Relativistic navigation reference deviation calibration method based on fixed star and pulsar information fusion

Abstract

The invention relates to a relativistic navigation reference deviation calibration method for fusing fixed star and pulsar information, which comprises the following steps of: configuring a fixed star angular distance measurement sensor and an X-ray detector on a spacecraft, observing a fixed star through the fixed star angular distance measurement sensor, extracting fixed star aberration caused by the movement of the spacecraft, and calibrating the fixed star aberration; the navigation information is contained in two relativistic effects of light gravitational deflection caused by a celestial body gravitational field; observing the pulsar through an X-ray detector to obtain a pulse time difference of arrival observed quantity; the method comprises the following steps: performing state prediction by combining a spacecraft and an earth orbit dynamics model, and correcting a state prediction value by expanding a Kalman filter, processing a fixed star angular distance and a pulse arrival time difference observed quantity to obtain estimated values of a spacecraft position and speed, a geocentric position and speed and a sensor system error parameter; therefore, the calibration of two kinds of reference deviations, namely the ground ephemeris error and the sensor system error, is realized. The invention provides a new way for improving the performance of the relativistic navigation system.

Description

Technical Field

[0001] The invention relates to a relativistic navigation reference deviation calibration method for fusion of star and pulsar information, belonging to the technical field of navigation and guidance. Background Art

[0002] Astronomical navigation based on observation of natural celestial bodies is a traditional technical means to achieve autonomous navigation of spacecraft. It includes "starlight + horizon", X-ray pulsars, etc. The navigation accuracy verified in orbit can only reach the km level, and it is difficult to break through the positioning accuracy level of 100 meters.

[0003] The basic method of relativistic navigation is to observe stars in different sky regions through multi-aperture star angular distance measurement sensors to obtain star angular distance observations associated with star aberration and light gravitational deflection. On this basis, the star angular distance observations are processed by navigation filters, and combined with the spacecraft orbital dynamics model, the spacecraft's position, velocity and other motion states are estimated. Relativistic navigation technology can be used for earth orbit communication, navigation, remote sensing satellite platforms, and earth-moon space cruise vehicles. In the absence of ground station / GNSS (Global Navigation Satellite System) support, it maintains the autonomous operation of spacecraft and provides input information for configuration maintenance, trajectory planning and maneuvering control. The relativistic navigation reference deviation includes sensor system error and earth ephemeris error. Affected by factors such as the space environment, there are systematic errors in the star angular distance observations obtained by multi-aperture star angular distance measurement sensors, resulting in a decrease in the performance of the relativistic navigation system. However, in the process of relativistic navigation data processing, the velocity information of the earth's center relative to the center of mass of the solar system is required. Limited by the current measurement technology conditions, the earth's center velocity calculated based on the earth ephemeris has errors, which has an adverse effect on the accuracy of relativistic navigation. Datum deviation is one of the main error sources of relativistic navigation system. The existing technology in this field cannot effectively solve the problem of relativistic navigation datum deviation calibration. Summary of the invention

[0004] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art, to address the problem that the benchmark deviation (including sensor system error and earth ephemeris error) affects the performance of the relativistic navigation system, and to provide a relativistic navigation benchmark deviation calibration method that fuses star and pulsar information. The method can be used for earth orbit spacecraft and can also be extended to deep space exploration missions, and has important application value.

[0005] The technical solution of the present invention is: in the first aspect, a relativistic navigation reference deviation calibration method for fusion of star and pulsar information is provided, wherein:

[0006] S1 uses the extended Kalman filter as the navigation filter and initializes it, setting the initial value of the state vector representing the position and velocity of the Earth orbit spacecraft relative to the center of the Earth, the position and velocity of the center of the Earth relative to the center of mass of the solar system, and the error parameters of the sensor system;

[0007] S2 predicts the position and velocity of the spacecraft relative to the center of the Earth based on the orbital dynamics model of the Earth-orbiting spacecraft and obtains the corresponding predicted values. It predicts the position and velocity of the center of the Earth relative to the center of mass of the solar system based on the orbital dynamics model of the Earth and obtains the corresponding predicted values.

[0008] S3 observes stars through the star angular distance measurement sensor configured on the earth orbit spacecraft to obtain the star angular distance observation value;

[0009] S4, when the stellar angular distance observation value is available, the stellar angular distance observation value obtained in step S3 is substituted into the extended Kalman filter for calculation, and the predicted values ​​of the position and velocity of the spacecraft relative to the center of the earth, the predicted values ​​of the position and velocity of the center of the earth relative to the center of mass of the solar system, and the sensor system error parameters obtained in step S2 are corrected;

[0010] S5 observes pulsars through X-ray detectors installed on earth-orbiting spacecraft to obtain the observed time difference of pulse arrival of pulsars;

[0011] S6, when the pulse arrival time difference observation is available, substitute the pulse arrival time difference observation obtained in step S5 into the extended Kalman filter for calculation, and correct the predicted values ​​of the position and velocity of the spacecraft relative to the center of the earth, the predicted values ​​of the position and velocity of the center of the earth relative to the center of mass of the solar system, and the sensor system error parameters obtained in step S2;

[0012] S7 returns to step S2 for iteration, and stops iteration when the statistical value of the filtered new information is less than a given threshold, to obtain the estimated values ​​of the position and velocity of the spacecraft relative to the center of the earth, the estimated values ​​of the position and velocity of the center of the earth relative to the center of mass of the solar system, and the estimated values ​​of the error parameters of the sensor system, thereby completing the calibration of the relativistic navigation reference deviation of the fusion of stellar and pulsar information.

[0013] Preferably, the method for initializing the extended Kalman filter as the navigation filter in step S1 is: setting the state vector estimate of the extended Kalman filter at the initial time k=0 for:

[0014]

[0015] in, and They represent the estimated values ​​of the position vector and velocity vector of the Earth orbit spacecraft relative to the center of the Earth at the initial moment, and They represent the estimated values ​​of the position vector and velocity vector of the Earth’s center relative to the solar system’s mass center at the initial moment, represents the estimated value of the sensor system error parameter at the initial moment, It is obtained based on a priori knowledge of the position and velocity of the Earth-orbiting spacecraft, the position and velocity of the Earth's center relative to the center of mass of the solar system, and the system error parameters of the star angular distance measurement sensor.

[0016] Preferably, the method for predicting the position and velocity of the spacecraft relative to the center of the earth, and the position and velocity of the center of the earth relative to the center of mass of the solar system in step S2 is: the state vector prediction value of the extended Kalman filter at time k Calculated according to the following formula:

[0017]

[0018] State transfer function The form is:

[0019]

[0020] Where τ represents the time step of one-step prediction in the extended Kalman filter, and the subscript k represents different moments. Represents the state vector estimate of the extended Kalman filter at time k-1; nonlinear function The form is:

[0021]

[0022] in, represents the estimated value of the velocity vector of the Earth orbit spacecraft relative to the center of the Earth at time k-1, represents the estimated value of the position vector of the Earth orbit spacecraft relative to the center of the Earth at time k-1, represents the estimated value of the velocity vector of the Earth relative to the center of mass of the solar system at time k-1, represents the estimated value of the position vector of the Earth's center relative to the center of mass of the solar system at time k-1, μ E represents the Earth's gravitational constant, represents the known spacecraft orbit perturbation function, which is obtained according to the orbital dynamics model of the spacecraft, μ S is the solar gravitational constant, represents the known Earth orbit perturbation function, which is obtained based on the Earth's orbital dynamics model, and m represents the number of sensor system error parameters.

[0023] Preferably, the star angular distance observation value y in step S3 isS,k The calculation method is:

[0024]

[0025] in, represents the observed angular distance of the i-th star at time k, i = 1, 2, ..., m, y S,k Obtained by observing stars using stellar angular distance measurement sensors installed on Earth-orbiting spacecraft.

[0026] Preferably, in step S4, the method for correcting the predicted values ​​of the position and velocity of the spacecraft relative to the center of the earth, the predicted values ​​of the position and velocity of the center of the earth relative to the center of mass of the solar system, and the sensor system error parameters is:

[0027]

[0028] in, represents the estimated value of the state vector of the extended Kalman filter at time k, represents the state vector prediction value of the extended Kalman filter at time k, y S,k represents the observed angular distance of the star, K S,k The Kalman gain matrix corresponding to the observed angular distance of the star is calculated based on the previously established relativistic navigation system model. The observation function The form is:

[0029]

[0030] in, (i=1,2,…,m) represents the observed angular distance corresponding to the i-th star The observation function of is:

[0031]

[0032]

[0033] Among them, u I ′ Ak and u I ′ Bk It represents the projection of the line-of-sight direction vector of a star measured by a stationary observer in an inertial coordinate system. It can be calculated based on a previously established star catalog. The subscripts A and B are used to distinguish different stars. c represents the speed of light. and Respectively Predicted values ​​of medium-Earth orbit spacecraft velocity, geocentric velocity, and sensor system error parameters.

[0034] Preferably, the pulse arrival time difference observation value y in step S5 is X,k for:

[0035]

[0036] in, represents the observed value of the arrival time difference of the jth pulse at time k, j = 1, 2, ..., n, y X,k The timing of pulsars is obtained by observing them with X-ray detectors installed on Earth-orbiting spacecraft and comparing them with a previously established pulsar timing model.

[0037] Preferably, in step S6, the method for correcting the predicted values ​​of the position and velocity of the spacecraft relative to the center of the earth, the predicted values ​​of the position and velocity of the center of the earth relative to the center of mass of the solar system, and the sensor system error parameters is:

[0038]

[0039] in, represents the state vector prediction value of the extended Kalman filter at time k, K X,k represents the Kalman gain matrix corresponding to the pulse arrival time difference observation, which is calculated according to the previously established pulsar navigation system model, y X,k represents the pulse arrival time difference observation, the observation function The form is:

[0040]

[0041] in, (j=1,2,…,n) represents the observed angular distance corresponding to the jth star The observation function of is:

[0042]

[0043] Among them, n (j) represents the line-of-sight direction vector of the j-th pulsar, represents the distance from the center of mass of the solar system to the jth pulsar, which can be calculated based on the previously established pulsar catalog. b represents the position vector of the center of mass of the solar system relative to the center of the sun, which can be calculated based on the previously established solar ephemeris. and Respectively Predicted values ​​of the medium earth orbit spacecraft position and the center of the earth, μ s represents the solar gravitational constant.

[0044] Preferably, the recursive calculation method of the statistical value of the filtered new information in step S7 is:

[0045]

[0046] Among them, S k represents the statistical value of the new filtered information at time k, s k-1 represents the statistical value of the filtering innovation at time k-1. The initial value S0 of the statistical value of the filtering innovation is set to a normal number greater than the specified threshold. l represents the total number of sampled data in the pre-specified time window. Represents the filtering innovation, which is calculated as follows:

[0047]

[0048] The method for judging whether the statistical value of the filtered innovation is less than a given threshold is:

[0049]

[0050] Then it is judged that the statistical value of the filtered new information is less than the given threshold, where, For a given threshold, it can be set in advance according to the accuracy index of the star angular distance measurement sensor.

[0051] In a second aspect, a relativistic navigation reference deviation calibration system for stellar and pulsar information fusion is provided, characterized in that it includes:

[0052] State initialization module: Initializes the extended Kalman filter used as a navigation filter, sets the initial value of the state vector representing the position and velocity of the Earth orbit spacecraft relative to the center of the Earth, the position and velocity of the center of the Earth relative to the center of mass of the solar system, and the error parameters of the sensor system;

[0053] State prediction module: Based on the orbital dynamics model of the Earth-orbiting spacecraft, the position and velocity of the spacecraft relative to the center of the Earth are predicted; based on the orbital dynamics model of the Earth, the position and velocity of the center of the Earth relative to the center of mass of the solar system are predicted;

[0054] Stellar observation module: observe stars on the celestial sphere through the star angular distance measurement sensor configured on the earth orbit spacecraft, and use the multi-aperture optical system on the star angular distance measurement sensor to observe multiple stars and obtain the angle of the star line of sight direction vector, that is, the star angular distance observation value;

[0055] Correction module based on star observation: When the star angular distance observations of the star angular distance measurement sensor are available, the star angular distance observations are processed by the extended Kalman filter to correct the predicted values ​​of the spacecraft's position and velocity relative to the center of the earth, the predicted values ​​of the position and velocity of the center of the earth relative to the center of mass of the solar system, and the sensor system error parameters;

[0056] Pulsar observation module: observe pulsars through X-ray detectors configured on earth-orbiting spacecraft, and use the multi-aperture optical system on the X-ray detector to observe multiple pulsars, and obtain the difference between the time when the pulse signal emitted by the pulsar arrives at the center of mass of the solar system and the time when it arrives at the spacecraft, that is, the pulse arrival time difference observation;

[0057] Correction module based on pulsar observations: When the pulse arrival time difference observations of the X-ray detector are available, the pulse arrival time difference observations are processed by the extended Kalman filter to correct the predicted values ​​of the spacecraft position and velocity relative to the center of the earth, the predicted values ​​of the position and velocity of the center of the earth relative to the center of mass of the solar system, and the sensor system error parameters.

[0058] Compared with the prior art, the present invention has the following advantages:

[0059] (1) The present invention expresses the position and velocity of the Earth's center relative to the center of mass of the solar system, as well as the error parameters of the sensor system for measuring the angular distance of stars, in the form of a state vector in the model, and establishes a reference deviation calibration model. By expanding the state dimension of the navigation filter, the present invention lays a foundation for the estimation of the position and velocity of the Earth's center, as well as the identification of the error parameters of the sensor system, and effectively solves the problem of relativistic navigation reference deviation calibration, achieving the effect of accurate estimation and effective compensation of reference deviation.

[0060] (2) The present invention introduces pulsar measurement information into the relativistic navigation system, observes pulsars through X-ray detectors, provides auxiliary measurement information for the on-orbit calibration of the benchmark deviation, integrates the stellar angular distance and pulse arrival time observations, and uses the extended Kalman filter to achieve accurate estimation of the state vector, thereby effectively suppressing the influence of the benchmark deviation, improving the performance of the relativistic navigation system, and achieving a navigation and positioning accuracy level of hundreds of meters. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 It is the overall flow chart of the present invention;

[0062] Figure 2 A spacecraft position estimation error curve diagram of the fusion of star and pulsar information according to an embodiment of the present invention;

[0063] Figure 3 A spacecraft velocity estimation error curve diagram of the fusion of star and pulsar information according to an embodiment of the present invention;

[0064] Figure 4 A graph showing an error curve of the geocentric position estimation of the fusion of star and pulsar information according to an embodiment of the present invention;

[0065] Figure 5 A graph showing an error curve of geocentric velocity estimation for stellar and pulsar information fusion according to an embodiment of the present invention;

[0066] Figure 6 This is a curve diagram of the system error parameter estimation error of the stellar and pulsar information fusion according to an embodiment of the present invention. DETAILED DESCRIPTION

[0067] The specific embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0068] In order to solve the problem that the performance of relativistic navigation system is easily affected by reference deviation, the present invention proposes a relativistic navigation reference deviation calibration method by fusing star and pulsar information, fusing the star angular distance observation provided by the star angular distance measurement sensor and the pulse arrival time difference observation provided by the X-ray detector, and designing an extended Kalman filter based on the "prediction-correction" structure in combination with the spacecraft orbital dynamics model, so as to realize the accurate estimation of the spacecraft position, velocity and the main model parameters used to characterize the reference deviation, which is helpful to realize the long-term high-precision autonomous navigation of the spacecraft.

[0069] The present invention proposes a relativistic navigation reference deviation calibration method based on the fusion of star and pulsar information. Figure 1 As shown, the steps are as follows:

[0070] (1) Initializing the extended Kalman filter as a navigation filter, setting the initial value of the state vector representing the position and velocity of the Earth orbit spacecraft relative to the Earth, the position and velocity of the Earth relative to the center of mass of the solar system, and the sensor system error parameter; the method for initializing the extended Kalman filter as a navigation filter is: setting the estimated value of the state vector of the extended Kalman filter at the initial time k = 0 to

[0071]

[0072] in, and They represent the estimated values ​​of the position vector and velocity vector of the Earth orbit spacecraft relative to the Earth at the initial moment, and They represent the estimated values ​​of the position vector and velocity vector of the Earth relative to the mass center of the solar system at the initial moment, represents the estimated value of the sensor system error parameter at the initial moment, It is obtained based on a priori knowledge of the position and velocity of the Earth-orbiting spacecraft, the position and velocity of the Earth relative to the center of mass of the solar system, and the system error parameters of the star angular distance measurement sensor.

[0073] (2) Based on the orbital dynamics model of the Earth-orbiting spacecraft, the position and velocity of the spacecraft relative to the center of the Earth are predicted, and based on the orbital dynamics model of the Earth, the position and velocity of the Earth relative to the center of mass of the solar system are predicted; the method for predicting the position and velocity of the spacecraft relative to the center of the Earth, and the position and velocity of the Earth relative to the center of mass of the solar system is as follows: The state vector prediction value of the extended Kalman filter at time k is calculated according to the following formula:

[0074]

[0075] State transfer function The form is:

[0076]

[0077] Among them, τ represents the time step of one-step prediction in the extended Kalman filter, the subscript k is used to distinguish different moments, and the nonlinear function The form is

[0078]

[0079] Among them, μ E represents the Earth's gravitational constant, represents the known spacecraft orbit perturbation function, which is obtained according to the orbital dynamics model of the spacecraft, μ S is the solar gravitational constant, represents the known Earth orbit perturbation function, which is obtained based on the Earth's orbital dynamics model, and m represents the number of sensor system error parameters.

[0080] (3) The stars on the celestial sphere are observed by a stellar angular distance measurement sensor configured on an earth-orbiting spacecraft to obtain the stellar angular distance observation value; the stellar angular distance observation value of the stellar angular distance measurement sensor is

[0081]

[0082] in, represents the observed angular distance of the i-th star at time k, i = 1, 2, ..., m, y S,k Obtained by observing stars using stellar angular distance measurement sensors installed on Earth-orbiting spacecraft.

[0083] (4) When the stellar angular distance observations of the stellar angular distance measurement sensor are available, the stellar angular distance observations obtained in step (3) are processed by an extended Kalman filter to correct the predicted values ​​of the position and velocity of the spacecraft relative to the earth, the predicted values ​​of the position and velocity of the earth relative to the center of mass of the solar system, and the sensor system error parameters obtained in step (2); the method for correcting the predicted values ​​of the position and velocity of the spacecraft relative to the earth, the predicted values ​​of the position and velocity of the earth relative to the center of mass of the solar system, and the sensor system error parameters is as follows:

[0084]

[0085] in, represents the state vector estimate of the extended Kalman filter at time k, K S,k The Kalman gain matrix corresponding to the observed angular distance of the star is calculated based on the previously established relativistic navigation system model. The observation function The form is

[0086]

[0087] in, (i=1,2,…,m) indicates the value corresponding to the i-th observation The observation function of

[0088]

[0089]

[0090] Among them, u I ′ Ak and u I ′ Bk It represents the projection of the line-of-sight direction vector of a star measured by a stationary observer in the inertial coordinate system, which can be calculated based on a previously established star catalog. The subscripts A and B are used to distinguish different stars. c represents the speed of light. and Respectively Predicted values ​​of medium-Earth orbit spacecraft velocity, Earth velocity, and sensor system error parameters.

[0091] (5) Pulsars are observed by X-ray detectors on Earth-orbiting spacecraft to obtain the observed pulse arrival time difference. The observed pulse arrival time difference of the X-ray detector is

[0092]

[0093] in, represents the observed value of the arrival time difference of the jth pulse at time k, j = 1, 2, ..., n, y X,k The timing of pulsars is obtained by observing them with X-ray detectors installed on Earth-orbiting spacecraft and comparing them with a previously established pulsar timing model.

[0094] (6) When the pulse arrival time difference observation of the X-ray detector is available, the pulse arrival time difference observation obtained in step (5) is processed by an extended Kalman filter to correct the predicted values ​​of the position and velocity of the spacecraft relative to the earth, the predicted values ​​of the position and velocity of the earth relative to the center of mass of the solar system, and the sensor system error parameters obtained in step (2); the method for correcting the predicted values ​​of the position and velocity of the spacecraft relative to the earth, the predicted values ​​of the position and velocity of the earth relative to the center of mass of the solar system, and the sensor system error parameters is as follows:

[0095]

[0096] Among them, K X,k The Kalman gain matrix corresponding to the pulse arrival time difference observation is calculated based on the previously established pulsar navigation system model. The observation function The form is

[0097]

[0098] in, (j=1,2,…,n) indicates the value corresponding to the jth observation The observation function of

[0099]

[0100] Among them, n (j) represents the line-of-sight direction vector of the j-th pulsar, represents the distance from the center of mass of the solar system to the jth pulsar, which can be calculated based on the previously established pulsar catalog. b represents the position vector of the center of mass of the solar system relative to the center of the sun, which can be calculated based on the previously established solar ephemeris. and Respectively Predicted values ​​of medium-Earth orbit spacecraft position and Earth position.

[0101] (7) Steps (2) to (6) are iterated repeatedly to obtain the estimated values ​​of the spacecraft's position and velocity relative to the Earth, the estimated values ​​of the Earth's position and velocity relative to the solar system's center of mass, and the estimated values ​​of the sensor system error parameters, thereby completing the relativistic navigation reference bias calibration of the stellar and pulsar information fusion.

[0102] Furthermore, the present invention also proposes a relativistic navigation reference deviation calibration system for stellar and pulsar information fusion, comprising:

[0103] State initialization module: Initializes the extended Kalman filter used as a navigation filter, sets the initial value of the state vector representing the position and velocity of the Earth-orbiting spacecraft relative to the Earth, the position and velocity of the Earth relative to the center of mass of the solar system, and the error parameters of the sensor system;

[0104] State prediction module: Based on the orbital dynamics model of the Earth-orbiting spacecraft, the position and velocity of the spacecraft relative to the center of the Earth are predicted. Based on the orbital dynamics model of the Earth, the position and velocity of the Earth relative to the center of mass of the solar system are predicted.

[0105] Stellar observation module: observe stars on the celestial sphere through the star angular distance measurement sensor configured on the earth orbit spacecraft, and use the multi-aperture optical system on the star angular distance measurement sensor to observe multiple stars and obtain the angle of the star line of sight direction vector, that is, the star angular distance observation value;

[0106] Correction module based on star observation: When the star angular distance observations of the star angular distance measurement sensor are available, the star angular distance observations are processed by the extended Kalman filter to correct the predicted values ​​of the spacecraft's position and velocity relative to the earth, the predicted values ​​of the earth's position and velocity relative to the solar system's center of mass, and the sensor system error parameters;

[0107] Pulsar observation module: observe pulsars through X-ray detectors configured on earth-orbiting spacecraft, and use the multi-aperture optical system on the X-ray detector to observe multiple pulsars, and obtain the difference between the time when the pulse signal emitted by the pulsar arrives at the center of mass of the solar system and the time when it arrives at the spacecraft, that is, the pulse arrival time difference observation;

[0108] Correction module based on pulsar observations: When the pulse arrival time difference observations of the X-ray detector are available, the pulse arrival time difference observations are processed by the extended Kalman filter to correct the predicted values ​​of the spacecraft's position and velocity relative to the Earth, the predicted values ​​of the Earth's position and velocity relative to the center of mass of the solar system, and the sensor system error parameters.

[0109] The present invention carries out the research on the evolution analysis of relativistic navigation error, establishes the calibration model of relativistic navigation benchmark deviation, and designs a relativistic navigation benchmark deviation calibration method by fusing stellar and pulsar information on this basis. By introducing auxiliary measurement information, reconstructing the navigation system model and optimizing the design of the navigation filter, the influence of the benchmark deviation is weakened and the accuracy of relativistic navigation is improved.

[0110] Example:

[0111] Taking the autonomous navigation of earth-orbiting spacecraft as an example, the effectiveness of the method described in the present invention is verified through simulation examples. It is assumed that the spacecraft is flying around the earth in a medium earth orbit (MEO) and its attitude remains stable relative to the earth. A stellar angular distance measurement sensor with star observation capability and an X-ray detector with pulsar observation capability are installed on the spacecraft. In the mathematical simulation process, it is assumed that the standard deviation of the angular measurement random error of the stellar angular distance measurement sensor is 1mas, the sensor system error is 0.5mas, and the data update frequency is set to 0.1Hz; the effective area of ​​the X-ray detector is 1m 2 , respectively, point to the three pulsars B0531+21, B1821-24 and B1937+21, and the observation time for each cycle is 1000s; the simulation time is 3 days. The position and velocity of the spacecraft relative to the earth, the position and velocity of the earth relative to the center of mass of the solar system, and the sensor system error parameters are determined by the stellar angular distance observations provided by the stellar angular distance measurement sensor and the pulse arrival time difference observations provided by the X-ray detector. The spacecraft position estimation error curve, spacecraft velocity estimation error curve, earth position estimation error curve, earth velocity estimation error curve, and sensor system error parameter estimation error curve obtained by the method of the present invention are respectively as follows: Figure 2 , Figure 3 , Figure 4 , Figure 5 and Figure 6 As shown. The solid line in the figure represents the state estimation error curve, and the dotted line represents the 3σ error bound calculated based on the corresponding diagonal element of the extended Kalman filter estimation error variance matrix. Mathematical simulation examples show that the use of the method of the present invention for autonomous navigation of earth orbit spacecraft can effectively suppress the adverse effects of earth ephemeris errors and sensor system errors, and achieve a positioning accuracy level of hundreds of meters when the angular measurement accuracy of the star angular distance measurement sensor reaches the mas level.

[0112] The main technical content of the present invention can open up a new way to improve the performance of relativistic navigation systems for spacecraft, can meet the technical requirements of "high precision, long time, and autonomy", and has application value in future Earth orbit communications, navigation, remote sensing satellites, Earth-Moon space cruise vehicles, and deep space probes.

[0113] The contents not described in detail in the specification of the present invention belong to the prior art known to the professional and technical personnel in this field.

Claims

1. A relativistic navigation reference deviation calibration method based on the fusion of star and pulsar information, characterized in that The following steps are involved: S1 uses the extended Kalman filter as the navigation filter and initializes it, setting the initial value of the state vector representing the position and velocity of the Earth orbit spacecraft relative to the center of the Earth, the position and velocity of the center of the Earth relative to the center of mass of the solar system, and the error parameters of the sensor system; S2 predicts the position and velocity of the spacecraft relative to the center of the Earth based on the orbital dynamics model of the Earth-orbiting spacecraft and obtains the corresponding predicted values. It predicts the position and velocity of the center of the Earth relative to the center of mass of the solar system based on the orbital dynamics model of the Earth and obtains the corresponding predicted values. S3 observes stars through the star angular distance measurement sensor configured on the earth orbit spacecraft to obtain the star angular distance observation value; S4, when the stellar angular distance observation value is available, the stellar angular distance observation value obtained in step S3 is substituted into the extended Kalman filter for calculation, and the predicted values ​​of the position and velocity of the spacecraft relative to the center of the earth, the predicted values ​​of the position and velocity of the center of the earth relative to the center of mass of the solar system, and the sensor system error parameters obtained in step S2 are corrected; S5 observes pulsars through X-ray detectors installed on earth-orbiting spacecraft to obtain the observed time difference of pulse arrival of pulsars; S6, when the pulse arrival time difference observation is available, substitute the pulse arrival time difference observation obtained in step S5 into the extended Kalman filter for calculation, and correct the predicted values ​​of the position and velocity of the spacecraft relative to the center of the earth, the predicted values ​​of the position and velocity of the center of the earth relative to the center of mass of the solar system, and the sensor system error parameters obtained in step S2; S7 returns to step S2 for iteration, and stops iteration when the statistical value of the filtered new information is less than a given threshold, to obtain the estimated values ​​of the position and velocity of the spacecraft relative to the center of the earth, the estimated values ​​of the position and velocity of the center of the earth relative to the center of mass of the solar system, and the estimated values ​​of the error parameters of the sensor system, thereby completing the calibration of the relativistic navigation reference deviation of the fusion of stellar and pulsar information.

2. The relativistic navigation reference deviation calibration method of the stellar and pulsar information fusion according to claim 1 is characterized by: The method for initializing the extended Kalman filter as the navigation filter in step S1 is: setting the state vector estimate of the extended Kalman filter at the initial time k = 0 for: in, and They represent the estimated values ​​of the position vector and velocity vector of the Earth orbit spacecraft relative to the center of the Earth at the initial moment, and They represent the estimated values ​​of the position vector and velocity vector of the Earth’s center relative to the solar system’s mass center at the initial moment, represents the estimated value of the sensor system error parameter at the initial moment, It is obtained based on a priori knowledge of the position and velocity of the Earth-orbiting spacecraft, the position and velocity of the Earth's center relative to the center of mass of the solar system, and the system error parameters of the star angular distance measurement sensor.

3. The method for calibrating the relativistic navigation reference deviation by fusing star and pulsar information according to claim 1, characterized in that: In step S2, the method for predicting the position and velocity of the spacecraft relative to the center of the earth, and the position and velocity of the center of the earth relative to the center of mass of the solar system is as follows: the state vector prediction value of the extended Kalman filter at time k Calculated according to the following formula: State transfer function The form is: Where τ represents the time step of one-step prediction in the extended Kalman filter, and the subscript k represents different moments. Represents the state vector estimate of the extended Kalman filter at time k-1; nonlinear function The form is: in, represents the estimated value of the velocity vector of the Earth orbit spacecraft relative to the center of the Earth at time k-1, represents the estimated value of the position vector of the Earth orbit spacecraft relative to the center of the Earth at time k-1, represents the estimated value of the velocity vector of the Earth relative to the center of mass of the solar system at time k-1, represents the estimated value of the position vector of the Earth's center relative to the center of mass of the solar system at time k-1, μ E represents the Earth's gravitational constant, represents the known spacecraft orbit perturbation function, which is obtained according to the orbital dynamics model of the spacecraft, μ S is the solar gravitational constant, represents the known Earth orbit perturbation function, which is obtained based on the Earth's orbital dynamics model, and m represents the number of sensor system error parameters.

4. The method for calibrating the relativistic navigation reference deviation by integrating star and pulsar information according to claim 1, characterized in that: The observed angular distance of the star y in step S3 S,k The calculation method is: in, represents the observed angular distance of the i-th star at time k, i = 1, 2, ..., m, y S,k Obtained by observing stars using stellar angular distance measurement sensors installed on Earth-orbiting spacecraft.

5. The method for calibrating the relativistic navigation reference deviation by fusing star and pulsar information according to claim 1, characterized in that: In step S4, the method for correcting the predicted values ​​of the position and velocity of the spacecraft relative to the center of the earth, the predicted values ​​of the position and velocity of the center of the earth relative to the center of mass of the solar system, and the sensor system error parameters is as follows: in, represents the estimated value of the state vector of the extended Kalman filter at time k, represents the state vector prediction value of the extended Kalman filter at time k, y S,k represents the observed angular distance of the star, K S,k The Kalman gain matrix corresponding to the observed angular distance of the star is calculated based on the previously established relativistic navigation system model. The observation function The form is: in, represents the observed angular distance corresponding to the i-th star The observation function of is: Among them, u′ IAk and u′ IBk It represents the projection of the line-of-sight direction vector of a star measured by a stationary observer in an inertial coordinate system. It can be calculated based on a previously established star catalog. The subscripts A and B are used to distinguish different stars. c represents the speed of light. and Respectively Predicted values ​​of medium-Earth orbit spacecraft velocity, geocentric velocity, and sensor system error parameters.

6. The method for calibrating the relativistic navigation reference deviation by fusing star and pulsar information according to claim 1, characterized in that: The pulse arrival time difference observation value y in step S5 X,k for: in, represents the observed value of the arrival time difference of the jth pulse at time k, j = 1, 2, ..., n, y X,k The timing of pulsars is obtained by observing them with X-ray detectors installed on Earth-orbiting spacecraft and comparing them with a pre-established pulsar timing model.

7. The method for calibrating the relativistic navigation reference deviation by fusing star and pulsar information according to claim 1, characterized in that: In step S6, the method for correcting the predicted values ​​of the position and velocity of the spacecraft relative to the center of the earth, the predicted values ​​of the position and velocity of the center of the earth relative to the center of mass of the solar system, and the sensor system error parameters is as follows: in, represents the state vector prediction value of the extended Kalman filter at time k, K X,k represents the Kalman gain matrix corresponding to the pulse arrival time difference observation, which is calculated according to the previously established pulsar navigation system model, y X,k represents the pulse arrival time difference observation, the observation function The form is: in, represents the observed angular distance corresponding to the jth star The observation function of is: Among them, n (j) represents the line-of-sight direction vector of the j-th pulsar, represents the distance from the center of mass of the solar system to the jth pulsar, which can be calculated based on the previously established pulsar catalog. b represents the position vector of the center of mass of the solar system relative to the center of the sun, which can be calculated based on the previously established solar ephemeris. and Respectively Predicted values ​​of the medium earth orbit spacecraft position and the center of the earth, μ s represents the solar gravitational constant.

8. The method for calibrating the relativistic navigation reference deviation by fusing star and pulsar information according to claim 1, characterized in that: The recursive calculation method of the statistical value of the filtered new information in step S7 is: Among them, S k represents the statistical value of the new filtered information at time k, S k-1 represents the statistical value of the filtering innovation at time k-1. The initial value S0 of the statistical value of the filtering innovation is set to a normal number greater than the specified threshold. l represents the total number of sampled data in the pre-specified time window. Represents the filtering innovation, which is calculated as follows: The method for judging whether the statistical value of the filtered innovation is less than a given threshold is: Then it is judged that the statistical value of the filtered new information is less than the given threshold, where, For a given threshold, it can be set in advance according to the accuracy index of the star angular distance measurement sensor.

9. A relativistic navigation reference deviation calibration system integrating star and pulsar information, characterized in that: include: State initialization module: Initializes the extended Kalman filter used as a navigation filter, sets the initial value of the state vector representing the position and velocity of the Earth orbit spacecraft relative to the center of the Earth, the position and velocity of the center of the Earth relative to the center of mass of the solar system, and the error parameters of the sensor system; State prediction module: Based on the orbital dynamics model of the Earth-orbiting spacecraft, the position and velocity of the spacecraft relative to the center of the Earth are predicted; based on the orbital dynamics model of the Earth, the position and velocity of the center of the Earth relative to the center of mass of the solar system are predicted; Stellar observation module: observe stars on the celestial sphere through the star angular distance measurement sensor configured on the earth orbit spacecraft, and use the multi-aperture optical system on the star angular distance measurement sensor to observe multiple stars and obtain the angle of the star line of sight direction vector, that is, the star angular distance observation value; Correction module based on star observation: When the star angular distance observations of the star angular distance measurement sensor are available, the star angular distance observations are processed by the extended Kalman filter to correct the predicted values ​​of the spacecraft's position and velocity relative to the center of the earth, the predicted values ​​of the position and velocity of the center of the earth relative to the center of mass of the solar system, and the sensor system error parameters; Pulsar observation module: observe pulsars through X-ray detectors configured on earth-orbiting spacecraft, and use the multi-aperture optical system on the X-ray detector to observe multiple pulsars, and obtain the difference between the time when the pulse signal emitted by the pulsar arrives at the center of mass of the solar system and the time when it arrives at the spacecraft, that is, the pulse arrival time difference observation; Correction module based on pulsar observations: When the pulse arrival time difference observations of the X-ray detector are available, the pulse arrival time difference observations are processed by the extended Kalman filter to correct the predicted values ​​of the spacecraft position and velocity relative to the center of the earth, the predicted values ​​of the position and velocity of the center of the earth relative to the center of mass of the solar system, and the sensor system error parameters.

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