CN111879335A - A centrifuge-based multi-position gyroscope drift coefficient calibration method - Google Patents

Abstract

The invention discloses a calibration method of a drift coefficient of a multi-position gyroscope based on a centrifugal machine, which comprises the following steps: establishing a coordinate system on a precision centrifuge with a reverse platform, analyzing error sources under each coordinate system, deducing accurate angular velocity input on each axis of a gyroscope by a homogeneous transformation method, giving a specific force input nominal value, and giving accurate calculation expressions of each drift coefficient according to a static error model of the gyroscope and the specific force input and the angular velocity input under the position of the gyroscope 16, so that error compensation can be performed on an identification result through the expressions, and calibration of the drift coefficient is realized.

Description

A centrifuge-based multi-position gyroscope drift coefficient calibration method

technical field

The invention belongs to the field of aerospace navigation, and specifically designs a centrifuge-based multi-position gyroscope drift coefficient calibration method.

Background technique

In order to accurately calibrate the drift coefficient of the gyroscope, a coordinate system was established on a precision centrifuge with a reversing platform, and the error sources under each coordinate system were analyzed. The nominal value of the specific force input is obtained, and then according to the static error model of the gyroscope and the specific force input and angular velocity input of the gyroscope 16 position, the precise calculation expression of each drift coefficient is given, so that the identification can be used through this set of expressions. The result is error-compensated. The experimental simulation shows that when the 16-position test method is used to calibrate the drift coefficient, the centrifuge error only has a relatively large influence on the D _I and D _OS , and has no effect on the calibration of other coefficients, indicating that this method can effectively avoid the centrifuge error. It is necessary to accurately measure the verticality error of the rotary axis of the inversion platform and the disk surface, the rotation error of the inclination angle of the rotary axis of the inversion platform, and the difference between the angular rate of the inversion platform and the angular rate of the main shaft, etc. to meet the calibration accuracy requirements.

SUMMARY OF THE INVENTION

In this paper, a simplified multi-position method for calibrating gyroscope parameters is proposed. The position stage is introduced, and the possible error sources of the centrifuge with reversing stage are analyzed. By establishing a coordinate system and applying the method of homogeneous transformation The precise expression of the angular velocity input, which has a great influence on the gyroscope calibration error, is deduced, and the input specific force expression of each axis of the gyroscope is given. The gyroscope output is obtained through a special position and combined with the derived angular velocity input, the specific force input expression and the gyroscope static error model, the expressions of various drift rate coefficients can be obtained, thereby improving the calibration accuracy through error compensation. .

Description of drawings

Figure 1 is a schematic diagram of a centrifuge with a reversing platform; Figure 2 is the attitude of each axis of the sixteen-position gyroscope.

Detailed ways

in:

为当地纬度。k ₁ =Δθ _y2t +Δθ _y2 (-ω); k ₂ =Δθ _x2t +Δθ _x2 (-ω); γ=ωt+γ ₀ , β=ωt, Δω is the magnitude of the reversal platform angular velocity and the main shaft angular velocity The difference, ω _e is the angular velocity of the earth's rotation,

is the local latitude.

The error of the centrifuge has an influence on the input ratio of each axis of the gyroscope, but considering that the drift coefficient of the gyroscope itself is very small, only the nominal value of the input of each axis of the gyroscope is considered here, and the rotating object is also considered to be affected by the gyroscope. The effect of acceleration is:

a _I =(-AA _k )cosγcosβ+sinβ (2)

a _O = -A sinγ (3)

a _S =(A+A _k )cosγsinβ+cosβ (4)

R₀为半径的标称值。Wherein, A=ω ² R ₀ /g;

_R0 is the nominal value of the radius.

The general form of the gyroscope static error model is:

In formula (5), ω _d is the angular rate equivalent output of the gyroscope, and the unit is °/h; a _I , a _O , and a _S are the specific forces along the input axis IA, output axis OA and rotation axis SA of the gyroscope, respectively. component; d _F is the zero offset, the unit is °/h; ω _I is the angular rate along the input axis of the gyroscope; d _I , d _O , d _S are the first-order drift rate coefficients, the unit is °/h/ g; d _II , d _OO , and d _SS are the quadratic drift rate coefficients, and the unit is °/h/g ² ; d _IO , d _IS , and d _OS are the cross-coupling drift rate coefficients, and the unit is °/h/g ² ; _σω is the residual error.

When calibrating the drift coefficient of the gyroscope under the 1g gravity field, the d _F , d _I , d _O , d _S and other coefficients can be calibrated usually by using 8 positions, but the premise is that the high-order drift coefficient is ignored. When the centrifuge shown in Figure 1 is used to calibrate various drift rate coefficients of the gyroscope, it is obviously impossible to calibrate all the drift coefficients by using the 8-position test method. A 16-position test method is given here, that is, when γ and β take 4 special angles respectively, 16 test positions are obtained through the combination of angles, and the output of the gyroscope is recorded at each position, and combined with the formula ( 1), (2), (3), (4), (5) 16 equations are obtained, and the expression of each drift coefficient can be obtained by solving the equation system.

Substitute the specific force input and input angular velocity value of each axis of the gyroscope at each position into formula (5) respectively, and 16 equations containing drift coefficients as unknowns can be obtained. By solving the equations, we get:

The drift coefficients d _I , d _O , d _S (°/h/g) caused by the input specific force of each axis and the drift coefficients d _IO , d _IS , d _OS caused by the product of the input specific force can be easily obtained by solving the equations. (°/h/g ² ), but the drift coefficients d _II , d _OO , d _SS (°/h/g ² due to the constant drift d _F (°/h) in the system of equations and the square of the input specific force ) is linearly correlated, that is, the system of equations is not full of rank, so the four parameters cannot be effectively separated. Based on this, the centrifuge provides two different centripetal accelerations, that is, the centrifuge is calibrated under the condition of two different rotational speeds ω and ω′, so that d _F , d _II , and d _OO can be effectively separated. , d _SS these four parameters. It can be obtained by calculation:

In the formula, A ₁ and A ₂ are used to distinguish two different centripetal accelerations provided by the centrifuge.

In this way, according to equations (6) to (15), all the gyroscope drift coefficients can be calibrated only by obtaining the output of the position of the gyroscope 16 at two rotational speeds.

Claims (2)

1. A calibration method for drift coefficients of a multi-position gyroscope based on a centrifugal machine adopts a system comprising the following steps: a centrifuge with a synchronous reverse speed platform and a high-precision positioning table;

characterized in that the method comprises: firstly, the centrifuge is integrally placed on a horizontal plane, and then the following steps are carried out:

(1) one side of the centrifuge is provided with a reverse platform, a rotatable positioning table is arranged on the reverse platform, a rotating shaft of the positioning table is a C shaft, the direction of the rotating shaft is parallel to the disk surface of the disk centrifuge, and the rotating shaft can perform 0-360 degrees to provide a posture required by calibrating the gyroscope; when the gyroscope is calibrated, the gyroscope is placed on the positioning table and fixedly mounted, the initial mounting direction is that SA is vertically upward, IA points to the center of a circle of the disk centrifuge along the radius direction of the disk centrifuge, and OA is vertical to the plane formed by SA and IA;

(2) the 16 positions are obtained as follows: the SA axis is vertically upward, and the OA axis and the IA axis rotate for 4 times at an interval angle of 90 degrees in a plane to obtain 4 angular positions; the SA axis is vertically downward, and the OA axis and the IA axis rotate for 4 times at an interval angle of 90 degrees in a plane to obtain 4 angular positions; the IA axis is vertically upward, and the OA axis and the SA axis rotate for 4 times at an interval angle of 90 degrees in a plane to obtain 4 angular positions; the IA axis is directed vertically downward and the OA, SA axes are rotated 4 times in a plane at 90 ° intervals, resulting in 4 angular positions.

2. The method of claim 1, wherein the calibration method comprises the steps of:

(1) when the centrifugal machine reverse rotation platform synchronously rotates reversely, the following test mode is adopted, firstly, the gyroscope input shaft points to and is vertical to the main shaft rotation axis, the main shaft rotates clockwise, and the reverse rotation platform rotates anticlockwise; then the azimuth axis rotates 180 degrees to lead the input shaft of the gyroscope to be back to the rotation axis of the main shaft, and the main shaft also rotates clockwise and anticlockwise;

(2) adjusting the level of the working base surface to meet the requirement that the error is less than 0.001 rad;

(3) the gyroscope is arranged on a working base surface, so that the rotation center of the rotor is overlapped with the azimuth axis of the centrifuge as much as possible, and the centering can be omitted during the synchronous reversal test of the reversal platform of the centrifuge, so that the centering operation is omitted;

(4) adjusting the input shaft of the gyroscope to align with the main shaft of the centrifuge, and meeting the requirement that the error is less than 0.001 rad;

(5) the included angle gamma between the big arm and the geographical north direction when the main shaft of the centrifuge is zero and the included angle between the gyroscope input shaft and the birdcage grating strip are measured

(6) Determining the size of the static radius, and calculating the static radius R according to the non-reversal working state of the reversal platform₀，R′₀To calculate the static radius value R of the birdcage reversal synchronous centrifuge test

(7) The C shafts are respectively arranged to rotate at 16 position angles as shown in figure 2, synchronous reverse rotation of the centrifuge main shaft and the reverse rotation platform main shaft is met during actual tests, and the position platform rotating shaft is locked. Data acquisition is carried out when the position table is at a certain angle each time, 16 groups of gyroscope output values can be obtained, the data acquisition real-time requirement is low in the mode, and the data acquisition precision can be met in the mode of acquiring data for multiple times and averaging. If the test has an acquisition system with high data acquisition capacity, simultaneous rotation of three shafts, namely a main shaft of the centrifuge, a main shaft of the inversion platform and a rotating shaft of the position table, can be considered, and high-speed data acquisition is carried out when the gyroscope meets 16 postures, so that the test efficiency is improved;

(8) giving the rotating speed omega of the main shaft of the centrifuge₁，ω₂，ω₃And the number of rotations N of azimuth axis₁，N₂，N₃And testing, collecting the output of the gyroscope at the rotating speed of each centrifuge main shaft, and recording the rotation angle position of the main shaft at the moment when the birdcage grating strips are triggered. Because the actual output of the gyroscope is reflected by adopting the pulse difference of the positive channel and the negative channel, the synchronous rotation of the reversal platform and the main shaft is ensured for the whole circle, and therefore, the zero position control timing of the birdcage grating is adopted. Acquiring the output quantity of the gyroscope at a corresponding position of the gyroscope, and recording related data;

(9) according to equations (6) to (15), all gyro drift coefficients can be calibrated by using the outputs of the positions of the gyroscopes 16 at three rotational speeds.

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