Method for maintaining regression orbit in high-precision gravitational field based on monopulse orbit control
阅读说明：本技术 一种基于单脉冲轨控的高精度引力场中回归轨道维持方法 (Method for maintaining regression orbit in high-precision gravitational field based on monopulse orbit control ) 是由 何艳超 张磊 王敏锋 徐�明 孙晓函 吕秋杰 谢松 于灵慧 于 2020-06-15 设计创作，主要内容包括：本发明公开了一种基于单脉冲轨控的高精度引力场中回归轨道维持方法,包括：构建高阶Poincaré映射和求解回归轨道初值的多目标优化函数,求解得到第一个回归轨道初值；对第一个回归轨道初值进行轨道积分,得到轨道状态量；根据轨道状态量,对高阶Poincaré映射进行重构,求解得到下一个回归轨道初值；根据轨道状态量与下一个回归轨道初值的速度差值,确定轨道控制所需要的单脉冲速度增量,实现对高精度引力场中回归轨道的维持。本发明在轨道设计作为标称值的基础上,通过在赤道升交点处施加速度脉冲使相邻回归周期内的轨道速度状态相连,从而实现高精度轨道控制,可使卫星实际星下点轨迹偏离标称位置距离在用户设定的阈值范围内。(The invention discloses a method for maintaining a regression orbit in a high-precision gravitational field based on monopulse orbit control, which comprises the following steps: constructing high-order Poincar é mapping and solving a multi-objective optimization function of the regression orbit initial value, and solving to obtain a first regression orbit initial value; performing orbit integration on the first regression orbit initial value to obtain an orbit state quantity; reconstructing the high-order Poincar é mapping according to the track state quantity, and solving to obtain the initial value of the next regression track; and determining the monopulse speed increment required by the track control according to the speed difference value between the track state quantity and the next regression track initial value, and realizing the maintenance of the regression track in the high-precision gravitational field. On the basis of taking the orbit design as a nominal value, the invention applies acceleration pulses at the ascending and crossing points of the equator to connect the orbit speed states in adjacent regression cycles, thereby realizing high-precision orbit control and ensuring that the actual subsatellite point orbit of the satellite deviates from the nominal position by the distance within the threshold range set by a user.)
1. A method for maintaining a regression orbit in a high-precision gravitational field based on monopulse orbit control is characterized by comprising the following steps:
constructing a high-order Poincar mapping of the change of the orbit state of the satellite after a regression period from the initial state;
constructing a multi-objective optimization function for solving the regression orbit initial value;
solving to obtain a first regression orbit initial value according to the high-order Poincar é mapping and the multi-objective optimization function;
performing orbit integration on the first regression orbit initial value to obtain an orbit state quantity;
reconstructing the high-order Poincar é mapping according to the track state quantity to obtain reconstructed high-order Poincar mapping;
constructing a control target optimization function;
solving to obtain a next regression orbit initial value according to the reconstructed high-order Poincar é mapping and the control target optimization function;
determining the single pulse speed increment required by the track control according to the speed difference value between the track state quantity and the initial value of the next regression track;
and maintaining the regression orbit in the high-precision gravitational field according to the determined monopulse speed increment required by the orbit control.
2. The method for maintaining the regression orbit in the high-precision gravitational field based on the monopulse orbit control as claimed in claim 1, wherein constructing a high-order poincare map of the orbit state change of the satellite after a regression period from the initial state comprises:
establishing a regression orbit design coordinate system; wherein, regressing the track design coordinate system, includes: an earth center inertial coordinate system and an earth center earth fixed coordinate system;
setting a regression orbit condition according to the precision requirement of task realization; wherein, the regression orbit condition comprises: a strict precision condition indicating that the track returns to the initial state within one regression cycle and a loose precision condition indicating that the track can return to the initial state within a plurality of regression cycles;
and constructing a high-order Poincar mapping of the change of the orbit state of the satellite after a regression period from the initial state.
3. The method for maintaining the regression orbit in the high-precision gravitational field based on monopulse orbit control as claimed in claim 2,
geocentric inertial coordinate system: the substantially plane is the equatorial plane,the axis points to the spring point from the center of the earth,
geocentric coordinate system:the axis is from the center of the earth along the intersection of the equatorial plane and the meridian plane,
the angular velocity of the earth center earth-fixed coordinate system rotating relative to the earth center inertial coordinate system is the earth rotation angular velocity omegaE。
4. The method for maintaining the regression orbit in the high-precision gravitational field based on the monopulse orbit control as claimed in claim 2, wherein constructing the high-order poincare map of the orbit state change of the satellite after a regression period from the initial state comprises:
taking the regression mode of the regression orbit as nM:nN(ii) a Wherein n isMDenotes the regression period, nNRepresenting the number of track turns in a regression period;
the state quantities x, y, vx、vy、vzAnd initializing the regression period T into a differential algebraic variable, and performing track recursion under a complete gravity perturbation model to obtain a high-order Taylor expansion formula of high-order Poincare mapping:
wherein x and y represent the earth center earth fixed coordinate of the satelliteIs a system
by solving the formula (4), the T degree of freedom is eliminated, i.e., X satisfying the formula (3)fFraction z is 0:
wherein z isfRepresenting the track in the geocentric geostationary coordinate system after a time TCoordinate values on the axis;
based on differential algebraic operation, we can:
substituting formula (5) back to formula (3) can yield:
5. the method for maintaining the regression orbit in the high-precision gravitational field based on the monopulse orbit control as claimed in claim 4, wherein a high-order Poincare map of the orbit state change of the satellite after a regression period from the initial state is constructed, further comprising:
when differential algebra operation is carried out, a transformation matrix from a geocentric inertial coordinate system to a geocentric coordinate system is calculated
In calculating the transformation matrixWhen considering the effects of nutation and polar motion of the earth, a first order approximation is performed by equation (7), and the transformation matrix is expressed as a differential algebraic form:
wherein the content of the first and second substances,
6. The method for maintaining the regression orbit in the high-precision gravitational field based on the monopulse orbit control as claimed in claim 4, wherein the solving to obtain the first regression orbit initial value according to the high-order Poincare mapping and the multi-objective optimization function comprises:
determining a multi-objective optimization function for solving the regression orbit initial value:
where v represents the amount of speed deviation from the initial guess, x0And v0Respectively representing the initial position and initial velocity, x, of the satellitefAnd vfRespectively representing the satellite's terminal position and velocity at the point of intersection after one or more regression cycles,
the orbital state quantity [ x, y,0, v ] represented by the formula (6)x,vy,vz]TSubstituting in an equation (8), and solving to obtain an optimization result through an optimization method;
and determining a design initial value of the regression orbit according to the optimization result.
7. The method for designing the regression orbit in the high-precision gravitational field according to claim 6, wherein the optimization result satisfies the following conditions: satisfy the sun synchronization characteristics and satisfy the initial guess [ x0,v0]T＝[x0,y0,0,vx0,vy0,vz0]TCorrection amount v of0＝[vx0,vy0,vz0]TAnd minimum.
8. The method of claim 7, wherein the regression trajectory in the high precision gravitational field is designed,
v | ═ 0, for assuranceAnd minimum.
9. The method for designing the regression orbit in the high-precision gravitational field according to claim 8, wherein the first regression orbit initial value obtained by solving is represented as: [ x ] of0,y0,0,vx0+vx0,vy0+vy0,vz0+vz0]T。
10. The method of claim 2, wherein the regression trajectory design in high precision gravitational field is characterized in that,
when the regression orbit condition is a strict precision condition, the control target optimization function is as follows:
J＝|v|2
when the regression orbit condition is a loose precision condition, the control target optimization function is as follows:
wherein x istDenotes a distance threshold value, vtIs indicative of a threshold value of the speed,
Technical Field
The invention belongs to the technical field of satellite task analysis and orbit design, and particularly relates to a method for maintaining a regression orbit in a high-precision gravitational field based on monopulse orbit control.
Background
The regression orbit is used as a special task application orbit of a near-earth orbit, and due to the characteristic that the track of the sub-satellite points is completely repeated at a certain time interval, the orbit is widely applied to tasks such as remote sensing to the earth, reconnaissance and survey and the like.
The orbit control technology is an important component in the technical field of satellite task analysis and orbit design. Due to the perturbation action in the space environment, especially the non-conservative force such as atmospheric resistance will cause the drift of the track of the point under the satellite. Absent the necessary trajectory maintenance control, a long-running regression trajectory will lose its regression characteristics in the real space environment. For any space mission using a return orbit, one major problem is that when the spacecraft deviates from the reference orbit by a certain extent, periodic control needs to be applied to restore to the return orbit condition, otherwise an increase in the deviation will cause the mission to fail.
In order to solve the problem, some scholars propose methods for specific tracking targets on the basis of track design. Considering the onboard equipment system and the ground station processing capability, the multi-pulse autonomous control strategy proposed by Aorpimai and Palmer can configure the spacecraft from an initial condition to a return orbit condition. Based on the semi-analytical method, Sengupta et al studied J2The control problem of the return orbit with small eccentricity covered on the ground under the action of perturbation and atmospheric resistance. Aiming at the problem of maintaining continuous coverage of a regression orbit on the ground, Fu and the like analyze the drift amount of the whole track of the point under the satellite based on latitude argument and provide a method for maintaining the track drift not to exceed a given threshold valueAnd (5) controlling the strategy.
Most of the research at home and abroad aiming at the regression orbit control method is to consider a unilateral limit cycle control method to counteract the influence of atmospheric resistance on the orbit drift of the point under the satellite on the basis of the design aiming at the orbit in the low-order gravitational field. In order to ensure the long-term stable on-orbit operation of the satellite, the design value of the orbit in the high-precision gravitational field is required to be used as a nominal orbit, and a method for realizing the regression orbit control in the high-precision gravitational field is designed, so that the distance of the orbit of the satellite point under the satellite deviating from the nominal position meets the threshold range given by a user.
Disclosure of Invention
The technical problem of the invention is solved: the method is characterized in that on the basis that the orbit design is used as a nominal value, acceleration pulses are applied to the ascending and crossing points of the equator to enable the orbit speed states in adjacent regression cycles to be connected, so that high-precision orbit control is achieved, and the deviation of the actual subsatellite point trajectory of the satellite from the nominal position is within a threshold range set by a user.
In order to solve the technical problem, the invention discloses a method for maintaining a regression orbit in a high-precision gravitational field based on monopulse orbit control, which comprises the following steps:
constructing a high-order Poincar mapping of the change of the orbit state of the satellite after a regression period from the initial state;
constructing a multi-objective optimization function for solving the regression orbit initial value;
solving to obtain a first regression orbit initial value according to the high-order Poincar é mapping and the multi-objective optimization function;
performing orbit integration on the first regression orbit initial value to obtain an orbit state quantity;
reconstructing the high-order Poincar é mapping according to the track state quantity to obtain reconstructed high-order Poincar mapping;
constructing a control target optimization function;
solving to obtain a next regression orbit initial value according to the reconstructed high-order Poincar é mapping and the control target optimization function;
determining the single pulse speed increment required by the track control according to the speed difference value between the track state quantity and the initial value of the next regression track;
and maintaining the regression orbit in the high-precision gravitational field according to the determined monopulse speed increment required by the orbit control.
In the above method for maintaining a regression orbit in a high-precision gravitational field based on monopulse orbit control, constructing a high-order poincare map of the change of the orbit state of a satellite after a regression period from an initial state includes:
establishing a regression orbit design coordinate system; wherein, regressing the track design coordinate system, includes: an earth center inertial coordinate system and an earth center earth fixed coordinate system;
setting a regression orbit condition according to the precision requirement of task realization; wherein, the regression orbit condition comprises: a strict precision condition indicating that the track returns to the initial position within one regression cycle and a loose precision condition indicating that the track can return to the initial position within a plurality of regression cycles;
and constructing a high-order Poincar mapping of the change of the orbit state of the satellite after a regression period from the initial state.
In the above mentioned method for maintaining the regression orbit in the high precision gravitational field based on monopulse orbit control,
geocentric inertial coordinate system: the substantially plane is the equatorial plane,the axis points to the spring point from the center of the earth,
geocentric coordinate system:
the angular velocity of the earth center earth-fixed coordinate system rotating relative to the earth center inertial coordinate system is the earth rotation angular velocity omegaE。
In the above method for maintaining a regression orbit in a high-precision gravitational field based on monopulse orbit control, constructing a high-order poincare map of the change of the orbit state of a satellite after a regression period from an initial state includes:
taking the regression mode of the regression orbit as nM:nN(ii) a Wherein n isMDenotes the regression period, nNRepresenting the number of track turns in a regression period;
the state quantities x, y, vx、vy、vzAnd initializing the regression period T into a differential algebraic variable, and performing track recursion under a complete gravity perturbation model to obtain a high-order Taylor expansion formula of high-order Poincare mapping:
wherein x and y represent the earth center earth fixed coordinate system of the satelliteShaft andcoordinate value on axis, vx、vyAnd vzIndicating that the satellite is in the earth's centerCoordinate system of earth fixed
by solving the formula (4), the T degree of freedom is eliminated, i.e., X satisfying the formula (3)fFraction z is 0:
wherein z isfRepresenting the track in the geocentric geostationary coordinate system after a time T
based on differential algebraic operation, we can:
substituting formula (5) back to formula (3) can yield:
in the above method for maintaining a regression orbit in a high-precision gravitational field based on monopulse orbit control, constructing a high-order poincare map of the change of the orbit state of a satellite after a regression period from an initial state, further comprising:
when differential algebra operation is performed, the inertial coordinate system of the earth center is calculatedTransformation matrix to geocentric coordinate system
In calculating the transformation matrix
wherein the content of the first and second substances,representing a transformation matrixAs a function of time of the regression cycle T,
In the above method for maintaining a regression orbit in a high-precision gravitational field based on monopulse orbit control, according to the high-order poincare mapping and the multi-objective optimization function, a first regression orbit initial value is obtained by solving, which includes:
determining a multi-objective optimization function for solving the regression orbit initial value:
where v represents the amount of speed deviation from the initial guess, x0And v0Respectively representing the initial position and initial velocity, x, of the satellitefAnd vfRespectively representing the satellite's terminal position and velocity at the point of intersection after one or more regression cycles,
the orbital state quantity [ x, y,0, v ] represented by the formula (6)x,vy,vz]TSubstituting in an equation (8), and solving to obtain an optimization result through an optimization method;
and determining a design initial value of the regression orbit according to the optimization result.
In the above method for maintaining the regression orbit in the high-precision gravitational field based on monopulse orbit control, the optimization result satisfies the following conditions: satisfy the sun synchronization characteristics and satisfy the initial guess [ x0,v0]T＝[x0,y0,0,vx0,vy0,vz0]TCorrection amount v of0＝[vx0,vy0,vz0]TAnd minimum.
In the above mentioned method for maintaining the regression orbit in the high precision gravitational field based on monopulse orbit control,
0 for ensuring v0＝[vx0,vy0,vz0]TAnd minimum.
In the above method for maintaining the regression orbit in the high-precision gravitational field based on monopulse orbit control, the first regression orbit initial value obtained by solving is represented as: [ x ] of0,y0,0,vx0+vx0,vy0+vy0,vz0+vz0]T。
In the above mentioned method for maintaining the regression orbit in the high precision gravitational field based on monopulse orbit control,
when the regression orbit condition is a strict precision condition, the control target optimization function is as follows:
J＝|v|2
when the regression orbit condition is a loose precision condition, the control target optimization function is as follows:
wherein x istDenotes a distance threshold value, vtIs indicative of a threshold value of the speed,the threshold value of the crossing right ascension drift rate is raised.
The invention has the following advantages:
(1) the invention overcomes the defect that the traditional method only considers the non-conservative gravity perturbation (J) of the earth2Or J4Item) directly considering the orbit control under high-order or even complete earth gravity perturbation, and increasing the action of non-conservative perturbation force (such as atmospheric resistance, solar radiation light pressure and sun-moon attraction) to achieve the goal of ensuring sufficient precision requirement.
(2) The invention provides the regression orbit respectively meeting the control of two precision modes, namely a loose precision mode and a strict precision mode according to the realization condition of the actual engineering task, and is convenient for a user to select and apply according to the realization precision requirement of the task.
Drawings
FIG. 1 is a flowchart illustrating the steps of a method for maintaining a regression trajectory in a high-precision gravitational field based on monopulse tracking according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a regression trajectory design coordinate system in an embodiment of the present invention;
fig. 3 is a schematic diagram of the evolution of the front-rear half axis of the regression orbit impulse maneuver in a strict precision mode in the embodiment of the present invention: (a)11:167 regression mode; (b)16:233 regression mode; (c)24:341 regression mode; (d)26:369 regression model;
FIG. 4 is a schematic diagram of the evolution of the regression trajectory applied impulse maneuver pitch and dip in a strict precision mode in the embodiment of the present invention: (a)11:167 regression mode; (b)16:233 regression mode; (c)24:341 regression mode; (d)26:369 regression model;
fig. 5 is a schematic diagram of the evolution of the ascension drift rate of the ascending intersection point before and after the regression orbit impulse maneuver in the strict precision mode in the embodiment of the present invention: (a)11:167 regression mode; (b)16:233 regression mode; (c)24:341 regression mode; (d)26:369 regression model;
FIG. 6 is a schematic diagram illustrating the deviation between the longitude of the tracked track and its initial value in the loose precision mode according to an embodiment of the present invention;
FIG. 7 is a schematic diagram of the evolution of the semi-major axis (a) and the tilt angle (b) in six regression cycles in the loose precision mode according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the embodiments of the present invention will be described in detail with reference to the accompanying drawings.
The accurate initial value of the track design is a necessary condition for forming the long-term regression track, so that various track factors need to be considered in the design stage to realize the accurate design of the regression track. Aiming at the requirement, the invention provides a regression orbit design method in a high-precision gravitational field (considering non-conservative perturbation factors such as high-order non-central gravitational perturbation, atmospheric resistance, solar radiation pressure, solar-lunar gravity perturbation and the like), and solves high-order Poincare mapping through differential algebraic operation so as to accurately approximate orbit recursion in one or more regression periods, thereby avoiding complex calculated amount caused by long-term orbit calculation and realizing high-precision and rapid orbit design. After determining the initial value of the regression orbit, the ending state of the spacecraft after one or several regression cycles will deviate from the initial state according to the determined initial value of the regression orbit. Therefore, to eliminate the deviation, the present invention provides a single-pulse track control strategy for track maintenance.
Referring to fig. 1, in this embodiment, the method for maintaining a regression trajectory in a high-precision gravitational field based on monopulse tracking includes:
(1) And establishing a regression orbit design coordinate system.
In this embodiment, the regression trajectory design coordinate system includes: the earth center inertial coordinate system and the earth center earth-fixed coordinate system. As shown in fig. 2, the geocentric inertial coordinate system is: the substantially plane is the equatorial plane,
The position of the satellite in inertial space can be determined by cylindrical coordinates (r, z, phi), while the position and velocity of the satellite in the geocentric geostationary coordinate system are denoted as X ═ X, y, z, vx,vy,vz]TThe latitude of the track of the point under the satellite
Wherein r represents satellite toThe distance of the axis, z represents the height of the satellite from the equator, phi represents the instantaneous longitude of the meridian plane of the satellite, and x, y and z represent the earth-centered earth-fixed coordinate system of the satellite
(2) And setting a regression orbit condition according to the precision requirement of task realization.
The regression orbit is actually a periodic orbit with a central celestial body as a central celestial body under a fixed coordinate system, and can be solved by some numerical methods, such as a differential correction algorithm. The differential correction algorithm is effective for conservative central celestial gravitational fields, but when the influence of non-conservative forces is added, periodic orbits can hardly be generated. Returning to the initial state X of the orbit according to the idea of solving the periodic orbit0Must be matched to the termination state X after a certain number of regression cyclesfSufficiently close.
When the orbit satisfies the resonance condition, that is, the average angular velocity of the satellite and the rotational angular velocity of the earth can be approximated, and the orbit is a regression orbit, the relationship is as follows:
nN(ωETd-ΔΩd)-2πnM＝0···(1)
wherein, Δ ΩdRepresents a period of intersection TdDrift amount of internal elevation crossing right ascension, nMDenotes the regression period, nNRepresenting the number of turns in a regression cycle.
When the regression trajectory has a strict nM:nNIn the regression mode, the longitude of the track of the subsatellite point at the ascending intersection point is:
wherein λ isiRepresenting the longitude, λ, at the start of the regression orbit0Indicating the longitude of the ith track at the point of intersection.
Preferably, equation (2) can be used as a reference for the nominal track to evaluate the degree to which the actual track deviates from the nominal design.
In this embodiment, from the perspective of actual task engineering implementation, the regression trajectory conditions can be divided into two categories: strict precision conditions and loose precision conditions; wherein the strict precision condition indicates that the track returns to the initial state (initial position and initial velocity) within one regression cycle, and the loose precision condition indicates that the track can return to the initial state (initial position and initial velocity) within a plurality of regression cycles. Accordingly, the regression orbit condition may be defined as an exact regression orbit solution within one regression cycle and a bounded solution within multiple regression cycles.
The requirements for an accurate regression orbit solution within one regression cycle are: initial state X of regression orbit in geocentric geostationary coordinate system in one regression period0Equal to the terminating state Xf(ii) a The requirements for a bounded solution over multiple regression cycles are: termination state X of regression trajectory after m regression cyclesfEqual to initial state X0. Wherein in the case of a bounded solution over multiple regression cycles, starting with the initial bounded solution, the trajectory will deviate before reaching the m regression cycles, but by applying a constraint X to the state of the trajectory at the m-th regression cycle0＝XfThe track will return to the initial state X0Are near and at some deviation from, and are therefore said to be bounded. When the regression cycle number m is 1, the regression orbit is reduced to an accurate solution in a bounded manner. In an actual track design problem, the determination of which solution to employ may depend on the desired accuracy and track control frequency. If the user has strict precision requirements, the track design can be carried out according to the precise solution and the track maintenance can be carried out once in each regression period; for relaxed accuracy requirements, the user may choose a bounded solution for the design and perform a track maintenance once over multiple regression cycles.
(3) And constructing a high-order Poincar mapping of the change of the orbit state of the satellite after a regression period from the initial state.
In this embodiment, the regression pattern of the return tracks is retrieved as nM:nN. Taking a freezing orbit which simultaneously satisfies regression and sun synchronization characteristics as a reference point, and taking the state quantity of the freezing orbit after the state quantity is converted from a geocentric inertial coordinate system to a geocentric coordinate system as the state quantity
The state quantities x, y, vx、vy、vzAnd initializing a regression period T as a differential algebraic variable, and performing orbit recursion under a complete gravity perturbation model (time is from T to T, from T being 0 to T), wherein the complete gravity perturbation model comprises an EGM-08 earth gravitational field model for calculating acceleration, an NRLMSISE-00 model for calculating atmospheric density, a dual cone shadow model for calculating solar radiation pressure and a March three-body gravitational model, and calling NASA SPICE a tool box for calculating moon, solar ephemeris and coordinate system conversion matrixes, in order to balance calculation precision and time, the degree and the order of the earth gravitational field model are 15 × 15, and a high-order Taylor expansion of a high-order Poincare map is obtained:
by solving the formula (4), the T degree of freedom is eliminated, i.e., X satisfying the formula (3)fFraction z is 0:
based on differential algebraic operation, we can:
substituting formula (5) back to formula (3) can yield:
wherein n isMDenotes the regression period, nNRepresenting the orbit turns in a regression cycle, and x and y representing the earth center earth fixed coordinate system of the satellite
Since orbit recursion is performed in the inertial system, and the orbit state quantities related to equations (3), (4), (5), and (4) are all expressed in the geocentric-geostationary coordinate system, it is necessary to calculate the transformation matrix from the geocentric inertial coordinate system to the geocentric-geostationary coordinate system when performing differential algebraic operations
wherein the content of the first and second substances,
In this embodiment, an arbitrary initial point near the reference point on the equatorial plane can be projected to the equatorial plane within one regression cycle by the high-order Poincar é mapping (formula (6)), and formula (5) is the required time (regression cycle). Solving the high-order Poincar é mapping requires differential algebraic integration of 6 variables, and therefore, more calculation time is required compared with ordinary floating-point number integration; however, once this mapping is obtained, the orbit recursion can be accurately approximated by a simple polynomial substitution operation, greatly reducing the amount of computation.
And 102, constructing a multi-objective optimization function for solving the regression orbit initial value.
The regression trajectory calculation is a process of solving an initial value satisfying a target condition, and in this embodiment, a multi-objective optimization function for solving the initial value of the regression trajectory is represented as:
wherein v represents a deviation from the initial guessMeasured speed deviation, x0And v0Respectively representing the initial position and initial velocity, x, of the satellitefAnd vfRespectively representing the satellite's terminal position and velocity at the point of intersection after one or more regression cycles,
And 103, solving to obtain a first regression orbit initial value according to the high-order Poincare mapping and the multi-objective optimization function.
In this embodiment, the orbit state quantity [ x, y,0, v ] represented by the formula (6)x,vy,vz]TIn the formula (8), the optimization result obtained by solving through an optimization method is the optimization result which meets the sun synchronization characteristic (obtained byGuaranteed) and satisfies an initial guess x0,v0]T＝[x0,y0,0,vx0,vy0,vz0]TCorrection amount v of0＝[vx0,vy0,vz0]TMinimum (guaranteed by | v | ═ 0); the final design initial value of the regression trajectory is expressed as: [ x ] of0,y0,0,vx0+vx0,vy0+vy0,vz0+vz0]T。
It should be noted that the objective of introducing the multi-objective function (equation (8)) is to obtain an initial value of the regression orbit having sun synchronization characteristics, and the initial value is required to have the minimum velocity correction amount | v | with respect to the initial guess. In fact, the sun synchronization condition of equation (8) depends on the different mission requirements
And 104, performing orbit integration on the first regression orbit initial value to obtain an orbit state quantity.
In this embodiment, the first regression orbit initial value is subjected to orbit integration, the integration time is the same as the time length (one or more regression cycles) adopted in the design stage, and the orbit state quantity at this time is recorded as Xf1(final state quantity at the end of the first regression cycle or cycles).
And 105, reconstructing the high-order Poincar mapping according to the track state quantity to obtain the reconstructed high-order Poincar mapping.
In this embodiment, to obtain the initial value of the regression orbit in the next one or more regression cycles, i.e. the target value of the pulse control, X is usedf1And reconstructing the higher-order Poincar mapping to obtain a reconstructed higher-order Poincar mapping.
And 106, constructing a control target optimization function.
In this embodiment, all the intersatellite point trajectories need to be maintained within the expected deviation threshold near the nominal trajectory by the method for maintaining the regression orbit in the high-precision gravitational field based on monopulse orbit control. The control target value (i.e., the next regression trajectory initial value) is determined according to the control accuracy requirement.
Preferably, when the regression trajectory condition is a strict precision condition, the control problem can be expressed as (i.e., control objective optimization function):
J＝|v|2
when the regression trajectory condition is a loose precision condition, the control problem can be expressed as (i.e., control objective optimization function):
wherein the optimization variable is v ═ vx,vy,vz]T，xt、vtAnd
It should be noted that the Taylor polynomial mapping obtained by differential algebraic operation of the present invention is usually valid for multiple regression cycles, and can be used to approximate the true orbit state. The mapping may be computed at the ground station and injected up to the on-board computer when visible to the satellite. Since the polynomial calculation only involves multiplication and addition operations, the online calculation does not consume too much of the on-board limited CPU computational resources, which is very important for on-board autonomous tracking.
And step 107, solving to obtain the next regression orbit initial value according to the reconstructed high-order Poincare mapping and the control target optimization function.
In this embodiment, the representation form of the reconstructed higher-order Poincar é map is the same as that of the higher-order Poincar map in the
And step 108, determining the single-pulse speed increment required by the track control according to the speed difference value between the track state quantity and the next regression track initial value.
And step 109, maintaining the regression orbit in the high-precision gravitational field according to the determined monopulse speed increment required by the orbit control.
In a preferred embodiment of the present invention, the tracking strategy for the strict precision mode is as follows:
the threshold values of position drift, velocity drift and rising point right ascension change are 10 respectively-6km、10-3km/s and 10-7In order to determine the target state quantity of the orbit with strict accuracy requirements. The invention takes a regression mode orbit of an actual sun synchronous regression orbit task as a simulation embodiment, and the regression modes are respectively 11:167 (the regression period is 11 days, and 167 circles of orbit operation are performed in one regression period), 16:233 (the regression period is 16 days, and 233 circles of orbit operation are performed in one regression period), 24:341 (the regression period is 24 days, and 341 circles of orbit operation are performed in one regression period), and 26:369 (the regression period is 26 days, and 369 circles of orbit operation are performed in one regression period).
The state quantities of the two regression cycles before and after the control are obtained as shown in tables 1, 2, 3 and 4, the positions and velocities in the 2 nd and 4 th columns of each table being initial conditions for starting the first and second regression cycles, respectively, and the positions and velocities in the 3 rd and 5 th columns being end states at the end of the first and second regression cycles, respectively. At the end of the first regression cycle, the spacecraft is brought to the target state, i.e. the initial state of the second regression cycle, by applying the single-pulse control, and then the second regression cycle is started. The required velocity increment v is simply achieved by comparing the velocity components in columns 3 and 4, with the desired sizes of the examples (11:167, 16:233, 24:341, and 26:369) for each regression model being 6.8178cm/s, 6.6070cm/s, 9.7281cm/s, and 10.3481cm/s, respectively. Through the single-pulse control, the track deviation can be maintained within a given threshold value, and strict precision requirements are met.
Wherein, tables 1 to 4 are as follows:
TABLE 1, 11:167 regression model example tracking control results
TABLE 2, 16:233 regression model example tracking control results
TABLE 3, 24:341 regression model example tracking results
TABLE 4, 26:369 regression model example orbit control results
Unlike previous research that track maintenance is performed by adjusting the half-major axis flat root, the invention directly performs track control through speed correction, and changes the instantaneous track root, as shown in fig. 3, 4 and 5. In fig. 3 to 5, the semiaxis, the orbit inclination angle and the ascension drift rate of the ascending point at each orbit secondary ascending point are all values in a true equatorial coordinate system, and epoch time is taken as 2018, 9, 1, 10, 30, 00.000 (UTC). In addition, the dotted line in fig. 5 is the angular velocity ω of the earth moving around the sunSThe size of (2). According to simulation results, each parameter keeps continuously changing before and after applying the rail control, and the right ascension drift rate of the semimajor axis and the ascending intersection point is kept in a fixed interval.
Therefore, a track design based on strict regression track conditions and a track control method of applying a pulse maneuver once per regression cycle can be used to accomplish the regression track task with strict accuracy requirements.
In a preferred embodiment of the present invention, the orbit control strategy of the loose precision model is as follows:
considering that in the actual task design, the precision requirement is looser, for example, a certain deviation between the designed track and the nominal track is allowed, in this case, it is not necessary to perform a pulse motor control in each regression period as in the strict precision mode, and the consumption of fuel will be greatly reduced. Taking a certain satellite orbit in an actual task as an example, the satellite has the mass of 300kg, the orbit inclination angle of 64.75 degrees and the height of about 650km, and the orbit regression mode is 7:102, namely the regression period of the orbit is 7 days, and the orbit runs for 102 circles in one regression period. Since the orbit is not a sun-synchronous orbit, the sun-synchronous constraint needs to be replaced with an inclination constraint when solving for the motionless point as an initial guess. The poincare mapping obtained by solving based on differential algebra operation also has reliable precision in a plurality of regression cycles, so that only one orbit recursion is needed to be carried out under a complete gravity perturbation model to obtain a Taylor polynomial of the mapping, and then the orbit recursion result can be approximated by substituting polynomial calculation (the solution is substituted twice in the embodiment). From this, all the track states within the three regression cycles can be determined. And designing the track by adopting a loose regression condition, wherein the actual track is allowed to have certain drift relative to the nominal track, but the track state returns to be close to the initial track state in the third regression period.
According to the control precision requirement of the embodiment, only a certain distance range is kept between the initial position and the deviation of the termination position after three regression cycles, and then the control optimization problem is converted into:
and in the present embodiment, the distance threshold x is settSet to 2km, thus illustrating the recursive orbit loose control strategy.
The calculation only involves the orbit recursion in one regression cycle and the substitution evaluation of the Taylor polynomial for two times, compared with the method of directly adopting the orbit recursion in three regression cycles, the calculation amount is greatly reduced, and the rapid and effective design of the orbit is realized. The available orbit state quantities in six regression cycles before and after orbit control are shown in table 5: the initial value of the regression trajectory is shown in
TABLE 5 orbit control results in relaxed precision mode
Although the present invention has been described with reference to the preferred embodiments, it is not intended to limit the present invention, and those skilled in the art can make variations and modifications of the present invention without departing from the spirit and scope of the present invention by using the methods and technical contents disclosed above.
Those skilled in the art will appreciate that the invention may be practiced without these specific details.
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