CN114166215B - Indexing mechanism of rotary strapdown inertial measurement unit (SIU) and IMU synchronous calibration and compensation method - Google Patents
Indexing mechanism of rotary strapdown inertial measurement unit (SIU) and IMU synchronous calibration and compensation method Download PDFInfo
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- CN114166215B CN114166215B CN202111376411.7A CN202111376411A CN114166215B CN 114166215 B CN114166215 B CN 114166215B CN 202111376411 A CN202111376411 A CN 202111376411A CN 114166215 B CN114166215 B CN 114166215B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C21/00—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00
- G01C21/10—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration
- G01C21/12—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration executed aboard the object being navigated; Dead reckoning
- G01C21/16—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration executed aboard the object being navigated; Dead reckoning by integrating acceleration or speed, i.e. inertial navigation
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C21/00—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00
- G01C21/20—Instruments for performing navigational calculations
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C25/00—Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass
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Abstract
The invention discloses an indexing mechanism of a rotary strapdown inertial measurement unit (SIU) and an IMU synchronous calibration and compensation method, which greatly improve the calculation precision of carrier postures in the inertial measurement unit rotation process, and mainly comprises the following implementation steps: firstly, eliminating the influence of zero offset errors of a gyroscope and an accelerometer on an alignment result by using double-position alignment; secondly, the gesture tracking mode can avoid the influence of speed errors and position errors on gesture measurement; estimating the deflection angle and the asynchronous error of the rotating shaft by using a posture quaternion error model in the process of driving the indexing mechanism to rotate 180 degrees anticlockwise; after the error between the indexing mechanism and the IMU is calibrated, the calibration result is substituted into a posture conversion formula, and posture information of the IMU is converted into posture information of a carrier to complete the offset angle of a rotating shaft appointed by the indexing mechanism and the compensation of time asynchronous error between the indexing mechanism and the IMU.
Description
Technical Field
The invention belongs to the technical field of strapdown inertial navigation, and particularly relates to an indexing mechanism of a rotary strapdown inertial navigation unit and an IMU synchronous calibration and compensation method.
Background
A certain type of strapdown inertial measurement unit (hereinafter referred to as inertial measurement unit) consists of a biaxial-velocity indexing mechanism and an IMU, and the specific structure of the strapdown inertial measurement unit comprises: three 120 optical fiber gyroscopes, three quartz flexible accelerometers, a biaxial rate indexing mechanism, electronic circuits, software and the like.
The inertial measurement unit can be used for providing the attitude information, the speed information and the position information of the vehicle for the positioning and orientation system in real time, and has the functions of inertial measurement, self-alignment, self-calibration, self-detection, rotation modulation, course angle isolation and the like. The inertial measurement unit self-alignment adopts a two-position alignment technology, enters a rotation modulation navigation mode of course angle isolation after alignment, and requires that the optical fiber inertial measurement unit can provide high-precision attitude information, speed information and position information for a vehicle.
In the modulation navigation process, the indexing mechanism drives the IMU (inertial measurement unit) to circularly overturn, and the fact that the rotating shaft deflection angle exists due to the fact that the corresponding shaft of the indexing mechanism is not completely parallel to the corresponding shaft of the IMU coordinate system during processing and installation is considered, and meanwhile, the time asynchronous error exists between the indexing mechanism and the IMU, so that the accuracy of calculating the carrier posture in the inertial measurement unit rotation process is greatly affected.
Disclosure of Invention
Aiming at the problems that the rotation shaft deflection angle exists when the rotation strapdown inertial measurement unit is driven by the rotation position mechanism to circularly overturn the IMU, and the carrier gesture calculation precision is poor in the inertial measurement unit rotation process due to the asynchronous time error of the rotation position mechanism and the IMU, the invention provides a rotation position mechanism of the rotation strapdown inertial measurement unit and an IMU synchronous calibration and compensation method.
The basic implementation principle of the invention is as follows:
the attitude measurement method adopting the two-position alignment and attitude tracking modes comprises the following steps:
firstly, eliminating the influence of zero offset errors of a gyroscope and an accelerometer on an alignment result by using double-position alignment;
secondly, the gesture tracking mode can avoid the influence of speed errors and position errors on gesture measurement;
estimating the deflection angle and the asynchronous error of the rotating shaft by using a posture quaternion error model in the process of driving the indexing mechanism to rotate 180 degrees anticlockwise; after the error between the indexing mechanism and the IMU is calibrated, the calibration result is substituted into a posture conversion formula, and posture information of the IMU is converted into posture information of a carrier to complete the offset angle of a rotating shaft appointed by the indexing mechanism and the compensation of time asynchronous error between the indexing mechanism and the IMU.
The specific technical scheme of the invention is as follows:
an indexing mechanism of a rotary strapdown inertial measurement unit and an IMU synchronous calibration and compensation method comprise the following steps:
step 1: standing the inertial measurement unit on a horizontal table top, switching on a power supply, and recording that the positions of motors of all rotating shafts in the indexing mechanism are 0 degrees at the moment;
step 2: dual position alignment
Step 2.1: a first position alignment;
controlling the motor of the appointed rotating shaft of the indexing mechanism to rotate anticlockwise to a 180-degree position, starting alignment after the indexing mechanism is stable, and enabling the IMU to be stationary at the 180-degree position for a duration of t 1 Recording the alignment attitude angle of the first position inertial measurement unit as phi 1 ；
Step 2.2: a second position alignment;
controlling the motor of the appointed rotating shaft of the indexing mechanism to rotate clockwise to the 0-degree position, and starting alignment after the indexing mechanism is stable, wherein the IMU is stationary at the 0-degree position for a duration of t 2 ＝t 1 Recording the alignment attitude angle of the second position inertial measurement unit as phi 2 The inertial measurement unit always aligns the attitude angle phi of the first position inertial measurement unit in the rotation process and the stabilization process of the inertial measurement unit 1 Tracking the posture to obtain an updated alignment posture angle phi 1 '；
Step 3: will align the attitude angle phi 1 ' and phi 2 Respectively converted into gesture matrixAnd->Averaging the two matrixes to obtain a final posture matrix +.>Obtaining a corresponding attitude angle phi and an attitude quaternion from the matrix>
Step 4: the inertial measurement unit enters a gesture tracking mode to obtain a rotating shaft deflection angle of an indexing mechanism and an asynchronous error existing between the indexing mechanism and the IMU; the gesture tracking mode only carries out gesture updating in the strapdown inertial navigation recursion process, and does not carry out speed and position updating;
step 4.1: controlling a motor of a designated rotating shaft of the indexing mechanism to rotate anticlockwise to a 180-degree position, and recording N groups of data with equal angle intervals in the rotating process, wherein the N groups of data are gesture quaternions corresponding to each angle of the indexing mechanismi takes the values 1,2,3, …, N;
step 4.2: n groups of data obtained in the step 4.1And the gesture quaternion obtained in the step 3 +.>Substituting the attitude quaternion error model equation, solving the rotating shaft deflection angle of the motor of the rotating shaft appointed by the indexing mechanism and the time asynchronous error between the indexing mechanism and the IMU, and taking the time asynchronous error as a calibration result;
step 5: and (3) according to the calibration result of the step (4.2), converting the attitude quaternion of the IMU into the attitude quaternion of the inertial unit by utilizing an attitude conversion formula, thereby completing the offset angle of the appointed rotating shaft of the indexing mechanism and the compensation of the time asynchronous error between the indexing mechanism and the IMU.
Further, in step 4.2, the specific calculation formula of the attitude quaternion error model equation is:
wherein u is the rotation shaft deflection angle of the appointed rotation shaft of the indexing mechanism; alpha is the time asynchronous error between the indexing mechanism and the IMU; θ 1 And theta 2 And (3) sampling values of angles of two adjacent indexing mechanisms before and after the IMU sampling time, wherein tau is a sampling interval.
The beneficial effects of the invention are as follows:
the offset angle of the designated shaft of the indexing mechanism and the time asynchronous error between the indexing mechanism and the IMU are calibrated and compensated through the designated flow and algorithm, so that the calculation accuracy of the inertial measurement unit attitude information during rotation of the indexing mechanism can be improved, speed update and position update are not carried out in the navigation recursion process, and the influence of accelerometer errors on a calibration result is avoided.
Drawings
FIG. 1 is a schematic diagram of a related coordinate system;
FIG. 2 is a calibration workflow diagram.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the embodiments of the present invention disclosed herein will be described in further detail with reference to the accompanying drawings.
In the actual process, the double-shaft indexing mechanism is provided with an inner shaft and an outer shaft, the three-shaft indexing mechanism is provided with the inner shaft, the middle shaft and the outer shaft, and the designated rotating shaft of the indexing mechanism is approximately directed to the upward direction by adjusting the inertial measurement unit state, so that the rotation deflection angle of any designated rotating shaft in the indexing mechanism and the time asynchronous error of the indexing mechanism and the IMU can be obtained by the method.
As shown in FIG. 1, the IMU coordinate system is denoted as carrier coordinate system s (three coordinate axes in carrier coordinate system s are denoted as (Xs, ys, zs), and the IMU coordinate system with the indexing mechanism in the 0 position is taken as carrier coordinate system s 0 (Carrier coordinate System s) 0 The three coordinate axes are respectively marked as (Xs) 0 、Ys 0 ，Zs 0 ) In this embodiment, the inertial measurement unit is calibrated to obtain the specified rotation axis (and Zs 0 The axes approximately coincide), and the time out-of-sync error between the indexing mechanism and the IMU, the IMU sampling lag time is known to be between 0 and 10ms, the sampling interval is τ=10ms, and during the calibration process, the rest of the rotating shafts are all at 0 ° positions except the rotating shaft to be calibrated. The specific calibration compensation method is shown in fig. 2:
s1: standing the inertial measurement unit on a table top, upwards arranging a designated rotating shaft of the indexing mechanism, and switching on a power supply, wherein the motor position of each rotating shaft in the indexing mechanism is at a 0-degree position;
s2: controlling the motor of the appointed rotating shaft of the indexing mechanism to rotate anticlockwise to a 180-degree position, and starting an alignment process after the indexing mechanism is stable, wherein the resting time of the IMU at the 180-degree position is t 1 The first position inertial measurement unit is recorded to have an alignment attitude angle phi of 140s 1 ；
S3: the motor for controlling the appointed rotating shaft of the indexing mechanism rotates clockwise to the 0 DEG positionAfter the indexing mechanism is stable, the alignment is started, the IMU is stationary at the 0 DEG position, and the duration is t 2 ＝t 1 Recording the alignment attitude angle of the second position inertial measurement unit as phi 2 The inertial measurement unit always aligns the attitude angle phi of the first position inertial measurement unit in the rotation process and the stabilization process of the inertial measurement unit 1 Tracking the posture to obtain an updated alignment posture angle phi 1 '；
S4: alignment attitude angle phi of inertial measurement unit 1 ' and phi 2 Gesture matrix respectively converted into inertial groupsAnd->Averaging the two gesture matrixes to obtain a gesture matrix of the final inertial unit>From the gesture matrix->Obtaining the corresponding attitude angle phi and attitude quaternion +.>Then the inertial measurement unit enters a gesture tracking mode, and the gesture tracking mode only carries out gesture updating and does not carry out speed and position updating;
s5: the motor for driving the rotating shaft appointed by the indexing mechanism rotates anticlockwise to a 180-degree position, 10 groups of data with equal angle intervals in the rotating process are recorded, and the 10 groups of data are gesture quaternions corresponding to the motor of the rotating shaft appointed by the indexing mechanism in each anglei takes the values 1,2,3, …,10;
s6: 10 sets of data obtained in step S5The gesture obtained in step S4Quaternion->Substituting an attitude quaternion error model equation to solve a rotating shaft deflection angle u of a motor of a rotating shaft appointed by the indexing mechanism and a time asynchronous error alpha between the indexing mechanism and the IMU, and taking the error as a calibration result, wherein the specific form of the equation is as follows:
wherein θ i1 And theta i2 For the angle of the two adjacent indexing mechanisms before and after the IMU sampling time, if the lag time of the IMU information relative to the indexing mechanism is 0-10 ms, then theta i1 For last sampling indexing mechanism angle, θ i2 Indexing the angle of the mechanism for the current sampling; τ is the sampling interval, known as 0.01s.
S7: according to the calibration result, the attitude quaternion of the IMU is converted into the attitude quaternion of the inertial group by utilizing an attitude conversion formula during navigation, so that the offset angle of the angular axis of the indexing mechanism and the time asynchronous error between the indexing mechanism and the IMU are compensated.
Although the present invention has been described in terms of the preferred embodiments, it is not intended to be limited to the embodiments, and any person skilled in the art can make any possible variations and modifications to the technical solution of the present invention by using the methods and technical matters disclosed above without departing from the spirit and scope of the present invention, so any simple modifications, equivalent variations and modifications to the embodiments described above according to the technical matters of the present invention are within the scope of the technical matters of the present invention.
What is not described in detail in the present specification belongs to the known technology of those skilled in the art.
Claims (2)
1. The indexing mechanism of the rotary strapdown inertial measurement unit and the IMU synchronous calibration and compensation method are characterized by comprising the following steps:
step 1: standing the inertial measurement unit on a horizontal table top, switching on a power supply, and recording that the positions of motors of all rotating shafts in the indexing mechanism are 0 degrees at the moment;
step 2: dual position alignment
Step 2.1: a first position alignment;
controlling the motor of the appointed rotating shaft of the indexing mechanism to rotate anticlockwise to a 180-degree position, starting alignment after the indexing mechanism is stable, and enabling the IMU to be stationary at the 180-degree position for a duration of t 1 Recording the alignment attitude angle of the first position inertial measurement unit as phi 1 ；
Step 2.2: a second position alignment;
controlling the motor of the appointed rotating shaft of the indexing mechanism to rotate clockwise to the 0-degree position, and starting alignment after the indexing mechanism is stable, wherein the IMU is stationary at the 0-degree position for a duration of t 2 ＝t 1 Recording the alignment attitude angle of the second position inertial measurement unit as phi 2 The inertial measurement unit always aligns the attitude angle phi of the first position inertial measurement unit in the rotation process and the stabilization process of the inertial measurement unit 1 Tracking the posture to obtain an updated alignment posture angle phi 1 '；
Step 3: will align the attitude angle phi 1 ' and phi 2 Respectively converted into gesture matrixAnd->Averaging the two matrixes to obtain a final posture matrix +.>Obtaining a corresponding attitude angle phi and an attitude quaternion from the matrix>
Step 4: the inertial measurement unit enters a gesture tracking mode to obtain a rotating shaft deflection angle of an indexing mechanism and an asynchronous error existing between the indexing mechanism and the IMU; the gesture tracking mode only carries out gesture updating in the strapdown inertial navigation recursion process, and does not carry out speed and position updating;
step 4.1: controlling a motor of a designated rotating shaft of the indexing mechanism to rotate anticlockwise to a 180-degree position, and recording N groups of data with equal angle intervals in the rotating process, wherein the N groups of data are gesture quaternions corresponding to each angle of the indexing mechanismi takes the values 1,2,3, …, N;
step 4.2: n groups of data obtained in the step 4.1And the gesture quaternion obtained in the step 3 +.>Substituting the attitude quaternion error model equation, solving the rotating shaft deflection angle of the motor of the rotating shaft appointed by the indexing mechanism and the time asynchronous error between the indexing mechanism and the IMU, and taking the time asynchronous error as a calibration result;
step 5: and (3) according to the calibration result of the step (4.2), converting the attitude quaternion of the IMU into the attitude quaternion of the inertial unit by utilizing an attitude conversion formula, thereby completing the offset angle of the appointed rotating shaft of the indexing mechanism and the compensation of the time asynchronous error between the indexing mechanism and the IMU.
2. The method for synchronously calibrating and compensating the indexing mechanism and the IMU of the rotary strapdown inertial measurement unit (SIU) according to claim 1, wherein the method comprises the following steps: in step 4.2, the specific calculation formula of the attitude quaternion error model equation is as follows:
wherein u is the rotation shaft deflection angle of the appointed rotation shaft of the indexing mechanism; alpha is the time asynchronous error between the indexing mechanism and the IMU; θ 1 And theta 2 And (3) sampling values of angles of two adjacent indexing mechanisms before and after the IMU sampling time, wherein tau is a sampling interval.
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| CN107270938A (en) * | 2017-06-13 | 2017-10-20 | 西北工业大学 | Single-shaft-rotation inertial navigation system posture demodulation method based on Taylor series fitting |
| CN111878064A (en) * | 2020-05-11 | 2020-11-03 | 中国科学院地质与地球物理研究所 | Attitude measurement method |
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| US10317214B2 (en) * | 2016-10-25 | 2019-06-11 | Massachusetts Institute Of Technology | Inertial odometry with retroactive sensor calibration |
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| CN107270938A (en) * | 2017-06-13 | 2017-10-20 | 西北工业大学 | Single-shaft-rotation inertial navigation system posture demodulation method based on Taylor series fitting |
| CN111878064A (en) * | 2020-05-11 | 2020-11-03 | 中国科学院地质与地球物理研究所 | Attitude measurement method |
| WO2021227012A1 (en) * | 2020-05-11 | 2021-11-18 | 中国科学院地质与地球物理研究所 | Attitude measurement method |
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