Three-self-laser inertial measurement unit two-position self-aligning and self-checking method

Abstract

The invention relates to a three-self-laser inertial measurement unit two-position self-alignment self-checking method which comprises the following steps: after a two-position self-alignment process is rotated to a first position, starting solidification system self-alignment at the first position, and performing pure attitude tracking after a solidification system self-alignment result is obtained; after the two-position self-alignment process is switched to the second position, solidification system self-alignment at the second position is started, and pure attitude tracking is carried out after a solidification system self-alignment result is obtained; and averaging the self-alignment course angles of the two solidification systems to obtain a verification course angle, calculating a difference value between the verification course angle and the kalman self-alignment course angle, comparing the difference value with a set threshold value, if the difference value is greater than the threshold value, reporting an out-of-tolerance fault, and if the difference value is less than the threshold value, passing self-verification. According to the invention, the two-position self-aligning and self-checking method of the three-self-laser inertial measurement unit is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of inertial navigation, and relates to a two-position self-alignment and self-verification method for a three-autonomous laser inertial group, and in particular to an alignment method designed in other ways based on the premise that the two-position self-alignment process remains unchanged to realize the self-alignment azimuth result self-verification function. Background Art

[0002] Before the laser inertial group enters the navigation working state, it is necessary to establish an initial reference, that is, to calculate the three attitude angles of the carrier, including pitch angle, roll angle and azimuth angle. This process of establishing the initial reference for the inertial navigation system is called initial alignment. At present, the laser inertial group self-alignment technology includes two parts: coarse alignment and fine alignment. The three-self laser inertial group has two rotation axes. The fine alignment process adopts a two-position process, that is, the inertial group rotates around the inner frame axis to the first position according to the coarse alignment heading angle result, stays for a period of time, and then rotates to the second position. After staying for a period of time, it returns to zero and locks. The whole process adopts the Kalman filtering method. After filtering, the attitude angle is corrected. The corrected attitude angle is the result of the three attitude angles of self-alignment. Navigation begins when self-alignment ends. The self-alignment result directly affects the navigation accuracy, so the correctness of the self-alignment result is very important. At present, the three-self laser inertial group does not have the self-verification function of the alignment result. Summary of the invention

[0003] The technical problem solved by the invention is to overcome the deficiencies of the prior art and propose a two-position self-alignment and self-calibration method for a three-self laser inertial group.

[0004] The solution of the present invention is:

[0005] A three-laser inertial group two-position self-alignment and self-calibration method, comprising:

[0006] After the two-position self-alignment process rotates to the first position, the solidification system self-alignment of the first position is started, and the solidification system self-alignment of the first position is ended before the first dwell position ends, and pure posture tracking is performed after the solidification system self-alignment result is obtained;

[0007] After the two-position self-alignment process is transferred to the second position, the second position solidification system self-alignment is started, and the second position solidification system self-alignment is ended before the second dwell position ends, and pure posture tracking is performed after the solidification system self-alignment result is obtained;

[0008] The self-alignment attitudes of the two solidification systems are tracked until the inertial group returns to zero and is locked. The self-alignment heading angles of the two solidification systems are averaged to obtain the verification heading angle. The difference between the verification heading angle and the Kalman self-alignment heading angle is calculated and compared with the set threshold. If it is greater than the threshold, an out-of-tolerance fault is reported. If it is less than the threshold, the self-verification passes.

[0009] Preferably, the solidification system self-alignment method is as follows:

[0010] Define the inertial solidification coordinate system i b0 , the inertial solidification coordinate system is at t 0 The carrier coordinate system b is the coordinate system after inertial solidification at all times;

[0011] Let the latitude of the aiming point be L and calculate the attitude matrix Achieve self-alignment;

[0012] The posture matrix satisfy

[0013]

[0014] in is the attitude transformation matrix from the earth coordinate system e to the navigation coordinate system n, is the attitude transformation matrix from the inertial coordinate system i to the earth coordinate system e at time t, for i b0 The attitude transformation matrix from the i system to the i system, is the time b connected to i b0 The attitude transformation matrix of the system.

[0015] Preferably,

[0016]

[0017] Preferably, By time interval tt 0 OK, for

[0018]

[0019] Among them, w ie is the angular velocity of the Earth's rotation, tt 0 is time t and t 0 The time interval between moments.

[0020] Preferably, The gyro output at time t is obtained by solving the rotation vector.

[0021] Preferably, The solution is as follows:

[0022] Taking into account the acceleration deviation and the acceleration caused by external interference on the carrier, the projection of the accelerometer output of the inertial solidification coordinate system in the b system is f b for

[0023] f b =-g b +Δ+a

[0024] where g b is the projection of gravity acceleration in the b system, Δ is the accelerometer zero bias, a is the interference acceleration, and f b In the inertial solidification coordinate system i b0 The projection in the system is

[0025]

[0026] In the formula, g i is the projection of gravitational acceleration in the i system, where

[0027]

[0028] In the formula, g n is the projection of gravitational acceleration in the n system;

[0029] f ib0 Integrate both sides, that is

[0030]

[0031] Remember V ib0 =∫f ib0 dt, Ignoring the acceleration deviation and the acceleration caused by external interference on the carrier,

[0032]

[0033] G i Substitute it into the equation, and we get V at time t. i satisfy

[0034]

[0035] Take the middle time t 1 ,t 2 , where t 0 <t 1 <t 2 ,have:

[0036]

[0037] Using V ib0 (t 1 ) and V ib0 (t 2 ) to perform cross multiplication, that is

[0038]

[0039] Right now

[0040]

[0041] Preferably, the two-position self-alignment rotation process of the three-autonomous laser inertial group is as follows:

[0042] Binding of gravity and latitude information;

[0043] Perform anti-disturbance coarse alignment for 30 seconds, then unlock and rotate to the first position with the X gyro pointing east or west and then stay in the first position;

[0044] Go to the second position, the X gyro points west or east and stays at the second position;

[0045] Then it returns to zero, locks and stays for 3 seconds to complete the self-alignment. The three attitude angles at the end of the self-alignment are the alignment results of the two-position self-alignment algorithm.

[0046] Preferably, the threshold is set to 4 arc minutes.

[0047] The beneficial effects of the present invention compared with the prior art are:

[0048] (1) The present invention proposes a two-position self-alignment and self-checking method based on the fact that the two-position process remains unchanged;

[0049] (2) The present invention performs self-alignment of the solidification system based on two positions respectively, and then performs attitude navigation until the locking is completed. There is a heading effect between the self-alignment of the solidification system at a single position and the true north. The average of the heading angles of the self-alignment of the solidification system at the two positions is taken as the calibration heading angle, which can offset the heading effect of a single position, and the difference with the traditional Kalman filter is controlled within 4 arc minutes. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is the rotation process of the two-position self-alignment algorithm of the three-autonomous laser inertial group. DETAILED DESCRIPTION

[0051] The present invention will be further described below in conjunction with the accompanying drawings.

[0052] The present invention proposes a two-position self-alignment and self-calibration method for a three-autonomous laser inertial group, which mainly includes the following steps:

[0053] (1) On the basis of the two-position process remaining unchanged, a self-alignment and self-verification method is designed. After the two-position process rotates to the first position (i.e., searching for the east or west), the solidification system self-alignment of the first position is started (the solidification system self-alignment method will be introduced later), and the solidification system self-alignment of the first position is ended before the first stop position ends. After the solidification system self-alignment result is obtained, pure posture tracking is performed;

[0054] (2) After the two-position process is transferred to the second position, the solidification system self-alignment of the second position is started, and the solidification system self-alignment of the second position is ended before the second dwell position ends. After the solidification system self-alignment result is obtained, pure posture tracking is performed;

[0055] (3) The self-alignment attitudes of the two solidification systems are tracked until the inertial group returns to zero and is locked. The self-alignment heading angles of the two solidification systems are averaged to obtain the verification heading angle. The difference between the verification heading angle and the Kalman self-alignment heading angle is compared with the set threshold. If it is greater than the threshold, an out-of-tolerance fault is reported. If it is less than the threshold, the self-verification passes.

[0056] The solidification system alignment calculation adopted by the two positions of the laser inertial group first defines an auxiliary coordinate system name: the base inertial coordinate system i b0 , also known as the inertial solidification coordinate system. This coordinate system is at t 0 The carrier coordinate system b is the coordinate system after inertial solidification. Similarly, let the latitude of the aiming point be L, and the attitude matrix It can be decomposed into the product of four correlation matrices, as shown below:

[0057]

[0058] In the formula,

[0059]

[0060] The time interval tt 0 OK, for

[0061]

[0062] w ie is the angular velocity of the Earth's rotation, tt 0 is the time interval, w ie (tt 0 ) is tt 0 The angle of the Earth's rotation during the time interval.

[0063] From b to i b0 The attitude transformation matrix between systems; for i b0 The attitude transformation matrix from system i to system i;

[0064] Using gyro output to calculate in real time, represents the time t The matrix is ​​obtained by solving the rotation vector according to the gyro output at time t.

[0065] If the acceleration deviation and the acceleration caused by external interference of the carrier are taken into account, the accelerometer output f of the rough alignment of the inertial solidification coordinate system b for

[0066] fb =-g b +Δ+a

[0067] where f b is the projection of the accelerometer output in the b frame, g b is the projection of gravity acceleration in the b system, Δ is the accelerometer zero bias, a is the interference acceleration, and f b In the inertial solidification coordinate system i b0 The projection in the system is

[0068]

[0069] In the formula, f ib0 is the projection of the accelerometer output in the ib0 system, g b Approximately equal to g i , g i is the projection of gravitational acceleration in the i system, where

[0070]

[0071] In the formula, g n is the projection of gravitational acceleration in the n system, is the formula (1) The transposed matrix of f represents the attitude matrix from the e system to the i system. ib0 Integrate both sides, that is

[0072]

[0073] Remember V ib0 =∫f ib0 dt, Ignoring the acceleration deviation and the acceleration caused by external interference on the carrier,

[0074]

[0075] G i Substituting into, we can get V at time t i satisfy

[0076]

[0077] Take the middle time t 1 ,t 2 , where t 0 <t 1 <t 2 ,have:

[0078]

[0079] It is a 3x3 matrix, and 3 more elements need to be constructed, so use Vib0 (t 1 ) and V ib0 (t 2 ) to perform cross multiplication, that is

[0080]

[0081] Right now

[0082]

[0083] Solved Substituting into the above formula, we can obtain the initial posture transformation matrix. The angle information output by the gyroscope is used to obtain the alignment error in real time, so the alignment error caused by the angular velocity interference of the carrier can be effectively isolated. This method is a solidification system self-alignment method.

[0084] Figure 1 The figure shows the two-position self-alignment rotation process of the three-autonomous laser inertial group. First, the gravity latitude information is bound, and then the anti-disturbance coarse alignment is performed for 30 seconds. Then the rotation is unlocked and the X-gyro is turned to the first position, pointing east (west) and then staying at position 1. The X-gyro is turned to the second position, pointing west (east) and then staying at position 2. Then it returns to zero and locks for 3 seconds to end the self-alignment. The three attitude angles at the end of the self-alignment are the alignment results of the two-position self-alignment algorithm. The three attitude angles are recorded as the pitch angle a1, the roll angle a2 and the heading angle a3. According to Figure 1 As shown in the figure, the process from the X-gyro pointing east (west) to the X-gyro pointing west (east) is the stop position 1. During the stop position 1, the solidification system alignment calculation is started, and three attitude angles are obtained. Then, pure attitude navigation is performed to Figure 1 The zero return lock is completed, and the heading angle at the time of zero return lock is recorded as W1. The process from the X-gyro pointing west (east) to zero return is the dwell position 2. During the dwell position 2, the solidification system alignment calculation is started, and three attitude angles are obtained. Then pure attitude navigation is performed to Figure 1 The zero return and locking are completed, and the heading angle at the time of zero return and locking is recorded as W2. The two heading angles W1 and W2 are averaged to obtain the calibration heading angle W12. The calibration heading angle W12 is subtracted from the heading angle a3, and the difference is compared with the set threshold. If it is less than the threshold, the self-calibration passes. If it is greater than the threshold, the three-autonomous laser inertial group reports a fault, that is, the self-calibration fails, and the subsequent process is terminated.

[0085] The feasibility and performance of the method of the present invention have been verified through multiple tests. The laboratory laser inertial group processing equipment was tested and verified on a laboratory marble platform. The ambient temperature was about 20°C. Ten groups of self-alignment tests were performed at the same position. The alignment results of the 10 groups of self-alignment self-verification algorithms and Kalman self-alignment algorithms were statistically analyzed. The statistical results are shown in Table 1. As shown in Table 1, the dispersion of the solidification system alignment at the first position and the solidification system alignment at the second position is within 200 arc seconds, which is a large deviation from the true value. The difference between the average of the two positions and the Kalman filter algorithm is within one arc minute, which is a small difference.

[0086] Table 1 Statistical results of 10 groups of tests

[0087]

[0088] The present invention provides a two-position self-alignment process of a three-autonomous laser inertial group, designs a new method for solving a heading angle based on the unchanged two-position process, and the heading angle is named a verification heading angle. The verification heading angle is obtained when the two-position self-alignment is completed, and the self-alignment heading angle is compared with the verification heading angle, thereby realizing a two-position self-alignment self-verification method of a three-autonomous laser inertial group.

[0089] The technical problem further solved by the present invention is to realize that the difference threshold of the heading angle of the two self-alignment methods of the three-auto laser inertial group is no more than four arc minutes, which solves the technical problem of self-alignment and self-verification and realizes the two-position self-alignment and self-verification function of the three-auto laser inertial group.

[0090] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for self-alignment and self-calibration of a three-axis laser inertial group in two positions, characterized in that: Including: After the two-position self-alignment process rotates to the first position, start the solidification system self-alignment at the first position, end the solidification system self-alignment at the first position before the end of the first stay position, and perform pure attitude tracking after obtaining the solidification system self-alignment result; After the two-position self-alignment process rotates to the second position, start the solidification system self-alignment at the second position, end the solidification system self-alignment at the second position before the end of the second stay position, and perform pure attitude tracking after obtaining the solidification system self-alignment result; The two solidification system self-alignments track the attitude until the inertial unit returns to zero and is locked. Average the heading angles of the two solidification system self-alignments to obtain the calibration heading angle. Calculate the difference between the calibration heading angle and the Kalman self-alignment heading angle, and compare it with the set threshold. If it is greater than the threshold, report an out-of-tolerance fault. If it is less than the threshold, the self-calibration passes.

2. A three-autonomous laser inertial group two-position self-alignment and self-calibration method according to claim 1, characterized in that: The method for solidification system self-alignment is as follows: Define the inertial solidification coordinate system i b0 , the inertial solidification coordinate system is the coordinate system after the carrier coordinate system b system is inertially solidified at time t0; Let the latitude of the aiming point be L and calculate the attitude matrix Achieve self-alignment; The posture matrix satisfy in is the attitude transformation matrix from the earth coordinate system e to the navigation coordinate system n, is the attitude transformation matrix from the inertial coordinate system i to the earth coordinate system e at time t, for i b0 The attitude transformation matrix from the i system to the i system, is the time b connected to i b0 The attitude transformation matrix of the system.

3. The two-position self-alignment self-calibration method for a three-self laser inertial unit according to claim 2, characterized in that 4. A three-autonomous laser inertial group two-position self-alignment and self-calibration method according to claim 2, characterized in that: Determined by the time interval t-t0, Among them, w ie is the angular velocity of the Earth’s rotation, and t-t0 is the time interval between time t and time t0.

5. The method for self-alignment and self-calibration of a three-axis laser inertial group in two positions according to claim 2 is characterized in that: The gyro output at time t is obtained by solving the rotation vector.

6. A three-autonomous laser inertial group two-position self-alignment and self-calibration method according to claim 2, characterized in that: The solution is as follows: Taking into account the acceleration deviation and the acceleration caused by external interference on the carrier, the projection of the accelerometer output of the inertial solidification coordinate system in the b system is f b for f b =-g b +D+a where g b is the projection of gravity acceleration in the b system, Δ is the accelerometer zero bias, a is the interference acceleration, and f b In the inertial solidification coordinate system i b0 The projection in the system is In the formula, g i is the projection of gravitational acceleration in the i system, where In the formula, g n is the projection of gravitational acceleration in the n system; f ib0 Integrate both sides, that is Remember V ib0 =∫f ib0 dt, Ignoring the acceleration deviation and the acceleration caused by external interference on the carrier, G i Substitute it into the equation, and we get V at time t. i satisfy Take the intermediate times t1 and t2, where t0 < t1 < t2, and there is: Using V ib0 (t1) and V ib0 (t2) is cross-producted, that is, That is 7. The method for self-alignment and self-calibration of a three-axis laser inertial group in two positions according to claim 1 is characterized in that: The rotation process of the two-position self-alignment of the three-self laser inertial unit is as follows: Perform gravity latitude information binding; Perform anti-disturbance coarse alignment for 30 s, then unlock and rotate to the first position where the X gyro points east or west and stay at the first position; Rotate to the second position where the X gyro points west or east and stay at the second position; Then return to zero and lock for 3 s to end the self-alignment. The three attitude angles at the end of the self-alignment are the alignment results of the two-position self-alignment algorithm.

8. The method for self-alignment and self-calibration of a three-axis laser inertial group in two positions according to claim 1 is characterized in that: The set threshold is 4 angular minutes.

Images