Joint fixed-point capturing method based on continuous small thrust

Abstract

The invention discloses a joint fixed-point capturing method based on continuous small thrust, and the method aims at a geosynchronous orbit satellite which carries out orbit transfer through the continuous small thrust, and employs a multi-step strategy to enable the flat longitude of the satellite to be gradually approached to a fixed-point position. Firstly, before a semi-major axis is about to be in place, by controlling in-place time, the longitude of a satellite continuously approaches to the east, and when the semi-major axis reaches a synchronous orbit, the satellite is located at a fixed-point longitude position; afterwards, when the inclination angle and eccentricity rate isolation residual error are corrected, the influence of earth shadow, accidental ignition stopping and the like is overcome by controlling the ignition stopping arc section, and the satellite flat longitude continues to be maintained at the fixed point position. And finally, after the inclination angle and the eccentricity rate are all in place, high-precision fixed-point capturing is carried out in a short time, and the effect that the geographic longitude and latitude of the satellite are all located in a dead zone controlled by a stationary orbit is achieved.

Description

Technical Field

[0001] The invention relates to a joint fixed-point capture method based on continuous small thrust, belonging to the technical field of satellite attitude and orbit control. Background Art

[0002] When the satellite and rocket separate, the geostationary orbit satellite is often not directly in the synchronous orbit, but in the geosynchronous transfer orbit. Its semi-major axis, inclination, and eccentricity all need to be adjusted through orbit control, and fixed-point capture is required at the end of the orbit transfer.

[0003] Continuous low-thrust orbit transfer and fixed-point capture is a new way of executing tasks. Compared with the traditional high-thrust engine orbit control, it can effectively save propellant fuel consumption. There are essential differences between the two: First, high-thrust orbit capture is usually combined with the selection of orbit circles by apogee orbit change pulse control, which cannot be implemented under continuous low-thrust orbit transfer control; second, continuous low-thrust orbit transfer takes a long time, and changes in geographic longitude are more sensitive to thrust size and direction, requiring long-term corrections, making it difficult to balance orbit control efficiency and fixed-point time. Summary of the invention

[0004] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art, a joint fixed-point capture method based on continuous small thrust is proposed, and fixed-point capture is performed in a step-by-step and multiple correction manner to meet the orbit transfer and fixed-point capture mission requirements of geostationary orbit satellites.

[0005] The technical solution of the present invention is:

[0006] A joint fixed-point capture method based on continuous small thrust is applied to a satellite configured with continuous small thrust and capable of adjusting the thrust pointing of orbit control. The joint fixed-point capture method includes:

[0007] When the satellite is in the transfer orbit and the semi-major axis, inclination and eccentricity are not in place, the semi-major axis, inclination and eccentricity are jointly controlled and the longitude is adjusted so that the semi-major axis is at a fixed longitude position when it reaches the synchronous orbit;

[0008] The eccentricity is eliminated by directing the in-plane thrust component perpendicular to the perigee direction; the orbital inclination is reduced by igniting the out-of-plane component in the orbital normal direction; the satellite's longitude and latitude are maintained at a fixed position by eliminating the residual errors of the inclination and eccentricity mentioned above;

[0009] When the satellite's semi-major axis, inclination, and eccentricity are all in place, it will ignite twice along the tangential direction of the orbit to perform fixed-point capture and accurately control the longitude and drift rate.

[0010] Preferably, when the satellite is in the transfer orbit and the semi-major axis, inclination and eccentricity are not in place, the semi-major axis, inclination and eccentricity are jointly controlled and combined with the longitude adjustment, and the semi-major axis is increased by igniting the in-plane thrust component in the tangential direction of the orbit; the orbit inclination is reduced by igniting the out-of-plane component in the normal direction of the orbit; the orbit eccentricity is eliminated by stopping the ignition in the perigee area; and the satellite longitude is controlled to drift eastward by manipulating the time for the semi-major axis to reach the target semi-major axis so that the semi-major axis is at a fixed longitude position when it reaches the synchronous orbit.

[0011] Preferably, the semi-major axis, inclination, and eccentricity are jointly controlled and the longitude and latitude are adjusted. The adjustment method is:

[0012] The small thrust is ignited continuously within one orbital period. The thrust is in the plane formed by the velocity direction and the orbital angular momentum, and there is an angle ψ with the orbital plane. 1 , the absolute value remains unchanged, but the sign changes at the argument angles of 90° and 270°; the ignition is stopped at the mean anomaly angle of 0°±ΔM; each orbital cycle is traversed by ψ at ±90° 1 , traverse ΔM within 0-180° to minimize fuel consumption; when the orbital period is more than 90% of the target orbital period, control the time for the semi-major axis to reach the target semi-major axis.

[0013] Preferably, the time for the semi-major axis to reach the target semi-major axis is controlled, and the control method is: the thrust size is calibrated according to the change trend of the orbital semi-major axis and the inclination in each orbital period, and the target fixed-point longitude is obtained by numerical integration using the calibrated thrust, and the ΔM value is extended or shortened so that the satellite's flat longitude is at the fixed-point accuracy when the semi-major axis reaches the target semi-major axis.

[0014] Preferably, the eccentricity is eliminated by directing the in-plane thrust component perpendicular to the perigee direction; and the orbital inclination is reduced by igniting the out-of-plane component in the orbital normal direction. The specific method is as follows:

[0015] The small thrust is ignited continuously in one orbital period. When the angle between the thrust component in the orbital plane and the direction of the perigee vector is -90°, the angle between the component outside the orbital plane and the orbital plane is ψ 2 , the absolute value remains unchanged, but changes its sign around 90° and 270°;

[0016] Set the orbit angle to 90°±Δu 1 Area, orbit angle 270°±Δu 2 Area, stop firing to reduce fuel consumption;

[0017] Each orbital cycle updates the angle ψ between the out-of-plane component and the orbital plane by traversing ±90° 2 , making fuel consumption at a minimum.

[0018] Preferably, when the earth's shadow season, initial orbit conditions, and unplanned stop firing are affected, Δu is set 1 , Δu 2 The relationship between the size of the fixed point longitude is corrected:

[0019] If the orbital argument u=90° is closer to the perigee: When the drift rate becomes larger, set Δu 1 >Δu 2 ; When the drift rate becomes smaller, set Δu 1 <Δu 2 ;

[0020] If the orbital argument u=270° is closer to the perigee: When the drift rate becomes larger, set Δu 1 <Δu 2 ; When the drift rate becomes smaller, set Δu 1 >Δu 2 ;

[0021] When the drift rate enables the satellite to reach the fixed position at the end of fixed-point acquisition, set Δu 1 =Δu 2 .

[0022] Preferably, when the semi-major axis, inclination, and eccentricity of the satellite are all in place, ignition is performed twice along the tangential direction of the orbit to perform fixed-point capture, which specifically includes:

[0023] After receiving the fixed-point capture command, the satellite orbit is determined first, the latest longitude and latitude drift rate of the satellite are obtained, and then the thrust is adjusted to the starting direction and the ignition is started. The duration is T 1 ;

[0024] T 1 After the ignition is completed, the star drifting phase begins. The drifting phase lasts for T draft ;

[0025] After the drifting is completed, adjust the thrust to the braking direction and perform braking ignition for a duration of T 2 ;

[0026] After the braking ignition is completed, the satellite reaches the target longitude and the drift rate is 0.

[0027] Preferably, if the satellite is performing a deorbit mission at the end of its life, only the start-up ignition is performed, T 1 The capture is considered complete after the segment ignition is completed.

[0028] The advantages of the present invention compared with the prior art are:

[0029] (1) The present invention performs preliminary fixed-point capture control while performing low-thrust orbit transfer, eliminating most of the fixed-point longitude differences without consuming additional fuel. When the orbit transfer is completed, the geographical longitude of the sub-satellite point is basically in place, and only fine-tuning is required.

[0030] (2) The fixed-point capture method described in the present invention has the advantages of updating the orbit control parameter angle multiple times and adjusting in stages, and has a high success rate.

[0031] (3) The present invention performs geographic longitude adjustment during orbit transfer. At this time, the inclination and eccentricity are larger, and the distance from other synchronous orbit satellites is farther, thus achieving inclination eccentricity isolation during the positioning process, which is safer. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0033] Figure 1 It is a flowchart of the combined fixed-point capture method based on continuous small thrust of the present invention;

[0034] Figure 2 The fixed-point capture correction curve diagrams of the embodiments of the present invention, (a) is the curve diagram corresponding to Example 1, and (b) is the curve diagram corresponding to Example 2;

[0035] Figure 3 The fixed-point capture start-drifting-braking curve diagram of an embodiment of the present invention, (a) is a curve diagram of the semi-major axis of the orbit changing with time, (b) is a curve diagram of the eccentricity changing with time, and (c) is a curve diagram of the geographic longitude changing with time. DETAILED DESCRIPTION

[0036] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0037] Aiming at the actual characteristics of continuous low-thrust orbit transfer and taking full account of the actual engineering constraints and the convenience of on-orbit operation, the present invention proposes a joint fixed-point capture method based on continuous low-thrust, which is mainly used for orbit transfer and fixed-point capture of geosynchronous orbit satellites that are equipped with continuous low-thrust actuators and have the ability to adjust the orbit control thrust pointing.

[0038] This method is Figure 1 As shown, when the satellite is in the transfer orbit and the semi-major axis, inclination and eccentricity are not in place, the following steps are performed during the entire low-thrust orbit transfer:

[0039] S1: When the orbital period is greater than 21 hours, the semi-major axis, inclination, and eccentricity are jointly controlled and the longitude and mean are adjusted.

[0040] By igniting the in-plane thrust component in the tangential direction of the orbit, the semi-major axis is increased; by igniting the out-of-plane component in the normal direction of the orbit, the orbit inclination is reduced; and by stopping the ignition near the perigee, the orbit eccentricity is eliminated.

[0041] (1) In this stage, the small thrust is continuously ignited for most of an orbital period. The thrust is in the plane formed by the velocity direction (or vertical radial direction) and the orbital angular momentum, and has a certain angle ψ with the orbital plane. 1 , its absolute value remains unchanged, but it changes its sign around 90° and 270°.

[0042] (2) Near the perigee, set the mean anomaly angle to 0°±ΔM and stop firing to reduce the orbital eccentricity.

[0043] (3) Regularly update the ψ 1 , ΔM, so that the fuel consumption is at the minimum value.

[0044] (4) When the orbital period is more than 90% of the target orbital period, the longitude drift is performed eastward. The execution method is to regularly calibrate the thrust size through the change trend of the orbit semi-major axis and inclination, and on this basis, extend or shorten the ΔM size so that the satellite's longitude is at the fixed point accuracy when the semi-major axis reaches the target semi-major axis.

[0045] Under the above strategy, when the semi-major axis of the orbit is about to be in place, the satellite phase continues to drift eastward and gradually approaches the fixed-point phase by adjusting the time when the semi-major axis reaches the target semi-major axis, that is, the eccentricity time of the stop point fire control.

[0046] S2: Eliminate the inclination and eccentricity residuals.

[0047] After completing the joint control of the semi-major axis, inclination, and eccentricity, a large inclination and eccentricity residual is left to ensure the safety of fixed-point capture. At the current stage, the eccentricity is eliminated by the in-plane thrust component perpendicular to the perigee direction; the out-of-plane component is ignited in the orbit normal direction to reduce the orbital inclination.

[0048] (1) During this stage, the low thrust is continuously ignited for most of an orbital period. The thrust direction is in the J2000 coordinate system. The thrust component in the orbital plane is at an angle of -90° to the direction of the perigee vector, and the thrust component out of the orbital plane is at an angle of ψ 2, its absolute value remains unchanged, but the sign changes around 90° and 270°. Set the orbit angle to 90°±Δu 1 Area, orbit angle 270°±Δu 2 Area, stop ignition to reduce fuel consumption.

[0049] (2) Regularly update the ψ 2 , making fuel consumption at a minimum.

[0050] (3) When affected by the Earth's shadow season, initial orbit conditions, or unplanned firing, set Δu 1 , Δu 2 The symmetry of , corrects the fixed point longitude:

[0051] If the orbital argument u=90° is closer to the perigee: When the drift rate becomes larger, set Δu 1 >Δu 2 ; When the drift rate becomes smaller, set Δu 1 <Δu 2 .

[0052] If the orbital argument u=270° is closer to the perigee: When the drift rate becomes larger, set Δu 1 <Δu 2 ; When the drift rate becomes smaller, set Δu 1 >Δu 2 .

[0053] When the drift rate is appropriate, Δu 1 =Δu 2 .

[0054] (4) Regularly update the ψ 2 , making fuel consumption at a minimum.

[0055] Under the above strategy, corrections are made to the deviations of the horizontal longitude and drift rate from the fixed position caused by the Earth's shadow or other firing suspension events by stopping firing near the perigee and apogee.

[0056] S3: Perform small thrust fixed-point capture control.

[0057] At this point, after the satellite's semi-major axis, inclination, and eccentricity are all in place, the longitude and drift rate can be precisely controlled through two ignitions along the tangential direction of the orbit.

[0058] (1) The design of fixed-point capture is divided into the following five states. After receiving the fixed-point capture command, the satellite orbit is first determined to obtain the latest satellite longitude and longitude drift rate. Then, the thrust is adjusted to the east or west start direction and the start ignition is performed. The duration is T 1 . T 1After the ignition is completed, the star drifting phase begins. The drifting phase lasts for T draft After the drifting is completed, the thrust is adjusted to the west or east braking direction, and the braking ignition is performed for a duration of T 2 After the braking ignition is completed, the satellite reaches the target longitude and the drift rate is 0.

[0059] (2) If the satellite is performing a deorbit mission at the end of its life, only the start-up ignition is performed, T 1 The capture is considered complete after the segment ignition is completed.

[0060] Example 1

[0061] Assume that the thrust of the small thruster is 320 mN, the semi-major axis of the satellite is located near 42165 km, the inclination is 4.5°, the eccentricity is 0.07, and the fixed point longitude is 135°E. In the stage of eliminating the inclination and eccentricity, set (1)Δu 1 =30°, Δu 2 =30°; (2) Δu 1 =28.1°, Δu 2 =31.0°, and the time it takes for both examples to reach the synchronous orbit is 31 days. In example 1, the mean longitude drifts eastward, and in example 2, the mean longitude is stabilized around 135° by adjusting the firing stop time. Figure 2 (a) and (b) in the figure.

[0062] Example 2

[0063] Set the current geographic longitude of the satellite to 150°E, use the start-ignition-brake process, first start to raise the semi-major axis, then drift the satellite, and finally brake to return the semi-major axis to the nominal position of the synchronous orbit, and at the same time control the satellite to the target fixed point position of 134°E. For details of the curve, see Figure 3 (a)~(c) in the text.

[0064] The simulation results show that the method of the present invention can realize the joint fixed-point capture based on continuous small thrust, and can be used for the fixed-point capture control of orbit transfer in geosynchronous orbit.

[0065] In summary, by using the joint fixed-point capture method based on continuous low thrust of the present invention, a geosynchronous orbit satellite equipped with a continuous low thrust orbit transfer actuator can be used to gradually approach the satellite's longitude and latitude to a fixed-point position using a multi-step strategy.

[0066] The above-described embodiments are only preferred specific implementations of the present invention. Common changes and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. A joint fixed-point capture method based on continuous low thrust, applied to a satellite configured with continuous low thrust and capable of adjusting the thrust pointing of orbit control, characterized in that: The joint fixed-point capture method includes: When the satellite is in the transfer orbit and the semi-major axis, inclination and eccentricity are not in place, the semi-major axis, inclination and eccentricity are jointly controlled and the longitude is adjusted so that the semi-major axis is at a fixed longitude position when it reaches the synchronous orbit; The eccentricity is eliminated by directing the in-plane thrust component perpendicular to the perigee direction; the orbital inclination is reduced by igniting the out-of-plane component in the orbital normal direction; the satellite's longitude and latitude are maintained at a fixed position by eliminating the residual errors of the inclination and eccentricity mentioned above; When the satellite's semi-major axis, inclination, and eccentricity are all in place, it will ignite twice along the tangential direction of the orbit to perform fixed-point capture and accurately control the longitude and drift rate.

2. A joint fixed-point capture method based on continuous small thrust according to claim 1, characterized in that: When the satellite is in the transfer orbit and the semi-major axis, inclination and eccentricity are not in place, the semi-major axis, inclination and eccentricity are jointly controlled and combined with the longitude adjustment. The semi-major axis is increased by igniting the in-plane thrust component in the tangential direction of the orbit. The orbit inclination is reduced by igniting the out-of-plane component in the normal direction of the orbit. The orbit eccentricity is eliminated by stopping the ignition in the perigee area. The time for the semi-major axis to reach the target semi-major axis is controlled to control the satellite longitude to drift eastward so that the semi-major axis is at a fixed longitude position when it reaches the synchronous orbit.

3. A joint fixed-point capture method based on continuous small thrust according to claim 2, characterized in that: The semi-major axis, inclination, eccentricity are jointly controlled and the longitude is adjusted. The adjustment method is: The small thrust is ignited continuously within one orbital period. The thrust is in the plane formed by the velocity direction and the orbital angular momentum, and has an angle ψ1 with the orbital plane. The absolute value remains unchanged, but the positive and negative values ​​change at the phase angles of 90° and 270°. The mean anomaly angle is set to 0°±ΔM to stop ignition. In each orbital period, the fuel consumption is kept to a minimum by traversing ψ1 within ±90° and traversing ΔM within 0-180°. When the orbital period is more than 90% of the target orbital period, the time for the semi-major axis to reach the target semi-major axis is controlled.

4. A joint fixed-point capture method based on continuous small thrust according to claim 3, characterized in that: The time for the semi-major axis to reach the target semi-major axis is controlled by the following method: the thrust size is calibrated according to the changing trend of the orbital semi-major axis and inclination in each orbital period, and the target fixed-point longitude is obtained by numerical integration of the calibrated thrust. By extending or shortening the ΔM value, the satellite's flat longitude is at the fixed-point accuracy when the semi-major axis reaches the target semi-major axis.

5. The method for joint fixed-point capture based on continuous small thrust according to claim 1, characterized in that: The eccentricity is eliminated by directing the in-plane thrust component perpendicular to the perigee direction; the orbital inclination is reduced by igniting the out-of-plane component in the normal direction of the orbit. The specific method is as follows: The small thrust is ignited continuously in one orbital period. When the angle between the thrust component in the orbital plane and the direction of the perigee vector is -90°, the angle ψ2 between the component outside the orbital plane and the orbital plane remains unchanged in absolute value, and changes in sign around 90° and 270°. Set the orbit angle area of ​​90°±Δu1 and the orbit angle area of ​​270°±Δu2, and stop firing to reduce fuel consumption; In each orbital cycle, the angle ψ2 between the out-of-plane component and the orbital plane is updated at ±90° to minimize the fuel consumption.

6. A joint fixed-point capture method based on continuous small thrust according to claim 5, characterized in that: When affected by the earth shadow season, initial orbit conditions, and unplanned stop firing, the relationship between Δu1 and Δu2 is set to correct the fixed point longitude: If the orbital argument u=90°is closer to the perigee: when the drift rate becomes larger, set Δu1>Δu2; when the drift rate becomes smaller, set Δu1<Δu2; If the orbital argument u=270°is closer to the perigee: when the drift rate becomes larger, set Δu1<Δu2; when the drift rate becomes smaller, set Δu1>Δu2; When the drift rate enables the satellite to reach the fixed position at the end of fixed-point acquisition, Δu1=Δu2 is set.

7. The method for joint fixed-point capture based on continuous small thrust according to claim 1, characterized in that: When the semi-major axis, inclination and eccentricity of the satellite are all in place, it will be ignited twice along the tangential direction of the orbit to perform fixed-point capture, including: After receiving the fixed-point capture command, the satellite orbit is first determined to obtain the latest satellite longitude and longitude drift rate, and then the thrust is adjusted to the starting direction and the start ignition is performed, the duration is T1; After the T1 stage ignition is completed, it enters the stop ignition drift stage, and the drift duration is T draft ; After the drifting is completed, the thrust is adjusted to the braking direction and the braking ignition is performed for a duration of T2; After the braking ignition is completed, the satellite reaches the target longitude and the drift rate is 0.

8. The method for joint fixed-point capture based on continuous small thrust according to claim 7, characterized in that: If the satellite is performing a deorbit mission at the end of its life, only the startup ignition is performed, and the capture is considered complete after the T1 stage ignition is completed.

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