A relative motion control planning method considering terminal velocity constraint

Abstract

A relative motion control planning method considering terminal velocity constraint comprises the following steps: step one, determining the feasible interval range of control planning transfer time; step two, according to the feasible interval range of control planning transfer time, determining the traversal time interval to obtain the trial point of iterative predictive control planning calculation; step three, according to the obtained trial point, using the method of iterative predictive control planning to traverse all results in the feasible interval range to obtain the terminal state after relative motion control at each trial point; step four, in the series of terminal states obtained in step three, according to the terminal optimization condition, determining one group as the optimal solution. The present application optimizes the optimal control planning position meeting the terminal velocity constraint condition through the iterative predictive comparison in a certain feasible control planning time interval, and calculates the corresponding control planning quantity, which can be applied to various spacecraft on-orbit space rendezvous and docking and other task scenarios.

Description

Technical Field

[0001] This invention relates to a relative motion control planning method that considers terminal velocity constraints, belonging to the field of spacecraft rendezvous and docking technology. Background Technology

[0002] Generally, the relative motion of close-keep point transfers of spacecraft is calculated using the CW method for control planning. This method can ensure the accuracy of control planning for the relative position of the terminals, but it does not constrain the relative velocity of the terminals. For multi-stage rendezvous and docking missions that need to continuously complete close-keep point transfers, the previous rendezvous state will be transmitted to the subsequent rendezvous mission through the terminal velocity. If the terminal velocity is not constrained, it will bring certain uncertainties to the subsequent pulse size and orbit control attitude adjustment. Therefore, after relaxing a certain time constraint, the constraint of the critical terminal velocity can be achieved by optimizing the rendezvous and transfer time, thereby improving the feasibility of continuous close-keep point transfer rendezvous missions. Summary of the Invention

[0003] The purpose of this invention is to propose a relative motion control planning method that considers terminal velocity constraints for rendezvous tasks. This method optimizes the optimal control planning position that meets the terminal velocity constraints by iteratively predicting and comparing within a certain feasible control planning time interval, and calculates the corresponding control planning quantities.

[0004] The technical solution adopted in this invention is as follows: A relative motion control planning method considering terminal velocity constraints includes the following steps: Step 1: Determine the feasible time range for the control plan transfer; Step 2: Based on the feasible range of the control plan transition time, determine the traversal time interval to obtain the trial calculation points for the iterative predictive control plan calculation; Step 3: Based on the obtained trial points, use the iterative predictive control programming method to traverse all results within the feasible interval and obtain the terminal state after relative motion control at each trial point; Step four: Among the series of terminal states obtained in step three, determine one set as the optimal solution based on the terminal optimization conditions.

[0005] Furthermore, step one, determining the feasible time range for the control planning transition, specifically involves: The feasible time interval for controlling the transition includes the minimum time t. min and maximum time t max Where, the minimum time t minIt is necessary to consider the current navigation status of the spacecraft and the preparation time required to perform orbital control maneuvers. After the spacecraft establishes stable relative navigation and is ready to perform orbital control, if the current time is t, then t min >t; Maximum time t max Related to the overall rendezvous and docking mission, if the mission's allowed transfer time is t task , then t max <t task .

[0006] Furthermore, step two, determining the traversal time interval, specifically involves: Based on the computing power of the onboard computer and the actual mission requirements, the feasible range of the control planning transfer time is evenly divided into N+1 iterative control planning calculation time points. That is, t0=t min t1=t min +(t max -t min ) / N、t2=t min +2 (t max -t min ) / N、……、t N =t max The calculation time point of the iterative control planning is the trial calculation point.

[0007] Furthermore, step three employs an iterative predictive control programming method to traverse all results within the feasible transition time interval of the control programming, specifically as follows: (3.1) Before traversing, latch the traversal input parameters based on the relative navigation results, i.e., the current relative distance between the two spacecraft. Relative velocity The orbital angular velocity of the spacecraft relative to the origin of the navigation coordinate system. The above input parameters remain unchanged during a complete traversal calculation; (3.2) Based on each trial point determined in step two , First, the relative position and velocity are extrapolated without power to the trial point using the relative motion equations to obtain the relative position of the control planning position. and relative velocity Using the relative position and relative velocity obtained by this extrapolation, combined with the target position of the control plan, and remaining transfer time Perform relative motion control planning calculations to obtain the velocity increment. This velocity increment is added to the relative velocity at the trial time. The relative velocity obtained after orbital control is applied: , Combined with the relative positions at the trial calculation time The terminal time is obtained by performing unpowered extrapolation. relative position and relative velocity ; (3.3) Following the method of step (3.2), calculate N+1 times, traverse all trial points, and obtain N+1 results, which are the terminal states after relative motion control.

[0008] Furthermore, in step four, among the obtained series of terminal states, one set is determined as the optimal solution based on the terminal optimization conditions, specifically as follows: Assume the optimization objective of the relative velocity in the z-direction is Then, the difference between the terminal state of all trial points and the optimization target is obtained. Take all The minimum value in the set is taken as the optimization result, that is, the control program result that is closest to the terminal optimization objective.

[0009] Secondly, the present invention also proposes a relative motion control planning system considering terminal velocity constraints, comprising: Scope determination module: Determines the feasible time range for control planning transition; Trial point determination module: Based on the feasible range of the control plan transition time, determine the traversal time interval to obtain the trial points for iterative predictive control plan calculation; Terminal state determination module: Based on the obtained trial points, the iterative predictive control programming method is used to traverse all results within the feasible interval to obtain the terminal state after relative motion control at each trial point; Optimal solution determination module: From a series of obtained terminal states, it determines one set as the optimal solution based on the terminal optimization conditions.

[0010] The advantages of this invention compared to the prior art are: (1) Currently, due to the relatively ample transfer time, the relative positions of transfer points and the transfer time of rendezvous pairs can be arranged to set the terminal conditions to a better state that is more conducive to engineering implementation. However, in the task range where the transfer time is relatively tight, it is impossible to guarantee a good terminal state. This invention analyzes the terminal state of the control plan by relaxing the transfer time constraints, thereby improving the control capability of the terminal state, especially the relative velocity state. (2) Starting from optimization methods and simulation data, this invention creatively introduces a predictive control planning method based on trajectory prediction for mechanism analysis, and cleverly uses optimization strategies to improve the constraints on terminal state based on a clear and concise mechanism. (3) The present invention proposes a relative motion control planning method that considers terminal velocity constraints. The scheme is theoretically analyzed, the process mechanism is expressed by mathematical methods, and the constraints of limited computing power of spaceborne computers under actual engineering conditions are considered. A discretization processing method is proposed, which is easy to implement in engineering. Attached Figure Description

[0011] Figure 1 This is a flowchart of a relative motion control planning method considering terminal velocity constraints according to the present invention. Detailed Implementation

[0012] The present invention will be further described below with reference to the embodiments.

[0013] To address the issue that current rendezvous pair approach distance control planning methods, while allowing for relatively ample transfer time and enabling the arrangement of relative transfer point positions and transfer times to set optimal terminal conditions for engineering implementation, cannot guarantee a satisfactory terminal state within tight timeframes, this invention proposes a relative motion control planning method that considers terminal velocity constraints. Figure 1 As shown, the steps are as follows: Step 1: Determine the feasible time range for the control plan transition.

[0014] The feasible time interval for controlling the transition includes the minimum time t. min and maximum time t max Where, the minimum time t min It is necessary to consider the current navigation status of the spacecraft and the preparation time required to perform orbital control maneuvers. After the spacecraft establishes stable relative navigation and is ready to perform orbital control, if the current time is t, then t min >t; Maximum time t max Related to the overall rendezvous and docking mission, if the mission's allowed transfer time is t task , then t max <t task .

[0015] Step 2: Based on the feasible range of the control plan transition time, determine the traversal time interval to obtain the trial calculation points for the iterative predictive control plan calculation.

[0016] Based on the computing power of the onboard computer and the actual mission requirements, the feasible range of the control planning transfer time is evenly divided into N+1 iterative control planning calculation time points. That is, t0=t min t1=t min +(t max -t min ) / N、t2=t min +2 (t max -t min ) / N、……、t N =t max The calculation time point of the iterative control planning is the trial calculation point.

[0017] Step 3: Based on the obtained trial points, use the iterative predictive control programming method to traverse all results within the feasible interval and obtain the terminal state after relative motion control at each trial point.

[0018] (3.1) Before traversing, latch the traversal input parameters based on the relative navigation results, i.e., the current relative distance between the two spacecraft. Relative velocity The orbital angular velocity of the spacecraft relative to the origin of the navigation coordinate system. The above input parameters remain unchanged during a complete traversal calculation.

[0019] (3.2) Based on each trial point determined in step two , First, the relative position and velocity are extrapolated without power to the trial point using the relative motion equations to obtain the relative position of the control planning position. and relative velocity Using the relative position and relative velocity obtained by this extrapolation, combined with the target position of the control plan, and remaining transfer time Perform relative motion control planning calculations to obtain the velocity increment. This velocity increment is added to the relative velocity at the trial time. The relative velocity obtained after orbital control is applied: , Combined with the relative positions at the trial calculation time The terminal time is obtained by performing unpowered extrapolation. relative position and relative velocity ; (3.3) Following the method of step (3.2), calculate N+1 times, traverse all trial points, and obtain N+1 results, which are the terminal states after relative motion control.

[0020] Step 4: Among the series of terminal states obtained, determine one set as the optimal solution based on the terminal optimization conditions.

[0021] Since the optimization process only involves one degree of freedom—time—the final state can only be determined by the relative velocities along the three axes. One of the following is optimized. Here, we take optimizing the relative velocity in the z-direction as an example, assuming the optimization objective for the relative velocity in the z-direction is... Then, the difference between the terminal state of all trial points and the optimization target can be obtained. Take all The minimum value in the x and y directions is taken as the optimization result, that is, the control program result that is closest to the terminal optimization objective. The same applies to the x and y directions.

[0022] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A relative motion control planning method considering terminal velocity constraints, characterized in that, include: Step 1: Determine the feasible time range for the control plan transfer; Step 2: Based on the feasible range of the control plan transition time, determine the traversal time interval to obtain the trial calculation points for the iterative predictive control plan calculation; Step 3: Based on the obtained trial points, use the iterative predictive control programming method to traverse all results within the feasible interval and obtain the terminal state after relative motion control at each trial point; Step four: Among the series of terminal states obtained in step three, determine one set as the optimal solution based on the terminal optimization conditions.

2. The relative motion control planning method considering terminal velocity constraints according to claim 1, characterized in that: Step one, determining the feasible time range for the control planning transition, specifically involves: The feasible time interval for controlling the transition includes the minimum time t. min and maximum time t max Where, the minimum time t min It is necessary to consider the current navigation status of the spacecraft and the preparation time required to perform orbital control maneuvers. After the spacecraft establishes stable relative navigation and is ready to perform orbital control, if the current time is t, then t min >t; Maximum time t max Related to the overall rendezvous and docking mission, if the mission's allowed transfer time is t task , then t max <t task .

3. The relative motion control planning method considering terminal velocity constraints according to claim 2, characterized in that: Step two, determining the traversal time interval, specifically involves: Based on the computing power of the onboard computer and the actual mission requirements, the feasible range of the control planning transfer time is evenly divided into N+1 iterative control planning calculation time points. That is, t0=t min t1=t min +(t max -t min ) / N、t2=t min +2 (t max -t min ) / N、……、t N =t max The calculation time point of the iterative control planning is the trial calculation point.

4. The relative motion control planning method considering terminal velocity constraints according to claim 3, characterized in that: Step three employs an iterative predictive control programming method to traverse all results within the feasible transition time interval of the control programming, specifically as follows: (3.1) Before traversing, latch the traversal input parameters based on the relative navigation results, i.e., the current relative distance between the two spacecraft. Relative velocity The orbital angular velocity of the spacecraft relative to the origin of the navigation coordinate system. The above input parameters remain unchanged during a complete traversal calculation; (3.2) Based on each trial point determined in step two , First, the relative position and velocity are extrapolated without power to the trial point using the relative motion equations to obtain the relative position of the control planning position. and relative velocity Using the relative position and relative velocity obtained by this extrapolation, combined with the target position of the control plan, and remaining transfer time Perform relative motion control planning calculations to obtain the velocity increment. This velocity increment is added to the relative velocity at the trial time. The relative velocity obtained after orbital control is applied: ， Combined with the relative positions at the trial calculation time The terminal time is obtained by performing unpowered extrapolation. relative position and relative velocity ; (3.3) Following the method of step (3.2), calculate N+1 times, traverse all trial points, and obtain N+1 results, which are the terminal states after relative motion control.

5. The relative motion control planning method considering terminal velocity constraints according to claim 4, characterized in that: Step four involves determining one set of terminal states from the obtained series of terminal states as the optimal solution based on the terminal optimization conditions. Specifically: Assume the optimization objective of the relative velocity in the z-direction is Then, the difference between the terminal state of all trial points and the optimization target is obtained. Take all The minimum value in the set is taken as the optimization result, that is, the control program result that is closest to the terminal optimization objective.

6. A relative motion control planning system considering terminal velocity constraints, characterized in that, include: Scope determination module: Determines the feasible time range for control planning transition; Trial point determination module: Based on the feasible range of the control plan transition time, determine the traversal time interval to obtain the trial points for iterative predictive control plan calculation; Terminal state determination module: Based on the obtained trial points, the iterative predictive control programming method is used to traverse all results within the feasible interval to obtain the terminal state after relative motion control at each trial point; Optimal solution determination module: Among the series of terminal states obtained, one set is determined as the optimal solution based on the terminal optimization conditions.

7. A relative motion control planning system considering terminal velocity constraints according to claim 6, characterized in that: The determination of the feasible time range for the control planning transition is specifically as follows: The feasible time interval for controlling the transition includes the minimum time t. min and maximum time t max Where, the minimum time t min It is necessary to consider the current navigation status of the spacecraft and the preparation time required to perform orbital control maneuvers. After the spacecraft establishes stable relative navigation and is ready to perform orbital control, if the current time is t, then t min >t; Maximum time t max Related to the overall rendezvous and docking mission, if the mission's allowed transfer time is t task , then t max <t task .

8. A relative motion control planning system considering terminal velocity constraints according to claim 7, characterized in that: The determination of the traversal time interval is specifically as follows: Based on the computing power of the onboard computer and the actual mission requirements, the feasible range of the control planning transfer time is evenly divided into N+1 iterative control planning calculation time points. That is, t0=t min t1=t min +(t max -t min ) / N、t2=t min +2 (t max -t min ) / N、……、t N =t max The calculation time point of the iterative control planning is the trial calculation point.

9. A relative motion control planning system considering terminal velocity constraints according to claim 8, characterized in that: The method of iterative predictive control programming traverses all results within the feasible transition time interval of the control program, specifically as follows: (3.1) Before traversing, latch the traversal input parameters based on the relative navigation results, i.e., the current relative distance between the two spacecraft. Relative velocity The orbital angular velocity of the spacecraft relative to the origin of the navigation coordinate system. The above input parameters remain unchanged during a complete traversal calculation; (3.2) Based on each determined trial point , First, the relative position and velocity are extrapolated without power to the trial point using the relative motion equations to obtain the relative position of the control planning position. and relative velocity Using the relative position and relative velocity obtained by this extrapolation, combined with the target position of the control plan, and remaining transfer time Perform relative motion control planning calculations to obtain the velocity increment. This velocity increment is added to the relative velocity at the trial time. The relative velocity obtained after orbital control is applied: ， Combined with the relative positions at the trial calculation time The terminal time is obtained by performing unpowered extrapolation. relative position and relative velocity ; (3.3) Following the method of step (3.2), calculate N+1 times, traverse all trial points, and obtain N+1 results, which are the terminal states after relative motion control.

10. A relative motion control planning system considering terminal velocity constraints according to claim 9, characterized in that: The process of determining one set of terminal states as the optimal solution from a series of obtained terminal states, based on terminal optimization conditions, is as follows: Assume the optimization objective of the relative velocity in the z-direction is Then, the difference between the terminal state of all trial points and the optimization target is obtained. Take all The minimum value in the set is taken as the optimization result, that is, the control program result that is closest to the terminal optimization objective.

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