CN109703787A - A kind of method for diagnosing faults of near-earth satellite three axis magnetometer data validity - Google Patents
A kind of method for diagnosing faults of near-earth satellite three axis magnetometer data validity Download PDFInfo
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- CN109703787A CN109703787A CN201811512670.6A CN201811512670A CN109703787A CN 109703787 A CN109703787 A CN 109703787A CN 201811512670 A CN201811512670 A CN 201811512670A CN 109703787 A CN109703787 A CN 109703787A
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Abstract
A kind of method for diagnosing faults of near-earth satellite three axis magnetometer data validity, within a preset time, if the geomagnetic field intensity measured value and geomagnetic field intensity theoretical value that the output data of three axis magnetometer is unchanged or three axis magnetometer obtains are inconsistent, judge that three axis magnetometer breaks down.Fault diagnosis flow scheme of the present invention is simple and easy, the threshold value of all settings may be configured as it is in-orbit correct, effectively the output data of three axis magnetometer can be diagnosed, avoid mistake geomagnetic field intensity substitute into satellite control system.
Description
Technical Field
The invention relates to a fault diagnosis method for data validity of a three-axis magnetometer of a near-earth satellite.
Background
The earth magnetic field is distributed in a large range above the earth, the near-earth satellite is greatly influenced by the earth magnetic field, and magnetic moment generated by the earth magnetic field to the satellite can be interference moment for controlling the satellite attitude and can also be utilized as control moment for stabilizing the satellite attitude to determine that the magnetic moment needs to know the strength and the direction of the magnetic field; in addition, the geomagnetic field can be used as a reference field for satellite attitude measurement, and the geomagnetic vector is used as a reference vector. A magnetometer, an instrument capable of measuring the local magnetic field vector, is typically mounted on the satellite constellation.
The three-axis magnetometer is used as a geomagnetic sensitive measurement component of a satellite attitude and orbit control system, is used for measuring the intensity vector of the earth magnetic field so as to ensure that the magnetic torquer generates correct control moment, and is also used for measuring the satellite attitude by directly using the local magnetic field as a measurement reference field. The introduction of wrong geomagnetic field strength into the control system, which cannot generate the required control torque, may cause deviation of the control or divergence of the attitude, and thus it is necessary to ensure the correctness of the measurement data of the magnetometer through fault diagnosis.
Disclosure of Invention
The invention provides a fault diagnosis method for data effectiveness of a three-axis magnetometer of a near-earth satellite, which has simple and feasible fault diagnosis process, can set all set thresholds to be in-orbit correctable, can effectively diagnose output data of the three-axis magnetometer, and avoids substituting wrong geomagnetic field intensity into a satellite control system.
In order to achieve the above object, the present invention provides a fault diagnosis method for data validity of a three-axis magnetometer of a near-earth satellite, comprising the following steps: and in the preset time, if the output data of the three-axis magnetometer is unchanged or the geomagnetic field intensity measured value obtained by the three-axis magnetometer is inconsistent with the geomagnetic field intensity theoretical value, judging that the three-axis magnetometer fails.
The preset time comprises 10 continuous beats.
And judging whether the output data of the three-axis magnetometer changes or not in each beat, and judging whether the geomagnetic field intensity measured value obtained by the three-axis magnetometer is consistent with the geomagnetic field intensity theoretical value or not.
And if the variation of the geomagnetic field intensity data output by the three-axis magnetometer is smaller than the set threshold, determining that the geomagnetic field intensity data output by the three-axis magnetometer is unchanged.
And if the difference value between the triaxial component of the geomagnetic field strength theoretical value and the triaxial component of the geomagnetic field strength measurement value is greater than a set threshold value, determining that the geomagnetic field strength measurement value is inconsistent with the geomagnetic field strength theoretical value.
The method for calculating the theoretical value of the geomagnetic field intensity comprises the following steps: and (4) solving the gradients of the magnetic potential in the north, east and down directions according to the geomagnetic field intensity model to obtain the triaxial components of the geomagnetic field intensity theoretical value.
The method of calculating the earth's magnetic field strength measurement comprises: and subtracting the known residual magnetism on the satellite from the measurement value of the three-axis magnetometer to obtain the geomagnetic field intensity measurement value.
And after the failure of the triaxial magnetometer is judged, the theoretical value of the geomagnetic field intensity is used to access the satellite control system.
The fault diagnosis process is simple and easy to implement, all set thresholds can be set to be in-orbit correctable, the output data of the three-axis magnetometer can be effectively diagnosed, and the wrong geomagnetic field intensity is prevented from being substituted into a satellite control system.
Drawings
Fig. 1 is a flowchart of a fault diagnosis method for data validity of a three-axis magnetometer of a near-earth satellite according to the present invention.
Detailed Description
The preferred embodiment of the present invention is described in detail below with reference to fig. 1.
The low earth satellite runs on the orbit, the position of the point under the satellite is changed continuously, the geomagnetic field output by the triaxial magnetometer fixedly connected with the satellite body is also changed continuously, and if the output is not changed, the triaxial magnetometer is judged to be possibly out of order. Therefore, whether the three-axis magnetometer has a fault can be diagnosed by judging whether the data output by the three-axis magnetometer is kept unchanged for a period of time.
The earth magnetic field is derived from the current system of the earth internal structure and the earth vicinity, wherein the basic magnetic field derived from the earth internal structure is a main part (more than 99 percent), and the magnetic potential of the main part can be expressed by a spherical harmonic function and is a function of the earth center distance, the earth center latitude and the geographic longitude (Greenwich mean east longitude). And solving the gradients of the magnetic potential in the north, east and down directions to obtain the components of the geomagnetic field in three directions as the theoretical values of the geomagnetic field strength. Generally, the geomagnetic field intensity data measured by the three-axis magnetometer should be equal to the theoretical value of the geomagnetic field intensity, and if the difference between the geomagnetic field intensity data measured by the three-axis magnetometer and the theoretical value of the geomagnetic field intensity is large, the fault of the three-axis magnetometer can be diagnosed.
As shown in fig. 1, the present invention provides a method for diagnosing data validity failure of a three-axis magnetometer of a near-earth satellite, comprising the following steps:
step S1, judging whether the geomagnetic field intensity data output by the triaxial magnetometer in one beat is unchanged, if not, performing step S6, and if so, performing step S2;
setting a threshold value (0.1Gs), and if the variation of the geomagnetic field intensity data output by the three-axis magnetometer in one beat is smaller than the threshold value, determining that the geomagnetic field intensity data output by the three-axis magnetometer is unchanged;
step S2, calculating theoretical value R of triaxial component of geomagnetic field intensity in satellite body coordinate system according to geomagnetic field intensity model in one beat with step S1bx0、Rby0、Rbz0；
Step S3, calculating the measured value R of the triaxial component of the geomagnetic field intensity in the satellite body coordinate system output by the triaxial magnetometer in the same beat as the step S2bx、Rby、Rbz；
Step S4, calculating the difference between the theoretical value and the measured value of the triaxial component of the magnetic field strength in the same beat;
step S5, judging whether the difference value between the theoretical value and the measured value of the three-axis component of the geomagnetic field intensity is larger than a threshold value (0.1Gs), if so, performing step S6, and if not, performing step S8;
step S6, determining whether the total number of beats reaches a set threshold (10 beats in this embodiment), if yes, performing step S7, and if no, performing step S1;
s7, judging that the triaxial magnetometer fails, accessing the satellite control system by using the theoretical value of the geomagnetic field intensity, and performing S1;
and step S8, the geomagnetic field intensity measured by the three-axis magnetometer is still kept to be connected to the satellite control system, and step S1 is carried out.
For a low-earth satellite, the intensity of the earth magnetic field corresponding to the low-earth satellite in the three-axis stable attitude along with the change of the satellite orbit position is a continuously changing vector, and the main part of the basic magnetic field can be obtained through an approximate model and can be used as the basis for fault diagnosis of the validity of the output data of the three-axis magnetometer.
The method for calculating the theoretical value of the geomagnetic field intensity comprises the following steps of:
the magnetic potential expression of the basic magnetic field is as follows:
in the formula, ReIs the radius of the earth, r is the geocentric distance of the near-earth satellite, theta is the geocentric latitude, lambda is the east longitude from Greenwich mean,is the gaussian coefficient of the basic magnetic field,is an m-order associative legendre function of degree n;
selecting a geomagnetic field intensity model according to needs, wherein a common simplified model is a tilted dipole model with n being 1 and m being 1;
and (3) solving the gradients of the magnetic potential in the north direction, the east direction and the downward direction under the north-east-earth coordinate system of the earth to obtain the triaxial components of the satellite geographical geomagnetic field strength theoretical value:
converting the three-axis component of the geomagnetic field intensity under the north-east-earth coordinate system of the earth into the satellite body coordinate system:
in the formula:
wherein a is the included angle between the flight direction of the satellite and the north-pointing radial line, u is the orbit argument, delta is the earth center dimension, CboA transformation matrix from an orbit coordinate system to a satellite body coordinate system;
wherein,roll, pitch and yaw angles, respectively, of the satellite body system are described in terms of 1-2-3 degrees of rotation euler angles relative to the orbital coordinate system.
The method for calculating the measured value of the geomagnetic field intensity comprises the following steps:
the magnetometer measures the geomagnetic field intensity under a satellite body coordinate system and comprises an earth magnetic field and an on-satellite residual magnetismThe residual magnetism on the satellite, which is obtained by ground measurement before satellite transmission, is known and is set asNeglecting measurement errors, hence magnetometer measurementsDeducting residual magnetism on the star to obtain the intensity of the geomagnetic fieldNamely:
when the three-axis magnetometer is installed, the measurement coordinate system of the three-axis magnetometer can be kept consistent with the satellite body system;
calculating the three-axis component of the geomagnetic field strength measurement value as the output value R of the three-axis magnetometerbxc、Rbyc、Rbzc：
Rbx＝Rbxc，Rby＝Rbyc，Rbz＝Rbzc
If the difference value between the theoretical value of the three-axis component of the geomagnetic field intensity and the measured value is small, the output data of the three-axis magnetometer is judged to be reasonable and effective and can be used for control.
The fault diagnosis process is simple and easy to implement, all set thresholds can be set to be in-orbit correctable, the output data of the three-axis magnetometer can be effectively diagnosed, and the wrong geomagnetic field intensity is prevented from being substituted into a satellite control system.
While the present invention has been described in detail with reference to the preferred embodiments, it should be understood that the above description should not be taken as limiting the invention. Various modifications and alterations to this invention will become apparent to those skilled in the art upon reading the foregoing description. Accordingly, the scope of the invention should be determined from the following claims.
Claims (8)
1. A fault diagnosis method for data validity of a three-axis magnetometer of a near-earth satellite is characterized by comprising the following steps: and in the preset time, if the output data of the three-axis magnetometer is unchanged or the geomagnetic field intensity measured value obtained by the three-axis magnetometer is inconsistent with the geomagnetic field intensity theoretical value, judging that the three-axis magnetometer fails.
2. The method of claim 1, wherein the predetermined time comprises 10 continuous beats.
3. The method for diagnosing the failure of the data validity of the three-axis magnetometer of the near-earth satellite according to claim 2, wherein it is determined whether the output data of the three-axis magnetometer is changed or not in each beat, and it is determined whether the measured value of the geomagnetic field intensity obtained by the three-axis magnetometer is consistent with the theoretical value of the geomagnetic field intensity.
4. The method of claim 3, wherein the geomagnetic field intensity data output by the three-axis magnetometer is considered to be unchanged if the variation of the geomagnetic field intensity data output by the three-axis magnetometer is smaller than a set threshold.
5. The method of claim 4, wherein the geomagnetic field strength measurement value is considered inconsistent with the geomagnetic field strength theoretical value if a difference between the triaxial component of the geomagnetic field strength theoretical value and the triaxial component of the geomagnetic field strength measurement value is greater than a set threshold value.
6. The method for fault diagnosis of data validity of the three-axis magnetometer of the near-earth satellite according to claim 5, wherein the method for calculating the theoretical value of the geomagnetic field intensity comprises: and (4) solving the gradients of the magnetic potential in the north, east and down directions according to the geomagnetic field intensity model to obtain the triaxial components of the geomagnetic field intensity theoretical value.
7. The method of fault diagnosis of data validity of a three-axis magnetometer of a near-earth satellite according to claim 6, wherein the method of calculating the geomagnetic field strength measurement comprises: and subtracting the known residual magnetism on the satellite from the measurement value of the three-axis magnetometer to obtain the geomagnetic field intensity measurement value.
8. The method of claim 7, wherein the theoretical value of geomagnetic field strength is used to access the satellite control system after the three-axis magnetometer is determined to be faulty.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116068477A (en) * | 2023-02-24 | 2023-05-05 | 中国科学院微小卫星创新研究院 | Satellite magnetometer self-validity judging method and device |
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| CN107422281A (en) * | 2017-04-28 | 2017-12-01 | 中国人民解放军国防科学技术大学 | Micro-nano satellite magnetic-field measurement deviation correction method and device |
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- 2018-12-11 CN CN201811512670.6A patent/CN109703787A/en active Pending
Patent Citations (6)
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| CN104090251A (en) * | 2014-07-25 | 2014-10-08 | 中国科学院空间科学与应用研究中心 | Device and method for measuring residual magnetism and induced magnetism of satellite in geomagnetic field |
| CN104090250A (en) * | 2014-07-25 | 2014-10-08 | 中国科学院空间科学与应用研究中心 | Device and method for measuring remanence and induced magnetism of satellite in magnetism-free space |
| CN105526947A (en) * | 2014-10-20 | 2016-04-27 | 霍尼韦尔国际公司 | Method of detecting attitude faults based on magnetometer measurements |
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| CN116068477A (en) * | 2023-02-24 | 2023-05-05 | 中国科学院微小卫星创新研究院 | Satellite magnetometer self-validity judging method and device |
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