A prediction method to avoid satellite-to-ground data transmission failure

Abstract

The present invention discloses a prediction method for avoiding satellite-to-ground data transmission failures, and analyzes whether the satellite's large-angle attitude maneuvering process will have an adverse effect on the pointing direction of the data transmission antenna, thereby rationally planning the satellite's data transmission mission. The present invention not only determines whether the theoretical rotation angle of the data transmission antenna exceeds the rotation angle range of the data transmission antenna, but also considers whether the maximum rotation angular velocity and angular acceleration are out of range, making the analysis more comprehensive and flexible. The angle change range can be predicted based on the angular acceleration, and the feasibility analysis of the data transmission during the large-angle attitude maneuvering process can be completed. The present invention adopts a polynomial fitting method to obtain the rotation angular velocity and angular acceleration of the data transmission antenna. The obtained angular velocity curve and angular acceleration curve change process are smooth and continuous, avoiding the error amplification problem caused by direct angle differentiation; it has engineering practicality and can provide support for the mission planning of various types of satellites with large-angle maneuvering capabilities.

Description

Technical Field

[0001] The present invention relates to the technical field of satellite data transmission evaluation, and in particular to a prediction method for avoiding satellite-to-ground data transmission failure. Background Art

[0002] To carry out complex missions, modern satellites typically possess the ability to maneuver at large angles. For example, high-resolution Earth observation satellites, to achieve observations of targets over a wide area, are no longer limited to observations near the subsatellite point. Instead, they can utilize their flexible attitude control capabilities to perform complex observation missions such as forward, backward, and oblique observations, significantly improving satellite data acquisition capabilities.

[0003] However, satellite maneuvers at high angles also present new challenges. When a satellite flies over a ground station, its data transmission antenna must be pointed toward the station for the station to properly receive the satellite's downlink signals. If the satellite needs to perform high-angle maneuvers to perform other tasks during data transmission, these maneuvers can adversely affect data transmission. On the one hand, due to the excessively large maneuvers, the ground station may move out of the pointing range of the data transmission antenna, causing data transmission to fail. On the other hand, even if the ground station is within the pointing range of the data transmission antenna, the antenna's limited response capability can also cause data transmission to fail.

[0004] Therefore, there is an urgent need for a method to avoid the failure of data transmission to the ground, so that ground operators can analyze in advance whether the satellite attitude maneuvering process will have an adverse effect on the pointing of the data transmission antenna when planning the mission. Summary of the Invention

[0005] In view of this, the present invention provides a prediction method for avoiding satellite-to-ground data transmission failure, which can analyze whether the satellite attitude maneuvering process will have an adverse effect on the data transmission antenna pointing direction.

[0006] In order to achieve the above-mentioned object of the invention, the technical solution of the present invention is:

[0007] A prediction method for avoiding satellite-to-ground data transmission failure, comprising the following steps:

[0008] Step 1: Based on the satellite's full-process attitude, obtain the projection of the relative vector between the ground station and the satellite in the satellite's own system; multiply the projection by the satellite installation matrix and convert the projection to the antenna coordinate system.

[0009] Step 2: Calculate the rotation angle of the antenna at each moment based on the projection of the relative vector in the antenna coordinate system.

[0010] Step 3: Check whether the rotation angle at each moment exceeds the rotation angle range. If not, proceed to step 4; if exceeded, the evaluation result is data transmission failure.

[0011] Step 4: Fit the rotation angles at all moments into a curve, and obtain the rotation angular velocity and rotation angular acceleration at each moment after derivation.

[0012] Step 5: Determine whether the rotational angular velocity exceeds the rotational angular velocity range, and determine whether the rotational angular acceleration exceeds the rotational angular acceleration range; if both the rotational angular velocity and the rotational angular acceleration are within the range, the evaluation result is that the data transmission is successful, otherwise the data transmission fails.

[0013] Furthermore, the specific method of step 1 is:

[0014] Step 1.1: Based on the satellite's initial orbit, the satellite's full-process attitude, and the ground station's position, perform orbit prediction and obtain the relative vector v between the ground station and the satellite during the satellite's attitude maneuver period. i , i is the time.

[0015] Step 1.2: Set the relative vector v i Coordinates are converted to projections in the satellite's native system (v i ) sat .

[0016] Step 1.3, projection (v i ) sat With satellite installation matrix L ant_sat Multiply and transform the projection into the antenna coordinate system (v i ) ant .

[0017] Furthermore, the specific method of step 2 is: the projection (v i ) ant Written in component form, that is:

[0018] (v i ) ant =(v i_ant_x ,v i_ant_y ,v i_ant_z ) T

[0019] Among them, v i_ant_x for (v i ) ant The X-axis coordinate, v i_ant_y for (v i ) ant The Y-axis coordinate, v i_ant_z for (v i ) ant The Z-axis coordinate of .

[0020] Then the rotation angle α of the data transmission antenna around the +X axis is i for:

[0021] α i =atan(-v i_ant_y / v i_ant_z )

[0022] The rotation angle β of the data transmission antenna around the +Y axis i for:

[0023]

[0024] Furthermore, in step 4, a polynomial fitting method is used to solve the fitting curve.

[0025] Furthermore, the polynomial expression of the fitting curve is:

[0026] α(t)=a0+a1(tt start )+a2(tt start ) 2 +…+a n (tt start ) n

[0027] Among them, t is the time, t∈[t start ,t end ]; n is the polynomial order, i=1,…,n; a i is the coefficient of the polynomial to the i-th power, t start , t end are the start and end times of the attitude maneuver period, respectively.

[0028] Beneficial effects:

[0029] 1. This invention proposes a method for predicting satellite-to-ground data transmission failures. This method analyzes whether a satellite's high-angle attitude maneuvers will adversely affect the data transmission antenna's pointing direction, thereby enabling rational planning of satellite data transmission missions. This method not only determines whether the data transmission antenna's theoretical rotation angle exceeds the data transmission antenna's rotation angle range, but also considers whether the maximum rotational angular velocity and angular acceleration exceed these ranges. This provides a more comprehensive and flexible analysis, predicting the angle variation range based on angular acceleration, and completing data transmission feasibility analysis during high-angle attitude maneuvers.

[0030] 2. The present invention adopts a polynomial fitting method to obtain the angular velocity and angular acceleration of the digital transmission antenna. The obtained angular velocity curve and angular acceleration curve change smoothly and continuously, avoiding the error amplification problem caused by direct angle differentiation.

[0031] 3. The present invention has engineering practicality and can provide support for mission planning of various types of satellites with large-angle maneuverability. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Flow chart of the method of the present invention.

[0033] Figure 2 This is the angular velocity curve of each axis of the data transmission antenna a and b.

[0034] Figure 3 Angular acceleration curves of each axis of the digital transmission antenna a and b. DETAILED DESCRIPTION

[0035] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0036] like Figure 1 As shown, the present invention proposes a prediction method for avoiding satellite-to-ground data transmission failure, which specifically includes the following steps:

[0037] Step 1: Based on the satellite's overall attitude, obtain the projection of the relative vector between the ground station and the satellite in the satellite's own system; multiply the projection by the satellite installation matrix and convert the projection to the antenna coordinate system:

[0038] To illustrate the implementation steps, the present invention first describes a satellite data transmission antenna. The data transmission antenna has two rotational degrees of freedom, with its origin located at the center of the antenna's first-stage rotation axis. The +X axis defines the direction of the first-stage rotation axis, the +Y axis defines the direction of the second-stage rotation axis, and the +Z axis is perpendicular to the antenna mounting base and points outward from the satellite. These three axes satisfy the right-hand rule. During tracking of a ground station, the data transmission antenna rotates about the X and Y axes to keep the +Z axis pointing toward the ground station.

[0039] Step 1.1: The orbit prediction algorithm is calculated based on the satellite's initial orbit, the satellite's full-process attitude, and the ground station's position (longitude, latitude, and altitude). The relative vector v between the ground station and the satellite during the satellite's attitude maneuver period is obtained. i , i is the time.

[0040] The satellite initial orbit required by the present invention includes: orbital epoch time and six orbital numbers at the epoch time; ground station position including longitude, latitude and altitude; the satellite's full-process attitude and the start and end times of the attitude maneuver period are calculated based on the satellite mission requirements.

[0041] By recording the Euler angle of the satellite, the entire process of the satellite's attitude can be discretized as:

[0042]

[0043] Among them, N+1 is the total number of discrete points, t start , t end are the start and end time of the attitude maneuver period, dt is the discrete time step, Int(*) is the rounding operation; t i Represents the moment corresponding to the i-th discrete point, q iRepresents t i The Euler angles of the satellite from the orbital coordinate system to the current system, including the roll angle, pitch angle and yaw angle.

[0044] Step 1.2: The coordinate conversion algorithm converts the relative vector into the projection of the satellite's own system (v i ) sat .

[0045] Step 1.3: According to the installation matrix L of the data transmission antenna relative to the satellite ant_sat , will (v i ) sat Convert to the antenna coordinate system: t i The vector v of the ground station relative to the satellite at this moment i The projection under the satellite system is (v i ) sat , then v i Projection under the antenna coordinate system (v i ) ant The calculation formula is as follows:

[0046] (v i ) ant =L ant_sat (v i ) sat .

[0047] Step 2: Based on the projection of the satellite system (v i ) sat , calculate the rotation angle of the data transmission antenna: the projection of the vector of the ground station relative to the satellite at time ti in the antenna coordinate system (v i ) ant Written in component form, that is:

[0048] (v i ) ant =(v i_ant_x ,v i_ant_y ,v i_ant_z ) T

[0049] Among them, v i_ant_x for (v i ) ant The X-axis coordinate, v i_ant_y for (v i ) ant The Y-axis coordinate, v i_ant_z for (v i ) ant The Z-axis coordinate of .

[0050] Then the rotation angle α of the data transmission antenna around the +X axis is i for:

[0051] α i =atan(-v i_ant_y / v i_ant_z )

[0052] Rotation angle β around the +Y axis i for:

[0053]

[0054] Step 3: Check each moment t point by point i The corresponding rotation angle α i , β i Whether it exceeds the rotation angle range. The rotation range of the data transmission antenna in the X-axis and Y-axis directions is respectively recorded as [α min ,α max ]、[β min ,β max ], if there is a certain moment α i , β i The following relationship is satisfied:

[0055] α i <α min orα i >α max orβ i <β min orβ i >β max

[0056] The process ends, and it is determined that the data transmission antenna cannot track the ground station during the attitude maneuver; otherwise, go to step 4.

[0057] Step 4: Use the polynomial fitting method to calculate the rotation angular velocity curve and the rotation angular acceleration curve according to the rotation angle, and then obtain the rotation angular velocity and rotation angular acceleration at each moment:

[0058] The rotation angle around the X-axis at each moment obtained in step 1 is fitted into a polynomial curve of the following form:

[0059] α(t)=a0+a1(tt start )+a2(tt start ) 2 +…+a n (tt start ) n

[0060] where t∈[t start ,t end ]; n is the polynomial order, and the specific value can be flexibly selected according to the change of the data transmission antenna angle; a i (i=1,…,n) is the coefficient of the i-th power of the polynomial, which can be obtained using the least squares method.

[0061] After taking the derivative of the above curve, the angular velocity curve is shown as follows:

[0062]

[0063] Taking the derivative again, we get the angular acceleration curve as shown below:

[0064]

[0065] Each discrete time point t i Substituting the angular velocity curve and angular acceleration curve respectively, the angular velocity A of the data transmission antenna around the X axis at the corresponding moment can be obtained. d Angular acceleration A dd , which can be expressed as a set of rotational angular velocities Rotational angular acceleration collection

[0066] The same method can be used for the angular velocity and angular acceleration of the data transmission antenna around the Y axis, which can be expressed in a collective manner as follows:

[0067] Step 5: Compare the required angular velocity and angular acceleration of each axis of the digital antenna obtained in step 4 with the maximum angular velocity and maximum angular acceleration that the digital antenna can achieve, and determine whether the maneuverability of the digital antenna meets the requirements for ground station tracking. The maximum design angular velocity and maximum design angular acceleration of the digital antenna around the X axis are respectively The maximum design angular velocity and maximum design angular acceleration around the Y axis are If the following relations are satisfied at the same time:

[0068]

[0069]

[0070]

[0071]

[0072] This indicates that the data transmission antenna can track the ground station during the attitude maneuver; otherwise, it cannot track the ground station. Here, |*| represents the absolute value of all elements in the set, and max{*} represents the maximum value of all elements in the set.

[0073] The following is further explained with reference to the embodiments.

[0074] Assume that a data transmission antenna is installed on the -Y and +Y sides of a satellite, where the -Y side is antenna a and the +Y side is antenna b. The installation matrix from the satellite system to the antenna coordinate system of antenna a is:

[0075]

[0076] The installation matrix from the satellite coordinate system to the antenna coordinate system of antenna b is:

[0077]

[0078] The rotation capability of each data transmission antenna is as follows:

[0079] X-axis rotation range [α min ,α max ]:[-115°,115°];

[0080] Y-axis rotation range [β min ,β max ]:[-102°,102°];

[0081] Maximum angular velocity of X-axis rotation

[0082] Maximum angular velocity of Y-axis rotation

[0083] Maximum angular acceleration of X-axis rotation

[0084] Maximum angular acceleration of X-axis rotation

[0085] The initial orbital parameters of the satellite are shown in Table 1:

[0086] Table 1 Satellite initial orbit parameters

[0087]

[0088]

[0089] The satellite was instructed to perform an attitude maneuver from 6:09:10 to 6:10:10 Beijing Time on April 22, 2019, with a discrete time step of dt = 1 s. The Euler angles of the satellite's local system relative to the orbital system at each time (using a 1-2-3 rotation sequence) are shown in columns 2 to 4 of Table 2. During the attitude maneuver, the satellite was required to simultaneously track a ground station with latitude and longitude information of 39.4785°N, 75.969°E, and altitude of 1000 m, respectively.

[0090] Based on the above information, the present invention is used to calculate the feasibility of data transmission antennas a and b tracking the ground station.

[0091] Step 1: Using the satellite's initial orbit, ground station position, attitude maneuver duration, and overall satellite attitude, calculate the projection of the ground station's relative vector relative to the satellite during the attitude maneuver duration within the satellite's own system, as shown in columns 5-7 of Table 2. Next, calculate the required rotation angles for data transmission antennas a and b to track the ground station, as shown in columns 8-11 of Table 2.

[0092] Table 2 Satellite attitude and data transmission antenna rotation angle corresponding to each discrete time point

[0093]

[0094]

[0095]

[0096]

[0097] As can be seen from Table 2, the X-axis rotation angles required for digital antenna a are all within [-102.14, -90.83]°, and the Y-axis rotation angles are all within [9.9, 14.33]°. The X-axis rotation angles required for digital antenna b are all within [-39.16, -27.86]°, and the Y-axis rotation angles are all within [-14.32, -9.91]°. Both are within the rotation range of the digital antennas, so proceed to the next step.

[0098] Step 2: Fit the theoretical rotation angles of the two axes of the data transmission antenna obtained in Step 1 to polynomial curves with time as the independent variable. This example uses a third-order polynomial curve for fitting. After calling the relevant MATLAB function, the results are as follows:

[0099] The polynomial curve corresponding to the rotation angle of the data transmission antenna a around the X-axis is as follows:

[0100] α a (t)=-90.8493-0.1871(tt start )-5.6547×10 -4 ×(tt start ) 2 +9.1219×10 -6 ×(tt start ) 3

[0101] The polynomial curve corresponding to the rotation angle of the data transmission antenna a around the Y axis is as follows:

[0102] β a (t) = 9.9067 + 0.094 (tt start )+1.1107×10 -4 ×(tt start ) 2-7.5172×10 -6 ×(tt start ) 3

[0103] The polynomial curve corresponding to the rotation angle of the data transmission antenna b around the X-axis is as follows:

[0104] α b (t) = -39.1507 + 0.1871 (tt start )+5.6548×10 -4 ×(tt start ) 2 -9.1220×10 -6 ×(tt start ) 3

[0105] The polynomial curve corresponding to the rotation angle of the data transmission antenna b around the Y axis is as follows:

[0106] β b (t)=-9.9067-0.094(tt start )-1.1107×10 -4 ×(tt start ) 2 +7.5172×10 -6 ×(tt start ) 3

[0107] By taking the derivative of the step polynomial curve, we can obtain the angular velocity and angular acceleration required by the two axes of the data transmission antenna at each moment of attitude maneuver. Figure 2 The angular velocity curves of each axis of the digital transmission antenna a and b are given. Figure 3 The angular acceleration curves of each axis of the data transmission antenna a and b are given, where Figure 2 and Figure 3 The horizontal axis is the second count relative to 6:09:10 Beijing time on April 22, 2019.

[0108] Step 3: Compare the angular velocity and angular acceleration required for each axis of the digital antenna obtained in Step 2 with the maximum angular velocity and maximum angular acceleration achievable by the digital antenna to determine whether the digital antenna's maneuverability meets the requirements for ground station tracking. The maximum angular velocity of digital antennas a and b around the X axis is 0.2° / s, and the maximum angular velocity around the Y axis is 0.1° / s, both of which are less than the angular velocity limit of 2.5° / s; the maximum angular acceleration of each axis of the two antennas is 2.5×10-3° / s 2 , are all less than 0.1° / s 2 It can be concluded that during the satellite attitude maneuver, both data transmission antennas a and b can track the ground station.

[0109] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for predicting satellite-to-ground data transmission failure, characterized in that: The specific steps include: Step 1: Based on the satellite's full-process attitude, obtain the projection of the relative vector between the ground station and the satellite in the satellite's own system; multiply the projection by the satellite installation matrix to convert the projection to the antenna coordinate system; Step 2: Calculate the rotation angle of the antenna at each moment based on the projection of the relative vector in the antenna coordinate system; Step 3: Check whether the rotation angle at each moment exceeds the rotation angle range. If it does not exceed the range, proceed to step 4; if it exceeds the range, the evaluation result is data transmission failure. Step 4: Fit the rotation angles at all moments into a curve, and obtain the rotation angular velocity and rotation angular acceleration at each moment after derivation; Step 5: Determine whether the rotational angular velocity exceeds the rotational angular velocity range, and determine whether the rotational angular acceleration exceeds the rotational angular acceleration range; if both the rotational angular velocity and the rotational angular acceleration are within the range, the evaluation result is that the data transmission is successful, otherwise, the data transmission fails; The specific method of step 2 is: The projection of the antenna coordinate system OXYZ (v i ) ant Written in component form, that is: (v i ) ant =(v i_ant_x ,v i_ant_y ,v i_ant_z ) T Among them, v i_ant_x for (v i ) ant The X-axis coordinate, v i_ant_y for (v i ) ant The Y-axis coordinate, v i_ant_z for (v i ) ant The Z-axis coordinate of Then the rotation angle α of the data transmission antenna around the +X axis is i for: α i =atan(-v i_ant_y / v i_ant_z ) The rotation angle β of the data transmission antenna around the +Y axis i for: The specific method of step 4 is: The rotation angle around the X-axis at each moment is fitted into a polynomial curve of the following form: α(t)=a0+a1(t-t start )+a2(t-t start ) 2 +…+a n (t-t start ) n where t∈[t start ,t end ], t start , t end are the start and end time of the attitude maneuver period respectively; n is the polynomial order, and the specific value is selected according to the change of the data transmission antenna angle; a i (i=1,…,n) is the coefficient of the i-th power of the polynomial, obtained by the least squares method; After taking the derivative of the above curve, the angular velocity curve is shown as follows: Taking the derivative again, we get the angular acceleration curve as shown below: Each discrete time point t i Substitute the angular velocity curve and angular acceleration curve respectively to obtain the angular velocity A of the data transmission antenna around the X axis at the corresponding moment. d Angular acceleration A dd , expressed as a set of rotational angular velocities Rotational angular acceleration collection The same method is used for the angular velocity and angular acceleration of the data transmission antenna around the Y axis, which are expressed in a collective manner as follows:

2. The method according to claim 1, wherein The specific method of step 1 is: Step 1.1: Based on the satellite's initial orbit, the satellite's full-process attitude, and the ground station's position, perform orbit prediction and obtain the relative vector v between the ground station and the satellite during the satellite's attitude maneuver period. i , i is the time; Step 1.2: Set the relative vector v i Coordinates are converted to projections in the satellite's native system (v i ) sat ; Step 1.3, projection (v i ) sat With satellite installation matrix L ant_sat Multiply and transform the projection into the antenna coordinate system (v i ) ant .

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