A method and apparatus for reducing false alarms due to asynchronous interference in an airborne collision avoidance system.

Abstract

This invention proposes a method and apparatus for reducing false alarms caused by asynchronous interference in an airborne collision avoidance system. Based on the principle of not affecting the normal function of the airborne collision avoidance system and meeting standard requirements, this invention filters out asynchronous interference signals to a certain extent by performing "intensity-distance" correlation judgment on the response signals received by the airborne collision avoidance system and adding a false target confirmation process within the minimum protection distance, thereby reducing the probability of asynchronous interference signals forming false targets and false alarms.

Description

Technical Field

[0001] This invention belongs to the field of avionics technology, specifically relating to a method and apparatus for reducing false alarms caused by asynchronous interference in an airborne collision avoidance system. Background Technology

[0002] Airborne Collision Avoidance System (ACAS) is an essential airborne device for preventing dangerous close-in encounters and collisions between aircraft. It operates independently of ground-based traffic control systems. Using the same operating methods and communication links as secondary radar, this system effectively tracks and monitors aircraft equipped with transponders in nearby airspace. It acquires and calculates information such as the target aircraft's distance, speed, altitude, and bearing, generating traffic alerts based on the target's trajectory or, further, decision alerts based on the threat level. This promptly alerts pilots to take evasive action and prevent collisions with other aircraft. Recent flight practice has demonstrated that ACAS is the last line of defense against mid-air collisions. It utilizes air-to-air communication between aircraft, overcoming the limitations of ground-based secondary radar's air-to-ground communication for traffic control. It plays a crucial role in responding to dangerous close-in encounters and preventing collisions.

[0003] When the airborne collision avoidance system is in operation, it first sends an interrogation signal to other aircraft equipped with air traffic control transponders in the airspace. Then, it waits for a period of time to receive the response signals sent by the other aircraft's air traffic control transponders in response to the interrogation signal, forming an interrogation-response link between the system and other aircraft. This waiting time is called the reception decoding window. When the response signals of several consecutive processing cycles meet the distance and altitude correlation conditions, the airborne collision avoidance system identifies it as an aircraft target and establishes a tracking trajectory.

[0004] In practical use, airborne collision avoidance systems (AOLs) often have their antennas installed close to other L-band devices, and various electronic devices within the aircraft operate in parallel, leading to increasingly complex electromagnetic signals in the airspace. As aircraft density or the number of secondary radar interrogations increases, the number of responses to other aircraft AOLs or secondary radars also increases. For the aircraft's own AOL, these response signals are asynchronous interference signals. Their arrival time has a certain probability of falling within the AOL's receiving and decoding window. When these asynchronous interference signals meet the target establishment conditions, the AOL will identify them as aircraft targets, establishing a tracking trajectory and creating false targets and false alarms, thus affecting the pilot's understanding and judgment of the airspace situation.

[0005] To meet the needs of next-generation military and civilian air traffic control systems for providing aircraft with traffic situation awareness and auxiliary decision-making and warning services throughout the entire flight and mission phases, thereby improving pilots' accurate judgment of airspace traffic situations and effectively enhancing the flight safety performance of military and civilian aircraft, it is urgent to study methods to reduce the probability of false targets and false alarms caused by asynchronous response interference signals in the airspace to the onboard collision avoidance system. Summary of the Invention

[0006] This invention provides a method and apparatus for reducing false alarms caused by asynchronous interference in an airborne collision avoidance system.

[0007] The first aspect of this invention provides a method for reducing false alarms due to asynchronous interference in an airborne collision avoidance system, comprising:

[0008] S1. In the preset direction, the airborne collision avoidance system sends an inquiry request at a preset cycle;

[0009] S2. Upon receiving a response message, if the distance indication corresponding to the response message is not a target to be tracked, determine whether the relationship between the strength of the response message and the preset direction and distance conforms to the preset relationship; if yes, proceed to S3; if no, proceed to S6.

[0010] S3. Send a supplementary inquiry request within this cycle;

[0011] S4. Upon receiving the response information corresponding to the supplementary inquiry request, determine whether the distance and height of all response information received in this cycle are within their respective relevant window ranges; if not, proceed to S6; if yes, proceed to S5.

[0012] S5. Confirm that the response information is valid;

[0013] S6. Determine that the response information is asynchronous interference.

[0014] Optionally, after S2 and before S3, the method for reducing asynchronous interference false alarms by the airborne collision avoidance system further includes:

[0015] S30. Determine whether the distance corresponding to the response information is less than the minimum protection distance; if it is less, proceed to S3; if it is not less, proceed to S5.

[0016] Optionally, the minimum protection distance is determined based on the number of targets being tracked.

[0017] Optionally, the minimum protection distance is inversely proportional to the number of targets being tracked.

[0018] Optionally, the preset relationship includes: the strength of the response information decreases as the distance increases;

[0019] The intensity of the response information is within the range corresponding to the preset direction; the intensity value is the highest corresponding to the 0° direction.

[0020] Optionally, a supplementary inquiry request may be sent during this period, including:

[0021] Two supplementary inquiry requests were sent during this period.

[0022] Optionally, determine whether the distance and height of all response messages received within the current period are within their respective relevant window ranges, including:

[0023] Determine if the differences in distance and height between all received response messages within the current period are within a preset window range.

[0024] A second aspect of the present invention provides an apparatus for reducing false alarms caused by asynchronous interference in an airborne collision avoidance system, for performing the method as described in any one of the first aspects.

[0025] This invention provides a method and apparatus for reducing false alarms caused by asynchronous interference in an airborne collision avoidance system. Based on the distinction between normal response signals and asynchronous interference response signals, and adhering to the principle of not affecting the normal function of the airborne collision avoidance system and meeting standard requirements, the method filters out asynchronous interference response signals by using a "signal strength-distance" correlation window and increasing the target confirmation within the minimum distance. This reduces the probability of asynchronous interference response signals in the airborne collision avoidance system, establishes target tracking trajectories, and causes false targets or false alarms. It provides pilots with accurate air traffic situation information, improving flight safety and reliability. Attached Figure Description

[0026] Figure 1 A block diagram is designed for a method to reduce false alarms caused by asynchronous interference in airborne collision avoidance systems;

[0027] Figure 2 This is a schematic diagram of the "signal strength-distance" related window;

[0028] Figure 3 Workflow diagram for identifying targets within the minimum distance. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] The features and illustrative embodiments of various aspects of the present invention will now be described in detail. Numerous specific details are set forth in the following detailed description to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The invention is by no means limited to any specific setups and methods set forth below, but covers any improvements, substitutions, and modifications to structures, methods, and devices without departing from the spirit of the invention. Well-known structures and techniques are not shown in the drawings and the following description to avoid unnecessarily obscuring the invention.

[0031] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited in each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0032] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0033] The technical solution adopted in this invention is a method for reducing false alarms due to asynchronous interference in an airborne collision avoidance system, such as... Figure 1 As shown, this method first records the signal strength of other aircraft's response signals received by the onboard collision avoidance system and the distance and bearing between the onboard system and other aircraft using a data recording device. Then, it trains the relationship between response signal strength and distance to derive a correlation window for "signal strength-distance" at different bearings. During the operation of the onboard collision avoidance system, the "signal strength-distance" correlation window is used to filter the strength of the response signals received in each monitoring cycle and the distance obtained from the ranging algorithm. Response signals that do not meet the correlation window are filtered out, while those that do are sent to the subsequent monitoring and tracking processing flow. In the monitoring and tracking processing flow, a minimum protection distance and a "distance & altitude" correlation window are set. For other aircraft within the minimum protection distance range, two confirmation processes are added in each monitoring cycle. Response signals that meet the "distance & altitude" correlation window threshold are used to establish the tracking trajectory; response signals that do not meet the "distance & altitude" correlation window threshold are not used in the tracking trajectory establishment process.

[0034] On the one hand, in the "signal strength-distance" correlation window, it is necessary to consider the different spatial attenuation of signal strength between the aircraft and other aircraft at different azimuths. Therefore, it is necessary to establish a "signal strength-distance" correlation window with distance from 0 to horizontal monitoring distance D at different azimuths within -180° to 180°, with azimuth resolution of Δφ and distance resolution of Δd.

[0035] On the other hand, during the confirmation process within the minimum protection distance, the initial minimum protection distance and distance-height window threshold can be set through external configuration, and the load of the system in the current processing cycle (i.e., the ratio of task processing time in the current processing cycle to the entire processing cycle) can be monitored in real time. When the system processing load is too high, the minimum protection distance can be reduced, and when the system processing load is low, the minimum protection distance can be increased, so as to achieve dynamic adjustment of the minimum protection distance without affecting the normal processing function of the airborne collision avoidance system.

[0036] Finally, the response signal confirmed by the "signal strength-distance" related window threshold and the "distance & altitude" related window within the minimum protection distance is used to establish the target's tracking trajectory. The target aircraft that establishes the tracking trajectory outputs the target's distance, altitude, bearing and other information to the external integrated display system.

[0037] Appendix Figure 1 A block diagram of an integrated alarm method for flight environment monitoring is shown. The method includes a signal strength-distance correlation window generation unit, a signal strength-distance correlation window signal processing unit, and a target confirmation unit within the minimum protection distance.

[0038] The "signal strength-distance" correlation window generation unit trains the "signal strength-distance" correlation model using recorded values ​​of the response signal strength, target relative bearing, and target relative distance of multiple real target aircraft that have been tracked, and obtains a correlation threshold table for signal strength and the distance between the local aircraft and the target aircraft at different bearings.

[0039] During the operation of the airborne collision avoidance system, after the current processing cycle transmits an interrogation signal to a target aircraft, the system performs signal strength sampling, target direction finding, and target ranging on the response signal received within the response decoding window of the interrogation. This yields the target aircraft's response signal strength sampling value, the target aircraft's bearing relative to the system, and the target aircraft's distance relative to the system. Then, the system performs a lookup comparison with the corresponding window threshold table for "signal strength-distance". Response signals that meet the window threshold are retained and sent to the target confirmation unit within the minimum protection distance for further processing, while response signals that do not meet the window threshold are filtered out.

[0040] The target confirmation unit within the minimum protection distance first receives the externally configured distance & altitude confirmation window and the initial minimum protection distance setting. In each monitoring cycle, it adds several additional interrogations to target aircraft within the minimum protection distance, obtaining corresponding additional response signals. Then, based on the distance & altitude window, it performs target confirmation on the response signals of the current processing cycle. If the response signals in the current processing cycle are correlated, they are used for target tracking trajectory establishment; otherwise, they are not used. Target tracking trajectory establishment is performed according to the same conditions specified in the standards of this professional field. In each monitoring cycle, the target confirmation unit within the minimum protection distance monitors the system's task processing load to dynamically adjust the minimum protection distance setting.

[0041] Appendix Figure 2 This figure shows a specific example of a "signal strength-distance" related window threshold table. The figure only shows the threshold window relationship between signal strength and relative distance for the local aircraft and the target aircraft at different bearings. Here, Δφ represents the bearing resolution; D represents the maximum monitoring range of the airborne collision avoidance system; Δd represents the distance resolution; S(i,j) represents the response signal strength at bearing i and distance j; and ΔS(i,j) is the signal strength window threshold at bearing i and distance j.

[0042] Appendix Figure 3This diagram illustrates the workflow of target confirmation within the minimum protection distance. Before the airborne collision avoidance system (APL) operates, the distance & altitude confirmation window threshold and the initial minimum protection distance are set via external configuration equipment. During normal operation of the APL, upon receiving a response signal from a target aircraft input from the "signal strength-distance" correlation window signal processing unit, target ranging is first performed. If the target aircraft's distance relative to the system is outside the minimum protection distance, the target tracking trajectory establishment process is initiated directly; if the target aircraft's distance relative to the system is within the minimum protection distance, the target confirmation process is initiated. The APL performs additional interrogation on the target aircraft in the current cycle, obtaining corresponding additional response signals. If the response signal in the current processing cycle does not meet the distance & altitude correlation threshold, the target's response signal for the current cycle is filtered out; if the response signal in the current processing cycle meets the distance & altitude correlation threshold, the target aircraft is considered a real aircraft, and the target aircraft's response signal for the current cycle is sent to the target tracking trajectory establishment process. If the response signals of the target aircraft meet the target tracking trajectory establishment conditions for several consecutive processing cycles, a tracking trajectory for the target aircraft is established, and the target information is output. If the target tracking trajectory establishment conditions are not met, a tracking trajectory for the target is not established. Finally, the processing load of the entire system in the current cycle is monitored. If the system processing load is higher than the upper threshold, the minimum protection distance setting is reduced; if the system processing load is lower than the lower threshold, the minimum protection distance setting is increased; if the system processing load is between the upper and lower thresholds, the minimum protection distance setting for the current cycle remains unchanged to ensure that the target confirmation process within the minimum protection distance does not affect the normal function of the airborne collision avoidance system.

[0043] The above description is merely a further embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope disclosed in the present invention, based on the technical solution and concept of the present invention, shall fall within the scope of protection of the present invention.

Claims

1. A method for reducing false alarms due to asynchronous interference in an airborne collision avoidance system, characterized in that, include: S1. In the preset direction, the airborne collision avoidance system sends an inquiry request at a preset cycle; S2. Upon receiving a response message, if the distance indication corresponding to the response message is not a target to be tracked, determine whether the relationship between the strength of the response message and the preset direction and distance conforms to the preset relationship; if yes, proceed to S3; if no, proceed to S6. S3. Send a supplementary inquiry request within this cycle; S4. Upon receiving the response information corresponding to the supplementary inquiry request, determine whether the distance and height of all response information received in this cycle are within their respective relevant window ranges; if not, proceed to S6; if yes, proceed to S5. S5. Confirm that the response information is valid; S6. Determine that the response information is asynchronous interference.

2. The method for reducing asynchronous interference false alarms in an airborne collision avoidance system according to claim 1, characterized in that, After S2 and before S3, the method further includes: S30. Determine whether the distance corresponding to the response information is less than the minimum protection distance; if it is less, proceed to S3; if it is not less, proceed to S5.

3. The method for reducing asynchronous interference false alarms in an airborne collision avoidance system according to claim 1, characterized in that, The minimum protection distance is determined based on the number of targets being tracked.

4. The method for reducing asynchronous interference false alarms in an airborne collision avoidance system according to claim 1, characterized in that, The minimum protection distance is inversely proportional to the number of targets being tracked.

5. The method for reducing asynchronous interference false alarms in an airborne collision avoidance system according to claim 1, characterized in that, The pre-defined relationship includes: the strength of the response information decreases as the distance increases; The intensity of the response information is within the range corresponding to the preset direction; the intensity value is the highest corresponding to the 0° direction.

6. The method for reducing asynchronous interference false alarms in an airborne collision avoidance system according to claim 1, characterized in that, This week, a supplementary inquiry request will be sent, including: Two supplementary inquiry requests were sent during this period.

7. The method for reducing asynchronous interference false alarms in an airborne collision avoidance system according to claim 1, characterized in that, Determine whether the distance and height of all response messages received within this period are within their respective relevant window ranges, including: Determine if the differences in distance and height between all received response messages within the current period are within a preset window range.

8. A device for reducing false alarms caused by asynchronous interference in an airborne collision avoidance system, characterized in that, Used to perform the method as described in any one of claims 1-7.

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