High-dynamic online interference estimation method and system for on-satellite ring sweep load

Abstract

The invention relates to an on-satellite ring sweep load high-dynamic on-line interference estimation method, which designs a high-dynamic interference on-line prediction method based on an observer for periodic characteristics of interference, and realizes high-precision estimation of fast-changing interference. And the high-precision estimated value of the disturbance torque is used as a feed-forward item of the satellite attitude control torque, so that load disturbance suppression is effectively realized, and the pointing precision and stability of the satellite are ensured.

Description

Technical Field

[0001] The invention relates to a high-dynamic online interference estimation method and system for on-board ring-scanning loads, belonging to the technical field of spacecraft control. Background Art

[0002] With the continuous growth of space mission demands, satellites will carry more and more types of payloads, a large part of which need to keep rotating during normal operation, such as ocean color meters, scanning microwave radiometers, microwave scatterometers, microwave imagers, scanning mirrors, etc. Some imaging satellites will also configure the payload on a single-axis turntable to achieve multi-target monitoring and tracking through turntable rotation.

[0003] High-speed rotating payloads will cause interference to the satellite. If interference compensation is not performed, the satellite's attitude stability and pointing accuracy will decrease, affecting the satellite's scientific mission. When this interference is severe, it may even stimulate the vibration of flexible accessories (such as solar panels), causing the satellite's attitude to oscillate.

[0004] At present, the commonly used interference estimation methods on satellites are mainly based on estimating slowly varying interference, which is no longer applicable when the interference changes rapidly. Summary of the invention

[0005] The technical problem to be solved by the present invention is: to overcome the shortcomings of the prior art, to propose a high-dynamic online interference estimation method for on-board circumferential scanning payloads, to use the high-precision estimation value of the interference torque as the feedforward item of the satellite attitude control torque, to effectively realize payload interference suppression, and to ensure the pointing accuracy and stability of the satellite.

[0006] The technical solution adopted by the present invention is:

[0007] A high-dynamic online interference estimation method for on-board ring-scanning payload comprises the following steps:

[0008] (1) Satellite attitude dynamics modeling and rotation load disturbance torque modeling;

[0009] (2) Obtain the disturbance state equation corresponding to the model;

[0010] (3) Design a state observer;

[0011] (4) Based on the state observer, the disturbance torque is estimated online to obtain the estimated value of the disturbance torque.

[0012] (5) The estimated value of the disturbance torque is used as the feedforward term of the satellite attitude control torque to achieve payload disturbance suppression.

[0013] Furthermore, the satellite attitude dynamics modeling is specifically as follows:

[0014] Considering the satellite center body as a rigid body, the satellite dynamic equation in the x-axis direction considering the load motion disturbance is expressed as:

[0015]

[0016] In the formula, ω sx is the satellite angular velocity, and the upper point represents the first-order derivative; J x is the moment of inertia of the star, which is a positive definite symmetric matrix; τ sx is the satellite attitude control torque; τ hx It is the disturbance torque generated on the star when the load moves.

[0017] Furthermore, the rotating load interference torque model is used, that is, the interference torque τ generated by the load on the star when it moves hx Expressed as:

[0018] τ hx =C0+C1sin(ω h t)+C2cos(ω h t)

[0019] Among them, ω h is the rotation speed of the sweeping load, t is the motion time, C0, C1, C2 are unknown constants.

[0020] Furthermore, the interference state equation corresponding to the acquisition model is specifically:

[0021] Using the disturbance dynamics characteristics, τ hx Taking the second derivative with respect to time, we get

[0022]

[0023] Defining state quantities

[0024] x1=τ hx , x3=J x ω sx ,

[0025] ωh x is the component of ωh on the x-axis;

[0026] The interference state equation is obtained

[0027]

[0028] Let X = [x1 x2 x3 x4] T , U = τ sx ,get

[0029]

[0030] Y=CX

[0031] in,

[0032] C = [0 0 1 0] is the state output matrix

[0033] Y is the measured output.

[0034] Furthermore, the state observer design is specifically as follows:

[0035] Assume that the observer gain matrix L = [h1 h2 h3 h4] T , then the characteristic polynomial of the closed-loop system based on the observer is

[0036]

[0037] Where s is the Laplace transform variable, I is the 4×4 unit matrix, and C=

[0010] is the state output matrix;

[0038] Design p = [abcd], p is the configuration pole, let

[0039] a=c=-ξω n +ξω n j

[0040] b=d=-ξω n -ξω n j

[0041] a1=-ξω n

[0042] Among them, j is the imaginary unit, ξ and ω n are observer design parameters, respectively represent the damping ratio and frequency, then the closed-loop characteristic expression is

[0043]

[0044] From this we can get

[0045] h3=-4a1

[0046]

[0047]

[0048] Furthermore, the online estimation of the disturbance torque based on the state observer is specifically as follows:

[0049] Definition A o =A-LC, B o =[LB]

[0050] Assume the control period is T c , then the discretized state space matrix of the rotating load disturbance torque model is

[0051]

[0052] The discretized state equation is

[0053] Z x (k) = G x Z x (k-1)+H x U x (k)

[0054] in, is the measured value of the angular velocity of the star, Z x (k) is the discrete value of the state variable X;

[0055] The disturbance torque estimate is obtained from this

[0056]

[0057] On the other hand, the present invention also proposes a high-dynamic online interference estimation system for on-board ring scanning payload, comprising:

[0058] Disturbance torque modeling module: satellite attitude dynamics modeling and rotation load disturbance torque modeling; the satellite center body is regarded as a rigid body, and the satellite x-axis dynamic equation considering the load motion disturbance is expressed as:

[0059]

[0060] In the formula, ω sx is the satellite angular velocity, and the upper point represents the first-order derivative; J x is the moment of inertia of the star, which is a positive definite symmetric matrix; τ sx is the satellite attitude control torque; τ hx It is the disturbance torque generated on the star when the load moves;

[0061] The rotating load interference torque modeling, that is, the interference torque τ generated by the load on the star when it moves hx Expressed as:

[0062] τ hx =C0+C1sin(ω h t)+C2cos(ω h t)

[0063] Among them, ω h is the speed of the sweep load, t is the motion time, C0, C1, C2 are unknown constants;

[0064] Interference state equation acquisition module: obtain the interference state equation corresponding to the model, specifically:

[0065] Using the disturbance dynamics characteristics, τ hx Taking the second derivative with respect to time, we get

[0066]

[0067] Defining state quantities

[0068] x1=τ hx , x3=J x ω sx ,

[0069] ωh x is the component of ωh on the x-axis;

[0070] The interference state equation is obtained

[0071]

[0072] Let X = [x1 x2 x3 x4] T , U = τ sx ,get

[0073]

[0074] Y=CX

[0075] in,

[0076] C = [0 0 1 0] is the state output matrix

[0077] Y is the measured output;

[0078] Observer design module: design state observer;

[0079] Disturbance torque online estimation module: online estimation of disturbance torque based on state observer.

[0080] Compared with the prior art, the present invention has the following beneficial effects:

[0081] (1) The method of the present invention estimates the interference torque of the rotating load with fixed periodic interference, fully exploits the dynamic characteristics of the load interference, and uses the high-precision estimation value of the interference torque as the feedforward term of the satellite attitude control torque, effectively realizing the load interference suppression and ensuring the pointing accuracy and stability of the satellite.

[0082] (2) The method of the present invention can be applied to the high-precision and high-stability control of spacecraft equipped with circumferential scanning payloads. The method constructs an observer-based state estimation method for high-precision interference estimation, and performs load suppression through controller feedforward compensation design. The improved control strategy can effectively meet the high-precision and high-stability pointing requirements of the system camera. The entire algorithm design is simple, and the workload of parameter debugging is small.

[0083] (3) The present invention proposes a new solution to the problem of suppressing the interference caused by the rotating load in the satellite attitude control. It does not require additional data input and is simple to calculate. The algorithm can be adapted to a large class of satellite systems with non-cooperative moving target tracking requirements and has strong engineering practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0084] Figure 1 is a flow chart of the method of the present invention;

[0085] Figure 2 Schematic diagram of the estimated value and true value of the disturbance torque (Nm);

[0086] Figure 3 Schematic diagram of the attitude angle of the star (deg);

[0087] Figure 4 Schematic diagram of satellite stability (deg / s). DETAILED DESCRIPTION

[0088] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0089] like Figure 1 As shown, the present invention relates to a high-dynamic online interference estimation method for on-board ring scanning payload, comprising the following steps:

[0090] Step 1: Modeling satellite attitude dynamics and rotation load disturbance torque;

[0091] Considering the satellite center body as a rigid body, the satellite dynamic equation in the x-axis direction considering the load motion disturbance can be simplified as follows:

[0092]

[0093] In the formula, ω sx is the satellite angular velocity, and the upper point represents the first-order derivative; J x is the moment of inertia of the star, which is a positive definite symmetric matrix; τ sx is the satellite attitude control torque; τ hx is the disturbance torque generated by the load on the star when it moves, and its model is

[0094] τ hx=C0+C1 sin(ω h t)+C2cos(ω h t)

[0095] Among them, ω h is the rotation speed of the sweeping load, t is the motion time, C0, C1, C2 are unknown constants.

[0096] Step 2: Obtain the interference state equation corresponding to the model;

[0097] Using the disturbance dynamics characteristics, τ hx Taking the second derivative with respect to time, we get

[0098]

[0099] ωh x is the component of ωh on the x-axis;

[0100] Defining state quantities

[0101] x1=τ hx , x3=J x ω sx ,

[0102] Get the state equation

[0103]

[0104] Let X = [x1 x2 x3 x4] T , U = τ sx , can be obtained

[0105]

[0106] Y=CX

[0107] in,

[0108]

[0109] C =

[0010] is the state output matrix, and Y is the measured output.

[0110] Step 3: Design the state observer.

[0111] Assume that the observer gain matrix L = [h1 h2 h3 h4] T , then the characteristic polynomial of the closed-loop system based on the observer is

[0112]

[0113] Where s is the Laplace transform variable, I is the 4×4 unit matrix, and C=[0 0 1 0] is the state output matrix;

[0114] Design p = [abcd], where p is the configuration pole, let

[0115] a=c=-ξω n +ξω n j

[0116] b=d=-ξω n -ξω n j

[0117] a1=-ξω n

[0118] Among them, j is the imaginary unit, ξ and ω n are observer design parameters, respectively represent the damping ratio and frequency, then the closed-loop characteristic expression is

[0119]

[0120] From this we can get

[0121] h3=-4a1

[0122]

[0123] Step 4: Online estimation of disturbance torque based on state observer.

[0124] Next, disturbance torque estimation is performed based on the observer.

[0125] definition

[0126] A o =A-LC, B o =[LB]

[0127] Assume the control period is T c , then the discretized state space matrix of the disturbance moment estimation model is

[0128]

[0129] Therefore, the discretized state equation is

[0130] Z x (k) = G x Z x (k-1)+H x U x (k)

[0131] in, is the measured value of the angular velocity of the star, Zx (k) is the discrete value of the state variable X.

[0132] The estimated value of the turntable disturbance torque is obtained

[0133]

[0134] The estimated value of the disturbance torque is used as the feedforward term of the satellite attitude control torque to achieve payload disturbance suppression.

[0135] The present invention will be further described below in conjunction with the embodiments.

[0136] Example:

[0137] Taking a certain satellite as an example, a set of typical on-orbit working conditions are used to simulate and verify the method proposed in this patent application. The satellite is initially in the normal ground-to-earth mode. At t = 30s, the circumferential scanning load is started, and the rotation speed is 36° / s. The satellite is affected by the circumferential scanning interference torque. At t = 80s, the circumferential scanning load interference torque estimation is turned on, and the estimation result is introduced into the control loop for interference compensation. It can be seen from the simulation curve that the interference estimation can achieve high-precision estimation of the load interference, and the satellite stability is improved from 0.008deg / s to 0.0005deg / s. The specific simulation curve is shown in Figure 2-Figure 4 .

[0138] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

[0139] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A high-dynamic online interference estimation method for on-board ring scanning payload, characterized in that: include: Conduct satellite attitude dynamics modeling and rotation load disturbance torque modeling; Obtain the disturbance state equation corresponding to the model; Design state observer; The disturbance torque is estimated online based on the state observer to obtain the estimated value of the disturbance torque.

2. The method for estimating high-dynamic online disturbance of on-board ring-scanning payload according to claim 1, characterized in that: The satellite attitude dynamics modeling is specifically as follows: Considering the satellite center body as a rigid body, the satellite dynamic equation in the x-axis direction considering the load motion disturbance is expressed as: In the formula, ω sx is the satellite angular velocity, and the upper point represents the first-order derivative; J x is the moment of inertia of the star, which is a positive definite symmetric matrix; τ sx is the satellite attitude control torque; τ hx It is the disturbance torque generated on the star when the load moves.

3. The method for estimating high-dynamic online disturbance of on-board ring-scanning payload according to claim 2, characterized in that: The rotating load interference torque modeling, that is, the interference torque τh generated by the load on the star when it moves x Expressed as: t hx =C0+C1 sin(ω h t)+C2cos(ω h t) Among them, ω h is the rotation speed of the sweeping load, t is the motion time, C0, C1, C2 are unknown constants.

4. The method for estimating high-dynamic online disturbance of on-board ring-scanning payload according to claim 3 is characterized by: The interference state equation corresponding to the acquisition model is specifically: Using the disturbance dynamics characteristics, τ hx Taking the second derivative with respect to time, we get Defining state quantities x1=τ hx , x3=J x oh sx , ω hx ω h The component on the x-axis; The interference state equation is obtained Let X = [x1 x2 x3 x4] T , U = τ sx ,get Y=CX in, C = [0 0 1 0] is the state output matrix Y is the measured output.

5. The method for estimating high-dynamic online disturbance of on-board ring-scanning payload according to claim 4, characterized in that: The state observer design is specifically as follows: Assume that the observer gain matrix L = [h1 h2 h3 h4] T , then the characteristic polynomial of the closed-loop system based on the observer is Where s is the Laplace transform variable, I is the 4×4 unit matrix, and C=[0 0 1 0] is the state output matrix; Design p = [abcd], p is the configuration pole, let a=c=-ξω n +ξω n j b=d=-ξω n -ξω n j a1=-out n Among them, j is the imaginary unit, ξ and ω n are observer design parameters, respectively represent the damping ratio and frequency, then the closed-loop characteristic expression is From this we can get h3=-4a1 6. The method for estimating high-dynamic online disturbance of on-board ring-scanning payload according to claim 5, characterized in that: The online estimation of the disturbance torque based on the state observer is specifically as follows: Definition A o =A-LC, B o =[LB] Assume the control period is T c , then the discretized state space matrix of the rotating load disturbance torque model is The discretized state equation is Z x (k)=G x Z x (k-1)+H x U x (k) in, is the measured value of the angular velocity of the star, Z x (k) is the discrete value of the state variable X; The disturbance torque estimate is obtained from this 7. A method for estimating high-dynamic online disturbance of on-board ring-scanning payload according to any one of claims 1 to 6, characterized in that: The estimated value of the disturbance torque is used as the feedforward term of the satellite attitude control torque to achieve payload disturbance suppression.

8. A high-dynamic online disturbance estimation system for onboard ring-scanning payload, characterized by: include: Interference torque modeling module: satellite attitude dynamics modeling and rotation load interference torque modeling; Considering the satellite center body as a rigid body, the satellite dynamic equation in the x-axis direction considering the load motion disturbance is expressed as: In the formula, ω sx is the satellite angular velocity, and the upper point represents the first-order derivative; J x is the moment of inertia of the star, which is a positive definite symmetric matrix; τ sx is the satellite attitude control torque; τ hx It is the disturbance torque generated on the star when the load moves; The rotating load interference torque modeling, that is, the interference torque τ generated by the load on the star when it moves hx Expressed as: t hx =C0+C1sin(ω h t)+C2cos(ω h t) Among them, ω h is the speed of the sweep load, t is the motion time, C0, C1, C2 are unknown constants; Interference state equation acquisition module: obtain the interference state equation corresponding to the model, specifically: Using the disturbance dynamics characteristics, τ hx Taking the second derivative with respect to time, we get Defining state quantities x1=τ hx , x3=J x oh sx , ωh x is the component of ωh on the x-axis; The interference state equation is obtained Let X = [x1 x2 x3 x4] T , U = τ sx ,get Y=CX in, C = [0 0 1 0] is the state output matrix Y is the measured output; Observer design module: design state observer; Disturbance torque online estimation module: online estimation of disturbance torque based on state observer.

9. The high-dynamic online disturbance estimation system for on-board scanning payload according to claim 8, characterized in that: The state observer design is specifically as follows: Assume that the observer gain matrix L = [h1 h2 h3 h4] T , then the characteristic polynomial of the closed-loop system based on the observer is Where s is the Laplace transform variable, I is the 4×4 unit matrix, and C=[0010] is the state output matrix; Design p = [abcd], p is the configuration pole, let a=c=-ξω n +ξω n j b=d=-ξω n -ξω n j a1=-out n Among them, j is the imaginary unit, ξ and ω n are observer design parameters, respectively represent the damping ratio and frequency, then the closed-loop characteristic expression is From this we can get h3=-4a1 10. The high-dynamic online disturbance estimation system for on-board scanning payload according to claim 9, characterized in that: The online estimation of the disturbance torque based on the state observer is specifically as follows: Definition A o =A-LC, B o =[LB] Assume the control period is T c , then the discretized state space matrix of the rotating load disturbance torque model is The discretized state equation is Z x (k)=G x Z x (k-1)+H x U x (k) in, is the measured value of the angular velocity of the star, Z x (k) is the discrete value of the state variable X; The estimated value of the turntable disturbance torque is obtained

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