RU2641619C1 - Method of astrocorrection - Google Patents

Abstract

FIELD: tool engineering.

SUBSTANCE: according to the current coordinates and time from the directory of stars recorded in the onboard digital computer, a star pair is selected that is available for sighting at a given object location and at a given point in time, their coordinates are determined in the local coordinate system at the current moment of time, target indications are formed in the form of angles of teleblock targeting, the first one of the selected stars is subjected to sighting by pointing the axis of sight of teleblock to the calculated point determined by coordinates of the first one of the stars selected from the catalogue with determination of its measured coordinates, angular corrections representing differences between measured and calculated values of its sight angles are determined, the second one of the stars selected from the catalog is subjected to sighting by pointing the axis of sight of the teleblock to the calculated point determined by coordinates of the second one of the stars selected from the catalogue with determination of its measured coordinates, angular corrections representing the differences between the measured and calculated values of its sight angles are determined, then absolute value of difference between the calculated and measured angles of selected pair of stars detected during their sequential sighting is calculated, which is compared with given threshold value and, if this value is not exceeded, an indication of correction resolution is generated, and correction of these angular corrections is carried out in the estimation of errors of the corrected inertial system.

EFFECT: improved accuracy and interference resistance.

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Description

The invention relates to the field of instrumentation, and in particular to methods for determining errors of inertial navigation systems, in which the main navigation information (calculated coordinates and course) is corrected by signals from an astroizing device (teleblock) and used as part of on-board equipment of aerospace objects.

There is a method of astro correction (implemented by the astroinertial navigation system of serial astroinertial systems L14MA and L41, which are part of the navigation aerospace systems VP-021 and N-202), which consists in the fact that according to the current coordinates and time from the star catalog recorded in the onboard digital computer, a pair of stars is selected that is available for sighting at a given point of the object’s location and at a given time, their coordinates are determined in the local coordinate system at the current time, target designations are formed in the form of angles in targeting the teleblock, the first of the selected stars is sighted by pointing the target axis of the teleblock to the calculated point determined by the coordinates of the first of the stars selected from the catalog with the determination of its measured (actual) coordinates, angular corrections representing the differences between the measured and calculated values of its viewing angles are determined , the second of the stars selected from the catalog is sighted by pointing the target axis of the teleblock to the calculated point determined by the coordinates of the second of the selected from the catalog of stars with the determination of its measured coordinates, angular corrections are determined that represent the differences between the measured and calculated values of the angles of its sight, and then the angular corrections obtained during the sighting of the first and second stars are recalculated into errors of the corrected system.

The relationship between the angular corrections and the kinematic errors of the inertial navigation system is determined by the linear relation

or in scalar form

where z is the vector of angular corrections;

- вектор кинематических ошибок системы;

- vector of kinematic errors of the system;

H - communication matrix, the structure of which is determined by the teleblock suspension scheme and the kinematics of working out its pointing angles;

h ₁ , h ₂ , h ₃ - elements of the matrix N.

To obtain an unambiguous definition of the three components of the vector β, at least three non-degenerate equations (2) are required. Since when viewing one star we get two measurements (two angular corrections), to solve equation (2), measurements of at least two stars are required.

The main disadvantage of this method is the relatively low accuracy of determining errors inertial navigation system.

The problem to which the invention is directed, is to create a method of astro correction with increased accuracy and noise immunity.

The technical result achieved by the implementation of the invention is the provision of selection from a false signal created by any external interference (for example, a bubble of an astrolight or the edge of a cloud illuminated by the sun).

The indicated technical result is achieved by the fact that the astro correction method consists in the fact that according to the current coordinates and time, from the catalog of stars recorded in the on-board computer, a pair of stars is selected that is available for sighting at a given location of the object and at a given time, their coordinates are determined in the local coordinate system at the current moment of time, target designations are formed in the form of targeting angles of the teleblock, the first of the selected stars is sighted by pointing the target axis of the teleblock to the calculated point determined by the coordinates of the first of the stars selected from the catalog with the determination of its measured coordinates, angular corrections are determined that represent the differences between the measured and calculated values of its viewing angles, the second of the stars selected from the catalog is sighted by pointing the teleblock sighting axis at the calculated point determined by the coordinates of the second From the stars selected from the catalog with the determination of its measured coordinates, angular corrections are determined that represent the differences between the measured and calculated values by the angles of her sight. In order to increase noise immunity and accuracy, the absolute value of the difference between the calculated and measured angles of the selected pair of stars detected during their sequential sighting is then calculated, which is compared with a given threshold value and, if this value is not exceeded, a sign of correction correction is generated and these angular corrections are recalculated in evaluating the errors of the corrected inertial system.

Suppose that during the sighting of the first of the stars selected from the catalog, the star was endorsed and its angular corrections determined, and during the sighting of the second of the stars selected from the catalog, the second star was endorsed and its angular corrections determined. As a criterion for choosing the stars of the working pair (i.e., exactly the pair of stars selected from the catalog), we take the angular distance between the stars endorsed during the sighting sessions, or the cosine of this angular distance, which is defined as the scalar product of their Cartesian coordinates

where D is the angular distance between the stars;

i, j = 1, 2 - numbers of the observed stars;

x ₁ , x ₂ , x ₃ are the Cartesian coordinates of the stars being sighted.

The choice of the Cos (D) function as a criterion is explained by the fact that this function is invariant with respect to any orthogonal transformation. Indeed, for two vectors x ₁ and x ₂ Cos (D) represents the scalar product

Let be

y ₁ = Ax ₁ ,

y ₂ = Ax ₂ ,

where A is the orthogonal matrix.

Then

because A ^T A = E (due to the orthogonality of A), and the vector β of kinematic errors of the corrected inertial system is three small angles of rotation of the Euler-Krylov initial trihedron around its three axes, which can be described by an orthogonal rotation matrix.

In particular, if the azimuth-altitude suspension of the teleblock is considered, in which its pointing angles are defined as the azimuthal angle A, measured in the plane of the local horizon from the north direction of the local meridian against the clock, and angle B (height) is measured from the plane of the local horizon to the zenith, Cartesian coordinates of the star will be determined as

The cosine of the angle between the ith and jth stars is defined as

With a different teleblock suspension scheme, determining the angular distance between the stars through the corners of the teleblock exhibition is not difficult. Therefore, for definiteness, we will further consider this suspension scheme.

Varying Cos (D _ij ) at the angles A _i , A _j , B _i , B _j , we obtain

Since (8) is a variation of Cos (D _ij ), in the absence of system errors, which are three small rotation angles of the original coordinate system β ₁ , β ₂ , β ₃ around its three axes, i.e. are described by the orthogonal rotation matrix of the original coordinate system, ΔCos (D _ij ) should ideally be zero. Actually, in the presence of instrumental errors in determining the coordinates of the sighted stars, the working pair is selected by ΔCos (D _ij ), not exceeding some given threshold D ₀ . The way to verify that a pair of stars selected from the catalog is endorsed is as follows:

1. All measured angular corrections, ΔA _i , ΔB _i , i = 1, 2, obtained during the sighting of two stars are remembered.

2. The absolute value ΔCos (D _ij ) is calculated, which is compared with a given threshold D ₀ .

3. When the condition is met

the decision is made that the stars selected from the catalog are endorsed.

The possibility of implementing the proposed astrocorrection method can be provided by means of an astroinertial navigation system, the essence of which is presented in the form of a block diagram in FIG. one.

The structure of the astroinertial navigation system structurally includes:

1 - teleblock;

2 - the angle sensor of the cardan suspension of the teleblock in azimuth;

3 - the angle sensor of the cardan suspension of the teleblock in height;

4 - engine working out the angle of the exhibition cardan suspension of the teleblock in azimuth;

5 - engine working out the angle of the exhibition cardan suspension telebloc height;

6 - on-board computer;

7 is a block of tracking systems for working out the teleblock pointing angles;

8 - the first difference scheme;

9 - the second difference scheme;

10 - the first block of correction;

11 - the second block of correction;

12 is a block calculating angular corrections;

13 - unit for calculating the absolute value of the difference between the calculated and actual coordinates of the sighted star;

14 is a block comparison;

15 is a block for calculating errors of the corrected system and the formation of the sign of readiness for corrective amendments;

16 is a block forming the sign of unavailability of corrective amendments.

The proposed method of astro correction is as follows.

(матрица разницы между расчетными и фактическими координатами звезды), который в блоке 14 сравнивается с заданным порогом D₀, и при выполнении условия (9) в блоке 15 формируется признак коррекции Пр.корр = 1 и вычисляется вектор β ошибок корректируемой системы, а при невыполнении этого условия в блоке 16 формируется Пр.корр = 0, свидетельствующий о неправильном формировании угловых поправок ΔA=A_т-A_i, ΔB=B_т-B_i при визировании первой, либо второй, либо обеих звезд.In the on-board digital computer 6, a pair of stars is selected from the star catalog that are available for sighting at a given point in the object’s location at a given time, and their Cartesian and angular coordinates are calculated. The calculated angular coordinates A _i , B _i , i = 1, 2 are output to the first inputs of the first and second difference schemes 8 and 9 of the block of tracking systems 7, to the other inputs of which the current angles A _t , B _t , teleblock 1 from the outputs of the angle sensors cardan gimbal of the teleblock in azimuth 2 and height 4. The resulting difference in angles ΔA _i , ΔB _i , where i = 1, 2 is the number of the selected star, are output to the inputs of the first and second correction blocks 10 and 11, forming control signals for cardan engines 4 and 5 a teleblock suspension working out target designations A _i , B _i , issued from the onboard computer. After target designation, the actual angular coordinates A _t , B _t are output from the output of the teleblock 1, which are fed to the inputs of the block for calculating angular corrections 12, the other inputs of which give the calculated values A _i , B _{i of} these angles, issued from the output of the on-board digital computer 6. Received differences ΔA = A _t -A _i , ΔB = B _t -B _i from the output of the block for calculating the angular corrections 12 are issued to the input of the block 13, where the module is calculated

(a matrix of the difference between the calculated and actual coordinates of the star), which in block 14 is compared with a given threshold D ₀ , and when condition (9) is fulfilled, in block 15 a correction sign Pr. Corr = 1 is generated and the error vector β of the corrected system is calculated, and when if this condition is not met, block Corr = 0 is formed in block 16, indicating the incorrect formation of angular corrections ΔA = A _t -A _i , ΔB = B _t -B _i when sighting the first, or second, or both stars.

In FIG. Figure 2 shows a graph of ΔCos (D _ij ) for errors in determining angular corrections ΔA _i , ΔB _i , i = 1, 2, which are random in nature and distributed according to a uniform law in the range of 0.1 angles. min

.In FIG. Figure 3 shows a graph of ΔCos (D _ij ) for the same errors in determining the angular corrections ΔA _i , ΔB _i , i = 1, 2, but errors between ΔA _i = 5 angles are simulated between the twelfth and seventeenth measurements. min and ΔB ₁ = 1 ang. min As can be seen from the graphs, this kind of error led to a sharp increase in the value

.

Claims (1)

The method of astro correction is that, based on the current coordinates and time, from the catalog of stars recorded in the on-board computer, a pair of stars is selected that is available for sighting at a given location of the object and at a given time, their coordinates are determined in the local coordinate system at the current time , target designations are formed in the form of teleblock targeting angles, the first of the selected stars is sighted by pointing the teleblock's sighting axis at the calculated point determined by the coordinates of the first of the selected a catalog of stars with the determination of its measured coordinates, angular corrections are determined that represent the differences between the measured and calculated values of the angles of its sight, the second of the stars selected from the catalog is sighted by pointing the target axis of the teleblock to the calculated point determined by the coordinates of the second of the stars selected from the catalog with the definition of its measured coordinates, angular corrections are determined that represent the differences between the measured and calculated values of the angles of its sight, characterized in that о, the absolute value of the difference between the calculated and measured angles of the selected pair of stars detected during their sequential sighting is calculated, which is compared with a predetermined threshold value and, if this value is not exceeded, a correction resolution sign is generated and these angular corrections are recalculated in the error estimation of the corrected inertial system.

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