RU2587666C1 - Method of identifying parameters of navigation satellites - Google Patents

Abstract

FIELD: communication.

SUBSTANCE: invention relates to methods for navigating based on satellite radio navigation systems (SRNS) and can be used to identify parameters of navigation satellites and improve accuracy of determining coordinates of a navigation receiver. Technical result is high accuracy of locating a navigation receiver. Said result is achieved due to compensation of occurring errors when determining coordinates of navigation receiver.

EFFECT: technical result is elimination of errors of mutual synchronisation hours navigation satellites and navigation receiver.

1 cl, 1 dwg

Description

The invention relates to navigation methods for Satellite Radio Navigation Systems (SRNS) and can be used to identify the parameters of navigation satellites and improve the accuracy of determining the coordinates of the navigation receiver. The technical result consists in increasing the accuracy of determining the coordinates of the navigation receiver by eliminating errors in the mutual synchronization of the clock of navigation satellites and the navigation receiver.

There are various ways to improve the accuracy of determining the coordinates of the navigation receiver. US Pat. No. 7,535,414 describes a method which assumes that before calculating the coordinates of the navigation receiver, the uncertainties caused including errors of the navigation satellite clock, in incomplete pseudo-ranges US Pat. No. 6,417,801 proposes the resolution of uncertainties in incomplete pseudorange by adding a correction to the measurement time in the vector of estimated parameters, followed by enumerating all valid integer combinations of ambiguities and selecting the necessary one according to the criterion of the minimum residual residuals.

Also, to improve the accuracy of determining the coordinates of the navigation receiver, various clock error compensation algorithms are used [GLONASS interface control document (5.1 edition). - M.: RNII KP, 2008. - 57 p.], And also uses a differential mode of measurements by code ranges, implemented using a control navigation receiver with known geographical coordinates - the so-called. base station [Bar-Sever, Y. Anew Massachusetts model for GPS yaw attitude // Journal of Geodesy, 70, 714723, 1996]. The disadvantages of these methods are the complexity of their implementation and the inability to accurately determine the current error values of the mutual synchronization of the clock of navigation satellites and the navigation receiver for their subsequent compensation.

Closest to the proposed invention is the method described in the patent of the Russian Federation No. 2432584. The method for determining the coordinates of the navigation receiver of the satellite radio navigation system / Vasiliev M.V., Mikhailov N.V., Pospelov S.S., Jalali Bidjan, which consists in the fact that the calculation of the corrections to the coordinates of the receiver is made after measuring the pseudorange and pseudo-velocity from the residual pseudorange.

The disadvantage of this method is the complexity of the hardware and computational implementation and the inability to accurately determine the current error values of the mutual synchronization of the clocks of navigation satellites and the navigation receiver for their subsequent compensation.

The claimed invention is aimed at solving the problem of improving the accuracy of determining the location of the navigation receiver by correcting the error of the mutual synchronization of the clocks of the navigation satellites and the navigation receiver.

The problem arises in the development of monitoring and control systems for navigation satellites, as well as the use of their measurements to solve the navigation problem of the object.

To ensure identification of the parameters of navigation satellites and simplify the hardware and computational implementation of this procedure, a method is proposed consisting in the fact that in a group of five navigation satellites located in the line of sight, simultaneous transmission of navigation messages from each satellite to each and their reception by each satellite are implemented from each, the determination of inter-satellite pseudorange and their transmission to another satellite with the subsequent solution on each satellite of the system of nineteen linear algorithms equations, as a result of which true distances between satellites, errors of mutual synchronization of satellite clocks and instrumental errors of transmitters are determined, after which errors of mutual synchronization of satellite clocks and instrumental errors of transmitters are transmitted in navigation messages and compensated in the navigation receiver when determining the coordinates of the navigation receiver based on the solution systems of three nonlinear equations, each of which is formed by the difference measured pseudorange between two satellites.

The accuracy of solving a navigation problem using satellite navigation means largely depends on the degree of suppression of interference arising from the reception and transmission of satellite messages. In the General case, the information structure of the satellite measurement of the pseudorange Z _R used as the main signal when positioning objects, taking into account the interference that most affects the positioning accuracy, has the form:

where ξ _s , η _s , ζ _s are the current coordinates of the satellite in the Greenwich coordinate system (GrSK),

ξ, η, ζ - the current coordinates of the object in GRSK,

C is the nominal value of the speed of light in vacuum,

Δτ is the error of the clock of the navigation receiver,

ΔT is the error of the satellite clock,

W _IT - errors due to the passage of the radio signal through the ionosphere and troposphere,

W _S - instrumental errors of the satellite transmitter.

Among the listed errors, the instrumental errors of the satellite transmitter and the errors of the clocks of the satellite and receiver have the most significant share. So, for example, despite the installation of an atomic clock on navigation satellites, the mean square error of the mutual synchronization of the onboard time scales can reach 20 or more ns [GLONASS. Interface control document / Navigation radio signal in the L1, L2 bands with open access and frequency division (Version 5.1). 2008. - 74 p.].

At present, various algorithms based on its approximation by time polynomials are used to compensate for clock errors. For example, in the GLONASS SNA, the satellite clock error ΔT is approximated by a linear time dependence with specified parameters (a quadratic dependence is used in GPS):

where t ^* is the time of calculating the error at the time of satellite information, α ₀ , α ₁ are the known parameters of the satellite clock error model, T _G is the delay time of the satellite signal, T _P is the relativistic correction determined in the process of calculating the satellite coordinates. As can be seen from (2), the compensation model contains 4 (!) Parameters that require an additional difficult determination with different periodicities, which reduces the overall efficiency of the model (2). Moreover, algorithms for compensating the instrumental errors of the satellite transmitter are currently completely absent.

The existing GLONASS and GPS navigation systems, in order to improve the accuracy of solving the navigation problem, are currently undergoing extensive modernization, which allows, in particular, determining the distance between satellites located in direct line of sight using on-board measuring instruments.

So, for example, GLONASS-M navigation satellites are equipped with on-board inter-satellite measurement equipment [GLONASS. The principles of construction and operation / Ed. A.I. Perova, V.N. Harisova. - 3rd ed., Revised. - M .: Radio engineering, 2005. - 688 p.], And GLONASS-K navigation satellites - by the receiving-forming device of the inter-satellite radio line [Stupak GG, Revnyvykh SG, Ignatovich EI, Kurshin VV, Betanov V.V., Panov S.S., Bondarev N.Z., Chebotarev V.E., Reshetneva M.F., Balashova N.N., Serdyukov A.I., Sintsova L.N. // Choice of the structure of the orbital grouping of the GLONAS perspective system // Cosmonautics No. 3-4 (6) 2013, S. 4-11]. The forming part of the inter-satellite radio link device generates and emits information-measuring radio signals, the structure of which is similar to the structure of the GLONASS navigation signal. In the receiving part, radio signals are amplified and the pseudo-speed and pseudorange are measured between the navigation satellites of the GLONASS system.

Improving the accuracy of determining the position of navigation satellites is also possible when using laser rangefinders [Chubykin AA, Roy Yu.A., Kornishev OM, Padun P.P. The use of onboard laser measuring and connected means to improve the accuracy and efficiency of EVO satellites of the GLONASS system // EV & ES. T. 12. 2007. S. 25-30, Shargorodsky V.D., Chubykin A.A., Sumerin V.V. Inter-satellite laser navigation and communications system // Aerospace Courier. 2007. No1 (49). P. 88-89], which is based on the principle of measuring the propagation time of laser pulses.

It is obvious that the measurement signals of pseudorange between the ith and jth satellites will be free from errors caused by the passage of the signal through the ionosphere and troposphere as in (1), and will have the form:

where Z _ij is the pseudorange measured on the jth satellite,

R _ij is the true range between the i-th and j-th satellites,

ΔT _j is the error of the clock of the j-th satellite,

ΔT _i - clock error of the i-th satellite,

W _Si is the error of the transmitter of the i-th satellite,

ΔT _ji = c (ΔT _j -ΔT _i ) is the error of mutual synchronization of the clocks of the i-th and j-th satellites.

Before constructing an algorithm for identifying the desired spatio-temporal parameters of satellites, we first determine the number of satellites N, which is necessary and sufficient for their complete identification. The number of all possible distances between N satellites (equal to the number of edges of the graph with N vertices) is determined by the well-known expression: N (N-1) / 2. In the mutual measurement of the distances between two satellites, the number of measured inter-satellite ranges will be, respectively, N (N-1). The obtained measurements contain the following unknown variables: N (N-1) / 2 true distances between N satellites, (N-1) linearly independent errors of mutual synchronization of clocks of N satellites (the rest (N-1) (N / 2-1) are determined their linear combinations) and N instrumental errors of the transmitters of N satellites, i.e. the total number of unknown variables is N (N-1) / 2 + N-1 + N. Equating the total number of measurements to the number of unknown variables, we have the following equation:

N (N-1) / 2 = 2N-1

or

N ² -5N + 2 = 0,

from which the number of satellites is easily determined, which is necessary and sufficient to solve the identification problem posed:

N = 5.

(If the true distances between the satellites are known - for example, measured with high accuracy by laser range finders, then the number of unknown variables is reduced to 2N-1 and the equation determining the number of satellites takes the form: N ² -3N + 1 = 0, whence N = 3) .

In the accepted notation, the measured distances (pseudorange) Z _ij between the five navigation satellites 1 _i , i = 1.5 (Fig. 1) can be represented as follows:

where ΔT ₁₂ , ΔT ₁₃ , ΔT ₅₃ , ΔT ₂₃ ... ΔT ₃₄ , ΔT ₅₄ , ΔT ₂₄ - errors of mutual synchronization of the clocks of satellites 1 ₁ , 1 ₂ , 1 ₃ , 1 ₄ and 1 ₅ ,

R ₁₃ , R ₂₃ , R ₁₂ ... R ₅₃ , R ₂₄ , R ₅₄ - true ranges between satellites,

W _S1 , W _S2 , W _S3 , W _S4 , W _S5 are the instrumental errors of the transmitters of the satellites 1 ₁ , 1 ₂ , 1 ₃ , 1 ₄ and 1 ₅ , respectively.

Given the obvious relationships:

ΔT _ji = -ΔT _ij , ΔT _jk = ΔT _ik -ΔT _ij = ΔT _k -ΔT _j , i, j, k = 1, 2 ... 5,

system (4) of 20 equations with 35 unknowns can be reduced to a system of 20 equations with 19 unknowns - ten true ranges R ₁₃ , R ₂₃ , R ₁₂ , ..., R ₄₃ , R ₂₄ , R ₅₄ , four independent errors of clock synchronization satellites (the choice of the determined errors is of no fundamental importance, therefore, we will choose the errors ΔT ₁₂ , ΔT ₁₃ , ΔT ₁₄ , ΔT ₁₅ as independent variables) and instrumental errors of the transmitters W _S1 , W _S2 , W _S3 , W _S4 , W _S5 :

систем уравнений, аналогичных (5), для их параллельного решения с целью повышения точности идентификации - за счет, например, усреднения полученных результатов. В данном случае решается не только задача текущего определения погрешностей взаимной синхронизации часов всех спутников и инструментальных погрешностей их передатчиков, используемых, как показано далее, для компенсации помех в сигнале навигационного приемника объекта, но и расстояний между спутниками, используемых, в свою очередь, в качестве дополнительной информации для повышения точности измерения текущего местоположения спутников.and is easily solved by any of the known methods for solving linear algebraic equations directly on board each of the satellites 1 ₁ , 1 ₂ , 1 ₃ , 1 ₄ and 1 ₅ . Because however, one redundant equation can be excluded, there is the possibility of additional formation $$C_{\mathrm{twenty}}^{19}-\mathrm{one}=19$$

systems of equations similar to (5) for their parallel solution in order to increase the accuracy of identification - for example, by averaging the results. In this case, not only the problem of the current determination of the errors of mutual synchronization of the clocks of all satellites and the instrumental errors of their transmitters, used, as shown below, to compensate for interference in the signal of the navigation receiver of the object, but also the distances between the satellites, used, in turn, is solved additional information to improve the accuracy of measuring the current location of satellites.

Thus, the determination of all the parameters mentioned above allows the identification of both the distances between the satellites and the synchronization errors of their own clocks and instrumental errors of the transmitters.

Compensation of errors in satellite communications in a navigation receiver is based on the fact that for solving a navigation problem satellite communications are received, as a rule, from at least four satellites [GLONASS. The principles of construction and operation / Ed. A.I. Perova, V.N. Harisova. - 3rd ed., Revised. - M .: Radio engineering, 2005. - 688 p.], Which allows you to generate various linear combinations of signals received from different satellites. So, the difference of the pseudorange signals received from two satellites - i-th and j-th, taking into account (1), has the form:

where the assumption arising from the practice of satellite navigation is accepted that interference is identical due to the passage through the ionosphere and troposphere of the radio signals of satellites located in the field of view of the same object.

As can be seen from (6), the difference of the signals Z _Ri -Z _{Rj of} any two satellites contains interference components ΔT _ij , W _Si , W _Sj , which are already known from the received satellite message and can be compensated (and does not contain the remaining interference given in ( 1): receiver clock errors, its instrumental errors, etc.).

As a result, processing — using the standard iterative procedure for solving the system of nonlinear equations (7) with respect to the coordinates ξ, η, ζ — is subject to signals containing only true information about the coordinates of the object, which can significantly increase the overall accuracy of solving the navigation problem:

where ΔZ _ij is the difference of the pseudorange received from the i-th and j-th satellites;

ΔZ _ik is the difference of the pseudorange received from the i-th and k-th satellites;

ΔZ _kj is the difference of the pseudoranges received from the kth and jth satellites.

The algorithm for the technical implementation of the proposed method is considered in steps using the example of satellite 1 (Fig. 1).

1. Transmission of navigation messages to satellites 1 ₂ , 1 ₃ , 1 ₄ , 1 ₅ .

2. Reception of navigation messages from satellites 1 ₂ , 1 ₃ , 1 ₄ , 1 ₅ (performed simultaneously with p. 1).

3. Determination of pseudorange Z ₂₁ , Z ₃₁ , Z ₄₁ , Z ₅₁ to satellites 1 ₂ , 1 ₃ , 1 ₄ , 1 ₅ .

4. Parallel transmission of the obtained pseudorange values Z ₂₁ , Z ₃₁ , Z ₄₁ , Z ₅₁ to satellites 1 ₂ , 1 ₃ , 1 ₄ , 1 ₅ .

5. Reception of pseudorange values Z ₁₂ , Z ₃₂ , Z ₄₂ , Z ₅₂ from satellite 1 ₂ (performed simultaneously with step 4).

6. Reception of pseudorange values Z ₁₃ , Z ₂₃ , Z ₄₃ , Z ₅₃ from satellite 1 ₃ (performed simultaneously with step 4).

7. Reception of pseudorange values Z ₁₄ , Z ₂₄ , Z ₃₄ , Z ₅₄ from satellite 1 ₄ (performed simultaneously with step 4).

8. Reception of pseudorange values Z ₁₅ , Z ₂₅ , Z ₄₅ , Z ₃₅ from satellite 1 ₅ (performed simultaneously with step 4).

9. The solution of the system of equations (5) and the calculation of the true ranges R ₁₃ , R ₂₃ , R ₁₂ , ..., R ₅₃ , R ₂₄ , R ₅₄ ; errors of mutual synchronization of the clock ΔT ₁₂ , ΔT ₁₃ , ΔT ₁₄ , ΔT ₁₅ and instrumental errors of the transmitters W _S1 , W _S2 , W _S3 , W _S4 , W _S5 .

10. The transmission in the satellite message of the true ranges R _ij between all satellites, the errors of mutual clock synchronization and the values of the instrumental errors of the transmitters for subsequent correction of satellite measurements (1).

11. The solution of the system of equations (7) and the calculation of the coordinates of the navigation receiver.

The proposed method for identifying the parameters of navigation satellites allows, using simple methods of radio and laser measurements, firstly, to significantly improve the accuracy of clock synchronization on all navigation satellites of the group (which is especially important for the GLONASS system, whose ground time synchronization stations are located only in the Russian Federation ), secondly, to determine the true ranges R _ij between satellites directly on board the satellite, thereby reducing the computational load on consumer receivers and those lemetric tracking stations, and, thirdly, to increase the overall accuracy of solving the navigation problem by compensating for the main interference in the received navigation message. At the same time, an increase in the accuracy of the determination of the considered spatio-temporal parameters is also inevitable due to the greater accuracy of inter-satellite measurements performed in space, compared with telemetric ones subject to atmospheric disturbances.

Claims (1)

A method for identifying the parameters of navigation satellites, which consists in the fact that in a group of five navigation satellites located in the line of sight, there are simultaneous transmission of navigation messages from each satellite to each and their reception by each satellite from each, determination of inter-satellite pseudorange and their transmission to another satellite with the subsequent solution on each satellite of the system of nineteen linear algebraic equations, as a result of which the true distances between the satellites are determined, errors of mutual synchronization of satellite clocks and instrumental errors of transmitters, after which errors of mutual synchronization of satellite clocks and instrumental errors of transmitters are transmitted in navigation messages and compensated in the navigation receiver when determining the coordinates of the navigation receiver based on the solution of a system of three nonlinear equations, each of which is formed by the difference of the measured pseudorange between two satellites.

Images