CN101196398A - Spacecraft posture confirming method based on Euler-q algorithm and DD2 filtering - Google Patents

Abstract

A spacecraft attitude fixing method of DD2 (Divided Difierence 2) filter and a counting method based on Euler-q (Euler-quaternion) are provided, which relates to a state estimation and attitude determination method based on vector observation. The invention is characterized in that: according to the reference ephemeris and the reference vector and the observation vector observed by a star sensor, the spacecraft attitude quaternion can be gotten through Euler-q counting method; through DD2 filter, on one hand, feedback compensation the attitude matrix obtained through resolving by gyro; on the other hand, revise the palstance output of three-axle gyro and conduct compensation to the constant drift of gyroscope. As for that, the current spacecraft attitude information when getting high precision can be achieved, the constant drift of gyroscope can be scaled on line. The invention is an unattended attitude determining method, which is characterized in high precision and good timeliness, being convenient and feasible, and can be used in the attitude fixing system of various spacecrafts.

Description

A kind of spacecraft attitude based on Euler-q algorithm and DD2 filtering is determined method

Technical field

The attitude that the present invention relates to a kind of spacecraft is determined method, particularly a kind of spacecraft attitude based on Euler-q (Euler-quaternion) algorithm and DD2 (Divided Difference 2) filtering is determined method, and the attitude that is used for various high-precision inertia/celestial combined navigation system is determined.

Background technology

It is to utilize spaceborne attitude sensor to measure resulting information that the attitude of spacecraft sets the tasks, through suitable processing, try to achieve the information that is fixed on a certain reference frame of spacecraft body coordinate system space, spacecraft is because the requirement of various tasks, need high-precision attitude information, this is one of gordian technique of spacecraft development and widespread use.

Inertia/astronomy, be that INS (Inertial Navigation System)/CNS (CelestialNavigation System) attitude and heading reference system is that a kind of autonomous attitude is fully determined navigational system, it utilizes the carrier angular velocity information of gyro to measure and the starlight information in the star sensor measurement visual field, on the basis of initial information, carry out attitude algorithm and filtering, attitude can be provided continuously, in real time, have that independence is strong, good concealment, be not subjected to advantage such as weather condition restriction, thereby be widely used in field such as space flight.The spacecraft attitude that uses is determined model at present, be state mostly with the attitude quaternion, because the degree of freedom of three-axis attitude is 3, therefore attitude quaternion exists redundant, if and the vector of getting attitude quaternion merely is the state of estimating, then must simplify, cause the precision of model to reduce the estimation model linearization.Be applied to spacecraft attitude and determine in the method, use determinacy vector observation merely, for example Davenport q method is owing to need computation of characteristic values and eigenmatrix, online dyscalculia, thereby be difficult to be applied.And on Davenport q method improved QuEsT (Quaternion Estimator) method, though on algorithm, obtained great improvement, still existed too to rely on the star sensor precision and can not revise gyroscopic drift and export the shortcoming of real-time attitude.SVD (the Singular ValueDecomposition) robustness is very strong but need svd, because svd is a complex work that operand is very big, is not very effective therefore.FOAM (A Fast Optimal MatrixAlgurithm) algorithm can not estimate that gyroscopic drift makes gyro output obtain on-line proving; And use other state estimation method, for example, EKF EKF (Extend Kalman Filter), because using the first order nonlinear of Taylor expansion handles, though can estimate nonlinear model, but it is not high to the nonlinear model estimated accuracy, UKF (Unsented Kalman Filter) then utilizes the sampled point of a series of approximate Gaussian distribution, carry out the recursion and the renewal of state and error covariance by the Unscented conversion, though precision increases, but calculate loaded down with trivial detailsly, real-time is not high, thereby is difficult to satisfy the requirement that attitude is determined real-time.

Summary of the invention

Technology of the present invention is dealt with problems and is: overcome the deficiencies in the prior art, provide a kind of spacecraft attitude to determine method based on Euler-q algorithm and DD2 filtering, the spacecraft attitude that this method is obtained by the observation of Euler-q algorithm computation vector, while is by the constant value drift of DD2 Filtering Estimation attitude error and gyro, high-accuracy posture information not only is provided, and has proofreaied and correct the output of gyro angular speed.

Technical solution of the present invention is: a kind of spacecraft attitude based on Euler-q algorithm and DD2 filtering is determined method, it is characterized in that using Euler-q algorithm and DD2 Filtering Estimation model, utilize star sensor and gyroscope, spacecraft attitude in the time of both can obtaining high-precision real, can estimate gyrostatic constant value drift again, its concrete steps are as follows:

(1) by the responsive spacecraft attitude of gyroscope, the output tri-axis angular rate, and use the angle increment algorithm to upgrade the attitude battle array, obtain the real-time attitude of spacecraft under geocentric inertial coordinate system: course angle , pitching angle theta, roll angle γ;

(2) utilize the responsive starlight of star sensor, pre-service obtains observing the coordinate of starlight vector s under the spacecraft body coordinate system through star chart; And through obtaining the coordinate of corresponding reference starlight vector v under geocentric inertial coordinate system with it after the identification of star chart coupling;

(3) use the Euler-q algorithm, utilize observation starlight vector and corresponding reference starlight vector with it, acquisition spacecraft attitude hypercomplex number;

(4) difference of the spacecraft attitude that resolves of the spacecraft attitude hypercomplex number that obtains with starlight observation and the middle gyroscope of step (1) is as observed quantity, and DD2 filtering is carried out in gyroscopic drift to the spacecraft attitude sum of errors, and quantity of state is: (Δ q ₁Δ q ₂Δ q ₃b ₁b ₂b ₃);

(5) the spacecraft attitude sum of errors gyroscope constant value drift that obtains by DD2 filtering, feedback compensation gyroscope output attitude and gyroscope output angle speed obtain the output of high-precision spacecraft attitude and high-precision gyro;

(6) behind the feedback compensation, repeat (1)-(5) step.

Principle of the present invention is: use gyroscope output angle speed to resolve attitude as the short-term reference, real-time attitude is provided, higher precision was arranged in the short time, but attitude information is constantly dispersed, the starlight vector that is obtained by star sensor provides high-precision long term reference spacecraft attitude by the Euler-q algorithm with certain frequency, with this long term reference attitude as observed quantity, by the DD2 wave filter, revise gyro output attitude, information is dispersed in correction, estimates gyroscope constant value drift simultaneously, the output of feedback compensation gyro, gyro is carried out on-line proving, keep high-accuracy posture to export in real time.

The present invention's advantage compared with prior art is: the invention provides the Euler q method of being calculated the attitude battle array by the revolving property at Euler axle and Euler angle, computing velocity is faster, adopting with attitude quaternion vector and gyro error simultaneously is the model of state, improved the precision of model, the singularity in having avoided calculating; And in the integrated attitude determination filtering, adopt DD2 Filtering Estimation hypercomplex number vector error and gyroscopic drift, the new wave filter that approaches with polynomial expression has been considered the uncertainty of new model state estimation, easier realization and do not need differentiate, precision is better than EKF and is not less than UKF, the computing velocity that when guaranteeing accuracy of attitude determination, improves greatly, estimate the constant value drift of gyro simultaneously, greatly facilitate the engineering practical application.

Description of drawings

Fig. 1 determines method flow diagram for the spacecraft attitude of use Euler-q algorithm of the present invention and DD2 filtering;

Fig. 2 is the relation between spacecraft body coordinate system and the geocentric inertial coordinate system.

Embodiment

As shown in Figure 1, 2, specific implementation method of the present invention is as follows:

1, by the responsive spacecraft attitude of gyroscope, the output tri-axis angular rate, and use the angle increment algorithm to upgrade the attitude battle array, and obtain spacecraft at geocentric inertial coordinate system, promptly earth the earth's core is an initial point, the sensing zenith is z _i, sensing first point of Aries is x _i, y _iWith x _i, z _iBecome the real-time attitude under the right-handed helix: course angle , pitching angle theta, roll angle γ.Gyro output attitude frequency is determined that by actual gyro sampling rate adopting output frequency in this example is 100HZ;

Calculate initial attitude hypercomplex number q battle array [q by initial attitude ₁q ₂q ₃q ₄], subscript 0 is an initial value:

The renewal matrix is:

$q(n+1)=\{\cos \frac{{\mathrm{\Δ\θ}}_0}{2}I+\frac{\sin \frac{{\mathrm{\Δ\θ}}_0}{2}}{{\mathrm{\Δ\θ}}_0}[\mathrm{\Δ\θ}\left]\right\}q\left(n\right)---\left(6\right)$

Δ θ=[Δ θ ₁Δ θ ₂Δ θ ₃] be the gyro output angle increment.Δ θ is the skew symmetry battle array of Δ θ:

$\left[\begin{array}{ccc}0& {\mathrm{\Δ\θ}}_2& {-\mathrm{\Δ\θ}}_3\\ {-\mathrm{\Δ\θ}}_2& 0& {\mathrm{\Δ\θ}}_1\\ {\mathrm{\Δ\θ}}_3& -{\mathrm{\Δ\θ}}_1& 0\end{array}\right]$

Calculating attitude cosine battle array is:

$C=\left[\begin{array}{ccc}{q}_4^2+q_1^2-q_2^2-q_3^2& 2(q_1{q}_2+q_4{q}_3)& 2(q_1{q}_3-q_4{q}_2)\\ 2(q_1{q}_2-q_4{q}_3)& q_4^2-q_1^2+q_2^2-q_3^2& 2(q_2{q}_3+q_4{q}_1)\\ 2(q_1{q}_3+q_4{q}_2)& 2(q_2{q}_3-q_4{q}_1)& q_4^2-q_1^2-q_2^2+q_3^2\end{array}\right]=\left[\begin{array}{ccc}{C}_{11}& C_{12}& C_{13}\\ C_{21}& C_{22}& C_{23}\\ C_{31}& C_{32}& C_{33}\end{array}\right]---\left(7\right)$

Calculate real-time attitude angle under the geocentric inertial coordinate system by the direction cosine battle array.

The attitude angle solution formula is as follows:

The angle of pitch is:

θ＝sin ^-1(C ₂₃) (8)

Crab angle such as following table:

C 21Value is judged	C 22Value is judged	Crab angle
			＝0	＞0	0
＜0	＞0	atan -1(-C 21/C 22)
			＜0	＝0	π/2
＜0	＜0	atan -1(-C 21/C 22)+π
			＝0	＜0	π
＞0	＜0	atan -1(-C 21/C 22)+π
			＞0	＝0	3π/2
＞0	＞0	atan -1(-C 21/C 22)+2π

Roll angle value such as following table:

C 13Value is judged	C 33Value is judged	Roll angle
			＝0	＜0	-π
＞0	＜0	atan -1(-C 13/C 33)-π
			＞0	＝0	-π/2
Arbitrary value	＞0	atan -1(-C 13/C 33)
			＜0	＝0	π/2
＜0	＜0	atan -1(-C 13/C 33)+π

2, utilize the responsive starlight of star sensor, pre-service obtains observing the coordinate of starlight vector s under the spacecraft body coordinate system through star chart, and promptly the spacecraft barycenter is an initial point, is reversed the zb axle with the earth's core line, with the tangent sensing of sky latitude east be x _b, y _bWith z _b, x _bBecome right-handed helix; And through obtaining the coordinate of corresponding reference starlight vector v under geocentric inertial coordinate system with it after the identification of star chart coupling;

3, use the Euler-q algorithm, utilize observation starlight vector and corresponding reference starlight vector with it, acquisition spacecraft attitude hypercomplex number;

Star sensor phase closing precision: ${\mathrm{\α}}_i=\frac{1}{{\mathrm{\β}}_i\underset{k=1}{\overset{n}{\mathrm{\Σ}}}1/{\mathrm{\β}}_k}---\left(9\right)$

Calculate the B matrix: $B=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{\α}}_i{s}_i{v}_i^T=\left[\begin{array}{ccc}{b}_{11}& b_{12}& b_{13}\\ b_{21}& b_{22}& b_{23}\\ b_{31}& b_{32}& b_{33}\end{array}\right]---\left(10\right)$

Compute vector Z:Z={b ₂₃-b ₃₂b ₃₁-b ₁₃b ₁₂-b ₂₁} ^T(11)

Calculate associated weight: ${\mathrm{\ξ}}_i=\frac{1}{{\mathrm{\β}}_i\underset{k=1}{\overset{n}{\mathrm{\Σ}}}1/{\mathrm{\β}}_k}---\left(12\right)$

Wherein subscript i is an i starlight, β _iPrecision when observing i starlight for star sensor, n is the starlight number, is as the criterion with the number of importance in star map recognition starlight.

Introduce vector of unit length: $d_i=\frac{v_i-s_i}{\left|\right|v_i-s_i\left|\right|}---\left(13\right)$

Calculate symmetric matrix: $H=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{\ξ}}_i{d}_i{d}_i^T=\left[\begin{array}{ccc}{h}_{11}& h_{12}& h_{13}\\ h_{21}& h_{22}& h_{23}\\ h_{31}& h_{32}& h_{33}\end{array}\right]---\left(14\right)$

The Euler axle is the proper vector of the minimal eigenvalue of H battle array.The computing formula of the proper vector of the minimal eigenvalue of H battle array is as follows:

$H{\stackrel{\→}{e}}_{\mathrm{opt}}={\mathrm{\λ}}_{\min }{\stackrel{\→}{e}}_{\mathrm{opt}}---\left(15\right)$

λ _MinBe minimal eigenvalue,

Be the optimal characteristics vector.

Can directly from H battle array 3 rank feature equatioies, directly resolve out:

λ ³+aλ ²+bλ+c＝0 (16)

Here a, b, the c coefficient can usually be represented according to the unit of H battle array:

a＝-tr[H]＝-h ₁₁-h ₂₂-h ₃₃

$b=-\mathrm{tr}\left[\mathrm{adjH}\right]=h_{11}{h}_{22}+h_{11}{h}_{33}+h_{22}{h}_{33}-h_{32}^2-h_{13}^2-h_{23}^2---\left(17\right)$

$c=-\det \left[H\right]=h_{11}{h}_{22}{h}_{33}+2h_{12}{h}_{13}{h}_{23}-h_{22}{h}_{13}^2-h_{11}{h}_{23}^2-h_{33}{h}_{12}^2$

Setup parameter is:

p ²＝(a/3) ²-(b/3)

q＝[(b/3)-(a/3) ²](a/3)-(c/3) (18)

$w=\frac{1}{3}{\cos }^{-1}(q/p^3)$

Three real roots separate into:

λ ₁＝-p(sinw+cosw)-a/3

λ ₂＝q(sinw-cosw)-a/3 (19)

λ ₃＝2pcosw-a/3

Because 0≤w≤π/3 draw λ _iSatisfy condition:

0≤λ ₁≤λ ₂≤λ ₃ (20)

λ _MinBe minimum λ value.Calculate λ once _MinProper vector, i.e. Euler q axle:

$(H-\mathrm{\λI}){\stackrel{\→}{e}}_{\mathrm{opt}}=M{\stackrel{\→}{e}}_{\mathrm{opt}}=\left[\begin{array}{c}{\stackrel{\→}{M}}_1\\ {\stackrel{\→}{M}}_2\\ {\stackrel{\→}{M}}_3\end{array}\right]{\stackrel{\→}{e}}_{\mathrm{opt}}=\left[\begin{array}{ccc}{m}_a& m_x& m_y\\ m_x& m_b& m_z\\ m_y& m_z& m_c\end{array}\right]{\stackrel{\→}{e}}_{\mathrm{opt}}=0---\left(21\right)$

Provide three selectable separating:

${\stackrel{\→}{e}}_1={\stackrel{\→}{M}}_2\×{\stackrel{\→}{M}}_3=\left\{\begin{array}{ccc}{m}_b{m}_c-m_z^2& m_y{m}_z-m_x{m}_c& m_x{m}_z{-m_{y}m}_b\end{array}\right\}$

${\stackrel{\→}{e}}_2={\stackrel{\→}{M}}_3\×{\stackrel{\→}{M}}_1=\left\{\begin{array}{ccc}{m}_y{m}_z-m_x{m}_c& m_a{m}_c-m_y^2& m_x{m}_y{-m_{z}m}_a\end{array}\right\}---\left(22\right)$

${\stackrel{\→}{e}}_3={\stackrel{\→}{M}}_1\×{\stackrel{\→}{M}}_2=\left\{\begin{array}{ccc}{m}_x{m}_z-m_y{m}_b& m_x{m}_y-m_z{m}_a& m_a{m}_b-m_x^2\end{array}\right\}$

All (k=1,2,3) all are parallel, and the mould that calculates each vector is:

$p_1=|m_b{m}_c-m_z^2|$

$p_2=|m_a{m}_c-m_y^2|$

$p_3=|m_a{m}_b-m_x^2|$

Select p near unit value _k(k=1,2,3), then by ${\stackrel{\→}{e}}_{\mathrm{opt}}={\stackrel{\→}{e}}_k/\left|\right|{\stackrel{\→}{e}}_k\left|\right|$ Draw optimum Euler-q axle.

Calculate relevant Euler-q angle Φ _Opt:

$\sin {\mathrm{\Φ}}_{\mathrm{opt}}=(1/D)Z^T{\stackrel{\→}{e}}_{\mathrm{opt}}$

${\cos \mathrm{\Φ}}_{\mathrm{opt}}=(1/D)\left(\mathrm{tr}\left(B\right)\right)-{\stackrel{\→}{e}}_{\mathrm{opt}}^{T}B{\stackrel{\→}{e}}_{\mathrm{opt}}---\left(24\right)$

Wherein: $D^2=\left(Z^T{\stackrel{\→}{e}}_{\mathrm{opt}}\right)+{(\mathrm{tr}\left(B\right)-{\stackrel{\→}{e}}_{\mathrm{opt}}^T{\mathrm{Be}}_{\mathrm{opt}})}^2$

The spacecraft attitude matrix A can be represented by Euler-q axle and Euler-q angle:

$A=I\cos {\mathrm{\Φ}}_{\mathrm{opt}}+(1-\cos \mathrm{\Φ}){\stackrel{\→}{e}}_{\mathrm{opt}}{{\stackrel{\→}{e}}_{\mathrm{opt}}}^T-\tilde{e}{\sin \mathrm{\Φ}}_{\mathrm{opt}}---\left(25\right)$

Be

The multiplication cross skew matrix.Resolve spacecraft attitude thus.

4, the spacecraft attitude that resolves of spacecraft attitude hypercomplex number that obtains with starlight observation and gyroscope is poor, as observed quantity, DD2 filtering is carried out in gyroscopic drift to the spacecraft attitude sum of errors, and the filtering cycle is by importance in star map recognition decision interval time, this routine medium frequency is 1HZ, and quantity of state is: (δ q ₁δ q ₂δ q ₃b ₁b ₂b ₃)

State equation:

$\left[\begin{array}{c}\mathrm{\δ}\stackrel{\·}{\stackrel{\→}{q}}\\ \stackrel{\·}{\stackrel{\→}{b}}\end{array}\right]=\left[\begin{array}{c}-[w\×]\mathrm{\δ}\stackrel{\→}{q}-\frac{1}{2}[\mathrm{\δ}{q}_0{I}_3+\mathrm{\δ}\stackrel{\→}{q}]\stackrel{\→}{b}-\frac{1}{2}[\mathrm{\δ}{q}_0{I}_3+\mathrm{\δ}\stackrel{\→}{q}]{\mathrm{\ϵ}}_1\\ {\mathrm{\ϵ}}_2\end{array}\right]---\left(26\right)$

Observation equation:

y＝[I ₃ 0]X+w (27)

Can get after the discretize:

x _k+1＝f(x _k，v _k) (28)

y _k＝g(x _k，w _k) (29)

Below various in, subscript-for the amount average, subscript ^ for the amount valuation, subscript ~ for the amount error.

Introducing four cholesky factors decomposes:

$Q=S_v{S}_v^T,R=S_w{S}_w^T---\left(30\right)$

$\stackrel{\‾}{P}={\stackrel{\‾}{S}}_x{\stackrel{\‾}{S}}_x^T,\hat{P}={\hat{S}}_x{\hat{S}}_x^T$

Wherein, $\stackrel{\‾}{P}=E\left[(x_k-{\stackrel{\‾}{x}}_k){(x_k-{\stackrel{\‾}{x}}_k)}^T\right|Y^{k-1}],\hat{P}=E[(x_k-{\stackrel{\‾}{x}}_k){(x_k-{\stackrel{\‾}{x}}_k)}^T\left|Y^k\right]=\stackrel{\‾}{P}-K_k{P}_y{K}_k^T,$

Q is a state-noise variance battle array, and R is the measuring noise square difference battle array, Y ^K-1=[y ₀y ₁Y _K-1], be the measurement matrix in past.

Use S _{X, j}Expression S _xThe j column element of matrix.

Can obtain following each amount:

$S_{\mathrm{xx}}^{\left(1\right)}\left(k\right)=\left\{(f_i({\hat{x}}_k+h{\hat{S}}_{x,j},{\stackrel{\‾}{v}}_k)+f_i({\hat{x}}_k-h{\hat{S}}_{x,j},{\stackrel{\‾}{v}}_k)/\left(2h\right))\right\}$

$S_{\mathrm{xv}}^{\left(1\right)}\left(k\right)=\left\{(f_i({\hat{x}}_k,{\stackrel{\‾}{v}}_k+h{S}_{v,j})+f_i({\hat{x}}_k-h{S}_{x,j},{\stackrel{\‾}{v}}_k)/\left(2h\right))\right\}$

$S_{y\hat{x}}^{\left(1\right)}\left(k\right)=\left\{(g_i({\stackrel{\‾}{x}}_k,+h{\stackrel{\‾}{S}}_{x,j},{\stackrel{\‾}{w}}_k)+g_i({\stackrel{\‾}{x}}_k-h{\stackrel{\‾}{S}}_{x,j},{\stackrel{\‾}{w}}_k)/\left(2h\right))\right\}$

$S_{\mathrm{yw}}^{\left(1\right)}\left(k\right)=\left\{(g_i({\stackrel{\‾}{x}}_k,{\stackrel{\‾}{w}}_k+h{S}_{w,j})+g_i({\stackrel{\‾}{x}}_k,{\stackrel{\‾}{w}}_k-h{S}_{w,j})/\left(2h\right))\right\}---\left(31\right)$

$S_{\mathrm{xx}}^{\left(2\right)}\left(k\right)=\left\{\frac{\sqrt{h^2-1}}{{2h}^2}(f_i({\hat{x}}_k+h{\hat{S}}_{x,j},{\stackrel{\‾}{v}}_k)+f_i({\hat{x}}_k-h{\hat{S}}_{x,j},{\stackrel{\‾}{v}}_k)-2f_i({\hat{x}}_k,{\stackrel{\‾}{v}}_k))\right\}$

$S_{\mathrm{xv}}^{\left(2\right)}\left(k\right)=\left\{\frac{\sqrt{h^2-1}}{{2h}^2}(f_i({\hat{x}}_k,{\stackrel{\‾}{v}}_k+h{S}_{x,j})+f_i({\hat{x}}_k-h{S}_{x,j},{\stackrel{\‾}{v}}_k)-2f_i({\hat{x}}_k,{\stackrel{\‾}{v}}_k))\right\}$

$S_{x\hat{x}}^{\left(2\right)}\left(k\right)=\left\{\frac{\sqrt{h^2-1}}{{2h}^2}(g_i({\stackrel{\‾}{x}}_k+h{\stackrel{\‾}{S}}_{x,j},{\stackrel{\‾}{w}}_k)+g_i({\stackrel{\‾}{x}}_k-h{\stackrel{\‾}{S}}_{x,j},{\stackrel{\‾}{w}}_k)-2g_i({\stackrel{\‾}{x}}_k,{\stackrel{\‾}{w}}_k))\right\}$

$S_{\mathrm{yw}}^{\left(2\right)}\left(k\right)=\left\{\frac{\sqrt{h^2-1}}{{2h}^2}(g_i({\stackrel{\‾}{x}}_k,{\stackrel{\‾}{w}}_k{+\mathrm{hS}}_{w,j})+g_i({\stackrel{\‾}{x}}_k,{\stackrel{\‾}{w}}_k-h{S}_{w,j})-2g_i({\stackrel{\‾}{x}}_k,{\stackrel{\‾}{w}}_k))\right\}---\left(32\right)$

Suppose that evaluated error is Gauss and does not have partially that establishing gap length is h ²=3.

One step upgraded:

${\stackrel{\‾}{x}}_{k+1}=\frac{h^2-n_x-n_y}{h^2}f({\hat{x}}_k,{\stackrel{\‾}{v}}_k)+\frac{1}{{2h}^2}\underset{p=1}{\overset{n_x}{\mathrm{\Σ}}}(f({\hat{x}}_k+h{\hat{S}}_{x,p},{\stackrel{\‾}{v}}_k)+f({\hat{x}}_k-h{\hat{S}}_{x,p},{\stackrel{\‾}{v}}_k))$

$\frac{1}{2h^2}\underset{p=1}{\overset{n_y}{\mathrm{\Σ}}}(f({\hat{x}}_k,{\stackrel{\‾}{v}}_k+h{S}_{v,p})+f({\hat{x}}_k,{\stackrel{\‾}{v}}_k-h{S}_{v,p}))---\left(33\right)$

$y_k=\frac{h^2-n_x-n_w}{h^2}f({\stackrel{\‾}{x}}_k,{\stackrel{\‾}{w}}_k)+\frac{1}{2h^2}\underset{p=1}{\overset{n_x}{\mathrm{\Σ}}}(g({\stackrel{\‾}{x}}_k+h{\stackrel{\‾}{S}}_{x,p},{\stackrel{\‾}{w}}_k)+g({\stackrel{\‾}{x}}_k-h{\stackrel{\‾}{S}}_{x,p},{\stackrel{\‾}{w}}_k))$

$\frac{1}{2h^2}\underset{p=1}{\overset{n_v}{\mathrm{\Σ}}}(g({\stackrel{\‾}{x}}_k,{\stackrel{\‾}{w}}_k+h{S}_{w,p})+g({\stackrel{\‾}{x}}_k,{\stackrel{\‾}{w}}_k-h{S}_{w,p}))---\left(34\right)$

From compound matrice, obtain:

$S_x\left(k\right)=\left[\begin{array}{cccc}{S}_{x\hat{x}}^{\left(1\right)}\left(k\right)& S_{\mathrm{xv}}^{\left(1\right)}\left(k\right)& S_{x\hat{x}}^{\left(2\right)}\left(k\right)& S_{\mathrm{xv}}^{\left(2\right)}\left(k\right)\end{array}\right]---\left(35\right)$

$S_y\left(k\right)=\left[\begin{array}{cccc}{S}_{y\hat{x}}^{\left(1\right)}\left(k\right)& S_{\mathrm{yw}}^{\left(1\right)}\left(k\right)& S_{y\hat{x}}^{\left(2\right)}\left(k\right)& S_{\mathrm{yw}}^{\left(2\right)}\left(k\right)\end{array}\right]---\left(36\right)$

$P_{\mathrm{xy}}\left(k\right)={\stackrel{\‾}{S}}_x\left(k\right)S_{y\hat{x}}{\left(k\right)}^T---\left(37\right)$

Gain matrix is:

K _k＝P _xy(k)[S _y(k)S _y(k) ^T] ^-1 (38)

${\hat{x}}_k={{\stackrel{\‾}{x}}_k+K}_k(y_k-{\stackrel{\‾}{y}}_k)---\left(39\right)$

Covariance matrix:

$\hat{P}=({\stackrel{\‾}{S}}_x-{\mathrm{KS}}_{\mathrm{yx}}^{\left(1\right)}){({\stackrel{\‾}{S}}_x-{\mathrm{KS}}_{\mathrm{yw}}^{\left(1\right)})}^T+{\mathrm{KS}}_{\mathrm{yw}}^{\left(1\right)}{\left({\mathrm{KS}}_{\mathrm{yw}}^{\left(1\right)}\right)}^T+{\mathrm{KS}}_{\mathrm{yx}}^{\left(2\right)}{\left({\mathrm{KS}}_{\mathrm{yx}}^{\left(2\right)}\right)}^T+{\mathrm{KS}}_{\mathrm{yw}}^{\left(2\right)}{\left({\mathrm{KS}}_{\mathrm{yw}}^{\left(2\right)}\right)}^T---\left(40\right)$

${\hat{S}}_x\left(k\right)=\left[\begin{array}{cccc}{\stackrel{\‾}{S}}_x\left(k\right)-{\mathrm{KS}}_{\mathrm{yx}}^{\left(1\right)}\left(k\right)& {\mathrm{KS}}_{\mathrm{yw}}^{\left(1\right)}\left(k\right)& {\mathrm{KS}}_{\mathrm{yx}}^{\left(2\right)}\left(k\right)& {\mathrm{KS}}_{\mathrm{yw}}^{\left(2\right)}\left(k\right)\end{array}\right]---\left(41\right)$

5, the spacecraft attitude error that obtains by DD2 filtering, feedback compensation gyroscope output attitude obtains high-precision spacecraft attitude; By the gyroscope constant value drift that filtering obtains, feedback compensation gyroscope output angle speed, the gyro output after obtaining proofreading and correct:

[δ q in the state that draws by filtering ₁δ q ₂δ q ₃], obtain error quaternion:

$\mathrm{\δq}=\left[\begin{array}{cccc}{\mathrm{\δq}}_1& \mathrm{\δ}{q}_2& \mathrm{\δ}{q}_3& \mathrm{sqrt}(1-{\mathrm{\δq}}_1^2-{\mathrm{\δq}}_2^2-{\mathrm{\δq}}_3^2)\end{array}\right],$ Calculate attitude error battle array C _g ^c, revise attitude battle array by gyro output: $C_{\mathrm{end}}^c=C_g^{c}C---\left(42\right)$

Calculate the attitude behind the feedback compensation thus.

In must doing well by filtering $\stackrel{\→}{b}=\left[\begin{array}{ccc}{b}_1& b_2& b_3\end{array}\right],$ The output of correction gyro:

$w_{\mathrm{end}}=w_{\mathrm{out}}-\stackrel{\→}{b}---\left(43\right)$

In the formula, w _OutBe the output of the gyro before revising.

6, behind the feedback compensation, repeat the 1-5 step.

Claims (3)

1. the spacecraft attitude based on Euler-q algorithm and DD2 filtering is determined method, it is characterized in that may further comprise the steps:

(1) by the responsive spacecraft attitude of gyroscope, the output tri-axis angular rate obtains the real-time attitude of spacecraft under geocentric inertial coordinate system;

(2) utilize the responsive starlight of star sensor, pre-service obtains observing the coordinate of starlight vector s under the spacecraft body coordinate system through star chart; And through obtaining the coordinate of corresponding reference starlight vector v under geocentric inertial coordinate system with it after the identification of star chart coupling;

(3) use the Euler-q algorithm, utilize observation starlight vector and corresponding reference starlight vector with it, acquisition spacecraft attitude hypercomplex number;

(4) spacecraft attitude that resolves of spacecraft attitude hypercomplex number that obtains with starlight observation and gyroscope is poor, and as observed quantity, DD2 filtering is carried out in gyroscopic drift to the spacecraft attitude sum of errors;

(5) the spacecraft attitude sum of errors gyroscope constant value drift that obtains by DD2 filtering, feedback compensation gyroscope output attitude and gyroscope output angle speed obtain attitude and the gyro output of spacecraft body coordinate system with respect to geocentric inertial coordinate system;

(6) behind the feedback compensation, repeat (1)-(5) step.

2. the spacecraft attitude based on Euler-q algorithm and DD2 filtering according to claim 1 is determined method, it is characterized in that: in the described step (4), estimation to the gyroscopic drift of spacecraft attitude sum of errors realizes by the DD2 wave filter, and attitude determines that model is as follows:

Quantity of state is: (δ q ₁δ q ₂δ q ₃b ₁b ₂b ₃), δ q wherein ₁δ q ₂δ q ₃Be the vector part of attitude error hypercomplex number, b ₁b ₂b ₃It is respectively the constant value drift of three outputs of gyro;

State equation, observation equation is respectively:

$\left[\begin{array}{c}\mathrm{\δ}\stackrel{\·}{\stackrel{\→}{q}}\\ \stackrel{\·}{\stackrel{\→}{b}}\end{array}\right]=\left[\begin{array}{c}-[w\×]\mathrm{\δ}\stackrel{\→}{q}-\frac{1}{2}[\mathrm{\δ}{q}_0{I}_3+\mathrm{\δ}\stackrel{\→}{q}]\stackrel{\→}{b}-\frac{1}{2}[\mathrm{\δ}{q}_0{I}_3+\mathrm{\δ}\stackrel{\→}{q}]{\mathrm{\ϵ}}_1\\ {\mathrm{\ϵ}}_2\end{array}\right]---\left(1\right)$

y=[I ₃ 0]X+W (2)

Wherein, y is observed quantity, ε ₁, ε ₂Be white Gaussian noise, w is a gyro output angle speed, and W is a measurement noise, I ₃Be 3 * 3 unit vectors.

3. the spacecraft attitude based on Euler-q algorithm and DD2 filtering according to claim 1 is determined method, it is characterized in that: in the described step (5), the feedback compensation of spacecraft attitude sum of errors gyroscopic drift is realized by following steps:

[δ q in the state that draws by filtering ₁δ q ₂δ q ₃], obtain error quaternion:

$\mathrm{\δq}=\left[\begin{array}{cccc}{\mathrm{\δq}}_1& \mathrm{\δ}{q}_2& \mathrm{\δ}{q}_3& \mathrm{sqrt}(1-{\mathrm{\δq}}_1^2-{\mathrm{\δq}}_2^2-\mathrm{\δ}{q}_3^2)\end{array}\right],$ Calculate attitude error battle array C _g ^c, revise attitude battle array C by gyro output, obtain the attitude battle array behind the feedback compensation:

$C_{\mathrm{end}}^c=C_g^{c}C---\left(3\right)$

In must doing well by filtering $\stackrel{\→}{b}=\left[\begin{array}{ccc}{b}_1& b_2& b_3\end{array}\right],$ The output of correction gyro:

$w_{\mathrm{end}}=w_{\mathrm{out}}-\stackrel{\→}{b}---\left(4\right)$

In the formula, w _OutBe the output of the gyro before revising.

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