Automatic dependent surveillance target reduction method based on target number sliding window detection

Abstract

The invention discloses an automatic dependent surveillance target reduction method based on target quantity sliding window detection, relates to the technical field of air traffic data monitoring, and comprises the following steps: obtaining an ADS-B message of a target; preprocessing the ADS-B message, extracting and caching an ICAO address and structured message data in the ADS-B message in a message receiving cycle to form a key-value pair, wherein the key is the ICAO address and the value is the structured message data; storing and performing track calculation on the ADS-B message; taking out all ICAO addresses in the current detection window, performing deduplication and statistical operations to obtain the number of ICAO addresses, and adjusting decoding sensitivity according to the number of target ICAO addresses, thereby completing target reduction; the invention can dynamically adjust the sensitivity to limit the receiving distance, and has the advantages of fast response speed and wide applicable equipment types.

Description

Technical Field

[0001] The invention relates to the technical field of air traffic data monitoring, and in particular to an automatic correlation monitoring target reduction method based on target quantity sliding window detection. Background Art

[0002] Automatic dependent surveillance-broadcast (ADS-B) is an aircraft surveillance technology whereby aircraft determine their position via satellite navigation systems and broadcast it periodically, making it trackable. Air traffic control ground stations can receive this information and use it as a replacement for secondary radar, eliminating the need to send interrogation signals from the ground. Other aircraft can also receive this information to provide attitude awareness and autonomous avoidance. ADS-B consists of two services (outgoing and incoming): "ADS-B Out" and "ADS-B In". "ADS-B Out" periodically broadcasts each aircraft's unique ICAO address, position, altitude, speed, and other information via an onboard transmitter. "ADS-B In" refers to receiving ADS-B data via a receiver.

[0003] ADS-B automatic dependent surveillance technology has become the mainstream aircraft surveillance technology. ADS-B technology is also used in small aircraft applications such as gliders, balloons, paragliders, small drones, and near-space aircraft. These devices are usually powered by batteries or solar energy, and are very sensitive to the power consumption indicators of airborne equipment. In terms of functional requirements, ADS-B OUT is the main requirement.

[0004] As the number of aircraft increases, the demand for ADS-B In equipment is also increasing. Pilots can obtain information about nearby flight targets monitored by ADS-B In equipment through display devices such as CDTI or cockpit displays, optimize flight plans based on airspace flight conditions, and reduce collision risks. In applications such as drones and unmanned sounding balloons, monitoring data is transmitted and displayed through ground-to-air data links, so that drone operators can adjust flight plans based on airspace flight conditions.

[0005] The American Radio Commission for Aeronautics standard number for ADS-B equipment is DO-260, and the Chinese Civil Aviation Technical Standard number is CTSO-166 (the clauses refer to DO-260). The receiving subsystem capability classification of DO-260 stipulates the decoding sensitivity (MTL, also known as receiving sensitivity) and minimum track number processing capability of the corresponding equipment level. MTL is specifically the minimum signal trigger level.

[0006] Considering the overall configuration of the ADS-B surveillance system, the number of tracks also affects the data link bandwidth, display device display processing capabilities, and database design. The power consumption and design costs of airborne equipment directly affect the reliability of the equipment and the adaptability of the carrier platform. Reducing the power consumption and cost of ADS-B equipment can improve the adaptability of the equipment on various carrier platforms, making the power supply simpler, the weight lighter, and the installation and maintenance more convenient.

[0007] Therefore, in order to reduce the overall cost of the system, such as cost and power consumption, a lower device level should be selected as much as possible while meeting the usage requirements, and the number of system target monitoring should be reduced.

[0008] When configuring small airborne ADS-B In equipment, in order to reduce power consumption, the technical solution usually chooses low-power processors, mainly 16-bit and 32-bit microcontrollers, and generally without floating-point processing units, such as STM32F4, whose computing performance is generally 210DMIPS. Under the test conditions of 300 flight targets provided by the simulator, only 110-120 tracks can be generated at full load. Using a high-performance CPU can generate more tracks, but the high power consumption, electromagnetic compatibility requirements and high design overhead caused by high performance reduce its availability and reliability. Although with the development of semiconductor technology, CPUs with lower power consumption and higher performance will eventually meet application requirements, in actual engineering applications, a larger number of tracks beyond the equipment level will not only bring higher performance requirements for the CPU, but also lead to further increases in the interface data bandwidth and display processing equipment capabilities of the entire ADS-B receiving subsystem, thereby increasing the design difficulty of the entire monitoring system.

[0009] In addition, the number of aircraft and vehicles equipped with ADS-B OUT functions has greatly increased around the world, and there is a high possibility that the number of aircraft targets in busy areas exceeds the tolerance of the equipment to process the track. For example, the A0-level receiving equipment has limited the receiving distance by reducing the receiving sensitivity: the equipment sensitivity is better than -72dBm (-73dBm is better than), and the effective monitoring range after calculation at -72dBm is about 60 nautical miles in radius, but if it is 60 nautical miles near a busy airport, the number of flight targets received may exceed 100. If the number of tracks processed is not limited, exceeding the processing capacity of the ADS-B In equipment may cause equipment jams, delays and crashes.

[0010] Based on the above two reasons, it is necessary to complete target reduction according to the equipment level. For example, if the track tolerance of an A0-level device is set to 120, when there are 200 flying targets within the monitoring range, only 120 tracks can be established and maintained, and the ADS-B messages sent by the remaining 80 targets will be discarded.

[0011] The technical requirements related to target reduction in the current DO-260 standard are:

[0012] (1) Lowering MTL requirements: Lowering MTL can reduce the signal receiving distance of the device. For example, the MTL of A1-level receiving equipment is better than -79dBm, and the target processing tolerance is not less than 200; the MTL of A0-level receiving equipment is better than -72dBm, and the target processing tolerance is not less than 100. A lower target processing tolerance is accompanied by a lower MTL requirement, which reduces the monitoring range and thus reduces the number of targets.

[0013] (2) Dynamic sensitivity tuning (DMTL): When low-power signals are mixed with high-power signals, the receiver prioritizes high-power signals and discards low-power signals by raising the minimum trigger level. The signal from a closer target is necessarily stronger, and a receiver with DMTL capability can prioritize identifying closer targets. This technology is designed to avoid multipath interference of signals.

[0014] The existing technology is to narrow the track file after the track is generated, compare the distance according to the target position information, and discard the track of the farther target, that is, solve first and then filter. In the process of establishing the target track, the CPR position solution involving double-precision floating-point operations consumes the most resources. To compare the distance between each target and the aircraft, the position solution must be performed first. The advantage of this technology is that it can give priority to identifying targets that are closer, saving bandwidth transmitted to CDTI and comprehensive display, and reducing the processing load of the display device. The disadvantage is that the position solution software module consumes the most resources and cannot reduce the load on the ADS-BIn equipment. When the computing power and memory are insufficient, it will cause system delays or crashes. Summary of the invention

[0015] The purpose of the present invention is to provide a method for achieving target reduction, which can solve the following two problems at the same time: (1) prioritize identifying targets that are closer to the aircraft, and when the number of targets within the monitoring range is greater than the track tolerance, ensure that the monitored targets are close targets as much as possible; (2) reduce the amount of calculation so that the CPU and memory load of the ADS-B In device does not exceed the maximum design capacity.

[0016] Therefore, the present invention provides an automatic correlation surveillance target reduction method based on target quantity sliding window detection, comprising the following steps:

[0017] S100. Receive the target ADS-B message and decode it to obtain an ADS-B message;

[0018] S200. Preprocess the ADS-B message, extract and cache the ICAO address and structured message data in the ADS-B message in a message receiving cycle to form a key-value pair, the key is the ICAO address, and the value is the structured message data;

[0019] S300. Store and calculate the track of ADS-B messages. S300 includes:

[0020] S310. Queue storage and processing of ADS-B messages within the message receiving cycle according to the ICAO address to obtain an ADS-B message queue;

[0021] S311. Perform track-related operations on the ADS-B messages in the ADS-B message queue and maintain the target track file. Maintaining the target track file specifically includes: updating the track file, creating a new track file, and deleting the track file; in response to the message sending cycle drive or event drive, sending the target track message to the data link receiving end;

[0022] S320. Acquire the detection window according to the message receiving cycle interrupt signal, extract all ICAO addresses in the current detection window in the cached ADS-B message and store them in a double linked list; the double linked list storage includes unidirectional circular chain storage and ordinary chain storage, the unidirectional circular chain storage is the unidirectional circular chain storage between each message detection cycle in the detection window, and the ordinary chain storage is the chain storage between each ICAO address in each message detection cycle; each node in the unidirectional circular chain storage stores the pointer of the first ICAO address in each detection cycle;

[0023] S400. Take out all ICAO addresses in the current detection window, perform deduplication and statistical operations to obtain the number of ICAO addresses, and adjust the decoding sensitivity according to the target number of ICAO addresses, thereby completing the target limit reduction.

[0024] Furthermore, the method further comprises the following steps:

[0025] S500. Calculate the system health E. If the system health is lower than the threshold, adjust the sliding window parameters according to the calculated system health E, perform sliding window operation on the detection window according to the sliding window parameters, update the double linked list, and repeat step S400 to continuously adjust the decoding sensitivity; the sliding window parameters include the detection window length, the number of memories and the message receiving cycle, , where T represents the detection window length, Indicates the message receiving cycle, and a indicates the number of memories.

[0026] Specifically, the process of performing queue storage processing on ADS-B messages within a message receiving period according to the ICAO address to obtain an ADS-B message queue includes the following steps: sequentially comparing the ICAO addresses of all ADS-B messages within the message receiving period with the ICAO address list obtained by statistics in the existing target track file; if there is a matching item in the ICAO address list, adding the ADS-B message to the processing queue, and storing and updating the ADS-B messages of the same target; if there is no matching item in the ICAO address list, determining whether the current target storage quantity exceeds a preset maximum target storage quantity value N; if so, discarding the ADS-B messages of the targets exceeding the maximum target storage quantity value N; if not, adding the ADS-B message to the processing queue, and storing the ICAO address of the ADS-B message in the ICAO address list.

[0027] Preferably, the ICAO address list uses hashing to store ICAO addresses; the ICAO addresses of all messages are compared with the existing ICAO address list in sequence, specifically, the hash values ​​of the ICAO addresses are compared.

[0028] Specifically, maintaining the target track file in S311 includes:

[0029] If there is no new ICAO address, that is, there is a matching item in the ICAO address list, the ADS-B message corresponding to the ICAO address is directly updated; if there is a new ICAO address, that is, there is no matching item in the ICAO address list, a new target track based on the ICAO address is established, and then the ADS-B message corresponding to the ICAO address is stored; the track files that exceed the life cycle management are deleted.

[0030] Specifically, the data link receiving end is one or more of a cockpit CDTI, a UAV ground command center, and a satellite data link ground station.

[0031] Furthermore, the decoding sensitivity adjustment according to the number of target ICAO addresses includes the following steps:

[0032] (1) Determine whether the number of target ICAO addresses exceeds the preset target tolerance. If so, pre-increase the MTL value; otherwise, pre-decrease the MTL value; MTL represents the minimum signal trigger level;

[0033] (2) Perform dynamic range detection on the pre-adjusted MTL value, that is, compare it with the maximum and minimum values ​​preset by the system. If the maximum value is reached, it will not increase further, and if the minimum value is reached, it will not decrease further.

[0034] (3) Adjust the decoding sensitivity according to the MTL value.

[0035] Furthermore, the sliding window parameters are adjusted according to the calculated system health E as follows: when the health decreases, T and r are reduced; when the health increases, T and r are increased.

[0036] Furthermore, the system health calculation steps are as follows:

[0037] (1) Calculate the health of a single target:

[0038] ;

[0039] in, Indicates the health of a single target. Status indicates the status of the target in the track file. The initial state is 2, the acquisition state is 1, and the tracking state is 0. AIC indicates the time deviation value of the aircraft identity and type message, with an update rate of 5 seconds / time and an initial value of 0. AP indicates the time deviation value of the air position message, with an update rate of 0.5 seconds / time and an initial value of 0. SP indicates the time deviation value of the ground position message, with an update rate of 5 seconds / time and an initial value of 0. Av indicates the time deviation value of the air speed message, with an update rate of 0.5 seconds and an initial value of 0. When AP exists, the SP value is 0. When SP exists, the AP value is 0. AP and SP messages are mutually exclusive. The specific calculation of the time deviation value of each message is as follows:

[0040] aic = (current time - timestamp of the most recent message) / 5

[0041] ap = (current time - timestamp of the most recent message) / 0.5

[0042] sp = (current time - timestamp of the most recent message) / 5

[0043] av = (current time - timestamp of the most recent message) / 0.5;

[0044] The health of all targets is obtained by calculating the health of a single target, forming the target health matrix w n ;

[0045] (2) Calculate system health E:

[0046] ;

[0047] Among them, normalization means normalization processing; w n represents the target health matrix; p represents the weight vector, , the dimension is 5*1; n represents the number of ICAO addresses of the target in the track file; represents the load factor, = Number of ICAO addresses in track file target / system tolerance, The result range is 0~1.2; k represents the sliding window target address matching degree, k=1-diff (sliding window target ICAO address Track file ICAO address), the result range of k is 0~1.

[0048] Meanwhile, the present invention discloses an automatic correlation monitoring target reduction system based on target quantity sliding window detection, the system is used for correlation monitoring of aircraft to reduce the target, and the system adopts the above method.

[0049] After adopting the above scheme, the beneficial effects of the present invention are as follows:

[0050] (1) Wide range of applicable equipment types: It can be used for ADS-B In equipment of various technical architectures. Since the DO-260 standard requires ADS-B In equipment to have DMTL capabilities, the present invention uses this module to perform dynamic sensitivity adjustment without making a lot of changes to the prescribed technical architecture, saving development time and reducing development risks. In addition, there are many adjustable parameters in the sliding window method, which is suitable for processing scenarios of different scales and has strong technical adaptability.

[0051] (2) The core system design method and sliding window detection sensitivity adjustment mechanism of the airborne ADS-B equipment of the present invention can effectively detect close-range, high-risk targets near the aircraft in a low-power embedded platform with small computing and storage resources. While meeting the functional performance requirements of the equipment standard, the restrictions on processor selection can be reduced, the platform adaptability can be enhanced, and the six performance indicators (reliability, environmental adaptability, maintainability, etc.) of the airborne ADS-B equipment as a whole can be effectively improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 It is the main flow chart of the method of the present invention;

[0053] Figure 2 It is a principle block diagram corresponding to the method of the present invention;

[0054] Figure 3 The following is a typical ADS-B surveillance system structure diagram (single aircraft);

[0055] Figure 4 This is a general ADS-B In architecture diagram;

[0056] Figure 5 The schematic diagram for sending and processing track files;

[0057] Figure 6 This is a flow chart of message preprocessing based on ICAO;

[0058] Figure 7This is an example diagram of a sliding window detection method for target monitoring range based on sensitivity adjustment;

[0059] The English parameters in the attached figure are explained as follows:

[0060] FPGA: Field Programmable Gate Array;

[0061] ASIC: Application Specific Integrated Circuit;

[0062] ARM: core microcontroller;

[0063] MCU: microcontroller (single-chip computer);

[0064] ICAO: Unique address information of the aircraft consisting of 24-bit binary numbers;

[0065] DAT1: track file ICAO address hash table;

[0066] DAT2: Processing the resulting track file;

[0067] Cockpit Integrated Display: The abbreviation of the aircraft cockpit integrated display, which is used to provide comprehensive information display to the pilot;

[0068] GNSS / RNSS: The specific positioning equipment in the figure can provide navigation and positioning information such as longitude and latitude, altitude, speed, time, etc. for other avionics equipment;

[0069] GNSS: Global Navigation Satellite System;

[0070] RNSS: Radio Navigation Satellite System, satellite radio navigation service, is an implementation form of GNSS for my country's Beidou navigation and positioning system. DETAILED DESCRIPTION

[0071] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0072] In the description of the present invention, the term "for example" is used to mean "used as an example, illustration or explanation". Any embodiment described as "for example" in the present invention is not necessarily to be construed as being more preferred or advantageous than other embodiments. The following description is given to enable any technician in the field to implement and use the present invention. In the following description, details are listed for the purpose of explanation. It should be understood that a person of ordinary skill in the art can recognize that the present invention can be implemented without using these specific details. In other examples, well-known structures and processes will not be elaborated in detail to avoid obscuring the description of the present invention with unnecessary details. Therefore, the present invention is not intended to be limited to the embodiments shown, but is consistent with the widest scope consistent with the principles and features disclosed in the present invention.

[0073] Typical airborne small ADS-B surveillance systems include: Figure 3 The ADS-B signal receiving and processing flow is as follows: Figure 4 As shown, according to the narrowing processing position in the ADS-B signal receiving and processing flow (see Figure 5 There are two current technical solutions to achieve the target reduction. The first method is a first-come-first-served method, and the second method is to reduce the limit of the track file after the track is generated. These two methods and their respective advantages and disadvantages are described in detail in the background technology.

[0074] In order to solve the problems of the prior art, the present invention has a specific solution as described below.

[0075] like Figure 1 and Figure 2 As shown, the automatic correlation surveillance target reduction method based on target quantity sliding window detection includes the following steps:

[0076] S100. Receive the target's ADS-B message and decode it to obtain an ADS-B message.

[0077] S200. Preprocess the ADS-B message. In a message receiving cycle, extract and cache the ICAO address and structured message data in the ADS-B message to form a key-value pair, where the key is the ICAO address and the value is the structured message data; the ICAO address is 24 bits of information in the 112-bit ADS-B message. The ICAO address represents the unique address information of the aircraft composed of 24 bits of binary numbers, also known as the S-mode address. The ICAO address extraction process does not consume too many resources and does not require additional operations. The purpose of message preprocessing based on the ICAO address is to reduce the number of messages that need to be solved, reduce the computational load of message solving and track generation processing, and is a key mechanism to prevent delays and crashes in the receiving system.

[0078] The structured message data content includes aircraft identity and type message, air position message, ground position message, air speed message, and message timestamp. The message timestamp can be used as a sign of whether the message has been updated.

[0079] S300. Store and calculate the track of ADS-B messages. S300 includes:

[0080] S310. Queue and store the ADS-B messages in the message receiving cycle according to the ICAO address to obtain an ADS-B message queue. The queue storage here includes the ICAO address and the ADS-B message, and the ICAO address is the index. The standard message receiving cycle is 1s. It is difficult to set the adjustment step when using the standard message receiving cycle to count the messages. If the step is too large, the MTL may oscillate greatly around the target value. If the step is too small, the speed of approaching the target value may be too slow and cannot keep up with the speed of change of the target number. The present invention uses a sliding window method. Figure 6 As shown, the ADS-B message queue is obtained by queue storage processing of the ADS-B messages in the message receiving cycle according to the ICAO address, including the following steps: the ICAO addresses of all ADS-B messages in the message receiving cycle are sequentially compared with the ICAO address list obtained by statistics in the existing target track file; if there is a matching item in the ICAO address list, the ADS-B message is added to the processing queue, and the ADS-B messages of the same target are stored and updated; if there is no matching item in the ICAO address list, it is determined whether the current target storage quantity exceeds the preset maximum target storage quantity value N; if it exceeds, the ADS-B messages of the targets exceeding the maximum target storage quantity value N are discarded; if it does not exceed, the ADS-B message is added to the processing queue, and the ICAO address of the ADS-B message is stored in the ICAO address list. In the prior art, the general ADS-B In architecture directly discards excess messages, such as Figure 4 shown.

[0081] Specifically, the ICAO address list uses hashing to store ICAO addresses; the ICAO address is hashed to obtain a hash value, which is the address of the storage unit of the ICAO address list. The ICAO address in the storage unit can be compared to determine whether it is repeated. The time complexity of the algorithm is O (1), thereby improving the speed of ICAO address comparison. The ICAO address is represented by a numerical value with a length of 24 bits and a range of 0x000000~0xFFFFFF. Determining whether it is repeated is to determine whether its value is equal. The hash table uses the key-value pair KEY-VALUE to find the storage unit location. Storing the ICAO address is to calculate the ICAO address value to obtain a hash value (a storage location in the hash table). The write operation is to store this ICAO address in the storage unit corresponding to the hash value. The search and comparison operation is similar to the write operation. After calculating the ICAO address value to be searched and obtaining the hash value, find the storage unit corresponding to the hash value, take out the ICAO address value stored therein, and compare it with the ICAO address value to be searched. After the ICAO address list with capacity N is designed using a hash table, it only needs to be calculated once to determine whether the ICAO address is repeated with the ICAO address already stored in the ICAO address list. This is independent of the size of the capacity N, and the algorithm time complexity is O (1). If the traditional comparison method is used, the ICAO address list needs to be traversed and compared, which is related to the size of the ICAO address list capacity N, and the algorithm time complexity is O (N). The actual comparison example is shown in the following table:

[0082] ;

[0083] S311. Perform track-related operations on the ADS-B messages in the ADS-B message queue and maintain the target track file. Maintaining the target track file specifically includes: updating the track file, creating a new track file, and deleting the track file; one flight target corresponds to one track. Specifically, if there is no new ICAO address, that is, there is a matching item in the ICAO address list, directly update the ADS-B message corresponding to the ICAO address; if there is a new ICAO address, that is, there is no matching item in the ICAO address list, establish a new target track based on the ICAO address, and then store the ADS-B message corresponding to the ICAO address; delete the track files that exceed the life cycle management. Generally speaking, if the track of a single target does not receive a new message within a certain period of time (such as 120S), it will be deleted automatically, and the life cycle is not 120s;

[0084] In response to the message sending cycle drive or event drive, the target track message is sent to the data link receiving end; the data link receiving end is one or more of the cockpit CDTI, the UAV ground command center, and the satellite data link ground station. The schematic diagram of the sending and processing of the track file is as follows Figure 5shown.

[0085] S320. Acquire the detection window according to the message receiving cycle interrupt signal, extract all ICAO addresses in the current detection window in the cached ADS-B message and store them in a double linked list; the double linked list storage includes unidirectional circular chain storage and ordinary chain storage, the unidirectional circular chain storage is the unidirectional circular chain storage between each message detection cycle in the detection window, and the ordinary chain storage is the chain storage between each ICAO address in each message detection cycle; each node in the unidirectional circular chain storage stores a pointer to the first ICAO address in each detection cycle; the ordinary chain storage is used to store all ICAO addresses in a single message detection cycle, and can flexibly store the ICAO addresses in the detection cycle to improve the efficiency of sequential retrieval; the ICAO addresses in each detection cycle are stored in different memories, and the number of memories is determined by the length of the detection window, that is, the number of nodes of the unidirectional circular linked list, that is, the number of memories should be set to at least the number of detection cycles in the detection window. The storage depth refers to the maximum number of nodes in an ordinary one-way linked list. The depth of the memory determines the number of ICAO addresses stored in a single cycle, preventing the linked list from expanding without limit and causing memory to exceed the bounds.

[0086] S400. Take out all ICAO addresses in the current detection window, perform deduplication and statistical operations to obtain the number of ICAO addresses, and adjust the decoding sensitivity according to the number of target ICAO addresses; the adjustment of the decoding sensitivity according to the number of target ICAO addresses includes the following steps:

[0087] (1) Determine whether the number of target ICAO addresses exceeds the preset target tolerance. If so, pre-increase the MTL value; otherwise, pre-decrease the MTL value; MTL represents the minimum signal trigger level;

[0088] (2) Perform dynamic range detection on the pre-adjusted MTL value, that is, compare it with the maximum and minimum values ​​preset by the system. If the maximum value is reached, it will not increase further, and if the minimum value is reached, it will not decrease further.

[0089] (3) Adjust the decoding sensitivity according to the MTL value.

[0090] S500. Calculate the system health E, adjust the sliding window parameters according to the calculated system health E, perform sliding window operation on the detection window according to the sliding window parameters, update the double linked list, and repeat step S400 to continuously adjust the decoding sensitivity; the sliding window parameters include the detection window length, the number of memories and the message receiving cycle, T = a×τ, where T represents the detection window length, τ represents the message receiving cycle, and a represents the number of memories. The message receiving cycle is also the message detection cycle, and the detection window length is the length of multiple message receiving cycles, such as Figure 7As shown, in the specific implementation of the present invention, the number of memories is 10, the number of memories can also be regarded as the number of detection cycles, the storage depth is 100, and the detection window contains 10 detection cycles. It can be seen that the number of ICAO addresses in each detection cycle is different.

[0091] In specific applications, the selection of parameters should also refer to the equipment level and system characteristics. The equipment levels include A0-A3, which correspond to 100 target processing capacity, 200 target processing capacity and 400 processing capacity respectively, and have the corresponding report generation capabilities. The system characteristics are the types of aircraft, including slow, supersonic, fixed-wing, rotary, unpowered paragliders, etc. For example, if a paraglider is equipped with A0-level equipment, based on its slow and low-altitude activities, the surrounding aircraft situation changes slowly, and a longer detection window and detection cycle can be selected, and frequent sliding window detection is not required; on the contrary, if it is a large civil aircraft, the speed is fast, there are many aircraft in the surrounding airspace, and the target threat is large. If a lower-level receiver such as A1 (normally A3) is installed, the monitoring capacity is low (200), and the rhythm of sliding window detection needs to be accelerated. The system health can be combined with the characteristics of the equipment and the system for comprehensive consideration to select the appropriate sliding window parameters.

[0092] The message detection cycle is also the message receiving cycle, the interval of the sliding window operation is one message detection cycle, and the step length of the sliding window operation is also one message detection cycle. Specifically, the update of the unidirectional circular chain storage is: the new content written replaces the storage information of the earliest detection cycle in the detection window, and the update of the ordinary chain storage is: according to the updated unidirectional circular chain storage, the ICAO address in the earliest detection cycle in the detection window is replaced with the ICAO address in the new message detection cycle.

[0093] Select preset parameters from the preset sliding window parameter matrix to increase or slow down the speed of sliding window adjustment MTL to match the current application scenario and improve the near-end target detection rate. The system health reflects the matching degree between the target ICAO address and the ICAO address list in the target track file. More intuitively, it is to compare the ICAO address list from the solved target track file with the target ICAO address obtained in the sliding window operation, and calculate their overlap. The lower the health, the smaller the overlap, indicating that the system tracking does not track the target well.

[0094] The sliding window parameters are adjusted according to the calculated system health E as follows: when the health decreases, T and τ are reduced, so that the detection speed can be accelerated and the target tracking rate can be improved; when the health increases, T and τ are increased, so that the detection speed can be slowed down, system resources can be saved and system power consumption can be reduced. For example, a small aircraft is equipped with A0-level equipment, which can handle 100 targets within a range of 100 kilometers. When there are fewer aircraft near the training ground, the 100 targets tracked and displayed are distant aircraft; if the training ground adds 20 aircraft at the same time in a short period of time, and the aircraft is turned on for training, the system processes the track and maintains the track for hundreds of seconds. The nearby aircraft cannot be tracked and processed by the system in the first time, but is detected by the system sliding window detection mechanism, and the calculated health decreases. Therefore, it is necessary to reset or modify the sliding window parameters so that these targets can form track files in time for the back-end display terminal to display to the pilot.

[0095] In more extreme cases, a group of fighter jets flying in formation suddenly fly over a low altitude near a small, slow-speed aircraft in training. When the monitoring capacity of the equipment has reached the upper limit (such as 100), these fighter jets are only detected by the system when they are close, and they will not be tracked and transmitted to the back-end display terminal in time. However, according to the health calculation, this problem is found, so it is necessary to speed up the sliding window detection frequency to adapt to this change, and reset the track file at the same time to give priority to tracking these high-threat targets. When these aircraft groups fly out of the monitoring range, the sliding window detection frequency can be gradually lowered according to the calculated health while maintaining the health, so as to save system energy consumption.

[0096] The steps for calculating the system health are as follows:

[0097] (1) Calculate the health of a single target:

[0098] ;

[0099] in, Indicates the health of a single target, status indicates the status of the target in the track file, with the initial state being 2, the acquisition state being 1, and the tracking state being 0. aic indicates the time deviation value of the aircraft identity and type message, with an update rate of 5 seconds / time, and an initial value of 0; ap indicates the time deviation value of the air position message, with an update rate of 0.5 seconds / time, and an initial value of 0; sp indicates the time deviation value of the ground position message, with an update rate of 5 seconds / time, and an initial value of 0; av indicates the time deviation value of the air speed message, with an update rate of 0.5 seconds, and an initial value of 0; when ap exists, the sp value is 0, and when sp exists, the ap value is 0; the specific calculation of the time deviation value of each message is as follows:

[0100] aic = (current time - timestamp of the most recent message) / 5

[0101] ap = (current time - timestamp of the most recent message) / 0.5

[0102] sp = (current time - timestamp of the most recent message) / 5

[0103] av = (current time - timestamp of the most recent message) / 0.5;

[0104] The health of all targets is obtained by calculating the health of a single target, forming the target health matrix w n ;

[0105] (2) Calculate system health E:

[0106] ;

[0107] Among them, normalization means normalization processing; w n represents the target health matrix; p represents the weight vector, , the dimension is 5*1; n represents the number of ICAO addresses of the target in the track file; represents the load factor, = Number of ICAO addresses in track file target / system tolerance, The result range is 0~1.2; k represents the sliding window target address matching degree, k=1-diff (sliding window target ICAO address Track file ICAO address), the result range of k is 0~1.

[0108] This specific embodiment also discloses an automatic correlation surveillance target reduction system based on target number sliding window detection. The system principle block diagram is shown in the figure, and this system corresponds to the automatic correlation surveillance target reduction method based on target number sliding window detection proposed by the present invention.

[0109] The goal of system design is to ensure that all targets within the close range are "measured", so the track file capacity should be larger than the detection limit number to ensure that "all targets that should be measured are measured" within the system processing capacity. Therefore, the target limit number and the track file capacity are configured with a difference. For example: the detection limit number is set to 100 targets, the system processing capacity is 130+, and the track file capacity is set to 120. When using the sliding window detection sensitivity adjustment mechanism, the number of detected targets may be 97, 106, 103, 138 and other values. The difference of 20 targets between the track file capacity and the limit number can ensure that all targets within the current detection range are measured.

[0110] Combining the sliding window method and the difference configuration, the sliding window detection algorithm can be expressed using the following pseudo code:

[0111] Adj = 5

[0112] TaskTick_0.1s [

[0114] if TargetAmount > 100 + Adj:

[0115] MTL – 1

[0116] if TargetAmount < 100 - Adj:

[0117] MTL +1 ]

[0119] In the specific implementation, in the scenario where the rate of change is ≤10 flights / second, the sliding window sensitivity adjustment mechanism with default parameters can better achieve the target quantity limit. When the software simulates the input of 100 flights / second and the linear simulation of the rate of change is ±1 flight / 0.1 second (i.e. ±10 flights / second), the sensitivity tracking adjustment can be completed within 1 second, effectively ensuring the target monitoring range of the receiving system; it can be seen that the adjustment speed of the present invention is relatively fast.

[0120] When the software simulates the input of 200 static targets, the processing tolerance parameter is set to 100 and the track file capacity is 120. After the device is running, it can finally process only the 100 closest tolerance targets based on the distance.

[0121] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0122] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. Automatic correlation surveillance target reduction method based on target quantity sliding window detection, characterized in that: The steps include: S100. Obtain the target ADS-B message; S200. Preprocess the ADS-B message, extract and cache the ICAO address and structured message data in the ADS-B message in a message receiving cycle to form a key-value pair, the key is the ICAO address, and the value is the structured message data; S300. Store and calculate the track of ADS-B messages. S300 includes: S310. Queue storage and processing of ADS-B messages within the message receiving cycle according to the ICAO address to obtain an ADS-B message queue; S311. Perform track-related operations on the ADS-B messages in the ADS-B message queue and maintain the target track file. Maintaining the target track file specifically includes: updating the track file, creating a new track file, and deleting the track file; in response to the message sending cycle drive or event drive, sending the target track message to the data link receiving end; S320. Acquire the detection window according to the message receiving cycle interrupt signal, extract all ICAO addresses in the current detection window in the cached ADS-B message and store them in a double linked list; the double linked list storage includes unidirectional circular chain storage and ordinary chain storage, the unidirectional circular chain storage is the unidirectional circular chain storage between each message detection cycle in the detection window, and the ordinary chain storage is the chain storage between each ICAO address in each message detection cycle; each node in the unidirectional circular chain storage stores the pointer of the first ICAO address in each message detection cycle; S400. Take out all ICAO addresses in the current detection window, perform deduplication and statistical operations to obtain the number of ICAO addresses, and adjust the decoding sensitivity according to the number of target ICAO addresses, thereby completing the target limit reduction; The method of performing queue storage processing on the ADS-B messages in the message receiving period according to the ICAO address to obtain the ADS-B message queue includes the following steps: sequentially comparing the ICAO addresses of all ADS-B messages in the message receiving period with the ICAO address list obtained by statistics in the existing target track file; if there is a matching item in the ICAO address list, adding the ADS-B message to the processing queue, and storing and updating the ADS-B message of the same target; if there is no matching item in the ICAO address list, judging whether the current target storage quantity exceeds the preset maximum target storage quantity value N; if so, discarding the ADS-B message of the target exceeding the maximum target storage quantity value N; if not, adding the ADS-B message to the processing queue, and storing the ICAO address of the ADS-B message in the ICAO address list.

2. The automatic correlation surveillance target reduction method based on target quantity sliding window detection according to claim 1 is characterized in that: The method further comprises the steps of: S500. Calculate the system health E. If the system health is lower than the threshold, adjust the sliding window parameters according to the calculated system health E, perform sliding window operation on the detection window according to the sliding window parameters, update the double linked list, and repeat step S400 to continuously adjust the decoding sensitivity; the sliding window parameters include the detection window length, the number of memories and the message receiving cycle, , where T represents the detection window length, Indicates the message receiving cycle, and a indicates the number of memories.

3. The automatic correlation surveillance target reduction method based on target quantity sliding window detection according to claim 1 is characterized in that: The ICAO address list uses hashing to store ICAO addresses.

4. The automatic correlation surveillance target reduction method based on target quantity sliding window detection according to claim 1 is characterized in that: Maintaining the target track file in S311 includes: If there is no new ICAO address, that is, there is a matching item in the ICAO address list, the ADS-B message corresponding to the ICAO address is directly updated; if there is a new ICAO address, that is, there is no matching item in the ICAO address list, a new target track based on the ICAO address is established, and then the ADS-B message corresponding to the ICAO address is stored; the track files that exceed the life cycle management are deleted.

5. The automatic correlation surveillance target reduction method based on target quantity sliding window detection according to claim 1 is characterized in that: The data link receiving end is one or more of the cockpit CDTI, the UAV ground command center, and the satellite data link ground station.

6. The automatic correlation surveillance target reduction method based on target quantity sliding window detection according to claim 1 is characterized in that: The decoding sensitivity adjustment according to the number of target ICAO addresses comprises the following steps: (1) Determine whether the number of target ICAO addresses exceeds the preset target tolerance. If so, pre-increase the MTL value; otherwise, pre-decrease the MTL value; MTL represents the minimum signal trigger level; (2) Perform dynamic range detection on the pre-adjusted MTL value, that is, compare it with the maximum and minimum values ​​preset by the system. If the maximum value is reached, it will not increase further, and if the minimum value is reached, it will not decrease further. (3) Adjust the decoding sensitivity according to the MTL value.

7. The automatic correlation surveillance target reduction method based on target quantity sliding window detection according to claim 2 is characterized in that: The specific method of adjusting the sliding window parameters according to the calculated system health E is as follows: when the health decreases, reduce T and ; As health increases, T and .

8. The automatic correlation surveillance target reduction method based on target quantity sliding window detection according to claim 2 or 7, characterized in that: The steps for calculating the system health in S500 are as follows: (1) Calculate the health of a single target: ； in, Indicates the health of a single target, status indicates the status of the target in the track file, with the initial state being 2, the acquisition state being 1, and the tracking state being 0. aic indicates the time deviation value of the aircraft identity and type message, with an update rate of 5 seconds / time, and an initial value of 0; ap indicates the time deviation value of the air position message, with an update rate of 0.5 seconds / time, and an initial value of 0; sp indicates the time deviation value of the ground position message, with an update rate of 5 seconds / time, and an initial value of 0; av indicates the time deviation value of the air speed message, with an update rate of 0.5 seconds, and an initial value of 0; when ap exists, the sp value is 0, and when sp exists, the ap value is 0; the specific calculation of the time deviation value of each message is as follows: aic = (current time - timestamp of the most recent message) / 5 ap = (current time - timestamp of the most recent message) / 0.5 sp = (current time - timestamp of the most recent message) / 5 av = (current time - timestamp of the most recent message) / 0.5; The health of all targets is obtained by calculating the health of a single target, forming the target health matrix w n； (2) Calculate system health E: ； Among them, normalization means normalization processing; w n represents the target health matrix; p represents the weight vector, , the dimension is 5*1; n represents the number of ICAO addresses of the target in the track file; represents the load factor, = Number of ICAO addresses in track file target / system tolerance, The result range is 0~1.2; k represents the sliding window target address matching degree, k=1-diff (sliding window target ICAO address Track file ICAO address), the result range of k is 0~1.

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