CN103591966A - Star simulator test platform and test calibration method - Google Patents

Abstract

The invention discloses a star simulator test platform and a test calibration method. The test platform comprises a graphical display device, a smooth platform with the adjustable height, a sliding rail with a sliding block, and a three-axis precision displacement platform, wherein the graphical display device is positioned on the smooth platform with the adjustable height and is vertical to the sliding rail; the three-axis precision displacement platform is arranged on the sliding block and can slide relative to the sliding rail; a star sensor is arranged above the three-axis precision displacement platform. The test calibration method comprises the following steps: simulating a star map; erecting the star simulator test platform, and calibrating the levelness, the verticality and the center position of an imaging part of the graphical display device; imaging the simulated star map on the graphical display device; acquiring the simulated star map on the graphical display device, and verifying the star map through using a star identification algorithm. The test platform has the advantages of simplicity, convenience and effectiveness in equipment, small size, light weight, simple erection method and low cost and is a portable function detection type star simulator test platform.

Description

A kind of star simulator test platform and test calibration method

Technical field

The present invention relates to satellite attitude measurement field, relate to a kind of simple and effective star sensor Function detection type star simulator test platform and test calibration method.

Background technology

Attitude control system is one of subsystem that satellite complexity is the highest, and its main task is to realize sensing and the orientation of satellite in space preferred coordinate system to control, and generally sensor, appearance control computer and the execution unit of measuring orientation vector, consists of.The attitude measurement sensor of widespread use at present mainly contains: sun sensor, magnetometer, gyro, earth sensor, star sensor etc.

Star sensor is the current known minimum attitude measurement parts of the highest drift of measuring accuracy.Along with satellite, intercontinental missile, the fast development of the aerospace industries such as spaceship, has also proposed more and more higher requirement to precision, and star sensor has had irreplaceable effect.

The theory diagram of star sensor as shown in Figure 1, by optical system, complete the opto-electronic conversion to starry sky, fixed star is imaged onto on imageing sensor, processor and controller complete the collection to view data, by processor, star chart is carried out a series of algorithm process such as denoising, threshold decision, image binaryzation processing, stellar target identification, the extraction of asterism barycenter and star pattern matching, last basis is determined appearance principle and is calculated attitude angle again.

After Star-Sensor Design completes, need to survey magnitude, measuring accuracy, star Pattern Recognition Algorithm etc. to it and carry out ground demarcation or test, we are called star simulator by the equipment that completes this process on ground.According to the difference of working method, generally star simulator is divided into two classes, demarcation type star simulator and Function detection type star simulator.The effect of demarcation type star simulator be realize in the face of the demarcation of probe satellite etc. and measuring accuracy.Corresponding equipment requires very high to the simulation precision of single star subtended angle and magnitude, also high to experimental situation requirement, as needs dark room operation, cost is also higher.The major function of Function detection type star simulator is to carry out on the ground star image simulation, the star chart producing will match with the duty of star sensor to be measured, so that asterism extraction and star Pattern Recognition Algorithm to star sensor are carried out functional test, can realize with it research and the optimal design of ground star Pattern Recognition Algorithm, the not star image simulation in district and the checking of efficiency of algorithm etc. on the same day, so Function detection type star simulator is the position at actual starry sky to fixed star, the simulation that the sky of fixed star distributes is had relatively high expectations, the fixed star that it needs us to realize actual distribution in celestial sphere by corresponding coordinate conversion corresponds to display screen according to certain rule.

Because the research work that domestic star simulator test platform is carried out is less, and many complexity and the cost realized are high, abroad again China's export is limited, therefore, conduct a research portable, miniaturization, easy, star simulator that cost is low has higher using value and comparatively considerable realistic meaning.

Summary of the invention

The invention provides a kind of star simulator test platform and test calibration method of simple and effective Function detection type.

A test platform, comprises graphical visual display device, height-adjustable smooth platform, with slide rail and the three-axis accurate displacement platform of slide block;

Described graphical visual display device is positioned on described height-adjustable smooth platform and is mutually vertical with described slide rail;

Described three-axis accurate displacement platform is arranged on described slide block and can moves relative to slide rail, and the top of described three-axis accurate displacement platform is provided with star sensor.

Described graphical visual display device is notebook display screen.Notebook display screen is for display simulation star chart.

The camera lens of star sensor and the distance of described display screen are object distance L, and the value of object distance L can be selected according to actual calibrated and calculated.By the position of adjusting slider, can make to move forward and backward the position that slide block is positioned on slide rail and come instrumentality apart from L, thereby change the size of the display screen that can enter camera lens.

Graphical visual display device is L apart from the position of camera lens; The camera lens of described star sensor with shown in graphical visual display device keep vertical, to reduce test error.

Described slide rail is long is 100cm.Slide rail is set to 100cm, not only makes structure miniaturization more, and when needs are to simulation star chart while gathering, for simulating the imaging effect of actual fixed star, imaging asterism occupies 3 * 3 pixels, can be on the slide rail of 100cm moving slider with instrumentality apart from L.

The image sensor pixel array size of described star sensor is 1024 * 1280, and the focal length size of camera lens is 35mm.When object distance L is adjusted to 800mm, asterism size accounts for 3 * 3 pixels.

A method, comprising:

(1) star chart is simulated;

(2) build above-mentioned star simulator test platform, and carry out center the O ' (A that levelness, verticality and graphical visual display device can imaging moieties _c, B _c) demarcation;

(3) the simulation star chart in step (1) is imaged on graphical visual display device;

(4) utilize star sensor to gather the simulation star chart on graphical visual display device, and the star chart gathering is carried out to the checking of star Pattern Recognition Algorithm.

In step (1), the concrete grammar that star chart is simulated is: by matlab software and according to the optical axis sensing of star sensor and the visual field size of star sensor of input, determine simulation day district, read basic simulation star catalogue, find out all fixed stars within the scope of simulation day district, and the imageing sensor by star sensor corresponds to the relevant position on graphical visual display device by all fixed stars by coordinate conversion.

Described coordinate conversion comprises the coordinate conversion of star sensor coordinate system and celestial coordinate system.

In step (2), described scaling method comprises:

A) to the measurement that collimates of described test platform;

B) regulate smooth platform and three-axis accurate displacement platform to make center the O ' (A of graphical visual display device _c, B _c) and the center of the camera lens of star sensor keep highly slightly demarcating;

C) with O ' (A _c, B _c) for intersection point is at the simulation line of crossing on star chart, then this simulation star chart is carried out to imaging, according to levelness and the verticality of the imaging results judgement test platform of cross curve, if undesirable, need to regulate, and continue the cross curve after regulating to carry out imaging, repeat said process, until test platform is horizontal vertical;

D) to center O ' (A _c, B _c) carry out imaging, by imaging results, judge its whether center position in star sensor imageing sensor, if not, need, according to error size fine setting three-axis accurate displacement platform, after adjusting, to continue O ' (A _c, B _c) carry out imaging, until O ' (A _c, B _c) be imaged on the center position of imageing sensor.

In step (3), described simulation star chart imaging asterism occupies 3 * 3 pixels.To simulate the imaging effect of actual fixed star as far as possible.

In step (4), the checking of described star Pattern Recognition Algorithm is preferably in darkroom to be carried out, to avoid the catoptrical interference of sunshine and graphical visual display device.

Compare with the test platform technology of existing capability detection type star simulator, tool of the present invention has the following advantages:

1) the present invention only need to the slide rail of slide block, three-axis accurate displacement platform, can coarse height smooth platform and graphical visual display device can complete whole testing authentication process, there is simple equipments effective, volume is little, lightweight, building method is simple, expending low advantage, is a kind of test platform of portable Function detection type star simulator.

2) the present invention only needs test platform to carry out the demarcation that levelness, verticality and display screen can imaging center positions, can carry out relevant checking and the test of star sensor star Pattern Recognition Algorithm, has the simple advantage of mode of operation.

3) the invention provides the methods that realize packaged type star image simulation, only need the optical axis of inputting star sensor to point to, just can draw the institute's any stars in corresponding day district by matlab, there is good dirigibility, versatility.

Accompanying drawing explanation

Fig. 1 is the fundamental diagram of star sensor.

Fig. 2 is that test platform of the present invention is built schematic diagram.

Fig. 3 be in the present invention after 3 rotations the celestial coordinate system that obtains and star sensor coordinate system be related to schematic diagram.

Fig. 4 is the image-forming principle schematic diagram in the present invention.

Fig. 5 be can imaging moiety to test platform and display screen in the present invention the schematic diagram demarcated of center.

Wherein, 1, notebook display screen; 2, smooth platform; 3, three-axis accurate displacement platform; 4, star sensor; 5, slide block; 6, slide rail.

Embodiment

As described in Figure 2, a kind of star simulator test platform comprise notebook display screen 1, height-adjustable smooth platform 2, with slide rail 6 and the three-axis accurate displacement platform 3 of slide block 5;

Described notebook display screen 1 is positioned on height-adjustable smooth platform 2 and is mutually vertical with slide rail 6;

Three-axis accurate displacement platform 3 is arranged on slide block 5 and can moves relative to slide rail 6, the top of three-axis accurate displacement platform 3 is provided with star sensor 4, the distance of the camera lens of this star sensor 4 and notebook display screen 1 is L, and camera lens keeps vertical with described notebook display screen 1.

The effect of each several part is as follows: by moving slider 5, be positioned at the position on slide rail 6, comparatively easily instrumentality distance; Can be by the height of smooth platform 2 coarse adjustment notebook display screens 1, make center that the center of camera lens and display screen 1 can imaging moiety on same straight line as far as possible; Notebook display screen 1 is used for showing star chart; Three-axis accurate displacement platform 3 is used for the center that Accurate Calibration display screen 1 can imaging moiety.In addition, we need horizontal measuring instrument to demarcate the levelness of whole test platform and verticality.

The scaling method of above-mentioned test platform is:

The first step, simulates determining of star catalogue substantially.The star catalogue that the present invention uses is ACT star catalogue, from this star catalogue, the institute's any stars below certain magnitude (determining according to the detection limit magnitude of star sensor) is screened, and then rejects and becomes photostar and double star, has so just determined basic simulation star catalogue.Because be the checking to star Pattern Recognition Algorithm, as long as basic simulation star catalogue comprises the positional information of fixed star, right ascension and declination, store these information in excel form into, the right ascension information of one leu time storage fixed star, the declination information of a leu time corresponding stored fixed star.

Second step, points to according to the optical axis of star sensor, finds out the institute's any stars in corresponding day district from basic simulation star catalogue.Set the star sensor optical axis and point to (α ₀, δ ₀), according to the visual field size of star sensor, determining can imaging Tian district scope.With matlab, read the information of fixed star in basic simulation star catalogue, and find out the institute's any stars in day district.

The 3rd step, shows by matlab the fixed star finding according to coordinate conversion and image-forming principle.First the fixed star in celestial sphere is converted in star sensor coordinate system according to formula (1) (2) (3), according to similar triangle theory, by formula (4) (5), be converted to again in imageing sensor coordinate system, set and display screen can imaging moiety center, finally according to image-forming principle, by formula (6) (7), be converted to the corresponding position of display screen, and drawn by matlab software.

In coordinate conversion, need to use four coordinate systems, be respectively star sensor coordinate system, satellite body coordinate system, satellite orbit coordinate system and celestial coordinate system, because star sensor is fixedly mounted on satellite, we are when discussing, easy in order to calculate, these two coordinate systems are done to a coincidence, only consider the coordinate conversion between celestial coordinate system and star sensor coordinate system.Make O-UVW represent celestial coordinate system, O '-XYZ represents star sensor coordinate system.O is at the center of the earth, and O ' is at the center of optical system of star sensor.The initial point O ' that supposes star sensor coordinate system can move on to the earth's core O, and O ' and O overlap, and therefore, only need to consider the rotational transform of coordinate system.By three Eulerian angle independently

just can determine the relation between coordinate system.Initial time initial point O is in the earth's core, and OU axle points to the first point of Aries, OW axle directed north, and OU, OV, OW form right-handed coordinate system, can be converted to XYZ coordinate system by UVW coordinate system through 3 rotations, are now expressed as follows:

$\left[\begin{array}{c}X\\ Y\\ Z\end{array}\right]=M\left[\begin{array}{c}U\\ V\\ W\end{array}\right]---\left(1\right);$

Suppose to make UVW coordinate system first around W axle rotation φ angle, obtain U ₁v ₁w ₁coordinate system, matrix M 1 can be expressed as follows:

$M1=\left[\begin{array}{ccc}\cos \mathrm{\φ}& \sin \mathrm{\φ}& 0\\ -\sin & \cos \mathrm{\φ}& 0\\ 0& 0& 1\end{array}\right]---\left(1a\right);$

Again around U ₁axle rotation θ angle, makes W ₁axle overlaps with Z axis, obtains U ₂v ₂w ₂coordinate system, rotation matrix M2 is expressed as follows:

$M2=\left[\begin{array}{ccc}1& 0& 0\\ 0& \cos \mathrm{\θ}& \sin \mathrm{\θ}\\ 0& -\sin \mathrm{\θ}& \cos \mathrm{\θ}\end{array}\right]---\left(1b\right);$

Finally again around W ₂axle turns

angle, just obtains XYZ coordinate system, and rotation matrix M3 can be expressed as:

M can be expressed as follows with M1, M2, M3:

M=M3*M2*M1 (1d)；

For easy calculating, get

θ=90 °-δ ₀, φ=90 °+α ₀, matrix M can be simplified and is expressed as follows:

$M=\left[\begin{array}{ccc}-\sin {\mathrm{\δ}}_0\cos {\mathrm{\α}}_0& -\sin {\mathrm{\δ}}_0\sin {\mathrm{\α}}_0& \cos {\mathrm{\δ}}_0\\ \sin {\mathrm{\α}}_0& -\cos {\mathrm{\α}}_0& 0\\ \cos {\mathrm{\δ}}_0\cos {\mathrm{\α}}_0& \cos {\mathrm{\δ}}_0\sin {\mathrm{\α}}_0& \sin {\mathrm{\δ}}_0\end{array}\right]---\left(2\right);$

The unit vector of fixed star i under celestial coordinate system is:

$\left[\begin{array}{c}U\\ V\\ W\end{array}\right]=\left[\begin{array}{c}\cos {\mathrm{\α}}_i\cos {\mathrm{\δ}}_i\\ \sin {\mathrm{\α}}_i\cos {\mathrm{\δ}}_i\\ \sin {\mathrm{\δ}}_i\end{array}\right]---\left(3\right);$

According to formula (1), (2), (3), can obtain respectively X, Y, Z.Shown in Fig. 3 is that the XYZ coordinate obtaining afterwards through 3 rotations is and the relation of star sensor coordinate system, has similar triangles relation between the two, by the geometric relationship between them, can calculate the coordinate (x, y) of fixed star on imageing sensor.The focal length of supposing star sensor is f, and the pixel dimension size of imageing sensor used is P _sENSOR:

$x*\frac{P_{\mathrm{SENSOR}}}{f}=\frac{X}{Z}---\left(3a\right);$

$y*\frac{P_{\mathrm{SENSOR}}}{f}=\frac{Y}{Z}---\left(3b\right);$

Can be in the hope of:

$x=\frac{f*X}{P_{\mathrm{SENSOR}}*Z}---\left(4\right);$

$y=\frac{f*X}{P_{\mathrm{SENSOR}}*Z}---\left(5\right);$

Determine the coordinate position (x, y) of imageing sensor afterwards, suppose that object distance is L by the slide block place that to be adjusted to apart from display screen be L, the pixel dimension size of display screen is P _dISPLAY, center O ' (A that can imaging moiety to display screen _c, B _c), schematic diagram as shown in Figure 4, can be determined now asterism coordinate position (a, b) on display screen after a series of coordinate conversion of process according to image-forming principle, a, b can be expressed as:

$a=A_C+\frac{x*P_{\mathrm{SENSOR}}*L}{P_{\mathrm{DISPLAY}}*f}---\left(6\right);$

$b=B_C+\frac{y*P_{\mathrm{SENSOR}}*L}{P_{\mathrm{DISPLAY}}*f}---\left(7\right);$

Now, the present invention corresponds to by matrix conversion and image-forming principle the fixed star An Tian district that meets certain condition in celestial sphere on display screen, that is to say, now, we gather image and directly the fixed star in corresponding day district in celestial sphere are gathered to image the simulation star chart forming on display screen respectively, and the image space of asterism on imageing sensor is consistent in theory.

The 4th step, builds test platform.Smooth platform is placed on experiment table, notebook is placed on smooth platform, slide rail is placed with notebook display screen is vertical, displacement platform is placed on slide block, again star sensor is placed on above displacement platform, then, the position of adjusting slider, the position that makes distance of camera lens display screen is L, and camera lens will keep vertical placement with display screen.

The 5th step, the demarcation that test platform levelness, verticality and display screen can imaging moiety centers.As shown in Figure 5, simulation star chart with cross curve and central point is carried out to imaging, according to imaging results, left and right manual adjustments test platform and three-axis accurate displacement platform up and down,, until test platform levelness and verticality on the whole meet the demands, and center is imaged onto the center position of imageing sensor.It should be noted that, owing to will simulate the imaging effect of actual fixed star as far as possible, preferably imaging asterism occupies 3 * 3 pixels, need to repeatedly to object distance L, regulate (and after object distance change, the position that simulation star chart is positioned on display screen also can and then change).Star sensor image sensor pixel array size of the present invention is 1024 * 1280, and the focal length size of camera lens is 35mm, and when object distance is adjusted to 800mm, imaging asterism size accounts for 3 * 3 pixels, meets the requirements.

The 6th step, the checking of star sensor star Pattern Recognition Algorithm.Simulation star chart being carried out to imaging, the star chart collecting is carried out to threshold value extraction, according to threshold value, star chart is carried out to binary conversion treatment, is then stellar target identification, and asterism barycenter extracts and carries out triangle map algorithm etc. with navigational star table.Utilize test platform of the present invention to carry out the checking of algorithm function and efficiency.

Claims (7)

1. a star simulator test platform, is characterized in that, comprises graphical visual display device, height-adjustable smooth platform, with slide rail and the three-axis accurate displacement platform of slide block;

Described graphical visual display device is positioned on described height-adjustable smooth platform and is mutually vertical with described slide rail;

Described three-axis accurate displacement platform is arranged on described slide block and can moves relative to slide rail, and the top of described three-axis accurate displacement platform is provided with star sensor.

2. star simulator test platform according to claim 1, is characterized in that, the camera lens of described star sensor keeps vertical with described graphical visual display device.

3. star simulator test platform according to claim 1, is characterized in that, described slide rail is long is 100cm.

4. star simulator test platform according to claim 1, is characterized in that, described graphical visual display device is notebook display screen.

5. a test calibration method, is characterized in that, comprising:

(1) star chart is simulated;

(2) build as the star simulator test platform as described in arbitrary in claim 1-4, and carry out center the O ' (A that levelness, verticality and graphical visual display device can imaging moieties _c, B _c) demarcation;

(3) the simulation star chart in step (1) is imaged on graphical visual display device;

(4) utilize star sensor to gather the simulation star chart on graphical visual display device, and the star chart gathering is carried out to the checking of star Pattern Recognition Algorithm.

6. test calibration method according to claim 5, it is characterized in that, in step (1), the concrete grammar that star chart is simulated is: by matlab software and according to the optical axis sensing of star sensor and the visual field size of star sensor of input, determine simulation day district, read basic simulation star catalogue, find out all fixed stars within the scope of simulation day district, and the imageing sensor by star sensor corresponds to the relevant position on graphical visual display device by all fixed stars by coordinate conversion.

7. test calibration method according to claim 5, is characterized in that, in step (2), described scaling method comprises:

A) to the measurement that collimates of described test platform;

B) regulate smooth platform and three-axis accurate displacement platform to make center the O ' (A of graphical visual display device _c, B _c) and the center of the camera lens of star sensor keep highly slightly demarcating;

C) with O ' (A _c, B _c) for intersection point is at the simulation line of crossing on star chart, then this simulation star chart is carried out to imaging, according to levelness and the verticality of the imaging results judgement test platform of cross curve, if undesirable, need to regulate, and continue the cross curve after regulating to carry out imaging, repeat said process, until test platform is horizontal vertical;

D) to center O ' (A _c, B _c) carry out imaging, by imaging results, judge its whether center position in star sensor imageing sensor, if not, need, according to error size fine setting three-axis accurate displacement platform, after adjusting, to continue O ' (A _c, B _c) carry out imaging, until O ' (A _c, B _c) be imaged on the center position of imageing sensor.

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