CN108516106B - Angular momentum unloading method and system in orbit transfer process of full-electric propulsion satellite - Google Patents
Angular momentum unloading method and system in orbit transfer process of full-electric propulsion satellite Download PDFInfo
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Abstract
The invention discloses an angular momentum unloading method in a full-electric propulsion satellite orbit transfer process, which comprises the following steps: before each track cycle begins, setting an unloading arc section A and an unloading arc section B; calculating and determining a thrust direction adjusting angle of the electric thruster; judging whether the thrust direction adjustment angle of the electric thruster of the unloading arc section A exceeds a critical value or not, and entering the unloading arc section A if the thrust direction adjustment angle of the electric thruster of the unloading arc section A does not exceed the critical value; if the angular momentum unloading amount exceeds the critical value, the angular momentum unloading amount of the unloading arc section A needs to be adjusted again, then the thrust direction adjustment angle of the electric thruster is recalculated, the electric thruster enters the unloading arc section A, after the unloading arc section A finishes unloading, the new angular momentum unloading amount is determined through the accumulation of the angular momentum of a new wheel train, the thrust direction adjustment angle of the electric thruster is calculated and determined, and the electric thruster enters the unloading arc section B. The invention solves the angular momentum unloading problem under the condition that the electric thruster executes the orbit maneuver control task in the orbit transfer process, and realizes the combined control of the full-electric propulsion satellite orbit maneuver and the angular momentum unloading.
Description
Technical Field
The invention belongs to the technical field of satellite orbit attitude dynamics and control, and particularly relates to an angular momentum unloading method and system in an all-electric propulsion satellite orbit transfer process.
Background
An All-Electric Propulsion Satellite (All-Electric Propulsion Satellite) adopts an Electric Propulsion system (such as ionic Electric Propulsion or Hall Electric Propulsion) with high specific impulse to replace a complex two-component unified chemical Propulsion system, so as to realize tasks of Satellite transfer orbit orbital transfer after separation of satellites and arrows, on-orbit position maintenance, angular momentum unloading, off-orbit and the like after Satellite in-orbit. Due to the limitation of the configuration quantity, the installation position and the on-orbit power supply power of the electric thruster, the east-west position, the south-north position and the north-south position of the fully-electric propulsion satellite are mutually coupled, the control parameters are reduced in the failure mode of the electric thruster, and the position keeping strategy design is very complex.
The general configuration of full electric propulsion satellite is 4 electric thrusters, is installed in satellite back of the body floor or north and south board through biax vector adjustment mechanism in rectangular configuration, contains 2 branches, and every branch contains 2 electric thrusters of diagonal, and 2 branches are each other for the backup. In the process of satellite orbital transfer, 2 electric thrusters are generally adopted to ignite simultaneously to work, the thrust directions are parallel, the resultant force passes through the center of mass of the satellite, and the resultant torque is zero. The transfer process of the full-electric propulsion satellite is long, generally can reach 3-6 months, and basically all orbital arc sections are subjected to orbital transfer maneuvering. The satellite attitude control adopts a flywheel system as an actuating mechanism, and the full-electric propulsion satellite orbital transfer process is subjected to the action of various space environment moments, such as sunlight pressure moment, pneumatic moment, gravity gradient moment and the like, and the accumulated angular momentum of a gear train needs to be unloaded in time. The electric thruster is used as a unique executing mechanism for orbit control and angular momentum unloading, so that strong coupling influence exists between the orbit control and the angular momentum unloading, and on the premise that an orbit transfer strategy is determined, the angular momentum unloading strategy with small influence on the maneuvering process of the orbit transfer has certain technical difficulty.
Disclosure of Invention
The technical problem solved by the invention is as follows: the method and the system for unloading the angular momentum of the full-electric propulsion satellite in the orbital transfer process overcome the defects of the prior art, have the advantages that the influence caused by orbital transfer maneuvering is small as much as possible, the problem of unloading the angular momentum under the condition that an electric thruster executes an orbital maneuvering control task in the orbital transfer process is solved, and the joint control of the orbital maneuvering and the angular momentum unloading of the full-electric propulsion satellite is realized.
The purpose of the invention is realized by the following technical scheme: according to one aspect of the invention, an angular momentum unloading method for a full-electric propulsion satellite orbit transfer process is provided, and the method comprises the following steps: the method comprises the following steps: before each track cycle begins, setting an unloading arc section A and an unloading arc section B, wherein the unloading arc section A is before an unloading arc B, and the unloading arc section B is an alternative arc section of the unloading arc section A; step two: before the unloading arc section A starts, determining the unloading amount of angular momentum through gear train angular momentum accumulation, and calculating and determining the thrust direction adjustment angle of the electric thruster; step three: judging whether the thrust direction adjustment angle of the electric thruster of the unloading arc section A exceeds a critical value or not, and entering the unloading arc section A if the thrust direction adjustment angle of the electric thruster of the unloading arc section A does not exceed the critical value; step four: if the angular momentum unloading amount exceeds the critical value, the angular momentum unloading amount of the unloading arc section A needs to be adjusted again, then the thrust direction adjustment angle of the electric thruster is recalculated, the electric thruster enters the unloading arc section A, after the unloading arc section A finishes unloading, the new angular momentum unloading amount is determined through the accumulation of the angular momentum of a new wheel train, the thrust direction adjustment angle of the electric thruster is calculated and determined, and the electric thruster enters the unloading arc section B.
In the angular momentum unloading method in the full-electric propulsion satellite orbit transfer process, in the step one, the interval between the unloading arc section A and the unloading arc section B is 2-3 hours;
the time length of each unloading arc segment is as follows:
wherein, the delta H is the angular momentum unloading amount and is determined according to the satellite in-orbit angular momentum accumulation condition; fpIs the thrust of the electric thruster, hmThe height of the centroid relative to the thrust point, Δ α is the thrust turn angle.
In the angular momentum unloading method in the full-electric propulsion satellite orbit transfer process, in the second step, the angular momentum unloading amount is calculated according to the following steps:
the whole star angular momentum can be determined according to the gear train angular momentum accumulation and the gear train installation parameters:
Hb=CHw
wherein HbFor whole star angular momentum, C is a train wheel mounting matrix, HwIs a gear train angular momentum vector;
the angular momentum unloading amount is the inverse of the current whole satellite angular momentum:
ΔH=-Hb
where Δ H is the angular momentum unload amount.
In the angular momentum unloading method in the full-electric propulsion satellite orbit changing process, in the step two, the formula of the thrust direction adjustment angle of the electric thruster is as follows:
wherein (Delta theta)1,Δα1,Δθ2,Δα2) The elevation angle rotation angle and the azimuth angle rotation angle of the first electric thruster and the elevation angle rotation angle and the azimuth angle rotation angle of the second electric thruster are respectively; fpTo unload the thrust of the electric thruster; x is the number of0、y0、z0Is the first electric thrustThe position coordinates of the installation points of the device take positive values; t is t1For the start of the unloading arc A, A (t)1) Is t1A transformation matrix from the time satellite body coordinate system to the inertial coordinate system,for the integral value of the conversion matrix from the satellite body coordinate system to the inertial coordinate system in the unloading arc section A, the following formula is calculated:
in the formula, t2And A (t) is a conversion matrix from the satellite body coordinate system to the inertial coordinate system at the moment t.
In the angular momentum unloading method for the full-electric propulsion satellite orbit transfer process, in the third step, the critical value is 5 degrees.
In the angular momentum unloading method in the full-electric propulsion satellite orbit changing process, in the third step, in the thrust direction adjusting sub-stage of the unloading arc section A, the vector adjusting mechanism drives the electric thruster to rotate by a specified angle according to the thrust direction adjusting angle of the electric thruster in the second step; in the angular momentum unloading stage of the unloading arc section A, the thrust direction of the thruster is kept unchanged, and the angular momentum of the satellite is continuously unloaded; and in the sub-stage of returning the thrust direction of the unloading arc section A, the vector adjusting mechanism adjusts the thrust direction to return to the zero position.
In the angular momentum unloading method for the full-electric propulsion satellite orbit transfer process, in the fourth step, the angular momentum unloading amount of the unloading arc section A is readjusted according to the following formula:
wherein (Delta theta)1,Δα1,Δθ2,Δα2) The elevation angle rotation angle and the azimuth angle rotation angle of the first electric thruster and the elevation angle rotation angle and the azimuth angle rotation angle of the second electric thruster are respectively; Δ H is the angular momentum unload amount; Δ HAFor readjusting the angle of the discharge arc AMomentum unloading amount.
In the angular momentum unloading method for the full-electric propulsion satellite orbital transfer process, in the thrust direction adjusting sub-stage of the unloading arc section A, the time required by the vector adjusting mechanism to drive the electric thruster to rotate is as follows:
wherein, ω isonDriving the rotation speed for the vector adjusting mechanism; (Delta theta)1,Δα1,Δθ2,Δα2) The elevation angle rotation angle and the azimuth angle rotation angle of the first electric thruster and the elevation angle rotation angle and the azimuth angle rotation angle of the second electric thruster are respectively;
in the sub-stage of returning the thrust direction of the unloading arc section A, the time for adjusting the thrust direction to return to the zero position by the vector adjusting mechanism is as follows:in the formula, ωbackThe rotating speed is adjusted back for the vector adjusting mechanism; the vector adjusting mechanism has the following callback time:
in the angular momentum unloading method in the full-electric propulsion satellite orbit changing process, in the fourth step, in the thrust direction adjusting sub-stage of the unloading arc section B, the vector adjusting mechanism drives the electric thruster to rotate by a specified angle according to the new thrust direction adjusting angle of the electric thruster; in the stage of unloading the angular momentum unloading carrier of the unloading arc section B, the thrust direction of the thruster is kept unchanged, and the angular momentum of the satellite is continuously unloaded; and in the thrust direction returning sub-stage of the unloading arc section B, the vector adjusting mechanism adjusts the thrust direction to return to the zero position.
In the angular momentum unloading method in the full-electric propulsion satellite orbit changing process, in the fourth step, the new angular momentum unloading amount is delta H '═ CH'wWherein C is a gear train installation matrix, Hw' is a new wheel train angular momentum vector;
the thrust direction adjustment angle of the novel electric thruster is as follows:
wherein (Delta theta)1',Δα1',Δθ2',Δα2') are the new elevation angle rotation angle and azimuth angle rotation angle of the first electric thruster and the new elevation angle rotation angle and azimuth angle rotation angle of the second electric thruster respectively; x is the number of0、y0、z0The coordinates of the mounting point of the first electric thruster are positive values; t is t1For the beginning of the unloading arc B, A (t)1) Is t1A transformation matrix from the time satellite body coordinate system to the inertial coordinate system,is the integral value of the transformation matrix from the satellite body coordinate system to the inertial coordinate system in the unloading arc section A.
According to another aspect of the present invention, there is also provided an angular momentum unloading system for a full-electric propulsion satellite orbital transfer process, the system comprising: the first module is used for setting an unloading arc section A and an unloading arc section B before the beginning of each track cycle, wherein the unloading arc section A is before the unloading arc section B, and the unloading arc section B is an alternative arc section of the unloading arc section A; the second module is used for determining the angular momentum unloading amount through gear train angular momentum accumulation before the unloading arc section A starts, and calculating and determining the thrust direction adjusting angle of the electric thruster; the third module is used for judging whether the thrust direction adjusting angle of the electric thruster of the unloading arc section A exceeds a critical value or not, and if not, entering the unloading arc section A; and the fourth module is used for readjusting the angular momentum unloading amount of the unloading arc section A if the angular momentum unloading amount exceeds the critical value, then recalculating the thrust direction adjustment angle of the electric thruster, entering the unloading arc section A, determining a new angular momentum unloading amount through new gear train angular momentum accumulation again after the unloading arc section A finishes unloading, calculating and determining a new thrust direction adjustment angle of the electric thruster, and entering the unloading arc section B.
Compared with the prior art, the invention has the following beneficial effects:
(1) the invention provides a method for unloading angular momentum by adopting an electric thruster in the full-electric propulsion satellite orbit transfer process, which can regularly unload the angular momentum accumulated in a wheel system and avoid the out-of-control attitude caused by the long-term accumulation of the angular momentum of a satellite;
(2) the angular momentum unloading method for the full-electric propulsion satellite orbit transfer process, provided by the invention, has negligible influence on the original orbit control task, and realizes the joint control of orbit maneuvering and angular momentum unloading.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:
fig. 1 is a schematic flowchart of an angular momentum unloading method in an orbit transferring process of a fully-electrically-propelled satellite according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a star electric thruster layout provided by an embodiment of the invention;
FIG. 3 is a schematic diagram of the direction of the electric thruster during ignition in the process of satellite orbital transfer according to the embodiment of the invention;
fig. 4 is a schematic view of the setting of the unloading arc provided by the embodiment of the invention.
Detailed Description
Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.
In the full-electric propulsion satellite orbit transfer process, 2 electric thrusters are adopted for ignition and orbit transfer, and 2 unloading arc sections are arranged in each orbit period. Before each unloading arc section starts, the angular momentum to be unloaded is determined through the accumulation of the angular momentum of the wheel train, and the adjustment angle of the thrust direction of the electric thruster is further calculated and determined. The unloading arc section is divided into three sub-stages of thrust direction adjustment, angular momentum unloading and thrust direction adjustment back. In the stage 1, an angle rotation vector adjusting mechanism is adjusted according to the thrust direction of an electric thruster; in the 2 nd stage, the thrust direction is kept unchanged, and at the moment, the electric thruster generates a constant unloading moment and continuously acts for a period of time; and the 3 rd stage vector adjusting mechanism adjusts the thrust direction to return to a zero position, namely the resultant torque is zero. The whole unloading arc section electric thruster still works in normal ignition, the thrust direction adjustment range is small, and the influence on the track maneuvering process can be ignored. Meanwhile, angular momentum unloading is carried out regularly in each orbit period, and attitude runaway caused by long-term accumulation of satellite angular momentum can be avoided.
Fig. 1 is a schematic flow chart of an angular momentum unloading method in an all-electric propulsion satellite orbit transfer process according to an embodiment of the present invention. As shown in fig. 1, the angular momentum unloading method in the process of full-electric propulsion satellite orbital transfer includes the following steps:
(1) step one, before each orbit cycle begins, an unload arc segment A, B is set. Before the unloading arc section A is used for unloading the radian B, the arc section B is an alternative arc section of the arc section A, the satellite only carries out angular momentum unloading in the arc section A under the normal condition, and when the angular momentum of the satellite is accumulated more and can not be unloaded only through the arc section A, or the arc section A and the ground shadow are overlapped under the condition that the electric thruster needs to be shut down, the satellite needs to be unloaded in the arc section B.
The position of the discharge arc section is selected according to the following principle:
● the unloading arc is far from the near point of the track as much as possible, on one hand, the track angular speed of the near point is very large, the arc angle corresponding to the same unloading time is large, and large arc loss exists. On the other hand, the near-location disturbance moment is large, and the satellite attitude is out of control due to the superposition of the unloading moment and other disturbance moments;
● the unloading arc section is far away from the arc section with fast attitude change, namely the arc section with large star angular velocity, and the arc section has large coupling interference torque;
● the two unloading segments A, B should be spaced to ensure adequate operating time between unloading.
Based on the above criteria, the unloading arc sections are recommended to be arranged in front of and behind the remote place, and the interval between the two unloading arc sections can be 2-3 hours.
The time length of the unloading arc section cannot be set too short, so that the adjustment angle of the thrust direction is as small as possible, and the orbital transfer thrust loss is minimum; and the length can not be too long, so that a large unloading error caused by insufficient rotation angle resolution of the vector adjusting mechanism is avoided. The unloading arc period time length can be estimated by:
in the above formula, Δ H is the angular momentum unloading amount, and is determined according to the satellite in-orbit angular momentum accumulation condition; fpIs the thrust of the electric thruster, hmThe height of the centroid relative to the thrust point is shown as Δ α, which is the thrust rotation angle and is typically taken to be 3 °.
(2) And step two, before the unloading arc section A starts, determining angular momentum to be unloaded through gear train angular momentum accumulation, and calculating and determining the thrust direction adjustment angle of the electric thruster. Before the unloading arc section A starts, the whole star angular momentum can be determined according to the wheel train angular momentum accumulation and the wheel train installation parameters:
Hb=CHw
in the above formula, HbFor whole star angular momentum, C is a train wheel mounting matrix, Hw=(hw1,…,hwn)TIs the angular momentum vector of the wheel train. The unloading target is that the angular momentum of the current whole satellite is reduced to zero, and the angular momentum unloading amount is the inverse of the angular momentum of the current whole satellite:
ΔH=-Hb
in the above formula,. DELTA.H is the angular momentum unload amount. Further, the adjustment angle of the electric thruster can be obtained:
in the above formula,(Δθ1,Δα1,Δθ2,Δα2) 4 turning angle variables of 2 electric thrusters are respectively an elevation angle turning angle and an azimuth angle turning angle of the electric thruster 1 and an elevation angle turning angle and an azimuth angle turning angle of the electric thruster 2; x is the number of0、y0、z0The coordinates of the installation point of the electric thruster 1 are positive values. t is t1Is the starting time of arc segment A, A (t)1) Is t1A transformation matrix from the time satellite body coordinate system to the inertial coordinate system,the integral value of the transformation matrix from the satellite body coordinate system to the inertial coordinate system in the arc section A is calculated according to the following formula:
in the formula, t2And A (t) is the ending time of the arc segment A, and A (t) is a conversion matrix from the satellite body coordinate system to the inertial coordinate system at the time t.
(3) And step three, judging whether the adjustment angle of the thrust direction of the electric thruster of the unloading arc section A exceeds a critical value, and if the adjustment angle exceeds the critical value, readjusting the unloading amount of the angular momentum.
In the second step, 4 rotation angles (delta theta) of 2 electric thrusters are calculated1,Δα1,Δθ2,Δα2) If the angle value exceeds 5 degrees, the unloading arc section A can not finish the angular momentum unloading for the time, and the angular momentum unloading amount of the arc section A is recalculated according to the following formula:
and by Δ HAAnd recalculating the rotation angle of the electric thruster according to the step two for the input.
(4) And step four, in the stage 1 of unloading the arc section, the vector adjusting mechanism adjusts the thrust direction to a specified angle.
In the second step and the third step, 4 rotation angles (delta theta) of 2 electric thrusters are calculated1,Δα1,Δθ2,Δα2) The vector adjusting mechanism drives the electric thruster to rotate by a specified angle, and the required time of the rotating process is as follows:
in the formula, ωonThe vector adjusting mechanism drives the rotating speed. The middle point moment of the regulating process should be corresponding to the starting moment t of the arc segment A1The coincidence, i.e. the vector adjustment mechanism drive time, is:
(5) and step five, in the 2 nd stage of the unloading arc section, the thrust direction of the electric thruster is kept unchanged, and the satellite angular momentum is continuously unloaded.
After the vector adjusting mechanism drives the electric thruster to rotate in place, the electric thruster is locked at the position, so that the thrust direction is kept stable, and the angular momentum of the satellite is continuously unloaded.
(6) And step six, in the stage 3 of unloading the arc section, the vector adjusting mechanism adjusts the thrust direction to return to the zero position.
When the arc section A is finished, the vector adjusting mechanism drives the electric thruster to return to a zero position, and the process time is adjusted back:
in the formula, ωbackThe speed is adjusted back for the vector adjustment mechanism. The middle point moment of the regulating process should be equal to the end moment t of the arc segment A2The coincidence, i.e. the vector adjustment mechanism, has a callback time of:
(7) and seventhly, judging whether the unloading arc section B needs angular momentum unloading or not, and calculating unloading parameters.
Step three, judging whether the arc section A can independently complete the angular momentum unloading or not, if the arc section A can independently complete the unloading, the arc section B does not need to be unloaded; and if the arc section A cannot independently complete unloading, recalculating the angular momentum unloading amount of the arc section B according to the step two, and executing the steps four to six to complete second unloading.
The steps are repeatedly executed, so that the angular momentum of the whole satellite can be maintained in a lower range, and the attitude runaway caused by the long-term accumulation of the angular momentum of the satellite is avoided.
Specifically, the layout of the satellite electric thruster is shown in fig. 2, and the orientation of the satellite orbital transfer process electric thruster is shown in fig. 3.
(1) Step one, the current track parameters are as follows: hp is 1000km, Ha is 36700km, and i is 28.47 °. Before the track cycle begins, the unload arc segment A, B is set, as shown in FIG. 4. The unloading arc section A and the unloading arc B are symmetrical relative to a far place, and the arc section A is 2 hours earlier than the arc section B. The accumulated amount of angular momentum in the current orbit period is about 20Nms, the thrust of the electric thruster is 0.12N, the height of the center of mass is 1.1m, and the time length of the unloading arc segment is 1447 s.
(2) Step two, before the beginning of the unloading arc section A, the angular momentum of 4 tower-shaped mounted flywheels is accumulated to be Hw=(6.7,8.2,4.1,5.5)TNms, whole star angular momentum of Hb=(2.1,2.2,14.3)TNms, angular momentum to be unloaded Δ H (-2.1, -2.2, -14.3)TNms, and calculating the rotation angle of the electric thruster as follows: delta theta1=2.03°,Δα1=1.81°,Δθ2=1.35°,Δα2=1.67°。
(3) And step three, judging that the rotation angle of the electric thruster does not exceed the rotation angle upper limit (5 degrees), and executing the unloading process according to the unloading parameters in the step two.
(4) Step four, starting time t of arc section A114934s, the vector control mechanism control process Δ ton28s, inAt that time, the rotation vector adjustment mechanism is started.
(5) And step five, after the vector adjusting mechanism drives the electric thruster to rotate in place, the thrust direction is kept stable, and the satellite angular momentum is continuously unloaded.
(6) Sixthly, starting time t of arc section A116381s, the vector adjustment mechanism recalls the process Δ tback28s, inAt that time, the vector adjustment mechanism begins to be recalled.
(7) And seventhly, because the unloading arc section A can independently complete angular momentum unloading, the unloading arc section B does not need angular momentum unloading.
The above process is completed, namely, angular momentum unloading is completed once in the ignition orbital transfer process of the full-electric propulsion satellite.
The embodiment also provides an angular momentum unloading system for an all-electric propulsion satellite orbit transferring process, which includes: the device comprises a first module, a second module, a third module and a fourth module. Wherein,
the first module is used for setting an unloading arc section A and an unloading arc section B before the beginning of each track cycle, wherein the unloading arc section A is before the unloading arc section B, and the unloading arc section B is an alternative arc section of the unloading arc section A; the second module is used for determining the angular momentum unloading amount through gear train angular momentum accumulation before the unloading arc section A starts, and calculating and determining the thrust direction adjusting angle of the electric thruster; the third module is used for judging whether the thrust direction adjusting angle of the electric thruster of the unloading arc section A exceeds a critical value or not, and if not, entering the unloading arc section A; and the fourth module is used for readjusting the angular momentum unloading amount of the unloading arc section A if the angular momentum unloading amount exceeds the critical value, then recalculating the thrust direction adjustment angle of the electric thruster, entering the unloading arc section A, determining a new angular momentum unloading amount through new gear train angular momentum accumulation again after the unloading arc section A finishes unloading, calculating and determining a new thrust direction adjustment angle of the electric thruster, and entering the unloading arc section B.
The embodiment provides a method for unloading angular momentum by adopting an electric thruster in the full-electric propulsion satellite orbit transfer process, which can periodically unload the angular momentum accumulated in a wheel system and avoid the attitude runaway caused by the long-term accumulation of the angular momentum of a satellite; the angular momentum unloading method for the full-electric propulsion satellite orbit transfer process provided by the embodiment has negligible influence on the original orbit control task, and realizes the joint control of orbital maneuver and angular momentum unloading.
The above-described embodiments are merely preferred embodiments of the present invention, and general changes and substitutions by those skilled in the art within the technical scope of the present invention are included in the protection scope of the present invention.
Claims (10)
1. An angular momentum unloading method in a full-electric propulsion satellite orbit transfer process is characterized by comprising the following steps:
the method comprises the following steps: before each track cycle begins, setting an unloading arc section A and an unloading arc section B, wherein the unloading arc section A is before an unloading arc B, and the unloading arc section B is an alternative arc section of the unloading arc section A;
step two: before the unloading arc section A starts, determining the unloading amount of angular momentum through gear train angular momentum accumulation, and calculating and determining the thrust direction adjustment angle of the electric thruster;
step three: judging whether the thrust direction adjustment angle of the electric thruster of the unloading arc section A exceeds a critical value or not, and entering the unloading arc section A if the thrust direction adjustment angle of the electric thruster of the unloading arc section A does not exceed the critical value;
step four: if the angular momentum unloading amount exceeds the critical value, the angular momentum unloading amount of the unloading arc section A needs to be adjusted again, then the thrust direction adjustment angle of the electric thruster is recalculated, the electric thruster enters the unloading arc section A, after the unloading arc section A finishes unloading, the new angular momentum unloading amount is determined through the accumulation of the angular momentum of a new wheel train, the thrust direction adjustment angle of the electric thruster is calculated and determined, and the electric thruster enters the unloading arc section B.
2. The full-electric propulsion satellite orbital transfer process angular momentum unloading method according to claim 1, characterized in that: in the first step, the interval between the unloading arc section A and the unloading arc section B is 2-3 hours;
the time length of each unloading arc segment is as follows:
wherein, the delta H is the angular momentum unloading amount and is determined according to the satellite in-orbit angular momentum accumulation condition; fpIs the thrust of the electric thruster, hmThe height of the centroid relative to the thrust point, Δ α is the thrust turn angle.
3. The full-electric propulsion satellite orbital transfer process angular momentum unloading method according to claim 1, characterized in that: in the second step, the angular momentum unload amount is calculated according to the following steps:
the whole star angular momentum can be determined according to the gear train angular momentum accumulation and the gear train installation parameters:
Hb=CHw
wherein HbFor whole star angular momentum, C is a train wheel mounting matrix, HwIs a gear train angular momentum vector;
the angular momentum unloading amount is the inverse of the current whole satellite angular momentum:
ΔH=-Hb
where Δ H is the angular momentum unload amount.
4. The full-electric propulsion satellite orbital transfer process angular momentum unloading method according to claim 3, characterized in that: in the second step, the formula of the thrust direction adjustment angle of the electric thruster is as follows:
wherein (Delta theta)1,Δα1,Δθ2,Δα2) The elevation angle rotation angle and the azimuth angle rotation angle of the first electric thruster and the elevation angle rotation angle and the azimuth angle rotation angle of the second electric thruster are respectively; fpTo unload the thrust of the electric thruster; x is the number of0、y0、z0The coordinates of the mounting point of the first electric thruster are positive values; t is t1For the start of the unloading arc A, A (t)1) Is t1A transformation matrix from the time satellite body coordinate system to the inertial coordinate system,in order to inverse the integral value of the conversion matrix from the satellite body coordinate system to the inertial coordinate system in the unloading arc section a,for the integral value of the conversion matrix from the satellite body coordinate system to the inertial coordinate system in the unloading arc section A, the following formula is calculated:
in the formula, t2And A (t) is a conversion matrix from the satellite body coordinate system to the inertial coordinate system at the moment t.
5. The full-electric propulsion satellite orbital transfer process angular momentum unloading method according to claim 1, characterized in that: in the third step, in the thrust direction adjusting sub-stage of the unloading arc section A, the vector adjusting mechanism drives the electric thruster to rotate by a specified angle according to the thrust direction adjusting angle of the electric thruster in the second step; in the angular momentum unloading stage of the unloading arc section A, the thrust direction of the thruster is kept unchanged, and the angular momentum of the satellite is continuously unloaded; and in the sub-stage of returning the thrust direction of the unloading arc section A, the vector adjusting mechanism adjusts the thrust direction to return to the zero position.
6. The full-electric propulsion satellite orbital transfer process angular momentum unloading method according to claim 1, characterized in that: in step four, the angular momentum unloading amount of the unloading arc section A is readjusted according to the following formula:
wherein (Delta theta)1,Δα1,Δθ2,Δα2) The elevation angle rotation angle and the azimuth angle rotation angle of the first electric thruster and the elevation angle rotation angle and the azimuth angle rotation angle of the second electric thruster are respectively; Δ H is the angular momentum unload amount; Δ HATo readjust the angular momentum unload amount of the unloading arc segment A.
7. The full-electric propulsion satellite orbital transfer process angular momentum unloading method according to claim 5, characterized in that: in the thrust direction adjustment sub-stage of the unloading arc section A, the time required by the vector adjusting mechanism to drive the electric thruster to rotate is as follows:
wherein, ω isonDriving the rotation speed for the vector adjusting mechanism; (Delta theta)1,Δα1,Δθ2,Δα2) The elevation angle rotation angle and the azimuth angle rotation angle of the first electric thruster and the elevation angle rotation angle and the azimuth angle rotation angle of the second electric thruster are respectively;
in the sub-stage of returning the thrust direction of the unloading arc section A, the time for adjusting the thrust direction to return to the zero position by the vector adjusting mechanism is as follows:in the formula, ωbackThe rotating speed is adjusted back for the vector adjusting mechanism; the vector adjusting mechanism has the following callback time:wherein, t2The moment of the end of the unloading arc segment a.
8. The full-electric propulsion satellite orbital transfer process angular momentum unloading method according to claim 1, characterized in that: in the fourth step, in the thrust direction adjusting sub-stage of the unloading arc section B, the vector adjusting mechanism drives the electric thruster to rotate by a specified angle according to the thrust direction adjusting angle of the new electric thruster; in the stage of unloading the angular momentum unloading carrier of the unloading arc section B, the thrust direction of the thruster is kept unchanged, and the angular momentum of the satellite is continuously unloaded; and in the thrust direction returning sub-stage of the unloading arc section B, the vector adjusting mechanism adjusts the thrust direction to return to the zero position.
9. The full-electric propulsion satellite orbital transfer process angular momentum unloading method according to claim 1, characterized in that: in step four, the new amount of angular momentum unload is Δ H '═ CH'wWherein C is a gear train installation matrix, Hw' is a new wheel train angular momentum vector;
the thrust direction adjustment angle of the novel electric thruster is as follows:
wherein (Delta theta)1',Δα1',Δθ2',Δα2') are the new elevation angle rotation angle and azimuth angle rotation angle of the first electric thruster and the new elevation angle rotation angle and azimuth angle rotation angle of the second electric thruster respectively; x is the number of0、y0、z0The coordinates of the mounting point of the first electric thruster are positive values; t is t1' starting time of unloading arc segment B, A (t)1') is t1' transformation matrix of the satellite body coordinate system to the inertial coordinate system at time,is the integral value of the transformation matrix from the satellite body coordinate system to the inertial coordinate system in the unloading arc section A.
10. An angular momentum offloading system for a full electric propulsion satellite orbital transfer process, the system comprising:
the first module is used for setting an unloading arc section A and an unloading arc section B before the beginning of each track cycle, wherein the unloading arc section A is before the unloading arc section B, and the unloading arc section B is an alternative arc section of the unloading arc section A;
the second module is used for determining the angular momentum unloading amount through gear train angular momentum accumulation before the unloading arc section A starts, and calculating and determining the thrust direction adjusting angle of the electric thruster;
the third module is used for judging whether the thrust direction adjusting angle of the electric thruster of the unloading arc section A exceeds a critical value or not, and if not, entering the unloading arc section A;
and the fourth module is used for readjusting the angular momentum unloading amount of the unloading arc section A if the angular momentum unloading amount exceeds the critical value, then recalculating the thrust direction adjustment angle of the electric thruster, entering the unloading arc section A, determining a new angular momentum unloading amount through new gear train angular momentum accumulation again after the unloading arc section A finishes unloading, calculating and determining a new thrust direction adjustment angle of the electric thruster, and entering the unloading arc section B.
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