CN101236086A - Evaluation and Judgment Method of Ultraviolet Lunar Sensor Output Data - Google Patents

Abstract

The evaluation and judgment method of the output data of the ultraviolet moon sensor is to judge the brightness and darkness of the moon image output by the ultraviolet moon sensor, and compare the proportion of dark gray pixels in the image with the preset proportion threshold. If the former is greater than the latter, then If the image is considered to be too dark, set the data quality level to the lowest level. Otherwise, judge whether there is strong stray light in the image. If so, set the data quality level to the lowest level. Otherwise, judge the effective edge length of the moon in the image. If the effective edge length is less than the preset value, If the arc is considered to be too short, the data quality level is set to the lowest level; otherwise, the data quality is graded and calculated according to the arc length of the lunar edge and the fitting error. The data judging method selects the valid data according to the threshold value of the data with the set level, and applies the weight coefficient to the valid data according to the quality level setting. The present invention performs quantitative evaluation and judgment on the current target situation and calculation, and effectively avoids the wrong data of the ultraviolet moon sensor. impact on the system.

Description

Evaluation and Judgment Method of Ultraviolet Lunar Sensor Output Data

technical field

The invention relates to an evaluation method for data output by an ultraviolet moon sensor, belonging to the field of optical imaging attitude sensors.

Background technique

With the rapid advancement of imaging detection devices and processor technology, spacecraft attitude sensors are gradually developing from unit scanning to imaging. The ultraviolet moon sensor is a large field of view imaging attitude sensor that is different from traditional horizons. . The output of the ultraviolet lunar sensor is restricted by the following factors: ① The quality of ultraviolet lunar imaging; ② Moon phases, including full moon, gibbous moon, crescent moon, and crescent moon; ③ Lunar surface terrain radiation differences and fluctuations; ④ Edge extraction and other information processing methods adaptability. The above factors make the data output of the ultraviolet lunar sensor have different data quality outputs in different arcs of the orbit, which is the technical background for the evaluation of the output data quality of the ultraviolet lunar sensor.

The evaluation of the data quality level realizes the mathematical description of the correctness, accuracy and reliability of the attitude information and the orbital height information. For the spacecraft navigation guidance control system (GNC), different data are used according to the quality level, for example Eliminate low-quality data and weight high-quality data, so the design of data quality level has important engineering value for satellite sensors and GNC systems.

The ultraviolet moon sensor is my country's first sensor for large-field-of-view extended target imaging.

Jiang Yu, Wang Weitao, Zhang Jiangao, He Guanghui, Data Quality Problems in Data Mining and Its Mining, Computer Science [J], No. 12, 2002. The literature mentions the concept of data quality in database establishment, but the main deficiency is that there is no discussion on the field of optical attitude sensors and quality quantification and establishment methods.

U.S. Patent US5319969, titled "Method for determining 3-axis spacecraftattitude", introduces a three-axis attitude determination method using an ultraviolet spectrum attitude sensor, which does not involve quality evaluation and judgment of output data.

Contents of the invention

The technical solution of the present invention is to provide a method for evaluating and judging the output data of the ultraviolet moon sensor. The data evaluation method quantifies the reliability of the data output by the ultraviolet moon sensor, and the judgment method further determines the application of the quantified data. The weight coefficient can effectively avoid the influence of the wrong output data of the ultraviolet moon sensor on the satellite system.

The technical solution of the present invention is: the ultraviolet moon sensor output data evaluation method, comprises the following steps:

(1) Carry out brightness analysis to the moon image data output by the ultraviolet moon sensor, judge the stray light interference of the moon image and the brightness and darkness of the image, compare the proportion of dark gray pixels in the image with the size of the preset ratio threshold, If the dark gray pixel ratio of the image is greater than the preset ratio threshold, the image is considered too dark, and the step (5) is turned, otherwise, the step (2) is turned;

(2) Determine whether there is strong stray light in the image, if so, go to step (5), otherwise go to step (3);

(3) Interpret the effective edge length of the moon in the image, if the effective edge length is less than the preset value, then consider the arc segment is too short, turn to step (5), otherwise turn to step (4);

(4) According to the arc length of the lunar edge and the fitting error, the data quality is graded and calculated;

(5) Set the output data quality level to the lowest level.

The calculation formula of the image dark pixel ratio value rate in the step (1) is:

$\mathrm{<span\; class="notranslate">\; Rate</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; Num</span>}}_{\mathrm{<span\; class="notranslate">\; PT</span>}}}{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; N</span>}}$

Wherein, Num _PT is the total amount of pixels whose grayscale is less than the dark grayscale threshold _PT in the image;

P _T is equal to the maximum background gray value in the ground experiment;

M and N are the length and width of the image.

A method for judging the output data of the ultraviolet moon sensor: first, an evaluation threshold is determined according to the simulation and test conditions, and the result of claim 1 is compared with the evaluation threshold, and the data greater than the threshold is regarded as valid data, otherwise discarded; then, Design the application weight coefficient for the effective data according to its quality level. The higher the quality level, the greater the application weight coefficient. The calculation formula of the application weight coefficient is as follows:

Coef＝Q0*W

W=QD/max(QD)

Among them, Coef is the system application coefficient;

Q0 is the preset maximum coefficient value;

W is the weight value;

max(QD) represents the maximum quality level.

Compared with the prior art, the present invention has beneficial effects as follows:

(1) The present invention realizes quantization of quality grades by analyzing image light and shade, stray light conditions, lunar arc length and calculation errors that affect the attitude measurement of ultraviolet lunar sensors, compared with existing sensors that mainly rely on front and rear data comparison methods , Realize on-orbit real-time evaluation of output data, strong independence and real-time performance; and because the present invention comprehensively considers image brightness, stray light and other factors, the accuracy is high.

(2) The quality calculation formula of the present invention is novel and comprehensive, which not only considers the length of the lunar arc segment but also includes the error of the fitting calculation, and completely reflects the degree of attitude accuracy.

(3) The image quality is comprehensively considered, including both bright and dark judgments and stray light interference judgments.

(4) The present invention judges the data quantified by the quality level by first setting the threshold, which can effectively prevent the output of data with poor image quality or the short arc length of the lunar edge, and also prevent the output of data with large calculation errors. The present invention sets the weight coefficient The sensor output data can be used more effectively, and different weights can be applied to high and low quality data greater than the threshold.

Description of drawings

Fig. 1 is the flow chart of evaluation calculation of output data of ultraviolet moon sensor of the present invention;

Fig. 2 is a flow chart of judging strong stray light in the present invention;

Fig. 3 is a judgment flow chart of the present invention;

Fig. 4 is the lunar image that the present invention imports;

Fig. 5 is an effective edge image of the present invention.

Detailed ways

The ultraviolet moon sensor involved in the present invention can be a three-axis attitude sensor utilizing the ultraviolet spectrum segment disclosed in the patent No. US5837894 titled "Wide Field of View Sensor with diffractive Optical Corrector" applied by Honeywell Company. It is also possible to use a three-axis attitude sensor using the ultraviolet spectrum disclosed in the name "Method for determining 3-axis spacecraft attitude" of US Patent No. 5,319,969.

As shown in Figure 1, it is a flow chart of the method of the present invention, and the specific implementation process is as follows:

(1) Carry out brightness analysis to the moon image data output by the ultraviolet moon sensor, judge described moon image stray light interference and image light and dark degree, compare the dark pixel ratio rate in the image with the preset ratio threshold value, if the ratio value is greater than Described ratio threshold value, then think that image is too dark, turn to step (5), otherwise turn to step (2);

The formula for calculating the rate value of the dark pixel ratio in the image is:

$\mathrm{<span\; class="notranslate">\; Rate</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; Num</span>}}_{\mathrm{<span\; class="notranslate">\; PT</span>}}}{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; N</span>}}$

Among them, Num _PT is the total number of pixels whose grayscale is less than the grayscale threshold _PT in the image, and _PT is equal to the maximum background grayscale value in the ground experiment. For 0-255 images, _PT can be selected from [1-10]; M , N is the length and width of the image.

The preset ratio threshold is determined according to the ratio of the target's nominal size to the entire image, and the range is [0.9-0.99].

(2) Determine whether there is strong stray light in the image, if there is, go to step (5), otherwise go to step (3); wherein, the process of judging strong light interference is shown in Figure 2, and the specific method is as follows:

The first step is to determine the target surface analysis area for judging the strong stray light of the image taken by the ultraviolet moon sensor, and the analysis area is a certain row in the lower image part outside the effective field of view of the ultraviolet moon sensor.

The second step is to perform a horizontal search on the pixels in the analysis area. If two consecutive pixels are greater than the bright pixel threshold, stop the search and go to the third step, otherwise continue to search; the bright pixel threshold is slightly smaller than the threshold determined in the ground experiment. The brightest gray value is generally not less than 95% of the brightest gray value.

The third step is to start a vertical search for any one of the two pixels whose pixels are greater than the strong light threshold in the second step and count the number of consecutive pixels in the search greater than the bright pixel threshold. When the number of statistics is greater than the number When the threshold is set, it means that there is strong stray light in the image, and the search is stopped; otherwise, another pixel is searched vertically and the number of consecutive pixels in the search is larger than the bright pixel threshold is counted. When the number of statistics is greater than the number threshold (number When the threshold is generally greater than 10), it means that there is strong stray light in the image, and the search is stopped; otherwise, the search is continued from the second step until all the analysis areas are searched.

(3) Interpret the length of the edge of the moon image, if the edge length is less than the preset value, then the arc is considered too short, and go to step (5), otherwise go to step (4); the value range of the preset value is [1/4～ 1/8]*360.

(4) Carry out quality classification calculation for lunar images, the calculation formula is as follows:

$\mathrm{<span\; class="notranslate">\; QD</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; [</span>\frac{\mathrm{<span\; class="notranslate">\; Vnum</span>}}{\mathrm{<span\; class="notranslate">\; dPixel</span>}}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; ]</span>$

Among them, Vnum is the effective edge length;

dPixel is the calculation error;

K is a constant;

[] is the rounding operation;

QD is the quantified quality level.

(5) Set the lunar image quality level to 0.

After evaluating the lunar image through the above method, output the current sensor data and the corresponding quality level to the spacecraft GNC system. The GNC discards the low-quality level data. If the quality level is higher than the threshold, it will be used and it will be different with the high-quality data. Weight, where the threshold can be set to 6.

As shown in Figure 3, it is a flow chart of the application method of the present invention. At first, an evaluation threshold is determined according to the simulation and test conditions, and the result of claim 1 is compared with the evaluation threshold. Data greater than the threshold are considered valid data, otherwise discarded; Then, design the application weight coefficient according to the quality level of the effective data. The higher the quality level, the greater the application weight coefficient. The calculation formula of the application weight coefficient is as follows:

Coef＝Q0*W

W=QD/max(QD)

Among them, Coef is the system application coefficient;

Q0 is the preset maximum coefficient value;

W is the weight value;

max(QD) represents the maximum quality level.

The value range of the evaluation threshold mentioned above is [3-7].

Example:

Input the image shown in Figure 4 into the memory of the ultraviolet moon sensor, the equivalent focal length of the sensor is 1.8758mm (137.2 pixels), the target surface pixels are 1024*1024 and the length is 14mm, the dark pixel gray threshold is selected as 15, and the dark pixel ratio threshold is 90 %, calculate the total number of dark pixels:

Num=931907

Dark pixel ratio:

Rate=Num/(1024*1024)=88.87%

Judging that the ratio of dark pixels Rate<90%, transfer to strong stray light judgment.

Set the strong stray light threshold to 250. In the selected area, the grayscale of the last few rows of G(x, y) pixels is less than the strong light threshold, so calculate the edge length of the image, and select the edge arc length threshold as 1/6 arc equivalent 60°, after edge fitting processing, the length of the edge arc segment is 172° (see Figure 5), then the edge length: Vnum=172>preset value 45, so the quality level calculation is performed, and the total quality level is set [0～15] , the proportional coefficient K is 20, and the circle fitting error substituted into the calculation is 0.95, then the quality level:

Qd=[(172/0.95/20)]=9

Set the sensor quality threshold as Qt to 4, then: Qd>Qt, this time the output data of the sensor calculation result is valid; the system presets the maximum coefficient value Q0 for the sensor data to be 0.2, then apply the weight W: W=Qd/ max(QD)=9/15

Weighted application coefficient: Coef=W*Q0=0.12.

The idea and method of the present invention can be extended and applied to the data evaluation and judgment of other space sensors, as long as the method implemented by the idea of the present invention falls within the protection scope of the present invention, the unspecified parts of the present invention belong to those skilled in the art. common sense.

Claims (10)

1, ultraviolet moon sensor output data evaluation method is characterized in that comprising the following steps:

(1) moon view data of ultraviolet moon sensor output is carried out brightness analysis, judge that described lunar map is as bright dark degree, the size of dark gray pixel proportion and preset ratio threshold value in the movement images, if the dark gray pixel ratio of image thinks then that greater than the preset ratio threshold value image is dark excessively, change step (4), otherwise change step (2);

(2) judge whether image strong veiling glare occurs,, otherwise change step (3) if step (4) occurs changeing;

(3) the efficient frontier length of the moon in the interpretation image if efficient frontier length less than preset value, thinks that then segmental arc is too short, is changeed step (4), otherwise changes step (5);

(4) the output data quality grade is set to lowermost level;

(5) according to moon edge arc length with fit error and carry out the data quality classification and calculate.

2, ultraviolet moon sensor output data evaluation method according to claim 1 is characterized in that: the image dark pixel ratio value rate computing formula in the described step (1) is:

$\mathrm{Rate}=\frac{{\mathrm{Num}}_{\mathrm{PT}}}{M\&times;N}$

Wherein, Num _PTFor gray scale in the image less than dark gray threshold value P _TAmount of pixels sum total;

P _TEqual the maximum background gray levels in the ground experiment;

M, N are the length of image and wide.

3, ultraviolet moon sensor output data evaluation method according to claim 1 is characterized in that: preset ratio threshold value range of choice is [0.9～0.99] in the described step (1).

4, ultraviolet moon sensor output data evaluation method according to claim 1 is characterized in that: judge whether image strong veiling glare occurs, and method is as follows in the described step (2):

The first step is determined the target surface analyzed area that the strong veiling glare of image that ultraviolet moon sensor is taken the photograph is judged;

Second step, the pixel in the described analyzed area is carried out Horizon Search, if continuous two pixels of appearance greater than the bright pixel threshold value, then stop search and changeed for the 3rd step, otherwise continue search;

The 3rd step, pixel in second step is begun in vertically search and the statistics search contiguous pixels greater than the number of described bright pixel threshold value greater than any one pixel in two pixels of high light threshold value, when the number of statistics during greater than the number threshold value, there is strong veiling glare in the representative image, stop search; Otherwise, the one other pixel point is vertically searched for and adds up in the search contiguous pixels greater than the number of described bright pixel threshold value, when the number of statistics during, there is strong veiling glare in the representative image greater than the number threshold value, stop search; Otherwise, finish until the whole search of analyzed area from the continuation search of second step.

5, ultraviolet moon sensor output data evaluation method according to claim 4 is characterized in that: the analyzed area in the described first step is certain delegation in the lower images part outside the ultraviolet moon sensor apparent field.

6, ultraviolet moon sensor output data evaluation method according to claim 4 is characterized in that: described bright pixel threshold value is slightly less than in the ground experiment the brightest gray-scale value of determining, generally is not less than 95% of the brightest gray-scale value.

7, ultraviolet moon sensor output data evaluation method according to claim 1 is characterized in that: span [1/4～1/8] * 360 of preset value in the described step (3).

8, ultraviolet moon sensor output data evaluation method according to claim 1 is characterized in that: the data quality classification computing formula in the described step (4) is:

$\mathrm{QD}=[\frac{\mathrm{Vnum}}{\mathrm{dPixel}}/K]$

Wherein, Vnum is an efficient frontier length;

DPixe/ is for fitting error;

K is a proportionality constant, determines general span [20～80] according to emulation and test findings;

[] is rounding operation;

The quality grade of QD for quantizing.

9, a kind of method of judging claim 1 evaluating data result is characterized in that:

At first,, the result and the Evaluation threshold of claim 1 compared, think valid data greater than the data of threshold value, otherwise cast out according to the fixed Evaluation threshold of emulation and test situation;

Then, described valid data are used weight coefficient according to its quality grade size design, the high more application weight coefficient of quality grade is big more, and it is as follows to use the weight coefficient computing formula:

Coef＝Q0*W

W＝QD/max(QD)

Wherein, Coef is the system applies coefficient;

Q0 is default maximum coefficient value;

W is a weighted value;

Max (QD) represents maximum quality grade.

10, data determination methods according to claim 9 is characterized in that: described Evaluation threshold span [3～7].

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