Heliostat calibration method and device, storage medium, computer program product and photo-thermal power generation system

Abstract

The invention discloses a heliostat calibration method and device, a storage medium, a computer program product and a photo-thermal power generation system, and the method comprises the steps: obtaining a first image shot for a target spot, and determining a first pixel position of the target spot in the first image; acquiring a second image shot for a mirror image in the heliostat, and determining a second pixel position of a central point of a sunglass image in the second image; based on the target transformation parameter, transforming the first pixel position to an image coordinate system to which the second image belongs, and obtaining a mapping pixel position; if the distance between the second pixel position and the mapping pixel position is greater than a preset first distance threshold, calibrating the heliostat based on the second pixel position and the mapping pixel position, and then acquiring a second image shot for a mirror image in the calibrated heliostat, the distance between the mapping pixel position and the re-determined second pixel position is smaller than or equal to the first distance threshold value. According to the scheme, the calibration precision of the heliostat can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of photothermal power generation, and in particular to a heliostat calibration method and device, a storage medium, a computer program product, and a photothermal power generation system. Background Art

[0002] With the continuous development of renewable energy, solar thermal power generation is an important direction of new energy utilization, mainly including three systems: trough, tower, and dish (disk). Among them, the tower solar thermal power generation system has higher tracking complexity and accuracy requirements than other systems such as trough and butterfly.

[0003] Heliostat is a component of a tower solar thermal power generation system. Its function is to reflect sunlight beams to a fixed position of a receiving tower to generate heat, which is then converted into electricity by the receiving tower. Since the position of the sun in the sky is constantly changing throughout the year and even at every moment, the heliostat also needs to constantly adjust its angle to track the sun and reflect sunlight to the receiver of the receiving tower. The closer the sunlight reflected by the heliostat is to the center point of the receiver, the higher the power generation efficiency. Therefore, calibrating or adjusting the position of the heliostat is the key to the tower solar thermal power generation system.

[0004] However, the existing heliostat calibration method has limited calibration accuracy, which affects the power generation efficiency. Summary of the invention

[0005] The problem solved by the embodiments of the present invention is: how to effectively improve the calibration accuracy of the heliostat.

[0006] To solve the above problem, an embodiment of the present invention provides a heliostat calibration method, the heliostat calibration method comprising: acquiring a first image shot for a target point, and determining a first pixel position of the target point in the first image; acquiring a second image shot for a mirror in the heliostat, and determining a second pixel position of a center point of the mirror of the sun in the second image, wherein the mirror in the heliostat at least includes the mirror of the sun; based on a target transformation parameter, transforming the first pixel position from an image coordinate system to which the first image belongs to an image coordinate system to which the second image belongs to obtain a corresponding mapping pixel position, wherein the target transformation parameter is used to indicate a coordinate space transformation relationship between an image coordinate system to which the first image belongs and an image coordinate system to which the second image belongs; determining whether a distance between the second pixel position in the second image and the mapping pixel position is less than or equal to a preset first distance threshold; if the determination result is no, calibrating the heliostat based on the second pixel position and the mapping pixel position, then acquiring a second image shot for the mirror in the calibrated heliostat, and re-determining a second pixel position corresponding to the center point of the mirror of the sun in the second image, until the distance between the mapping pixel position and the re-determined second pixel position is less than or equal to the first distance threshold.

[0007] Optionally, the target transformation parameter is determined in the following manner: performing a first operation, the first operation comprising: adjusting the heliostat until a sample target point on a receiving tower coincides with a position of a light spot formed on the receiving tower after sunlight is reflected by the heliostat; obtaining a first sample image shot for the sample target point on the receiving tower, and determining an actual pixel position of the sample target point in the first sample image, recorded as a first sample position; obtaining a second sample image shot for the mirror image in the adjusted heliostat, and determining an actual pixel position of a center point of the mirror image of the sun in the second sample image, recorded as a second sample position; determining the target transformation parameter based on multiple groups of first sample positions and second sample positions determined after performing the first operation multiple times; wherein the position of the sample target point for each execution of the first operation is different.

[0008] Optionally, adjusting the heliostat until the sample target point on the receiving tower coincides with the position of a light spot formed on the receiving tower after the sunlight is reflected by the heliostat, includes: acquiring a target image shot for the sample target point and the light spot; respectively determining actual pixel positions of the sample target point and the light spot in the target image, recorded as a first target position and a second target position; judging whether the first target position and the second target position in the target image coincide with each other; if the judgment result is no, adjusting the heliostat, and acquiring a target image shot for the sample target point and the light spot formed on the receiving tower after the sunlight is reflected by the adjusted heliostat, until the first target position and the second target position in the target image coincide with each other.

[0009] Optionally, the heliostat calibration method is implemented by a heliostat calibration device; the acquiring a first image shot for the target target and determining a first pixel position of the target target in the first image includes: acquiring a first image shot for the target target and determining an actual pixel position of the target target in the first image; judging whether a distance between the actual pixel position of the target target and a center point of the first image is less than or equal to a preset second distance threshold; if the judgment result is no, adjusting the heliostat calibration device based on the actual pixel position of the target target and the center point of the first image, then acquiring a first image re-shot for the target target, and re-determining the actual pixel position of the target target in the first image until the distance between the actual pixel position and the center point of the first image is less than or equal to the second distance threshold, and using the actual pixel position of the target target determined for the last time as the first pixel position of the target target in the first image; wherein the spatial position of the first image re-shot for the target target after the heliostat calibration device is adjusted is adjusted accordingly.

[0010] Optionally, calibrating the heliostat is achieved by controlling the movement of the heliostat; calibrating the heliostat based on the second pixel position and the mapped pixel position includes: determining a distance between the second pixel position and the mapped pixel position, recorded as a target distance; if the target distance is less than or equal to a preset third distance threshold, reducing a moving speed of the heliostat, and calibrating the heliostat using the reduced moving speed; wherein the third distance threshold is greater than or equal to the first distance threshold.

[0011] Optionally, the smaller the target distance is, the smaller the lowered moving speed of the heliostat is.

[0012] Optionally, determining the second pixel position of the center point of the sun's mirror image in the second image includes: determining the maximum brightness value among the brightness values ​​of each pixel in the second image; and determining the second pixel position of the center point of the sun's mirror image in the second image based on the maximum brightness value and a preset target brightness range.

[0013] Optionally, based on the maximum brightness value and a preset target brightness range, determining the second pixel position of the center point of the sun's mirror image in the second image includes: judging whether the maximum brightness value is within the target brightness range; if the maximum brightness value exceeds the target brightness range, adjusting the exposure time of shooting, and obtaining a second image retaken based on the adjusted exposure time, until the maximum brightness value among the brightness values ​​of each pixel of the retaken second image is within the target brightness range, and taking the position of the pixel to which the maximum brightness value among the brightness values ​​of each pixel of the most recently shot second image belongs as the second pixel position of the center point of the sun's mirror image in the second image.

[0014] Optionally, the two endpoint brightness values ​​of the target brightness range are respectively recorded as a first brightness threshold and a second brightness threshold, and the first brightness threshold is less than the second brightness threshold; if the maximum brightness value exceeds the target brightness range, the exposure time of shooting is adjusted, including: if the maximum brightness value is greater than or equal to the second brightness threshold, reducing the exposure time of shooting; if the maximum brightness value is less than or equal to the first brightness threshold, increasing the exposure time of shooting.

[0015] The embodiment of the present invention further provides a heliostat calibration device, comprising: a first pixel position determination module, used to obtain a first image shot for a target target point, and determine a first pixel position of the target target point in the first image; a second pixel position determination module, used to obtain a second image shot for a mirror image in the heliostat, and determine a second pixel position of a center point of the mirror image of the sun in the second image, wherein the mirror image in the heliostat includes at least the mirror image of the sun; a coordinate space transformation module, used to transform the first pixel position from an image coordinate system to which the first image belongs to to an image coordinate system to which the second image belongs based on a target transformation parameter, to obtain a corresponding mapping pixel position, wherein the target transformation parameter is used indicating a coordinate space transformation relationship between an image coordinate system to which the first image belongs and an image coordinate system to which the second image belongs; a judging module, used to judge whether the distance between the second pixel position in the second image and the mapped pixel position is less than or equal to a preset first distance threshold; a heliostat calibration module, used to calibrate the heliostat based on the second pixel position and the mapped pixel position if the judgment result is no, then obtain a second image taken for the mirror image in the calibrated heliostat, and redetermine a second pixel position corresponding to the center point of the mirror image of the sun in the second image, until the distance between the mapped pixel position and the redetermined second pixel position is less than or equal to the first distance threshold.

[0016] An embodiment of the present invention further provides a storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of the heliostat calibration method are executed.

[0017] An embodiment of the present invention further provides a heliostat calibration device, comprising a memory and a processor, wherein the memory stores a computer program that can be run on the processor, and the processor executes the steps of the heliostat calibration method when running the computer program.

[0018] An embodiment of the present invention further provides a solar thermal power generation system, comprising the above-mentioned heliostat calibration device, and also comprising: a heliostat and a receiving tower; the heliostat calibration device corresponds one-to-one to the heliostat, and the receiving tower includes the above-mentioned target point.

[0019] An embodiment of the present invention further provides a computer program product, including a computer program, which executes the steps of the above heliostat calibration method when executed by a processor.

[0020] Compared with the prior art, the technical solution of the embodiment of the present invention has the following advantages:

[0021] In an embodiment of the present invention, a first image shot for a target point is obtained, and a first pixel position of the target point in the first image is determined; a second image shot for a mirror in a heliostat is obtained, and a second pixel position of a center point of the mirror of the sun in the second image is determined; based on a coordinate space transformation relationship between an image coordinate system to which the first image belongs and an image coordinate system to which the second image belongs (i.e., the target transformation parameter), a first pixel position of the target point in the first image is transformed from an image coordinate system to which the first image belongs to an image coordinate system to which the second image belongs, to obtain a mapping pixel position corresponding to the first pixel position in the second image; and then the heliostat is calibrated so that the second pixel position is as close as possible to the mapping pixel position, so that the sunlight reflected by the heliostat reaches the light of the second image as parallel as possible to the target point. In this way, in actual application, the incident position of the sunlight reflected by the heliostat on the receiving tower is close to or coincides with the position of the target point on the receiving tower, so that the sunlight reflected by the heliostat can be reflected to a receiver of the receiving tower to achieve light-to-heat conversion.

[0022] From the above, by adopting the present embodiment, there is no need to specially set the imaging plane to which the first image belongs and the imaging plane to which the second image belongs to strictly satisfy the condition of being parallel and having overlapping formats, and there is no need to set the midpoint of the line between the center point of the first image and the center point of the second image as the calibration point. Instead, based on the coordinate space transformation relationship between the image coordinate system to which the first image belongs and the image coordinate system to which the second image belongs, the coordinate space transformation is performed on the pixel position corresponding to the target point and the heliostat calibration is performed, which helps to avoid the calibration deviation caused by the change of the relative position relationship between the first imaging plane and the second imaging plane, and improves the calibration accuracy.

[0023] Furthermore, during the use of the heliostat calibration device, the relative positional relationship between the image sensor used to capture the first image and the image sensor used to capture the second image may change, that is, the coordinate space transformation relationship between the image coordinate system to which the first image belongs and the image coordinate system to which the second image belongs may change. Compared with using historically calibrated, fixed target transformation parameters (for example, target transformation parameters calibrated based on the imaging plane of the first image sensor and the imaging plane of the second image sensor after the heliostat calibration device leaves the factory), this embodiment can efficiently and accurately obtain the latest target transformation parameters at any appropriate time according to actual needs, thereby further ensuring the calibration accuracy of the heliostat. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a flow chart of a heliostat calibration method in an embodiment of the present invention;

[0025] Figure 2 is a schematic diagram of calibrating a heliostat using a heliostat calibration device in a typical application scenario of an embodiment of the present invention;

[0026] Figure 3 yes Figure 1 A flowchart of a specific implementation of step S11;

[0027] Figure 4 is a flowchart of a specific implementation method for determining target transformation parameters in an embodiment of the present invention;

[0028] Figure 5 yes Figure 1 A flowchart of a specific implementation of step S15;

[0029] Figure 6 It is a structural schematic diagram of a heliostat calibration device in an embodiment of the present invention. DETAILED DESCRIPTION

[0030] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0031] Reference Figure 1 , Figure 1 is a flow chart of a heliostat calibration method in an embodiment of the present invention. Specifically, the method may include:

[0032] Step S11: acquiring a first image shot for a target point, and determining a first pixel position of the target point in the first image;

[0033] Step S12: acquiring a second image taken for the mirror image in the heliostat, and determining a second pixel position of a center point of the mirror image of the sun in the second image, wherein the mirror image in the heliostat at least includes the mirror image of the sun;

[0034] Step S13: based on a target transformation parameter, transforming the first pixel position from the image coordinate system to which the first image belongs to the image coordinate system to which the second image belongs to obtain a corresponding mapping pixel position, wherein the target transformation parameter is used to indicate a coordinate space transformation relationship between the image coordinate system to which the first image belongs and the image coordinate system to which the second image belongs;

[0035] Step S14: determining whether the distance between the second pixel position in the second image and the mapping pixel position is less than or equal to a preset first distance threshold;

[0036] If the judgment result is no, that is, the distance between the second pixel position and the mapped pixel position is greater than the first distance threshold, step S15 is executed.

[0037] Step S15: calibrating the heliostat based on the second pixel position and the mapped pixel position.

[0038] After calibrating the heliostat, returning to re-execute step S12 until the distance between the second pixel position in the second image and the mapping pixel position is less than or equal to the first distance threshold. In the process of re-executing step S12, the second image obtained is a second image re-photographed for the mirror image in the calibrated heliostat.

[0039] Further, if the judgment result of step S14 is yes, that is, the distance between the second pixel position in the second image and the mapped pixel position is less than or equal to the first distance threshold, there is no need to calibrate the heliostat. Further, since the position of the sun changes in real time in actual applications, and the heliostat calibration device used to perform the heliostat calibration method may also be slightly offset, it is possible to directly return to step S11 without calibrating the heliostat to continue the next round of calibration. In other words, the heliostat calibration method of the embodiment of the present invention can be executed cyclically.

[0040] In a specific implementation, the above heliostat calibration method can be Figure 2 The heliostat calibration 20 device shown is implemented. Figure 2 , the specific implementation process, relevant principles and technical effects of the above heliostat calibration method are described in detail. It should be pointed out that Figure 2 The specific structures of the heliostat calibration device 20 and the receiving tower 50 shown in the figure do not constitute a limitation on the specific implementation scheme of the heliostat calibration method of the present application. In other words, the heliostat calibration method of the present application adopts Figure 2 The heliostat calibration device 20 and the receiving tower 50 shown in the figure may also be implemented based on the structure of other appropriate calibration devices or receiving towers having the same or similar calibration principles.

[0041] like Figure 2 As shown, a schematic diagram of calibrating a heliostat using a heliostat calibration device 20 in a typical application scenario of an embodiment of the present invention is provided.

[0042] The heliostat calibration device 20 may include: a calibration body 30, a first image sensor 32 and a second image sensor 32, and may also include a calibration body bracket 37. Wherein:

[0043] The calibration body 30 includes a first optical surface 34 and a second optical surface 35 which are arranged opposite to each other, and may also include a light shielding surface 33. The first optical surface 34 may be provided by a first lens, and the second optical surface 35 may be provided by a second lens. In a specific implementation, the calibration body 30 may have a variety of shapes, for example, Figure 2 The calibration body 30 may be a cylinder. In this case, the first optical surface 34 and the second optical surface 35 are equivalent to the upper and lower surfaces of the cylinder, and the light shielding surface 33 is equivalent to the cylindrical surface of the cylinder.

[0044] In some embodiments, the calibration body may also be in other shapes, such as a cuboid, a cube, etc., with a first optical surface 34 and a second optical surface 35, which are not limited here. Specifically, the first optical surface 34 and the second optical surface 35 may be arranged to be parallel to each other.

[0045] The first image sensor 31 and the second image sensor 32 are located on the calibration body 30; the first image sensor 31 has a first imaging plane 301 facing the first optical surface 34, and the second image sensor 32 has a second imaging plane 302 facing the second optical surface 35; the first imaging plane 301 is arranged opposite to the second imaging plane 302. Specifically, the first image sensor 31 and the second image sensor 32 can be arranged back to back or with a certain gap, and the specific size of the gap can be set according to actual conditions.

[0046] The first image sensor 31 is used to capture a first image for the target point A of the receiving tower 50, and the second image sensor 32 is used to capture a second image for the mirror image in the heliostat 60, wherein the mirror image in the heliostat 60 at least includes a mirror image of the sun 40 (also called a "sun image"). The first imaging plane 301 is an imaging plane to which the first image belongs, and the second imaging plane 302 is an imaging plane to which the second image belongs. The first imaging plane 301 faces the target point A, and the second imaging plane 302 faces the heliostat 60. More specifically, the image coordinate system to which the first image belongs is a coordinate system constructed based on the first imaging plane 301; the image coordinate system to which the second image belongs is a coordinate system constructed based on the second imaging plane 302.

[0047] Furthermore, a receiver 51 may be provided on the receiving tower 50, and the receiver 51 is used to receive the reflected light of the sun during the actual light-to-heat conversion process. A target plate 52 may also be provided on the receiving tower 50, and a plurality of target points may be provided on the target plate 52, and a target point may be selected arbitrarily from the plurality of target points as the target point A for calibrating the heliostat. In order to obtain higher power generation efficiency, the target point A may be set as the center point of the receiver 51.

[0048] After acquiring the first image, the first pixel position of the target point A in the first image can be determined; after acquiring the second image, the second pixel position of the center point of the mirror image of the sun 40 in the second image can be determined.

[0049] In an existing calibration scheme, the first imaging plane 301 and the second imaging plane 302 are set to be parallel and overlapped, and the midpoint of the line between the center point of the first image and the center point of the second image is directly used as the calibration point and the position of the calibration point is pre-stored; the heliostat can be calibrated so that the first pixel position of the target target point A on the receiving tower 50 in the first image and the second pixel position of the mirror image of the sun 40 in the heliostat 60 in the second image are symmetrical around the calibration point, so that the sunlight reflected by the heliostat 60 can reach the second imaging plane 302 in parallel with the target target point A of the receiving tower 50, and then the incident position of the sunlight reflected by the heliostat 60 on the receiving tower 50 is close to or overlaps with the position of the target target point A on the receiving tower 50, so that the sunlight reflected by the heliostat 60 can be reflected to the receiver 51 of the receiving tower 50 to achieve light-to-heat conversion.

[0050] It should be pointed out that the premise for the above existing calibration scheme to achieve high-precision calibration is that the first imaging plane 301 and the second imaging plane 302 meet the conditions of being parallel and completely overlapping in format. However, in actual use, affected by various factors, especially after the heliostat calibration device has been running for a long time, the positional relationship between the first imaging plane 301 and the second imaging plane 302 may not strictly meet the conditions of being parallel and completely overlapping in format. For example, there may be an angle or offset between the first imaging plane 301 and the second imaging plane 302. In this case, the above calibration scheme of judging whether the position is symmetrical around the pre-stored calibration point will cause deviation in the calibration result and low calibration accuracy.

[0051] In comparison, in the embodiment of the present invention, based on the coordinate space transformation relationship between the image coordinate system to which the first image belongs and the image coordinate system to which the second image belongs (i.e., the target transformation parameter), the first pixel position of the target point A in the first image is transformed from the image coordinate system to which the first image belongs to the image coordinate system to which the second image belongs to obtain the mapping pixel position corresponding to the first pixel position in the second image; then, by calibrating the heliostat, the second pixel position of the mirror image of the sun 40 in the heliostat 60 in the second image is as close as possible to the image on the receiving tower 50. The mapping pixel position corresponding to the target target point A in the second image (that is, the distance between the second pixel position in the second image and the mapping pixel position is less than or equal to the preset first distance threshold), so that the sunlight reflected by the heliostat 60 reaches the second imaging plane 302 as parallel as possible to the target target point A. In this way, in actual application, the incident position of the sunlight reflected by the heliostat 60 on the receiving tower 50 is close to or coincides with the position of the target target point A on the receiving tower 50, so that the sunlight reflected by the heliostat 60 can be reflected to the receiver 51 of the receiving tower 50 to achieve light-to-heat conversion.

[0052] From the above, by adopting the solution of the embodiment of the present invention, there is no need to specially set the first imaging plane and the second imaging plane to strictly meet the conditions of being parallel and having overlapping formats, and there is no need to set the midpoint of the line between the center point of the first image and the center point of the second image as the calibration point. Instead, based on the coordinate space transformation relationship between the image coordinate system to which the first image belongs and the image coordinate system to which the second image belongs, the coordinate space transformation is performed on the pixel position corresponding to the target point and the heliostat calibration is performed, which helps to avoid the calibration deviation caused by the change of the relative position relationship between the first imaging plane and the second imaging plane, and improves the calibration accuracy.

[0053] Furthermore, the calibration scheme of the embodiment of the present invention can at least be applicable to the following situations: (1) the first imaging plane and the second imaging plane are parallel to each other and their formats overlap, and the line between the center point of the first image and the center point of the second image is perpendicular to the first imaging plane and the second imaging plane; (2) the first imaging plane and the second imaging plane are parallel to each other but their formats do not completely overlap; (3) there is a certain angle between the first imaging plane and the second imaging plane.

[0054] It is understandable that the first distance threshold cannot be set too large, otherwise it will affect the accuracy of calibration; the first distance cannot be set too small, otherwise it will lead to reduced efficiency of calibration.

[0055] In a specific implementation, in order to improve the calibration efficiency and calibration accuracy, the heliostat calibration device 20 may further include a control component (not shown) for determining whether the distance between the second pixel position in the second image and the mapped pixel position is less than or equal to the first distance threshold, and if the determination result of step S14 is no, calibrate the heliostat based on the second pixel position and the mapped pixel position until the distance between the mapped pixel position and the re-determined second pixel position is less than or equal to the first distance threshold. The first control component may be disposed between the first image sensor 31 and the second image sensor 32 of the heliostat calibration device 20.

[0056] The control component may be in communication connection with the heliostat support 601 , and the heliostat support 601 moves (eg, moves in a horizontal direction, a vertical direction, or other appropriate directions) the heliostat 60 under the control of the control component to achieve calibration of the heliostat 60 .

[0057] In a specific implementation of the step S11, the actual pixel position of the target point in the first image (ie, the actual imaged pixel position) may be directly used as the first pixel position.

[0058] In another specific implementation of step S11, the heliostat calibration device may be adjusted (for example, the control component of the heliostat calibration device is used for adjustment) so that the actual pixel position of the target point in the first image is as close as possible to the center point of the first image, and the actual pixel position close to the center point of the first image is used as the first pixel position of the target point in the first image. For details of this implementation, see Figure 3 and the description below.

[0059] Reference Figure 3 , Figure 3 yes Figure 1 FIG. 4 is a flowchart of a specific implementation of step S11 in FIG. 4 . In this implementation, step S11 may include the following steps S111 to S113.

[0060] In step S111, a first image captured for a target point is acquired, and an actual pixel position of the target point is determined in the first image.

[0061] The actual pixel position of the target point specifically refers to the pixel position where the target point is actually imaged in the first image.

[0062] In step S112, it is determined whether the distance between the actual pixel position of the target point and the center point of the first image is less than or equal to a preset second distance threshold.

[0063] In some non-limiting embodiments, the second distance threshold may be set to 0 or a suitable value close to 0.

[0064] If the judgment result is no, step S113 is executed; if the judgment result is yes, the actual pixel position of the target point in the first image can be used as the first pixel position of the target point in the first image.

[0065] In step S113, the heliostat calibration device is adjusted based on the actual pixel position of the target point and the center point of the first image.

[0066] After adjusting the heliostat calibration device, return to re-execute step S111 until the distance between the actual pixel position of the target point in the first image and the center point of the first image is less than or equal to the second distance threshold. At this time, the actual pixel position of the target point determined last time can be used as the first pixel position of the target point in the first image.

[0067] It can be understood that after the heliostat calibration device is adjusted, the image sensor (corresponding to Figure 2 The position of the first image sensor 31 in the image sensor 31 changes accordingly, and therefore, the spatial position of the first image re-photographed for the target target is also adjusted accordingly, thereby changing the pixel position of the target target actually imaged in the first image.

[0068] It should be pointed out that, in the imaging process of the image sensor, since the imaging quality at the center point of the image is often least affected by factors such as lens distortion, correspondingly, the accuracy of the first pixel position of the target point in the first image is higher. Therefore, in an embodiment of the present invention, before adjusting the heliostat, the position of the heliostat calibration device is adjusted so that the actual pixel position of the target point in the first image is as close as possible to the center point of the first image, which helps to improve the accuracy of the first pixel position and its corresponding mapping pixel position, thereby improving the calibration accuracy of the heliostat.

[0069] Further, continue to refer to Figure 1In step S12, determining the second pixel position of the center point of the sun's mirror image in the second image may specifically include: determining the maximum brightness value among the brightness values ​​of each pixel in the second image; and determining the second pixel position of the center point of the sun's mirror image in the second image based on the maximum brightness value and a preset target brightness range.

[0070] The second pixel position may be the pixel position where the center point of the sun's mirror image is actually imaged in the second image.

[0071] Furthermore, based on the maximum brightness value and a preset target brightness range, the second pixel position of the center point of the sun's mirror image in the second image is determined, including: judging whether the maximum brightness value is within the target brightness range; if the maximum brightness value exceeds the target brightness range, adjusting the exposure time of shooting, and obtaining a second image retaken based on the adjusted exposure time, until the maximum brightness value among the brightness values ​​of each pixel of the retaken second image is within the target brightness range, and taking the position of the pixel to which the maximum brightness value among the brightness values ​​of each pixel of the most recently shot second image belongs as the second pixel position of the center point of the sun's mirror image in the second image.

[0072] In a specific implementation, the two endpoint brightness values ​​of the target brightness range are respectively recorded as the first brightness threshold and the second brightness threshold, and the first brightness threshold is less than the second brightness threshold; if the maximum brightness value exceeds the target brightness range, the exposure time of the shooting is adjusted, including: if the maximum brightness value is greater than or equal to the second brightness threshold, the exposure time of the shooting is reduced; if the maximum brightness value is less than or equal to the first brightness threshold, the exposure time of the shooting is increased.

[0073] It can be understood that, in the process of capturing an image, the longer the exposure time of the image sensor is, the greater the brightness value of each pixel in the captured image, and when the exposure time is too long, in addition to the sun image in the heliostat, the mirror images of other objects in the heliostat will also be brighter in the second image, thereby interfering with the pixel position corresponding to the center point of the mirror image of the sun accurately located in the second image (i.e., the second pixel position); on the contrary, the shorter the exposure time of the image sensor is, the smaller the brightness value of each pixel in the captured image, and when the exposure time is too short, both the sun image in the heliostat and the mirror images of other objects will be darker in the second image, and at this time, the mirror images of other objects will also interfere with the pixel position corresponding to the center point of the mirror image of the sun accurately located in the second image.

[0074] To solve the above problem, in an embodiment of the present invention, the target brightness interval is appropriately set, and it is determined whether the maximum brightness value among the brightness values ​​of each pixel in the second image is within the target brightness interval; and based on the comparison result between the maximum brightness value and the brightness values ​​at both end points of the target brightness interval, starting from the aspect of improving image quality, the exposure time of the image sensor is appropriately increased or decreased to optimize the quality of the captured second image, avoid the influence of other interfering targets in the heliostat as much as possible, and ensure that the maximum brightness value of each pixel in the second image is always within the target brightness interval.

[0075] From the above, compared with adopting other methods to determine the second pixel position (for example, when the maximum brightness value exceeds the target brightness range, without changing the exposure time, selecting a pixel position from a plurality of pixel positions with larger brightness values ​​in the second image as the second pixel position), adopting this embodiment helps to achieve that the brightest pixel position in the second image is the pixel position corresponding to the mirror image of the sun, rather than the pixel position corresponding to other interference targets in the heliostat, thereby improving the positioning accuracy of the second pixel position, and further improving the efficiency and accuracy of subsequent calibration of the heliostat.

[0076] In a specific implementation, the first brightness threshold and / or the second brightness threshold is determined based on the bit width of the second image. The larger the bit width of the second image, the larger the first brightness threshold and / or the second brightness threshold.

[0077] Specifically, the first brightness threshold is determined by the following formula:

[0078] Y1=w1×(2 x -1);

[0079] The second brightness threshold is determined by the following formula:

[0080] Y2=w2×(2 x -1);

[0081] Among them, Y1 represents the first brightness threshold, Y2 represents the second brightness threshold, x represents the bit width of the second image, w1 represents a preset first adjustment coefficient, w2 represents a preset second adjustment coefficient, and w1<w2.

[0082] In some non-limiting embodiments, the bit width of the second image may be 8 bits, the first adjustment coefficient may be selected from the interval [0.8, 0.92], and the second adjustment coefficient may be selected from the interval [0.95, 1]. For example, the first brightness threshold may be set to 230, and the second brightness threshold may be set to 255.

[0083] Reference Figure 4 , Figure 4 It is a flowchart of a specific implementation method of determining the target transformation parameters in an embodiment of the present invention; in this implementation method, the target transformation parameters can be determined by using the following steps S41 to S42.

[0084] In step S41, a first operation is performed, which includes: adjusting the heliostat until the sample target point on the receiving tower coincides with the position of the light spot formed on the receiving tower after the sunlight is reflected by the heliostat; obtaining a first sample image shot for the sample target point on the receiving tower, and determining an actual pixel position of the sample target point in the first sample image, which is recorded as a first sample position; obtaining a second sample image shot for the mirror image in the adjusted heliostat, and determining an actual pixel position of the center point of the mirror image of the sun in the second sample image, which is recorded as a second sample position.

[0085] Further, the heliostat is adjusted until the sample target point on the receiving tower coincides with the position of the light spot formed on the receiving tower after the sunlight is reflected by the heliostat, including: obtaining a target image shot for the sample target point and the light spot; respectively determining the actual pixel positions of the sample target point and the light spot in the target image, recorded as the first target position and the second target position; judging whether the first target position and the second target position in the target image coincide; if the judgment result is no, adjusting the heliostat, and obtaining a target image shot for the sample target point and the light spot formed on the receiving tower after the sunlight is reflected by the adjusted heliostat, until the first target position and the second target position in the target image coincide.

[0086] In step S42, the target transformation parameters are determined based on multiple groups of first sample positions and second sample positions determined after performing the first operation multiple times.

[0087] Among them, the positions of the sample targets for each execution of the first operation are different. In other words, a plurality of sample targets at different positions can be set on the receiving tower. In a specific implementation, for a solar thermal power generation system including a plurality of heliostat calibration devices and a plurality of heliostats (the plurality of heliostat calibration devices correspond one to one to a plurality of heliostats), a number of calibration markers can be set at appropriate positions on the receiving tower, and the markers can be regular polyhedral prisms (such as regular dodecahedral prisms, regular hexagonal prisms, etc.), and a suitable number of sample targets are set on each face of the regular polyhedral prism, so as to realize simultaneous calibration of multiple heliostats based on sample targets on multiple faces, thereby improving the calibration efficiency of each heliostat in the solar thermal power generation system, and thus greatly improving the overall power generation efficiency.

[0088] Among them, the target transformation parameters may include a rotation matrix and / or a translation vector, the rotation matrix is ​​used to indicate the rotation transformation relationship between the image coordinate system to which the first image belongs and the image coordinate system to which the second image belongs, and the translation vector is used to indicate the translation transformation relationship between the image coordinate system to which the first image belongs and the image coordinate system to which the second image belongs.

[0089] Regarding the specific implementation scheme of determining the target transformation parameters based on multiple groups of first sample positions and second sample positions, it can be implemented using existing technologies.

[0090] In the embodiment of the present invention, by setting a plurality of sample target points on the receiving tower, utilizing the positional coincidence relationship between the sample target points on the receiving tower and the light spot formed on the receiving tower after the sunlight is reflected by the heliostat during the solar thermal power generation process, and using the image acquisition function of the heliostat calibration device to determine a plurality of groups of first sample pixel positions and second sample pixel positions, the coordinate space transformation relationship (i.e., target transformation parameters) between the image coordinate system to which the first image belongs and the image coordinate system to which the second image belongs can be obtained conveniently and in real time.

[0091] Furthermore, the scheme for determining the target transformation parameters may be executed once per interval of a preset duration, that is, the target transformation parameters may be determined per interval of a preset duration, or may be determined at any appropriate time, or may be determined before each execution of step S13.

[0092] It can be understood that, since the relative positional relationship between the image sensor used to capture the first image and the image sensor used to capture the second image may change during the use of the heliostat calibration device, the coordinate space transformation relationship between the image coordinate system to which the first image belongs and the image coordinate system to which the second image belongs may also change accordingly. Compared with using historically calibrated, fixed target transformation parameters (for example, target transformation parameters calibrated based on the imaging plane of the first image sensor and the imaging plane of the second image sensor after the heliostat calibration device leaves the factory), this embodiment can efficiently and accurately obtain the latest target transformation parameters at any appropriate time according to actual needs, thereby further ensuring the calibration accuracy of the heliostat.

[0093] Reference Figure 5 , Figure 5 yes Figure 1 Flow chart of a specific implementation of step S15 in the embodiment; in this implementation, the calibration of the heliostat is achieved by controlling the movement of the heliostat; the step S15 may specifically include the following steps S151 to S153.

[0094] In step S151, the distance between the second pixel position and the mapped pixel position is determined and recorded as the target distance.

[0095] In step S152, it is determined whether the target distance is less than or equal to a preset third distance threshold.

[0096] If the target distance is less than or equal to the third distance threshold, step S153 is executed; further, if the target distance is greater than the third distance threshold, the moving speed of the heliostat may be kept unchanged (i.e., the heliostat continues to be moved at the original moving speed) to calibrate the heliostat.

[0097] In step S153, the moving speed of the heliostat is reduced, and the heliostat is calibrated using the reduced moving speed.

[0098] Furthermore, the smaller the target distance is, the smaller the lowered moving speed of the heliostat is.

[0099] It can be understood that the goal of calibrating the heliostat may be to make the second pixel position as close to or even coincide with the mapping pixel position as possible (that is, the target distance is as small as possible or even 0). Therefore, in the embodiment of the present invention, when the target distance gradually decreases to be less than or equal to a preset third distance threshold as the calibration process progresses, the moving speed of the heliostat is reduced, which helps to further improve the calibration accuracy.

[0100] It is understandable that the third distance threshold cannot be set too large, otherwise the calibration accuracy will be affected; the third distance threshold cannot be set too small, otherwise the calibration efficiency will be reduced.

[0101] Reference Figure 6 , Figure 6 : is a schematic diagram of the structure of a heliostat calibration device in an embodiment of the present invention. The heliostat calibration device may include:

[0102] A first pixel position determination module 61 is used to obtain a first image shot for a target point and determine a first pixel position of the target point in the first image;

[0103] A second pixel position determination module 62 is used to obtain a second image taken for the mirror image in the heliostat, and determine a second pixel position of the center point of the mirror image of the sun in the second image, wherein the mirror image in the heliostat includes at least the mirror image of the sun;

[0104] a coordinate space transformation module 63, configured to transform the first pixel position from the image coordinate system to which the first image belongs to into the image coordinate system to which the second image belongs based on a target transformation parameter, so as to obtain a corresponding mapping pixel position, wherein the target transformation parameter is used to indicate a coordinate space transformation relationship between the image coordinate system to which the first image belongs and the image coordinate system to which the second image belongs;

[0105] A judging module 64, configured to judge whether the distance between the second pixel position in the second image and the mapped pixel position is less than or equal to a preset first distance threshold;

[0106] The heliostat calibration module 65 is configured to, if the judgment result of the judgment module 64 is no, calibrate the heliostat based on the second pixel position and the mapped pixel position, then obtain a second image taken for the mirror image in the calibrated heliostat, and redetermine a second pixel position corresponding to the center point of the mirror image of the sun in the second image, until the distance between the mapped pixel position and the redetermined second pixel position is less than or equal to the first distance threshold.

[0107] For the principle, specific implementation and beneficial effects of the heliostat calibration device, please refer to the previous article and Figures 1 to 5 The relevant description about the heliostat calibration method shown in any embodiment will not be repeated here.

[0108] The embodiment of the present invention further provides a storage medium, such as a computer-readable storage medium, on which a computer program is stored, and the computer program is executed by a processor. Figures 1 to 5 The steps of the heliostat calibration method shown in any embodiment. The computer-readable storage medium may include a non-volatile memory or a non-transitory memory, and may also include an optical disk, a mechanical hard disk, a solid-state hard disk, and the like.

[0109] Specifically, in the embodiment of the present invention, the processor may be a central processing unit (CPU), and the processor may also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field programmable gate arrays (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0110] It should also be understood that the memory in the embodiments of the present application may be a volatile memory or a non-volatile memory, or may include both volatile and non-volatile memories. Among them, the non-volatile memory may be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a flash memory. The volatile memory may be a random access memory (RAM), which is used as an external cache. By way of example but not limitation, many forms of random access memory (RAM) are available, such as static RAM (SRAM), dynamic random access memory (DRAM), synchronous DRAM (SDRAM), double data rate synchronous dynamic random access memory (DDR SDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous link DRAM (SLDRAM) and direct rambus RAM (DR RAM).

[0111] The embodiment of the present invention further provides a heliostat calibration device, comprising a memory and a processor, wherein the memory stores a computer program that can be run on the processor, and the processor executes the above-mentioned Figures 1 to 5Any of the embodiments shows steps related to the heliostat calibration method.

[0112] The embodiment of the present invention further provides a solar thermal power generation system, which may include the above-mentioned heliostat calibration device, and may also include a heliostat and a receiving tower; the number of the heliostat calibration device and the heliostat may be multiple, and the multiple heliostat calibration devices correspond to the multiple heliostats one by one, and the receiving tower includes Figures 1 to 5 The target point described in any embodiment may also include Figure 4 Sample targets as described in the examples shown.

[0113] In a specific implementation, a heliostat calibration device may be arranged to correspond to a heliostat one by one, so that each heliostat calibration device can calibrate a unique heliostat to prevent interference between sunlight reflected by the heliostats, thereby improving the parallelism of calibration.

[0114] For more details about the solar thermal power generation system, please refer to Figure 2 The related descriptions in the previous article will not be repeated here.

[0115] The embodiment of the present invention also provides a computer program product, including a computer program, wherein the computer program is executed when the processor is running. Figures 1 to 5 The steps of the heliostat calibration method described in any embodiment.

[0116] The "plurality" appearing in the embodiments of the present application refers to two or more.

[0117] The first, second, etc. descriptions appearing in the embodiments of the present application are only used for illustration and distinction of the description objects. There is no order, nor do they indicate any special limitation on the number of devices in the embodiments of the present application, and cannot constitute any limitation on the embodiments of the present application.

[0118] It should be pointed out that the serial numbers of the steps in this embodiment do not limit the execution order of the steps.

[0119] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A heliostat calibration method, characterized in that: include: Acquire a first image captured for a target point, and determine a first pixel position of the target point in the first image; Acquire a second image taken for a mirror image in a heliostat, and determine a second pixel position of a center point of a mirror image of the sun in the second image, wherein the mirror image in the heliostat includes at least a mirror image of the sun; Based on a target transformation parameter, transforming the first pixel position from an image coordinate system to which the first image belongs to an image coordinate system to which the second image belongs to obtain a corresponding mapped pixel position, wherein the target transformation parameter is used to indicate a coordinate space transformation relationship between an image coordinate system to which the first image belongs and an image coordinate system to which the second image belongs; Determine whether the distance between the second pixel position in the second image and the mapped pixel position is less than or equal to a preset first distance threshold; If the judgment result is no, the heliostat is calibrated based on the second pixel position and the mapped pixel position, and then a second image taken for the mirror image in the calibrated heliostat is obtained, and a second pixel position corresponding to the center point of the mirror image of the sun in the second image is re-determined until the distance between the mapped pixel position and the re-determined second pixel position is less than or equal to the first distance threshold.

2. The method according to claim 1, characterized in that The target transformation parameters are determined in the following manner: Performing a first operation, the first operation comprising: adjusting the heliostat until a sample target point on a receiving tower coincides with a position of a light spot formed on the receiving tower after sunlight is reflected by the heliostat; acquiring a first sample image shot for the sample target point on the receiving tower, and determining an actual pixel position of the sample target point in the first sample image, recorded as a first sample position; acquiring a second sample image shot for the mirror image in the adjusted heliostat, and determining an actual pixel position of a center point of the mirror image of the sun in the second sample image, recorded as a second sample position; Determining the target transformation parameters based on multiple groups of first sample positions and second sample positions determined after performing the first operation multiple times; The locations of the sample targets targeted by each execution of the first operation are different.

3. The method according to claim 2, characterized in that Adjusting the heliostat until the sample target point on the receiving tower coincides with the position of the light spot formed on the receiving tower after the sunlight is reflected by the heliostat, comprising: Acquire a target image captured for the sample target point and the light spot; Determine respectively the actual pixel positions of the sample target point and the light spot in the target image, and record them as the first target position and the second target position; Determining whether a first target position and a second target position in the target image overlap; If the judgment result is no, the heliostat is adjusted, and a target image is obtained for the sample target point and a light spot formed on the receiving tower after the sunlight is reflected by the adjusted heliostat, until the first target position and the second target position in the target image coincide with each other.

4. The method according to claim 1, characterized in that The heliostat calibration method is implemented by a heliostat calibration device; The step of acquiring a first image shot for a target point and determining a first pixel position of the target point in the first image includes: Acquire a first image captured for a target point, and determine an actual pixel position of the target point in the first image; Determine whether the distance between the actual pixel position of the target point and the center point of the first image is less than or equal to a preset second distance threshold; If the judgment result is no, adjusting the heliostat calibration device based on the actual pixel position of the target target and the center point of the first image, then acquiring a first image re-taken for the target target, and re-determining the actual pixel position of the target target in the first image until the distance between the actual pixel position and the center point of the first image is less than or equal to the second distance threshold, and using the actual pixel position of the target target determined last time as the first pixel position of the target target in the first image; After the heliostat calibration device is adjusted, the spatial position of the first image re-photographed for the target point is adjusted accordingly.

5. The method according to claim 1, characterized in that Calibration of the heliostat is achieved by controlling the movement of the heliostat; Calibrating the heliostat based on the second pixel position and the mapped pixel position includes: Determine a distance between the second pixel position and the mapped pixel position, recorded as a target distance; if the target distance is less than or equal to a preset third distance threshold, reduce a moving speed of the heliostat, and calibrate the heliostat using the reduced moving speed; The third distance threshold is greater than or equal to the first distance threshold.

6. The method according to claim 5, characterized in that The smaller the target distance is, the smaller the lowered moving speed of the heliostat is.

7. The method according to claim 1, characterized in that Determining a second pixel position of a center point of the sun's mirror image in the second image includes: Determine a maximum brightness value among the brightness values ​​of the pixels in the second image; Based on the maximum brightness value and a preset target brightness range, a second pixel position of a center point of the sun's mirror image in the second image is determined.

8. The method according to claim 7, characterized in that Determining a second pixel position of a center point of the sun's mirror image in the second image based on the maximum brightness value and a preset target brightness range includes: Determining whether the maximum brightness value is within the target brightness range; If the maximum brightness value exceeds the target brightness range, the exposure time of the shooting is adjusted, and a second image retaken based on the adjusted exposure time is obtained, until the maximum brightness value among the brightness values ​​of each pixel of the retaken second image is within the target brightness range, and the position of the pixel to which the maximum brightness value among the brightness values ​​of each pixel of the second image taken most recently belongs is used as the second pixel position of the center point of the sun's mirror image in the second image.

9. The method according to claim 8, characterized in that The two endpoint brightness values ​​of the target brightness interval are respectively recorded as a first brightness threshold and a second brightness threshold, and the first brightness threshold is smaller than the second brightness threshold; If the maximum brightness value exceeds the target brightness range, the exposure time of shooting is adjusted, including: If the maximum brightness value is greater than or equal to the second brightness threshold, reducing the exposure time of shooting; If the maximum brightness value is less than or equal to the first brightness threshold, the exposure time of shooting is increased.

10. A heliostat calibration device, characterized in that: include: A first pixel position determination module, used to obtain a first image shot for a target target point, and determine a first pixel position of the target target point in the first image; A second pixel position determination module is used to obtain a second image taken for a mirror image in a heliostat, and determine a second pixel position of a center point of the mirror image of the sun in the second image, wherein the mirror image in the heliostat includes at least the mirror image of the sun; a coordinate space transformation module, configured to transform the first pixel position from an image coordinate system to which the first image belongs to an image coordinate system to which the second image belongs based on a target transformation parameter, so as to obtain a corresponding mapped pixel position, wherein the target transformation parameter is used to indicate a coordinate space transformation relationship between the image coordinate system to which the first image belongs and the image coordinate system to which the second image belongs; a judging module, configured to judge whether the distance between the second pixel position in the second image and the mapped pixel position is less than or equal to a preset first distance threshold; a heliostat calibration module, configured to, if the judgment result is no, calibrate the heliostat based on the second pixel position and the mapped pixel position, then obtain a second image taken for the mirror image in the calibrated heliostat, and redetermine a second pixel position corresponding to the center point of the mirror image of the sun in the second image, until the distance between the mapped pixel position and the redetermined second pixel position is less than or equal to the first distance threshold.

11. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the heliostat calibration method according to any one of claims 1 to 9 are executed.

12. A heliostat calibration device, comprising a memory and a processor, wherein the memory stores a computer program that can be run on the processor, wherein: When the processor runs the computer program, the steps of the heliostat calibration method according to any one of claims 1 to 9 are performed.

13. A solar thermal power generation system, characterized in that: The heliostat calibration device comprises the heliostat according to claim 12, and further comprises: a heliostat and a receiving tower; the heliostat calibration device corresponds to the heliostat one-to-one, and the receiving tower comprises the target point according to any one of claims 1 to 9.

14. A computer program product comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the heliostat calibration method according to any one of claims 1 to 9 are executed.

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