An on-board high-dynamic online interference estimation method and system for ring-scan loads

Abstract

The application relates to a high-dynamic on-line interference estimation method for a ring-scan load on a satellite. The method designs an on-line high-dynamic interference prediction method based on an observer aiming at the periodic characteristics of the interference, and realizes high-precision estimation of fast-changing interference. The high-precision estimated value of the interference torque is used as a feedforward item of the satellite attitude control torque, so that the load interference is effectively inhibited, and the pointing accuracy and stability of the satellite are ensured.

Description

TECHNICAL FIELD

[0001] The application relates to a kind of on-orbit interference estimation method and system of high dynamic of ring scanning load on satellite, belong to spacecraft control technical field. BACKGROUND

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

[0003] High-speed rotating loads will cause interference to the satellite. If no interference compensation is performed, the satellite attitude stability and pointing accuracy will be reduced, affecting the scientific mission of the satellite. In severe cases, this interference can even excite the vibration of flexible accessories (such as solar panels), causing the attitude of the satellite to oscillate.

[0004] Currently, the commonly used interference estimation method on satellite mainly estimates slowly varying interference and is no longer applicable in the case of rapid interference changes. SUMMARY

[0005] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art and provide an on-orbit high-dynamic interference estimation method for ring scanning loads on satellite. The high-precision estimated value of the interference torque is used as the feedforward term of the satellite attitude control torque to effectively suppress the load interference and ensure the pointing accuracy and stability of the satellite.

[0006] The technical solution adopted by the present application is as follows:

[0007] An on-orbit high-dynamic interference estimation method for ring scanning loads on satellite, comprising the following steps:

[0008] (1) Perform satellite attitude dynamics modeling and rotating load interference torque modeling;

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

[0010] (3) Design a state observer;

[0011] (4) Perform online estimation of the interference torque based on the state observer to obtain the estimated value of the interference torque.

[0012] (5) Use the estimated value of the interference torque as the feedforward term of the satellite attitude control torque to achieve load interference suppression.

[0013] Further, the satellite attitude dynamics modeling is performed as follows:

[0014] The satellite center body is regarded as a rigid body, and the satellite x-axis direction dynamics equation considering the load motion disturbance is expressed as:

[0015]

[0016] In the formula, ω sx is the satellite angular velocity, the upper point represents the first derivative; J x is the star body rotation inertia, which is a positive definite symmetric matrix; τ sx is the satellite attitude control torque; τ hx is the interference torque generated by the star body when the load moves.

[0017] Further, the rotating load interference torque modeling, that is, the interference torque τ hx generated by the star body when the load moves is expressed as:

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

[0019] Wherein, ω h is the rotating speed of the ring scanning load, t is the motion time, C0, C1, C2 are unknown constants.

[0020] Further, the interference state equation corresponding to the model is obtained, which is specifically:

[0021] By using the interference dynamics characteristics, τ hx is derived twice with respect to time, and

[0022]

[0023] The state quantity is defined as

[0024] x1=τ hx , x3=J x ω sx ,

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

[0026] The interference state equation is obtained

[0027]

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

[0029]

[0030] Y = CX

[0031] wherein,

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

[0033] Y is the measurement output.

[0034] Further, the state observer is designed, in particular:

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

[0036]

[0037] wherein, s is the Laplace transform variable, I is a 4x4 unit matrix, C = [0 1 0] is the state output matrix;

[0038] Design p = [a b c d], 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] wherein, j is the imaginary unit, ξ and ω n are observer design parameters, respectively representing damping ratio and frequency, then the closed-loop characteristic expression is

[0043]

[0044] Thus, we can get

[0045] h3 = -4a1

[0046]

[0047]

[0048] Further, the disturbance torque is estimated online based on the state observer, in particular:

[0049] Define A o = A - LC, B o = [L B]

[0050] Assuming the control period is T c The discretized state space matrix of the rotational 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] Wherein, is the measured value of the angular velocity of the star body, Z x (k) is the discrete quantity of the state variable X;

[0055] Thus, the disturbance torque estimation value is

[0056]

[0057] On the other hand, the application also provides a high dynamic on-line disturbance estimation system for a ring-scan load on a satellite, comprising:

[0058] A disturbance torque modeling module: satellite attitude dynamics modeling and rotational load disturbance torque modeling; the satellite central body is regarded as a rigid body, and the satellite x-axis direction dynamics equation considering the load motion disturbance is expressed as:

[0059]

[0060] In the formula, ω sx is the angular velocity of the satellite, and the upper point represents the first derivative; J x is the moment of inertia of the star body, 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 motion on the star body;

[0061] The rotational load disturbance torque modeling, i.e. the disturbance torque τ hx generated by the load motion on the star body, is expressed as:

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

[0063] Wherein, ω h is the rotating speed of the ring-scan load, t is the motion time, and C0, C1 and C2 are unknown constants;

[0064] An interference state equation obtaining module: obtaining an interference state equation corresponding to the model, specifically:

[0065] By using the interference dynamics characteristics, τ hx Secondly, the time is derived twice to obtain

[0066]

[0067] Define the state variable

[0068] x1=tau hx , x3=J x omega sx ,

[0069] omega_h x is the component of omega_h in the x-axis;

[0070] Obtain the interference state equation

[0071]

[0072] Let X=[x1 x2 x3 x4] T , U=tau sx , obtain

[0073]

[0074] Y=CX

[0075] Wherein,

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

[0077] Y is the measurement output;

[0078] An observer design module: state observer design is carried out;

[0079] An interference torque online estimation module: based on the state observer, the interference torque online estimation is carried out.

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

[0081] (1) The method of the present application estimates the interference torque of the rotating load interference of the fixed period, fully excavates the load interference dynamics characteristics, and takes the high-precision estimated value of the interference torque as the feedforward item of the satellite attitude control torque, effectively realizes the load interference suppression, and ensures the pointing accuracy and stability of the satellite.

[0082] (2) The method of this invention is applicable to the high-precision and high-stability control of spacecraft equipped with ring-scan payloads. This method constructs a state estimation method based on the observer for high-precision disturbance estimation and uses a controller feedforward compensation design for payload suppression. Using the improved control strategy, the high-precision and high-stability pointing requirements of the tethered camera can be effectively met. The entire algorithm design is simple, and the parameter debugging workload is small.

[0083] (3) This invention proposes a new solution to the problem of suppressing the interference caused by rotating loads in satellite attitude control. It does not require additional data input, is simple to calculate, and can be adapted to a large class of satellite systems with non-cooperative moving target tracking requirements. It has strong engineering practicality. Attached Figure Description

[0084] Figure 1 This is a flowchart of the method of the present invention;

[0085] Figure 2 This is a schematic diagram showing the estimated and actual values ​​(Nm) of the disturbance torque;

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

[0087] Figure 4 This is a schematic diagram of satellite stability (deg / s). Detailed Implementation

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

[0089] like Figure 1 As shown, this invention relates to a method for estimating high dynamic online interference of on-board ring scan payloads, comprising the following steps:

[0090] Step 1: Perform satellite attitude dynamics modeling and rotational load disturbance torque modeling;

[0091] Treating the satellite's central body as a rigid body, the satellite's dynamic equations along the x-axis, considering load motion disturbances, can be simplified as follows:

[0092]

[0093] In the formula, ω sx J represents the satellite's angular velocity, with the point above indicating the first derivative; x Let τ be the moment of inertia of the celestial body, and let τ be a positive definite symmetric matrix sx τ is the attitude control torque for the satellite. hx The disturbance torque exerted on the celestial body by the load during its motion is modeled as follows:

[0094] τ hx= C0 + C1 sin(ω h t) + C2 cos(ω h t)

[0095] where ω h is the rotating speed of the ring scan load, t is the motion time, C0, C1, C2 are unknown constants.

[0096] Step two, obtain the interference state equation corresponding to the model;

[0097] Using the interference dynamics characteristics, τ hx is the second derivative with respect to time, and

[0098]

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

[0100] Define the state variable

[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 , we can get

[0105]

[0106] Y = CX

[0107] where,

[0108]

[0109] C =

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

[0110] Step three, design the state observer.

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

[0112]

[0113] where s is the Laplace transform variable, I is a 4x4 identity matrix, C=[0 0 1 0] is the state output matrix;

[0114] Design p=[a b c d], 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] where j is the imaginary unit, ξ and ω n are observer design parameters, representing damping ratio and frequency respectively, then the closed-loop characteristic expression is

[0119]

[0120] Thus, we can get

[0121] h3=-4a1

[0122]

[0123] Step four, disturbance torque online estimation based on state observer.

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

[0125] Define

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

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

[0128]

[0129] Therefore, the discrete state equation is

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

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

[0132] The estimated value of the interference torque of the rotating platform is obtained

[0133]

[0134] The estimated value of the interference torque is used as a feedforward item of the satellite attitude control torque to realize the load interference suppression.

[0135] The application will be further described in combination with the embodiments.

[0136] Embodiment:

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

[0138] The contents not described in detail in the specification of the application are the known technology of those skilled in the art.

[0139] Although the application has been disclosed with the above preferred embodiments, it is not intended to limit the application, and any person skilled in the art can make possible changes and modifications to the technical solutions of the application by using the disclosed methods and technical contents without departing from the spirit and scope of the application. Therefore, any simple modification, equivalent change and modification made on the basis of the technical essence of the application to the above embodiments, which does not depart from the technical solutions of the application, belongs to the protection scope of the technical solutions of the application.

Claims

1. A method for estimating high dynamic online interference of on-board ring scan payloads, characterized in that, include: Perform satellite attitude dynamics modeling and rotational load disturbance torque modeling; Obtain the disturbance state equation corresponding to the model; Design a state observer; The disturbance torque is estimated online based on the state observer, and the estimated value of the disturbance torque is obtained. The satellite attitude dynamics modeling is specifically performed as follows: Treating the satellite's central body as a rigid body, the satellite's dynamic equations along the x-axis, considering load motion disturbances, are expressed as: In the formula, ω sx J represents the satellite's angular velocity, with the point above indicating the first derivative; x Let τ be the moment of inertia of the celestial body, and let τ be a positive definite symmetric matrix. sx For satellite attitude control torque; τ hx This refers to the disturbance torque generated on the celestial body by the load during its movement; The modeling of the rotating load disturbance torque, namely the disturbance torque τ generated on the celestial body by the load during its motion. hx Expressed as: t hx =C0+C1sin(ω h t)+C2cos(ω h t) Where, ω h Let t be the rotational speed of the ring sweep load, t be the motion time, and C0, C1, C2 be unknown constants; The specific method for obtaining the disturbance state equation corresponding to the model is as follows: Utilizing the dynamic characteristics of disturbance, τ hx Taking the second derivative with respect to time, we get Define state variables ω hx For ω h Components on the x-axis; The disturbance state equation is obtained. Let X = [x1 x2 x3 x4] T U = τ sx ,get Y = CX in, C = [0 010] is the state output matrix. Y is the measurement output.

2. The method for estimating high dynamic online interference of on-board ring scan payload according to claim 1, characterized in that: The design of the state observer is specifically as follows: Assume 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 a 4×4 identity matrix, and C = [0010] is the state output matrix; Design p = [abcd], where p is the placement pole, let a=c=-ξω n +ξω n j b=d=-ξω n -ξω n j a1=-out n Where j is the imaginary unit, ξ and ω n Let the parameters for the observer be denoted by the damping ratio and frequency, respectively. Then the closed-loop characteristic expression is: From this, we can obtain h3=-4a1 3. The method for estimating high dynamic online interference of on-board ring scan payload according to claim 2, characterized in that: The online estimation of disturbance torque based on the state observer is specifically as follows: Define 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 then: Z x (k)=G x Z x (k-1)+H x U x (k) in, Z is the measured value of the angular velocity of the celestial body. x (k) represents the discrete quantity of the state variable X; This yields the estimated value of the disturbance torque.

4. A method for estimating high dynamic online interference of on-board ring scan payload according to any one of claims 1-3, characterized in that: The estimated disturbance torque is used as a feedforward term for the satellite attitude control torque to achieve load disturbance suppression.

5. A high-dynamic online interference estimation system for on-board ring scan payloads, characterized in that: include: Disturbance torque modeling module: performs satellite attitude dynamics modeling and rotational load disturbance torque modeling; Treating the satellite's central body as a rigid body, the satellite's dynamic equations along the x-axis, considering load motion disturbances, are expressed as: In the formula, ω sx J represents the satellite's angular velocity, with the point above indicating the first derivative; x Let τ be the moment of inertia of the celestial body, and let τ be a positive definite symmetric matrix. sx For satellite attitude control torque; τ hx This refers to the disturbance torque generated on the celestial body by the load during its movement; The modeling of the rotating load disturbance torque, namely the disturbance torque τ generated on the celestial body by the load during its motion. hx Expressed as: t hx =C0+C1sin(ω h t)+C2cos(ω h t) Where, ω h Let t be the rotational speed of the ring sweep load, t be the motion time, and C0, C1, C2 be unknown constants; Disturbance State Equation Acquisition Module: Acquires the disturbance state equations corresponding to the model, specifically: Utilizing the dynamic characteristics of disturbance, τ hx Taking the second derivative with respect to time, we get Define state variables ω hx For ω h Components on the x-axis; The disturbance 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 measurement output; Observer design module: Design the state observer; Online estimation module for disturbance torque: performs online estimation of disturbance torque based on state observer.

6. The on-board ring scan payload high dynamic online interference estimation system according to claim 5, characterized in that: The design of the state observer is specifically as follows: Assume 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 a 4×4 identity matrix, and C = [0010] is the state output matrix; Design p = [abcd], where p is the placement pole, let a=c=-ξω n +ξω n j b=d=-ξω n -ξω n j a1=-out n Where j is the imaginary unit, ξ and ω n Let the parameters for the observer be denoted by the damping ratio and frequency, respectively. Then the closed-loop characteristic expression is: From this, we can obtain h3=-4a1 7. The on-board ring scan payload high dynamic online interference estimation system according to claim 6, characterized in that: The online estimation of disturbance torque based on the state observer is specifically as follows: Define 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 then: Z x (k)=G x Z x (k-1)+H x U x (k) in, Z is the measured value of the angular velocity of the celestial body. x (k) represents the discrete quantity of the state variable X; This yields the estimated value of the turntable disturbance torque.

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