SUN POSITION TRACKING METHOD BASED ON BLACK SUN EFFECT OF IMAGE SENSOR, COMPUTER PROGRAM STORED IN MEDIUM, AND SOLAR SENSOR USING THE SAME

• US 20170323453A1
• Filed: 05/01/2017
• Published: 11/09/2017
• Est. Priority Date: 05/03/2016
• Status: Active Grant

• Current Assignee: SungKyunKwan University's Research & Business Foundation (SungKyunKwan University (SKKU))
• Original Assignee: SungKyunKwan University's Research & Business Foundation (SungKyunKwan University (SKKU))
• Inventors: LEE, Sukhan, SALEEM, Rashid, KIM, Jaewoong
• Granted Patent: US 10,373,321 B2
• Time in Patent Office: Days
• CPC Class Codes: G06T 2207/20221 Image fusion; Image merging
• CPC Class Codes: G06T 2207/30181 Earth observation
• CPC Class Codes: G06T 5/20 using local operators
• CPC Class Codes: G06T 5/50 using two or more images, e.g. averaging or subtraction
• CPC Class Codes: G06T 5/70 Denoising; Smoothing
• CPC Class Codes: G06T 7/136 involving thresholding
• CPC Class Codes: G06T 7/246 using feature-based methods, e.g. the tracking of corners or segments
• CPC Class Codes: G06T 7/248 involving reference images or patches
• CPC Class Codes: G06T 7/277 involving stochastic approaches, e.g. using Kalman filters
• CPC Class Codes: G06T 7/292 Multi-camera tracking
• CPC Class Codes: H02S 20/32 specially adapted for solar tracking
• CPC Class Codes: Y02E 10/50 Photovoltaic [PV] energy

Abstract

The present invention provides a sun position tracking method based on a black sun effect of an image sensor, a computer program including commands for causing a computer system to perform the method, and a solar sensor using the method. The sun position tracking method includes processing a plurality of images captured using a plurality of image sensors installed to capture a plurality of images of the sun irrespective of the position of the sun to estimate the center point of the black sun and track the position of the sun.

Claims

1. A sun position tracking method based on a black sun effect of an image sensor, comprising:

capturing one or more images using one or more image sensors; and

processing the one or more captured images using the black sun effect.

2. The sun position tracking method according to claim 1, wherein the one or more image sensors capture a plurality of images using a plurality of image sensors for enabling position tracking irrespective of a position of the sun.

3. The sun position tracking method according to claim 1, wherein the one or more image sensors capture a plurality of images using a plurality of image sensors in order to fuse a plurality of sun position estimation results on the basis of the captured images to track the position of the sun with higher accuracy and reliability.

4. The sun position tracking method according to claim 1, wherein the processing of the one or more captured image using the black sun effect comprises:

estimating a center point of each black sun in the one or more captured images;

extracting one or more solar vectors with respect to the center point of each black sun;

transforming the one or more extracted solar vectors into reference coordinates; and

fusing the transformed solar vectors.

5. The sun position tracking method according to claim 4, wherein the estimating of the center point of the black sun comprises:

acquiring an image of the sun from a plurality of images captured using a plurality of image sensors;

repeatedly segmenting the image of the sun by at least one times while varying an intensity threshold value;

detecting corner points whenever the image of the sun is segmented; and

obtaining the center point of black sun from the detected corner points at the final segmenting of sun image.

6. The sun position tracking method according to claim 5, wherein the obtaining the center point of black sun from the detected corner points at the final segmenting of sun image includes obtaining a centroid of strong corner points corresponding to corner points detected from a final segmented image, and

wherein the estimating of the center point of the black sun further comprises estimating a strong corner point having a minimum distance from the centroid as the center point of the black sun for each of the strong corner points.

7. The sun position tracking method according to claim 4, wherein the extracting of the solar vectors comprises obtaining azimuths and altitudes of the solar vectors using the following mathematical formula for representing a 2-dimensional image of the sun as a 3-dimensional vector,

8. The sun position tracking method according to claim 4, wherein the transforming of the extracted solar vectors into the reference coordinates comprises obtaining an initial rotation using two solar vectors represented in sensor coordinates and two solar vectors represented in the reference coordinates at two different time points and determining the average of a plurality of initial rotations calculated by changing the two different time points by a predetermined number of times as a final rotation, to transform the extracted solar vectors into the reference coordinates.

9. The sun position tracking method according to claim 4, wherein the fusing of the one or more solar vectors comprises removing noise of azimuths and altitudes of the one or more solar vectors and fusing the solar vectors to calculate a final solar vector.

10. The sun position tracking method according to claim 9, wherein an extended Kalman filter is used to remove the noise.

11. A computer program stored in a computer readable medium to track a position of the sun on the basis of a black sun effect of an image sensor, and including commands for instructing a computing system to capture one or more images using one or more image sensors and to process the captured images using the black sun effect.

12. A solar sensor using a sun position tracking method based on a black sun effect of an image sensor, comprising:

a sensor unit for acquiring one or more images captured using one or more image sensors installed to acquire images of the sun; and

a processor for processing the one or more images using the black sun effect to track a position of the sun.

13. The solar sensor according to claim 12, wherein the sensor unit acquires a plurality of images captured using a plurality of image sensors for enabling position tracking irrespective of a position of the sun, and the processor fuses a plurality of sun position estimation results on the basis of the captured images to track the position of the sun.

14. The solar sensor according to claim 12, wherein the processor comprises:

a center point estimation module for estimating a center point of each black sun in the one or more captured images;

a solar vector extraction module for extracting one or more solar vectors with respect to the center point of each black sun;

a coordinate transformation module for transforming the one or more extracted solar vectors into reference coordinates; and

a fusion module for fusing the transformed solar vectors.

15. The solar sensor according to claim 14, wherein the center point estimation module configured to:

acquire an image of the sun from a plurality of images captured using a plurality of image sensors;

repeatedly segment the image of the sun by a predefined number of times while varying an intensity threshold value;

detect corner points whenever the image of the sun is segmented;

obtain a centroid of strong corner points corresponding to corner points detected from a final segmented image; and

estimate a strong corner point having a minimum distance from the centroid as the center point of the black sun for each of the strong corner points.

16. The solar sensor according to claim 14, wherein the solar vector extraction module obtains azimuths and altitudes of the solar vectors using the following mathematical formula for representing a 2-dimensional image of the sun as a 3-dimensional vector,

17. The solar sensor according to claim 14, wherein the coordinate transformation module is configured to:

obtain an initial rotation using two solar vectors represented in sensor coordinates and two solar vectors represented in the reference coordinates at two different time points; and

determine the average of a plurality of initial rotations calculated by changing the two different time points by a predetermined number of times as a final rotation, to transform the extracted solar vectors into the reference coordinates.

18. The solar sensor according to claim 14, wherein the fusion module removes noise of azimuths and altitudes of the one or more solar vectors and fusing the solar vectors to calculate a final solar vector.

19. The solar sensor according to claim 18, wherein an extended Kalman filter is used to remove the noise.

20. A solar sensor comprising 6 image sensor cameras installed at positions of 6 vertexes of a virtual icosahedron such that 3 cameras capture a black sun with hemispherical coverage irrespective of a position of the sun using a minimum number of image sensor cameras, the 6 vertexes including one reference vertex and 5 vertexes neighboring the reference vertex.