CN109343550B - Spacecraft angular velocity estimation method based on rolling time domain estimation - Google Patents
Spacecraft angular velocity estimation method based on rolling time domain estimation Download PDFInfo
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Abstract
The invention relates to a rolling time domain estimation-based spacecraft angular velocity estimation method, which comprises the following steps of: constructing a state equation and an observation equation of the angular velocity of the spacecraft based on a spacecraft dynamics model; simplifying four paths of twelve-dimensional angular velocity measurement information of the redundant fiber optic gyroscope combination to obtain three-axis angular velocity measurement data of the spacecraft; based on the constructed state equation and observation equation and the obtained spacecraft triaxial angular velocity measurement data, spacecraft angular velocity constraint and control moment constraint are considered at the same time, online estimation is carried out by using a rolling time domain estimation strategy and a multiple target shooting method, and the estimated value of the spacecraft optimal angular velocity at the current moment is obtained. The method has the advantages of high calculation efficiency, high reliability, good operation effect, high precision and the like, simultaneously fully considers the influences of the physical constraint and the control moment constraint of the spacecraft, is an effective optimal online state estimation method, and is suitable for the angular velocity estimation problem of the constrained spacecraft.
Description
Technical Field
The invention relates to a rolling time domain estimation-based spacecraft angular velocity estimation method, which is mainly applied to the problem of spacecraft angular velocity on-line estimation considering angular velocity constraint and control moment constraint and belongs to the field of spacecraft attitude determination.
Background
The development of the aerospace technology is based on the control and navigation technology of the spacecraft, and how to improve the control and navigation precision of the spacecraft on the basis of the existing system hardware equipment has important significance. In recent years, with the trend of diversification and complication of flight missions of spacecrafts, for the spacecrafts performing the flight missions in orbit, the accuracy of determining attitude parameters of the spacecrafts determines the accuracy of attitude control, and further influences the function realization of the whole flight missions.
The emergence of new complex space missions puts higher requirements on the control precision of the spacecraft, so that the research of a high-precision angular velocity estimation method is particularly important. Most of existing spacecraft angular velocity estimation methods are researched around Kalman filtering algorithms, Kalman filtering has many advantages, meanwhile, conclusions about linear Kalman filtering are very mature, but Kalman filtering cannot do constraint processing and system model uncertainty, so that very useful information existing in reality in an actual system is ignored, and the practicability of Kalman filtering is limited. The rolling time domain estimation method is designed based on a model, only a fixed amount of measurement data before the current moment is considered, and the influence of the measurement data at other moments on estimation is described by an approximate method, so that the problems of 'infinite memory' and 'data explosion' are well solved, known information about system interference and system state in a time domain constraint form can be fully utilized, the time domain constraint and nonlinear characteristics of the system are directly expressed in an optimization problem, and the system state is accurately estimated, and the reasonability and accuracy of estimation are improved.
For the problem of spacecraft angular velocity estimation, patent CN201711456224.3 selects a Singer acceleration probability model taking spacecraft angular velocity and angular acceleration as state quantities as a state model, performs image processing on a multi-frame fuzzy star map, extracts optical flow information as quantity measurement, establishes a measurement model according to the relation between star point optical flow and spacecraft angular velocity, and finally completes estimation of spacecraft triaxial angular velocity through kalman filtering, but the state model, the measurement model and the estimation algorithm in the method are all different from the method; the patent CN201610180095.9 provides a method for estimating the constrained angular velocity of a gyroscope-free inertial measurement system, which has the characteristics of clear estimation steps and estimation error which does not change along with time, can be used for estimating the angular velocity under the condition of configuring a redundant accelerometer of the gyroscope-free inertial measurement system, and can effectively improve the estimation precision of the angular velocity, but the method does not consider the constraint of the angular velocity;
for an application example of a rolling time domain estimation algorithm, patent CN201210102226.3 firstly identifies parameters of a power battery model, and then estimates the state of charge of the power battery by using a rolling time domain estimation method on the basis of the determined model; the patent CN201610201135.3 estimates the wave frequency model parameters and wave frequency motion of the dynamic positioning ship by using a rolling time domain estimation method; the patent CN201510235759.2 considers the state constraint condition for a linear model in radar tracking, and adopts a linear rolling time domain method to estimate the position of a tracking target; the patent CN201711466618.7 firstly carries out sensitivity analysis based on a circuit parameter function to establish an augmented nonlinear state space equation, then establishes an SOC and model parameter adaptive joint estimation model based on a rolling time domain estimation strategy, sets each algorithm parameter, and finally carries out SOC and model parameter joint estimation by utilizing the online estimation model based on detection voltage and current. The system models used in the above patents are not spacecraft models, so the above methods are not suitable for spacecraft.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: because the spacecraft is often influenced by various external disturbance moments such as gravity gradient moment, aerodynamic resistance, sunlight pressure and the like in the process of attitude control in space, a spacecraft dynamics model has certain uncertainty, and meanwhile, a measurement error exists in the measurement of the angular speed of an optical fiber gyroscope on the spacecraft. In order to obtain effective angular velocity information with higher precision, the invention provides a rolling time domain estimation-based spacecraft angular velocity estimation method, which is a state estimation method which is designed based on a model, considers state time domain constraint, considers fixed time domain measurement data, is reasonable and has higher estimation precision.
According to an aspect of the invention, a method for estimating the angular velocity of a spacecraft based on rolling time domain estimation is provided, which comprises the following steps:
s1: constructing a state equation and an observation equation of the angular velocity of the spacecraft based on a spacecraft dynamics model in a special orthogonal group SO (3) description mode;
s2: simplifying four-way twelve-dimensional angular rate measurement information combined by redundant fiber optic gyroscopes by using a new weighted data fusion method for distributing weights based on failure factors to obtain spacecraft three-axis angular rate measurement data;
s3: based on the state equation and the observation equation constructed in the step S1 and the spacecraft triaxial angular rate measurement data obtained in the step S2, spacecraft angular rate constraint and control moment constraint are considered at the same time, online estimation is carried out by using a rolling time domain estimation strategy and a multiple target shooting method, and an estimated value of the spacecraft optimal angular rate at the current moment is obtained.
Further, the spacecraft dynamics model in the special orthogonal group SO (3) description mode in step S1 is:
Rk+1=RkFk(2)
wherein h is a sampling time interval; superscript T represents matrix transposition; the index k denotes the kth sampling instant; matrix Rk,FkE SO (3) is a rotation matrix,a rotation matrix representing the euler attitude angle description of the spacecraft,a rotation matrix representing the description of the Euler attitude error angle of the spacecraft between two sampling instants, FkIs the solution of implicit equation (1);which represents the angular momentum of the spacecraft,is an inertial matrix of the spacecraft,is the spacecraft angular velocity;representing the external disturbance moment of the spacecraft caused by gravity gradient moment, aerodynamic resistance, sunlight pressure and the like;Representing the control moment required by the attitude maneuver or the stability of the spacecraft; positive definite arrayRepresents a non-standard inertia matrix, which is related to the inertia matrix J;is about real vectorFor any vectorIts corresponding oblique antisymmetric array x×The form is as follows:
further, based on the spacecraft dynamics model, a state equation and an observation equation for rolling time domain estimation can be constructed as follows:
taking the system state quantity as omega ═ omegax,ωy,ωz)TThen the state equation is
Taking the observed quantity of the system as y ═ yx,yy,yz)TThen the observation equation is
Jyk=CJωk+νk(5)
Wherein ω ═ ω (ω ═ ω)x,ωy,ωz)TIs the spacecraft angular velocity; y ═ yx,yy,yz)TThe output value of the angular speed measurement data after the redundant fiber optic gyroscope combined data processing,yx,yy,yzmeasuring the angular rate of each inertia main shaft of the spacecraft; fkThe epsilon SO (3) is an auxiliary variable and represents the relative attitude between two adjacent moments;andthe system external interference and the measurement noise are respectively independent from each other, and the measurement noise is independent from the system external interference and the initial state;is a measurement matrix.
Furthermore, since the observation equation needs three-dimensional measurement data, and the combination of the redundant fiber optic gyroscopes feels that the combination of the fiber optic gyroscopes is four-way twelve-dimensional measurement data, a new data fusion method for distributing weights based on failure factors needs to be designed. The new weighted data fusion method for distributing the weights based on the failure factors in step S2 is as follows:
wherein the content of the first and second substances,measuring data of the angular velocity of the spacecraft after data processing;the angular velocity information of the spacecraft sensed by the ith optical fiber gyroscope in the redundant optical fiber gyroscopes,for four-way twelve-dimensional angular rate measurement information αiAnd i is 1,2,3 and 4 is a mounting deflection angle of the optical fiber gyroscope, and represents the projection of the axial direction of the ith optical fiber gyroscope on the xoy plane and the ox axisβiThe i is 1,2,3 and 4, which is the installation high-low angle of the optical fiber gyroscope and represents the included angle between the axial direction of the ith optical fiber gyroscope and the xoy plane;as a weighting factor, the failure factor ρ of the ith optical fiber gyroscopei∈[0,1]Influence and need to satisfy the constraint τ1+τ2+τ3+τ4=1。
Further, the specific steps of performing online estimation by using the rolling time domain estimation strategy and the multiple targeting method in step S3 are as follows:
1) a priori estimation of initial state assuming a known systemCovariance matrix of initial state error is P0The weight matrix of the external interference and the measured noise of the system is Q1,Q2And P is0,Q1,Q2All are positive definite matrixes, and the length of a rolling time domain is N;
2) at time T, the optimization problem defined by the rolling time domain estimation is as follows:
in the two cases, the first term in the objective function represents the cost sum of external interference of the system at each sampling moment, the second term represents the cost sum of measurement noise at each sampling moment, and the third term represents prior estimation when T is less than or equal to NDegree of trust of, at T>When the N is greater than the N value,to approximate the cost function of a constrained nonlinear system, i.e., to the arrival cost function of an unconstrained linear system, representing the effect of the remaining measurement data on the estimate, the cost function of a constrained nonlinear system is approximated by the arrival cost function of an unconstrained linear systemThe cost function is of the form:
in the formula, initial state estimationObey normal distributionPT-NTo estimate the error covariance, it can be updated by the following equation (8);
meanwhile, the objective function needs to satisfy spacecraft dynamics, spacecraft angular velocity time domain constraint and control moment constraint, and the specific mathematical expression form is as follows:
angular velocity time domain constraint:
wherein the content of the first and second substances,for the angular rate estimate obtained by the rolling time domain estimation,the minimum and maximum angular velocities allowed by the main axes of the spacecraft are determined by the properties of physical devices such as solar sailboards, sensors and the like installed on the spacecraft. It should be noted that the angular velocity time domain constraint proposed herein is the optimal angular velocity estimated by the rolling time domain online estimation algorithmConstraining rather than imposing an actual operating angular velocity ω of the spacecraftkGo on to aboutBundles, require special attention to distinguish in order to avoid ambiguity.
Controlling torque constraint:
and because the spacecraft system is in a discrete system form, the angular accelerationCan be approximated in the following form:
the control torque constraint can be written approximately as:
simplifying the above formula, can convert control moment restraint into the form of angular velocity restraint, the concrete form is as follows:
wherein the content of the first and second substances,respectively providing minimum and maximum control moments for the spacecraft actuating mechanism in the directions of all main shafts;the optimal estimated value of the angular rate of the spacecraft at the previous moment is obtained; t issThe time interval is sampled for a discrete system. Similarly, it should be noted that the constraint equation (13) is the optimal angular velocity estimated by the rolling time domain online estimation algorithmFor constraining, not for spacecraftActual operating angular velocity ωkAnd (6) carrying out constraint.
Combining the angular velocity constraint (9) and the control moment constraint (13), two constraints can be simplified as:
at this time, the constrained rolling horizon optimization problem can be written as follows:
3) at the time T, if the redundant fiber optic gyroscope after data processing is combined with the angular speed measurement output sequenceOrAnd spacecraft attitude control moment sequenceOrKnown, therein for arbitrary variablesSequence ofTo representThe optimization problem (15) can be solved using a multiple targeting method to obtain a unique existing optimal solution
4) At time T, the specific steps for solving the optimization problem (15) by using the multiple targeting method are as follows:
firstly, the angular momentum pi of the spacecraft is used herek=JωkReplacing spacecraft angular velocity omegakThe optimization problem (15) can be equivalently transformed into the form of the following optimization problem (16):
wherein, Yk=JykFrom the spacecraft angular velocity measurement y for time kkCalculating the angular momentum of the spacecraft;3, estimating values of angular momentum of each main shaft of the spacecraft at the moment k; respectively the minimum and maximum angular momentum of each main shaft of the spacecraft; equation (16c) is solving for the auxiliary variablesAn implicit equation of (c);
considering system dynamics equality constraint (16b) and angular momentum time domain inequality constraint (16d), defining an augmented objective function:
wherein the content of the first and second substances,is a Lagrangian multiplier,. mu. > 0 andin order to be a penalty parameter,the penalty function for the corresponding inequality constraint (16d) is expressed in the following way:
when T is larger than N, the broadening cost function is subjected to variation by using a variation method, wherein the variation expression is as follows:
wherein the content of the first and second substances,as a penalty functionTo pairFirst order variational sum, variational coefficientAs follows:
wherein e isiI is 1,2 and 3 are unit vectors of main axes of inertia of the spacecraft respectively;
let δ ΦTaThe first order requirement for the 0 available optimization problem (16) is as follows:
wherein the content of the first and second substances,
the following first order requirements can be met by modifying equation (21):
wherein the content of the first and second substances,for the vectors to be solved of the first order requirement, by lagrange multiplier sequenceAnd spacecraft angular momentum estimation sequenceComposition is carried out;
at this time, solving the optimization problem (16) can be equivalently converted into solving the root of the first-order requirement (22), namely, the root of the first-order requirement and the optimal solution of the optimization problem are the same, and the numerical iteration solving is carried out on the formula (22) by adopting a multiple targeting method, namely, a group of specific sequences s is required to be found*So that Fs(s*)=06N+3If the first order requirement (22) has a root and is unique, the root is the optimal solution of the optimization problem (16);
the root-finding iterative relationship in the multiple targeting method is as follows:
si+1=si+κΔ(s)i(23)
wherein s isi+1For the i +1 th iterative solution, siFor the ith iterative solution,. kappa.. epsilon. (0, 1)]In order to iterate the step size,for iterative descending direction, Δ(s)iIn (1)A Jacobian matrix of formula (22);
a variational expression according to equation (22):
wherein, the coefficient matrix corresponding to each formula is as follows:
thus, the formula (2) can be obtained from the formula (24) to the formula (28)2) Jacobian matrix ofThe following were used:
the iteration termination condition in the algorithm flow is as follows:
||Fs(s)||≤σ (30)
wherein σ is the acceptable iteration precision error;
to this end, the root of the first order requirement (22) can be solved by the above stepsThen passing through the relation lambdak=Q1wkAn optimal solution of the optimization problem (16) is obtainedThen passing through relation IIk=JωkAn optimal solution of the optimization problem (15) can be obtained
When T is less than or equal to N, namely when the full information rolling time domain estimation is considered, the root of the first-order requirement (22) can be solved by only making all T-N in the algorithm steps equal to 0Further by the relation lambdak=Q1wkAn optimal solution of the optimization problem (16) is obtainedThen passing through relation IIk=JωkCan be optimizedOptimal solution of problem (15)
5) At the time T, the optimal solution of the step 4) can be obtainedOrAnd attitude control moment sequenceOrSubstituting the attitude dynamics and the kinematic equation of the discrete spacecraft into iteration and recursion to obtain the optimal estimated value of the angular velocity of the spacecraft at the current moment
6) Calculating the next time estimation error covariance P according to the formula (8)T-N+1;
7) At the next time T + 1, the data sequence is updated with the latest measured value and the latest control torque, and T: ═ T +1 is defined, returning to step 2).
The optimal online estimation of the angular velocity of the spacecraft can be completed through the steps.
Compared with the prior art, the invention has the advantages that:
(1) the method describes the attitude dynamics and the kinematics equation of the discrete spacecraft by introducing a special orthogonal group SO (3), the kinematics equation uses multiplication of two rotation matrixes to describe the rotation motion of the spacecraft in a popular and understandable way and greatly simplify the calculation amount of the attitude motion of the spacecraft, and simultaneously compared with the traditional quaternion description method and the Euler angle description method, the constraint problem in the quaternion method and the singular point problem in the Euler angle method are avoided.
(2) Different from the conventional angular velocity estimation method, compared with the classical Kalman filtering, the estimation method of the angular velocity of the spacecraft based on the rolling time domain estimation provided by the invention has the advantages that on one hand, the state estimation is carried out by fully utilizing the system information and the measurement information in the current and past periods, more information is considered, and the estimation precision is further improved; on the other hand, angular velocity constraint and control moment constraint of the spacecraft system are considered and are directly expressed in an optimization problem, and the optimization is dynamically satisfied through online rolling optimization; and the optimization problem is solved in a limited time domain by adopting the approximate arrival cost function, so that the solving time of the optimization problem is shortened. The rolling time domain estimation method is an estimation method which can solve the optimization problem including constraint conditions, and is high in reliability, accurate and effective.
(3) In the optimal problem solving algorithm, the optimization problem in a limited time domain is solved by adopting a multiple shooting method, compared with other optimal algorithms, the algorithm can process a rigid problem and can adopt a parallel framework, and the method has the characteristics of high calculation efficiency and good operation effect, so that the solving efficiency and precision are improved, and the real-time requirement of a spacecraft system is met.
Drawings
Fig. 1 is a schematic block diagram of the method for estimating the angular velocity of a spacecraft based on rolling time domain estimation according to the present invention.
Fig. 2 is a schematic diagram of the rolling time domain estimation method of the present invention.
Fig. 3 is a flow chart of the method for estimating the angular velocity of a spacecraft based on rolling time domain estimation according to the present invention.
FIG. 4 is a flow chart of the multiple targeting algorithm of the present invention to solve the optimization problem.
Detailed Description
As shown in fig. 1, the spacecraft angular velocity estimation method of the present invention is a rolling time domain estimation method considering the spacecraft angular velocity physical constraint and the control moment constraint. At each sampling moment, the optimal angular velocity estimation value obtained by the estimation method can be fed back to the controller, and the controller generates a control moment to act on the spacecraft interfered by the external moment by using the optimal estimation value to complete attitude stabilization or attitude maneuver; the redundant fiber optic gyroscope is combined with the angular velocity of the sensitive spacecraft, new weighted data fusion processing is carried out on four paths of twelve-dimensional measurement signals with measurement noise on the basis of fault failure factor distribution, and the new weighted data fusion processing and the control moment signals are input into a rolling time domain estimator, so that the real-time, reliable, accurate and efficient estimation of the triaxial angular velocity of the spacecraft is completed; and pushing the latest measured value and the latest control moment value into the data sequence at the next sampling moment to finish updating the data sequence, thereby forming a closed loop structure.
As shown in fig. 2, the rolling time domain estimation algorithm of the present invention is derived from the analysis of a rolling time domain window, each time only uses the latest first N data at the current time T, and the influence of the rest of the measurement data on the estimation can be described by an arrival cost function; at the next moment, the rolling time domain window is shifted backwards by one sampling time, and the data sequence is updated to the latest first N data at the current T +1 moment.
It should be understood that in this context, spacecraft angular velocities describe "vectors" and spacecraft angular velocities describe "scalars", i.e. angular velocities refer to (ω)x,ωy,ωz) Angular rate refers to the angular rate ω of a certain principal axis of inertiaxOr ωyOr ωzAnd the three-axis angular rate refers to ωx,ωy,ωzThree scalars.
As shown in fig. 3, the method for estimating the angular velocity of a spacecraft based on rolling time domain estimation of the present invention includes the steps of: firstly, constructing a state equation and a measurement equation which can be used for a rolling time domain estimation strategy based on a discrete spacecraft attitude dynamics and kinematics model; then, carrying out new weighted data fusion of weight values distributed based on fault failure factors on four paths of twelve-dimensional angular rate signals sensed by the combination of the redundant fiber optic gyroscopes to obtain angular rate measured values of all inertial main shafts under a spacecraft body coordinate system; and finally, according to the state equation, the measurement equation, the angular velocity measurement sequence and the controller input sequence, simultaneously considering the angular velocity constraint and the control moment constraint of the spacecraft, and performing online estimation by using a rolling time domain estimation strategy and a multiple target shooting method to obtain the optimal estimation of the angular velocity of the spacecraft. The specific operation steps are as follows:
firstly, aiming at the problem of spacecraft angular velocity estimation, a state equation and an observation equation of the spacecraft angular velocity are constructed based on a spacecraft dynamics model in a special orthogonal group SO (3) description mode. The spacecraft dynamics model under the special orthogonal group SO (3) description mode is as follows:
Rk+1=RkFk(2)
wherein h is a sampling time interval; superscript T represents matrix transposition; the index k denotes the kth sampling instant; matrix Rk,FkE SO (3) is a rotation matrix,a rotation matrix representing the euler attitude angle description of the spacecraft,a rotation matrix representing the description of the Euler attitude error angle of the spacecraft between two sampling instants, FkIs the solution of implicit equation (1);denotes the overall angular momentum of the spacecraft, J ═ diag ([2.5, 2.5)])kg·m2A matrix of the inertia of the spacecraft is represented,representing the three-axis angular velocity of the spacecraft;the method comprises the following steps of representing external disturbance moment caused by gravity gradient moment, aerodynamic resistance, sunlight pressure and the like to which a spacecraft is subjected;representing the control moment required by the attitude maneuver or the stability of the spacecraft; positive definite arrayRepresents a non-standard inertia matrix, which is related to the inertia matrix J;is about real vectorFor any vectorIts corresponding oblique antisymmetric array x×The form is as follows:
based on the discrete spacecraft attitude dynamics model, a state equation and an observation equation for rolling time domain estimation can be constructed as follows:
taking the system state quantity as omega ═ omegax,ωy,ωz)TThen the state equation is
Wherein ω ═ ω (ω ═ ω)x,ωy,ωz)TIs the spacecraft angular velocity; fkThe epsilon SO (3) is an auxiliary variable and represents the relative attitude between two adjacent moments;is system external interference, independent of measurement noise and initial state;
taking the observed quantity of the system as y ═ yx,yy,yz)TThen the observation equation is
Jyk=CJωk+νk(5)
Wherein y ═ yx,yy,yz)TMeasuring data output value, y, for redundant fiber optic gyroscopes combined data processed angular velocityx,yy,yzMeasuring the angular rate of each inertia main shaft of the spacecraft;for noise measurement, it is independent of system external interference and initial state; measurement matrix C ═ I3×3Is an identity matrix;
secondly, because the observation equation needs three-dimensional measurement data, and the combination of the redundant fiber optic gyroscopes feels that the combination of the redundant fiber optic gyroscopes is four-way twelve-dimensional measurement data, a new weighted data fusion method for distributing weights based on failure factors needs to be designed:
wherein the content of the first and second substances,for the spacecraft angular velocity measurement data after data processing, it should be noted that y here1,y2,y3And y mentioned abovex,yy,yzBeing the same quantity, the above observation equation requires three-dimensional angular rate measurements, whereas redundant fiber optic gyroscopes are sensitive to four-way twelve-dimensional angular rate measurements, so that from twelve-dimensional to three-dimensional data processing is required for use with the above observation equation.The angular velocity information of the spacecraft sensed by the ith optical fiber gyroscope in the redundant optical fiber gyroscopes is measured by four paths of twelve-dimensional angular velocity measurement informationα1=45°,α2=135°,α3=225°,α4315 degrees are respectively the installation deflection angles of four optical fiber gyroscopes, and represent the included angle between the projection of the axial direction of the ith optical fiber gyroscope on the xoy plane and the ox axis, βi54.75 degrees, and i is 1,2,3 and 4 respectively representing the installation high and low angles of the four optical fiber gyroscopes, and representing the included angle between the axial direction of the ith optical fiber gyroscope and the xoy plane;as a weighting factor, influenced by the failure factor of the ith optical fiber gyroscope, where ρ is takeni1, i is 1,2,3,4, so the weighting factor is τi=0.25,i=1,2,3,4τi=0.25,i=1,2,3,4;
And thirdly, performing optimal estimation on the angular velocity of the spacecraft by using a rolling time domain estimation algorithm on the basis of the first step and the second step, wherein the method specifically comprises the following steps:
1) a priori estimation of initial state assuming a known systemCovariance matrix of initial state error is P0=diag([1,1,1]) The weight matrix of the external interference and the measured noise of the system is Q1=diag([100,100,100]),Q2=diag([1000,1000,1000]) And P is0,Q1,Q2All the time zones are positive definite matrixes, and the length of a rolling time domain is N-5;
2) at time T, the optimization problem defined by the rolling time domain estimation is as follows:
wherein the content of the first and second substances,in order to achieve the cost function, the invention adopts the arrival cost function of an unconstrained linear system to approximate the cost function of a constrained nonlinear system, namely the approximate arrival cost function has the following form:
in the formula, initial state estimationObey normal distributionPT-N is the estimation error covariance, updated by equation (8) below;
meanwhile, the objective function needs to satisfy spacecraft dynamics, spacecraft angular velocity time domain constraint and control moment constraint, and the specific mathematical expression form is as follows:
angular velocity time domain constraint:
wherein the content of the first and second substances,for the angular rate estimate obtained by the rolling time domain estimation,the minimum and maximum angular velocities allowed by the main axes of the spacecraft are determined by the properties of physical devices such as solar sailboards, sensors and the like installed on the spacecraft. It should be noted that the angular velocity time domain constraint proposed herein is the optimal angular velocity estimated by the rolling time domain online estimation algorithmConstraining rather than imposing an actual operating angular velocity ω of the spacecraftkTo make the constraints, special care needs to be taken to distinguish in order to avoid ambiguity.
Controlling torque constraint:
and because the spacecraft system is in a discrete system form, the angular accelerationCan be approximated in the following form:
the control torque constraint can be written approximately as:
simplifying the above formula, can convert control moment restraint into the form of angular velocity restraint, the concrete form is as follows:
wherein the content of the first and second substances,respectively providing minimum and maximum control moments for the spacecraft actuating mechanism in the directions of all main shafts; t iss0.01s is a discrete system sampling time interval;the optimal estimated value of the angular velocity of the spacecraft at the previous moment is obtained. Similarly, it should be noted that the constraint equation (13) is the optimal angular velocity estimated by the rolling time domain online estimation algorithmConstraining rather than imposing an actual operating angular velocity ω of the spacecraftkAnd (6) carrying out constraint.
Combining the angular velocity constraint (9) and the control moment constraint (13), two constraints can be simplified as:
at this time, the constrained rolling horizon optimization problem can be written as follows:
3) at the time T, if the redundant fiber optic gyroscope after data processing is combined with the angular speed measurement output sequenceOrAnd spacecraft attitude control moment sequenceOrIf known, the optimization problem (15) can be solved by using a multiple targeting method, and the only existing optimal solution can be solved
4) At time T, the specific steps for solving the optimization problem (15) by using the multiple targeting method are as follows:
firstly, the angular momentum pi of the spacecraft is used herek=JωkReplacing spacecraft angular velocity omegakThe optimization problem (15) can be equivalently written in the form of the following optimization problem (16):
wherein, Yk=JykFrom the spacecraft angular velocity measurement y for time kkThe angular momentum of the spacecraft is obtained by calculation,for the estimated value of the angular momentum of each main shaft of the spacecraft at the moment k, respectively the minimum and maximum angular momentum of each main shaft of the spacecraft, and the formula (16c) is used for solving auxiliary variablesImplicit equation of (2).
Considering system dynamics equality constraint (16b) and angular momentum time domain inequality constraint (16d), defining an augmented objective function:
wherein the content of the first and second substances,is a Lagrangian multiplier,. mu. > 0 andin order to be a penalty parameter,the penalty function for the corresponding inequality constraint (16d) is expressed in the following way:
wherein h is 0.01, which is the time interval between two moments;
when T is larger than N, the broadening cost function is subjected to variation by using a variation method, wherein the variation expression is as follows:
wherein the content of the first and second substances,as a penalty functionTo pairFirst order variational sum, variational coefficientAs follows:
let δ ΦTaThe first order requirement for the 0 available optimization problem (16) is as follows:
wherein the content of the first and second substances,
the following first order requirements can be met by modifying equation (21):
wherein the content of the first and second substances,for the vectors to be solved of the first order requirement, by lagrange multiplier sequenceAnd spacecraft angular momentum estimation sequenceComposition is carried out;
at this point, solving the optimization problem (16) can be equivalently transformed into solving the root of the first order requirement (22), i.e., the root of the first order requirement is the same as the optimal solution of the optimization problem. The numerical iterative solution of equation (22) using multiple targeting is to find a specific set of sequences s*So that Fs(s*)=06N+3If the first order requirement (22) has a root and is unique, the root is the optimal solution of the optimization problem (16);
the flow of the multiple targeting algorithm is shown in fig. 4, and the root-finding iterative relationship in the algorithm is as follows:
si+1=si+κΔ(s)i(23)
wherein s isi+1For the i +1 th iterative solution, siFor the ith iterative solution,. kappa.. epsilon. (0, 1)]In order to iterate the step size,for iterative descending direction, Δ(s)iIn (1)A Jacobian matrix of formula (22);
a variational expression according to equation (22):
wherein, the coefficient matrix corresponding to each formula is as follows:
therefore, the Jacobian matrix of formula (22) can be obtained from formula (24) to formula (28)The following;
the iteration termination condition in the algorithm flow is as follows:
||Fs(s)||≤σ (30)
wherein, σ is 0.00001 as iteration precision error;
to this end, the root of the first order requirement (22) can be solved by the above stepsThen passing through the relation lambdak=Q1wkAn optimal solution of the optimization problem (16) is obtainedThen passing through relation IIk=JωkAn optimal solution of the optimization problem (15) can be obtained
When T is less than or equal to N, namely when the full information rolling time domain estimation is considered, the root of the first-order requirement (22) can be solved by only making all T-N in the algorithm steps equal to 0Further by the relation lambdak=Q1wkAn optimal solution of the optimization problem (16) is obtainedThen passing through relation IIk=JωkAn optimal solution of the optimization problem (15) can be obtained
5) At time T, the optimal solution of the steps can be obtainedOrAnd attitude control moment sequenceColumn(s) ofOrSubstituting the attitude dynamics and the kinematic equation of the discrete spacecraft into iteration and recursion to obtain the optimal estimated value of the angular velocity of the spacecraft at the current moment
6) Calculating the next time estimation error covariance P according to the formula (8)T-N+1;
7) At the next time T + 1, updating the data sequence by using the latest measured value and the latest control torque, defining T: (T + 1), and returning to the step 2);
the optimal online estimation of the angular velocity of the spacecraft can be completed through the steps.
Those skilled in the art will appreciate that the invention may be practiced without these specific details.
Claims (1)
1. A spacecraft angular velocity estimation method based on rolling time domain estimation is characterized by comprising the following steps:
s1: constructing a state equation and an observation equation of the angular velocity of the spacecraft based on a spacecraft dynamics model in a special orthogonal group SO (3) description mode;
the spacecraft dynamics model under the special orthogonal group SO (3) description mode is as follows:
Rk+1=RkFk(2)
wherein h is a sampling time interval; superscript T represents matrix transposition;the index k denotes the kth sampling instant; matrix Rk,FkE SO (3) is a rotation matrix,a rotation matrix representing the euler attitude angle description of the spacecraft,a rotation matrix representing the description of the Euler attitude error angle of the spacecraft between two sampling instants, FkIs the solution of implicit equation (1);which represents the angular momentum of the spacecraft, is an inertial matrix of the spacecraft,the angular velocity of the spacecraft at the kth sampling moment; representing external disturbance moments caused by external disturbances including gravity gradient moments, aerodynamic drag, sunlight pressure, to which the spacecraft is subjected;representing the control moment required by the attitude maneuver or the stability of the spacecraft; positive definite arrayRepresenting non-standard inertia matricesIt is related to the inertia matrix J;is about real vectorFor any vectorIts corresponding oblique antisymmetric array x×The form is as follows:
the state equation and the observation equation for rolling time domain estimation are constructed based on a spacecraft dynamics model as follows:
taking the system state quantity as spacecraft angular velocity omega ═ omegax,ωy,ωz)TThen the state equation is
Taking the system observed quantity as the angular velocity measurement data output value y after the redundant fiber-optic gyroscope combined data is processed (y ═ y)x,yy,yz)TThen the observation equation is
Jyk=CJωk+νk(5)
Wherein, yx,yy,yzMeasuring the angular rate of each inertia main shaft of the spacecraft;andrespectively system external interference and measurement noise;is a measurement matrix;
s2: simplifying four-way twelve-dimensional angular rate measurement information combined by redundant fiber optic gyroscopes by using a new weighted data fusion method for distributing weights based on failure factors to obtain spacecraft three-axis angular rate measurement data;
the new weighted data fusion method for distributing the weight value based on the failure factor comprises the following steps:
wherein the content of the first and second substances,the angular velocity information of the spacecraft sensed by the ith optical fiber gyroscope in the redundant optical fiber gyroscopes,for four-way twelve-dimensional angular rate measurement information αiWherein i is 1,2,3 and 4 is the installation deflection angle of the optical fiber gyroscope and represents the included angle between the projection of the axial direction of the ith optical fiber gyroscope on the xoy plane and the ox axis, βiThe i is 1,2,3 and 4, which is the installation high-low angle of the optical fiber gyroscope and represents the included angle between the axial direction of the ith optical fiber gyroscope and the xoy plane;as a weighting factor, the failure factor ρ of the ith optical fiber gyroscopei∈[0,1]Influence and need to satisfy the constraint τ1+τ2+τ3+τ4=1;
S3: based on the state equation and the observation equation constructed in the step S1 and the spacecraft triaxial angular rate measurement data obtained in the step S2, considering spacecraft angular velocity constraint and control moment constraint, and performing online estimation by using a rolling time domain estimation strategy and a multiple target shooting method to obtain an estimated value of the optimal angular velocity of the spacecraft at the current moment;
the specific steps of on-line estimation by using a rolling time domain estimation strategy and a multiple target practice method are as follows:
1) a priori estimation of initial state assuming a known systemCovariance matrix of initial state error is P0The weight matrix of the external interference and the measured noise of the system is Q1,Q2And P is0,Q1,Q2All are positive definite matrixes, and the length of a rolling time domain is N;
2) at time T, the optimization problem defined by the rolling time domain estimation is as follows:
in the two cases, the first term in the objective function represents the cost sum of external interference of the system at each sampling moment, the second term represents the cost sum of measurement noise at each sampling moment, and the third term represents prior estimation when T is less than or equal to NDegree of trust of, at T>When the N is greater than the N value,to approximate the arrival cost function, which represents the influence of the remaining measurement data on the estimation, the arrival cost function of the unconstrained linear system is used to approximate the cost function of the constrained nonlinear system, i.e., the approximate arrival cost function is of the form:
in the formula, initial state estimationObey normal distributionPT-NTo estimate the error covariance, it can be updated by the following equation (8);
meanwhile, the objective function needs to satisfy spacecraft dynamics, spacecraft angular velocity time domain constraint and control moment constraint, and the specific mathematical expression form is as follows:
angular velocity time domain constraint:
wherein the content of the first and second substances,for the angular rate estimate obtained by the rolling time domain estimation,the minimum and maximum angular rates allowed by each main shaft of the spacecraft are determined by the properties of physical devices including a solar panel and a sensor which are arranged on the spacecraft;
controlling torque constraint:
and because the spacecraft system is in a discrete system form, the angular accelerationCan be approximated in the following form:
the control torque constraint can be written approximately as:
simplifying the above formula, can convert control moment restraint into the form of angular velocity restraint, the concrete form is as follows:
wherein the content of the first and second substances,respectively providing minimum and maximum control moments for the spacecraft actuating mechanism in the directions of all main shafts;the optimal estimated value of the angular rate of the spacecraft at the previous moment is obtained; t issSampling a time interval for a discrete system;
combining the angular velocity constraint (9) and the control moment constraint (13), two constraints can be simplified as:
at this time, the constrained rolling horizon optimization problem can be written as follows:
3) at the time T, if the redundant fiber optic gyroscope after data processing is combined with the angular speed measurement output sequenceOrAnd spacecraft attitude control moment sequenceOrKnown, therein for arbitrary variablesSequence ofTo representThe optimization problem (15) can be solved using a multiple targeting method to obtain a unique existing optimal solution
4) At time T, the specific steps for solving the optimization problem (15) by using the multiple targeting method are as follows:
firstly, the angular momentum pi of the spacecraft is used herek=JωkReplacing spacecraft angular velocity omegakThe optimization problem (15) can be equivalently transformed into the form of the following optimization problem (16):
wherein, Yk=JykFrom the spacecraft angular velocity measurement y for time kkCalculating the angular momentum of the spacecraft;3, estimating values of angular momentum of each main shaft of the spacecraft at the moment k; respectively the minimum and maximum angular momentum of each main shaft of the spacecraft; equation (16c) is solving for the auxiliary variablesThe implicit equation of (a) is,
considering system dynamics equality constraint (16b) and angular momentum time domain inequality constraint (16d), defining an augmented objective function:
wherein the content of the first and second substances,is a Lagrangian multiplier,. mu. > 0 andin order to be a penalty parameter,the penalty function for the corresponding inequality constraint (16d) is expressed in the following way:
when T is larger than N, the broadening cost function is subjected to variation by using a variation method, wherein the variation expression is as follows:
wherein the content of the first and second substances,as a penalty functionTo pairFirst order variational sum, variational coefficientAs follows:
wherein e isiI is 1,2 and 3 are unit vectors of main axes of inertia of the spacecraft respectively;
let δ ΦTaThe first order requirement for the 0 available optimization problem (16) is as follows:
wherein the content of the first and second substances,
the following first order requirements can be met by modifying equation (21):
wherein the content of the first and second substances,for the vectors to be solved of the first order requirement, by lagrange multiplier sequenceAnd spacecraft angular momentum estimation sequenceComposition is carried out;
at this time, solving the optimization problem (16) can be equivalently converted into solving the root of the first-order requirement (22), namely, the root of the first-order requirement and the optimal solution of the optimization problem are the same, and the numerical iteration solving is carried out on the formula (22) by adopting a multiple targeting method, namely, a group of specific sequences s is required to be found*So that Fs(s*)=06N+3If the first order requirement (22) is rooted and unique, then the root is the optimization problem (16)) The optimal solution of (2);
the root-finding iterative relationship in the multiple targeting method is as follows:
si+1=si+κΔ(s)i(23)
wherein s isi+1For the i +1 th iterative solution, siFor the ith iterative solution,. kappa.. epsilon. (0, 1)]In order to iterate the step size,for iterative descending direction, Δ(s)iIn (1)A Jacobian matrix of formula (22);
a variational expression according to equation (22):
wherein, the coefficient matrix corresponding to each formula is as follows:
therefore, the Jacobian matrix of formula (22) can be obtained from formula (24) to formula (28)The following were used:
the iteration termination condition in the algorithm flow is as follows:
||Fs(s)||≤σ (30)
wherein σ is the acceptable iteration precision error;
to this end, the root of the first order requirement (22) can be solved by the above stepsThen passing through the relation lambdak=Q1wkAn optimal solution of the optimization problem (16) is obtainedThen passing through relation IIk=JωkAn optimal solution of the optimization problem (15) can be obtained
When T is less than or equal to N, namely when the full information rolling time domain estimation is considered, the root of the first-order requirement (22) can be solved by only making all T-N in the algorithm steps equal to 0Further by the relation lambdak=Q1wkAn optimal solution of the optimization problem (16) is obtainedThen passing through relation IIk=JωkAn optimal solution of the optimization problem (15) can be obtained
5) At time T, canOptimal solution of step 4)OrAnd attitude control moment sequenceOrSubstituting the attitude dynamics and the kinematic equation of the discrete spacecraft into iteration and recursion to obtain the optimal estimated value of the angular velocity of the spacecraft at the current moment
6) Calculating the next time estimation error covariance P according to the formula (8)T-N+1;
7) At the next time T +1, the data sequence is updated with the latest measured value and the latest control torque, and T: ═ T +1 is defined, and the process returns to step 2.
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