Ground verification device and method for spacecraft centroid on-orbit identification technology

Abstract

The invention discloses a spacecraft mass center on-orbit identification technology ground verification device and method. The spacecraft centroid on-orbit identification technology ground verification device comprises a centroid measuring platform, a driving mechanism, an accelerometer and a centroid adjusting mechanism, the centroid measuring platform comprises a torsional pendulum platform, a torsional pendulum base and a suspension wire, the torsional pendulum platform is used for placing a spacecraft simulator, and only the degree of freedom of rotation around the gravity direction is reserved between the torsional pendulum platform and the torsional pendulum base; the centroid measuring platform comprises a torsional pendulum platform and a torsional pendulum base, the torsional pendulum platform and the torsional pendulum base are connected through a suspension wire, the motion state of a spacecraft in orbit is simulated, the acceleration of the spacecraft is measured through an accelerometer, the centroid position is calculated, and the centroid position of the spacecraft simulator is adjusted through a centroid adjusting device. And the rotation center of the spacecraft simulator is equivalent to the mass center of the spacecraft in orbit.

Description

Technical Field

[0001] The present application relates to the field of aerospace technology, and in particular to a ground verification device and method for in-orbit identification technology of a spacecraft center of mass. Background Art

[0002] Among the related technologies, accurately establishing the Earth's gravity field model is of great significance to the fields of Earth geodesy, ocean science, seismology, resource exploration, etc. A high-precision gravity spacecraft is one of the necessary equipment for establishing an accurate Earth's gravity field model. To ensure the accurate measurement of the Earth's gravity, it is necessary to accurately remove other non-conservative forces besides the Earth's gravity, and ensure that the center of mass position of the gravity spacecraft and the detection center position of the accelerometer test mass are within a certain range. This is a key technical challenge.

[0003] While a spacecraft is in orbit, factors such as structural deformation, material outgassing, and propellant consumption will cause the spacecraft's center of mass to change relative to the spacecraft frame. The accelerometer and the spacecraft frame are approximately rigidly connected, so the actual position of the accelerometer's test mass center of mass and the spacecraft's center of mass in orbit will change over time.

[0004] However, compared with the on-orbit working environment of spacecraft, spacecraft are affected by gravity factors in ground experiments. This is because the earth's gravity will have a significant impact on the movement and balance of spacecraft. In ground experiments, it is difficult for spacecraft to reproduce the actual operating state in orbit. The influence of the earth's gravity causes its behavior to be different from that in orbit. This situation affects the accurate identification and adjustment of the center of mass position.

[0005] Therefore, when conducting the ground equivalent verification scheme of center of mass identification and adjustment, it is difficult to simulate the state of the spacecraft when it is in orbit in the ground verification test. Summary of the invention

[0006] The present application aims to solve at least one of the technical problems existing in the prior art. To this end, the present application proposes a ground verification method for on-orbit identification technology of a spacecraft mass center, which can simulate the state of a spacecraft on-orbit during a ground verification experiment.

[0007] The present application also proposes a spacecraft center of mass on-orbit technology ground verification device for implementing the above-mentioned spacecraft center of mass on-orbit technology ground verification method.

[0008] According to the first aspect of the present application, a ground verification method for on-orbit identification of a spacecraft mass center includes the following steps:

[0009] Setting a centroid measurement platform, limiting the degree of freedom of the centroid measurement platform, so that the centroid measurement platform only retains the degree of freedom of rotation around the direction of gravity;

[0010] The spacecraft simulator is placed on the mass center measurement platform, and the mass center position of the spacecraft simulator is measured using a mass center inertia measuring instrument. An accelerometer and an attitude measuring instrument are arranged above the mass center measurement platform, and the accelerometer has a measurement center. The mass center position of the spacecraft simulator is offset from the position of the measurement center, that is, the mass center position of the spacecraft simulator has a deviation from the position of the measurement center;

[0011] Applying torque excitation to the spacecraft simulator to cause the spacecraft simulator to generate periodic oscillations on the center of mass measurement platform;

[0012] Using the attitude measuring instrument to measure the attitude of the swinging spacecraft simulator, and using the accelerometer to measure the linear acceleration of the spacecraft simulator at the center of the accelerometer;

[0013] By measuring the attitude and acceleration of the spacecraft simulator, the center of mass position of the spacecraft simulator at this time is calculated;

[0014] According to the calculated center of mass position, the center of mass position of the spacecraft simulator is adjusted to control the deviation between the center of mass of the spacecraft simulator and the center of the accelerometer, that is, to control the distance between the center of mass of the spacecraft simulator and the center of the accelerometer.

[0015] The ground verification method of the spacecraft center of mass on-orbit identification technology according to the embodiment of the present application has at least the following beneficial effects:

[0016] By setting up a center of mass measurement platform and placing the spacecraft simulator on the center of mass measurement platform, the spacecraft simulator can perform torsional pendulum motion on the center of mass measurement platform. By measuring various parameters of the spacecraft during the torsion and pendulum, the center of mass position of the spacecraft simulator can be calculated through the measured parameters. In the ground verification test of the spacecraft simulator, the center of mass of the spacecraft simulator can also be measured by other means to verify the accuracy of the above calculation method, so that the calculation method can be applied to the measurement of the spacecraft when it is in orbit.

[0017] By limiting the degrees of freedom of the center of mass measurement platform, the spacecraft simulator on the center of mass measurement platform will not move under the action of gravity and can maintain a purely ideal rotation, thereby simulating the state of the spacecraft when it is in orbit, thereby improving the accuracy of ground verification experiments.

[0018] In the measurement of the spacecraft simulator, an accelerometer and an attitude measuring instrument are used to measure various parameters of the spacecraft simulator. In order to make the measurement results more accurate and to make the measurement state of the spacecraft simulator close to the state of the spacecraft in orbit, the measurement center of the accelerometer and the center of mass of the spacecraft simulator need to maintain a certain deviation. The embodiment of the present application determines the center of mass position of the spacecraft simulator before entering the torsion pendulum state by the center of mass inertial measuring instrument, which is convenient for installing the accelerometer, so that the measurement center of the accelerometer and the center of mass of the spacecraft simulator maintain a certain deviation. By applying torque excitation to the spacecraft simulator, the spacecraft simulator enters a periodic torsion pendulum motion state. After the spacecraft simulator enters the torsion pendulum state, the center of mass position of the spacecraft simulator is calculated by the parameters measured by the accelerometer and the attitude measuring instrument, and the center of mass of the spacecraft simulator is adjusted to keep the deviation between the center of mass of the spacecraft simulator and the measurement center of the accelerometer within a certain range, ensuring that when the accelerometer is measured, the rotation center of the spacecraft simulator is equivalent to the center of mass of the spacecraft when it is in orbit.

[0019] The embodiment of the present application simulates the state of the spacecraft when it is in orbit through a center of mass measurement platform and a spacecraft simulator, and conducts ground verification experiments of center of mass measurement and center of mass adjustment, thereby verifying the accuracy of the measurement method, and then being able to apply the measurement method to actual on-orbit measurements of spacecraft, thereby improving research efficiency and reducing research costs.

[0020] According to some embodiments of the present application, repeated experiments are performed according to the above steps, and based on the results of the repeated experiments, the error between the center of mass measurement of the spacecraft simulator and the ideal value is calculated to ensure the accuracy of the ground experiment.

[0021] According to some embodiments of the present application, the center of mass measurement platform includes a torsion pendulum base and a torsion pendulum platform, and the center of mass position measurement formula of the spacecraft simulator is:

[0022]

[0023] Where δ is the displacement of the center of mass of the spacecraft simulator; k is the torsional stiffness coefficient of the torsion pendulum platform; m0 is the mass of the spacecraft simulator; m p is the mass of the torsion pendulum platform; ω1 and ω2 are the vibration frequencies of the spacecraft simulator when it rotates 0° and 180° around the rotation axis of the torsion pendulum platform, respectively; is the angle between the horizontal projection of the spacecraft simulator and the vertical line of the spacecraft simulator; R is the distance between the geometric center of the spacecraft simulator and the rotation axis of the torsion pendulum platform.

[0024] According to some embodiments of the present application, a method for calculating an error includes:

[0025] Obtaining the angular velocity and angular acceleration of the spacecraft simulator and the attitude information of the spacecraft simulator;

[0026] Set the Asum matrix, ω matrix and dω matrix. The Asum matrix contains the three-dimensional coordinates (x, y, z) of the spacecraft. The ω matrix is ​​the classification of the angular velocity of the spacecraft simulator in the three directions of x, y, and z (ω x ,ω y ,ω z );The dω matrix is ​​the classification of the angular acceleration of the spacecraft simulator in the three directions of x, y, and z (dω x ,dω y ,dω z );

[0027] In ω z , dω z , x, y, add noise, and set the data after adding noise to ω z’ , dω z’ , x', y'

[0028] Suppose there is a 2×2 matrix A and a 2×1 matrix a, where:

[0029]

[0030] a=[x,y]

[0031] Calculate the deviation in the x direction and the deviation in the y direction of the spacecraft simulator. The calculation formula is as follows:

[0032] l=(A×A) -1 ×A×a

[0033] error = l - [0.005; 0.005]

[0034] Among them, the first column of matrix l is the deviation of the spacecraft simulator in the x direction, and the second column of matrix l is the deviation of the spacecraft simulator in the y direction; the result is a 2×1 matrix error matrix, which is the error between the current estimated parameter and the expected value [0.005; 0.005]. The first column of the error matrix is ​​the error in the x direction, set to x error , the second column of the error matrix is ​​the error in the y direction, set to y error .

[0035] Let the error in the x direction be x error , let the error in the y direction be y error ;

[0036] Repeat the experiment and record the error each time; let the error in the x direction and the error in the y direction of the ith experiment be x and error (i) and yerror (i) Calculate the sum of the squares of the errors in the X and Y directions and find the root mean square (RMS) error X error and Y error ;in

[0037]

[0038] Combining the root mean square error in the X direction and the Y direction, the comprehensive error is calculated. The calculation formula is as follows:

[0039]

[0040] L error This is the desired comprehensive error.

[0041] According to the second aspect of the present application, a ground verification device for on-orbit identification technology of a spacecraft mass center includes:

[0042] A mass center measurement platform, the mass center measurement platform comprises a torsion pendulum platform, a torsion pendulum base and a suspension wire, the torsion pendulum platform is used to place a spacecraft simulator, the torsion pendulum platform is arranged above the torsion pendulum base, the torsion pendulum platform and the torsion pendulum base are connected by the suspension wire, and only the degree of freedom of rotation around the direction of gravity is retained between the torsion pendulum platform and the torsion pendulum base;

[0043] A driving mechanism, disposed on the mass center measurement platform, for applying torque excitation to the spacecraft simulator;

[0044] an accelerometer, the accelerometer being disposed above the center of mass measurement platform and being used to measure the acceleration of the spacecraft simulator;

[0045] The center of mass adjustment mechanism is arranged on the center of mass measurement platform and is used for adjusting the center of mass position of the spacecraft simulator.

[0046] The ground verification device for on-orbit identification technology of spacecraft mass center according to the embodiment of the present application has at least the following beneficial effects:

[0047] By setting up a center of mass measurement platform, the center of mass position of the spacecraft simulator can be measured. The center of mass measurement platform consists of a torsion pendulum platform, a torsion pendulum base and a suspension wire. The torsion pendulum platform and the torsion pendulum base are connected by the suspension wire, so that the torsion pendulum platform can perform torsion pendulum motion on the torsion pendulum base, and the torsion pendulum achieved by the suspension wire is less affected by external forces, has higher motion sensitivity, and can more accurately simulate the state of the spacecraft in orbit. Only the degree of freedom of rotation around the direction of gravity is retained between the torsion pendulum platform and the torsion pendulum base, so that the spacecraft simulator on the torsion pendulum platform will not swing up and down under the influence of gravity, and can maintain a purely ideal rotation, better simulating the motion state of the spacecraft in orbit, so as to conduct more accurate ground verification tests.

[0048] Placing the tumbler platform above the tumbler base so that there is no shielding structure above the tumbler platform means that the size of the spacecraft simulator will not affect the overall installation, allowing flexibility in the use of thinner suspension wires to improve the accuracy and sensitivity of the system.

[0049] A driving mechanism is set up to apply torque excitation to the spacecraft simulator, so that the spacecraft simulator enters a torsion pendulum state, which is convenient for subsequent measurement and adjustment. An accelerometer is set up to collect various motion parameters of the spacecraft simulator during movement, so as to calculate the center of mass position of the spacecraft simulator during movement. By setting up a center of mass adjustment mechanism, the center of mass of the spacecraft simulator can be adjusted according to the center of mass position of the spacecraft simulator, so that the center of mass of the spacecraft simulator and the measurement center of the accelerometer maintain a certain deviation.

[0050] According to some embodiments of the present application, the suspension wire includes a first suspension wire, a second suspension wire, a third suspension wire, a fourth suspension wire and a fifth suspension wire. The setting direction of the first suspension wire is parallel to the direction of gravity. The second suspension wire intersects with the third suspension wire at a first intersection. The fourth suspension wire intersects with the fifth suspension wire at a second intersection. The first intersection and the second intersection are both set on the torsion pendulum platform.

[0051] According to some embodiments of the present application, the driving mechanism is a reaction flywheel.

[0052] According to some embodiments of the present application, the center of mass adjustment mechanism includes a movable rail, a mass block and a driving unit, the movable rail is installed on the spacecraft simulator, the mass block is movably set on the movable rail, and the driving unit is used to drive the mass block to move.

[0053] According to some embodiments of the present application, the oscillating platform includes a connecting portion, the connecting portion has a bending portion, the bending portion is arranged at the bottom of the oscillating base, a support line is arranged on the bending portion, the support line is connected to the oscillating base, and the direction in which the support line is arranged is parallel to the direction of gravity.

[0054] According to some embodiments of the present application, a moving mechanism is connected to the accelerometer, and the moving mechanism is used to move the position of the accelerometer.

[0055] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The accompanying drawings are used to provide further understanding of the technical solution disclosed in the present application and constitute a part of the specification. Together with the embodiments disclosed in the present application, they are used to explain the technical solution disclosed in the present application and do not constitute a limitation on the technical solution disclosed in the present application.

[0057] Figure 1 This is a flow chart of a ground verification method for the on-orbit identification technology of the spacecraft mass center according to an embodiment of the present application;

[0058] Figure 2 This is a schematic diagram of the overall structure of a ground verification device for the on-orbit identification technology of the center of mass of a spacecraft according to an embodiment of the present application;

[0059] Figure 3 This is a schematic diagram of the structure of the center of mass measurement platform of the ground verification device of the spacecraft center of mass in-orbit identification technology in the embodiment of the present application.

[0060] Figure numerals: center of mass measurement platform 110, driving mechanism 120, accelerometer 130, moving mechanism 131, first moving component 132, second moving component 133, center of mass adjustment mechanism 140, moving rail 141, mass block 142, torsion pendulum platform 150, connecting portion 151, bending portion 152, torsion pendulum base 160, first suspension wire 171, second suspension wire 172, third suspension wire 173, fourth suspension wire 174, fifth suspension wire 175, support line 176, attitude measuring instrument 180, data acquisition card 181, power supply 190. DETAILED DESCRIPTION

[0061] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0062] In the description of the present application, it should be understood that descriptions involving orientation, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0063] In the description of this application, "several" means more than one, "more" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and "above", "below", "within", etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0064] In the description of this application, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in this application based on the specific content of the technical solution.

[0065] In the description of the present application, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0066] In some selectable embodiments, the function / operation mentioned in the block diagram may not occur in the order mentioned in the operation diagram. For example, depending on the function / operation involved, the two boxes shown in succession can actually be executed substantially simultaneously or the boxes can sometimes be executed in reverse order. In addition, the embodiment presented and described in the flow chart of the application is provided by way of example, for the purpose of providing a more comprehensive understanding of technology. The disclosed method is not limited to the operation and logic flow presented herein. Selectable embodiments are expected, wherein the order of various operations is changed and the sub-operation of a part described as a larger operation is performed independently.

[0067] For the ground verification method of the spacecraft center of mass identification technology on orbit according to the first aspect of the present application, please refer to Figure 1 to Figure 3 , which comprises the following steps:

[0068] S1: Setting the centroid measurement platform 110, limiting the degree of freedom of the centroid measurement platform 110, so that the centroid measurement platform 110 only retains the degree of freedom of rotation around the gravity direction;

[0069] S2: placing the spacecraft simulator on the mass center measurement platform 110, and using the mass center inertia measuring instrument to measure the mass center position of the spacecraft simulator. The mass center measurement platform 110 is provided with an accelerometer 130 and an attitude measuring instrument 180. The accelerometer 130 has a measurement center, and the position of the measurement center has a deviation from the mass center position of the spacecraft simulator;

[0070] S3: applying torque excitation to the spacecraft simulator, so that the spacecraft simulator generates periodic swing on the center of mass measurement platform 110;

[0071] S4: using the attitude measuring instrument 180 to measure the attitude of the swinging spacecraft simulator, and using the accelerometer 130 to measure the linear acceleration of the spacecraft simulator at the center of the accelerometer 130;

[0072] S5: Calculate the center of mass position of the spacecraft simulator at this time by measuring the attitude and acceleration of the spacecraft simulator;

[0073] S6: According to the calculated center of mass position, the center of mass position of the spacecraft simulator is adjusted to control the deviation between the center of mass of the spacecraft simulator and the center of the accelerometer 130.

[0074] In an embodiment of the present application, a center of mass measurement platform 110 is provided and a spacecraft simulator is placed on the center of mass measurement platform 110. The spacecraft simulator can perform a torsional pendulum motion on the center of mass measurement platform 110. Various parameters of the spacecraft during the torsion and pendulum are measured and the center of mass position of the spacecraft simulator can be calculated through the measured parameters. In a ground verification test of the spacecraft simulator, the center of mass of the spacecraft simulator can also be measured by other means to verify the accuracy of the above-mentioned calculation method, so that the calculation method can be applied to the measurement of the spacecraft while it is in orbit.

[0075] By limiting the degrees of freedom of the center of mass measurement platform 110, the spacecraft simulator on the center of mass measurement platform 110 will not move under the action of gravity and can maintain a purely ideal rotation, thereby simulating the state of the spacecraft when it is in orbit, thereby improving the accuracy of ground verification experiments.

[0076] In the measurement of the spacecraft simulator, the accelerometer 130 and the attitude measuring instrument 180 are used to measure various parameters of the spacecraft simulator. In order to make the measurement results more accurate and to make the measurement state of the spacecraft simulator close to the state of the spacecraft on orbit, the measurement center of the accelerometer 130 and the center of mass of the spacecraft simulator need to maintain a certain deviation. The embodiment of the present application determines the center of mass position of the spacecraft simulator before entering the torsion pendulum state by the center of mass inertial measuring instrument, which is convenient for installing the accelerometer 130, so that the measurement center of the accelerometer 130 and the center of mass of the spacecraft simulator maintain a certain deviation. By applying torque excitation to the spacecraft simulator, the spacecraft simulator enters a periodic torsion pendulum motion state. After the spacecraft simulator enters the torsion pendulum state, the center of mass position of the spacecraft simulator is calculated by the parameters measured by the accelerometer 130 and the attitude measuring instrument 180, and the center of mass of the spacecraft simulator is adjusted to keep the deviation between the center of mass of the spacecraft simulator and the measurement center of the accelerometer within a certain range.

[0077] The deviation between the position of the measurement center and the position of the center of mass of the spacecraft simulator is intended to solve the following problems: if the spacecraft is required to perform only attitude movement when it is in orbit, the reference point of rotation is at the center of mass of the spacecraft, and the center of mass position is regarded as (0,0,0). The accelerometer 130 has a certain installation distance from it, and the position of the center of mass can be determined by the distance between the two; while during ground verification, the spacecraft is verified on the center of mass measurement platform 110, and the center of rotation at this time is not the center of mass of the spacecraft but the center of rotation of the torsion pendulum platform 150. In order to ensure that the center of rotation of the spacecraft simulator is equivalent to the center of mass of the spacecraft when it is in orbit, the offset between the accelerometer 130 and the center of mass of the spacecraft simulator is adjusted by adjusting the center of mass position of the spacecraft simulator, thereby simulating the offset between the center of mass of the spacecraft and the accelerometer 130 when the spacecraft is in orbit.

[0078] Specifically, in the embodiment of the present application, the center of mass measurement platform 110 includes a wobbling platform 150, a wobbling base 160 and a suspension wire. The wobbling platform 150 is used to place a spacecraft simulator. The wobbling platform 150 is arranged above the wobbling base 160. The wobbling platform 150 and the wobbling base 160 are connected by the suspension wire. Only the degree of freedom of rotation around the direction of gravity is retained between the wobbling platform 150 and the wobbling base 160. Specifically, the suspension wire includes a first suspension wire 171, a second suspension wire 172, a third suspension wire 173, a fourth suspension wire 174 and a fifth suspension wire 175. The setting direction of the first suspension wire 171 is parallel to the direction of gravity. The second suspension wire 172 and the third suspension wire 173 intersect at a first intersection. The fourth suspension wire 174 and the fifth suspension wire 175 intersect at a second intersection. The first intersection and the second intersection are both arranged on the wobbling platform 150, and the connection point between the first suspension wire 171 and the wobbling platform 150 is the third intersection. By setting five suspension wires, the torsion pendulum base 160 and the torsion pendulum platform 150 form a five-wire torsion pendulum structure, thereby limiting the degree of freedom of the torsion pendulum platform 150 so that the torsion pendulum platform 150 can only rotate around the direction of gravity. When the torsion pendulum platform 150 is acted upon by an external force (such as gravity) and has a tendency to move in other directions, there is always one or more suspension wires that can generate a pulling force that offsets the external force, thereby limiting the degree of freedom of the torsion pendulum platform 150.

[0079] Specifically, the distance from the first intersection to the rotation center of the yaw platform 150 , the distance from the second intersection to the rotation center of the yaw platform 150 , and the distance from the third intersection to the rotation center of the yaw platform 150 are equal.

[0080] Specifically, in the embodiment of the present application, the measurement formula of the center of mass position of the spacecraft simulator is:

[0081]

[0082] Where δ is the offset of the center of mass of the spacecraft simulator; k is the torsional stiffness coefficient of the torsion pendulum platform; m0 is the mass of the spacecraft simulator; m p is the mass of the tumble platform; ω1 and ω2 are the vibration frequencies of the spacecraft simulator when it rotates 0° and 180° around the rotation axis of the tumble platform, respectively; is the angle between the horizontal projection of the spacecraft simulator and the vertical line of the spacecraft simulator; R is the distance between the geometric center of the spacecraft simulator and the rotation axis of the torsion pendulum platform.

[0083] Specifically, the horizontal projection of the spacecraft simulator is the horizontal projection of the center of mass of the spacecraft to be tested, and the vertical line is the vertical line between the center of mass of the spacecraft to be tested and the central axis of rotation of the torsion pendulum platform. There are many ways to obtain the vibration frequency of the spacecraft simulator. In this embodiment, the vibration frequency can be extracted from the time series of the angular displacement of the spacecraft simulator, or it can be directly measured by an instrument, which will not be repeated here.

[0084] Specifically, the calculation formula of the torsional stiffness coefficient k of the torsion pendulum platform is as follows:

[0085]

[0086] Where k is the torsional stiffness coefficient of the torsion pendulum platform, r is the distance from the rotation center to the wire connection point, g is the gravitational acceleration, and L is the wire length.

[0087] The embodiment of the present application simulates the state of the spacecraft when it is in orbit through the center of mass measurement platform 110 and the spacecraft simulator, and conducts ground verification experiments on the center of mass identification and center of mass adjustment, so as to verify the accuracy of the identification and adjustment methods, and then the identification and adjustment methods can be applied to the actual on-orbit measurement of the spacecraft, thereby improving research efficiency and reducing research costs.

[0088] It should be noted that the spacecraft simulator should be installed on the torsion pendulum platform 150 to carry out ground simulation experiments for calibration and adjustment of the spacecraft center of mass. In the initial state, the center of mass of the spacecraft simulator should be placed at the position of the rotation center of the torsion pendulum.

[0089] Specifically, in an embodiment of the present application, the method for adjusting the center of mass of the spacecraft simulator is to set a center of mass adjustment mechanism 140, and the center of mass adjustment mechanism 140 is installed on the spacecraft simulator. The center of mass adjustment mechanism 140 includes a movable rail 141, a mass block 142 and a driving unit. The driving unit drives the mass block 142 to move on the movable rail 141, thereby changing the mass distribution of the spacecraft simulation, thereby changing the center of mass position of the spacecraft simulator.

[0090] According to some embodiments of the present application, experiments are repeated according to the above steps, and based on the results of multiple experiments, the error between the center of mass measurement of the spacecraft simulator and the ideal value is calculated to ensure the accuracy of the ground verification experiment.

[0091] According to some embodiments of the present application, a method for calculating an error includes:

[0092] S1': obtain the angular velocity and angular acceleration of the spacecraft simulator and the attitude information of the spacecraft simulator;

[0093] S2': Set the Asum matrix, ω matrix and dω matrix. The Asum matrix contains the three-dimensional coordinates (x, y, z) of the spacecraft. The ω matrix is ​​the classification of the angular velocity of the spacecraft simulator in the three directions of x, y, and z (ω x ,ω y ,ω z );dω matrix is ​​the classification of the angular acceleration of the spacecraft simulator in the three directions of x, y, and z (dω x ,dω y ,dω z );

[0094] S3': in ω z dω z , x, y, add noise, and set the data after adding noise to ω z’ , dω z’ , x', y'

[0095] S4': Assume a 2×2 matrix A and a 2×1 matrix a, where:

[0096]

[0097] a=[x,y]

[0098] S5': Calculate the deviation in the x direction and the deviation in the y direction of the spacecraft simulator. The calculation formula is as follows:

[0099] l=(A×A) -1 ×A×a

[0100] error = l - [0.005; 0.005]

[0101] Among them, the first column of matrix l is the deviation of the spacecraft simulator in the x direction, and the second column of matrix l is the deviation of the spacecraft simulator in the y direction; the result is a 2×1 matrix error matrix, which is the error between the current estimated parameter and the expected value [0.005; 0.005]. The first column of the error matrix is ​​the error in the x direction, set to x error , the second column of the error matrix is ​​the error in the y direction, set to y error .

[0102] S6': Let the error in the x direction be x error , let the error in the y direction be y error ;

[0103] Repeat the experiment and record the error each time. Suppose the error in the x direction and the error in the y direction of the ith experiment are x and error (i) and y error (i) Calculate the sum of the squares of the errors in the X and Y directions and find the root mean square (RMS) error X error and Y error ;in

[0104]

[0105] S7': Combine the root mean square errors in the X and Y directions to calculate the comprehensive error. The calculation formula is as follows:

[0106]

[0107] L error This is the desired comprehensive error.

[0108] Through the comprehensive error L error , which can provide a reference for subsequent decision-making, help us judge the accuracy of the center of mass estimation, complete the ground verification of the spacecraft's on-orbit identification technology, and then apply the center of mass identification technology to the on-orbit measurement of the spacecraft.

[0109] This application also discloses a ground verification device for on-orbit identification of the center of mass of a spacecraft. Figure 2 , 3 , which includes a mass center measurement platform 110, a driving mechanism 120, an accelerometer 130 and a mass center adjustment mechanism 140. The mass center measurement platform 110 includes a torsion pendulum platform 150, a torsion pendulum base 160 and a suspension wire. The torsion pendulum platform 150 is used to place a spacecraft simulator (the spacecraft simulator is not shown in the figure). The torsion pendulum platform 150 is arranged above the torsion pendulum base 160. The torsion pendulum platform 150 and the torsion pendulum base 160 are connected by the suspension wire. Only the degree of freedom of rotation around the direction of gravity is retained between the torsion pendulum platform 150 and the torsion pendulum base 160;

[0110] A driving mechanism 120 , disposed on the mass center measurement platform 110 , for applying torque excitation to the spacecraft simulator;

[0111] An accelerometer 130 , which is disposed on the mass center measurement platform 110 and is used to measure the acceleration of the spacecraft simulator;

[0112] The center of mass adjustment mechanism 140 is disposed on the center of mass measurement platform 110 and is used to adjust the center of mass position of the spacecraft simulator.

[0113] By setting up a center of mass measurement platform 110, the center of mass position of the spacecraft simulator can be measured. The center of mass measurement platform 110 is composed of a wobbling platform 150, a wobbling base 160 and a suspension wire. The wobbling platform 150 and the wobbling base 160 are connected by the suspension wire, so that the wobbling platform 150 can perform a wobbling motion on the wobbling base 160, and the wobbling achieved by the suspension wire is less affected by external forces, has a higher motion sensitivity, and can more accurately simulate the state of the spacecraft in orbit. Only the degree of freedom of rotation around the direction of gravity is retained between the wobbling platform 150 and the wobbling base 160, so that the spacecraft simulator will not swing up and down or the like under the influence of gravity on the wobbling platform 150, and can maintain a purely ideal rotation, so as to better simulate the motion state of the spacecraft in orbit, so as to conduct more accurate ground verification tests.

[0114] The tumbler platform 150 is disposed above the tumbler base 160 so that there is no shielding structure above the tumbler platform 150, which means that the size of the spacecraft simulator will not affect the overall installation, thereby allowing the flexibility to select thinner suspension wires to improve the accuracy and sensitivity of the system.

[0115] A driving mechanism 120 is provided to apply torque excitation to the spacecraft simulator, so that the spacecraft simulator enters a torsion pendulum state, which is convenient for subsequent measurement and adjustment. An accelerometer 130 is provided to collect various motion parameters of the spacecraft simulator during movement, so as to calculate the center of mass position of the spacecraft simulator during movement. By providing a center of mass adjustment mechanism 140, the center of mass of the spacecraft simulator can be adjusted according to the center of mass position of the spacecraft simulator, so that the center of mass of the spacecraft simulator and the measurement center of the accelerometer 130 maintain a certain deviation.

[0116] Preferably, the accelerometer is a high-precision quartz flexible accelerometer installed on the moving mechanism to measure the linear acceleration of the accelerometer measurement center when the spacecraft simulator performs periodic attitude motion.

[0117] In the embodiment of the present application, a posture measuring instrument 180 is also provided on the centroid measurement platform 110. Specifically, the posture measuring instrument 180 used in the embodiment of the present application is an autocollimator with high measurement accuracy and fast measurement speed.

[0118] The autocollimator in the embodiment of the present application can measure the attitude with an accuracy better than 5 μrad; the accelerometer can measure the attitude with an accuracy better than 10 μrad. -6 m / s 2 .

[0119] According to some embodiments of the present application, the suspension wire includes a first suspension wire 171, a second suspension wire 172, a third suspension wire 173, a fourth suspension wire 174 and a fifth suspension wire 175. The setting direction of the first suspension wire 171 is parallel to the direction of gravity. The second suspension wire 172 and the third suspension wire 173 intersect at a first intersection. The fourth suspension wire 174 and the fifth suspension wire 175 intersect at a second intersection. The first intersection and the second intersection are both set on the torsion pendulum platform 150.

[0120] Specifically, the second suspension wire 172 and the third suspension wire 173 constitute a first pulling structure, the fourth suspension wire 174 and the fifth suspension wire 175 constitute a second pulling structure, and the first pulling structure and the second pulling structure are symmetrical to each other, and the center of symmetry is the plane formed by the rotation axis of the torsion pendulum platform 150 and the line where the first suspension wire 171 is located. This structure enables the suspension wires deployed by each pulling structure to provide effective horizontal rigidity, thereby preventing the torsion pendulum plane from swinging, maintaining the rotational motion, and maintaining the stability of the center of mass measurement platform 110.

[0121] Working principle: When not restricted, the spacecraft simulator has three rotation angles. The five-wire torsion pendulum structure formed by the five suspension wires restricts two rotational degrees of freedom and three translational degrees of freedom, so that the spacecraft simulator to be tested has only the degree of freedom around the vertical direction, thereby achieving pure ideal rotation at a small angle. In addition, the torsion pendulum platform 150 with the five-wire torsion pendulum structure has high flexibility and controllability. It can be adjusted and optimized according to specific needs to meet the rotation requirements of different spacecraft simulators.

[0122] Specifically, in one embodiment of the present application, the suspension wire is made of quartz wire with high elastic modulus and low thermal expansion coefficient to ensure stable performance under different environmental conditions.

[0123] Specifically, in some other embodiments of the present application, the suspension wires may also be made of metal wires or suspension wires made of other materials.

[0124] In modern aerospace technology, precise rotation control is very important. Existing technologies use single-axis turntables and single-axis air-floating tables to achieve rotation. However, with the continuous development of technology, these solutions can no longer fully meet the needs of precise rotation control.

[0125] The single-axis turntable is one of the early rotation schemes used. It controls the rotation of the spacecraft through an independent axis. However, the single-axis turntable has the problem of friction. Since the contact surface between the bearings will produce friction during the rotation process, it will have a negative impact on the smoothness and accuracy of the rotation. Especially at small angles, the friction will be more obvious, causing rotation instability.

[0126] On the other hand, the single-axis air-floating table uses air film support to achieve rotation. By forming an air film on the bearing, the contact area with the bearing can be reduced, thereby reducing the impact of friction. However, the single-axis air-floating table also has problems with air pressure fluctuations and air film unevenness. The fluctuation of air pressure will affect the support effect of the air film, resulting in instability of rotation.

[0127] In contrast, the centroid measurement platform 110 of the embodiment of the present application adopts a five-wire torsion pendulum platform, which adopts a completely different working principle. It limits the degrees of freedom in five directions so that the spacecraft simulator to be tested only retains the degrees of freedom around the vertical direction. In this way, within a small angle range, the rotation process is more stable, and accurate measurement and control can be achieved. At very small angles, the five-wire torsion pendulum platform can provide pure ideal rotation.

[0128] According to some embodiments of the present application, the driving mechanism 120 is a reaction flywheel. The reaction flywheel can use the change in its own angular momentum to apply torque excitation to the spacecraft under test through the law of conservation of momentum. This driving method has high stability and high response speed, and can quickly and accurately perform torque excitation on the spacecraft under test in the experiment.

[0129] According to some embodiments of the present application, the mass center adjustment mechanism 140 includes a moving rail 141, a mass block 142, and a driving unit (not shown in the figure), wherein the moving rail 141 is installed on the spacecraft simulator, the mass block 142 is movably arranged on the moving rail 141, and the driving unit is used to drive the mass block 142 to move. By changing the position of the mass block 142, the mass distribution on the spacecraft simulator can be changed, thereby adjusting the mass center position of the spacecraft simulator.

[0130] In the embodiment of the present application, a plurality of center of mass adjustment mechanisms 140 may be provided.

[0131] Preferably, according to some embodiments of the present application, two center of mass adjustment mechanisms 140 are provided, and the mass blocks of the two center of mass adjustment mechanisms 140 are orthogonal in the moving direction, so as to be able to adjust the center of mass position of the spacecraft simulator in two directions.

[0132] According to some embodiments of the present application, the oscillating platform 150 includes a connecting portion 151, the connecting portion 151 has a bending portion 152, the bending portion 152 is arranged at the bottom of the oscillating base 160, and a support line 176 is arranged on the bending portion 152. The support line 176 is connected to the oscillating base 160, and the direction in which the support line 176 is arranged is parallel to the direction of gravity.

[0133] The embodiment of the present application forms a tensile structure that can effectively balance the tension by setting the support wire 176 and combining it with the five-wire torsion pendulum structure formed by the five suspension wires, thereby further enhancing the balance of the overall structure. In addition, the support wire 176 can maintain the stability of the entire structure by connecting with the other five suspension wires, ensuring reliability and durability during operation.

[0134] When gravity is in line with the support wire 176, the tensegrity structure is best balanced and the stability of the structure can be maintained through the connection of the five suspension wires.

[0135] The embodiment of the present application utilizes the prestress of the suspension wire and the support wire 176 to maintain the shape and stability of the structure. When subjected to external forces, the suspension wire and the support wire 176 can reduce the pressure of the external forces on a single point in the structure by absorbing the external forces and evenly distributing these forces. This design effectively isolates external vibrations and reduces the impact on the structure. The natural vibration frequency of the tensioned structure is usually low, which meets the requirements of ground verification. This structure not only enhances stability, but also improves seismic performance.

[0136] According to some embodiments of the present application, the accelerometer 130 is connected to a data acquisition card, and the data acquisition card is used to collect output parameters of the accelerometer 130 to facilitate subsequent calculations.

[0137] According to some embodiments of the present application, a moving mechanism 131 is connected to the accelerometer 130, and the moving mechanism 131 is used to move the position of the accelerometer 130. By setting the moving mechanism 131, the position of the accelerometer 130 can be adjusted, thereby adjusting the deviation between the measurement center of the accelerometer 130 and the center of mass of the spacecraft simulator. The moving mechanism 131 includes a first moving component 132 and a second moving component 133. The accelerometer 130 is connected to the first moving component 132, and the first moving component 132 can drive the accelerometer 130 to move. The first moving component 132 is connected to the second moving component 133, and the second moving component 133 can drive the first moving component 132 to move. By setting the first moving component 132 and the second moving component 133, the accelerometer 130 can achieve movement in two directions.

[0138] The deviation between the center of mass of the spacecraft simulator and the measurement center of the accelerometer 130 is generated by the moving mechanism 131, and the spacecraft simulator on the five-wire torsion pendulum platform is driven to generate periodic attitude drive through the driving mechanism (reaction flywheel). The accelerometer generates the linear acceleration of the accelerometer measurement center, which is collected and transmitted to the host computer through the data acquisition card 181. The distance between the center of mass of the accelerometer and the center of mass of the spacecraft simulator is calibrated by the center of mass calibration algorithm, and then the motion command is input into the center of mass adjustment mechanism according to the calibration result to adjust the center of mass of the spacecraft simulator and control the deviation between the center of mass of the spacecraft simulator and the center of the accelerometer within a certain range.

[0139] The ground verification device for the on-orbit identification technology of the spacecraft center of mass in the embodiment of the present application is also provided with a power supply 190 for providing the energy required for the operation of the system.

[0140] The embodiments of the present application are described in detail above in conjunction with the accompanying drawings, but the present application is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present application. In addition, the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

Claims

1. A ground verification method for on-orbit identification of spacecraft mass center, characterized in that: The following steps are involved: Setting a centroid measurement platform, limiting the degree of freedom of the centroid measurement platform, so that the centroid measurement platform only retains the degree of freedom of rotation around the direction of gravity; Placing a spacecraft simulator on the mass center measurement platform, and using a mass center inertia measuring instrument to measure the mass center position of the spacecraft simulator, an accelerometer and an attitude measuring instrument are arranged above the mass center measurement platform, the accelerometer has a measurement center, and the mass center position of the spacecraft simulator is offset from the position of the measurement center; Applying torque excitation to the spacecraft simulator to cause the spacecraft simulator to generate periodic oscillations on the center of mass measurement platform; Using the attitude measuring instrument to measure the attitude of the swinging spacecraft simulator, and using the accelerometer to measure the linear acceleration of the spacecraft simulator at the center of the accelerometer; By measuring the attitude and acceleration of the spacecraft simulator, the center of mass position of the spacecraft simulator at this time is calculated; According to the calculated center of mass position, the center of mass position of the spacecraft simulator is adjusted to control the distance between the center of mass of the spacecraft simulator and the center of the accelerometer.

2. The ground verification method for on-orbit identification of spacecraft mass center according to claim 1 is characterized in that: The center of mass measurement platform includes a torsion pendulum base and a torsion pendulum platform. The center of mass position measurement formula of the spacecraft simulator is: Where δ is the displacement of the center of mass of the spacecraft simulator; k is the torsional stiffness coefficient of the torsion pendulum platform; m0 is the mass of the spacecraft simulator; m p is the mass of the torsion pendulum platform; ω1 and ω2 are the vibration frequencies of the spacecraft simulator when it rotates 0° and 180° around the rotation axis of the torsion pendulum platform, respectively; is the angle between the horizontal projection of the spacecraft simulator and the vertical line of the spacecraft simulator; R is the distance between the geometric center of the spacecraft simulator and the rotation axis of the torsion pendulum platform.

3. The ground verification method for on-orbit identification of spacecraft mass center according to claim 1 is characterized in that: Repeat the experiment and calculate the error between the center of mass measurement of the spacecraft simulator and the ideal value based on the results of the repeated experiments to ensure the accuracy of the ground verification experiment.

4. The ground verification method for on-orbit identification of spacecraft mass center according to claim 3 is characterized in that: Methods for calculating the error include: Get the angular velocity and angular acceleration of the spacecraft simulator, Set the Asum matrix, ω matrix and dω matrix. The Asum matrix contains the three-dimensional coordinates (x, y, z) of the spacecraft. The ω matrix is ​​the classification of the angular velocity of the spacecraft simulator in the three directions of x, y, and z (ω x ,ω y ,ω z );The dω matrix is ​​the classification of the angular acceleration of the spacecraft simulator in the three directions of x, y, and z (dω x ,dω y ,dω z ); In ω z dω z , x, y, add noise, and set the data after adding noise to ω z' , dω z' , x', y' Suppose there is a 2×2 matrix A and a 2×1 matrix a, where: a=[x,y] Calculate the deviation in the x-direction and the y-direction of the spacecraft simulator. The calculation formula is as follows: l=(A×A) -1 ×A×a error = l - [0.005; 0.005] Among them, the first column of matrix l is the deviation of the spacecraft simulator in the x direction, and the second column of matrix l is the deviation of the spacecraft simulator in the y direction; the result is a 2×1 matrix error matrix, which is the error between the current estimated parameter and the expected value [0.005; 0.005]. The first column of the error matrix is ​​the error in the x direction, set to x error , the second column of the error matrix is ​​the error in the y direction, set to y error . Let the error in the x direction be x error , let the error in the y direction be y error ; Repeat the experiment and record the error each time; let the error in the x direction and the error in the y direction of the ith experiment be x and error (i) and y error (i) Calculate the sum of the squares of the errors in the X and Y directions and find the root mean square (RMS) error X error and Y error ;in Combining the root mean square error in the X direction and the Y direction, the comprehensive error is calculated. The calculation formula is as follows: L error This is the desired comprehensive error.

5. A ground verification device for on-orbit identification technology of spacecraft mass center, characterized in that: The ground verification method for implementing the on-orbit identification technology of the spacecraft mass center described in claim 1 comprises: A mass center measurement platform, the mass center measurement platform comprises a torsion pendulum platform, a torsion pendulum base and a suspension wire, the torsion pendulum platform is used to place a spacecraft simulator, the torsion pendulum platform is arranged above the torsion pendulum base, the torsion pendulum platform and the torsion pendulum base are connected by the suspension wire, and only the degree of freedom of rotation around the direction of gravity is retained between the torsion pendulum platform and the torsion pendulum base; A driving mechanism, disposed on the mass center measurement platform, for applying torque excitation to the spacecraft simulator; an accelerometer, the accelerometer being disposed above the center of mass measurement platform and being used to measure the acceleration of the spacecraft simulator; The center of mass adjustment mechanism is arranged on the center of mass measurement platform and is used for adjusting the center of mass position of the spacecraft simulator.

6. The ground verification device for on-orbit identification of spacecraft mass center according to claim 5 is characterized in that: The suspension wire includes a first suspension wire, a second suspension wire, a third suspension wire, a fourth suspension wire and a fifth suspension wire. The setting direction of the first suspension wire is parallel to the direction of gravity. The second suspension wire intersects with the third suspension wire at a first intersection. The fourth suspension wire intersects with the fifth suspension wire at a second intersection. The first intersection and the second intersection are both set on the torsion pendulum platform.

7. The ground verification device for on-orbit identification of spacecraft mass center according to claim 5 is characterized in that: The driving mechanism is a reaction flywheel.

8. The ground verification device for on-orbit identification of spacecraft mass center according to claim 5 is characterized in that: The mass center adjustment mechanism comprises a moving rail, a mass block and a driving unit. The moving rail is installed on the spacecraft simulator, the mass block is movably arranged on the moving rail, and the driving unit is used to drive the mass block to move.

9. The ground verification device for on-orbit identification of spacecraft mass center according to claim 5, characterized in that: The oscillating platform comprises a connecting portion, wherein the connecting portion has a bending portion, wherein the bending portion is arranged at the bottom of the oscillating base, wherein a support line is arranged on the bending portion, wherein the support line is connected to the oscillating base, and wherein the direction in which the support line is arranged is parallel to the direction of gravity.

10. The ground verification device for on-orbit identification of spacecraft mass center according to claim 5, characterized in that: The accelerometer is connected with a moving mechanism, and the moving mechanism is used to move the position of the accelerometer.

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