A method for non-latitude alignment of a swing base of a hemispherical resonant gyro strapdown inertial navigation system assisted by a micromechanical gyroscope

Abstract

The present invention provides a method for non-latitude alignment of a swing base of a hemispherical resonant gyro strapdown inertial navigation system assisted by a micromechanical gyroscope, and belongs to a signal processing method in the field of automation technology. The present invention is aimed at a force feedback mode HRG strapdown inertial navigation system for navigation, which is swaying due to the impact of waves, and the carrier attitude angular velocity exceeds the HRG angular velocity measurement range, and the latitude information is unknown. The MEMS gyroscope coaxially installed with the HRG inertial navigation system is used as an angular velocity measurement auxiliary device, and the problem of initial alignment and latitude estimation under the swaying state of the ship is solved through gravity vector geometric constraints and inertial system alignment methods. The present invention can realize the initial alignment of the carrier when it is in a swaying state and the latitude is unknown, has low requirements for the motion state and external latitude information, and has high autonomy and robustness.

Description

Technical Field

[0001] The invention relates to a non-latitude alignment method for a swing base of a hemispherical resonant gyro strapdown inertial navigation system assisted by a micro-mechanical gyro, and a signal processing method in the field of automation technology. Background Art

[0002] The invention is designed to be a non-latitude alignment method for a swaying base of a hemispherical resonator gyro (HRG) strapdown inertial navigation system assisted by a micro-electromechanical systems (MEMS) gyro. More specifically, when a force feedback mode HRG strapdown inertial navigation system for navigation is swaying due to the impact of sea waves, the carrier attitude angular velocity exceeds the HRG angular velocity measurement range, and the latitude information is unknown, a MEMS gyro coaxially installed with the HRG inertial navigation system is used as an angular velocity measurement auxiliary device, and the problem of initial alignment and latitude estimation under the swaying condition of the ship is solved through gravity vector geometric constraints and an inertial system alignment method. The invention belongs to a signal processing method in the field of automation technology, and realizes initial alignment when the carrier is in a swaying condition and the latitude is unknown.

[0003] The hemispherical resonator gyroscope is a new type of inertial navigation-grade solid gyroscope. It is a new type of vibration gyroscope that uses the Coriolis effect of standing waves excited on a hemispherical resonator to measure the angular velocity of the base rotation. Since the hemispherical resonator gyroscope has no high-speed moving parts, does not require temperature control, has low internal power consumption, and has the least potential failure factors, it has high measurement accuracy, super stability and reliability, good shock and vibration resistance and temperature performance. In particular, it has a working life of more than 15 years, and the reliability of 15 years of continuous work can reach 0.995. Based on the above advantages, the strapdown inertial navigation system constructed by the hemispherical resonator gyroscope will be one of the ideal choices for inertial navigation equipment for navigation.

[0004] However, compared with traditional laser gyroscopes and fiber optic gyroscopes, the measurement range of the force feedback mode HRG gyroscope is smaller. Although most of the movements of ocean vehicles are in a low angular velocity state, due to the influence of different sea conditions, the ocean vehicle may experience violent swinging movements during the alignment process of the moored state, and the angular velocity generated may exceed the measurement range of the force feedback mode HRG. Although the full-angle mode HRG has a larger measurement range, the current technology is immature, the domestic production capacity is low, and it is not suitable for large-scale equipment. In addition, the current measurement accuracy is lower than that of the force feedback mode HRG.

[0005] Although the measurement accuracy of MEMS gyro is low and cannot reach the measurement accuracy of HRG for angular rate, the angular rate measurement range is large and can be used as an angular rate measurement instrument when the angular rate exceeds the measurement range of HRG device. Therefore, MEMS gyro is selected as an auxiliary device to realize the alignment of HRG strapdown inertial navigation system. This will provide a strong guarantee for subsequent ship navigation.

[0006] As a key technology of the strapdown inertial navigation system, the initial alignment technology, its alignment speed and alignment accuracy will directly determine the startup response time and attitude measurement accuracy of the strapdown inertial navigation system. Traditional initial alignment technology does not require longitude information when starting alignment, but it is heavily dependent on external latitude information, which will reduce the autonomy and safety of the system and affect its battlefield survivability. This effect is more significant under the swing base.

[0007] Under the condition of a rocking base, the angular velocity caused by the rocking motion of the waves is much greater than the angular velocity of the earth's rotation, which makes the gyro output have a low signal-to-noise ratio. Therefore, it is impossible to directly extract the earth's rotation angular velocity vector from the gyro output information. At this time, the traditional analytical static base alignment method will not work. In addition, since the compass alignment and Kalman filter combined alignment method needs to meet the condition that the misalignment angle is a small angle when applied, it is impossible to complete the initial alignment under the conditions of arbitrary azimuth and heading angles of the rocking base.

[0008] Although the Earth's rotation angular velocity cannot be used directly to construct constraint equations under the condition of a rocking base, the inertial system alignment method uses the gravity acceleration vectors of two or more inertial systems at different times to construct corresponding constraint relationships and then determine the attitude transformation matrix. Therefore, it is widely used for the initial alignment of a rocking base. In essence, the dual-vector inertial system alignment method based on the velocity integral form belongs to the category of least squares estimation, and has a good suppression effect on interference such as device noise and external environmental vibration.

[0009] However, the traditional sway base alignment method, including the analytical alignment method of the inertial system based on dual vectors, requires the use of external devices such as GPS and beacon transducers to obtain local latitude information during initial alignment, which will reduce the autonomy and safety of the strapdown inertial navigation system. For the initial alignment of the sway base under conditions such as loss of GPS signal lock and denial on the surface and inability to receive positioning signals underwater, the traditional sway base initial alignment method will not be able to complete the alignment task, which greatly limits the application scope of the strapdown inertial navigation system.

[0010] Therefore, in order to solve the problem of initial alignment without latitude under the swing base, the present invention proposes a method for aligning the swing base without latitude of the HRG strapdown inertial navigation system in a force feedback mode assisted by a MEMS gyroscope. First, a micromechanical gyroscope is used as an auxiliary device to realize the reconstruction of the carrier angular velocity information; then, in view of the external conditions of inaccurate latitude information, a latitude estimation method based on the apparent motion of gravity in the inertial system and the geometric constraints of the gravity vector at two different moments in the inertial space is designed to realize the estimation of latitude information. Finally, the attitude matrix chain rule is used to convert the attitude matrix solution problem into three matrices: the initial moment attitude matrix, the matrix of the carrier coordinate system and the solidified carrier coordinate system, and the problem of solving the conversion matrix of the navigation coordinate system and the solidified navigation coordinate system, and finally the carrier attitude matrix is ​​obtained to realize the initial alignment of the HRG inertial navigation system under the condition of no latitude. This method belongs to a signal processing method in the field of automation technology, and can realize the initial alignment of the HRG strapdown inertial navigation system based on the force feedback mode under the bad sea conditions where the latitude information is unknown and the carrier angular motion is violent. Summary of the invention

[0011] The purpose of the present invention is to solve the problems existing in the above-mentioned prior art, and further provide a method for non-latitude alignment of a swing base of a hemispherical resonant gyro strapdown inertial navigation system assisted by a micro-mechanical gyroscope.

[0012] The objective of the present invention is achieved through the following technical solutions:

[0013] A method for non-latitude alignment of a swing base of a hemispherical resonant gyro strapdown inertial navigation system assisted by a micromechanical gyro comprises the following steps:

[0014] Step 1: Install high-precision HRG and MEMS gyroscopes in force feedback mode on the ship, with the x-axis of the two gyroscopes pointing parallel to the starboard side of the ship, the y-axis pointing to the bow, and the z-axis pointing to the sky, and connect them to a computer equipped with data acquisition software;

[0015] Step 2: During the ship alignment process, the data of the hemispherical resonant gyro strapdown inertial navigation system and the MEMS gyro are collected simultaneously;

[0016] Step 3: By setting a threshold, determine the data whose angular rate in the swing motion exceeds the HRG measurement range, and use the MEMS gyro output as the angular rate output value of the HRG strapdown inertial navigation system on the axis;

[0017] Step 4: Based on the apparent motion of gravity in the inertial system, the local latitude information is estimated using the geometric constraints of the gravity vector at two different times in the inertial space;

[0018] Step 5: Use the inertial system alignment method to achieve alignment;

[0019] Step 6: Store the attitude matrix obtained by alignment into the navigation computer to complete the alignment process.

[0020] Furthermore, the force feedback mode HRG measurement accuracy described in step 3 is high, but the measurement range is limited. When the angular motion amplitude is large and exceeds the measurement range of the force feedback mode HRG gyro, self-alignment cannot be completed. A MEMS gyro is used to assist it in completing the swing state alignment. The specific method is:

[0021] 1) Simultaneously collect the angular rate data of the strapdown inertial navigation system HRG and the angular rate information measured by the coaxially mounted MEMS gyroscope, and set the threshold λ according to the HRG measurement range;

[0022] 2) Compare the HRG measurement value with the threshold and choose whether to use the MEMS output as alignment data. The specific method is as follows:

[0023]

[0024]

[0025]

[0026] Among them, IMUx, IMUy, IMUz are the data of the three-axis gyroscope used for alignment, t is the time of data acquisition, HRGx, HRGy, HRGz are the data output by the HRG three-axis gyroscope, MEMSx, MEMSy, MEMSz are the data output by the MEMS three-axis gyroscope, λ is the set threshold, and the reconstructed gyroscope data and the acceleration data of the inertial navigation system are used for the alignment of the rocking base.

[0027] Furthermore, the local latitude information is estimated by using the geometric constraints of the gravity vector at two different moments in the inertial space as described in step 4. The specific method is as follows:

[0028] 1) The direction of gravitational acceleration g in inertial space is g i (t1) becomes g i (t2), g i (t1) and g i The angle between (t2) is θ, which can be determined by the following formula:

[0029]

[0030] In the above formula, t1=t2 / 2, t2 is the current time in the alignment process, and t1 is the middle time in the alignment process;

[0031] 2) Angle α is g i (t1) becomes g i (t2) is the angle of rotation during the process, expressed as:

[0032] α=ω ie (t2-t1);

[0033] ω ie is the angular rate of the Earth's rotation.

[0034] 3) According to the geometric relationship:

[0035]

[0036] Where L is the local latitude, and the final expression for the latitude estimate is:

[0037]

[0038] The final latitude estimation result L is obtained.

[0039] Furthermore, the alignment is achieved by using the inertial system alignment method described in step 5, and the specific method is:

[0040] 1) According to the matrix chain rule, Expand into Calculate the three matrices obtained by decomposition respectively;

[0041] 2) Due to is a constant, that is, the n(t) system rotates with respect to the n(0) system. The above equation can be solved to get Expression:

[0042]

[0043] For convenience of representation, for any three-dimensional column vector V = [V x V y V z ] T , use (V×) to represent the third-order matrix:

[0044]

[0045] Where I is the identity matrix, ω ie is the Earth's rotation angular rate, and t is the current moment.

[0046] So we have:

[0047] g n(0) = -g[sinω ie tcosL(1-cosω ie t)sinLcosL 1-(1-cosω ie t)cos 2 L] T ;

[0048] where gn(0) is the projection of gravitational acceleration in the n(0) system.

[0049] Secondly, the specific force output of the accelerometer is projected on the b(0) system as:

[0050]

[0051] in:

[0052]

[0053]

[0054]

[0055] In the above formula, Δθ1 and Δθ2 are the angular rate increment information obtained by gyro measurement. is the equivalent rotation vector obtained after cone error compensation.

[0056] 3): Use the dual vector pose determination algorithm to solve In order to reduce the influence of linear motion interference, the equation is integrated during the initial alignment process.

[0057]

[0058] in and are the projections of the gravity vector in the initial carrier coordinate system for two periods of time, and They are the projections of the gravity vector in the initial navigation coordinate system for two periods of time.

[0059] The two satisfy the following relationship:

[0060]

[0061] The initial strapdown matrix is ​​calculated by the following formula:

[0062]

[0063] In order to obtain the attitude matrix at the end of the rough alignment, the following formula can be used for calculation

[0064]

[0065] Based on this, the strapdown matrix is ​​obtained to complete the latitude estimation and initial alignment.

[0066] The beneficial effects of the present invention are:

[0067] The present invention aims at solving the problems of initial alignment and latitude estimation under the ship swaying condition by using a MEMS gyroscope coaxially installed with the HRG inertial navigation system as an angular velocity measurement auxiliary device, and by using gravity vector geometric constraints and an inertial system alignment method, when a force feedback mode HRG strapdown inertial navigation system for navigation is swayed by the impact of waves, the carrier attitude angular velocity exceeds the HRG angular velocity measurement range, and the latitude information is unknown.

[0068] The advantages of the present invention are: the non-latitude alignment method of the swing base of the HRG strapdown inertial navigation system assisted by the MEMS gyroscope can realize the swing base alignment under the condition of low measurement range of HRG in the existing force feedback mode and latitude position, has low requirements for the motion state and external latitude information, and has high autonomy and robustness. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 It is a schematic diagram of the process of the present invention.

[0070] Figure 2 It is a diagram showing the swinging state of the carrier of the present invention.

[0071] Figure 3 This is a diagram of the alignment results of the strapdown inertial navigation system of the present invention.

[0072] Figure 4 This is a diagram of the latitude estimation result of the present invention. DETAILED DESCRIPTION

[0073] The present invention will be further described in detail below in conjunction with the accompanying drawings: This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method is given, but the protection scope of the present invention is not limited to the following embodiments.

[0074] like Figures 1 to 4 As shown, the present embodiment involves a method for non-latitude alignment of a swing base of a hemispherical resonant gyro strapdown inertial navigation system assisted by a micromechanical gyroscope, and the schematic diagram of the method is shown in FIG. Figure 1 The object of the present invention is achieved by the following steps:

[0075] Step 1: Install high-precision HRG and MEMS gyroscopes in force feedback mode on the ship, with the x-axis of the two gyroscopes pointing parallel to the starboard side of the ship, the y-axis pointing to the bow, and the z-axis pointing to the sky, and connect them to a computer equipped with data acquisition software;

[0076] Step 2: During the ship alignment process, data of the hemispherical resonant gyro strapdown inertial navigation system and the MEMS gyro are collected simultaneously;

[0077] Step 3: According to the HRG measurement range, by setting the threshold λ, determine the data of the angular rate in the swing motion exceeding the HRG measurement range, and choose whether to use the MEMS output as alignment data by the following formula:

[0078]

[0079]

[0080]

[0081] The reconstructed gyro data and the acceleration data of the inertial navigation system are used for the alignment of the rocking base.

[0082] Step 4: Based on the apparent motion of gravity in the inertial system, the local latitude information is estimated using the geometric constraints of the gravity vector at two different moments in the inertial space;

[0083] The direction of gravitational acceleration g in inertial space is given by g i (t1) becomes g i (t2), g i (t1) and g i The angle between (t1) and (t2) is θ, where t1 = t2 / 2. The angle θ can be determined by the following formula:

[0084]

[0085] The angle α is g i (t1) becomes g i (t2) is the angle of rotation during the process, expressed as:

[0086] α=ω ie (t2-t1);

[0087] ω ie is the angular rate of the Earth's rotation.

[0088] According to the geometric relationship:

[0089]

[0090] Where L is the local latitude, and the final expression for the latitude estimate is:

[0091]

[0092] Step 5: Use the inertial system alignment method to achieve alignment.

[0093] According to the matrix chain rule, Expand into Calculate the three matrices obtained by decomposition respectively;

[0094] because is a constant, that is, the n(t) system rotates with respect to the n(0) system. The above equation can be solved to get Expression:

[0095]

[0096] Use the following method to find:

[0097]

[0098]

[0099]

[0100] In the above formula, Δθ1 and Δθ2 are the angular rate increment information obtained by gyro measurement. is the angular increment between the two sampling moments after compensation, t is the current moment, and tm is the moment when the previous angular increment compensation value is generated, that is, the two sampling moments before the two current t moments.

[0101] Then use the dual vector pose determination algorithm to solve

[0102]

[0103] In order to obtain the attitude matrix at the end of the rough alignment, the following formula can be used for calculation

[0104]

[0105] Step 6: Store the attitude matrix obtained by alignment into the navigation computer to complete the alignment process.

[0106] The effect of the present invention can be verified by the following simulation:

[0107] The simulation experiment uses a gyro drift of 0.01 / h and a random walk of angular The full-angle mode hemispherical resonant gyro and accelerometer zero bias are 10 -4 g inertial device, the sampling frequency is 100Hz, the gyro angle measurement range is ±8 / h; the MEMS gyro drift is 0.5 / h, and the angle random walk is Since the reference value of the attitude can be obtained in real time in the simulation environment, as long as the comparative experiment is carried out under the same swinging conditions, the obtained alignment error can be used to evaluate the alignment performance of each algorithm. Therefore, the simulation sets the local latitude to 45.72° (Harbin) and the simulation time to 200s. Specifically, the simulation sets the swing equilibrium position to 0° roll, 0° pitch and 45° heading, the initial phase is 0°, and the swing motion is set to the following conditions:

[0108] The rolling amplitude is 12° and the period is 8s;

[0109] The pitch amplitude is 4° and the period is 5s;

[0110] The amplitude of the bow roll is 3° and the period is 5s.

[0111] The simulation results are as follows Figure 2 As shown, Figure 2 The three figures in the middle represent the rocking base and roll, pitch and heading (north-west is positive) respectively.

[0112] The alignment result is as follows Figure 3 As shown, the roll error is -0.0002°, the pitch error is -0.0006°, and the heading error is 0.7213°. It can be seen that the algorithm realizes the alignment of the force feedback mode HRG. Therefore, the method proposed in the present invention solves the angular velocity measurement problem of the navigation system when the angular velocity amplitude exceeds the HRG measurement range, and has a faster alignment convergence speed and better noise suppression capability. At the same time, as the alignment time increases, the fluctuation of the attitude estimation result continues to decrease. In order to achieve better convergence of the attitude estimation result, the alignment time can be appropriately increased. The present invention provides a good initial condition for precise alignment.

[0113] The latitude estimation result is as follows Figure 4 As shown, the latitude estimation error is 0.6699°, which can effectively estimate the local latitude information and has a good alignment convergence speed, achieving latitude estimation in a shorter time. At the same time, as the alignment time increases, the influence of noise continues to decrease, and the fluctuation of the estimation result continues to decrease. Therefore, in order to achieve better convergence of the latitude estimation result, the alignment time can be appropriately increased. The present invention provides a good initial condition for precise alignment.

[0114] The above are only preferred specific embodiments of the present invention, which are all different implementations based on the overall concept of the present invention, and the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for non-latitude alignment of a swing base of a hemispherical resonant gyro strapdown inertial navigation system assisted by a micromechanical gyro, characterized in that: The following steps are involved: Step 1: Install high-precision HRG and MEMS gyroscopes in force feedback mode on the ship, with the x-axis of the two gyroscopes pointing parallel to the starboard side of the ship, the y-axis pointing to the bow, and the z-axis pointing to the sky, and connect them to a computer equipped with data acquisition software; Step 2: During the ship alignment process, the data of the hemispherical resonant gyro strapdown inertial navigation system and the MEMS gyro are collected simultaneously; Step 3: By setting a threshold, determine the data whose angular rate in the swing motion exceeds the HRG measurement range, and use the MEMS gyro output as the angular rate output value of the HRG strapdown inertial navigation system on the axis; Step 4: Based on the apparent motion of gravity in the inertial system, the local latitude information is estimated using the geometric constraints of the gravity vector at two different times in the inertial space; Step 5: Use the inertial system alignment method to achieve alignment; Step 6: Store the attitude matrix obtained by alignment into the navigation computer to complete the alignment process.

2. The method for non-latitude alignment of a swing base of a micro-mechanical gyro-assisted hemispherical resonant gyro strapdown inertial navigation system according to claim 1, characterized in that: The force feedback mode HRG measurement accuracy described in step 3 is high, but the measurement range is limited. When the angular motion amplitude is large and exceeds the measurement range of the force feedback mode HRG gyro, self-alignment cannot be completed. A MEMS gyro is used to assist it in completing the swing state alignment. The specific method is as follows: 1) Simultaneously collect the angular rate data of the strapdown inertial navigation system HRG and the angular rate information measured by the coaxially mounted MEMS gyroscope, and set the threshold λ according to the HRG measurement range; 2) Compare the HRG measurement value with the threshold and choose whether to use the MEMS output as alignment data. The specific method is as follows: Among them, IMUx, IMUy, IMUz are the data of the three-axis gyroscope used for alignment, t is the time of data acquisition, HRGx, HRGy, HRGz are the data output by the HRG three-axis gyroscope, MEMSx, MEMSy, MEMSz are the data output by the MEMS three-axis gyroscope, λ is the set threshold, and the reconstructed gyroscope data and the acceleration data of the inertial navigation system are used for the alignment of the rocking base.

3. The method for non-latitude alignment of a swing base of a micro-mechanical gyro-assisted hemispherical resonant gyro strapdown inertial navigation system according to claim 1, characterized in that: The method described in step 4 is to estimate the local latitude information by using the geometric constraints of the gravity vector at two different times in the inertial space. The specific method is: 1) The direction of gravitational acceleration g in inertial space is g i (t1) becomes g i (t2), g i (t1) and g i The angle between (t2) is θ, which can be determined by the following formula: In the above formula, t1=t2 / 2, t2 is the current time in the alignment process, and t1 is the middle time in the alignment process; 2) Angle α is g i (t1) becomes g i (t2) is the angle of rotation during the process, expressed as: a = oh ie (t2-t1); ω ie is the Earth's rotation angular rate; 3) According to the geometric relationship: Where L is the local latitude, and the final expression for the latitude estimate is: The final latitude estimation result L is obtained.

4. The method for non-latitude alignment of a swing base of a micro-mechanical gyro-assisted hemispherical resonant gyro strapdown inertial navigation system according to claim 1, characterized in that: The alignment is achieved by using the inertial system alignment method described in step 5. The specific method is as follows: 1) According to the matrix chain rule, Expand into Calculate the three matrices obtained by decomposition respectively; 2) Due to is a constant, that is, the n(t) system rotates with respect to the n(0) system. The above equation can be solved to get Expression: For convenience of representation, for any three-dimensional column vector V = [V x V y V z ] T , use (V×) to represent the third-order matrix: Where I is the identity matrix, ω ie is the Earth's rotation angular rate, t is the current moment; So we have: g n(0) =-g[sinω ie tcosL (1-cosω ie t)sinLcosL 1-(1-cosω ie t)cos 2 L] T ; where g n(0) is the projection of gravitational acceleration in the n(0) system; Secondly, the specific force output of the accelerometer is projected on the b(0) system as: in: In the above formula, Δθ1 and Δθ2 are the angular rate increment information obtained by gyro measurement. is the equivalent rotation vector obtained after cone error compensation; 3): Use the dual vector pose determination algorithm to solve In order to reduce the influence of linear motion interference, the equation is integrated during the initial alignment process. Among them, F1 b(0) and are the projections of the gravity vector in the initial carrier coordinate system for two periods of time, and are the projections of the gravity vector in the initial navigation coordinate system for two periods of time; The two satisfy the following relationship: The initial strapdown matrix is ​​calculated by the following formula: In order to obtain the attitude matrix at the end of the rough alignment, the following formula can be used for calculation Based on this, the strapdown matrix is ​​obtained to complete the latitude estimation and initial alignment.

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