Multi-source information fusion navigation method for landing process of reusable carrier rocket

Abstract

The invention relates to a multi-source information fusion navigation method in a landing process of a reusable carrier rocket, aiming at the characteristics that when the reusable carrier rocket is close to a target landing point, because the flight height is relatively low and various positioning single machines can be utilized, the method comprises the following steps of: firstly, utilizing rocket body speed and position information output by a differential receiver; the rocket body speed and position information solved by the strapdown inertial measurement combination is corrected, and landing navigation control of the carrier rocket is carried out by using a corrected result; and when the output of the differential receiver cannot be utilized, the measurement result of the radar altimeter is further utilized to correct the rocket body height information solved by the strapdown inertial measurement combination, and the corrected height information is utilized to carry out landing navigation control on the carrier rocket. The method can ensure that the rocket navigation system can always output high-precision and high-reliability position and speed information in the landing process.

Description

Technical Field

[0001] This invention belongs to the field of spacecraft control and relates to a high-precision navigation method for auxiliary control during the landing process of reusable launch vehicles. Background Technology

[0002] Reusable launch vehicles are a concept relative to "disposable launch vehicles." After launching from the ground and completing their intended mission, a reusable launch vehicle returns and lands at its target location. After maintenance, repairs, and refueling, it can be launched again. The advantage and ultimate goal of reusable launch vehicles is to reduce the number of rocket bodies and equipment discarded after a single use, thereby lowering launch costs through recovery and reuse. Reusability technology is considered an important means of reducing space transportation costs and an effective way to improve the rapid response capability of launch vehicles to space.

[0003] Launch vehicles are typically equipped with inertial navigation systems (INS), but during long-term strapdown calculations, the position and velocity of these INS systems tend to diverge. Traditional integrated navigation systems for launch vehicles generally use receiver point positioning to correct the INS strapdown calculation results, and the navigation accuracy is insufficient to meet the landing requirements of reusable rockets. Summary of the Invention The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide a multi-source information fusion navigation method for the landing process of a reusable launch vehicle. It relies on ground base station information for differential positioning, corrects velocity and position through combined navigation, and selects a radar altimeter to assist in the measurement of altitude in the case of short-term receiver failure. This effectively solves the problem of position and velocity divergence in the inertial navigation system during strapdown calculation, and ensures that the rocket navigation system can always output high-precision and high-reliability position and velocity information during the landing process.

[0004] The technical solution of this invention is: a multi-source information fusion navigation method for the landing process of a reusable launch vehicle, comprising: The velocity and position information of the rocket body at the current moment are obtained by using strapdown inertial measurement unit (SIM) combined calculation. Determine whether the current altitude of the rocket body meets the differential positioning conditions of the differential receiver. If it does, use the rocket body velocity and position information output by the differential receiver to correct the rocket body velocity and position information in the navigation coordinate system calculated by the strapdown inertial measurement unit, and use the corrected results to perform landing navigation control of the launch vehicle. If the conditions are not met, the system will further determine whether the current altitude of the rocket body meets the measurement conditions of the radar altimeter. If it does, the system will use the measurement results of the radar altimeter to correct the altitude information of the rocket body in the navigation coordinate system calculated by the strapdown inertial measurement unit, and use the corrected altitude information to perform landing navigation control of the launch vehicle. If the conditions are not met, the system will wait for the next moment and re-determine the differential positioning conditions. The navigation coordinate system is the landing point coordinate system, with the origin at... At the theoretical landing point, The axis points in the direction of the line connecting the launch point and the sphere of the landing point within the horizontal plane of the landing point. The axis is perpendicular to the horizontal plane at the landing point and pointing upwards. The axis forms a right-handed system.

[0005] Furthermore, the determination of whether the current height of the rocket body meets the differential positioning conditions of the differential receiver specifically involves: if Then the condition is satisfied, where The current position of the rocket body in the navigation coordinate system, obtained from the inertial measurement unit's calculations, is its altitude position. This refers to the effective range of the receiver's differential positioning. It is a constant value, determined based on the effective range of the receiver's differential positioning data.

[0006] Furthermore, before correcting the velocity and position information of the rocket body in the navigation coordinate system calculated by the strapdown inertial measurement unit, the differential positioning status output of the differential receiver is checked for normality, including but not limited to normal receiver communication, normal PPS signal, differential positioning status, and the output position and velocity information satisfying the following relationship with the strapdown inertial measurement unit:

[0007] If all conditions are met, the differential positioning status output of the differential receiver is determined to be normal, where... , , , , , The velocity and position of the rocket body in the navigation coordinate system are converted from the receiver differential positioning data at the current sampling time n. , , , , , The velocity and position of the rocket body in the navigation coordinate system at the current sampling time n, obtained from the current strapdown inertial measurement unit calculation. The differential receiver position discrimination threshold is a constant value. A constant value is used for the speed discrimination threshold of the differential receiver. The aforementioned... and The performance specifications of the selected differential receiver and the accuracy specifications of the strapdown inertial measurement unit are determined based on the performance specifications of the selected receiver.

[0008] Furthermore, the method of correcting the velocity and position information of the rocket body in the navigation coordinate system calculated by the strapdown inertial measurement unit (SIM) using the velocity and position information output by the differential receiver specifically involves: applying Kalman filtering based on the calculation results of the SIM and the output of the differential receiver, wherein the observed values... for:

[0009] in , , , , , The differential receiver output of the current second pulse is converted to the velocity and position in the navigation coordinate system; , , , , , The velocity and position in the navigation coordinate system are calculated using the current second pulse strapdown inertial measurement unit. After performing a single integrated navigation filter using Kalman filtering, the state variables are obtained. The position and velocity errors in these state variables are then used to correct the solution results of the strapdown inertial measurement system.

[0010] in The position and velocity errors are in the filtered state variables.

[0011] Furthermore, the determination of whether the current altitude of the rocket body meets the measurement conditions of the radar altimeter specifically involves: if and Then the condition is satisfied, where, and These are the position and velocity information of the rocket body in the current navigation coordinate system, obtained from the strapdown inertial measurement unit (SIM) calculations. For the radar altimeter measurement range, This is the maximum velocity of the rocket body that the radar altimeter can track.

[0012] Furthermore, before correcting the rocket's altitude information in the navigation coordinate system calculated by the strapdown inertial measurement unit using the radar altimeter's measurement results, the output of the radar altimeter is checked for normality. This includes, but is not limited to, checking that the radar altimeter communication is normal, the measurement result flag is normal, and the mutual judgment results between the altimeter and the strapdown inertial measurement unit meet the requirements. If all conditions are met, the radar altimeter output is considered normal. This is the current output from the radar altimeter. The altitude calculated by the current strapdown inertial measurement unit is [height]. This is used to determine the discrimination threshold for the radar altimeter output. The accuracy is determined based on the performance specifications of the selected radar altimeter and the accuracy specifications of the strapdown inertial measurement unit.

[0013] Furthermore, the correction of the rocket's altitude information in the navigation coordinate system calculated by the strapdown inertial measurement unit using the radar altimeter's measurement results specifically involves: applying a PI filter to the altitude calculated by the strapdown inertial measurement unit using the radar altimeter's output. , ,in To convert the current radar altimeter output to the altitude position in the navigation coordinate system, This represents the current altitude position in the navigation coordinate system based on the current solution obtained from the strapdown system. This is to capture the current observation of the landing point's altitude and direction. These are the parameters for the PI filter, ranging from 0 to 1.

[0014] The advantages of this invention compared to the prior art are: (1) In the reusable launch vehicle return phase, the present invention uses a high-precision differential positioning receiver and combines the Kalman filtering algorithm to periodically correct the velocity and position of the rocket body calculated by the strapdown inertial navigation system, which can ensure the accuracy of the velocity and position output by the navigation system and thus greatly improve the landing accuracy. (2) When the receiver cannot stably output differential positioning information, the present invention further uses a radar altimeter to perform PI filtering correction on the altitude information calculated by the strapdown inertial navigation system, thereby quickly and effectively ensuring the measurement accuracy of the rocket's altitude direction and improving the reliability of reusable rocket landing. Attached Figure Description

[0015] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0016] During the landing process of a reusable rocket, the method of this invention employs multiple positioning units to correct the strapdown calculation results. When the reusable launch vehicle approaches the target landing point, due to its low flight altitude, the receiver can rely on ground base station information and the onboard high-precision differential receiver rover station for differential positioning. A Kalman filter method is used to correct the velocity and position through integrated navigation, controlling the rocket engine thrust and greatly improving landing accuracy. To ensure the accuracy and effectiveness of the differential positioning system output data, this invention distinguishes specific parameters output by designated receivers. During landing, short-term receiver failure (differential positioning system failure) may occur. To ensure the rocket still lands safely, this invention uses a radar altimeter to assist in measuring the altitude direction position, ensuring the accuracy of the altitude direction position and effectively guaranteeing the successful landing of the launch vehicle.

[0017] High-precision inertial navigation systems can directly output or indirectly obtain current time, attitude, velocity, and position information through calculation. Receivers can periodically output current high-precision differential positioning velocity and position information, and radar altimeters can periodically output current altitude information.

[0018] like Figure 1 The diagram shown is a flowchart of the method of the present invention, and the specific implementation steps are as follows: Step 1: Inertial Navigation System Strapdown Solution Based on the inertial navigation system (INS) output information, strapdown calculations are performed to obtain the current position and velocity information of the rocket body in the navigation coordinate system. The navigation coordinate system used in this invention is the landing point coordinate system, or simply the navigation system. The origin of the coordinate system is... At the theoretical landing point, The axis points in the direction of the line connecting the launch point and the sphere of the landing point within the horizontal plane of the landing point. The axis is perpendicular to the horizontal plane at the landing point and pointing upwards. The axis forms a right-handed system.

[0019] Step 2: Differential Receiver Integrated Navigation Condition Determination In the navigation coordinate system, based on the current altitude and directional position of the rocket body calculated by the strapdown system... The system determines whether the current position of the rocket body meets the requirements for differential positioning. The criterion is: ,in, This represents the application range of the receiver's differential positioning, and is a constant value, typically designed based on the effective range of the receiver's differential positioning data.

[0020] If the strapdown inertial navigation system (SINS) solution meets the above requirements, it proves that the current position of the rocket body meets the conditions for the receiver to enter differential positioning. The receiver then begins a self-test, including checking if the receiver communication is normal, if the PPS signal is normal, and if the positioning state is differential. Once the receiver self-test results meet the requirements, the receiver's differential positioning status output is compared with the SINS strapdown inertial navigation system (INS) solution results, i.e., the following criteria are met:

[0021] In the formula , , , , , The velocity and position of the rocket body in the navigation coordinate system are converted from the receiver differential positioning data at the current sampling time n. , , , , , The velocity and position of the rocket body in the navigation coordinate system at the current sampling time n, calculated by the current strapdown inertial navigation system. The differential receiver position discrimination threshold is a constant value. The velocity discrimination threshold for the differential receiver is a constant value. Position and velocity thresholds are typically designed based on the positioning accuracy of the differential receiver and the accuracy specifications of the inertial navigation system.

[0022] If the above conditions are met, it proves that the receiver's differential positioning is normal, and you can proceed to step three to use the differential receiver to access the integrated navigation loop for speed and position correction. If the conditions are not met, proceed to step four.

[0023] Step 3: Differential Receiver Integrated Navigation Based on the strapdown calculation results and the differential receiver output, the combined navigation filter observations are calculated as follows:

[0024] in , , , , , Convert the current PPS receiver data to velocity and position in the navigation coordinate system; , , , , , This represents the velocity and position in the navigation coordinate system calculated by the current PPS strapdown inertial navigation system.

[0025] After completing one integrated navigation filtering operation using Kalman filtering, the Kalman filtered state variables are obtained. The position and velocity errors in these state variables are then used to correct the strapdown induction solution results.

[0026] in: This represents the filtered velocity and position error.

[0027] After completing the Kalman filter correction, the current navigation cycle ends, and the aforementioned steps are repeated in the next navigation cycle.

[0028] Step 4: Altimeter-based navigation condition determination Based on the current altitude position in the navigation coordinate system calculated by the strapdown system of the rocket body. and velocity in the vertical direction The determination of whether the current motion state of the rocket body meets the altimeter measurement requirements is based on the following criteria: and , in, The measurement range of the radar altimeter is fixed with constant values, and the design is based on the performance specifications of the selected radar altimeter. The radar altimeter can track the maximum velocity of the rocket body, with constant values, and is designed according to the performance specifications of the selected radar altimeter. If the rocket's motion meets the radar altimeter's measurement requirements, a radar altimeter self-test begins, including checking if radar altimeter communication is normal and if the measurement result flags are normal. Once the radar altimeter self-test results meet the requirements, a cross-validation is performed between the radar altimeter output and the strapdown inertial navigation system (SINS) results, i.e., the following criteria are met:

[0029] in: To convert the current radar altimeter output to the altitude position in the navigation coordinate system, This represents the current altitude position in the navigation coordinate system based on the current solution obtained from the strapdown system. The output discrimination threshold of the radar altimeter is determined based on the performance indicators of the selected altimeter and strapdown inertial navigation system.

[0030] If the above conditions are met, it proves that the radar altimeter output is normal and you can proceed to step five. If any one of the conditions is not met, return to step one and carry out the next combined navigation cycle judgment.

[0031] Step 5: Radar altimeter integrated navigation The height position of the strapdown solution is obtained by using the output of a radar altimeter and applying PI filtering.

[0032] First, calculate the observation in the height direction:

[0033] in The current radar altimeter output is converted to the altitude position in the navigation coordinate system; This represents the current altitude position in the navigation coordinate system based on the current image capture and telemetry solution. This is an observation of the current landing point's altitude and direction.

[0034]

[0035] in These are PI filter parameters, bound as constants, designed according to the requirements of the navigation system, with a design range between 0 and 1.

[0036] After applying PI filtering As the navigation system's result of the navigation coordinates at that moment, the navigation system outputs this value to the control system for rocket landing control.

[0037] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A multi-source information fusion navigation method for the landing process of a reusable launch vehicle, characterized in that: The velocity and position information of the rocket body at the current moment are obtained by using strapdown inertial measurement unit (SIM) combined calculation. Determine whether the current altitude of the rocket body meets the differential positioning conditions of the differential receiver. If it does, use the rocket body velocity and position information output by the differential receiver to correct the rocket body velocity and position information in the navigation coordinate system calculated by the strapdown inertial measurement unit, and use the corrected results to perform landing navigation control of the launch vehicle. If the conditions are not met, the system will further determine whether the current altitude of the rocket body meets the measurement conditions of the radar altimeter. If it does, the system will use the measurement results of the radar altimeter to correct the altitude information of the rocket body in the navigation coordinate system calculated by the strapdown inertial measurement unit, and use the corrected altitude information to perform landing navigation control of the launch vehicle. If the conditions are not met, the system will wait for the next moment and re-determine the differential positioning conditions. The navigation coordinate system is the landing point coordinate system, with the origin at... At the theoretical landing point, The axis points in the direction of the line connecting the launch point and the sphere of the landing point within the horizontal plane of the landing point. The axis is perpendicular to the horizontal plane at the landing point and pointing upwards. The axis forms a right-handed system.

2. The multi-source information fusion navigation method for the landing process of a reusable launch vehicle according to claim 1, characterized in that: The determination of whether the current height of the rocket body meets the differential positioning conditions of the differential receiver specifically involves: if Then the condition is satisfied, where The current position of the rocket body in the navigation coordinate system, obtained from the inertial measurement unit's calculations, is its altitude position. This refers to the effective range of differential positioning for the receiver.

3. The multi-source information fusion navigation method for the landing process of a reusable launch vehicle according to claim 2, characterized in that: The aforementioned It is a constant value, determined based on the effective range of the receiver's differential positioning data.

4. The multi-source information fusion navigation method for the landing process of a reusable launch vehicle according to claim 1, characterized in that: Before correcting the velocity and position information of the rocket body in the navigation coordinate system calculated by the strapdown inertial measurement unit, the differential positioning status output of the differential receiver is checked to determine whether it is normal. This includes, but is not limited to, normal receiver communication, normal PPS signal, differential positioning status, and the output position and velocity information satisfying the following relationship with the strapdown inertial measurement unit: If all conditions are met, the differential positioning status output of the differential receiver is determined to be normal, where... , , , , , The velocity and position of the rocket body in the navigation coordinate system are converted from the receiver differential positioning data at the current sampling time n. , , , , , The velocity and position of the rocket body in the navigation coordinate system at the current sampling time n, obtained from the current strapdown inertial measurement unit calculation. The differential receiver position discrimination threshold is a constant value. The speed discrimination threshold for differential receivers is a constant value.

5. The multi-source information fusion navigation method for the landing process of a reusable launch vehicle according to claim 4, characterized in that: The aforementioned and The performance specifications of the selected differential receiver and the accuracy specifications of the strapdown inertial measurement unit are determined based on the performance specifications of the selected receiver.

6. The multi-source information fusion navigation method for the landing process of a reusable launch vehicle according to claim 1, characterized in that: The method of correcting the velocity and position information of the rocket body in the navigation coordinate system calculated by the strapdown inertial measurement unit (SIM) using the velocity and position information output by the differential receiver specifically involves: applying Kalman filtering based on the calculation results of the SIM and the output of the differential receiver, wherein the observed values... for: in , , , , , The differential receiver output of the current second pulse is converted to the velocity and position in the navigation coordinate system; , , , , , The velocity and position in the navigation coordinate system are calculated using the current second pulse strapdown inertial measurement unit. After performing a single integrated navigation filter using Kalman filtering, the state variables are obtained. The position and velocity errors in these state variables are then used to correct the solution results of the strapdown inertial measurement system. in The position and velocity errors are in the filtered state variables.

7. The multi-source information fusion navigation method for the landing process of a reusable launch vehicle according to claim 1, characterized in that: The determination of whether the current altitude of the rocket body meets the measurement conditions of the radar altimeter specifically refers to: if and Then the condition is satisfied, where, and These are the position and velocity information of the rocket body in the current navigation coordinate system, obtained from the strapdown inertial measurement unit (SIM) calculations. For the radar altimeter measurement range, This is the maximum velocity of the rocket body that the radar altimeter can track.

8. The multi-source information fusion navigation method for the landing process of a reusable launch vehicle according to claim 1, characterized in that: Before correcting the rocket's altitude information in the navigation coordinate system calculated by the strapdown inertial measurement unit using the radar altimeter's measurement results, the output of the radar altimeter is checked for normality. This includes, but is not limited to, checking that the radar altimeter communication is normal, the measurement result flag is normal, and the mutual judgment results between the altimeter and the strapdown inertial measurement unit meet the requirements. If all conditions are met, the radar altimeter output is considered normal. This is the current output of the radar altimeter. The altitude calculated by the current strapdown inertial measurement unit is [height]. The threshold for the radar altimeter output is set.

9. A multi-source information fusion navigation method for the landing process of a reusable launch vehicle according to claim 8, characterized in that: The aforementioned The accuracy is determined based on the performance specifications of the selected radar altimeter and the accuracy specifications of the strapdown inertial measurement unit.

10. A multi-source information fusion navigation method for the landing process of a reusable launch vehicle according to claim 1, characterized in that: The method of correcting the rocket's altitude information in the navigation coordinate system calculated by the strapdown inertial measurement unit using radar altimeter measurement results specifically involves: applying PI filtering to the altitude calculated by the strapdown inertial measurement unit using the radar altimeter output. , ,in To convert the current radar altimeter output to the altitude position in the navigation coordinate system, This represents the current altitude position in the navigation coordinate system based on the current solution obtained from the strapdown system. This is to capture the current observation of the landing point's altitude and direction. These are the parameters for the PI filter, ranging from 0 to 1.

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