An ultra-low earth orbit satellite high-precision attitude control system and method

Abstract

The application discloses a kind of ultra-low orbit satellite high-precision attitude control system and method, the system includes: attitude measurement sensitive module, attitude controller and control execution mechanism;Wherein, attitude measurement sensitive module is used to measure the attitude information of current satellite;Attitude controller is used to combine the attitude information of current satellite, using preset control strategy, the control amount input of control execution mechanism is solved;Control execution mechanism is used to generate the moment of influence satellite attitude movement according to control amount input, to control satellite attitude by reaction flywheel control and jet control alternate use mode.This application is based on propulsion system, reaction flywheel and magnetic moment ware, realizes the full interval high-precision high-stability attitude control target for ultra-low orbit satellite.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of super low orbit satellite attitude control, in particular to a super low orbit satellite high-precision attitude control system and method. BACKGROUND

[0002] At present, some super low orbit satellites are launched at home and abroad, and the observation task orbit range is mainly concentrated above 300km. The research on high-precision attitude control of satellites in a lower super low orbit is relatively less. Some people have done theoretical research on high-precision attitude control of satellites in the range of 150-200km. On the basis of reaction wheel control, a pneumatic rudder is added to assist attitude control, and high-precision attitude control is realized. However, the method has high cost, and has not been realized in engineering application.

[0003] The atmospheric density of super low orbit is significantly increased, and the aerodynamic disturbance torque is obviously increased, which can reach 10-1Nm. At present, the satellite in this orbit range is usually controlled by jet to realize three-axis attitude stabilization, but the control precision of this control method is poor, and the stability is not high, the control precision is about 3°, and the stability is about 0.5° / s. SUMMARY

[0004] The present application provides a super low orbit satellite high-precision attitude control system and method to solve the technical problems of poor control precision and low stability in the prior art.

[0005] To solve the above technical problems, the present application provides the following technical solutions:

[0006] On the one hand, the present application provides a super low orbit satellite high-precision attitude control system, which comprises an attitude measurement sensitive module, an attitude controller and a control execution mechanism, wherein,

[0007] The attitude measurement sensitive module is used to measure the attitude information of the current satellite;

[0008] The attitude controller is used to combine the attitude information of the current satellite measured by the attitude measurement sensitive module, adopt a preset control strategy, and calculate the control amount input of the control execution mechanism;

[0009] The control execution mechanism is used to generate a torque affecting the satellite attitude motion according to the control amount input, so as to control the satellite attitude by alternately using reaction flywheel control and jet control.

[0010] Further, the attitude measurement sensitive module comprises a star sensor, a fiber optic gyro assembly, a three-axis magnetometer and a sun sensor assembly.

[0011] Further, the attitude controller is a satellite computer.

[0012] Further, the control execution mechanism comprises a propulsion assembly, a reaction flywheel and a magnetic torque device.

[0013] Further, the preset control strategy comprises:

[0014] When the aerodynamic disturbance torque does not exceed the preset threshold, the reaction flywheel control mode is adopted for attitude control, and the magnetic torque device is used for reaction flywheel angular momentum unloading.

[0015] When the aerodynamic disturbance torque exceeds the preset threshold, the ground judges whether to switch the attitude control mode to the jet control; when the ground judges that the jet control is the attitude control mode, the satellite enters the jet control mode, the reaction flywheel is maintained at the nominal speed, and the jet control mode is adopted to realize the three-axis attitude control of the satellite.

[0016] When the load observation time is received, the attitude controller calculates the time to cut into the reaction flywheel control mode, and when the switching time arrives, the satellite autonomously cuts into the reaction flywheel control mode, at which time the jet control stops; when the load observation task is completed, the satellite cuts into the jet control mode, at which time the reaction flywheel speed is pulled back to the nominal speed to achieve the purpose of reaction flywheel angular momentum unloading; waiting for the next load observation task; wherein when the duration of the reaction flywheel control mode exceeds the preset duration, the attitude control mode is forcibly switched to the jet control mode, and the reaction flywheel is pulled to the nominal speed.

[0017] Further, the calculation of the time to cut into the reaction flywheel control mode comprises:

[0018] The dynamic time to reach the observation pointing accuracy and stability of the load is calculated:

[0019] T=Hrem / (k1*Tc)+t

[0020] Wherein, T represents the dynamic time to reach the observation pointing accuracy and stability of the load; Hrem is the residual angular momentum of the whole satellite when switching from the jet control mode to the reaction flywheel control mode, Tc is the three-axis control torque amplitude of the satellite that can be provided by the reaction flywheel, k1 is the torque gain, k1 < 1, usually k1 = 0.8-0.6, and t is the steady-state convergence time.

[0021] According to the calculated dynamic time T, the time to cut into the reaction flywheel control mode is determined.

[0022] Further, the calculation formula of the duration is:

[0023] Twheel=(Hwheel-Hrem) / (k2*Td)

[0024] Wherein, Twheel represents the duration; Hwheel is the single-axis angular momentum provided by the reaction flywheel, Hrem is the residual angular momentum of the whole satellite when switching from the jet control mode to the reaction flywheel control mode, k2 is the interference torque coefficient, k2>1, the value range of k2 is 1.6-1.8, and Td is the order of magnitude of the interference torque.

[0025] In another aspect, the application also provides a high-precision attitude control method of a super low orbit satellite, which is realized by using the high-precision attitude control system of the super low orbit satellite.

[0026] When the aerodynamic interference torque does not exceed the preset threshold, the reaction flywheel control mode is used for attitude control, and the magnetic torque device is used for reaction flywheel angular momentum unloading.

[0027] When the aerodynamic interference torque exceeds the preset threshold, it is judged on the ground whether to switch the attitude control mode to the jet control; after the ground judges that the jet control is used as the attitude control mode, the satellite enters the jet control mode, the reaction flywheel is maintained at the nominal speed, and the jet control mode is used to realize the three-axis attitude control of the satellite.

[0028] When the load observation time is received, the attitude controller calculates the time of switching to the reaction flywheel control mode, and when the switching time arrives, the satellite autonomously switches to the reaction flywheel control mode, at which time the jet control stops; after the load observation task is completed, the satellite immediately switches to the jet control mode, at which time the reaction flywheel speed is pulled back to the nominal speed, so as to achieve the purpose of reaction flywheel angular momentum unloading; waiting for the next load observation task; wherein, when the duration of the reaction flywheel control mode exceeds the preset duration, the attitude control mode is forcibly switched to the jet control mode, and the reaction flywheel is pulled to the nominal speed.

[0029] The technical scheme provided by the application has at least the following beneficial effects:

[0030] 1. The reaction flywheel control and jet control alternately used method can realize the high-precision and high-stability attitude control target in the super low orbit interval, and further widens the range of load observation.

[0031] 2. Compared with the jet unloading method, the method of directly pulling the reaction flywheel speed back to the nominal speed has more obvious advantages. After the method is used, the reaction flywheel angular momentum capacity is controllable, the duration of the reaction flywheel control can be accurately calculated, and the control effect is better. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0033] Figure 1 is a block diagram of a high-precision attitude control system of an ultra-low orbit satellite provided by the embodiments of the present application.

[0034] Figure 2 is a principle diagram of a high-precision attitude control method of an ultra-low orbit satellite provided by the embodiments of the present application. DETAILED DESCRIPTION

[0035] In order to make the objects, technical solutions and advantages of the present application more clear, the embodiments of the present application will be further described in detail below with reference to the drawings.

[0036] The embodiments of the present application provide a high-precision attitude control system of an ultra-low orbit satellite, which is particularly suitable for satellites running in an ultra-low orbit and having high-precision and high-stability attitude control requirements. The system includes two parts of attitude control hardware and attitude control software. As shown in Figure 1 the hardware part mainly includes an attitude measurement sensitive module, an attitude controller and a control execution mechanism; the attitude measurement sensitive module includes a star sensor, a fiber-optic gyro assembly, a three-axis magnetometer and a sun sensor assembly; the attitude controller is a satellite computer; the control execution mechanism includes a propulsion assembly, a reaction flywheel and a magnetic torque device; the attitude measurement sensitive module is used to measure the attitude information of the current satellite; the attitude controller is used to calculate the control amount input of the control execution mechanism according to the preset control strategy and the attitude control algorithm combined with the attitude information of the current satellite measured by the attitude measurement sensitive module; and the control execution mechanism is used to generate a moment affecting the attitude movement of the satellite according to the control amount input, so as to control the satellite attitude in a manner that the reaction flywheel control and the jet control are used alternately.

[0037] Specifically, the control strategy used in the embodiments of the present application is as follows:

[0038] When the aerodynamic disturbance torque is relatively small, the reaction flywheel can be used for long-term attitude control, and the magnetic torque device is used for reaction flywheel angular momentum unloading. In this orbit interval, high-precision and high-stability attitude control objectives can be achieved through reaction flywheel control. With the gradual decrease of the orbit height, the aerodynamic disturbance torque gradually increases, and the magnetic torque device cannot unload the angular momentum of the reaction flywheel in time, resulting in angular momentum saturation and loss of control ability of the reaction flywheel. Therefore, when the satellite orbit height decreases to a certain range, the ground needs to determine whether to switch the main control method to jet control. When the ground determines to use jet control as the main control method, the satellite enters the long-term jet control mode, the reaction flywheel is maintained at the nominal speed, and jet control is used to achieve three-axis attitude stabilization control of the satellite; when the load observation time is received, the on-board autonomous calculation cuts in the time of wheel control, and the switching time arrives, then the satellite autonomously cuts in the reaction flywheel control mode, at which time the jet control stops; when the load observation task is completed, the satellite cuts in the jet control, at which time the reaction flywheel speed is slowly pulled back to the nominal speed, achieving the purpose of reaction flywheel angular momentum unloading. Wait for the next load observation task. The specific implementation process is shown in Figure 2 The calculation of the switching time is as follows:

[0039] When switching from jet control to reaction flywheel control, the attitude control precision and stability of the satellite gradually improve, and it takes a dynamic time T to reach the observation pointing precision and stability of the load. Accurate calculation of the dynamic time T is the key to switching. The calculation method of the dynamic time T is as follows:

[0040] T = Hrem / (k1*Tc) + t

[0041] Wherein, Hrem is the residual angular momentum of the whole satellite when switching from jet control mode to reaction flywheel control mode, Tc is the three-axis control torque amplitude of the satellite that can be provided by the reaction flywheel, k1 is the torque gain, k1 < 1, usually k1 = 0.8-0.6, t is the steady-state convergence time, usually about 20-30s, which can be determined through simulation.

[0042] Further, the calculation method of the wheel control duration Twheel is as follows:

[0043] Twheel = (Hwheel-Hrem) / (k2*Td)

[0044] Wherein, Hwheel is the single-axis angular momentum that can be provided by the reaction flywheel, k2 is the disturbance torque coefficient, usually k2 > 1, the value range of k2 is 1.6-1.8, and Td is the order of magnitude of the disturbance torque.

[0045] When the wheel control time exceeds Twheel, forced switching to jet control is needed while the reaction flywheel is pulled to the nominal speed. In this way, the reaction flywheel angular momentum saturation is prevented, which leads to the satellite attitude out of control.

[0046] In summary, the embodiment provides a kind of super low orbit satellite high-precision attitude control system and method, using the method of this reaction flywheel control and jet control alternate use of the embodiment can be realized in super low orbit interval high-precision high-stability attitude control goal, further widen the range of load observation.And compared to the method of jet unloading, the method of the reaction flywheel speed directly pulled back to the nominal speed used in the embodiment has more obvious advantages. After using the super low orbit satellite high-precision attitude control method of the embodiment, the reaction flywheel angular momentum capacity is controllable, and the reaction flywheel continuous control time can be accurately calculated, and the control effect is better.It is especially suitable for the satellite running in super low orbit and having high-precision high-stability attitude control demand.

[0047] In addition, it should be noted that the present application can be provided as a method, device or computer program product. Therefore, the embodiments of the present application can adopt a completely hardware embodiment, a completely software embodiment or an embodiment combining software and hardware aspects. Moreover, the embodiments of the present application can adopt the form of a computer program product implemented on one or more computer usable storage media containing computer usable program codes.

[0048] The embodiments of the present application are described with reference to flowcharts and / or block diagrams according to the method, terminal device (system) and computer program product of the embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of the flows and / or blocks in the flowcharts and / or block diagrams can be realized by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, embedded processor or other programmable data processing terminal device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing terminal device produce a means for implementing the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in one flow or multiple flows and / or blocks Figure 1 The device for realizing the functions specified in one block or multiple blocks.

[0049] These computer program instructions can also be stored in a computer readable storage medium that can guide the computer or other programmable data processing terminal device to work in a specific way, so that the instructions stored in the computer readable storage medium produce a product including instruction devices, which realize the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in one flow or multiple flows and / or blocks Figure 1The computer program instructions can also be loaded onto a computer or other programmable data processing terminal device to cause a series of operational steps to be performed on the computer or other programmable terminal device to produce a computer implemented process such that the instructions which execute on the computer or other programmable terminal device provide steps for implementing the flow Figure 1 The computer program instructions can also be loaded onto a computer or other programmable data processing terminal device to cause a series of operational steps to be performed on the computer or other programmable terminal device to produce a computer implemented process such that the instructions which execute on the computer or other programmable terminal device provide steps for implementing the flow Figure 1 The computer program instructions can also be loaded onto a computer or other programmable data processing terminal device to cause a series of operational steps to be performed on the computer or other programmable terminal device to produce a computer implemented process such that the instructions which execute on the computer or other programmable terminal device provide steps for implementing the flow

[0050] It is also noted that the aforementioned embodiments can be implemented in such computer languages as C, C++, Java, etc., and that each said program can be stored on a computer usable medium, i.e. RAM memory, magnetic disk, etc., when the programs are used to direct the functions of a computer or other programmable terminal device, and that these computer program instructions can also be downloaded to a computer or other programmable terminal device to cause a series of operational steps to be performed on the computer or other programmable terminal device to produce a computer implemented process, such that the instructions which execute on the computer or other programmable terminal device provide steps for implementing the flow

[0051] Finally, it is to be understood that the above-described arrangements are simply certain embodiments of the application and that many additions and modifications can be made within the scope of the present application as set forth in the appended claims.

Claims

1. An ultra-low orbit satellite high-precision attitude control system, characterized in that, The attitude control system comprises an attitude measurement sensitive module, an attitude controller and a control execution mechanism, wherein The attitude measurement sensitive module is used for measuring the attitude information of the current satellite; The attitude controller is used for combining the attitude information of the current satellite measured by the attitude measurement sensitive module, adopting a preset control strategy, and calculating the control quantity input of the control execution mechanism; The control execution mechanism is used for generating a moment affecting the satellite attitude movement according to the control quantity input, so as to control the satellite attitude in a manner that the reaction flywheel control and the jet control are used alternately; The preset control strategy comprises: When the aerodynamic interference moment does not exceed a preset threshold, the reaction flywheel control is adopted to control the attitude, and the magnetic moment device is used for reaction flywheel angular momentum unloading; When the aerodynamic interference moment exceeds the preset threshold, the ground judges whether to switch the attitude control mode to the jet control; when the ground judges that the jet control is used as the attitude control mode, the satellite enters the jet control mode, the reaction flywheel is maintained at a nominal speed, and the jet control is adopted to realize the three-axis attitude control of the satellite; When the load observation time is received, the attitude controller calculates the time of cutting into the reaction flywheel control mode; when the switching time arrives, the satellite autonomously cuts into the reaction flywheel control mode, at this time, the jet control is stopped; when the load observation task is completed, the satellite cuts into the jet control mode, at this time, the reaction flywheel speed is pulled back to the nominal speed, so as to achieve the purpose of reaction flywheel angular momentum unloading; the next load observation task is waited for; wherein, when the duration of the reaction flywheel control mode exceeds a preset duration, the attitude control mode is forcibly switched to the jet control mode, and the reaction flywheel is pulled to the nominal speed.

2. The ultra-low orbit satellite high-precision attitude control system of claim 1, wherein, The attitude measurement sensitive module comprises a star sensor, a fiber-optic gyro assembly, a three-axis magnetometer and a sun sensor assembly.

3. The ultra-low orbit satellite high-precision attitude control system of claim 1, wherein, The attitude controller is a satellite-borne computer.

4. The ultra-low orbit satellite high-precision attitude control system of claim 1, wherein, The control execution mechanism comprises a propulsion assembly, a reaction flywheel and a magnetic moment device.

5. The ultra-low Earth orbit satellite high-precision attitude control system of claim 1, wherein, The calculation of the time of cutting into the reaction flywheel control mode comprises: The dynamic time of reaching the observation pointing accuracy and stability of the load is calculated: T=Hrem / (k1*Tc)+t wherein, T represents the dynamic time of reaching the observation pointing accuracy and stability of the load; Hrem is the residual angular momentum of the whole satellite when the jet control mode is switched to the reaction flywheel control mode, Tc is the satellite three-axis control moment amplitude that can be provided by the reaction flywheel, k1 is the moment gain, k1<1, and t is the steady-state convergence time; According to the calculated dynamic time T, the time of cutting into the reaction flywheel control mode is determined.

6. The ultra-low orbit satellite high-precision attitude control system of claim 1, wherein, The calculation formula of the duration is: Twheel=(Hwheel-Hrem) / (k2*Td) wherein, Twheel represents the duration; Hwheel is the single-axis angular momentum that can be provided by the reaction flywheel, Hrem is the residual angular momentum of the whole satellite when the jet control mode is switched to the reaction flywheel control mode, k2 is the interference moment coefficient, k2>1, the value range of k2 is 1.6-1.8, and Td is the order of magnitude of the interference moment.

7. A high-precision attitude control method for ultra-low orbit satellites, implemented by using the high-precision attitude control system for ultra-low orbit satellites according to any one of claims 1 to 6, characterized in that, The control method comprises: When the aerodynamic disturbance torque does not exceed the preset threshold, the reaction flywheel control mode is adopted for attitude control, and the magnetic torque device is used for reaction flywheel angular momentum unloading; When the aerodynamic disturbance torque exceeds the preset threshold, the ground judges whether to switch the attitude control mode to the jet control; when the ground judges that the jet control is used as the attitude control mode, the satellite enters the jet control mode, the reaction flywheel is maintained at the nominal speed, and the jet control mode is adopted to realize the three-axis attitude control of the satellite; When the load observation time is received, the attitude controller calculates the time of switching to the reaction flywheel control mode, and when the switching time arrives, the satellite autonomously switches to the reaction flywheel control mode, at which time the jet control stops; when the load observation task is completed, the satellite immediately switches to the jet control mode, at which time the reaction flywheel speed is pulled back to the nominal speed, so as to achieve the purpose of reaction flywheel angular momentum unloading; and the next load observation task is waited for; wherein when the duration of the reaction flywheel control mode exceeds the preset duration, the attitude control mode is forcibly switched to the jet control mode, and at the same time, the reaction flywheel is pulled to the nominal speed.

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