Satellite ground simulation system and method based on absolute orbit dynamics

Abstract

The application discloses a satellite ground simulation system and method based on absolute orbit dynamics, relates to the technical field of dynamic spacecraft ground simulation, and comprises the following steps: determining the space-time scale ratio between an actual space orbit and a space ground simulator; acquiring the spatial position and attitude of the space ground simulator; generating thrust through jetting to control the space ground simulator to move according to a preset track; obtaining the size of a nonlinear force of the space ground simulator according to the preset space-time scale ratio; calculating the size and direction of a compensation thrust expected to be provided by a fan after the space-time scale ratio; obtaining the current position of a rotating shaft through a visual camera array, and moving the fan to the calculated expected position through the rotating shaft; and controlling the fan to start working according to the expected force size to compensate for the nonlinear force under the absolute orbit dynamics. Therefore, by using the above method, the spacecraft long-distance approaching experiment environment is closer to the real working condition, the satellite ground simulation experiment is realized, and the reliability is enhanced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of dynamic spacecraft ground simulation technology, in particular to a satellite ground simulation system and method based on absolute orbit dynamics. BACKGROUND

[0002] With the rapid development of space technology, the space missions carried out tend to be diverse, such as on-orbit docking of satellites and spacecraft, construction and maintenance of space stations, and space robot activities. Due to the high cost and special importance of these space missions, they must have high safety and reliability. When a spacecraft is launched from the earth into space, it will face many uncertain environmental conditions and unfavorable factors, such as microgravity, electromagnetic radiation, micro-meteoroids and space debris. To solve the above problems, high-precision zero-gravity ground simulation tests are needed to ensure the feasibility and effectiveness of various key technologies on the satellite.

[0003] The air floatation method can form a closed-loop control of the attitude and orbit maneuver motion control of the satellite simulator and the actual motion position and attitude, has strong maneuver tracking capability for the space flight simulator, and high position and attitude positioning accuracy, and can meet the functional and performance testing of various space instruments and equipment under zero gravity, and meet the ground test and testing work of various space products before being launched into space.

[0004] Currently, the spacecraft zero-gravity ground simulation technology is basically based on relative orbit dynamics. When one spacecraft approaches another spacecraft at a close distance, the nonlinear term in the C-W equation can be approximately ignored, but once the spacecraft approaches another spacecraft at a long distance, the nonlinear term cannot be ignored, and it is very difficult to simulate the nonlinear term of the C-W equation on the ground. Therefore, the existing technical solutions cannot realize the long-distance approaching ground zero-gravity simulation test, and it is urgent to design a spacecraft simulator based on absolute orbit dynamics, which can better restore the working conditions during the long-distance approaching test. SUMMARY

[0005] The purpose of the present application is to provide a satellite ground simulation system and method based on absolute orbit dynamics, which can better restore the working conditions during the long-distance approaching test and improve the response speed and response frequency of the ground simulation.

[0006] To achieve the above purpose, the present application provides a satellite ground simulation method based on absolute orbit dynamics, comprising the following steps:

[0007] S1, before the experiment starts, determining the space-time scaling ratio between the actual space orbit and the space ground simulator;

[0008] S2, acquiring the spatial position and attitude of the space ground simulator through a visual camera array;

[0009] S3, generating thrust by air jet, controlling the space ground simulator to move according to the preset trajectory;

[0010] S4, according to the preset space-time ratio, obtaining the distance between the space ground simulator and the target by the on-board computer, then calculating the actual space distance, and calculating the size of the non-linear force according to the actual space distance;

[0011] S5, calculating the size and direction of the compensation thrust expected to be provided by the fan after the space-time ratio;

[0012] S6, obtaining the current position of the rotating shaft by the visual camera array, and moving the fan to the calculated expected position by the rotating shaft;

[0013] S7, controlling the fan to start working according to the expected force, and compensating the non-linear force under the absolute orbit dynamics.

[0014] Preferably, step S2 comprises:

[0015] S21, attaching target balls on the space ground simulator and the fan rotating shaft;

[0016] S22, calibrating the visual camera array to ensure the accuracy of the visual camera array;

[0017] S23, establishing the coordinate system of the field of view.

[0018] Preferably, in step S4, the non-linear perturbation force is calculated by using the actual space distance, comprising:

[0019] Total perturbation force F total is:

[0020] F total = F gravity + F pert

[0021] Earth's gravity on the spacecraft F gravity is:

[0022]

[0023] In the formula, G is the gravitational constant, M is the mass of the earth, m is the mass of the spacecraft, and d is the distance between the spacecraft and the center of the earth;

[0024] Nonlinear effect perturbation force F pert is:

[0025] F pert = a J2 ·m

[0026]

[0027] wherein a J2 is the perturbed gravitational acceleration of J2, R e is the equatorial radius of the earth, J2 is the second order gravitational field coefficient of the celestial body, z is the coordinate of the spacecraft in the vertical direction, is the radial unit vector, is the vertical unit vector.

[0028] Preferably, in step S5, the calculation of the compensation thrust size and direction comprises:

[0029] According to the positions of the spacecraft and the target, the unit vectors are calculated as:

[0030]

[0031] wherein r target , r sat are the position vectors of the target and the spacecraft respectively;

[0032] The compensation thrust size calculation:

[0033]

[0034] wherein F comp is the compensation thrust;

[0035] wherein the thrust components in each direction are:

[0036]

[0037] wherein F comp,x , F comp,y , F comp,z are the compensation thrust sizes in the x-axis, y-axis, and z-axis directions respectively, are the unit vectors in the x-axis, y-axis, and z-axis directions respectively;

[0038] According to the designed space-time scaling ratio, the compensation thrust components in each direction obtained by calculation are converted into the thrust size expected to be provided by the fan.

[0039] Preferably, step S7 comprises a serial communication module and a control element, and the steps are as follows:

[0040] S71, turn on the onboard computer serial communication module;

[0041] S72, transmit the nonlinear compensation force size calculated by the onboard computer to the fan;

[0042] S73, control the fan to move at the expected speed using the control element.

[0043] Preferably, the non-linear force compensation thrust of the single fan is obtained according to the position of the corresponding aerospace ground simulator during the formation movement of the aerospace ground simulator.

[0044] The satellite ground simulation system based on absolute orbit dynamics comprises a control module, a ground satellite simulation module and a satellite state acquisition module.

[0045] The control module comprises an airborne computer for simulating ground control.

[0046] The ground satellite simulation module comprises a ground zero-gravity platform, an aerospace ground simulator, an air foot, an electromagnetic valve, a nozzle, a reaction flywheel, a rotating shaft and a fan.

[0047] The satellite state acquisition module comprises a visual camera array arranged outside the ground satellite simulation module.

[0048] Preferably, the airborne computer, the reaction flywheel, the electromagnetic valve, the nozzle and the fan move according to a work flow.

[0049] Therefore, the satellite ground simulation method based on absolute orbit dynamics has the following technical effects:

[0050] (1) The satellite ground simulation method based on absolute orbit dynamics realizes an experimental environment closer to the real working condition for spacecraft remote approach, makes the ground simulation result more persuasive, and is easy to improve on the basis of an existing satellite simulator based on relative orbit dynamics, thereby reducing the cost.

[0051] (2) According to the different positions of the satellite simulator, the central rotating shaft and the fan of the simulator are dynamically adjusted to be real-time aligned with the earth center of mass, so as to ensure the dynamic environment and improve the real effectiveness of the spacecraft ground zero-gravity simulation experiment.

[0052] The technical solutions of the present application will be further described in detail below with reference to the drawings and embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0053] Figure 1 is a perspective view of the satellite ground simulation system and method based on absolute orbit dynamics;

[0054] Figure 2 is a schematic view of the overall work of the satellite ground simulation system and method based on absolute orbit dynamics.

[0055] REFERENCE NUMERALS

[0056] 1, aerospace simulator; 2, rotating shaft; 3, fan; 4, ground zero-gravity platform; 5, visual camera array. DETAILED DESCRIPTION

[0057] The application will be explained in more detail by the following examples, the purpose of which is to protect all changes and improvements within the scope of the application, and the application is not limited to the following examples.

[0058] As Figure 1 indicated, the satellite ground simulation system and method based on absolute orbit dynamics provided by the application comprises:

[0059] The space ground simulator 1 is provided with a high-pressure gas cylinder, and cold gas jet is used to realize the movement of the space ground simulator 1 along the expected trajectory; and the space ground simulator 1 is provided with a porous gas foot at the bottom, and after aeration, a gas film with high stiffness and almost zero friction is generated to offset the gravity of the space ground simulator itself, so as to realize zero gravity environment on the ground; since the porous structure of the gas foot is easy to be blocked by dust and other small impurities, the entire space ground simulator works on a smooth zero-gravity marble air floating platform.

[0060] The space ground simulator 1 is provided with a reaction flywheel as an attitude actuator to realize the expected attitude of the space ground simulator 1; eight nozzles are symmetrically installed on the space ground simulator 1, which can realize the translation and rotation of the plane. The on-board computer is powered by lithium batteries, the USB interface of the on-board computer is connected with a USB-to-RS485 serial communication module, and the control instructions are sent through the module to control the on-off of the electromagnetic valve installed on the top of the space ground simulator 1; the gas pressure preset in the pipeline in the space ground simulator 1 is used to generate thrust from the nozzles; due to the existence of the gas film, the friction between the space ground simulator and the zero-gravity marble air floating platform is almost 0, so although the cold gas jet can only provide a small thrust, the movement of the entire space floating simulator can still be realized.

[0061] The specific process is as follows:

[0062] (1) Before the experiment starts, the space-time scaling ratio between the actual space orbit and the space ground simulator 1 is set according to the parameters of the planned orbit and the ground zero-gravity simulation conditions, which is used to connect the ground simulation space with the actual space, and is adjusted according to the actual situation in the actual application scene; based on the space-time scaling ratio, the real space distance and time in space are equivalent to the ground simulation distance and time, and the shaft 2 and the fan 3 are set in the space ground simulator 1, the shaft is used to align the space ground simulator 1 to the earth center at all times, and the fan is used to provide a nonlinear force for simulating the earth gravity and perturbation force.

[0063] (2) The spatial position and attitude of the space ground simulator are acquired by the vision camera array 5, and the target balls are pasted on the space ground simulator 1 and the shaft of the fan 3, the vision camera array 5 is calibrated, and the coordinate system of the field of view is established.

[0064] (3) The space ground simulator 1 moves according to the preset trajectory by generating thrust through the air jets.

[0065] (4) According to the preset space-time scaling ratio, the onboard computer calculates the actual distance in space according to the distance between the space ground simulator 1 and the target, and calculates the size of the non-linear force according to the actual distance, including the following steps:

[0066] The gravitational force of the Earth on the spacecraft F gravity is:

[0067]

[0068] In the formula, G is the gravitational constant, M is the mass of the Earth, m is the mass of the spacecraft, and d is the distance between the spacecraft and the center of the Earth, i.e. the actual distance in space;

[0069] The perturbation force F of the non-linear effect pert is:

[0070] F pert = a J2 ·m

[0071]

[0072] In the formula, a J2 is the J2 perturbation gravitational acceleration, R e is the equatorial radius of the Earth, J2 is the second-order gravitational field coefficient of the celestial body, z is the vertical coordinate of the spacecraft, is the radial unit vector, is the vertical unit vector.

[0073] In summary, the total perturbation force F total is:

[0074] F total = F gravity +F pert

[0075] By the above method, the orbit perturbation force in the Earth's inertial coordinate system is used as the non-linear force to realize satellite ground simulation of absolute orbit dynamics, avoiding the problem that the C-W equation cannot be obtained in the relative absolute orbit dynamics satellite ground simulation in the process of approaching at a long distance, and improving the simulation accuracy and effectiveness.

[0076] (5) After calculating the space-time scaling ratio, the size and direction of the compensation thrust expected to be provided by the fan are calculated, as follows:

[0077] First, according to the positions of the spacecraft and the target, the unit vector is:

[0078]

[0079] wherein r target , r sat are target position vector, spacecraft position vector respectively;

[0080] Then, the compensation thrust size is calculated:

[0081]

[0082] wherein F comp is compensation thrust;

[0083] wherein the thrust component in each direction is:

[0084]

[0085] wherein F comp,x , F comp,y , F comp,z are compensation thrust size in x-axis, y-axis, z-axis direction respectively, are unit vector in x-axis, y-axis, z-axis direction respectively;

[0086] According to the designed space-time scaling ratio, the compensation thrust component in each direction calculated is converted into the thrust size expected to be provided by the fan.

[0087] (6) The current position of the rotation shaft is obtained through the vision camera array 5, and the fan is moved to the calculated expected position through the rotation shaft

[0088] (7) The fan starts to work according to the size of the expected thrust, realizing the nonlinear force compensation under the absolute orbit dynamics.

[0089] Through the above method, the space-time scaling ground zero gravity experiment under the absolute orbit dynamics of a single space ground simulator 1 can be realized.

[0090] As Figure 2As shown, with the continuous progress of aerospace technology, the application of spacecraft formation is more and more extensive, and the necessity and importance of ground test verification of the spacecraft formation approaching the target are more and more obvious. Another use of the embodiment is to realize that the spacecraft formation approaches the target, and the realization process of a single spacecraft in the spacecraft formation is consistent with the above. In addition, it is necessary to determine the configuration of the formation, and obtain the position and attitude of each spacecraft simulator through the visual camera array 5; according to the preset configuration of the spacecraft simulator, the time of the jet of the eight electromagnetic valves is calculated in real time respectively, and the preset spacecraft formation configuration is realized; after all the spacecraft simulators successfully realize the preset configuration, run above the ground zero-gravity platform 4, the ground zero-gravity platform 4 in the embodiment adopts a zero-gravity marble air floating platform; because the friction between the spacecraft simulator air foot and the zero-gravity marble air floating platform is almost 0, although the zero-gravity air floating platform has only a very small angle, it may still cause the entire spacecraft floating platform to deviate; in order to ensure the accuracy of the formation configuration, the position and attitude of each spacecraft simulator can be obtained through the visual camera array 5, and the spacecraft simulator is corrected in configuration through the jet of the nozzle and the reaction flywheel; at the same time, according to the preset space-time ratio, the size and direction of the non-linear force that needs to be compensated by the fan are calculated inversely, and after the position of the shaft is obtained through the visual camera, the fan is controlled to work with a specified size of force to compensate the force of the spacecraft in the real space.

[0091] Therefore, the satellite ground simulation system and method based on absolute orbit dynamics can make the experimental environment of the spacecraft approaching another spacecraft at a long distance closer to the real working condition, enhance the persuasiveness of the ground simulation experiment results, have fast response speed, high response frequency, simple structure, small occupied space, and are convenient to maintain.

[0092] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application but not to limit them, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can still be modified or replaced by equivalents, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A satellite ground simulation method based on absolute orbital dynamics, characterized in that: The following steps are involved: S1. Determine the time and space reduction ratio between the actual space trajectory and the space ground simulator; S2, obtain the spatial position and attitude of the aerospace ground simulator through the visual camera array; S3, generating thrust through jets to control the aerospace ground simulator to move along a preset trajectory; S4. According to the preset time-space reduction ratio, the distance between the aerospace ground simulator and the target is obtained through the onboard computer, and then the distance in real space is reversed and the magnitude of the nonlinear force is calculated based on the distance in real space; Using real-space distances, calculate nonlinear perturbation forces, including: Total power for: Earth's gravitational pull on spacecraft for: Where, is the gravitational constant, is the mass of the Earth, is the mass of the spacecraft, is the distance between the spacecraft and the center of the Earth; Perturbation force of nonlinear effects for: Where, is the J2 perturbation gravitational acceleration, is the equatorial radius of the Earth, is the second-order gravitational field coefficient of the celestial body, is the vertical coordinate of the spacecraft, is the radial unit vector, is the unit vector in the vertical direction; S5. Calculating the magnitude and direction of the compensatory thrust that the fan is expected to provide after the time-space reduction ratio; The calculation of the magnitude and direction of the compensatory thrust includes: Calculate the unit vector based on the position of the spacecraft and the target for: Where, 、 are the target position vector and the spacecraft position vector respectively; Compensation thrust calculation: Where, To compensate for thrust; Among them, the compensatory thrust components in each direction are: Where, 、 、 They are the compensation thrust in the x-axis, y-axis and z-axis directions respectively. 、 、 are the unit vectors in the directions of the x-axis, y-axis, and z-axis respectively; According to the designed time-space reduction ratio, the calculated compensatory thrust components in each direction are converted into the thrust size expected to be provided by the fan; S6. Obtain the current position of the shaft through the visual camera array, and move the fan to the calculated desired position through the shaft; S7. Control the fan to start working according to the magnitude of the desired force, and compensate for the nonlinear force under the absolute orbital dynamics.

2. The satellite ground simulation method based on absolute orbital dynamics according to claim 1, characterized in that: Step S2 includes: S21. Attach target balls to the aerospace ground simulator and fan shaft; S22, calibrating the visual camera array; S23. Establish a coordinate system for the field of view.

3. The satellite ground simulation method based on absolute orbital dynamics according to claim 1, characterized in that: Step S7 includes: S71. Open the onboard computer serial communication module; S72, transmitting the magnitude of the nonlinear compensation force calculated by the onboard computer to the fan; S73: Use the control element to control the fan to move at a desired speed.

4. The satellite ground simulation method based on absolute orbital dynamics according to any one of claims 1 to 3, characterized in that: During the formation motion of the aerospace ground simulator, the nonlinear force compensation thrust of a single fan is obtained according to the position of the corresponding aerospace ground simulator.

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