CN101672649B - Mooring alignment method of optical fiber strapdown system for ship based on digital low-pass filtering - Google Patents

Abstract

The invention provides a mooring alignment method of an optical fiber strapdown system for a ship based on digital low-pass filtering. The method comprises the following steps: determining parameters of the initial position of a carrier through a GPS; collecting the output of an optical fiber gyroscope and data output by an accelerometer and processing the data; converting the output of the optical fiber gyroscope and the accelerometer into a base inertial coordinate system; designing a reasonable low-pass digital filter according to the frequency feature of the output of the gyroscope and the accelerometer under the base inertial system and filtering the disturbance angular velocity and the disturbance acceleration in the base inertial system; amending angular velocity information after the low-pass filtering treatment by utilizing a weighted averaging filtering algorithm and filtering small-amplitude ripples; and utilizing the projection formed by the angular velocity and the acceleration information after the filtering, as well as the angular velocity of rotation and the gravity acceleration of the earth on a navigation coordinate system for establishing a matrix and completing the initial alignment of the system. The adoption of the method can obtain higher alignment precision within a shorter period of time when the carrier is in the mooring state.

Description

A kind of optical fiber strapdown system for ship mooring alignment methods based on digital low-pass filtering

(1) technical field

What the present invention relates to is a kind of measuring method, in particular a kind of optical fiber strapdown system for ship mooring alignment methods based on digital low-pass filtering.

(2) background technology

Inertial navigation system is an a kind of self-aid navigation system, it is without any need for artificial external information, as long as the starting condition (initial velocity, position etc.) of given navigation, just specific force and the angular velocity that can measure according to the inertia device in the system, by computer real-time calculate various navigational parameters.Strapdown inertial navigation system (SINS) is connected in inertance elements such as gyroscope, accelerometer on the carrier, according to Newton mechanics law, by the information of these inertance element collections is handled, obtain the complete independent navigation equipment of the full navigation information such as attitude, speed, position, acceleration, angular velocity and angular acceleration of carrier.Because that it has is in light weight, reliability is high, be convenient to safeguard, round-the-clock and complete advantage such as autonomous obtains application more and more widely.

According to the ultimate principle of SINS, SINS needs to obtain initial information before entering navigational state, comprises initial position, speed and attitude.Wherein the precision of initial attitude is exactly the initial alignment precision of SINS when entering navigational state, therefore must at first finish determining of initial attitude before strapdown inertial navitation system (SINS) enters navigational state.Because " platform " is the benchmark of measuring specific force, therefore the initial alignment of " platform " is just extremely important; The strapdown matrix plays the effect of mathematical platform in strapdown inertial navigation system.Therefore the critical problem of initial alignment is exactly the initial value of trying to achieve initial strapdown matrix in the short period of time with certain precision.

Initial alignment can be not rely on outside autonomous type, also can be the controlled formula that relies on some external unit, the method that also can adopt autonomous type and controlled formula to combine sometimes.According to the motion state of different pedestals, initial alignment can be divided into static-base alignment and moving alignment again.Moving alignment is meant motor-driven or exist under the condition of external disturbance at carrier, and strapdown inertial navigation system is finished initial alignment.Moving alignment usually needs external information, the state variable of system is estimated, and carried out the attitude correction after filtering is stable.

The requirement of initial alignment generally comprises precision and rapidity two aspects.In order to satisfy high-precision requirement, wish that inertial sensor has high as far as possible precision and stability, and it is insensitive to wish that system can disturb to external world, promptly the robustness of system will be got well; In order to improve precision, can measure and compensate gyroscopic drift, the accelerometer error of zero and their scaling ratio when also wishing initial alignment.The realization of obvious above-mentioned measure needs big, the fireballing computing machine of capacity to give to guarantee, clearly, the requirement of this two aspect of precision and rapidity is conflicting, therefore will reasonably carry out Control System Design, take into account the requirement of this two aspect as far as possible, in the hope of trying to achieve satisfactory result.

(3) summary of the invention

The object of the present invention is to provide a kind of interference that can isolate the external world effectively, reach a kind of optical fiber strapdown system for ship mooring alignment methods of alignment precision preferably in the short period of time based on digital low-pass filtering.

The object of the present invention is achieved like this: a kind of optical fiber strapdown system for ship mooring alignment methods based on digital low-pass filtering, utilize IIR wave digital lowpass filter and weighting to ask the average filter algorithm that angular velocity under the pedestal inertial coordinates system and acceleration information are handled, utilize the rotational-angular velocity of the earth and the acceleration of gravity information that obtain after the filtering, and its coordinate transformation relation between the projection that navigation coordinate is fastened calculates attitude matrix, realize the initial alignment of inertial navigation system, its concrete steps are as follows:

(1) determines the initial position parameters of carrier by GPS, they are bound to navigational computer;

(2) strapdown inertial navitation system (SINS) is carried out the preheating preparation, gathers the data of fibre optic gyroscope and quartz accelerometer output;

(3) fibre optic gyroscope that collects and the data of quartz accelerometer are carried out coordinate conversion, be transformed under the pedestal inertial coordinates system;

(4) the frequency characteristic output according to gyroscope and accelerometer designs lowpass digital filter, with Mach angle speed under the pedestal inertial system and disturbance acceleration filtering;

(5) angular velocity information after the low-pass filtering treatment is utilized weighting ask the average filter algorithm to revise, filtering is ripple by a small margin;

(6) make up the strapdown matrix according to rotational-angular velocity of the earth and acceleration of gravity, finish the initial alignment of inertial navigation system.

The present invention can also comprise:

1, described data-switching with fibre optic gyroscope and quartz accelerometer specifically comprises the steps: to the pedestal inertial coordinates system

Be the transition matrix between pedestal inertial coordinates system and the carrier coordinate system,, utilize the hypercomplex number method matrix according to gyrostatic output

Carry out real-time update, for the computing of following one-period provides parameter;

Strapdown inertial navitation system (SINS) under the swinging condition comprises the rotational-angular velocity of the earth ω that the cycle changes in the gyroscope output _Ie ^b, the kinetic angular velocity omega of carrier line _En ^b, wave the angular velocity omega that causes _Nb ^bWith gyroscope constant value drift ε,

That is:

${\mathrm{\ω}}_{\mathrm{ib}}^b={\mathrm{\ω}}_{\mathrm{ie}}^b+{\mathrm{\ω}}_{\mathrm{en}}^b+{\mathrm{\ω}}_{\mathrm{nb}}^b+\mathrm{\ϵ}$

Gyroscope output is expressed as in the pedestal inertial system:

${\mathrm{\&omega;}}_{\mathrm{ib}}^{i_{\mathrm{<figure-callout\; id="0"\; label="b"\; filenames="H2009100730728E00021.png,H2009100730728E00022.png"\; state="\{\{state\}\}">b</figure-callout>}0}}=T_b^{i_{\mathrm{<figure-callout\; id="0"\; label="b"\; filenames="H2009100730728E00021.png,H2009100730728E00022.png"\; state="\{\{state\}\}">b</figure-callout>}0}}{\mathrm{\&omega;}}_{\mathrm{ib}}^b={\mathrm{\&omega;}}_{\mathrm{ie}}^{i_{\mathrm{<figure-callout\; id="0"\; label="b"\; filenames="H2009100730728E00021.png,H2009100730728E00022.png"\; state="\{\{state\}\}">b</figure-callout>}0}}+{\mathrm{\&omega;}}_{\mathrm{en}}^{i_{\mathrm{<figure-callout\; id="0"\; label="b"\; filenames="H2009100730728E00021.png,H2009100730728E00022.png"\; state="\{\{state\}\}">b</figure-callout>}0}}+{\mathrm{\&omega;}}_{\mathrm{nb}}^{i_{\mathrm{<figure-callout\; id="0"\; label="b"\; filenames="H2009100730728E00021.png,H2009100730728E00022.png"\; state="\{\{state\}\}">b</figure-callout>}0}}+T_b^{i_{\mathrm{<figure-callout\; id="0"\; label="b"\; filenames="H2009100730728E00021.png,H2009100730728E00022.png"\; state="\{\{state\}\}">b</figure-callout>}0}}\mathrm{\&epsiv;}$

Wherein,

Be normal value, under the moored condition

Be zero, extract that the main distracter of rotational-angular velocity of the earth is under the pedestal inertial system this moment

Because waving of carrier comprises gravity acceleration g in the accelerometer output ^b, wave the disturbing acceleration δ a that causes ^bWith the accelerometer error of zero

That is:

$f^b=-g^b+\mathrm{\&delta;}{a}^b+\&dtri;$

Because inertia device deviation and the influence of swinging motion cause having disturbing acceleration information in the projection of output under the pedestal inertial system of accelerometer

The output of accelerometer is transformed in the pedestal inertial system and is expressed as:

$f^{i_{\mathrm{<figure-callout\; id="0"\; label="b"\; filenames="H2009100730728E00021.png,H2009100730728E00022.png"\; state="\{\{state\}\}">b</figure-callout>}0}}=T_b^{i_{b0}}{f}^b=-g^{i_{\mathrm{<figure-callout\; id="0"\; label="b"\; filenames="H2009100730728E00021.png,H2009100730728E00022.png"\; state="\{\{state\}\}">b</figure-callout>}0}}+\mathrm{\&delta;}{a}^{i_{\mathrm{<figure-callout\; id="0"\; label="b"\; filenames="H2009100730728E00021.png,H2009100730728E00022.png"\; state="\{\{state\}\}">b</figure-callout>}0}}+T_b^{i_{\mathrm{<figure-callout\; id="0"\; label="b"\; filenames="H2009100730728E00021.png,H2009100730728E00022.png"\; state="\{\{state\}\}">b</figure-callout>}0}}\&dtri;.$

2, the transitional zone of described design filtering gyro signal and accelerometer signal wave filter is respectively [0.001Hz, 0.01Hz], [0.01Hz, 0.02Hz], takes low-pass filtering technique to the gyroscope information under the inertial system

And acceleration information Handle, the filtering carrier obtains pure relatively rotational-angular velocity of the earth owing to wave and swing the disturbance angle velocity and the acceleration of motion generation

And acceleration of gravity

3, described weighting asks the average filter algorithm to be: known equidistant sampled point x ₀＜x ₁＜...＜x _N-1＜... on observation data be y ₀, y ₁..., y _N-1, y _iExpression y _iSmooth value, getting weighting coefficient is 1, get 400 seconds to 600 seconds data after the low-pass filtering do once level and smooth, then:

${\stackrel{\&OverBar;}{y}}_i=\frac{y_{i-n}+y_{i-n+1}+\&CenterDot;\&CenterDot;\&CenterDot;+y_0+{\mathrm{<figure-callout\; id="1"\; label="y"\; filenames="H2009100730728E00021.png,H2009100730728E00022.png"\; state="\{\{state\}\}">y</figure-callout>}}_1+\&CenterDot;\&CenterDot;\&CenterDot;+y_{i+n-2}+y_{i+n-1}}{n};$

4, described according to rotational-angular velocity of the earth and acceleration of gravity structure strapdown matrix, the method for finishing the initial alignment of inertial navigation system is:

Utilize rotational-angular velocity of the earth ω _IeThe projection of fastening at navigation coordinate with gravity acceleration g, and their coordinate transformation relations between the projection that the pedestal inertial coordinate is fastened calculate attitude matrix

$T_{i_{b0}}^n={\left[\begin{array}{c}{\left(g^n\right)}^T\\ {(g^n\&times;{\mathrm{\&omega;}}_{\mathrm{ie}}^n)}^T\\ {((g^n\&times;{\mathrm{\&omega;}}_{\mathrm{ie}}^n)\&times;g^n)}^T\end{array}\right]}^{-1}\left[\begin{array}{c}{\left(g^{i_{b0}}\right)}^T\\ {({\mathrm{<figure-callout\; id="0"\; label="g\; i\; b"\; filenames="H2009100730728E00021.png,H2009100730728E00022.png"\; state="\{\{state\}\}">g</figure-callout>}}^{i_b}\&times;{\mathrm{\&omega;}}_{\mathrm{ie}}^{i_{b0}})}^T\\ {((g^{i_{\mathrm{<figure-callout\; id="0"\; label="b"\; filenames="H2009100730728E00021.png,H2009100730728E00022.png"\; state="\{\{state\}\}">b</figure-callout>}0}}\&times;{\mathrm{\&omega;}}_{\mathrm{ie}}^{i_{b0}})\&times;g^{i_{b0}})}^T\end{array}\right]$

Obtain

Substitution $T_b^n=T_{i_{b0}}^n{T}_{\mathrm{<figure-callout\; id="0"\; label="b\; i\; b"\; filenames="H2009100730728E00021.png,H2009100730728E00022.png"\; state="\{\{state\}\}">b</figure-callout>}}^{i_b},$ Calculate T _b ⁿFinish the initial alignment of inertial navigation system.

The present invention's advantage compared with prior art is: the present invention has broken under the naval vessel moored condition, since the interference of waving and swinging motion cause tradition navigation system down analytical method can't be suitable for this problem, utilize inertial system to aim at this characteristic of alignment issues that is applicable under the resolved vector dynamic environment, proposed in strapdown inertial navitation system (SINS), to adopt the method that inertial system is aimed at of resolving.Owing to adopted angular velocity and acceleration information under the low-pass filtering treatment pedestal inertial system, therefore can isolate extraneous interference effectively, reach alignment precision preferably in the short period of time.

The effect useful to the present invention is described as follows:

Under the Matlab simulated conditions, this method is carried out emulation experiment:

Carrier is done the three-axis swinging motion.Carrier waves around pitch axis, axis of roll and course axle with sinusoidal rule, and its mathematical model is:

$\left\{\begin{array}{c}\mathrm{\&theta;}={\mathrm{\&theta;}}_m\sin ({\mathrm{\&omega;}}_{\mathrm{\&theta;}}t+{\mathrm{\&phi;}}_{\mathrm{\&theta;}})\\ \mathrm{\&gamma;}={\mathrm{\&gamma;}}_m\sin ({\mathrm{\&omega;}}_{\mathrm{\&gamma;}}t+{\mathrm{\&phi;}}_{\mathrm{\&gamma;}})\\ \mathrm{\&psi;}={\mathrm{\&psi;}}_m\sin ({\mathrm{\&omega;}}_{\mathrm{\&psi;}}t+{\mathrm{\&phi;}}_{\mathrm{\&psi;}})+k\end{array}\right.$

Wherein: θ, γ, ψ represent the angle variables of waving of pitch angle, roll angle and course angle respectively; θ _m, γ _m, ψ _mThe angle amplitude is waved in expression accordingly respectively; ω _θ, ω _γ, ω _ψRepresent corresponding angle of oscillation frequency respectively; φ _θ, φ _γ, φ _ψRepresent corresponding initial phase respectively; ω _i=2 π/T _i, i=θ, γ, ψ, T _iRepresent corresponding rolling period, k is the angle, initial heading.Get during emulation: θ _m=6 °, γ _m=12 °, ψ _m=10 °, T _θ=8s, T _γ=10s, T _ψ=6s, k=0 °.

The swaying of carrier, surging and hang down and swing the linear velocity that causes and be:

In the formula, i=x, y, z be geographic coordinate system east orientation, north orientation, day to. $A_{D_x}=0.02m,$ $A_{D_y}=0.03m,$ $A_{D_z}=0.3m;$ $T_{D_x}=7s,$ $T_{D_y}=6s,$ $T_{D_z}=8s;$

For going up, [0,2 π] obey equally distributed random phase.

Carrier initial position: 45.7796 ° of north latitude, 126.6705 ° of east longitudes;

The initial attitude error angle: three initial attitude error angles are zero;

Equatorial radius: R _e=6378393.0m;

Ellipsoid degree: e=3.367e-3;

The earth surface acceleration of gravity that can get by universal gravitation: g ₀=9.78049;

Rotational-angular velocity of the earth (radian per second): 7.2921158e-5;

The gyroscope constant value drift: 0.01 degree/hour;

The gyroscope random walk: 0.001 degree/

Accelerometer bias: 10 ^-4g ₀

Accelerometer noise: 10 ^-6g ₀

Constant: π=3.1415926;

Utilize method of the present invention to obtain carrier misalignment curve under the moored condition, respectively as Fig. 9, Figure 10, shown in Figure 11.The result shows and waves under the disturbed condition, adopts the inventive method can obtain higher coarse alignment precision.

(4) description of drawings

Fig. 1 is a kind of optical fiber strapdown system for ship mooring alignment methods process flow diagram based on digital low-pass filtering of the present invention;

Fig. 2 obtains flow process for pedestal inertial system rotational-angular velocity of the earth of the present invention and acceleration of gravity;

Fig. 3 is the angular velocity information on the different phase x direction of principal axis of the present invention;

Fig. 4 is the angular velocity information on the different phase y direction of principal axis of the present invention;

Fig. 5 is the angular velocity information on the different phase z direction of principal axis of the present invention;

Fig. 6 is the acceleration information on the different phase x direction of principal axis of the present invention;

Fig. 7 is the acceleration information on the different phase y direction of principal axis of the present invention;

Fig. 8 is the acceleration information on the different phase z direction of principal axis of the present invention;

Fig. 9 is the horizontal misalignment of east orientation of the present invention;

Figure 10 is the horizontal misalignment of north orientation of the present invention;

Figure 11 is that sky of the present invention is to the orientation misalignment;

(5) embodiment

Below in conjunction with accompanying drawing the specific embodiment of the present invention is described in detail:

(1) determines the initial position parameters of carrier by GPS, they are bound to navigational computer;

(2) strapdown inertial navitation system (SINS) is carried out the preheating preparation, gathers the data of fibre optic gyroscope and quartz accelerometer output;

(3) fibre optic gyroscope that collects and the data of quartz accelerometer are carried out coordinate conversion, be transformed under the pedestal inertial coordinates system;

Be the transition matrix between pedestal inertial coordinates system and the carrier coordinate system,, utilize the hypercomplex number method matrix according to gyrostatic output

Carry out real-time update, for the computing of following one-period provides parameter.

Strapdown inertial navitation system (SINS) under the swinging condition comprises the rotational-angular velocity of the earth ω that the cycle changes in the gyroscope output _Ie ^b, the kinetic angular velocity omega of carrier line _En ^b, wave the angular velocity omega that causes _Nb ^bWith gyroscope constant value drift ε.

${\mathrm{\&omega;}}_{\mathrm{ib}}^b={\mathrm{\&omega;}}_{\mathrm{ie}}^b+{\mathrm{\&omega;}}_{\mathrm{en}}^b+{\mathrm{\&omega;}}_{\mathrm{nb}}^b+\mathrm{\&epsiv;}---\left(1\right)$

Gyroscope output is expressed as in the pedestal inertial system:

${\mathrm{\&omega;}}_{\mathrm{ib}}^{i_{b0}}=T_{\mathrm{<figure-callout\; id="0"\; label="b\; i\; b"\; filenames="H2009100730728E00021.png,H2009100730728E00022.png"\; state="\{\{state\}\}">b</figure-callout>}}^{i_b}{\mathrm{\&omega;}}_{\mathrm{ib}}^b={\mathrm{\&omega;}}_{\mathrm{ie}}^{i_{\mathrm{<figure-callout\; id="0"\; label="b"\; filenames="H2009100730728E00021.png,H2009100730728E00022.png"\; state="\{\{state\}\}">b</figure-callout>}0}}+{\mathrm{\&omega;}}_{\mathrm{en}}^{i_{\mathrm{<figure-callout\; id="0"\; label="b"\; filenames="H2009100730728E00021.png,H2009100730728E00022.png"\; state="\{\{state\}\}">b</figure-callout>}0}}+{\mathrm{\&omega;}}_{\mathrm{nb}}^{i_{b0}}+T_{\mathrm{<figure-callout\; id="0"\; label="b\; i\; b"\; filenames="H2009100730728E00021.png,H2009100730728E00022.png"\; state="\{\{state\}\}">b</figure-callout>}}^{i_b}\mathrm{\&epsiv;}---\left(2\right)$

Wherein,

Be normal value, under the moored condition Be zero, extract that the main distracter of rotational-angular velocity of the earth is under the pedestal inertial system this moment

Because waving of carrier can obtain comprising gravity acceleration g in the accelerometer output equally ^b, wave the disturbing acceleration δ a that causes ^bWith the accelerometer error of zero

$f^b=-g^b+\mathrm{\&delta;}{a}^b+\&dtri;---\left(3\right)$

Theoretically, because gyroscope and accelerometer are connected in the same framework, ignore its lever arm influence and have good synchronism.When therefore the output of accelerometer process coordinate conversion is to the pedestal inertial system, can separates effectively and wave the disturbing acceleration that causes, obtain pure acceleration of gravity information.In real system, because the inertia device deviation and the influence of swinging motion cause having disturbing acceleration information in the projection of output under the pedestal inertial system of accelerometer

Therefore the output of accelerometer is transformed in the pedestal inertial system and is expressed as:

$f^{i_{b0}}=T_b^{i_{b0}}{f}^b=-{\mathrm{<figure-callout\; id="0"\; label="g\; i\; b"\; filenames="H2009100730728E00021.png,H2009100730728E00022.png"\; state="\{\{state\}\}">g</figure-callout>}}^{i_b}+\mathrm{\&delta;}{a}^{{\mathrm{<figure-callout\; id="0"\; label="i\; b"\; filenames="H2009100730728E00021.png,H2009100730728E00022.png"\; state="\{\{state\}\}">i</figure-callout>}}_b}+T_{\mathrm{<figure-callout\; id="0"\; label="b\; i\; b"\; filenames="H2009100730728E00021.png,H2009100730728E00022.png"\; state="\{\{state\}\}">b</figure-callout>}}^{i_b}\&dtri;---\left(4\right)$

(4) export lowpass digital filter reasonable in design according to the frequency characteristic of gyroscope and accelerometer, with Mach angle speed under the pedestal inertial system and disturbance acceleration filtering.

Be in naval vessel under the moored condition and under wind wave action, produce and wave and swing motion, the disturbing acceleration of its generation at the component main frequency on the inertial system all more than 1/15Hz.Gravity projection period of change is relevant with the motor-driven headway of carrier with earth rotation in the inertial system.Because the earth rotation cycle is 24 hours, when being in moored condition, carrier only has rotational-angular velocity of the earth, therefore just can " observations " in inertial coordinates system to rotate slowly drifting about of the gravity apparent acceleration that causes owing to the earth, so earth rotation will make the gravity projection change with 24 hours cycles around circular conical surface.Such change frequency is far below 1/15Hz; Rotational-angular velocity of the earth is 0Hz at the change frequency of pedestal inertial system, therefore much smaller than any Mach angle speed in frequency.

The low-pass filter of two different frequencies of design is taken all factors into consideration factors such as low-pass characteristic, time-delay size, and the transitional zone of setting filtering gyro signal and accelerometer signal wave filter is respectively [0.001Hz, 0.01Hz], [0.01Hz, 0.02Hz].

Utilize rotational-angular velocity of the earth under the pedestal inertial system, to change this characteristic, take low-pass filtering technique the gyroscope information under the inertial system for normal value and acceleration of gravity information present slow circular cone in the pedestal inertial system

And acceleration information

Handle, the filtering carrier obtains pure relatively rotational-angular velocity of the earth owing to wave and swing the disturbance angle velocity and the acceleration of motion generation

And acceleration of gravity

It obtains flow process such as accompanying drawing 2.

(5) angular velocity information after the low-pass filtering treatment is utilized weighting ask the average filter algorithm to revise, filtering is ripple by a small margin;

Through the rotational-angular velocity of the earth information that obtains after the IIR low-pass filtering treatment, the angular velocity order of magnitude on three directions is all 10 ^-3Below, even the pass band damping value of low-pass filter is very little, also can produce ripple in a small amount.Such signal is unfavorable for the analytical method aligning, therefore adopts the angular velocity information after weighting asks the average filter algorithm to low-pass filtering to carry out denoising Processing once more.This method is the simplest a kind of signal processing mode, and algorithmic formula is as follows: establish known equidistant sampled point x ₀＜x ₁＜...＜x _N-1＜... on observation data be y ₀, y ₁..., y _N-1, y _iExpression y _iSmooth value.Getting weighting coefficient is 1, gets 400 seconds to 600 seconds data after the low-pass filtering and does once smoothly, then has:

${\stackrel{\&OverBar;}{y}}_i=\frac{y_{i-n}+y_{i-\mathrm{<figure-callout\; id="1"\; label="n\; +"\; filenames="H2009100730728E00021.png,H2009100730728E00022.png"\; state="\{\{state\}\}">n</figure-callout>}+1}+\&CenterDot;\&CenterDot;\&CenterDot;+{\mathrm{<figure-callout\; id="0"\; label="y"\; filenames="H2009100730728E00021.png,H2009100730728E00022.png"\; state="\{\{state\}\}">y</figure-callout>}}_0+{\mathrm{<figure-callout\; id="1"\; label="y"\; filenames="H2009100730728E00021.png,H2009100730728E00022.png"\; state="\{\{state\}\}">y</figure-callout>}}_1+\&CenterDot;\&CenterDot;\&CenterDot;+y_{i+n-2}+y_{i+n-1}}{n}---\left(5\right)$

(6) make up the strapdown matrix according to rotational-angular velocity of the earth and acceleration of gravity, finish the initial alignment of inertial navigation system;

Utilize rotational-angular velocity of the earth ω _IeThe projection of fastening at navigation coordinate with gravity acceleration g, and their coordinate transformation relations between the projection that the pedestal inertial coordinate is fastened calculate attitude matrix

$T_{i_{b0}}^n={\left[\begin{array}{c}{\left(g^n\right)}^T\\ {(g^n\&times;{\mathrm{\&omega;}}_{\mathrm{ie}}^n)}^T\\ {((g^n\&times;{\mathrm{\&omega;}}_{\mathrm{ie}}^n)\&times;g^n)}^T\end{array}\right]}^{-1}\left[\begin{array}{c}{\left(g^{i_{b0}}\right)}^T\\ {(g^{i_{b0}}\&times;{\mathrm{\&omega;}}_{\mathrm{ie}}^{i_{b0}})}^T\\ {((g^{i_{b0}}\&times;{\mathrm{\&omega;}}_{\mathrm{ie}}^{i_{b0}})\&times;g^{i_{b0}})}^T\end{array}\right]---\left(6\right)$

Obtain

The substitution following formula calculates the strapdown matrix T _b ⁿFinish the initial alignment of inertial navigation system.

$T_b^n=T_{i_{b0}}^n{T}_b^{i_{b0}}---\left(7\right)$

Claims (3)

1. optical fiber strapdown system for ship mooring alignment methods based on digital low-pass filtering is characterized in that may further comprise the steps:

(1) determines the initial position parameters of carrier by GPS, they are bound to navigational computer;

(2) strapdown inertial navitation system (SINS) is carried out the preheating preparation, gathers the data of fibre optic gyroscope and quartz accelerometer output;

(3) fibre optic gyroscope that collects and the data of quartz accelerometer are carried out coordinate conversion, be transformed under the pedestal inertial coordinates system;

(4) the frequency characteristic output according to gyroscope and accelerometer designs lowpass digital filter, with Mach angle speed under the pedestal inertial system and disturbance acceleration filtering;

(5) angular velocity information after the low-pass filtering treatment is utilized weighting ask the average filter algorithm to revise, filtering is ripple by a small margin;

(6) make up the strapdown matrix according to rotational-angular velocity of the earth and acceleration of gravity, finish the initial alignment of inertial navigation system;

Described data-switching with fibre optic gyroscope and quartz accelerometer specifically comprises the steps: to the pedestal inertial coordinates system

Be the transition matrix between pedestal inertial coordinates system and the carrier coordinate system,, utilize the hypercomplex number method matrix according to gyrostatic output

Carry out real-time update, for the computing of following one-period provides parameter;

Strapdown inertial navitation system (SINS) under the swinging condition comprises the rotational-angular velocity of the earth that the cycle changes in the gyroscope output The kinetic angular velocity of carrier line

Wave the angular velocity that causes

With gyroscope constant value drift ε, that is:

${\mathrm{\&omega;}}_{\mathrm{ib}}^b={\mathrm{\&omega;}}_{\mathrm{ie}}^b+{\mathrm{\&omega;}}_{\mathrm{en}}^b+{\mathrm{\&omega;}}_{\mathrm{nb}}^b+\mathrm{\&epsiv;}$

Gyroscope output is expressed as in the pedestal inertial system:

${\mathrm{\&omega;}}_{\mathrm{ib}}^{i_{b0}}=T_b^{i_{b0}}{\mathrm{\&omega;}}_{\mathrm{ib}}^b={\mathrm{\&omega;}}_{\mathrm{ie}}^{i_{b0}}+{\mathrm{\&omega;}}_{\mathrm{eb}}^{i_{b0}}+{\mathrm{\&omega;}}_{\mathrm{nb}}^{i_{b0}}+T_b^{i_{b0}}\mathrm{\&epsiv;}$

Wherein,

Be normal value, under the moored condition Be zero, extract that the main distracter of rotational-angular velocity of the earth is under the pedestal inertial system this moment

Because waving of carrier comprises gravity acceleration g in the accelerometer output ^b, wave the disturbing acceleration δ a that causes ^bWith the accelerometer error of zero

That is:

$f^b=-g^b+\mathrm{\&delta;}{a}^b+\&dtri;$

Because inertia device deviation and the influence of swinging motion cause having disturbing acceleration information in the projection of output under the pedestal inertial system of accelerometer

The output of accelerometer is transformed in the pedestal inertial system and is expressed as:

$f^{i_{b0}}=T_b^{i_{b0}}{f}^b=-g^{i_{b0}}+\mathrm{\&delta;}{a}^{i_{b0}}+T_b^{i_{b0}}\&dtri;;$

The transitional zone of described design filtering gyro signal and accelerometer signal wave filter is respectively [0.001Hz, 0.01Hz], [0.01Hz, 0.02Hz], takes low-pass filtering technique to the gyroscope information under the inertial system

And acceleration information

Handle, the filtering carrier obtains pure relatively rotational-angular velocity of the earth owing to wave and swing the disturbance angle velocity and the acceleration of motion generation

And acceleration of gravity

2. the optical fiber strapdown system for ship mooring alignment methods based on digital low-pass filtering according to claim 1 is characterized in that described weighting asks the average filter algorithm to be: known equidistant sampled point x ₀＜x ₁＜...＜x _N-1＜... on observation data be y ₀, y ₁..., y _N-1,

Expression y _iSmooth value, getting weighting coefficient is 1, get 400 seconds to 600 seconds data after the low-pass filtering do once level and smooth, then:

${\stackrel{\&OverBar;}{y}}_i=\frac{y_{i-n}+y_{i-n+1}+...+y_0+y_1+...+y_{i+n-2}+y_{i+n-1}}{n}.$

3. the optical fiber strapdown system for ship mooring alignment methods based on digital low-pass filtering according to claim 1 and 2, it is characterized in that describedly making up the strapdown matrix according to rotational-angular velocity of the earth and acceleration of gravity, the method for finishing the initial alignment of inertial navigation system is:

Utilize rotational-angular velocity of the earth ω _IeThe projection of fastening at navigation coordinate with gravity acceleration g, and their coordinate transformation relations between the projection that the pedestal inertial coordinate is fastened calculate attitude matrix

$T_{i_{b0}}^n={\left[\begin{array}{c}{\left(g^n\right)}^T\\ {(g^n\&times;{\mathrm{\&omega;}}_{\mathrm{ie}}^n)}^T\\ {((g^n\&times;{\mathrm{\&omega;}}_{\mathrm{ie}}^n)\&times;g^n)}^T\end{array}\right]}^{-1}\left[\begin{array}{c}{\left(g^{i_{b0}}\right)}^T\\ {(g^{i_{b0}}\&times;{\mathrm{\&omega;}}_{\mathrm{ie}}^{i_{b0}})}^T\\ {((g^{i_{b0}}\&times;{\mathrm{\&omega;}}_{\mathrm{ie}}^{i_{b0}})\&times;g^{i_{b0}})}^T\end{array}\right]$

Obtain

Substitution Calculate

Finish the initial alignment of inertial navigation system.

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