A multi-satellite autonomous task planning method based on constraint contract net

Abstract

The application provides a multi-satellite autonomous task planning method based on a constraint contract net, and the problem of joint autonomous task planning of a satellite system composed of multiple satellites can be solved by introducing an Agent (intelligent agent) and a Multi-Agent system (MAS) theory, which comprises the following steps: a leading satellite receives an observation task, and candidate satellites capable of executing the observation task are screened out from subordinate satellites; a contract net negotiation method is used to select a contractee from the candidate satellites capable of executing the observation task; the subordinate satellite selected as the contractee starts task execution preparation before the task execution time arrives, executes the contract task after the preparation is completed, feeds back information about the execution result to the leading satellite, the leading satellite sends a task completion notification to announce the end of the task.

Description

Technical Field

[0001] This invention relates to the field of satellite intelligent management technology, and in particular to a multi-satellite autonomous mission planning method based on a constraint contract network. Background Technology

[0002] Autonomous mission planning technology is one of the key technologies for realizing intelligent remote sensing satellites. The traditional operational process of non-intelligent remote sensing satellites is "requirements collection – requirements planning – mission planning – satellite execution – image processing – user distribution," which suffers from redundancy, tight coupling of processes, and numerous constraints, resulting in long response times and poor emergency observation capabilities. By utilizing onboard autonomous mission planning technology, the operational process can be shortened to "requirements collection – satellite autonomously completing mission planning and image processing – user distribution," with a large amount of work completed autonomously by the satellite, achieving the goal of shortening mission response time and enhancing reaction speed.

[0003] The research on mission planning technology for single satellites is relatively mature and has been implemented in various models. The paper "Autonomous Mission Planning Methods for Agile Imaging Satellites" (Computer Integrated Manufacturing Systems, No. 4, 2016) studies and summarizes the autonomous mission planning problem for a single agile imaging satellite, proposing a rolling planning heuristic algorithm that uses multiple consecutive local planning steps to replace a one-time global planning. This algorithm is applied in orbit, and the relationship between the rolling planning step size and mission completion rate is analyzed using experimental data.

[0004] With the increasing number of remote sensing satellites in my country, the growing demand for observation, and the maturing of inter-satellite link technology, joint observation using multiple remote sensing satellites is imperative. However, multi-satellite joint autonomous mission planning technology involves research on the coordination mechanism among multiple satellites, which is more technically challenging than single-satellite mission planning. Currently, no multi-satellite joint mission planning system has been applied in orbit. The paper "Research on In-orbit Real-time Guided Multi-Satellite Imaging Mission Planning Method" (Spacecraft Engineering, October 2019) proposes a multi-satellite mission planning method for in-orbit real-time guided imaging. It designs a conflict-free mission sequence generation method for satellite imaging and an ad-hoc adjustment strategy to optimize imaging benefits. Simulation results show that the imaging benefits of the entire planning scheme can be improved in real time by replacing low-benefit targets with high-benefit targets. However, this scheme belongs to a ground-based centralized planning strategy and is not an on-board autonomous mission planning method. Summary of the Invention

[0005] This invention proposes a multi-satellite autonomous mission planning method based on constrained contract networks. By introducing Agent and Multi-Agent System (MAS) theory, it can solve the problem of joint autonomous mission planning in a satellite system composed of multiple satellites.

[0006] The present invention is achieved through the following technical solution.

[0007] A multi-satellite autonomous mission planning method based on a constrained contract network includes: a master satellite receiving an observation mission and selecting candidate satellites capable of performing the observation mission from among subordinate satellites; selecting a contractor from the candidate satellites capable of performing the observation mission using a contract network negotiation method; the subordinate satellite selected as the contractor initiating mission execution preparation before the mission execution time is approaching, executing the contract mission after preparation is completed, and feeding back information about the execution results to the master satellite; the master satellite then sends a mission completion notification, declaring the mission over.

[0008] The beneficial effects of this invention are:

[0009] 1. Compared with existing single-satellite mission planning technology, the mission planning method proposed in this invention can make full use of the advantages of multi-satellite collaborative observation, and the leading satellite can select suitable satellites from the set of potential candidate satellites in real time on orbit to execute the mission, thereby improving the mission completion rate.

[0010] 2. This invention adopts a hierarchical structure of leading satellites and subordinate satellites in a multi-satellite joint mission planning system. The leading satellite refers to a satellite node that has the capability of joint planning of the satellite constellation and can select and guide subordinate satellites to complete the predetermined observation tasks. The subordinate satellites have the capability of single-satellite planning and the ability to execute specific observation actions. Thus, a multi-satellite collaborative mechanism between leading satellites and subordinate satellites is designed.

[0011] 3. The joint mission planning process based on contract network negotiation proposed in this invention includes pre-screening of candidate satellites, mission release, mission bidding, mission bidding evaluation, contract signing, and mission execution, forming a complete closed-loop control chain. Through this process, the satellite system can plan, generate, and execute the best observation scheme that meets the global optimization objective, and provide feedback on the execution results.

[0012] 4. In the existing technology, the bidding judgment of a bidder for a certain task is a dynamic scheduling process. The bidder itself maintains a set of contracted tasks that have been signed. When a new bidding task arrives, the bidder must insert the new task into the appropriate time interval without causing conflicts. This dynamic scheduling process is a complex constraint solving process. The present invention uses a backtracking algorithm for dynamic task scheduling. On the one hand, it must ensure the consistency of various constraints in the scheduling scheme, and on the other hand, it must meet certain scheduling optimization objectives.

[0013] 5. The present invention sets pre-screening rules for multiple candidate satellites capable of performing the observation task, including communication capability satisfaction check, imaging capability satisfaction check, and payload capability satisfaction check, thereby selecting candidate satellites;

[0014] 6. This invention adopts a contract network negotiation method, which allocates the task among multiple bidders according to the bidding-tendering-winning mechanism in the market, and selects the contracter from the candidate satellites that can perform the observation task. Attached Figure Description

[0015] Figure 1 This is a flowchart illustrating the overall process of the multi-satellite autonomous mission planning method based on constraint contract networks of the present invention.

[0016] Figure 2 This is a flowchart of the backtracking algorithm in a specific embodiment of the present invention. Detailed Implementation

[0017] Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be understood that the embodiments shown and described in the drawings are merely exemplary and are intended to illustrate the principles and spirit of the present invention, and are not intended to limit the scope of the present invention.

[0018] The core idea of ​​this invention is to adopt a "master-slave" structure, designating a master satellite in a satellite system requiring joint mission planning, with all other satellites serving as slave satellites. The master satellite is a satellite node possessing constellation joint planning capabilities, capable of selecting and guiding slave satellites to complete predetermined observation tasks. Slave satellites possess individual satellite planning capabilities and the ability to execute specific observation tasks. Inter-satellite communication capabilities exist between the master and slave satellites. Generally, the master satellite should be a satellite with real-time satellite-to-ground communication capabilities and strong onboard processing power; a typical example is a geostationary orbit satellite.

[0019] Based on the above ideas, such as Figure 1 As shown, the multi-satellite autonomous mission planning method based on constrained contract networks of the present invention specifically includes the following steps:

[0020] Step 1: Lead the satellite reception and observation task;

[0021] In this embodiment, the observation task originates from a ground-based task, a task autonomously generated by the leading satellite, or a task generated and transmitted by other satellites.

[0022] In this embodiment, the observation task includes: Task=<target location, observation time window start point, observation time window end point, payload type, resolution requirement, and task priority.

[0023] In practice, an observation task requires specifying the location of the target to be observed, described by the target's latitude and longitude; specifying the start and end times of the task, i.e., the start and end points of the observation time window; specifying the imaging payload used for observation, including visible light, electronic reconnaissance, infrared, or SAR; specifying the payload resolution requirements for certain payloads; and specifying the task priority, in which case higher priority tasks take precedence over lower priority tasks in the event of a conflict.

[0024] Step 2: The lead satellite selects candidate satellites from the subordinate satellites that can perform the observation mission.

[0025] In practice, the leading satellite performs pre-screening based on the attributes of the observation mission and the orbital information of each subordinate satellite, and adds the subordinate satellites that pass the pre-screening to the candidate satellite set. For satellites that fail the check, the leading satellite reports that the mission execution has failed.

[0026] In this embodiment, the pre-screening rules include:

[0027] 1. Communication capability fulfillment check: Within the time window of [current time, start of observation time window], whether the subordinate satellite has the ability to conduct inter-satellite communication with the master satellite;

[0028] 2. Imaging capability satisfaction check: Within the time window of [the start and end of the observation time window], does the subordinate satellite have the capability to perform imaging observation of the target location?

[0029] 3. Payload capability compliance check: Whether the payloads of the subordinate satellite that can perform imaging observations of the target location meet the requirements of payload type and payload resolution.

[0030] Step 3: Select a contractor from candidate satellites capable of performing the observation task through a contract network negotiation process;

[0031] The contract network protocol described in this invention is a negotiation method, which is mainly used in distributed sensor systems in the prior art to complete the transmission of control in a strictly distributed system. Its importance lies in the fact that task managers and potential executors select each other through a computational negotiation process, that is, to allocate tasks among multiple bidders according to the bidding-tendering-winning mechanism in the market. It is a dynamic and distributed method.

[0032] In this embodiment, the contract network consists of several nodes, which are divided into the following three categories:

[0033] The bidding party, acting as the lead satellite, is responsible for allocating the tasks that should be completed to other nodes.

[0034] Bidders are subordinate satellites in the candidate satellite set; they are idle nodes with the ability to complete certain tasks.

[0035] The contractor, as the subordinate satellite responsible for executing the observation mission, is the successful bidder and has the task to complete.

[0036] Based on the above explanation of the contract network and its nodes, in this embodiment, the contract network negotiation includes the following steps:

[0037] A) Observation mission release: After receiving the observation mission, the lead satellite releases the mission to the subordinate satellites within the available communication window with the relevant bidders, and transmits the bid deadline and the constraints for completing the mission to the subordinate satellites.

[0038] In practice, the task is issued to subordinate satellites using a triplet description:<AID,Task,DL> Where AID is the identifier of the tendering party, Task is the tendered task, which includes the requirements for the task and the set of constraints for completing the task, and DL is the deadline for submitting bids.

[0039] B) Mission Bidding: After receiving an observation mission, the subordinate satellite makes a bidding decision based on its own situation and the mission's constraints. There are three main types: rejection, misunderstanding, and bidding; specifically:

[0040] If you are bidding, the bidding information must be honest and described using triples.<bidder,Plan,Cost> Where bidder is the identifier of the bidding satellite, and Plan is the scheduling scheme of the bidding satellite for the mission; the scheduling scheme is represented by a seven-tuple: Plan = <imaging payload type, imaging payload resolution, start imaging time, end imaging time, start data transmission time, end data transmission time, data transmission station number>, and Cost is the cost incurred by the bidder to complete the mission.

[0041] In practice, a bidder's decision to submit a bid for a specific task is a dynamic scheduling process. Each bidder maintains a set of already signed contract tasks. When a new bidding task arrives, the bidder must insert the new task into the appropriate time frame without causing conflicts. This dynamic scheduling process is a complex constraint-solving process, requiring both ensuring the consistency of various constraints in the scheduling scheme and satisfying certain scheduling optimization objectives.

[0042] To address this requirement, this embodiment employs a backtracking algorithm for dynamic task scheduling, such as... Figure 2 As shown, the specific steps are as follows:

[0043] Step 1: Obtain the planned mission set from the subordinate satellite.S ={P1,P2,…,P i ,…,P N The task to be planned is P';

[0044] Step 2: Determine whether a time window TW exists in the time window set TW on this satellite. j =(ws j ,we j Task P' can be inserted, where ws j and we j These refer to the start and end times of the time window, respectively; if they exist, P' is directly inserted into TW. j If you must proceed to Step 5, otherwise proceed to Step 3.

[0045] Step 3: For task P' that cannot be directly inserted, calculate the time window conflict and storage conflict set of task P'. Assuming that the planned task that has a conflict is replaced, determine whether there is a free time period in other time windows for the conflicting task in the replacement conflict to be inserted. If there is, the assumption is true and the conflicting task is inserted into the free time period. Go to Step 5. Otherwise, the assumption is false and go to Step 4.

[0046] Step 4: If the above two methods fail to insert the task, then search the conflict set to see if there exists a task P with a lower priority than P'. i If P exists i Then delete P. i and P i Set it as a task to be planned, add P' to the already planned tasks, and jump to Step 2; otherwise, the task insertion fails and the algorithm ends.

[0047] Step 5: Complete the planning of the inserted tasks, generate a new set of planned tasks, and the algorithm ends.

[0048] C) Mission Bid Evaluation: After the lead satellite receives all bid results or the bid deadline expires, it evaluates the bid proposals according to the predetermined evaluation strategy, selects the best bid proposal, issues a notice of award to the corresponding bidder, and issues a notice of rejection to other bidders.

[0049] In practice, the evaluation strategy is related to the global optimization goal, and different evaluation strategies can be formulated according to different optimization goals. The global optimization goals include minimum cost, earliest imaging time, earliest data transmission time, and load balancing.

[0050] D) Signing of task contract: After receiving the winning notice, the winning bidder officially adds the task to its contract task set and replies with a confirmation message. The contract between the two parties is established. After receiving the confirmation message, the leading satellite marks the task as a contract task and waits for the feedback of the execution result information.

[0051] Step 4: The subordinate satellite selected as the contractor starts to prepare for task execution before the task execution time arrives. After the preparation is completed, it executes the contract task and feeds back the information about the execution result to the leading satellite. The leading satellite sends a task completion notice to announce the end of the task.

[0052] Embodiment 1:

[0053] The following takes a certain forest fire observation task as an example to introduce the multi-satellite autonomous task planning method based on the constrained contract net of the present invention in detail.

[0054] Suppose a forest fire occurs at a certain place (latitude 37.81, longitude 72.34), and the Ministry of Emergency Management requires obtaining optical observation images of this place within 3 hours, and the imaging time is as early as possible, and the observation resolution is not less than 1m. Suppose the heterogeneous satellite system available for observing forest fires includes the following satellites:

[0055]

[0056] The specific implementation process of the satellite system joint task planning technology is as follows:

[0057] 1. Task reception

[0058] The ground uploads the observation task to the leading satellite, Task = <(latitude 37.81, longitude 72.34), current time, current time + 3 hours, visible light, resolution less than 1m>.

[0059] 2. Satellite pre-screening

[0060] The leading satellite pre-screens 10 subordinate satellites. The subordinate satellites that meet the communication ability, imaging ability and payload ability include low-earth orbit optical satellite 3 and low-earth orbit optical satellite 4. The leading satellite adds these 2 satellites to the candidate satellite set.

[0061] 3. Contract net negotiation

[0062] Within the available communication window between the leading satellite and the relevant bidders, the leading satellite publishes the task to the relevant satellites. The published information is a triple: <ID geostationary satellite, Task, DL>, and DL is set to half an hour before the task required time, DL = current time + 2.5 hours.

[0063] After receiving the bidding information, the 3 candidate satellites send bidding information to the leading satellite within the DL time limit.

[0064] Low Earth Orbit Optical Satellite 3: <ID Low Earth Orbit 3, Plan Low Earth Orbit 3, Cost Low Earth Orbit 3>, where Plan Low Earth Orbit 3 = <Visible light, 0.3m, Current time + 20 minutes, Current time + 23 minutes, Current time + 50 minutes, Current time + 55 minutes, Xiamen Station>, Cost Low Earth Orbit 3 = 0.

[0065] Low Earth Orbit Optical Satellite 4: <ID Low Earth Orbit 4, Plan Low Earth Orbit 4, Cost Low Earth Orbit 4>, where Plan Low Earth Orbit 4 = <Visible light, 0.3m, Current time + 1 hour 52 minutes, Current time + 1 hour 55 minutes, Current time + 2 hours 10 minutes, Current time + 2 hours 15 minutes, Xiamen Station>, Cost Low Earth Orbit 4 = 0.

[0066] After receiving the bidding information sent by these 2 satellites, the leading satellite evaluates the bidding proposals according to the strategy of the earliest imaging time, selects Low Earth Orbit Optical Satellite 3 as the winner, sends a winning notice to the corresponding bidder, and sends a rejection notice to other bidders.

[0067] After receiving the winning notice, Low Earth Orbit Optical Satellite 3 officially adds the task to its contract task set and replies with a confirmation message, and the contract between the two parties is established. After receiving the confirmation message, the leading satellite marks the task as a contract task and waits for the feedback of the execution result information.

[0068] 4. Task Execution

[0069] Before the task execution time of Low Earth Orbit Optical Satellite 3 is about to arrive, it starts the relevant preparations for task execution. After the preparations are completed, it executes the contract task, downloads the image to the ground station for processing, and feeds back the information about the execution result to the leading satellite. The leading satellite sends a notice of task completion to the Ministry of Emergency Management, declaring the end of the task.

[0070] Those of ordinary skill in the art will realize that the embodiments described herein are for the purpose of assisting the reader in understanding the principles of the present invention, and it should be understood that the scope of protection of the present invention is not limited to such specific statements and embodiments. Those of ordinary skill in the art can make various other specific deformations and combinations without departing from the essence of the present invention based on the technical revelations disclosed in the present invention, and these deformations and combinations are still within the scope of protection of the present invention.

Claims

1. A multi-satellite autonomous mission planning method based on constrained contract networks, characterized in that, include: The lead satellite receives observation tasks and selects candidate satellites from subordinate satellites that can perform the observation tasks; Contractors were selected from candidate satellites capable of performing the observation tasks through a contract network negotiation process. Before the scheduled mission execution time, the subordinate satellite selected as the contractor initiates mission execution preparations. After the preparations are completed, it executes the contracted mission and feeds back information about the execution results to the lead satellite. The lead satellite then sends a mission completion notification, declaring the mission over. The observation task includes: target location, start point of observation time window, end point of observation time window, payload type, resolution requirement, and task priority; The master satellite pre-screens satellites based on the attributes of the observation mission and the orbital information of each subordinate satellite. Subordinate satellites that pass the pre-screening are added to the candidate satellite set. For satellites that fail the check, the master satellite reports mission execution failure. The pre-screening rules include: Communication capability fulfillment check: Within the time window (current time, start of the observation time window), does the subordinate satellite have the capability to conduct inter-satellite communication with the master satellite? Imaging capability satisfaction check: Within the time window (start of the observation time window, end of the observation time window), does the subordinate satellite have the capability to perform imaging observation of the target location? Payload capability compliance check: whether the payloads that the subordinate satellites can use to perform imaging observations of the target location meet the requirements of payload type and payload resolution; The contract negotiation process includes the following steps: A) Observation mission release: After receiving the observation mission, the lead satellite releases the mission to the subordinate satellites within the available communication window with the relevant bidders, and transmits the bid deadline and the constraints for completing the mission to the subordinate satellites. B) Mission Bidding: After receiving an observation mission, the subordinate satellite makes a bidding decision based on its own situation and the constraints of the mission. There are three types: rejection, misunderstanding, and bidding. C) Mission Bid Evaluation: After the lead satellite receives all bid results or the bid deadline expires, it evaluates the bid proposals according to the predetermined evaluation strategy, selects the best bid proposal, issues a notice of award to the corresponding bidder, and issues a notice of rejection to other bidders. D) Contract signing: After receiving the notification of award, the successful bidder will formally add the task to its contract task set and reply with confirmation information. The contract between the two parties is established. After receiving the confirmation information, the lead satellite will mark the task as a contract task and wait for feedback on the execution results. The task is issued to subordinate satellites, described using a triplet:<AID, Task, DL> Where AID is the identifier of the tendering party, Task is the tendered task, which includes the requirements for the task and the set of constraints for completing the task, and DL is the deadline for submitting the bid. The specific details of the task bidding are as follows: If you are bidding, the bidding information must be honest and described using triples.<bidder, Plan, Cost> Where bidder is the identifier of the bidding satellite, Plan is the scheduling scheme of the bidding satellite for the mission; the scheduling scheme is represented by a seven-tuple: imaging payload type, imaging payload resolution, start imaging time, end imaging time, start data transmission time, end data transmission time, data transmission station number, and Cost is the cost incurred by the bidder to complete the mission. The backtracking algorithm is used for dynamic task scheduling. The specific steps are as follows: Step 1: Obtain the planned mission set from subordinate satellites. The task to be planned is P'. Step 2: Determine if a time window TW exists in the time window set TW on this satellite. j =(ws j , we j Task P' can be inserted, where ws j and we j These refer to the start and end times of the time window, respectively; if they exist, P' is directly inserted into TW. j If you must proceed to Step 5, otherwise proceed to Step 3. Step 3: For task P' that cannot be directly inserted, calculate the time window conflict and storage conflict set of task P'. Assuming that the planned task with the conflict is replaced, determine whether there is a free time period in other time windows for the conflicting task in the replacement conflict to be inserted. If there is, the assumption is true and the conflicting task is inserted into the free time period. Go to Step 5. Otherwise, the assumption is false and go to Step 4. Step 4: If the above two methods fail to insert the task, then search the conflict set to see if there exists a task P with a lower priority than P'. i If P exists i Then delete P. i and P i Set it as a task to be planned, add P' to the already planned tasks, and jump to Step 2; otherwise, the task insertion fails and the algorithm ends. Step 5: Complete the planning of the inserted tasks, generate a new set of planned tasks, and the algorithm ends.

2. The multi-satellite autonomous mission planning method based on constrained contract networks as described in claim 1, characterized in that, The observation tasks originate from ground-based tasks, tasks generated autonomously by the leading satellite, or tasks generated and transmitted by other satellites.

3. The multi-satellite autonomous mission planning method based on constrained contract networks as described in claim 1 or 2, characterized in that, The contract network consists of several nodes, which are divided into the following three categories: The bidding party, acting as the lead satellite, is responsible for allocating the tasks that should be completed to other nodes. Bidders are subordinate satellites in the candidate satellite set; they are idle nodes with the ability to complete certain tasks. The contractor, as the subordinate satellite responsible for executing the observation mission, is the successful bidder and has the task to complete.

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