A fast anti-saturation control method for tethered satellite payload recovery

Abstract

The present invention discloses a rapid anti-saturation control method for tethered satellite payload recovery, the method comprising the following steps: constructing a tethered satellite system dynamics model based on the Lagrangian method; obtaining the stable recovery rate of the tether according to the relationship between the gravity component and the Coriolis force offset; and adjusting the thrust control signal under the above tether stable recovery rate condition. The beneficial effect of the present invention is that the rapid anti-saturation stability control problem in tethered satellite payload recovery is solved by reasonably adjusting the thrust on the payload. During use, the control parameters are easy to adjust, and the maximum convergence time can be set independently, which makes the invention very flexible and practical.

Description

Technical Field

[0001] The invention relates to the field of satellite control technology, and in particular to a fast anti-saturation control method for tethered satellite payload recovery. Background Art

[0002] A tethered satellite usually consists of a main satellite and a sub-satellite (payload), which are connected by a tether, and the release and recovery of the payload are achieved with the help of the tether equipment on the main satellite. During the payload recovery process, under the action of the Coriolis force, the system will continue to swing significantly. This state of motion will have a great negative impact on the stability of the system and may even cause the system to roll over and become unstable. Therefore, the system must be stably controlled and the stable state must be maintained. In addition, the payload recovery cycle is usually short, and the thrust amplitude that can be controlled is limited. The above problem requires that the stable control for the payload recovery process must have good rapidity and anti-saturation. Existing technical means cannot meet the above requirements. Summary of the invention

[0003] In view of the deficiencies in the prior art, the present invention aims to provide a rapid anti-saturation control method for tethered satellite payload recovery. Through this method, the thrusters on the payload are reasonably adjusted to achieve rapid anti-saturation stability control of tethered satellite payload recovery.

[0004] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0005] A fast anti-saturation control method for tethered satellite payload recovery, the method comprising the following steps:

[0006] S1 constructs a tethered satellite system dynamics model based on the Lagrangian method, wherein the modeling coordinate system is the geocentric inertial system Oxy and the moving coordinate system The moving coordinate system takes the parent star M as the origin of the moving coordinate system, e r is a unit vector, and its direction is along the center of the earth pointing toward the main satellite. is a unit vector, perpendicular to e r , taking the main satellite flight direction as the positive direction;

[0007] S2 obtains the stable recovery rate of the tether based on the offset relationship between the gravity component and the Coriolis force;

[0008] S3 adjusts the thrust control signal under the above-mentioned tether stable recovery rate condition.

[0009] It should be noted that the expression of the stable recovery rate of the tether is as follows:

[0010]

[0011] L represents the rope length; Indicates the recovery rate; represents the orbital angular velocity of the main satellite; θ e represents the target swing angle, where the target swing angle θ e Can be set by yourself.

[0012] It should be noted that the method further includes step S3.1, in which, when it is determined that a disturbance error exists, the control input signal is adjusted.

[0013] It should be noted that when it is determined that there is a disturbance error, the actual swing is brought into the sliding surface S to obtain the corrected control signal of the controller; it is determined whether the control signal exceeds the available amplitude F max If it does not exceed, the obtained controller control signal is directly input into the controller for use; otherwise, the difference Δu between the theoretical control input amplitude and the allowable amplitude of the control actuator is calculated, and the auxiliary variable χ and the auxiliary input u a The correction is performed to correct the control signal u and cause the saturation state to end quickly.

[0014] It should be noted that the control input signal expression is as follows:

[0015]

[0016] in,

[0017]

[0018] Among them, T c is the preset convergence time; 0<η≤1 is the control parameter; the expression sig satisfies the rule: sig n (·)=|·| n sign(·); χ is an auxiliary variable; u a is the auxiliary input; the auxiliary variable and the auxiliary input satisfy the following equation:

[0019]

[0020] Where Δu=u b –u,u b To control the amplitude limit function, its specific form is as follows:

[0021]

[0022] In the above formula, F max Indicates the maximum amplitude of thrust; ξ is a small positive quantity and can be set to 0.01; 0 <p<1,q> 0 is the control parameter; S is the sliding surface, and its expression is:

[0023]

[0024] The beneficial effect of the present invention is that by reasonably adjusting the thrust on the payload, the problem of rapid anti-saturation stability control in the recovery of the tethered satellite payload is solved. During use, the control parameters are easy to adjust, and the maximum convergence time can be set independently, which makes the invention very flexible and practical. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the overall steps of the present invention;

[0026] Figure 2 It is a schematic diagram of the structure of the tethered satellite system of the present invention;

[0027] Figure 3 It is a control input variation curve and a swing angle variation convergence curve diagram in the stable control process of the present invention. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] like Figure 1 As shown, the present invention is a fast anti-saturation control method for tethered satellite payload recovery, the method comprising the following steps:

[0030] S1 constructs a tethered satellite system dynamics model based on the Lagrangian method, wherein the modeling coordinate system is the geocentric inertial system Oxy and the moving coordinate system The moving coordinate system takes the parent star M as the origin of the moving coordinate system, e r is a unit vector, and its direction is along the center of the earth pointing toward the main satellite. is a unit vector, perpendicular to e r , taking the main satellite flight direction as the positive direction;

[0031] S2 obtains the stable recovery rate of the tether based on the offset relationship between the gravity component and the Coriolis force;

[0032] S3 adjusts the thrust control signal under the above-mentioned tether stable recovery rate condition.

[0033] It should be noted that the expression of the stable recovery rate of the tether is as follows:

[0034]

[0035] L represents the rope length; Indicates the recovery rate; represents the orbital angular velocity of the main satellite; θ e represents the target swing angle, where the target swing angle θ e Can be set by yourself.

[0036] Furthermore, the present invention also includes step S3.1, when it is determined that a disturbance error exists, adjusting the control input signal.

[0037] Furthermore, when the present invention determines that there is a disturbance error, the actual swing is brought into the sliding surface S to obtain a corrected control signal of the controller; and it is determined whether the control signal exceeds the available amplitude F max If it does not exceed, the obtained controller control signal is directly input into the controller for use; otherwise, the difference Δu between the theoretical control input amplitude and the allowable amplitude of the control actuator is calculated, and the auxiliary variable χ and the auxiliary input u a The correction is performed to correct the control signal u and cause the saturation state to end quickly.

[0038] Furthermore, the control input signal expression of the present invention is as follows:

[0039]

[0040] in,

[0041]

[0042] Among them, T c is the preset convergence time; 0<η≤1 is the control parameter; the expression sig satisfies the rule: sig n (·)=|·| n sign(·); χ is an auxiliary variable; u a is the auxiliary input; the auxiliary variable and the auxiliary input satisfy the following equation:

[0043]

[0044] Where Δu=u b –u,u b To control the amplitude limit function, its specific form is as follows:

[0045]

[0046] In the above formula, F max Indicates the maximum amplitude of thrust; ξ is a small positive quantity and can be set to 0.01; 0 <p<1,q> 0 is the control parameter; S is the sliding surface, and its expression is:

[0047]

[0048] Example

[0049] The technical solution of the present invention is further described below through specific simulation experiments.

[0050] The settings of the initial parameters of the system parameter set are shown in the table:

[0051]

[0052]

[0053] Due to the initial disturbance, the swing angle is greater than the ideal state in the initial 500 seconds. By the 500th second, the load swing angle converges to the target state, as shown in Figure 3 As shown. After that, the swing angle always remains at the target value and the control input returns to 0, which means that the control has been completed within the predetermined time (1000 seconds). In the initial 150 seconds, the control input is in a saturated state, but with the correction of the control method, the saturation state ends at 150 seconds, and the saturation time is very short.

[0054] For those skilled in the art, various corresponding changes can be made according to the above technical solutions and concepts, and all of these changes should be included in the protection scope of the claims of the present invention.

Claims

1. A fast anti-saturation control method for tethered satellite payload recovery, It is characterized in that The method comprises the following steps: S1 constructs a tethered satellite system dynamics model based on the Lagrangian method, where the modeling coordinate system is the geocentric inertial system Oxy and the moving coordinate system The moving coordinate system takes the parent star M as the origin of the moving coordinate system, e r is a unit vector, and its direction is along the center of the earth and points to the main satellite; is a unit vector, perpendicular to e r , taking the main satellite flight direction as the positive direction; S2 obtains the stable recovery rate of the tether based on the offset relationship between the gravity component and the Coriolis force; S3 adjusts the thrust control signal under the above-mentioned tether stable recovery rate condition; The control input signal expression is as follows: in, Among them, T c is the preset convergence time; 0<η≤1 is the control parameter; the expression sig satisfies the rule: sig n (·)=|·| n sign(·); χ is an auxiliary variable; u a is the auxiliary input; the auxiliary variable and the auxiliary input satisfy the following equation: Where Δu=u b –u,u b To control the amplitude limit function, its specific form is as follows: In the above formula, F max Indicates the maximum amplitude of thrust; ξ is a small positive quantity and can be set to 0.01; 0 <p<1,q> 0 is the control parameter; S is the sliding surface, and its expression is:

2. The rapid anti-saturation control method for tethered satellite payload recovery according to claim 1, It is characterized in that The expression of the stable recovery rate of the tether is as follows: L represents the rope length; Indicates the recovery rate; represents the main satellite orbital angular velocity; θ e represents the target swing angle, where the target swing angle θ e Can be set by yourself.

3. The rapid anti-saturation control method for tethered satellite payload recovery according to claim 1, It is characterized in that Also includes: When it is determined that there is a disturbance error, the control input signal is adjusted.

4. The rapid anti-saturation control method for tethered satellite payload recovery according to claim 3, It is characterized in that When it is determined that there is a disturbance error, the actual swing is substituted into the sliding surface S to obtain the controller's corrected control signal; it is determined whether the control signal exceeds the available amplitude F max If it does not exceed, the obtained controller control signal is directly input into the controller for use; otherwise, the difference Δu between the theoretical control input amplitude and the allowable amplitude of the control actuator is calculated, and the auxiliary variable χ and the auxiliary input u a The correction is performed to correct the control signal u and cause the saturation state to end quickly.

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