A spacecraft energy-saving control method based on online identification of actuator degradation

Abstract

The present invention provides a spacecraft energy-saving control method based on online identification of actuator degradation, which belongs to the field of spacecraft control. The method comprises: first, based on the attitude dynamics equation of the spacecraft, establishing an augmented deep-coupled attitude dynamics model of the spacecraft under actuator degradation and flexible vibration interference; second, designing an input excitation disturbance observer based on the augmented deep-coupled attitude dynamics model of the spacecraft, and identifying actuator degradation parameters online based on the output of the input excitation disturbance observer; finally, designing a sliding mode observer to estimate the flexible vibration interference, incorporating the identification value of the actuator degradation parameter into the design of the spacecraft energy-saving control law, and realizing fine compensation for flexible vibration interference and actuator degradation. The present invention has the advantages of high control accuracy and low energy consumption, and can be used for high-precision attitude maneuvering control of flexible spacecraft.

Description

Technical Field

[0001] The present invention belongs to the field of spacecraft control, and in particular relates to a spacecraft energy-saving control method based on online identification of actuator degradation. Background Art

[0002] Space missions such as space / earth observation, precision scientific experiments, and deep space exploration have put forward urgent demands on the attitude control accuracy and energy consumption level of spacecraft. First of all, attitude control accuracy is one of the key factors that determine the success or failure of space missions and restrict mission performance. For example, the attitude pointing accuracy of the Hubble telescope reaches 0.007 arc seconds, achieving high-precision and high-stability attitude pointing control goals. For ultra-precision attitude pointing tasks, any slight attitude jitter will cause problems such as pointing deviation and blurred imaging, making it difficult to complete the established tasks. Secondly, spacecraft have the characteristics of being difficult to maintain in real time and having high autonomy requirements. Therefore, energy is life, and the rate of fuel consumption directly determines the life span of the spacecraft.

[0003] However, spacecraft are faced with multiple sources of interference and uncertainties during their in-orbit operation. First, spacecraft are in orbit for a long time, making it difficult to maintain them in real time, and are affected by harsh environments such as temperature / radiation. Therefore, spacecraft actuators (jet thrusters, flywheels, etc.) are prone to degradation, resulting in problems such as partial efficiency reduction and unknown deviations. As the "muscle" of spacecraft control, the output accuracy of the actuator directly affects the accuracy of satellite attitude control; second, the spacecraft is equipped with flexible components such as large solar panels and deployable antennas. The flexible vibration interference of these components will be transmitted to the rigid platform of the spacecraft, causing the spacecraft attitude jitter. These interferences present composite characteristics, that is, the interference is coupled with the spacecraft's attitude angular velocity, control input and other uncertainties, and has additive, multiplicative and implicit forms. How to finely compensate for the impact of composite interference has become a key factor in improving attitude control accuracy and reducing energy consumption.

[0004] Disturbance compensation control methods (such as active disturbance rejection control, control based on disturbance observer, etc.) have active disturbance estimation and compensation capabilities and are widely used in spacecraft attitude control. The core of disturbance compensation control is disturbance estimation technology. Disturbance observer and extended state observer are both effective means of disturbance estimation. In order to improve the real-time performance of spacecraft disturbance estimation, non-smooth disturbance estimation methods based on sliding mode and other algorithms have also been widely studied. However, these disturbance compensation control methods are often targeted at "single lumped disturbance" systems and are difficult to finely handle complex disturbances.

[0005] For the problem of spacecraft attitude control under composite disturbances, composite anti-disturbance control provides a powerful tool to achieve simultaneous suppression and compensation of disturbances. Under the theoretical framework of composite anti-disturbance control, the strong anti-disturbance control method incorporates the disturbance observer and the extended state observer into a unified framework, which can achieve fine separation of heterogeneous disturbances. However, the existing composite anti-disturbance control for spacecraft often only considers two types of additive disturbances, which is difficult to apply when additive, multiplicative and implicit composite disturbances are mixed; secondly, the existing disturbance estimation methods often characterize the unknown dynamic disturbances in the form of derivative bounded variables. For the multiplicative disturbances caused by actuator degradation, their dynamics are related to the derivative of the control input, and characterizing them as derivative bounded variables is relatively conservative. Therefore, it is urgent to develop fine estimation, identification and compensation methods for additive, multiplicative and implicit composite disturbances, so as to improve the accuracy of spacecraft attitude control and reduce energy consumption. Summary of the invention

[0006] In view of the problem that the existing spacecraft attitude control methods are difficult to accurately handle the actuator degradation and flexible vibration interference, the present invention provides a spacecraft energy-saving control method based on online identification of actuator degradation, establishes an augmented deep-coupled attitude dynamics model of the spacecraft, and fully explores the coupling correlation between additive, multiplicative and implicit composite interference. On this basis, the design of the input excitation interference observer and the identification of actuator degradation parameters are proposed. Finally, the design of the energy-saving control law is completed, providing theoretical and technical support for space missions such as space / earth observation and precision scientific experiments.

[0007] In order to achieve the above object, the present invention adopts the following technical scheme:

[0008] A spacecraft energy-saving control method based on online identification of actuator degradation comprises the following steps:

[0009] Step 1: Based on the attitude dynamics equation of the spacecraft, an augmented deep-coupled attitude dynamics model of the spacecraft under actuator degradation and flexible vibration interference is established;

[0010] Step 2: Design an input excitation disturbance observer based on the spacecraft augmented deep-coupled attitude dynamics model, and identify actuator degradation parameters online based on the output of the input excitation disturbance observer;

[0011] Step 3: Design a sliding mode observer to estimate the flexible vibration disturbance, incorporate the identified values ​​of the actuator degradation parameters into the design of the spacecraft energy-saving control law, and achieve fine compensation for the flexible vibration disturbance and actuator degradation.

[0012] The beneficial effects of the present invention compared with the prior art are:

[0013] The present invention makes full use of the deep coupling relationship of spacecraft composite interference and designs an actuator degradation parameter identification method based on input excitation, which overcomes the difficulty of decoupling and separating additive, multiplicative and implicit composite interference, and further realizes the fine compensation of actuator degradation and flexible vibration interference, which can significantly improve the accuracy of attitude pointing in precision missions such as space / earth observation and reduce control energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a flow chart of a spacecraft energy-saving control method based on online identification of actuator degradation of the present invention;

[0015] Figure 2 It is the time response curve of the flexible vibration disturbance and its estimated value under the input excitation disturbance observer;

[0016] Figure 3 It is the time response curve of actuator degradation and its estimated value under input excitation disturbance observer;

[0017] Figure 4 is the time response curve of the spacecraft angular velocity;

[0018] Figure 5 This is a comparison chart of spacecraft energy consumption indicators under different control laws. DETAILED DESCRIPTION

[0019] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0020] like Figure 1 As shown, a spacecraft energy-saving control method based on online identification of actuator degradation of the present invention comprises the following steps:

[0021] The first step is to establish an augmented deep-coupled attitude dynamics model of spacecraft under actuator degradation and flexible vibration interference based on the attitude dynamics equation of the spacecraft, including:

[0022] The attitude dynamics equation of the spacecraft is:

[0023] ;

[0024] in, is the spacecraft inertia matrix, is the spacecraft angular velocity, , and They represent the roll angular velocity, pitch angular velocity, and yaw angular velocity, respectively. The superscript “T” indicates the transpose operation of the matrix; for The first time derivative of Indicates about The cross product matrix of represents the rigid-flex coupling matrix, represents the actuator output of the spacecraft, represents the environmental disturbance torque; represents the modal displacement of the flexible component, and Respectively The first time derivative of The second-order time derivative of and They represent the damping matrix and the stiffness matrix of the flexible component respectively; represents the energy-saving control law of the spacecraft, represents the actuator efficiency matrix, Indicated by , and The actuator deviation vector composed of ” denotes a diagonal matrix; , and They represent the actuator efficiency factor of the first control channel, the actuator efficiency factor of the second control channel, and the actuator efficiency factor of the third control channel, respectively. , and They represent the actuator deviation of the first control channel, the actuator deviation of the second control channel, and the actuator deviation of the third control channel respectively;

[0025] definition is the flexible vibration interference, Indicates actuator degradation, represents a unit matrix with 3 rows and 3 columns; at this time, the augmented deep coupling attitude dynamics model of the spacecraft under actuator degradation and flexible vibration interference is established as:

[0026] ;

[0027] in, The state variable representing the flexible vibration disturbance; and Respectively The first time derivative of The first time derivative of ; is a known constant matrix, express The inverse matrix of , and is a known coefficient matrix, and its expression is:

[0028] ,

[0029] ,

[0030] ;

[0031] and Represent zero matrices with 3 rows and 3 columns and 3 rows and 1 column respectively; , and Respectively Row 3 Column, Row 1 column and 3 rows The zero matrix of columns, The dimension representing the modal displacement of the flexible component; and Respectively Row 3 Column, OK zero matrix of columns; express OK The identity matrix of columns;

[0032] The second step is to design an input excitation disturbance observer based on the spacecraft augmented deep-coupled attitude dynamics model, and identify the actuator degradation parameters online based on the output of the input excitation disturbance observer, including:

[0033] The whole attitude control process is divided into the excitation identification stage and the maneuver control stage;

[0034] In the excitation identification stage, the input excitation signal is designed to be in the form of piecewise constants, and its expression is:

[0035] ;

[0036] in, represents the input excitation signal, Indicates the time, To stimulate identification of the end time, and All represent given constant values; in the excitation identification stage, let the energy-saving control law of the spacecraft With input excitation signal Equal, the input excitation disturbance observer is obtained as:

[0037] ;

[0038] in, , and Respectively The estimated value of The estimated value and The estimated value of is an auxiliary variable, express The first time derivative of ; is the gain matrix of the input excitation disturbance observer, which is solved by the pole placement method;

[0039] The parameters of actuator degradation include actuator efficiency matrix and actuator deviation vector;

[0040] Based on the output of the input excitation disturbance observer, the identification method of the actuator degradation parameters is proposed as follows:

[0041] ;

[0042] in, Indicates Identification value of the actuator efficiency factor for each control channel, =1,2,3; Indicates The estimated value of the actuator deviation of each control channel, , and are given moments, satisfying and ; express No. elements; express From a given moment To a given time The integral value of express From a given moment At the end of the stimulus identification The integral value of; at this time, the actuator efficiency matrix is ​​obtained Identification value and the actuator deviation vector Identification value ;

[0043] The third step is to design a sliding mode observer to estimate the flexible vibration disturbance, incorporate the identification value of the actuator degradation parameter into the design of the spacecraft energy-saving control law, and realize the fine compensation of the flexible vibration disturbance and actuator degradation, including:

[0044] After the excitation identification phase, the maneuvering control phase begins. In order to achieve a precise and rapid estimation of the flexible vibration disturbance in the maneuvering control phase, the sliding mode observer is designed as follows:

[0045] ;

[0046] in, represents the spacecraft angular velocity The estimated value of express The first time derivative of and are all positive observer gains, Represents a given constant, the symbol " ” represents the Euclidean norm of the vector; the identification value of the actuator efficiency matrix and the identified value of the actuator deviation vector Incorporating this into the design of attitude control, the energy-saving control law of the spacecraft is obtained as follows:

[0047] ;

[0048] in, express The inverse matrix of For a given desired angular velocity, and is a positive control law gain; the designed energy-saving control law can realize fine compensation for flexible vibration interference and actuator degradation, thereby achieving high-precision and low-energy consumption control performance.

[0049] Example:

[0050] This embodiment takes the spacecraft attitude control system as an example, and the parameters of the spacecraft are shown in Table 1:

[0051] Table 1 Spacecraft parameters

[0052]

[0053] The steps of this embodiment include:

[0054] The first step is to establish an augmented deep-coupled attitude dynamics model of spacecraft under actuator degradation and flexible vibration interference based on the attitude dynamics equation of the spacecraft.

[0055] The second step is to design an input excitation disturbance observer based on the augmented deep-coupled attitude dynamics model of the spacecraft, and identify the actuator degradation parameters online based on the output of the input excitation disturbance observer.

[0056] In this embodiment, the excitation identification end time In this embodiment, the value is 30s, and the given constant and In this embodiment, the value is 0.02.

[0057] The gain matrix of the input excitation disturbance observer is , solved by the pole placement method, in this embodiment, the value is:

[0058] ;

[0059] Given a moment and In this embodiment, the values ​​are 10s and 25s respectively.

[0060] In order to verify the effectiveness of the designed input excitation disturbance observer, Figure 2 The time response curve of the flexible vibration disturbance and its estimated value under the input excitation disturbance observer is given; Figure 3 The time response curves of actuator degradation and its estimated value under input excitation disturbance observer are given. Figure 2 and Figure 3 It can be seen that the designed input excitation disturbance observer can realize the accurate estimation of flexible vibration disturbance and actuator degradation; further, based on the output of the input excitation disturbance observer, Table 2 gives the identification results of the actuator degradation parameter identification method; it can be seen from Table 2 that the identification values ​​of the actuator efficiency factors of the three control channels are 0.497, 0.675 and 0.710, respectively, and the identification values ​​of the actuator deviations of the three control channels are 0.0104, 0.0075 and -0.0102, respectively, and the identification accuracy of the six parameters is better than 93%.

[0061] Table 2 Actuator degradation parameter identification values

[0062]

[0063] The third step is to design a sliding mode observer to estimate the flexible vibration interference, incorporate the identification values ​​of the actuator degradation parameters into the design of the spacecraft energy-saving control law, and achieve fine compensation for the flexible vibration interference and actuator degradation.

[0064] Positive observer gain and In this embodiment, the value is 1; the given constant In this embodiment, the value is 0.001; given the desired angular velocity In this embodiment, the value is 0 rad / s, and the positive control law gain and In this embodiment, the values ​​are 0.2 and 0.1 respectively.

[0065] In order to verify the effectiveness of the designed energy-saving control law, Figure 4 The time response curve of the spacecraft angular velocity is given; Figure 4 It can be seen that after the excitation identification phase (0s to 30s) is completed, the rolling angular velocity of the spacecraft in the maneuvering control phase (30s to 60s) is , pitch angular velocity and yaw rate All of them can converge to zero quickly, and the convergence time is less than 10s, which verifies the effectiveness of the designed method. At the same time, in order to verify the energy consumption of the control method, Figure 5 A comparison of spacecraft energy consumption indicators under different control laws is given. Figure 5 It can be seen that compared with the traditional sliding mode control law, the designed energy-saving control law reduces the energy consumption by 37.5%, which fully verifies the effectiveness of the designed energy-saving control law.

[0066] The contents not described in detail in the specification of the present invention belong to the prior art known to the professional and technical personnel in this field.

Claims

1. A spacecraft energy-saving control method based on online identification of actuator degradation, characterized in that: The following steps are involved: Step 1: Based on the attitude dynamics equation of the spacecraft, establish the spacecraft augmented deep coupling attitude dynamics model under actuator degradation and flexible vibration interference, including: Based on the attitude dynamics equation of the spacecraft, the augmented deep coupling attitude dynamics model of the spacecraft under the interference of actuator degradation and flexible vibration is established as follows: ； in, is the spacecraft angular velocity, express The first time derivative of Indicates about The cross product matrix of represents the state variable of the flexible vibration disturbance, Indicates actuator degradation; and Respectively The first time derivative of The first time derivative of ; is a known constant matrix, is the spacecraft inertia matrix, express The inverse matrix of represents the environmental disturbance torque, represents the energy-saving control law of the spacecraft, , and is a known coefficient matrix; and They represent a zero matrix with 3 rows and 3 columns and a zero matrix with 3 rows and 1 column respectively; , and Respectively A zero matrix with 3 rows and columns, Zero matrix with 1 row and 3 columns The zero matrix of columns, The dimension representing the modal displacement of the flexible component; Step 2: Design an input excitation disturbance observer based on the spacecraft augmented deep-coupled attitude dynamics model, and identify actuator degradation parameters online based on the output of the input excitation disturbance observer, including: The control process is divided into the excitation identification stage and the maneuver control stage; In the excitation identification stage, the input excitation signal is designed to be in the form of piecewise constants, and the energy-saving control law of the spacecraft is made equal to the input excitation signal, and the input excitation disturbance observer is obtained as: ； in, represents the flexible vibration disturbance, , and Respectively represent the state variables of flexible vibration disturbance Estimated value of flexible vibration disturbance Estimation of and actuator degradation The estimated value of is an auxiliary variable, express The first time derivative of ; is the input excitation signal, is the gain matrix of the input excitation disturbance observer, which is solved by the pole placement method; The actuator degradation parameters include the actuator efficiency matrix and the actuator deviation vector; Based on the output of the input excitation disturbance observer, the identification method of the actuator degradation parameters is proposed as follows: ； in, and All represent given constant values. Indicates Identification value of the actuator efficiency factor for each control channel, =1,2,3; Indicates The estimated value of the actuator deviation of each control channel, , and For a given moment, Identify the end moment for motivation; Indicates actuator degradation Estimated value of No. elements; express From a given moment To a given time The integral value of express From a given moment At the end of the stimulus identification The integral value of the actuator efficiency matrix is ​​obtained. and the identified value of the actuator deviation vector ,symbol" " denotes a diagonal matrix, the superscript "T" denotes the transpose operation of the matrix, and t denotes time; Step 3: Design a sliding mode observer to estimate the flexible vibration disturbance, incorporate the identified values ​​of the actuator degradation parameters into the design of the spacecraft energy-saving control law, and achieve fine compensation for the flexible vibration disturbance and actuator degradation.

2. The spacecraft energy-saving control method based on online identification of actuator degradation according to claim 1 is characterized in that: The step 3 comprises: After the excitation identification phase, the maneuvering control phase begins. In order to achieve a precise and rapid estimation of the flexible vibration disturbance in the maneuvering control phase, the sliding mode observer is designed as follows: ； in, represents the spacecraft angular velocity The estimated value of express The first time derivative of and are all positive observer gains, Represents a given constant, symbol " ” represents the Euclidean norm of the vector; the identification value of the actuator efficiency matrix and the identified value of the actuator deviation vector Incorporated into the design of attitude control, the energy-saving control law of the spacecraft is obtained for: ； in, Represents the identified value of the actuator efficiency matrix The inverse matrix of For a given desired angular velocity, and is a positive control law gain.

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