CN106679695B - Focal plane thermal deformation testing method based on star sensor - Google Patents
Focal plane thermal deformation testing method based on star sensor Download PDFInfo
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Abstract
The invention discloses a focal plane thermal deformation testing method based on a star sensor, which comprises the following steps: s1, mounting the static light star simulator on the star sensor, and placing the static light star simulator and the star sensor together in a vacuum tank; and S2, applying temperature change excitation to the focal plane of the star sensor, and collecting the attitude measurement curve output by the star sensor to obtain the output error of focal plane thermal deformation to attitude.
Description
Technical Field
The invention particularly relates to a focal plane thermal deformation testing method based on a star sensor.
Background
With the rapid development of the aerospace industry in China, the development requirement of a high-resolution earth observation satellite is increasingly urgent, and a star sensor is adopted for accurately measuring the attitude of the earth observation satellite, so that the star sensor is an important part for measuring the attitude of the current spacecraft. To realize high-precision attitude measurement, each link of the attitude measurement needs to be controlled. The star sensor is generally composed of three parts, namely an optical and precise structure system, a photoelectric detector, a signal processing circuit and software. During the on-orbit operation, the space environment is severe, and various complex temperature working conditions can be met, so that the thermal stability of the photoelectric detection system is particularly considered. Based on the star sensor technology, a photoelectric detector shoots an image of which the visual axis points to the sky, the position and brightness information of star points of the image is extracted through a signal processing circuit, corresponding matching of observed stars is found in a navigation star library through a star map recognition algorithm, and the three-axis attitude information of the star sensor is calculated by utilizing the direction vector information of the matched star pairs, so that the space attitude of the spacecraft is determined.
The accurate three-axis attitude information obtained by the star sensor cannot be basically guaranteed by the photoelectric detector. The photoelectric detector is arranged at the focal plane position of the optical system and used for shooting a starry sky image pointed by the visual axis, so that the accurate position (including X-direction coordinates, Y-direction coordinates, starry point gray scale information and the like) of a starry point can be determined, and the photoelectric detector is mainly used for accurately positioning the position of the star. It can be seen from the on-orbit flight data and the ground thermal vacuum test that the change of the environmental temperature has a certain influence on the measurement precision of the attitude angle output by the star sensor, so that the photoelectric detector is deformed in the temperature change process, the two-dimensional plane coordinates of the star point change, errors are introduced in the star point centroid resolving process, and the solved attitude transfer matrix and the finally output attitude precision also bring deviations. Therefore, the influence of focal plane thermal deformation factors on the attitude calculation precision needs to be analyzed, and a basic basis is provided for obtaining high-precision attitude.
At present, the field of testing based on focal plane thermal deformation is blank, and the testing and research of the aspect are not mentioned yet. The invention provides a method for testing the focal plane thermal deformation of a star sensor, which is used for simply and effectively testing the influence of the focal plane thermal deformation on the attitude precision of the star sensor.
Disclosure of Invention
The invention aims to provide a focal plane thermal deformation testing method based on a star sensor, which is used for measuring the variation of an attitude measurement precision curve output by the star sensor under periodic temperature change excitation, and further providing theoretical basis and actual reference for correcting measurement errors caused by detector deformation.
In order to achieve the purpose, the invention is realized by the following technical scheme:
a focal plane thermal deformation testing method based on a star sensor is characterized by comprising the following steps:
s1, mounting the static light star simulator on the star sensor, and placing the static light star simulator and the star sensor together in a vacuum tank;
and S2, applying temperature change excitation to the focal plane of the star sensor, and collecting the attitude measurement curve output by the star sensor to obtain the output error of focal plane thermal deformation to attitude.
In the step S1, the star sensor fixes the static optical star simulator through the adapter ring, and when the temperature changes, the deformation of the focal plane of the star sensor is higher than the deformation of the adapter ring and the static optical star simulator.
The static light star simulator simulates and generates a static star map in the sky area, the star sensor aligns with the static star map for shooting, and the data processing system can solve the right ascension and the declination of the sky area where the static star map is located.
In the step S2, before obtaining the output error of the focal plane thermal deformation versus the attitude, the change trend term of the star sensor optical axis direction caused by the change of the environmental temperature needs to be deducted.
The method for obtaining the attitude output error caused by the focal plane thermal deformation specifically comprises the following steps:
taking temperature fluctuation, right ascension fluctuation and declination fluctuation data in a fluctuation period;
and calculating the maximum value of the declination angle fluctuation period and the maximum value of the declination angle fluctuation period, and obtaining the output error of focal plane thermal deformation to attitude.
Compared with the prior art, the invention has the following advantages:
according to the invention, by measuring the variable quantity of the attitude measurement precision curve output by the star sensor under the periodic temperature change excitation, theoretical basis and actual reference are provided for correcting the measurement error caused by the deformation of the detector.
Drawings
FIG. 1 is a structural diagram of a focal plane thermal deformation testing system based on a star sensor according to the present invention;
FIG. 2 is a flow chart of a focal plane thermal deformation testing method based on a star sensor according to the invention;
FIG. 3 is a graph showing the optical axis direction and the temperature change of the star sensor during the thermal vacuum test;
FIG. 4 is a plot of optical axis orientation versus temperature (minus the trend term) for a star sensor during a thermal vacuum test.
Detailed Description
The present invention will now be further described by way of the following detailed description of a preferred embodiment thereof, taken in conjunction with the accompanying drawings.
And applying temperature change excitation to the star sensor in the vacuum tank, so that the image surface of the detector is deformed, the position information of star points is changed, and the output attitude curve is changed. The specific calculation of the amount of change is as follows.
Position seat for setting actual measurement star point shot by detectorThe coordinate system of the image plane of the detector is converted into a space coordinate system, the origin of coordinates is at the optical center position of the star sensor, the z axis is coincident with the optical axis of the star sensor, x and y are parallel to the edge of the detector surface, and the position of the star point under the star sensor body coordinate system is [ x, y, z ] z]t. The star point is the vertical foot of the focal distance on the target surface of the detector, and the (x ', y') is the centroid of the star point after distortion correction, which can be known from the calibration result. Therefore, the coordinates of the star light direction vector under the star sensor body coordinate system are as formula (1):
wherein f is the focal length of the star sensor. Based on the coordinates of the J2000.0 coordinate system under the celestial coordinate system as formula (2), the coordinates of the starlight direction vector under the celestial coordinate system are:
w＝Tv (3)
t is a posture transfer matrix. And (4) solving the attitude calculation result of the star map shot by the star sensor through a Quest algorithm. At this time, if the position information of the star point is changed into (Δ x, Δ y) due to the deformation of the photoelectric detector, the actually observed star vector and the ideal star vector have deviation, and the output attitude calculation result is changed accordingly according to the formula, so that the thermal deformation of the focal plane introduces an error to the measurement attitude output by the star sensor.
Intercepting a-50 ℃ low-temperature maintaining data section for carrying out temperature change excitation of the detector. And controlling the refrigerator to a certain temperature in the low-temperature keeping process of-50 ℃, and observing the change of the output attitude curve of the star sensor. The data curve graph after the refrigerator is started is compared with the data curve stored before, namely the influence of the deformation of the focal plane caused by the periodic temperature change excitation on the change of the star point position is obtained. And taking the data in the fluctuation period for evaluation, thereby obtaining the measurement error caused by the thermal deformation of the focal plane assembly.
Therefore, as shown in fig. 1 and 2, the invention provides a focal plane thermal deformation testing method based on a star sensor, which comprises the following steps:
s1, mounting the static light star simulator 1 on the star sensor 2, and placing the static light star simulator 1 and the star sensor 2 in a vacuum tank 3 together; wherein the star sensor is connected to the data processing system 4. A light-weight adapter ring is sleeved on the star sensor light shield, and a well-matched static optical star model simulator is arranged on the light shield. In this embodiment, the star sensor and the static optical star model simulator both adopt a heatless design method to deal with the influence of temperature on the imaging quality of the product, that is, by a certain compensation technique, the optical system keeps the focal length unchanged or slightly changed in a larger temperature change environment. The great influence of temperature difference on the precision of the space optical system is avoided.
S2, starting to vacuumize in the vacuum tank to keep the vacuum degree at 1.3 x 103pa, starting to increase and decrease the temperature to +/-50 ℃ for circulation, applying temperature change excitation to a focal plane of the star sensor by the refrigerator, and acquiring an attitude measurement curve output by the star sensor to obtain an output error of thermal deformation of the focal plane to the attitude.
The static light star simulator simulates to generate a static star map in the sky area, and the red longitude and the red latitude of the sky area where the star map is located can be calculated by aligning the star sensor with the static star map shooting data processing system.
In the step S1, the star sensor fixes the static optical star simulator through the adapter ring, and when the temperature changes, the deformation of the focal plane of the star sensor is higher than the deformation of the adapter ring and the static optical star simulator.
In the above step S2, before obtaining the error of outputting the focal plane thermal deformation to the attitude, a trend term of the star sensor optical axis orientation change due to the environmental temperature change needs to be subtracted, and the trend term is obtained by 7 th order polynomial fitting, as shown in fig. 3. The fluctuation of the right ascension and the declination after deduction is only related to the temperature change excitation applied by the refrigerator, so that the measurement error introduced by the temperature deformation of the focal plane can be examined.
The obtaining of the output error of the focal plane thermal deformation to the attitude specifically includes:
obtaining a temperature fluctuation curve and an attitude (right ascension and declination) fluctuation curve through a data processing system, and taking temperature fluctuation, right ascension fluctuation and declination fluctuation data in a fluctuation period;
the attitude curve obtained by deducting trend term from the data processing system is shown in FIG. 4, the maximum value of the fluctuation period of the declination angle and the maximum value of the fluctuation period of the declination angle are taken to obtain the output error of the focal plane thermal deformation to the attitude, the maximum value of the fluctuation period of the declination angle is a, the maximum value of the fluctuation period of the declination angle is b, and the optical axis drift caused by the temperature change of the focal plane can be estimated as
The temperature variation is N deg.C, the measurement error due to the thermal deformation of the focal plane is about M/N (arcsec/deg.C).
In summary, the method for testing the focal plane thermal deformation based on the star sensor measures the variation of the attitude measurement precision curve output by the star sensor under the periodic temperature change excitation, and further provides theoretical basis and actual reference for correcting the measurement error caused by the deformation of the detector.
While the present invention has been described in detail with reference to the preferred embodiments, it should be understood that the above description should not be taken as limiting the invention. Various modifications and alterations to this invention will become apparent to those skilled in the art upon reading the foregoing description. Accordingly, the scope of the invention should be determined from the following claims.
Claims (1)
1. A focal plane thermal deformation testing method based on a star sensor is characterized by comprising the following steps:
s1, mounting the static light star simulator on the star sensor, and placing the static light star simulator and the star sensor together in a vacuum tank;
s2, applying temperature change excitation to the focal plane of the star sensor, and collecting the attitude measurement curve output by the star sensor to obtain the output error of focal plane thermal deformation to attitude;
in the step S1, the star sensor fixes the static optical star simulator through the adapter ring, and when the temperature changes, the deformation of the focal plane of the star sensor is higher than the deformation of the adapter ring and the static optical star simulator; the static light star simulator simulates and generates a static star map in the sky area, the star sensor aims at the static star map for shooting, and the data processing system can solve the right ascension and the declination of the sky area where the static star map is located; in the step S2, before obtaining the output error of the focal plane thermal deformation to the attitude, a change trend term of the star sensor optical axis direction caused by the change of the environmental temperature needs to be deducted;
the method for obtaining the attitude output error caused by the focal plane thermal deformation specifically comprises the following steps:
taking temperature fluctuation, right ascension fluctuation and declination fluctuation data in a fluctuation period;
calculating the maximum value of the declination angle fluctuation period and the maximum value of the declination angle fluctuation period, and obtaining the output error of focal plane thermal deformation to attitude;
after the trend term is deducted by the data processing system, the maximum value of the right ascension angle and the maximum value of the declination angle in the fluctuation period are taken, the maximum value of the right ascension angle in the fluctuation period is set as a, the maximum value of the declination angle in the fluctuation period is set as b, and the optical axis drift caused by the temperature change of the focal plane is estimated as
If the temperature variation is N, the measurement error caused by the thermal deformation of the focal plane is M/N.
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| CN108663137B (en) * | 2018-05-15 | 2019-12-20 | 北京控制工程研究所 | Star sensor temperature field measurement and pointing temperature drift compensation method |
| CN108759868A (en) * | 2018-06-20 | 2018-11-06 | 上海卫星工程研究所 | The antenna of the quick integral type mounting structure of satellite load star is directed toward thermal deformation measurement method |
| CN109141472B (en) * | 2018-08-13 | 2020-08-28 | 上海航天控制技术研究所 | Star observation testing device and method for evaluating thermal stability of star sensor |
| CN111323210B (en) * | 2020-03-17 | 2021-07-09 | 北京控制工程研究所 | Device and method for testing optical axis thermal stability of optical lens |
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| CN102564458B (en) * | 2011-12-29 | 2014-07-02 | 北京控制工程研究所 | Low-frequency error measuring method for star sensor |
| CN204514279U (en) * | 2015-03-24 | 2015-07-29 | 中国科学院上海技术物理研究所 | A kind of device measuring infrared focus plane module low temperature deformation |
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