A method for using a magnetometer in a strong magnetic environment

Abstract

The present invention discloses a method for using a magnetometer in a strong magnetic environment, which includes the following steps: Step 1, preprocessing of the magnetometer and validity judgment; Step 2, calculating the magnetic field intensity of the aircraft body relative to the inertial system according to the magnetic field model; Step 3, selecting the magnetic field reference; Step 4, determining the usage strategy according to the selection situation of the magnetic field reference. This method is based on reserving an interface for deducting the strong magnetic constant value from the magnetometer measurement value and the time-division and staggered control of the magnetometer and the magnetic torquer, which can avoid the problem that the magnetic field measurement value of the magnetometer is affected by the surrounding strong magnetic environment and its access to the closed-loop use, and can more reliably introduce the geomagnetic field value into the closed-loop control for use. The design of this method for using the magnetometer is simple and easy to be applied in engineering.

Description

Technical Field

[0001] The present invention relates to the field of aircraft control, and particularly to a method for using a magnetometer in a strong magnetic environment, which is applicable to the effective attitude control of introducing a magnetic field into a closed loop. Background Art

[0002] Existing methods for using magnetometers do not consider the influence of other interferences. Even if the influence is considered, at the initial stage of design, the interference source is separated by a spatial distance to reduce the influence. However, in actual applications, due to limited installation space on the aircraft or inevitable strong magnetic interference generated during the operation of other single units, it is impossible to ensure that the real-time measurement information of the magnetometer is not affected. In order to ensure as accurately as possible the magnetic field value introduced into the closed loop, certain technical means need to be taken to ensure this. Summary of the Invention

[0003] Aiming at the deficiencies existing in the prior art, the technical problem solved by the present invention is to provide a method for using a magnetometer in a strong magnetic environment, which can more real-time and reliably introduce the geomagnetic field value into the closed loop. This method for using a magnetometer is simple, can avoid the problem that the magnetic field measurement value of the magnetometer is affected by the surrounding strong magnetic environment, and is easy to be applied in engineering.

[0004] To achieve the above object, the present invention provides a method for using a magnetometer in a strong magnetic environment. The magnetometer is installed on an aircraft and used, and the method includes the following steps:

[0005] Step 1, preprocessing and validity judgment of the magnetometer:

[0006] - Calculate the magnetic field intensity in this system according to the measurement value of the magnetometer;

[0007] - Judge whether the magnetometer is valid;

[0008] Step 2, calculate the magnetic field intensity of the aircraft body relative to the inertial system according to the magnetic field model:

[0009] - Calculate the geomagnetic field intensity by using the Gauss model;

[0010] - Calculate the magnetic field intensity in this system;

[0011] Step 3, select the magnetic field reference:

[0012] - Judge the magnetic field reference selection method;

[0013] - Determine the magnetic field reference according to the current magnetic field reference selection method;

[0014] Step 4, determine the usage strategy according to the magnetic field reference selection situation:

[0015] - Select the corresponding usage strategy when the magnetic field reference is the magnetic field model;

[0016] - Select the corresponding usage strategy for the magnetometer based on the magnetic field reference.

[0017] Further, the said step 1 includes the following content:

[0018] Step 1.1, calculate the magnetic field intensity in this system according to the magnetometer measurement value:

[0019] When the magnetometer acquisition is effective, convert the original magnetometer measurement data to the body coordinate system:

[0020] Bb_MM = A b←s ×Bs_MM - Δb

[0021] Where, A b←s is the rotation matrix from the magnetometer measurement system to this system; Δb is the zero position of the magnetometer, and Bb_MM and Bs_MM are the body coordinate system data and the original data respectively;

[0022] Step 1.2, judge whether the magnetometer is effective:

[0023] After deducting the strong magnetic interference by merging into the magnetometer zero position Δb, if it is judged that the absolute value of any axis magnetometer exceeds 0.8 Gs, set the magnetometer invalid flag, otherwise, if the modulus value of the magnetometer measurement data is greater than 0.1 Gs and the absolute value of the magnetometer measurement data of any axis does not exceed 0.8 Gs, set the magnetometer effective flag.

[0024] Further, the said step 2 includes the following content:

[0025] Step 2.1, calculate the geomagnetic field intensity Bp using the Gauss model;

[0026]

[0027] Where, Re is the radius of the earth; r is the distance from the aircraft to the earth's center; θ is the co-latitude of the earth's center; λ is the geographical longitude;

[0028] Step 2.2, calculate the magnetic field intensity Bb_mdl in this system and limit it to [-1, 1] Gs:

[0029] B b_mdl = C bi ×C ip ×B P

[0030] Where,

[0031] a is the right ascension of the position where the aircraft is located; φ is the declination of the position where the aircraft is located; Cbi is the conversion matrix from the inertial system to this system;

[0032] Further, step 3 includes the following steps:

[0033] Step 3.1, determine the magnetic field reference selection method:

[0034] The magnetic field reference selection is divided into two methods: ground forced selection and aircraft autonomous selection. Ground injection is given priority. If the ground does not inject and specify the magnetic field reference, the aircraft makes an autonomous selection;

[0035] Step 3.2, determine the magnetic field reference according to the current magnetic field reference selection method:

[0036] If the ground injects and forces the selection of the magnetic field reference, it shall be subject to the ground forced selection; if the ground forces the selection of the magnetometer as the reference, the magnetic field reference is the magnetometer; if the ground forces the selection of the magnetic field model as the reference, the magnetic field reference is the magnetic field model.

[0037] If the magnetic field reference adopts the autonomous selection method, it is as follows: if the injection allows the judgment of platform abnormality, and the platform is abnormal and the magnetometer is effective, the magnetic field reference is the magnetometer; otherwise, if the previous cycle was the magnetometer and the magnetometer is effective, the magnetic field reference is the magnetometer; otherwise, the magnetic field reference is the magnetic field model.

[0038] As described in claim 1, a method for using a magnetometer in a strong magnetic environment, characterized in that step 4 includes the following steps:

[0039] Step 4.1, when the magnetic field reference is the magnetic field model, there is no need to use it with wrong beats; the magnetic field intensity of this system is calculated in real time according to the Gauss model for each cycle, and closed-loop control is introduced when the attitude control mode is not jet control;

[0040] Step 4.2, when the magnetic field reference is the magnetometer, the magnetometer and the magnetic torquer are controlled separately. The magnetometer continuously measures for three cycles, and after preprocessing, the magnetic field intensity of this system is obtained. The effective value of the magnetic field intensity of this system for these three cycles is averaged to obtain an average value of the magnetic field intensity of this system. Closed-loop control for the next few cycles is introduced when the attitude control mode is not jet control, and the magnetic control command current is calculated in real time. The magnetic control command current is sent to the magnetic torquer for continuous control for six cycles, and then the magnetic torquer stops controlling for one cycle, and then repeats the measurement and control according to the above timing requirements

[0041] In summary, compared with the prior art, the method for using a magnetometer in a strong magnetic environment provided by the present invention has the following advantages and beneficial effects:

[0042] 1. It can deduct the strong magnetic constant interference existing on the aircraft and avoid the influence of the constant deviation of the measurement value of the magnetometer introduced into the closed loop;

[0043] 2. The magnetometer and magnetic torquer are controlled by time-sharing staggered beats. The time-sharing staggered beats can be flexibly selected to avoid the influence of the close-range magnetic torquer operation on the magnetometer measurement value introduced into the closed loop;

[0044] 3. It is suitable for controlling various aircraft with limited layouts and has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a flow chart of the method for using the magnetometer in a strong magnetic environment of the present invention;

[0046] Figure 2 It is a schematic diagram of the time-sharing staggered timing design of the magnetometer and magnetic torquer of the present invention. DETAILED DESCRIPTION

[0047] The following is a further detailed description of a method for using a magnetometer in a strong magnetic environment proposed by the present invention in combination with the accompanying drawings and specific embodiments. According to the following description, the advantages and features of the present invention will be clearer. It should be noted that the accompanying drawings are in a very simplified form and use non-precise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. In order to make the purposes, features and advantages of the present invention more obvious and easy to understand, please refer to the accompanying drawings. It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no technical substantive significance. Any structural modification, change in proportional relationship or adjustment of size, without affecting the effects that the present invention can produce and the purposes that can be achieved, should still fall within the scope of the technical content disclosed by the present invention.

[0048] like Figure 1 As shown, a method for using a magnetometer in a strong magnetic environment provided by the present invention is provided. The magnetometer is installed in an aircraft for use. The method comprises the following steps:

[0049] Step 1: Magnetometer preprocessing and validity judgment:

[0050] -Calculate the magnetic field strength in this system based on the magnetometer measurement value;

[0051] -Determine whether the magnetometer is valid;

[0052] Step 2: Calculate the magnetic field strength of the aircraft body relative to the inertial system based on the magnetic field model:

[0053] - Use Gauss model to calculate the geomagnetic field strength;

[0054] -Calculate the magnetic field strength of this system;

[0055] Step 3: Select the magnetic field reference:

[0056] - Determine the magnetic field reference selection method;

[0057] - Determine the magnetic field reference according to the current magnetic field reference selection method;

[0058] Step 4. Determine the usage strategy according to the magnetic field reference selection situation:

[0059] - Select the corresponding usage strategy when the magnetic field reference is the magnetic field model;

[0060] - Select the corresponding usage strategy when the magnetic field reference is the magnetometer.

[0061] Specifically, the said Step 1 includes the following contents:

[0062] Step 1.1. Calculate the magnetic field intensity in this system according to the magnetometer measurement value:

[0063] When the magnetometer acquisition is effective, convert the original magnetometer measurement data to the body coordinate system:

[0064] Bb_MM = A b←s ×Bs_MM - Δb

[0065] where A b←s is the rotation matrix from the magnetometer measurement system to this system; Δb is the magnetometer zero position, and Bb_MM and Bs_MM are the body coordinate system data and the original data respectively;

[0066] Step 1.2. Judge whether the magnetometer is effective:

[0067] After deducting the strong magnetic interference by merging into the magnetometer zero position Δb, if it is judged that the absolute value of any axis magnetometer exceeds 0.8 Gs, set the magnetometer invalid flag; otherwise, if the modulus value of the magnetometer measurement data is greater than 0.1 Gs and the absolute value of the magnetometer measurement data of any axis does not exceed 0.8 Gs, set the magnetometer effective flag.

[0068] The said Step 2 includes the following contents:

[0069] Step 2.1. Calculate the geomagnetic field intensity Bp using the Gauss model:

[0070]

[0071] where Re is the radius of the earth; r is the distance from the aircraft to the earth's center; θ is the co-latitude of the earth's center; λ is the geographical longitude;

[0072] Step 2.2. Calculate the magnetic field intensity in this system:

[0073] Calculate the magnetic field intensity Bb_mdl in this system and limit it to [-1, 1] Gs:

[0074] Bb_mdl = C bi × C ip × B P

[0075] Wherein,

[0076] a is the right ascension of the position where the aircraft is located; φ is the declination of the position where the aircraft is located; Cbi is the conversion matrix from the inertial system to the body system;

[0077] Further, step 3 includes the following steps:

[0078] Step 3.1, determine the magnetic field reference selection method:

[0079] The magnetic field reference selection is divided into two methods: ground forced selection and aircraft autonomous selection. Ground injection is given priority. If the ground does not inject and specify the magnetic field reference, the aircraft makes an autonomous selection;

[0080] Step 3.2, determine the magnetic field reference according to the current magnetic field reference selection method:

[0081] If the ground injects and forces the selection of the magnetic field reference, it shall be subject to the ground forced selection; if the ground forces the selection of the magnetometer as the reference, the magnetic field reference is the magnetometer; if the ground forces the selection of the magnetic field model as the reference, the magnetic field reference is the magnetic field model.

[0082] If the magnetic field reference adopts the autonomous selection method, specifically as follows: if the injection allows the judgment of platform abnormality, and the platform is abnormal and the magnetometer is effective, the magnetic field reference is the magnetometer; otherwise, if the previous cycle was the magnetometer and the magnetometer is effective, the magnetic field reference is the magnetometer; otherwise, the magnetic field reference is the magnetic field model. Generally, after the aircraft enters orbit, the magnetic field model is preferably selected by default.

[0083] Further, in step 4, when the magnetic field reference is the magnetic field model or the magnetometer, the corresponding usage strategies are selected, including the following steps:

[0084] Step 4.1, when the magnetic field reference is the magnetic field model, there is no need to use it with misaligned beats; the magnetic field intensity of the body system is calculated in real time according to the Gauss model every cycle, and closed-loop control is introduced when the attitude control mode is not jet control;

[0085] Step 4.2, when the magnetic field reference is the magnetometer, the magnetometer and the magnetic torquer are controlled separately, such as Figure 2As shown, the magnetometer continuously measures for three cycles. After preprocessing, the magnetic field strength of this system is obtained. The effective values of the magnetic field strength of this system in these three cycles are averaged to obtain an average value of the magnetic field strength of this system. When the attitude control mode is not jet control, closed-loop control for the next few cycles is introduced, and the magnetic control command current is calculated in real time. The magnetic control command current is sent to the magnetic torque actuator in real time to continuously control for six cycles. Then, the magnetic torque actuator stops controlling for one cycle, and the measurement and control are repeated according to the above timing requirements.

[0086] The present invention provides a method for using a magnetometer. This method is based on reserving an interface for deducting strong magnetic constant values from the magnetometer measurement values and time-sharing and staggered control of the magnetometer and the magnetic torque actuator, which can avoid the problem that the magnetic field measurement value of the magnetometer is affected by the surrounding strong magnetic environment and its access to closed-loop use, and can more reliably introduce the geomagnetic field value into closed-loop control for use. The method for using this magnetometer is simply designed and easy to apply in engineering.

[0087] Although the content of the present invention has been introduced in detail through the above preferred embodiments, it should be recognized that the above description should not be considered as a limitation of the present invention. After those skilled in the art have read the above content, various modifications and substitutions to the present invention will be obvious. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims

1. A method for using a magnetometer in a strong magnetic environment, where the magnetometer is installed on an aircraft for use, Characterized in that, It includes the following steps: Step 1, Magnetometer preprocessing and validity judgment: - Calculate the magnetic field strength of this system according to the magnetometer measurement value; - Judge whether the magnetometer is valid; Step 2, Calculate the magnetic field strength of the aircraft body relative to the inertial system according to the magnetic field model: - Use the Gauss model to calculate the geomagnetic field strength; - Calculate the magnetic field strength of this system; Step 3, Select the magnetic field reference: - Judge the magnetic field reference selection method; - The magnetic field reference selection is divided into two methods: ground forced selection and aircraft autonomous selection; ground injection is specified as the priority. If the ground does not specify the magnetic field reference, the aircraft makes an autonomous selection; - Determine the magnetic field reference according to the current magnetic field reference selection method; - If the ground injects to force the selection of the magnetic field reference, take the ground forced selection as the standard: if the ground forces the selection of the magnetometer as the reference, the magnetic field reference is the magnetometer; if the ground forces the selection of the magnetic field model as the reference, the magnetic field reference is the magnetic field model; Step 4, Determine the usage strategy according to the magnetic field reference selection situation: - Select the corresponding usage strategy when the magnetic field reference is the magnetic field model; - Step 4.1, When the magnetic field reference is the magnetic field model, there is no need to use it with wrong beats; the magnetic field strength of this system is calculated in real time according to the Gauss model in each period, and closed-loop control is introduced when the attitude control mode is not jet control; - Select the corresponding usage strategy when the magnetic field reference is the magnetometer; - Step 4.2, When the magnetic field reference is the magnetometer, the magnetometer and the magnetic torquer are controlled separately. The magnetometer continuously measures for three periods, and after preprocessing, the magnetic field strength of this system is obtained. Take the effective value of the magnetic field strength of this system in these three periods and average it to obtain an average value of the magnetic field strength of this system. Closed-loop control is introduced in the next few periods when the attitude control mode is not jet control, and the magnetic control command current is calculated in real time. The magnetic control command current is sent to the magnetic torquer continuously for six periods of control, and then the magnetic torquer stops controlling for one period, and then the measurement and control are repeated.

2. A method for using a magnetometer in a strong magnetic environment as described in claim 1, Characterized in that, The said step 1 includes the following contents: Step 1.1, Calculate the magnetic field strength of this system according to the magnetometer measurement value: When the magnetometer collects valid data, convert the original magnetometer measurement data to the body coordinate system: Bb_MM = A b←s ×Bs_MM - Δb where A b←s is the rotation matrix from the magnetometer measurement system to this system; Δb is the magnetometer zero position Bb_MM and Bs_MM are the data in the body coordinate system and the original data respectively; Step 1.2, Judge whether the magnetometer is valid: After deducting the strong magnetic interference by merging into the magnetometer zero position Δb, if it is judged that the absolute value of any axis magnetometer exceeds 0.8 Gs, set the magnetometer invalid flag. Otherwise, if the modulus value of the magnetometer measurement data is greater than 0.1 Gs and the absolute value of the magnetometer measurement data of any axis does not exceed 0.8 Gs, set the magnetometer valid flag.

3. A method for using a magnetometer in a strong magnetic environment as described in claim 1, Characterized in that, The said step 2 includes the following contents: Step 2.1, Use the Gauss model to calculate the geomagnetic field strength Bp; Where, Re is the radius of the earth; r is the distance from the aircraft to the center of the earth; θ is the co-latitude of the center of the earth; λ is the geographical longitude; Step 2.2, calculate the magnetic field strength Bb_mdl of this system and limit it to [-1, 1] Gs: B b_mdl = C bi × C ip × B P Among them, a is the right ascension of the position where the aircraft is located; φ is the declination of the position where the aircraft is located; Cbi is the transformation matrix from the inertial system to this system.

4. A method for using a magnetometer in a strong magnetic environment as described in claim 1, characterized in that the said step 3 includes the following steps: If the magnetic field reference adopts the autonomous selection method, specifically as follows: If the number of notes allows judging platform abnormality, and the platform is abnormal and the magnetometer is effective, then the magnetic field reference is the magnetometer; otherwise, if the previous cycle is the magnetometer and the magnetometer is effective, then the magnetic field reference is the magnetometer; otherwise the magnetic field reference is the magnetic field model.

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