CN114166215A - Indexing mechanism of rotary strapdown inertial measurement unit and IMU synchronous calibration and compensation method - Google Patents
Indexing mechanism of rotary strapdown inertial measurement unit and IMU synchronous calibration and compensation method Download PDFInfo
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- CN114166215A CN114166215A CN202111376411.7A CN202111376411A CN114166215A CN 114166215 A CN114166215 A CN 114166215A CN 202111376411 A CN202111376411 A CN 202111376411A CN 114166215 A CN114166215 A CN 114166215A
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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 a synchronous calibration and compensation method for a transposition mechanism and an IMU (inertial measurement Unit) of a rotary strapdown inertial measurement unit, which greatly improves the calculation precision of the attitude of a carrier in the rotation process of the inertial measurement unit 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 attitude tracking mode can avoid the influence of speed errors and position errors on attitude measurement; estimating the deflection angle and the asynchronous error of the rotating shaft by utilizing an attitude 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 an attitude conversion formula, and the attitude information of the IMU is converted into the attitude information of the carrier to complete the compensation of the deflection angle of the specified rotating shaft of the indexing mechanism and the asynchronous time 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 a transposition mechanism of a rotary strapdown inertial unit and an IMU synchronous calibration and compensation method.
Background
A certain type of strapdown inertial measurement unit (hereinafter referred to as an inertial measurement unit) is composed of a double-shaft speed indexing mechanism and an IMU (inertial measurement Unit), and the specific structure of the strapdown inertial measurement unit comprises: three 120-type 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 attitude information, speed information and position information of a vehicle loader for a positioning and orienting 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 double-position alignment technology, enters a course angle isolated rotation modulation navigation mode after alignment, and requires that the optical fiber inertial measurement unit can provide high-precision attitude information, speed information and position information for the vehicle carrying vehicle.
In the modulation navigation process, the indexing mechanism drives an IMU (inertial measurement unit) to circularly turn, and the indexing mechanism is not completely parallel to a corresponding shaft of an IMU coordinate system during processing and installation, so that a rotating shaft deflection angle exists, and the indexing mechanism and the IMU have asynchronous time errors, so that the precision of carrier attitude calculation in the rotation process of the inertial measurement unit is greatly influenced.
Disclosure of Invention
The invention provides a transposition mechanism of a rotary strapdown inertial measurement unit and an IMU synchronous calibration and compensation method, aiming at the problems that a rotating shaft deflection angle exists when the transposition mechanism drives an IMU to circularly overturn, and the calculation precision of a carrier posture is poor in the rotation process of the inertial measurement unit due to the fact that time asynchronism errors exist between the transposition mechanism and the IMU.
The basic implementation principle of the invention is as follows:
the attitude measurement method adopting the double-position alignment and attitude tracking mode 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 attitude tracking mode can avoid the influence of speed errors and position errors on attitude measurement;
estimating the deflection angle and the asynchronous error of the rotating shaft by utilizing an attitude 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 an attitude conversion formula, and the attitude information of the IMU is converted into the attitude information of the carrier to complete the compensation of the deflection angle of the specified rotating shaft of the indexing mechanism and the asynchronous time error between the indexing mechanism and the IMU.
The specific technical scheme of the invention is as follows:
a synchronous calibration and compensation method for an indexing mechanism and an IMU (inertial measurement unit) of a rotary strapdown inertial measurement unit comprises the following steps:
step 1: standing the inertial measurement unit on a horizontal table board, switching on a power supply, and recording the positions of rotating shaft motors in the indexing mechanism to be 0 degree at the moment;
step 2: dual position alignment
Step 2.1: a first position alignment;
controlling the indexing mechanism to designate the motor of the rotating shaft to rotate anticlockwise to a 180-degree position, after the indexing mechanism is stabilized, starting alignment, enabling the IMU to be static at the 180-degree position, and keeping the duration t1Recording the first position inertia alignment attitude angle as phi1；
Step 2.2: the second position is aligned;
controlling the indexing mechanism to designate the motor of the rotating shaft to rotate clockwise to a 0-degree position, after the indexing mechanism is stabilized, starting alignment, enabling the IMU to be static at the 0-degree position for a duration of t2＝t1Recording the second position inertia alignment attitude angle as phi2Aligning the attitude angle phi to the first position inertial set all the time in the rotation process and the stabilization process of the inertial set1Performing attitude tracking to obtain updated alignment attitude angle phi1'；
And step 3: will align the attitude angle phi1' and phi2Respectively converted into attitude matrix
And
averaging the two matrixes to obtain a final attitude matrix
Obtaining corresponding attitude angle phi and attitude quaternion from the matrix
And 4, step 4: the inertial measurement unit enters an attitude tracking mode to obtain a rotating shaft deflection angle of the indexing mechanism and asynchronous errors existing between the indexing mechanism and the IMU; the attitude tracking mode is only used for updating the attitude and is not used for updating the speed and the position in the navigation recursion process of the strapdown inertial measurement unit;
step 4.1: controlling the indexing mechanism to designate the motor of the rotating shaft to rotate anticlockwise to a position of 180 degrees, and recording N groups of data at equal angle intervals in the rotating process, wherein the N groups of data are attitude quaternions corresponding to the indexing mechanism at each angle
i takes the values 1, 2, 3, …, N; (ii) a
Step 42: the N groups of data obtained in step 4.1 are combined
And the attitude quaternion obtained in step 3
Substituting the attitude quaternion error model equation, solving a rotating shaft deflection angle of a motor of a specified rotating shaft of the indexing mechanism and a time asynchronous error between the indexing mechanism and the IMU, and taking the time asynchronous error as a calibration result;
and 5: and 4.2, converting the attitude quaternion of the IMU into the attitude quaternion of the inertial measurement unit by utilizing an attitude conversion formula according to the calibration result of the step 4.2, thereby completing the compensation of the deviation angle of the specified rotating shaft of the indexing mechanism and the time asynchronous error between the indexing mechanism and the IMU.
Further, the specific calculation formula in step 4.3 is as follows:
wherein u is a rotating shaft deflection angle of a specified rotating shaft of the indexing mechanism; alpha is the asynchronous error of time between the indexing mechanism and the IMU; theta1And theta2And (4) angle sampling values of two adjacent indexing mechanisms before and after IMU sampling time, wherein tau is a sampling interval.
The invention has the beneficial effects that:
the drift 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, the calculation precision of the inertial measurement unit attitude information during rotation of the indexing mechanism can be improved, speed updating and position updating are not performed in the navigation recursion process, and the influence of the accelerometer error on the calibration result is avoided.
Drawings
FIG. 1 is a schematic diagram of a relational coordinate system;
FIG. 2 is a calibration workflow diagram.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the embodiments of the present invention will be described in detail with reference to the accompanying drawings.
In the practical 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 appointed rotating shaft of the indexing mechanism approximately points to the sky direction by adjusting the inertial group state, so that the rotating deflection angle of the arbitrarily appointed 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 referred to as a carrier coordinate system s (three coordinate axes in the carrier coordinate system s are referred to as (Xs, Ys, Zs), respectively), and the IMU coordinate system at the 0 ° position of the indexing mechanism is referred to as the carrier coordinate system s0(Carrier coordinate System s)0The three coordinate axes are respectively marked as (Xs)0、Ys0，Zs0) In this embodiment, the inertial set needs to be calibrated to obtain the designated axis of rotation (and Zs) in the indexing mechanism0The axes approximately coincident) and the time out-of-sync error between the indexing mechanism and the IMU, which is known to be an IMUThe sampling lag time is between 0ms and 10ms, the sampling interval is tau which is 10ms, and in the calibration process, except the rotating shaft to be calibrated, the other rotating shafts are all at the position of 0 degree. The specific calibration compensation method is shown in fig. 2:
s1: standing the inertial unit on the table board, enabling the appointed rotating shaft of the indexing mechanism to face upwards, 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 indexing mechanism to designate the motor of the rotating shaft to rotate anticlockwise to a 180-degree position, starting an alignment process after the indexing mechanism is stable, and enabling the IMU to be stationary at the 180-degree position for t1140s, and recording the first position inertia alignment attitude angle as phi1；
S3: controlling the indexing mechanism to designate the motor of the rotating shaft to rotate clockwise to a 0-degree position, after the indexing mechanism is stabilized, starting alignment, enabling the IMU to be static at the 0-degree position for a duration of t2＝t1Recording the second position inertia alignment attitude angle as phi2Aligning the attitude angle phi to the first position inertial set all the time in the rotation process and the stabilization process of the inertial set1Performing attitude tracking to obtain updated alignment attitude angle phi1'；
S4: aligning attitude angle phi of inertial measurement unit1' and phi2Attitude matrix respectively converted into inertial set
And
averaging the two attitude matrices to obtain the attitude matrix of the final inertial measurement unit
From the attitude matrix
Obtaining corresponding attitude angle phi and attitude quaternion
Subsequently, the inertial measurement unit enters a posture tracking modeThe attitude tracking mode only updates the attitude and does not update the speed and the position;
s5: the motor for driving the designated rotating shaft of the indexing mechanism rotates anticlockwise to a position of 180 degrees, 10 groups of data at medium angle intervals in the rotating process are recorded, and the 10 groups of data are attitude quaternions corresponding to the motor for the designated rotating shaft of the indexing mechanism at each angle
i takes values of 1, 2, 3, …, 10;
s6: the 10 sets of data obtained in step S5
And the attitude quaternion obtained in step S4
Substituting into the attitude quaternion error model equation, solving the rotating shaft deflection angle u of the motor of the appointed rotating shaft of the indexing mechanism and the time asynchronous error alpha between the indexing mechanism and the IMU, and taking the time asynchronous error alpha as a calibration result, wherein the specific form of the equation is as follows:
wherein, thetai1And thetai2The angle of the indexing mechanism is two times of adjacent before and after IMU sampling time, in the example, if the lag time of the IMU information relative to the indexing mechanism is known to be 0-10 ms, thetai1For last sampling of indexing mechanism angle, thetai2The angle of the sampling indexing mechanism is the angle of the sampling indexing mechanism; τ is the sampling interval, known as 0.01 s.
S7: and according to the calibration result, converting the attitude quaternion of the IMU into the attitude quaternion of the inertial set by using an attitude conversion formula during navigation, thereby completing the compensation of the drift angle of the indexing mechanism in the vertical axis and the time asynchronous error between the indexing mechanism and the IMU.
Although the present invention has been described with reference to the preferred embodiments, it is not intended to limit the present invention, and those skilled in the art can make variations and modifications of the present invention without departing from the spirit and scope of the present invention by using the methods and technical contents disclosed above.
Those skilled in the art will appreciate that the invention may be practiced without these specific details.
Claims (2)
1. A synchronous calibration and compensation method for an indexing mechanism and an IMU (inertial measurement unit) of a rotary strapdown inertial measurement unit is characterized by comprising the following steps:
step 1: standing the inertial measurement unit on a horizontal table board, switching on a power supply, and recording the positions of rotating shaft motors in the indexing mechanism to be 0 degree at the moment;
step 2: dual position alignment
Step 2.1: a first position alignment;
controlling the indexing mechanism to designate the motor of the rotating shaft to rotate anticlockwise to a 180-degree position, after the indexing mechanism is stabilized, starting alignment, enabling the IMU to be static at the 180-degree position, and keeping the duration t1Recording the first position inertia alignment attitude angle as phi1；
Step 2.2: the second position is aligned;
controlling the indexing mechanism to designate the motor of the rotating shaft to rotate clockwise to a 0-degree position, after the indexing mechanism is stabilized, starting alignment, enabling the IMU to be static at the 0-degree position for a duration of t2＝t1Recording the second position inertia alignment attitude angle as phi2Aligning the attitude angle phi to the first position inertial set all the time in the rotation process and the stabilization process of the inertial set1Performing attitude tracking to obtain updated alignment attitude angle phi1'；
And step 3: will align the attitude angle phi1' and phi2Respectively converted into attitude matrix
And
averaging the two matrixes to obtain a final attitude matrix
Obtaining corresponding attitude angle phi and attitude quaternion from the matrix
And 4, step 4: the inertial measurement unit enters an attitude tracking mode to obtain a rotating shaft deflection angle of the indexing mechanism and asynchronous errors existing between the indexing mechanism and the IMU; the attitude tracking mode is only used for updating the attitude and is not used for updating the speed and the position in the navigation recursion process of the strapdown inertial measurement unit;
step 4.1: controlling the indexing mechanism to designate the motor of the rotating shaft to rotate anticlockwise to a position of 180 degrees, and recording N groups of data at equal angle intervals in the rotating process, wherein the N groups of data are attitude quaternions corresponding to the indexing mechanism at each angle
i takes the values 1, 2, 3, …, N; (ii) a
Step 42: the N groups of data obtained in step 4.1 are combined
And the attitude quaternion obtained in step 3
Substituting the attitude quaternion error model equation, solving a rotating shaft deflection angle of a motor of a specified rotating shaft of the indexing mechanism and a time asynchronous error between the indexing mechanism and the IMU, and taking the time asynchronous error as a calibration result;
and 5: and 4.2, converting the attitude quaternion of the IMU into the attitude quaternion of the inertial measurement unit by utilizing an attitude conversion formula according to the calibration result of the step 4.2, thereby completing the compensation of the deviation angle of the specified rotating shaft of the indexing mechanism and the time asynchronous error between the indexing mechanism and the IMU.
2. The indexing mechanism and IMU synchronous calibration and compensation method of the rotary strapdown inertial measurement unit according to claim 1, wherein: the specific calculation formula in the step 4.3 is as follows:
wherein u is a rotating shaft deflection angle of a specified rotating shaft of the indexing mechanism; alpha is the asynchronous error of time between the indexing mechanism and the IMU; theta1And theta2And (4) angle sampling values of two adjacent indexing mechanisms before and after IMU sampling time, wherein tau is a sampling interval.
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| US20180231385A1 (en) * | 2016-10-25 | 2018-08-16 | Massachusetts Institute Of Technology | Inertial Odometry With Retroactive Sensor Calibration |
| 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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| US20090164067A1 (en) * | 2003-03-20 | 2009-06-25 | Whitehead Michael L | Multiple-antenna gnss control system and method |
| US20180231385A1 (en) * | 2016-10-25 | 2018-08-16 | Massachusetts Institute Of Technology | Inertial Odometry With Retroactive Sensor Calibration |
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| 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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