Semi-autonomous orbital maintenance mission planning method and system using electric propulsion

Abstract

The application provides a semi-autonomous orbit maintenance task planning method and system using electric propulsion, and comprises the following steps: after starting the autonomous orbit maintenance task planning on the ground, generating an orbit maintenance task sequence of continuous multiple orbits by autonomously calculating the total time length of the thruster, the number of operations and the satellite time of each operation on the satellite, inserting the orbit maintenance task sequence into the task queue of the whole satellite, and executing the orbit maintenance task sequence in time sequence. The application solves the problem of autonomous orbit maintenance task planning in the case of satellite configuration of electric thrusters.

Description

Technical Field

[0001] This invention relates to the field of satellite autonomous mission planning, and more specifically, to a semi-autonomous orbit maintenance mission planning method and system using electric propulsion. Background Technology

[0002] With increasingly frequent space activities, satellite constellation launches often require multiple satellites to be launched simultaneously, imposing stringent requirements on the weight of individual satellites. At the same time, the demand for longer satellite lifespans is also growing, and traditional chemical propulsion requires loading more fuel to meet these long-lifespan requirements. To improve the satellite payload-to-weight ratio and meet the demands of long lifespan and multiple-satellite launches, electric propulsion has gradually become the preferred option. Compared to chemical propulsion, electric propulsion has a higher specific impulse but lower thrust and higher power consumption, requiring multiple orbits and restarts to achieve orbit maintenance missions. Relying solely on ground control is labor-intensive and consumes significant telemetry and control resources, necessitating the design of onboard autonomous orbit maintenance mission planning functions.

[0003] Chinese patent document with publication number CN201710179460.9 discloses an autonomous orbit control method for low-orbit remote sensing satellites. This method does not require consideration of multiple orbits or mission conflicts, but it is not suitable for long-term orbit maintenance based on electric propulsion.

[0004] Chinese patent document CN201610898405.0 discloses a trajectory maintenance control method based on a chemical thruster. This method achieves trajectory lifting by a single thruster activation based on the deviation of the semi-major axis, which is quite different from the electric propulsion control strategy.

[0005] In Chinese patent document CN201510836995.X, a joint control method for maintaining and unloading electric propulsion in synchronous orbit is disclosed. A calculation method for autonomous orbit maintenance of multiple electric thrusters suitable for the angle adjustment mechanism is designed. In this method, the control duration and ignition position of each thruster need to be solved in real time according to the satellite status, which involves a large amount of calculation and is not suitable for satellites with limited computing resources and high energy consumption.

[0006] Chinese patent document CN201410190625.9 discloses a method for maintaining the position of an electrically propelled geostationary satellite. It discloses a control method that uses four thrusters to control the orbital inclination, eccentricity, and longitude drift rate. This method does not consider energy constraints and mission conflict constraints in its design. It is suitable for satellites in high orbits with sufficient energy and real-time telemetry on the ground, but not for low orbit satellites in situations involving light and shadow switching or telemetry and control arcs.

[0007] Liu Qi et al. disclosed a high-precision phase-maintaining technique based on a limit cycle in their paper "A High-Precision Phase-Maintaining Method for Low-Earth Orbit Constellations" (Journal of Astronautics, 2021, 42(11)). This technique can control the satellite's orbital altitude and eccentricity, but it requires estimating the influence of atmospheric drag on the satellite's orbital altitude to obtain the corresponding relationship between the latitudinal argument and the semi-major axis variation. Meanwhile, the paper did not provide a planning strategy for electric propulsion orbit maintenance under energy-constrained conditions. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the purpose of this invention is to provide a semi-autonomous orbit maintenance mission planning method and system using electric propulsion.

[0009] According to the present invention, a semi-autonomous orbit maintenance mission planning method using electric propulsion includes: after the autonomous orbit maintenance mission planning is initiated on the ground, the satellite autonomously calculates the total working time, number of working times, and satellite time for each working time of the thrusters, generates a sequence of orbit maintenance missions for continuous multi-orbit missions, inserts them into the mission queue of the entire satellite, and executes them sequentially according to time.

[0010] Preferably, the method includes the following steps:

[0011] Step S1: After the ground injection command initiates the onboard autonomous orbit maintenance mission planning, the average orbital elements at the corresponding time are calculated based on the current orbital elements, and the time of the most recent arrival at the apogee is recursively obtained.

[0012] Step S2: Calculate the difference between the current orbital semi-major axis and the nominal orbital semi-major axis, combine the orbital altitude gain per unit time obtained by the satellite mass and electric thruster characteristics, divide the two and round up to obtain the total jet propulsion duration;

[0013] Step S3: Calculate the allowable operating time of the electric propulsion monorail based on the satellite's energy.

[0014] Step S4: Calculate the number of times electric propulsion needs to operate based on the total jet propulsion time and the allowable working time of the monorail;

[0015] Step S5: Based on the nearest apogee time, the number of electric propulsion operations, and the duration of single-orbit operations, generate a sequence of continuous multi-orbit orbit maintenance missions and insert them into the satellite's mission queue.

[0016] Preferably, in step S1, the average orbital elements at the current moment are calculated, and the expression for calculating the time of the most recently arriving stars at their nearest and farthest points is as follows:

[0017]

[0018] Where: T0 is the star time corresponding to the current orbital element, in seconds;

[0019] u g The gravitational constant is 3.98600436 × 10⁻⁶. 14 m 3 / s 2 ;

[0020] a and M are the mean semi-major axis and mean apogee angle of the orbit at the current moment, respectively, in meters (m) and rad (rad).

[0021] Preferably, in step S2, the expression for calculating the total jet duration is as follows:

[0022]

[0023] Where: a0 and a are the nominal semi-major axis of the track and the average semi-major axis of the current track, respectively, in meters;

[0024] H0 represents the upward lift relative to the nominal track for each track control operation, in meters (m).

[0025] H c The orbital altitude that can be raised per unit time based on the thruster thrust, specific impulse, and satellite mass, expressed in m / s.

[0026] Preferably, in step S3, the ground calculates the maximum allowable single-track operation time T of the electric thruster based on the onboard battery capacity, solar panel area, satellite platform power consumption, electric propulsion power consumption, and the illumination and shadow time of the satellite orbit. c .

[0027] Preferably, in step S4,

[0028] Based on the total operating time of the thruster and the allowable operating time of the monorail, the number of times the thruster operates is calculated:

[0029]

[0030] Where: ngate is the number of consecutive times that can be opened.

[0031] Preferably, based on the orbital altitude to be increased and the duration of each single operation during the satellite's entire lifespan, the expression for the total number of electric thruster switches used for orbit maintenance throughout the satellite's entire lifespan is as follows:

[0032]

[0033] Where: (x, y, z) are the orbital altitude decay values ​​corresponding to high, medium, and low solar activity years, respectively, in meters; (l1, l2, l3) are the number of high, medium, and low solar activity years during the entire designed life of the satellite.

[0034] Preferably, in step S5, the generated orbit maintenance sequence is as follows:

[0035] T1-Tc / 2~T1+Tc / 2: First ignition;

[0036] T2-Tc / 2~T2+Tc / 2: Second ignition;

[0037] T3-Tc / 2~T3+Tc / 2: Third ignition;

[0038] Tn-Tc / 2~Tn+Tc / 2: The nth ignition.

[0039] Where: T1 = Ta, is the star time corresponding to the nearest successive orbital apogee;

[0040] T2 = T1 + m × T is the intermediate star time corresponding to the second ignition;

[0041] T3 = T 2 +m×T is the intermediate star time corresponding to the 3rd ignition;

[0042] T n =T n-1 +m×T is the intermediate star corresponding to the nth ignition;

[0043] T is the orbital period, and

[0044] m is the number of orbits required between two consecutive ignitions, which is related to the satellite's energy balance.

[0045] Preferably, based on the energy balance of the electric propulsion orbit maintenance process, when inserting the autonomously generated electric propulsion task into the mission queue of the entire satellite, it is necessary to make a conflict judgment on the ground injection, autonomously planned electric propulsion task and the operational task;

[0046] The judgment rules include:

[0047] If there are no imaging, data transmission, or other orbit maintenance tasks within each k orbital period before and after the electric propulsion mission, the command queue will be inserted.

[0048] -If there are other business or track maintenance tasks within the previous or next k track cycles, then the current task is discarded.

[0049] A semi-autonomous orbit maintenance mission planning system using electric propulsion, according to the present invention, includes:

[0050] Module M1: After the ground injection command initiates the onboard autonomous orbit maintenance mission planning, it calculates the average orbital elements at the corresponding time based on the current orbital elements, and recursively obtains the time of the most recent arrival at the apogee;

[0051] Module M2: Calculates the difference between the current orbital semi-major axis and the nominal orbital semi-major axis, and combines the orbital altitude gain per unit time obtained by combining the satellite mass and electric thruster characteristics. Divide the two values ​​and round up to obtain the total jet propulsion duration.

[0052] Module M3: Calculates the permissible operating time of the electric propulsion monorail based on satellite energy.

[0053] Module M4: Calculates the number of times electric propulsion needs to operate based on the total jet propulsion time and the allowable operating time of the monorail;

[0054] Module M5: Based on the nearest apogee time, the number of electric propulsion operations, and the duration of single-track operations, it generates a sequence of continuous multi-track orbit maintenance missions and inserts them into the satellite's mission queue.

[0055] Compared with the prior art, the present invention has the following beneficial effects:

[0056] 1. After the mission is launched on the ground, the present invention autonomously plans an orbit maintenance mission based on electric propulsion, reducing the workload of ground mission planning and injection.

[0057] 2. This invention calculates the apogee and orbital period once during a single mission planning process, reducing the amount of onboard computation. Attached Figure Description

[0058] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0059] Figure 1 This is a flowchart of the semi-autonomous orbit maintenance mission planning method using electric propulsion in this invention. Detailed Implementation

[0060] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0061] Reference Figure 1 This invention discloses a semi-autonomous orbit maintenance mission planning method using electric propulsion. After the autonomous orbit maintenance mission planning is initiated by issuing a command on the ground, the satellite autonomously calculates the total working time, number of working times, and satellite time for each working time of the thrusters, generates a sequence of orbit maintenance missions for continuous multi-orbit missions, inserts them into the mission queue of the entire satellite, and executes them sequentially according to time.

[0062] Specifically, a method for planning a semi-autonomous orbit maintenance mission using electric propulsion includes the following steps:

[0063] Step S1: After the ground-based command initiates the onboard autonomous orbit maintenance mission planning, the average orbital elements at the corresponding time are calculated based on the current orbital elements, and the time of the most recent arrival at the apogee is recursively obtained.

[0064] Specifically, the average orbital elements at the current moment are calculated, and the expression for calculating the time of the most recently arriving stars at their nearest and farthest points is as follows:

[0065]

[0066] Where: T0 is the star time corresponding to the current orbital element, in seconds;

[0067] u g The gravitational constant is 3.98600436 × 10⁻⁶. 14 m 3 / s 2 ;

[0068] a and M are the mean semi-major axis and mean apogee angle of the orbit at the current moment, respectively, in meters (m) and rad (rad).

[0069] In a preferred embodiment, it is assumed that the nominal semi-major axis of the current satellite orbit is 6,871,030 km, and the semi-major axis of the satellite orbit corresponding to the current time 10,000 s is 6,870,930 m. The semi-major axis of the orbit is reduced by 100 m, and M is π / 2.

[0070] After the ground sends the autonomous mission planning start command for orbit maintenance at time t0, the onboard software begins mission planning at t0+2s, reads GPS orbit data, and calculates the mean orbital elements at the current time, including t, a, and M; based on the current orbital semi-major axis a, the mean orbital angular velocity is calculated as follows:

[0071]

[0072] Based on the orbital angular velocity ω and the mean anterior angle M, the time corresponding to the apogee and the mean anterior angle of π is calculated as follows:

[0073]

[0074] Step S2: Calculate the difference between the current orbital semi-major axis and the nominal orbital semi-major axis, combine the orbital altitude gain per unit time obtained by the satellite mass and electric thruster characteristics, divide the two and round up to obtain the total jet propulsion duration;

[0075] Specifically, the expression for calculating the total jet duration is as follows:

[0076]

[0077] Where: a0 and a are the nominal semi-major axis of the track and the average semi-major axis of the current track, respectively, in meters;

[0078] H0 represents the upward lift relative to the nominal track for each track control operation, in meters (m).

[0079] H c The orbital altitude that can be raised per unit time based on the thruster thrust, specific impulse, and satellite mass, expressed in m / s.

[0080] In one specific implementation, the satellite's semi-major axis is lowered by 100m. Assuming that the elevation gain relative to the nominal orbit is 50m per orbit control cycle, and the calibrated value of the orbital altitude gain per unit time obtained from the electric thruster characteristics is 0.042m / s, the total jet propulsion time required for this orbit maintenance can be calculated as follows:

[0081]

[0082] Step S3: Calculate the permissible duration of single-track operation of the electric thruster based on the satellite's energy resources; the ground-based system calculates the maximum permissible duration T of single-track operation of the electric thruster based on the satellite's battery capacity, solar array area, satellite platform power consumption, electric propulsion power consumption, and the satellite orbit's illumination and shadow time. c .

[0083] In one specific implementation, considering a satellite equipped with a 90Ah lithium-ion battery pack, a satellite platform power consumption of 857W, and a power consumption of 420W during electric propulsion operation, and taking into account a 35-minute shadow, the calculation shows that under the energy balance constraint during the sunlight period, the maximum single-cycle operating time of the satellite's electric propulsion is T. c =900s.

[0084] Step S4: Calculate the number of times electric propulsion needs to operate based on the total jet propulsion time and the allowable working time of the monorail;

[0085] Specifically, the number of thruster operations is calculated based on the total operating time of the thruster and the allowable operating time of the monorail:

[0086]

[0087] Where: ngate is the number of consecutive times that can be opened.

[0088] In a preferred embodiment, the total number of operations is calculated based on the total jet duration and the longest single-cycle working time:

[0089]

[0090] Step S5: Based on the nearest apogee time, the number of electric propulsion operations, and the duration of single-orbit operations, generate a sequence of continuous multi-orbit orbit maintenance missions and insert them into the satellite's mission queue.

[0091] Specifically, the generated orbital maintenance sequence is as follows:

[0092] T1-Tc / 2~T1+Tc / 2: First ignition;

[0093] T2-Tc / 2~T2+Tc / 2: Second ignition;

[0094] T3-Tc / 2~T3+Tc / 2: Third ignition;

[0095] Tn-Tc / 2~Tn+Tc / 2: The nth ignition.

[0096] Where: T1 = Ta, is the star time corresponding to the nearest successive orbital apogee;

[0097] T2 = T1 + m × T is the intermediate star time corresponding to the second ignition;

[0098] T3 = T 2 +m×T is the intermediate star corresponding to the 3rd ignition;

[0099] T n =T n-1 +m×T is the intermediate star corresponding to the nth ignition;

[0100] T is the orbital period, and

[0101] m is the number of orbits required between two consecutive ignitions, which is related to the satellite's energy balance.

[0102] In the example above, if the number of orbital revolutions required between two adjacent ignitions is set to 0, then the final generated autonomous orbit control sequence is:

[0103] Sequence 1: 12405.99~13305.99: 1st ignition;

[0104] Sequence 2: 18074.05~18974.05: 2nd ignition;

[0105] Sequence 3: 23742.11~24642.11: The third ignition;

[0106] Sequence 4: 29410.16~30310.16: The fourth ignition.

[0107] Considering the energy balance during electric propulsion orbit maintenance, and based on the following rules, after conflict assessment of ground-based injection, autonomously planned electric propulsion tasks, and operational tasks, autonomously generated electric propulsion tasks are inserted into the satellite's task queue. The assessment rules are as follows:

[0108] (1) If there are no imaging, data transmission, or other orbit maintenance tasks within each k orbital period before and after the electric propulsion mission, then insert the command queue.

[0109] (2) If there are other business or track maintenance tasks in the previous or subsequent k track cycles, the current task is abandoned.

[0110] For example, after generating the command sequence, a conflict check is performed with the tasks in the current task pool. If there are no imaging, data transmission, or other orbit maintenance tasks within 90 minutes before and after the electric propulsion task, the command is inserted into the command queue; otherwise, the current task is discarded. In the example above, if there is an imaging task at 21674.05s, and the interval between sequences 2 and 3 and this imaging task is less than 90 minutes, then the tasks corresponding to sequences 2 and 3 are discarded, and the tasks of sequences 1 and 4 are inserted into the satellite's task pool and executed in chronological order.

[0111] Those skilled in the art will understand that, besides implementing the system and its various devices, modules, and units provided by this invention in the form of purely computer-readable program code, the same functions can be achieved entirely through logical programming of the method steps, making the system and its various devices, modules, and units of this invention function in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers. Therefore, the system and its various devices, modules, and units provided by this invention can be considered as a hardware component, and the devices, modules, and units included therein for implementing various functions can also be considered as structures within the hardware component; alternatively, the devices, modules, and units for implementing various functions can be considered as both software modules implementing the method and structures within the hardware component.

[0112] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0113] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for planning a semi-autonomous orbit maintenance mission using electric propulsion, characterized in that, include: After the autonomous orbit maintenance mission planning is initiated on the ground, the satellite autonomously calculates the total working time, number of operations, and satellite time of each operation of the thrusters, generates a sequence of continuous multi-orbit orbit maintenance missions, inserts them into the mission queue of the entire satellite, and executes them sequentially according to time. The method includes the following steps: Step S1: After the ground injection command initiates the onboard autonomous orbit maintenance mission planning, the average orbital elements at the corresponding time are calculated based on the current orbital elements, and the time of the most recent arrival at the apogee is recursively obtained. Step S2: Calculate the difference between the current orbital semi-major axis and the nominal orbital semi-major axis, combine the orbital altitude gain per unit time obtained by the satellite mass and electric thruster characteristics, divide the two and round up to obtain the total jet propulsion duration; Step S3: Calculate the allowable operating time of the electric propulsion monorail based on the satellite's energy. Step S4: Calculate the number of times electric propulsion needs to operate based on the total jet propulsion time and the allowable working time of the monorail; Step S5: Based on the closest apogee time, the number of electric propulsion operations, and the duration of single-track operations, generate a sequence of continuous multi-track orbit maintenance missions and insert them into the satellite's mission queue; In step S1, the average orbital elements at the current moment are calculated, and the expression for calculating the time of the most recently arriving stars at their nearest and farthest points is as follows: (1) in: The star time corresponding to the current orbital elements, in seconds; The gravitational constant is 3.98600436 × 10⁻⁶. 14 m 3 / s 2 ; a and M are the mean semi-major axis and the mean anomaly angle of the orbit at the current moment, respectively, in meters and rads. In step S2, the expression for calculating the total jet duration is as follows: (2) in: These are the nominal orbital semi-major axis and the current orbital average semi-major axis, respectively, in meters; The elevation adjustment relative to the nominal track for each track control operation, in meters (m). The orbital height that can be raised per unit time based on the thruster thrust, specific impulse, and satellite mass, expressed in m / s; In step S3, the ground calculates the maximum allowable duration of single-track operation of the electric thruster based on the onboard battery capacity, solar array area, satellite platform power consumption, electric propulsion power consumption, and the illumination and shadow time of the satellite orbit. T c ; In step S4 Based on the total operating time of the thruster and the allowable operating time of the monorail, the number of times the thruster operates is calculated: (3) in: The number of times consecutive opening is allowed; In step S5, the generated orbital maintenance sequence is as follows: T1-Tc / 2 ~ T1+Tc / 2: First ignition; T2 - Tc / 2 ~ T2+ Tc / 2: Second ignition; T3 - Tc / 2 ~ T3+ Tc / 2: 3rd ignition; Tn - Tc / 2 ~ Tn + Tc / 2: The nth ignition; Where: T1=Ta, is the star time corresponding to the nearest successive orbital apogee; T2 = T1 + m × T is the intermediate star time corresponding to the second ignition; T3=T 2 +m×T is the intermediate star corresponding to the 3rd ignition; T n =T n-1 +m×T is the intermediate star corresponding to the nth ignition; T is the orbital period, and ; m is the number of orbits required between two consecutive ignitions, which is related to the satellite's energy balance; Based on the energy balance of the electric propulsion orbit maintenance process, when inserting the autonomously generated electric propulsion mission into the mission queue of the entire satellite, it is necessary to make conflict judgments on the ground injection, autonomously planned electric propulsion missions and business missions. The judgment rules include: -Before and after the electric propulsion mission If there are no imaging, data transmission, or other orbit maintenance tasks during the orbital period, the command queue is inserted. -If before, after If there are other business or track maintenance tasks during the track cycle, the current task will be abandoned.

2. The semi-autonomous orbit maintenance mission planning method using electric propulsion according to claim 1, characterized in that, Based on the required orbital altitude gain and single operational time during the satellite's entire lifespan, the expression for the total number of electric thruster switches used for orbit maintenance throughout the satellite's entire lifespan is as follows: (4) in: These are the orbital altitude decay values ​​corresponding to high, medium, and low solar activity years, in meters; These represent the number of high, medium, and low solar activity years within the satellite's entire design life.

3. A semi-autonomous orbit maintenance mission planning system using electric propulsion, wherein the system executes the semi-autonomous orbit maintenance mission planning method using electric propulsion as described in claim 1 or 2, characterized in that, include: Module M1: After the ground injection command initiates the onboard autonomous orbit maintenance mission planning, it calculates the average orbital elements at the corresponding time based on the current orbital elements, and recursively obtains the time of the most recent arrival at the apogee; Module M2: Calculates the difference between the current orbital semi-major axis and the nominal orbital semi-major axis, and combines the orbital altitude gain per unit time obtained by combining the satellite mass and electric thruster characteristics. Divide the two values ​​and round up to obtain the total jet propulsion duration. Module M3: Calculates the permissible operating time of the electric propulsion monorail based on satellite energy. Module M4: Calculates the number of times electric propulsion needs to operate based on the total jet propulsion time and the allowable operating time of the monorail; Module M5: Based on the nearest apogee time, the number of electric propulsion operations, and the duration of single-track operations, it generates a sequence of continuous multi-track orbit maintenance missions and inserts them into the satellite's mission queue.

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