Single-satellite high-precision cooperative remote sensing method

Abstract

The application discloses a single-satellite high-precision cooperative remote sensing method, which is applied to a satellite platform with multiple loads, and payloads are connected with the satellite platform through flexible cables, contactless actuators and the satellite platform to form a multi-loop control system; the method comprises the following steps: (1) equivalent the flexible cable to a combination of multiple beads, springs and dampers; (2) establishing force equations and moment equations of all payloads, all flexible cables and the satellite platform; establishing control equations and constraint conditions of the multi-loop control system; (3) according to the control equations and constraint conditions of the multi-loop control system, the payloads are oriented, multiple payloads are directed to the same target, and the distance between the payloads and the satellite platform is controlled within a critical distance. Through the contactless actuators, the flexible cable dynamics modeling and the establishment of the control equations of the multi-loop control system, the super-static super-stable and cooperative work of multiple payloads on a single satellite platform are realized.

Description

Technical Field

[0001] The present invention relates to the field of satellite remote sensing, and in particular to a single-satellite high-precision collaborative remote sensing method. Background Art

[0002] Traditional Earth observation remote sensing satellite platforms carrying a single payload can only cover a limited target area per orbital cycle. For larger target areas, multiple orbital cycles are required to stitch together the image strips obtained each time. For instantaneous natural disasters, Earth observation remote sensing satellite platforms must obtain information about the target area in the shortest possible time. The time consumed by traditional single-satellite, single-payload remote sensing satellite platforms for multiple observations can result in missing the optimal rescue opportunity. As a countermeasure, some scholars have proposed the concept of a multi-payload remote sensing satellite platform, in which a single remote sensing satellite carries multiple payloads working in coordination. For example, by rationally dividing the target area in advance and utilizing multiple onboard cameras on a single satellite for coordinated observation, it is possible to cover the entire target area within a single orbital cycle. Clearly, a multi-payload satellite solution saves both time and in-orbit operating costs. Summary of the Invention

[0003] In view of the above-mentioned defects of the prior art, the purpose of the present invention is to provide a single-satellite high-precision collaborative remote sensing method to improve the detection accuracy and collaborative detection capability of existing remote sensing satellite platforms.

[0004] To achieve the above objectives, the present invention provides a single-satellite high-precision collaborative remote sensing method, which is applied to a multi-payload satellite platform. The satellite platform and the payloads constitute a multi-loop control system. The satellite platform and each payload are connected by a flexible cable, and the attitude of the payload is adjusted by a contactless actuator.

[0005] The method comprises the following steps:

[0006] (1) The flexible cable is equivalent to a combination of multiple beads, springs, and dampers: multiple beads are connected in series, and the springs and dampers are arranged in parallel between two adjacent beads;

[0007] (2) Establish the force and torque equations for all payloads, all flexible cables, and the satellite platform; establish the control equations and constraints for the multi-loop control system;

[0008] (3) Obtain the position and attitude data of all payloads. For any payload n, calculate the following based on the attitude data of payload n: the gravity, atmospheric drag, cable force, gravity gradient torque, and cable torque acting on payload n when the satellite platform is operating in low-Earth orbit;

[0009] Obtain the position and attitude data of the satellite platform, and calculate the following based on the position and attitude data of the satellite platform and the relative position and attitude data of each payload: the gravitational force on the satellite platform, atmospheric drag, the forces acting on each cable, the gravitational gradient torque, and the torque acting on each cable;

[0010] According to the control equations and constraints of the multi-loop control system, the payload is oriented, multiple payloads are pointed to the same target, and the distance between the payload and the satellite platform is controlled within a critical distance.

[0011] Furthermore, the expression of the spring-damper-mass point model of the flexible cable is:

[0012]

[0013] In the above formula, F i,kc is the force of the two spring / damping units acting on the bead i (i = 1 to N-1); k is the spring stiffness coefficient; c is the damping coefficient; l i =r i -r i-1 v is the vector from bead point i-1 to bead point i; i is the velocity vector of bead i; is the vector l i The modulus of Δl i =l i -l initial is the extension of the i-th spring / damper unit, l initial is the initial length of the spring / damper element.

[0014] The single-satellite high-precision collaborative remote sensing method of the present invention achieves the following technical effects:

[0015] (1) A non-contact design is adopted between the satellite platform and the payload to ensure ultra-high precision and ultra-high stability of the payload;

[0016] (2) Flexible cable dynamics modeling fully considers the stiffness, damping, and mass characteristics of the cable, making the model more accurate and more in line with engineering practice;

[0017] (3) Establishing the control equations of a multi-loop control system, which can simultaneously achieve ultra-quiet and ultra-stable operation of multiple payloads, laying the foundation for multi-payload collaborative detection;

[0018] (4) Realizing the collaborative operation of multiple payloads on a single satellite platform can effectively reduce the cost of satellite launch and operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a structural diagram of a single-star high-precision collaborative remote sensing satellite platform;

[0020] Figure 2 It is a multi-loop control system;

[0021] Figure 3 is the relative position of the coil and magnet of the contactless actuator of the two payloads;

[0022] Figure 4 are the payload attitude angles of the two payloads;

[0023] Figure 5 is the payload angular velocity of the two payloads;

[0024] Figure 6 is the satellite platform attitude angle;

[0025] Figure 7 is the satellite platform angular velocity;

[0026] Figure 8 It is a spring-mass point model of a flexible cable in the prior art;

[0027] Figure 9 The spring-damper-mass point model of the flexible cable of the present invention;

[0028] Figure 10 It is a super-quiet satellite platform configuration of the existing technology;

[0029] Figure 11 This is the single-satellite collaborative remote sensing platform configuration of the present invention;

[0030] Figure 12 It is the existing technology of dual-satellite single-target collaborative detection;

[0031] Figure 13 This is the single-star single-target collaborative detection of the present invention. DETAILED DESCRIPTION

[0032] To further illustrate various embodiments, the present invention is provided with accompanying drawings. These drawings form part of the present disclosure and are primarily used to illustrate the embodiments and, in conjunction with the relevant description in the specification, to explain the operating principles of the embodiments. By referring to these drawings, one of ordinary skill in the art will understand other possible embodiments and the advantages of the present invention. The components in the figures are not drawn to scale, and similar reference numerals are generally used to represent similar components.

[0033] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0034] In order to improve the observation capability of a single satellite, two payloads can be installed in parallel on the satellite platform, such as Figure 1 shown.

[0035] The present invention provides a single-satellite high-precision collaborative remote sensing method, which is applied to the above-mentioned multi-payload remote sensing satellite platform to improve the detection accuracy and collaborative detection capability of the existing remote sensing satellite platform.

[0036] 1. The satellite platform and the payload are connected by a flexible cable, and the attitude of the payload is adjusted by a contactless actuator (such as an electromagnetic actuator).

[0037] In this method, the flexible cable dynamics model is firstly developed. The flexible cable is equivalent to a combination of beads, springs and dampers in this platform. Its detailed structure is as follows: Figure 1 shown.

[0038] The expression of the spring-damper-mass point model of the flexible cable is:

[0039]

[0040] In the above formula, F i,kc is the force of the two spring / damping units acting on the bead i (i = 1 to N-1); k is the spring stiffness coefficient; c is the damping coefficient; l i =r i -r i-1 v is the vector from bead point i-1 to bead point i; i is the velocity vector of bead i; is the vector l i The modulus of Δl i =l i -l initial is the extension of the i-th spring / damper unit, l initial is the initial length of the spring / damper element.

[0041] In the flexible cable dynamics modeling of this embodiment, the stiffness, damping, and mass characteristics of the cable are fully considered, so the model is more accurate and more in line with engineering practice.

[0042] 2. Force analysis of a single-star high-precision collaborative remote sensing satellite system, and establishing force and torque equations acting on the payload and satellite platform.

[0043] Assuming that the remote sensing satellite platform is operating in low Earth orbit, the forces and moments acting on payload I are:

[0044]

[0045]

[0046]

[0047]

[0048] T ⅠPu =d ⅠP ×F ⅠPu

[0049] Among them, F ⅠPg 、F ⅠPd 、F ⅠPu 、T ⅠPd 、T ⅠPu They are the gravity, atmospheric drag, cable force, gravity gradient torque, and cable torque acting on payload I respectively.

[0050] The forces and moments acting on payload II are:

[0051]

[0052]

[0053]

[0054]

[0055] T ⅡPu =d ⅡP ×F ⅡPu

[0056] Similarly, if multiple payloads are included, the forces and moments acting on payload n are:

[0057]

[0058]

[0059]

[0060]

[0061] T nPu =d nP ×F nPu

[0062] Among them, F nPg 、F nPd 、F nPu 、T nPd 、T nPu are the gravity, atmospheric drag, cable force, gravitational gradient torque, and cable torque acting on the payload n, respectively.

[0063] The force acting on flexible cable No. 1 is:

[0064]

[0065]

[0066] The force acting on flexible cable No. Ⅱ is:

[0067]

[0068]

[0069] Similarly, if there is a flexible cable n, the force acting on the flexible cable n is:

[0070]

[0071]

[0072] Among them, F nig 、F nBi are the attraction acting on the i-th bead point on the n-th flexible cable and the cooperative force of the adjacent spring-damper units, respectively.

[0073] The force acting on the satellite platform is:

[0074]

[0075]

[0076]

[0077]

[0078] T nSu =d nS ×F nSu

[0079] Among them, F Sg 、F Sd 、F nSu 、T Sd 、T nSu They are the gravity acting on the satellite platform, atmospheric drag, the force of the nth flexible cable, the gravitational gradient torque, and the torque of the nth flexible cable.

[0080] 3. Derivation of the multi-rigid-body flexible dynamics of a single-star high-precision collaborative remote sensing satellite system. Based on the force analysis results, the motion equations of the satellite platform, payload, and flexible cables are established.

[0081] The equation of motion for the payload n is as follows:

[0082]

[0083]

[0084]

[0085]

[0086] Among them, r nP 、v nP ,q nP 、ω nP 、 M nP , I nP They are the position vector, velocity vector, attitude quaternion, angular velocity vector, quaternion form of angular velocity vector, mass, and moment of inertia of payload n respectively.

[0087] The equation of motion of the satellite platform is as follows:

[0088]

[0089]

[0090]

[0091]

[0092]

[0093] Among them, r S 、v S ,q S 、ω S 、 M S , I S ,η,ζ,Ω,B t 、B r They are respectively the position vector, velocity vector, attitude quaternion, angular velocity vector, quaternion form of angular velocity vector, mass, moment of inertia, flexible coordinates, damping coefficient, modal frequency of flexible attachment, translational coupling matrix between flexible attachment and satellite platform, and rotational coupling matrix between flexible attachment and satellite platform.

[0094] The motion equation of the flexible cable n is as follows:

[0095]

[0096]

[0097] Among them, r ni 、v ni 、M ni are the position vector, velocity vector, and mass of the i-th bead point in the flexible cable n, respectively.

[0098] 4. Multi-loop controller design

[0099] The control objectives of this system are as follows:

[0100] a. Both payloads achieve high pointing performance;

[0101] b. Ensure the critical distance between the payload and the satellite platform.

[0102] Based on the above objectives, a multi-loop control system is designed, such as Figure 2 As shown. The multi-loop control system includes two payloads, and the control law of the multi-loop control system is designed as follows:

[0103] T ⅠPc =K ⅠPP (q ⅠPv0 -q ⅠPv )+K ⅠPD (ω ⅠP0 -ω ⅠP )

[0104] T ⅡPc =K ⅡPP (q ⅡPv0 -q ⅡPv )+K ⅡPD (ω ⅡP0 -ω ⅡP )

[0105]

[0106]

[0107] T Sc =K RAP (q Rv0 -q Rv )+K RAD (ω R0 -ω R )

[0108] Similarly, when there are multiple payloads on the satellite platform, the control law of the multi-loop control system can be updated as follows:

[0109] T nPc =K nPP (q nPv0 -q nPv )+K nPD (ω nP0 -ω nP )

[0110]

[0111] T Sc =K RAP (q Rv0 -qRv )+K RAD (ω R0 -ω R )

[0112] Where, subscript n represents the nth payload; T nPc , K nPP ,q nPv0 ,q nPv , K nPD 、ω nP0 、ω nP 、ω nP0 are the control torque, proportional coefficient, expected quaternion of payload n, current quaternion of payload n, differential coefficient, expected angular velocity, and current angular velocity of the attitude control loop of payload n, respectively; F nPc , K nRTP , ρ nr0 , ρ nr , K nRTD 、 are the control force, proportional coefficient, expected relative position, current relative position, differential coefficient, expected relative speed, and current relative speed of the relative control loop between the satellite platform and the payload n, respectively; T Sc , K RAP ,q Rv0 ,q Rv , K RAD 、ω R0 、ω R They are the control torque, proportional coefficient, expected relative quaternion, current relative quaternion, differential coefficient, expected relative angular velocity, and current relative angular velocity of the relative attitude control loop between the satellite platform and payload n.

[0113] 5. Simulation analysis

[0114] In order to verify the collaborative detection capability and detection accuracy of the proposed single-line high-precision remote sensing satellite platform, a single-target multi-payload collaborative detection mission was designed: the two payloads synchronously achieved the orientation task of the attitude angle (0° 0° 0°) in the Earth-centered inertial coordinate system.

[0115] The purpose of the observation mission is to converge the desired attitude deviation of the two payload body coordinate systems relative to the Earth-centered inertial coordinate system to zero, while controlling the relative position and attitude of the satellite platform and the payload to ensure that the contactless actuator is always in normal working condition (that is, the range of action of the coil and magnet of the contactless actuator remains within 2mm).

[0116] Based on the established single-line high-precision remote sensing satellite platform motion equation, the simulation results of the single-target collaborative observation mission are as follows: Figures 3 to 7 shown.

[0117] According to the analysis of the above results, when the two payloads of the single-star high-precision remote sensing satellite platform are oriented to the same target in inertial space, the designed multi-loop control system can ensure the normal operation of the two actuators, and the payload has high pointing performance, which verifies the effectiveness of the proposed single-star high-precision collaborative remote sensing satellite platform in performing collaborative observation tasks.

[0118] (1) Different structures

[0119] a. The flexible cable model in this invention is more accurate than the existing solutions. Existing studies generally use spring models or spring-mass point models to model the flexible cables between satellite platforms and payloads, such as Figure 8 As shown in the figure, the model takes into account the mass and stiffness characteristics of the cable, but ignores the damping characteristics of the cable, so it deviates from reality to a certain extent. Based on the existing spring-mass point model, the present invention further considers the damping characteristics and establishes the following Figure 9 The spring-damper-mass point model shown in Figure 1 takes into account the stiffness, damping, and mass properties of the cable, making it closer to reality.

[0120] b. The satellite configuration of the present invention can realize the contactless design of multiple payloads and satellite platforms.

[0121] Based on Figure 10 The traditional ultra-quiet satellite platform configuration shown in FIG can only ensure that a single payload can achieve ultra-high precision and ultra-high stability. The single-star collaborative remote sensing satellite platform of the present invention, such as Figure 11 As shown, it can carry multiple payloads, and multiple payloads are evenly distributed on the satellite platform to achieve contactless design, ensuring that each payload is ultra-quiet and ultra-stable, providing a basis for single-satellite high-precision collaborative remote sensing.

[0122] (2) Functional differences:

[0123] Since the traditional ultra-quiet satellite configuration can only achieve ultra-quiet and ultra-stable single payload, for single-target detection missions, it is necessary to launch multiple ultra-quiet satellites to achieve collaborative detection missions, such as Figure 12 As shown. The launch cost and satellite in-orbit operation cost of launching multiple detection satellites are obviously higher than launching a single satellite. The single-satellite collaborative remote sensing platform of the present invention can realize the collaborative single-target detection of multiple payloads on the basis of a satellite platform, such as Figure 13 shown.

[0124] The single-satellite high-precision collaborative remote sensing method of the present invention can achieve the following technical effects:

[0125] (1) A non-contact design is adopted between the satellite platform and the payload to ensure ultra-high precision and ultra-high stability of the payload;

[0126] (2) Flexible cable dynamics modeling fully considers the stiffness, damping, and mass characteristics of the cable, making the model more accurate and more in line with engineering practice;

[0127] (3) Establishing the control equations of a multi-loop control system, which can simultaneously achieve ultra-quiet and ultra-stable operation of multiple payloads, laying the foundation for multi-payload collaborative detection;

[0128] (4) Realizing the collaborative operation of multiple payloads on a single satellite platform can effectively reduce the cost of satellite launch and operation.

[0129] Although the present invention has been particularly shown and described in conjunction with preferred embodiments, it will be understood by those skilled in the art that various changes in form and details may be made to the present invention without departing from the spirit and scope of the invention as defined in the appended claims, and all such changes are within the scope of protection of the present invention.

Claims

1. A single-satellite high-precision collaborative remote sensing method, applied to a multi-payload satellite platform, characterized by: The satellite platform and payload form a multi-loop control system. Flexible cables are used to connect the satellite platform and each payload, and contactless actuators are used to adjust the payload's attitude. The method comprises the following steps: (1) The flexible cable is equivalent to a combination of multiple beads, springs, and dampers: multiple beads are connected in series, and the springs and dampers are arranged in parallel between two adjacent beads; (2) Establish the force and torque equations for all payloads, all flexible cables, and the satellite platform; establish the control equations and constraints for the multi-loop control system; (3) Obtain the position and attitude data of all payloads. For any payload n, calculate the following based on the attitude data of payload n: the gravity, atmospheric drag, cable force, gravity gradient torque, and cable torque acting on payload n when the satellite platform is operating in low-Earth orbit; Obtain the position and attitude data of the satellite platform, and calculate the following based on the position and attitude data of the satellite platform and the relative position and attitude data of each payload: the gravitational force on the satellite platform, atmospheric drag, the forces acting on each cable, the gravitational gradient torque, and the torque acting on each cable; According to the control equations and constraints of the multi-loop control system, the payload is oriented, multiple payloads are pointed to the same target, and the distance between the payload and the satellite platform is controlled within a critical distance.

2. The single-satellite high-precision collaborative remote sensing method according to claim 1, characterized in that: The expression of the spring-damper-mass point model of the flexible cable is: In the above formula, F i,kc is the force of the two spring / damping units acting on the bead i (i = 1 to N-1); k is the spring stiffness coefficient; c is the damping coefficient; l i =r i -r i-1 v is the vector from bead point i-1 to bead point i; i is the velocity vector of bead i; is the vector l i The model; Δl i =l i -l initial is the extension of the i-th spring / damper unit, l initial is the initial length of the spring / damper element.

3. The single-satellite high-precision collaborative remote sensing method according to claim 2, characterized in that: The force equation and moment equation include: Assume that the remote sensing satellite platform operates in low Earth orbit; The forces and moments acting on the payload n are: T nPu =d nP ×F nPu Among them, F nPg 、F nPd 、F nPu 、T nPd 、T nPu are the gravity, atmospheric drag, cable force, gravity gradient torque, and cable torque acting on the payload n, respectively; The force acting on the flexible cable n is: Among them, F nig 、F nBi are the attraction force acting on the i-th bead point on the n-th flexible cable and the cooperative force of the adjacent spring-damper units; The force acting on the satellite platform is: T nSu =d nS ×F nSu Among them, F Sg 、F Sd 、F nSu 、T Sd 、T nSu They are the gravity acting on the satellite platform, atmospheric drag, the force of the nth flexible cable, the gravitational gradient torque, and the torque of the nth flexible cable.

4. The single-satellite high-precision collaborative remote sensing method according to claim 2, characterized in that: The equation of motion for the payload n is as follows: Among them, r nP 、v nP ,q nP 、ω nP 、 M nP , I nP are the position vector, velocity vector, attitude quaternion, angular velocity vector, quaternion form of angular velocity vector, mass, and moment of inertia of payload n respectively; The motion equation of the satellite platform is as follows: Among them, r S 、v S ,q S 、ω S 、 M S , I S ,η,ζ,Ω,B t 、B r They are the position vector, velocity vector, attitude quaternion, angular velocity vector, quaternion form of angular velocity vector, mass, moment of inertia, flexible coordinates, damping coefficient, modal frequency of flexible attachment, translational coupling matrix between flexible attachment and satellite platform, and rotational coupling matrix between flexible attachment and satellite platform of the satellite platform; The motion equation of the flexible cable n is as follows: Among them, r ni 、v ni 、M ni are the position vector, velocity vector, and mass of the i-th bead point in the flexible cable n, respectively.

5. The single-satellite high-precision collaborative remote sensing method according to claim 2, characterized in that: The control equations and constraints of the multi-loop control system are as follows: T nPc =K nPP (q nPv0 -q nPv )+K nPD (ω nP0 -ω nP ) T Sc =K RAP (q Rv0 -q Rv )+K RAD (ω R0 -ω R ) Where, subscript n represents the nth payload; T nPc , K nPP ,q nPv0 ,q nPv , K nPD 、ω nP0 、ω nP 、ω nP0 are the control torque, proportional coefficient, expected quaternion of payload n, current quaternion of payload n, differential coefficient, expected angular velocity, and current angular velocity of the attitude control loop of payload n, respectively; F nPc , K nRTP , ρ nr0 , ρ nr , K nRTD 、 are the control force, proportional coefficient, expected relative position, current relative position, differential coefficient, expected relative velocity, and current relative velocity of the relative control loop between the satellite platform and the payload n respectively; T Sc , K RAP ,q Rv0 ,q Rv , K RAD 、ω R0 、ω R are the control torque, proportional coefficient, expected relative quaternion, current relative quaternion, differential coefficient, expected relative angular velocity, and current relative angular velocity of the relative attitude control loop between the satellite platform and the payload n, respectively; Constraints: The non-contact actuator is always in normal working condition.

6. The single-satellite high-precision collaborative remote sensing method according to claim 5, characterized in that: The contactless actuator is an electromagnetic actuator, and the constraint condition is specifically that the action range of the coil and magnet of the electromagnetic actuator is kept within a set distance.

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