlap between the light spots from two heliostats. Therefore, the center and circumcircle radius of the light spot must be calculated first. Light spots whose circumcircles intersect cannot be calibrated simultaneously. To prevent light spot shifts caused by factors such as heliostat foundation settlement and strong winds, the radius of the equivalent circle of the light spot should be slightly larger than the radius of its circumcircle.

[0041] First, the direction of the heliostat normal corresponding to the vertex of the light spot quadrilateral is solved iteratively using the principle of light reflection and the motion model of the heliostat. Then, the coordinates of the image of the artificial light source in the heliostat are solved using the principle of mirror imaging. Next, the pixel coordinates of the vertices of the light spot quadrilateral are solved using the principle of pinhole camera imaging. Finally, the geometric center of the light spot and the radius of the equivalent circle are determined by the vertex pixel coordinates.

[0042] Calculating the geometric center of the light spot and the radius of its equivalent circle includes:

[0043] Step 3.1: Iteratively solve for the direction of the heliostat normal corresponding to the vertex of the quadrilateral of the light spot; The specific method is as follows: Set up a heliostat within the field of view. The coordinates of the center of the mirror in the mirror field coordinate system are: A heliostat within the field of view The width and length of the mirror are respectively and The points corresponding to the four corners of the mirror are denoted as , , , The coordinates in the mirror coordinate system are respectively , , , Their coordinates in the mirror field coordinate system are denoted as follows: , , , ; When the artificial light source L forms an image on the surface of the heliostat h and the line connecting it to the camera c passes through the four corners of the mirror, the corresponding imaging points in the camera correspond to the four vertices of the parallelogram light spot formed in the image captured by the camera during the calibration of the heliostat h. Therefore, by solving for these four imaging points, the range of the light spot can be determined.

[0044] With point For example, when the artificial light source L forms an image on the surface of the heliostat h and the line connecting it to the camera c passes through point [point missing], How to determine the normal vector? At this point, the equation of the plane corresponding to the heliostat mirror is: ; A horizontal straight line passing through the center of the mirror plane The equation can be expressed as: ; The vector corresponding to the line is Then the line perpendicular to the center of the mirror The equation of the plane is: ; The line that intersects the plane and the mirror plane is the line perpendicular to the center of the mirror plane. straight line Its equation can be obtained by solving the two plane equations simultaneously, that is: ; With a straight line ,straight line Let the x-axis, y-axis, and z-axis be the mirror plane normal, respectively, and the center of the mirror plane be the origin. Establish a mirror coordinate system. The original coordinate system differs from the mirror coordinate system by one translation and one rotation operation. The matrix corresponding to the rotation operation is... for: ; in, , , Let be the normalization factors of the three column vectors of the matrix, expressed as: ; ; ; point The coordinates in the mirror field coordinate system can be obtained by transforming the coordinates in the heliostat mirror surface coordinate system, that is: ; but, ; ; ; An artificial light source within the mirror field The coordinates are The coordinates of camera c in the field coordinate system are: past the point The normal bisects the angle c L (point) (where c is the vertex of the corner, and the camera c and the artificial light source L are located on opposite sides of the corner, then the normal vector...) It can be represented as: ; ; ; in, and They are points Vectors and points pointing to camera c The normalization factors for the vector pointing to the artificial light source L are expressed as follows: ; .

[0045] Solve using the following iterative method , , , , , , , , and Let their initial values ​​for iteration be denoted as , , , , , , , , and The initial values ​​for the iteration are as follows: ; ; ; ; ; ; ; ; ; ; Among them, subscript This indicates the first iteration. For the second iteration, the parameter index is changed from... Change to And so on for the rest; This indicates that when the artificial light source L forms an image on the surface of the heliostat h, the line connecting it to the camera c passes through the point [point missing]. The normal vector at time, , , This represents the value of the normal vector during the first iteration, i.e., the initial value of the iteration; and They are points Vectors and points pointing to camera c The normalization factor of the vector pointing to the artificial light source L. and Indicates the iterative solution process and The value at the first iteration; , , The line connecting the artificial light source to the camera in the heliostat passes through a point. At that time, the normalization factor of the three column vectors of the rotation matrix for the transformation between the heliostat coordinate system and the mirror field coordinate system. and Indicates the iterative solution process , The value at the first iteration; Point Coordinates in the mirror field coordinate system , , This represents their values ​​during the first iteration.

[0046] For the iteration ; ; ; ; ; ; ; ; ; ; ; Among them, subscript and They represent the first Second and third The next iteration; when , , All are less than the specified threshold When the parameter value is 0.001 (for example), the iteration ends, and the parameter value of the last iteration is taken as the final solution.

[0047] Similarly, we can find that the line connecting the image of the artificial light source L in the heliostat h and the camera c passes through the other three corresponding points on the mirror surface. , , The direction of the normal and the coordinates of the corner point.

[0048] Step 3.2: Calculate the coordinates of the image of the artificial light source in the heliostat in the mirror field when the reflected light passes through the vertex of the quadrilateral of the light spot;

[0049] The specific method is as follows:

[0050] Below, the line connecting the image formed by the artificial light source L in the mirror of the heliostat h and the camera c passes through the point. Let's take the case of an artificial light source L as an example to illustrate how to determine the coordinates of the image of the artificial light source L on the surface of the heliostat h in the mirror field.

[0051] In this case, the artificial light source L passes through, and is in conjunction with the heliostat. The current normal vector The equations of the parallel lines are: ; The equation of the straight line and the heliostat Solving the simultaneous equations of the mirror's plane yields the artificial light source. In the heliostat Projected coordinates of the mirror plane Represented as: ; ; ; Artificial light source In the heliostat The coordinates of the image in the mirror in the mirror field coordinate system Represented as: ; ; ; Right now: ; ; ; in, The time corresponds to the line connecting the image of the artificial light source L in the mirror of the heliostat h and the camera c. , , , The situation at these four points; , , These represent the three components of the coordinates of the image of the artificial light source L in the mirror of the heliostat h under the corresponding conditions; , , This represents the three components of the heliostat h-normal vector under the corresponding conditions.

[0052] Similarly, we can find that the line connecting the image of the artificial light source L in the heliostat h and the camera c passes through the other three corresponding points on the mirror surface. , , Artificial light source In the heliostat Coordinates of the image in the mirror , , .

[0053] Step 3.3: Calculate the pixel coordinates of the image of the artificial light source in the heliostat and the image in the camera when the reflected light passes through the vertices of the light spot quadrilateral;

[0054] The optical axis vector of camera c in the lens field coordinate system is Let the camera coordinate system be defined with the optical axis as the z-axis, the horizontal line passing through the camera center and perpendicular to the optical axis as the x-axis, and the third line passing through the camera center and perpendicular to these two lines as the y-axis. The lens field coordinate system differs from the camera coordinate system by one translation and one rotation operation. The matrix corresponding to the rotation operation... for: ; in, , , Let be the normalization factors of the three column vectors of the matrix, expressed as: ; ; .

[0055] Below, the line connecting the image formed by the artificial light source L in the mirror of the heliostat h and the camera c passes through the point. Let's take a case as an example to illustrate how to determine the pixel coordinates of the vertices of the corresponding light spot quadrilateral.

[0056] In this case, artificial light sources In the heliostat The coordinates of the image in the mirror in the mirror field coordinate system coordinates in the camera coordinate system The transformation relationship is as follows: ; but, ; in, Indicates transpose. yes The transpose of is given. Therefore, the coordinate representation in the camera coordinate system can be obtained as: ; ; Its pixel coordinates are: ; in, and Determine the x and y coordinates of the pixel; , They represent cameras respectively. The focal length in the x and y directions; and They represent cameras respectively. The pixel coordinates in the x and y directions corresponding to the center point of the captured image.

[0057] Similarly, it can be determined that the line connecting the image of the artificial light source L in the heliostat h and the camera c passes through the other three corner points of the heliostat. , , The pixel coordinates of the image formed by the artificial light source L on the surface of the heliostat h are denoted as follows: , , That is, the line connecting the image of the artificial light source L on the surface of the heliostat h and the camera c passes through the point. hour, The pixel coordinates of the image of the artificial light source L in the heliostat h in the camera. for: .

[0058] Step 3.4: Calculate the geometric center of the light spot based on the pixel coordinates of the image of the artificial light source in the heliostat when the reflected light passes through the vertex of the light spot quadrilateral, determine the radius of the circumcircle based on the maximum distance from the vertex to the center, and then multiply it by a magnification factor greater than 1 to obtain the radius of the equivalent circle.

[0059] The specific method is as follows: the geometric center of the light spot Represented as: ; ; The radius of the circumcircle of the light spot is: ; ; To avoid spot shift caused by factors such as heliostat foundation settlement and strong wind interference, a value slightly larger than the radius of the circumcircle is chosen as the radius of the equivalent circle of the spot. The calculation is as follows: ; in, Indicates the expansion factor. >1, for example, it can be taken as 1.1.

[0060] Step 4, Calibration Combination Screening: Based on the calculation results of Step 3, select the "artificial light source-camera-heliostat" combination where the light spot is completely located within the effective area of ​​the camera image to form an effective calibration combination set;

[0061] The specific method is as follows: If the heliostat h is simultaneously within the coverage area of ​​both the artificial light source L and the camera c, then the heliostat h is within the coverage area of ​​the "artificial light source-camera combination: Lc"; if it is within the coverage area of ​​the "artificial light source-camera combination: Lc", then it is determined whether the image of the artificial light source L in the heliostat h is within the shooting range of the camera c under the boundary conditions; when the following conditions are met, the heliostat h is considered to be calibrated using the "artificial light source-camera combination: Lc", that is: ; ; Where W is the number of pixels in the width of the image captured by camera c, and H is the number of pixels in the height of the image; Record all heliostats that can be calibrated for each "artificial light source-camera combination" to form an effective calibration combination set of "artificial light source-camera-heliostat".

[0062] Step 5, Parallel Calibration Grouping: Treat each valid calibration combination as a node and construct an undirected graph. If two combinations share a heliostat, or share a camera and the light spots may overlap, or there is light occlusion between the heliostats, then establish a connection edge between the corresponding nodes. Divide the nodes into several groups using a graph grouping algorithm to ensure that the nodes in the same group are not connected to each other, so that all combinations in the same group can perform calibration in parallel.

[0063] An undirected graph is created for each camera. Heliostat-light source combinations whose light spots are not adjacent and are not from the same heliostat are grouped together. Then, each group of heliostats is calibrated simultaneously.

[0064] Step 5.1, construct the undirected graph:

[0065] Based on the above steps, the center and size of the light spot in the corresponding camera for each "artificial light source-camera-heliostat combination" can be determined. Treating an "artificial light source-camera-heliostat combination" as a point in a topological graph, an undirected graph can be constructed according to the following rules: If two combinations share a single heliostat or the distance between heliostats is less than a specified threshold. If the nodes in the topology graph corresponding to these two combinations are connected; If two combinations share a camera and the distance between the centers of the light spots is less than the sum of the radii of their equivalent circles, then the nodes in the topology graph corresponding to these two combinations are connected.

[0066] Step 5.2, group the nodes:

[0067] The graph grouping algorithm is a degree-first label propagation algorithm. In the degree-first label propagation algorithm, the degree of a node refers to the number of edges directly connected to that node. The algorithm includes iteratively executing the following steps until all nodes are grouped: (1) Initialize labels for all ungrouped nodes; (2) Prioritize nodes with low degree and that are not connected to each other, and change their labels to group labels; (3) Perform label propagation and mark the neighboring nodes of the group label node as not belonging to the same group; (4) Group nodes with group labels into the same group and remove them from the graph.

[0068] like Figure 3 As shown, the specific execution method is as follows:

[0069] Figure 3 In the diagram, the first number in the circled node is the node number, and the second number is the label added during the algorithm execution.

[0070] (1) Initialization: Assign a label of 0 to all nodes in the undirected graph, such as... Figure 3 As shown in (a); (2) Preferred node labeling: From the nodes with a label of 0, select nodes with a degree less than or equal to 1. If none exist, select the node with the smallest degree, ensuring that there are no connecting edges between the selected nodes. Change the label of these nodes to 1, such as... Figure 3 As shown in (b); (3) First-level neighbor labeling: Change the label of all nodes directly connected to the node whose label has been changed to 1 and whose label is 0 to 2, such as... Figure 3 As shown in (c); (4) Second-level neighbor labeling and state transition: Change the label of all nodes directly connected to the node with label 2 and with label 0 to 3, such as... Figure 3As shown in (d); subsequently, traverse all nodes with label 3, change their label to 1, and during this process, if a node with label 3 is connected to another node with label 3, change the latter's label to 2, as shown in (d). Figure 3 As shown in (e); (5) Iterative convergence: Repeat steps (3) and (4) until the labels of all nodes in the current graph structure are not 0, such as Figure 3 As shown in (f); (6) Grouping and Node Removal: Group all nodes with a label of 1 into the same group and remove these nodes from the undirected graph, such as... Figure 3 As shown in (g); (7) Cyclic grouping: Repeat steps (1) to (6) until all nodes in the undirected graph are assigned to the corresponding groups.

[0071] The "artificial light source-camera-heliostat combination" corresponding to the same group of nodes can be calibrated at the same time. Each group of "artificial light source-camera-heliostat combination" can be calibrated in sequence.

[0072] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A scheduling method for coordinating the calibration of a heliostat using a large-scale artificial light source and a camera, characterized in that, Includes the following steps: Step 1, Camera Coverage Modeling: Calculate the shooting range of each camera in the lens field through coordinate system transformation, and filter out the heliostats located within the camera's field of view; Step 2, Light Source Coverage Modeling: Based on the visible distance and angular parameters of each artificial light source, determine the heliostats within its effective illumination range; Step 3, Calculation of light spot parameters: The results of Step 1 and Step 2 are superimposed to form a candidate set of heliostats that are covered by the same "artificial light source-camera" combination; For each heliostat in the candidate set, the geometric center and equivalent circle radius of its imaging light spot in the corresponding camera image are calculated using the principle of light reflection and the motion model of the heliostat. Step 4, Calibration Combination Screening: Based on the calculation results of Step 3, the "artificial light source-camera-heliostat" combination that has its spot completely located within the effective area of ​​the camera image is screened out to form an effective calibration combination set; Step 5, Parallel Calibration Grouping: Treat each valid calibration combination as a node and construct an undirected graph. If two combinations share a heliostat, or share a camera and the light spots may overlap, or there is light occlusion between the heliostats, then establish a connection edge between the corresponding nodes. Divide the nodes into several groups using a graph grouping algorithm to ensure that the nodes in the same group are not connected to each other, so that all combinations in the same group can perform calibration in parallel.

2. The method according to claim 1, characterized in that, The specific method for step 1 is as follows: Step 1.1, determine the camera's shooting range in the lens field: the coordinates of camera c in the lens field coordinate system are... The optical axis vector is The image captured by camera c has a width of W pixels and a height of H pixels. The area captured by the camera in the field of view is a quadrilateral, and the vertex coordinates are as follows: ； ； ； ； ； ； ； ； in, , They represent cameras respectively. The focal length in the x and y directions; , , , These represent the two-dimensional coordinates of the vertices of the quadrilateral within the shooting area; , , Let be the normalization factors of the three column vectors of the rotation matrix that transforms the lens field coordinate system to the camera coordinate system, expressed as: ； ； ； Step 1.2, Determine if the heliostat is within the camera's field of view: Set the heliostat. The coordinates are The method of ray determination is used to determine whether the heliostat is located within the quadrilateral, i.e., from the heliostat... Draw a ray to the right of the position if the ray intersects one and only one side of the quadrilateral, or passes through one and only one vertex of the quadrilateral and When the size of the heliostat is between the sizes of the y-coordinates of the two other vertices connecting the two sides of the given vertex, then the heliostat... It is located inside the quadrilateral; otherwise, it is located outside the quadrilateral.

3. The method according to claim 1, characterized in that, The specific method for step 2 is as follows: Step 2.1, Determine the coverage area of ​​the artificial light source on the mirror field: Artificial light source The coordinates are Its elliptic cone central axis vector is The two subtended angles corresponding to the major and minor axes of the ellipse are and Curve in the z=0 plane The range is the coverage area of ​​the artificial light source L in the mirror field; Represented as: ； in, , , The normalization factors for the three column vectors of the rotation matrix, which transforms the coordinate system between the artificial light source and the mirror field, are expressed as follows: ； ； ； Step 2.2, determine whether the heliostat is within the field of view covered by the artificial light source: heliostat The coordinates are The visible distance of the artificial light source L is Then, when the following two equations are satisfied, the heliostat... Within the coverage area of ​​the artificial light source L, that is: ； 。 4. The method according to claim 1, characterized in that, In step 3, calculating the geometric center of the light spot and the radius of the equivalent circle includes: Step 3.1: Iteratively solve for the direction of the heliostat normal corresponding to the vertex of the quadrilateral of the light spot; Step 3.2: Calculate the coordinates of the image of the artificial light source in the heliostat in the mirror field when the reflected light passes through the vertex of the quadrilateral of the light spot; Step 3.3: Calculate the pixel coordinates of the image of the artificial light source in the heliostat and the image in the camera when the reflected light passes through the vertices of the light spot quadrilateral; Step 3.4: Calculate the geometric center of the light spot based on the pixel coordinates of the image of the artificial light source in the heliostat when the reflected light passes through the vertex of the light spot quadrilateral, determine the radius of the circumcircle based on the maximum distance from the vertex to the center, and then multiply it by an expansion factor greater than 1 to obtain the radius of the equivalent circle.

5. The method according to claim 4, characterized in that, The specific method for step 3.1 is as follows: a heliostat within the mirror field. The width and length of the mirror are respectively and The points corresponding to the four corners of the mirror are denoted as , , , The coordinates in the mirror coordinate system are respectively , , , Their coordinates in the mirror field coordinate system are denoted as follows: , , , ; When the artificial light source L forms an image on the surface of the heliostat h and the line connecting it to the camera c passes through the four corners of the mirror surface, the corresponding image points in the camera correspond to the four vertices of the parallelogram light spot formed in the image captured by the camera during the calibration of the heliostat h; for points... Its coordinates are obtained iteratively using the following method, with the initial values ​​as follows: ； ； ； ； ； ； ； ； ； ； Among them, subscript This indicates the first iteration. For the second iteration, the parameter index is changed from... Change to And so on for the rest; This indicates that when the artificial light source L forms an image on the surface of the heliostat h, the line connecting it to the camera c passes through the point [point missing]. The normal vector at time, , , This represents the value of the normal vector during the first iteration, i.e., the initial value of the iteration; and They are points Vectors and points pointing to camera c The normalization factor of the vector pointing to the artificial light source L. and Indicates the iterative solution process and The value at the first iteration; , , The line connecting the artificial light source to the camera in the heliostat passes through a point. At that time, the normalization factor of the three column vectors of the rotation matrix for the transformation between the heliostat coordinate system and the mirror field coordinate system. and Indicates the iterative solution process , The value at the first iteration; Point Coordinates in the mirror field coordinate system , , This represents their values ​​during the first iteration; For the iteration ; ； ； ； ； ； ； ； ； ； ； Among them, subscript and They represent the first Second and third The next iteration; when , , All are less than the specified threshold When the time is reached, the iteration ends, and the parameter value of the last iteration is taken as the final solution; Using the same method, the line connecting the image of the artificial light source L on the surface of the heliostat h and the camera c passes through the corresponding points at the other three corners of the mirror surface. , , The direction of the normal and the coordinates of the corner point.

6. The method according to claim 4, characterized in that, The specific method for step 3.2 is as follows: The line connecting the image of the artificial light source L in the mirror surface of the heliostat h and the camera c passes through the point. At that time, the coordinates of the image of the artificial light source L on the surface of the heliostat h in the mirror field are: ； ； ； in, The time corresponds to the line connecting the image of the artificial light source L in the mirror of the heliostat h and the camera c. , , , The situation at these four points; , , These represent the three components of the coordinates of the image of the artificial light source L in the mirror of the heliostat h under the corresponding conditions; , , This represents the three components of the heliostat h-normal vector under the corresponding conditions.

7. The method according to claim 4, characterized in that, The specific method for step 3.3 is as follows: The optical axis vector of camera c in the lens field coordinate system is... The line connecting the image of the artificial light source L in the mirror of the heliostat h and the camera c passes through the point. hour, The pixel coordinates of the image of the artificial light source L in the heliostat h in the camera. for: ； in, , They represent cameras respectively. The focal length in the x and y directions; and They represent cameras respectively. The pixel coordinates in the x and y directions corresponding to the center point of the captured image.

8. The method according to claim 7, characterized in that, The specific method for step 3.4 is as follows: the geometric center of the light spot. Represented as: ； ； The radius of the circumcircle of the light spot is: ； ； Radius of the equivalent circle of the light spot The calculation is as follows: ； in, Indicates the expansion factor. >

1.

9. The method according to claim 8, characterized in that, The specific method for step 4 is as follows: If the heliostat h is simultaneously within the coverage area of ​​both the artificial light source L and the camera c, then the heliostat h is within the coverage area of ​​the "artificial light source-camera combination: Lc"; if it is within the coverage area of ​​the "artificial light source-camera combination: Lc", then it is determined whether the image of the artificial light source L in the heliostat h is within the shooting range of the camera c under the boundary conditions; when the following conditions are met, it is considered that the heliostat h can be calibrated using the "artificial light source-camera combination: Lc", that is: ； ； Where W is the number of pixels in the width of the image captured by camera c, and H is the number of pixels in the height of the image; Record all heliostats that can be calibrated for each "artificial light source-camera combination" to form an effective calibration combination set of "artificial light source-camera-heliostat".

10. The method according to claim 1, characterized in that, In step 5, the graph grouping algorithm is a degree-first label propagation algorithm, where the degree of a node refers to the number of edges directly connected to that node. This algorithm includes iteratively executing the following steps until all nodes are grouped: (1) Initialize labels for all ungrouped nodes; (2) Prioritize nodes with low degree and that are not connected to each other, and change their labels to group labels; (3) Perform label propagation and mark the neighboring nodes of the group label node as not belonging to the same group; (4) Group nodes with group labels into the same group and remove them from the graph.

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