阅读说明：本技术 一种星基ads-b的目标验证方法 (Target verification method of satellite-based ADS-B ) 是由 安强 李家蓬 黄枭 牟光红 陈琴 于 2021-09-03 设计创作，主要内容包括：本发明公开了一种星基ADS-B的目标验证方法,包括：步骤一,对星基ADS-B系统架构和报文进行设计；步骤二,基于步骤一中设计的所述星基ADS-B系统架构和报文进行基于TDOA算法架构的星座设计；步骤三,基于步骤二中所述星座设计,在星基ADS-B数据中心基于TDOA架构进行计算,并通过与ADS-B系统报告的位置进行比对,判断目标的真实性和有效性。本发明从根本上解决了星基ADS-B目标有效性验证的问题,可有效过滤虚假目标和无效目标,保证了ADS-B数据的正确性和有效性,保障了管制安全。(The invention discloses a target verification method of a satellite-based ADS-B, which comprises the following steps: designing a satellite-based ADS-B system architecture and a message; secondly, carrying out constellation design based on a TDOA algorithm architecture based on the satellite-based ADS-B system architecture and the message designed in the first step; and step three, based on the constellation design in the step two, calculating on the basis of a TDOA framework in a satellite-based ADS-B data center, and comparing the position reported by the ADS-B system to judge the authenticity and the effectiveness of the target. The invention fundamentally solves the problem of validity verification of the satellite-based ADS-B target, can effectively filter false targets and invalid targets, ensures the correctness and validity of ADS-B data, and ensures the control safety.)

1. A target verification method of satellite-based ADS-B is characterized by comprising the following steps:

designing a satellite-based ADS-B system architecture and a message;

secondly, carrying out constellation design based on a TDOA algorithm architecture based on the satellite-based ADS-B system architecture and the message designed in the first step;

and step three, based on the constellation design in the step two, calculating on the basis of a TDOA framework in a satellite-based ADS-B data center, and comparing the position reported by the ADS-B system to judge the authenticity and the effectiveness of the target.

2. The method for target validation of satellite-based ADS-B according to claim 1, wherein in step one, the design of the satellite-based ADS-B system architecture comprises the steps of: the aircraft transmits the ADS-B message to a plurality of satellites by using air-to-air communication, and then transmits the ADS-B message to a satellite-based ADS-B data center by using a plurality of satellites through inter-satellite-ground communication.

3. The method for target validation of satellite-based ADS-B according to claim 1, wherein in step one, the designing of the satellite-based ADS-B system architecture includes implementing satellite multiple coverage; the message design comprises the steps of realizing satellite time synchronization, message time marking, message attribute marking and transmission delay balance.

4. The target verification method of the satellite-based ADS-B according to claim 1, wherein in the second step, the constellation design includes a constellation design with constellation parameters of 7, 12, 30, 15, a height of 1000Km, and an inclination angle of 85 °; in the constellation design, the ground coverage area of the satellite is a circle, and the coverage area can be calculated through the geocentric half opening angle and the diameter of the coverage area, and the geocentric half opening angle of the coverage areaAnd the earth's surfaceThe surface coverage area diameter D is:

wherein Re is the earth radius, and when the orbit height is h and the ground elevation angle is epsilon, the half cone angle of the satellite view field is alpha.

5. The method for target verification of satellite-based ADS-B according to any of claims 1-4, wherein the calculation based on TDOA architecture in the satellite-based ADS-B data center in step three for the case of double satellite coverage comprises the steps of:

s31, searching two pieces of message information received by two satellites receiving the same message sent by the same target through a ground data center;

s32, calculating the time difference TDOA1 between the same message of the target and two satellites according to the time data in the two messages;

s33, according to the following formula (a), obtaining a hyperboloid formula of the time difference between the target and the two satellites;

in the formula (x)₀,y₀,z₀) As the spatial location coordinates of the master station, (x, y, z) as the spatial location coordinates of the flying target, (x)_i,y_i,z_i) Is the spatial position coordinate of the ith secondary station, r₀Distance of the master station from the flying target, r_iIs the distance between the ith secondary station and the flying target, c is the propagation speed of the electromagnetic wave in the space, and deltar_iFor the difference between the distance of the flying object from the primary station to the ith secondary station, Delta T_iResponse signal arrival to master station for flying targetTime difference from arrival at the ith secondary station;

s34, calculating the minimum distance from the ADS-B report position point to the hyperboloid, wherein the calculation steps are as follows;

converting the TDOA equation in the formula (a) into a constraint equation G (x, y, z) of 0, (x)₀,y₀,z₀) For ADS-B report points, the problem of finding the minimum value from ADS-B target report points to hyperboloid is converted into the problem of finding the target functionThe minimum value of (d) is calculated by using a Lagrange multiplier method;

s35, determining a distance threshold value epsilon according to the time error precision on the satellite_dIf the minimum distance between the ADS-B report position and the hyperboloid is larger than the threshold, the target is false, otherwise, confidence is set for the target.

6. The method for target verification of satellite-based ADS-B according to any of claims 1-4, wherein the step three of calculating the satellite-based ADS-B data center based on the TDOA architecture for triple satellite coverage comprises the steps of:

SS31, searching three satellites through the ground data center to receive three message messages of the same message sent by the same target;

the SS32 calculates time difference values TDOA1 and TDOA2 of the same message of the target reaching three satellites according to the time data in the three message information;

SS33, calculating two position points according to the following formula (a), wherein one is a real target position and the other is a false target position;

SS34, whether the target current altitude information obtained by using other information accords with the flying altitude of the aircraft, and eliminates false positions;

SS35 calculating ADS-B report position point and TDOA calculated real position pointA distance d of; if the distance d exceeds the distance threshold value epsilon_dThe target is identified as a false target, otherwise, the target is identified as a real target.

7. The method for target verification of satellite-based ADS-B according to any of claims 1-4, wherein the step three of calculating the satellite-based ADS-B data center based on the TDOA architecture for the case of coverage of four or more satellites comprises the steps of: and resolving to obtain the target position by utilizing a Chan algorithm and a Taylor series algorithm.

8. The target verification method of satellite-based ADS-B according to claim 7, comprising the steps of: calculating the distance between the target position point obtained by resolving by using a Chan algorithm and a Taylor series algorithm and the ADS-B report position point, and if the distance exceeds a distance threshold value epsilon_dThe target is identified as a false target, otherwise, the target is identified as a real target.

9. The target validation method of satellite-based ADS-B according to claim 3, wherein the multiple overlays comprise at least two overlays; and the satellite time synchronization comprises time synchronization with a GNSS; the message time marking comprises the steps of obtaining time information from a satellite through a design interface between the ADS-B load and the satellite, and marking the arrival time of the ADS-B message when the ADS-B message is received; and the transmission delay equalization comprises that the same message received by different satellites is ensured by an inter-satellite-ground communication network through a designed routing algorithm, and finally reaches the delay equalization of the satellite-based ADS-B data center and meets the system delay requirement.

Technical Field

The invention relates to the technical field of satellite-based ADS-B, in particular to a target verification method of satellite-based ADS-B.

Background

In recent years, although ADS-B is popularized and applied quickly in the world, the system still belongs to a typical foundation monitoring system and has inherent space-time limitation, namely, ADS-B base stations still belong to the line-of-sight work and are limited by terrain environment, and monitoring airspace coverage is insufficient; in addition, with the continuous development of air transportation industry and the continuous improvement of aircraft performance, new characteristics can appear in future military and civil aviation flight activities: the flying units are large in number, high in density, multiple in types, high in speed and strong in randomness; the monitoring airspace has wide requirement range, high precision, good stability and the like, and provides higher updating requirements for the development of future aviation monitoring application. By carrying ADS-B receiving equipment on a low-orbit satellite, the characteristics of global coverage, no terrain shielding and the like of the satellite are utilized, and the real-time continuous seamless monitoring on global flights can be realized. In recent years, relevant research and test of the satellite-based ADS-B system are carried out at home and abroad.

By carrying ADS-B receiving equipment on a low-orbit satellite, the characteristics of global coverage, no terrain shielding and the like of a satellite system are utilized, and real-time continuous seamless monitoring on global flights can be realized. In recent years, relevant research and verification test work of a satellite-based ADS-B system is carried out at home and abroad. The satellite system comprises a satellite-based ADS-B system of Aireon Canada, a PROBE-V satellite of European space agency, and the like, and domestic 'aerospace satellite No. 1' developed by Jiuzhou air traffic control science and technology Limited liability company in Sichuan and Beijing aerospace university, and 'Tiantu No. 3' developed by national defense science and technology university. According to the requirements of China civil aviation, before ADS-B access automation operation, authenticity and validity of the ADS-B access automation operation are verified. After the satellite-based ADS-B networking is carried out and data services are developed for control operation, verification of target validity and authenticity must be provided.

At present, the research of the satellite-based ADS-B in China is in a starting stage, and no complete solution is provided for validity verification of the satellite-based ADS-B data; existing TDOA-based target validity verification also does not propose a solution for the time of receipt of two target signals.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a target verification method of a satellite-based ADS-B, which fundamentally solves the problem of validity verification of the satellite-based ADS-B target, can effectively filter false targets and invalid targets, ensures the correctness and validity of ADS-B data, ensures the control safety and the like.

The purpose of the invention is realized by the following scheme:

a target verification method of satellite-based ADS-B comprises the following steps:

designing a satellite-based ADS-B system architecture and a message;

secondly, carrying out constellation design based on a TDOA algorithm architecture based on the satellite-based ADS-B system architecture and the message designed in the first step;

and step three, based on the constellation design in the step two, calculating on the basis of a TDOA framework in a satellite-based ADS-B data center, and comparing the position reported by the ADS-B system to judge the authenticity and the effectiveness of the target.

Further, in step one, the design of the satellite-based ADS-B system architecture includes the steps of: the aircraft transmits the ADS-B message to a plurality of satellites by using air-to-air communication, and then transmits the ADS-B message to a satellite-based ADS-B data center by using a plurality of satellites through inter-satellite-ground communication.

Further, in the first step, the designing the satellite-based ADS-B system architecture includes implementing satellite multiple coverage; the message design comprises the steps of realizing satellite time synchronization, message time marking, message attribute marking and transmission delay balance.

Further, in step two, the constellation design includes a constellation design with constellation parameters of 7, 12, 30, 15, a height of 1000Km and an inclination angle of 85 °; in the constellation design, the ground coverage area of the satellite is a circle, and the coverage area can be calculated through the geocentric half opening angle and the diameter of the coverage area, and the geocentric half opening angle of the coverage areaAnd the earth's surface footprint diameter D are:

wherein Re is the earth radius, and when the orbit height is h and the ground elevation angle is epsilon, the half cone angle of the satellite view field is alpha.

Further, for the case of dual satellite coverage, the computing at the satellite-based ADS-B data center based on the TDOA architecture in step three includes the steps of:

s31, searching two pieces of message information received by two satellites receiving the same message sent by the same target through a ground data center;

s32, calculating the time difference TDOA1 between the same message of the target and two satellites according to the time data in the two messages;

s33, according to the following formula (a), obtaining a hyperboloid formula of the time difference between the target and the two satellites;

in the formula (x)₀,y₀,z₀) As the spatial location coordinates of the master station, (x, y, z) as the spatial location coordinates of the flying target, (x)_i,y_i,z_i) Is the spatial position coordinate of the ith secondary station, r₀Distance of the master station from the flying target, r_iIs the distance between the ith secondary station and the flying target, c is the propagation speed of the electromagnetic wave in the space, and deltar_iFor the difference between the distance of the flying object from the primary station to the ith secondary station, Delta T_iThe time difference between the flight target response signal arriving at the main station and arriving at the ith secondary station is obtained;

s34, calculating the minimum distance from the ADS-B report position point to the hyperboloid, wherein the calculation steps are as follows;

converting the TDOA equation in the formula (a) into a constraint equation G (x, y, z) of 0, (x)₀,y₀,z₀) For ADS-B report points, the problem of finding the minimum value from ADS-B target report points to hyperboloid is converted into the problem of finding the target functionThe minimum value of (d) is calculated by using a Lagrange multiplier method;

s35, determining a distance threshold value epsilon according to the time error precision on the satellite_dIf the minimum distance between the ADS-B report position and the hyperboloid is larger than the threshold, the target is false, otherwise, confidence is set for the target.

Further, for the case of triple satellite coverage, the computing at the satellite-based ADS-B data center based on the TDOA architecture in step three includes the steps of:

SS31, searching three satellites through the ground data center to receive three message messages of the same message sent by the same target;

the SS32 calculates time difference values TDOA1 and TDOA2 of the same message of the target reaching three satellites according to the time data in the three message information;

SS33, calculating two position points according to the following formula (a), wherein one is a real target position and the other is a false target position;

SS34, whether the target current altitude information obtained by using other information accords with the flying altitude of the aircraft, and eliminates false positions;

SS35, calculating the distance d between the ADS-B report position point and the real position point obtained by TDOA calculation; if the distance d exceeds the distance threshold value epsilon_dThe target is identified as a false target, otherwise, the target is identified as a real target.

Further, for the case of a quad satellite or above quad satellite coverage, the calculating at the satellite-based ADS-B data center based on the TDOA architecture in step three comprises the steps of: and resolving to obtain the target position by utilizing a Chan algorithm and a Taylor series algorithm.

Further, comprising the steps of: calculating the distance between the target position point obtained by resolving by using a Chan algorithm and a Taylor series algorithm and the ADS-B report position point, and if the distance exceeds a distance threshold value epsilon_dThe target is identified as a false target, otherwise, the target is identified as a real target.

Further, the multiple coverage includes at least two coverage; and the satellite time synchronization comprises time synchronization with a GNSS; the message time marking comprises the steps of obtaining time information from a satellite through a design interface between the ADS-B load and the satellite, and marking the arrival time of the ADS-B message when the ADS-B message is received; and the transmission delay equalization comprises that the same message received by different satellites is ensured by an inter-satellite-ground communication network through a designed routing algorithm, and finally reaches the delay equalization of the satellite-based ADS-B data center and meets the system delay requirement.

The invention has the beneficial effects that:

the invention fundamentally solves the problem of validity verification of the satellite-based ADS-B target, can effectively filter false targets and invalid targets, ensures the correctness and validity of ADS-B data, and ensures the control safety.

The embodiment of the invention provides a complete TDOA-based target verification method and scheme design from system architecture design, constellation design to a target verification method.

According to the embodiment of the invention, firstly, a reasonable satellite framework is utilized to enable a target to be covered by more than 2 satellites, time synchronization is realized through a satellite built-in GNSS, and a received signal is decoded in real time to obtain an ADS-B message and is transmitted to a ground data center, so that the problem of insufficient coverage range of a monitored airspace is solved; secondly, the ground data center carries out the processes of position analysis and track generation, different satellites download the same message to carry out TDOA calculation to obtain target position information, and then effective information is confirmed through comparison, so that the problem that an ADS-B monitoring system can possibly obtain false targets is solved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a logical architecture of TDOA calculation for a satellite-based ADS-B system;

FIG. 2 is a 3D model of a constellation layout according to an embodiment of the present invention;

FIG. 3 is a 2D model of a constellation layout according to an embodiment of the present invention;

FIG. 4 illustrates the coverage time of an embodiment of the present invention;

FIG. 5 illustrates an embodiment of the present invention for effective coverage;

FIG. 6 illustrates a principle of authenticity verification of a dual satellite coverage target according to an embodiment of the present invention;

FIG. 7 is a flowchart illustrating validation of a satellite-based ADS-B target based on TDOA according to an embodiment of the present invention.

Detailed Description

All features disclosed in all embodiments in this specification, or all methods or process steps implicitly disclosed, may be combined and/or expanded, or substituted, in any way, except for mutually exclusive features and/or steps.

A target verification method of satellite-based ADS-B comprises the following steps:

designing a satellite-based ADS-B system architecture and a message;

secondly, carrying out constellation design based on a TDOA algorithm architecture based on the satellite-based ADS-B system architecture and the message designed in the first step;

and step three, based on the constellation design in the step two, calculating on the basis of a TDOA framework in a satellite-based ADS-B data center, and comparing the position reported by the ADS-B system to judge the authenticity and the effectiveness of the target.

Further explaining the working principle and the working process of the invention, referring to the attached drawings 1-7, the method comprises the following steps:

(I) TDOA measurement and calculation architecture design

The TDOA-based spatial target multi-point location principle is a hyperbolic (surface) principle, that is, if the distance difference between a target and two fixed points in a space is the same, the target is on the two hyperbolic surfaces with the two fixed points as the focus, and when there are 4 or more stations in the space, a unique target position can be intersected. The hyperboloid positioning algorithm mathematical model is as follows:

the calculation of the TDOA and the target verification are used for synchronous calculation during the track generation. Because the generation of the flight path is realized in the satellite-based ADS-B data center, the TDOA calculation process also occurs in the satellite-based ADS-B data center. To realize verification of authenticity and effectiveness of a satellite-based ADS-B target based on TDOA calculation, a satellite-based ADS-B system architecture and a message transmission protocol need to be reasonably designed to meet the TDOA calculation, and a logic architecture of the embodiment of the invention is shown in FIG. 1. On this basis, the architecture design requirements mainly include:

1) multiple coverage capability: the satellite coverage has more than 2 times of multiple coverage;

2) satellite time synchronization: the satellite-based ADS-B system has time synchronization capability among satellites, and if the satellite is a low-orbit satellite, the GNSS can be directly utilized to realize time synchronization;

3) message time marking: an interface should be designed between the ADS-B load and the satellite, time information is obtained from the satellite, and the arrival time of the ADS-B load is marked when the ADS-B message is received;

4) message attribute marking: an interface should be designed between the ADS-B load and the satellite, and the satellite number and the sub-satellite point position information are obtained from the satellite;

5) transmission delay equalization: the inter-satellite-ground communication network should reasonably design a routing algorithm to ensure that the delay of the same message received by different satellites and finally reaching the satellite-based ADS-B data center meets the system delay requirement and is balanced.

(II) constellation design based on TDOA algorithm framework

According to the TDOA architecture, the satellite constellation is designed to satisfy the capability of multiple coverage. For a satellite system, in order to achieve coverage and service capability for a certain area or the world, a satellite constellation is often required to be formed by several or tens of satellites, in the embodiment of the present invention, a low-orbit constellation covering the world is designed, the constellation parameters are 7, 12, 30, and 15, the height is 1000Km, the inclination angle is 85 °, and 3D and 2D models of the constellation layout are shown in fig. 2 and 3.

The ground coverage area of the satellite is a circle, the coverage area can be calculated through the geocentric half opening angle and the diameter of the coverage area, and the geocentric half opening angle of the coverage area can be calculatedAnd the earth's surface footprint diameter D are:

in the formula, Re is the earth radius, and when the orbit height is h and the ground elevation angle is epsilon, the half cone angle of the satellite view field is alpha;

fig. 4 is a graph of coverage time, with the abscissa representing time and the ordinate representing coverage, which shows that the maximum coverage is 100% and the minimum coverage is 97%, which can effectively cover the world and communicate in real time;

as can be seen from the analysis in table 1, when the phase factor is 3, the coverage of the low-earth satellite constellation configuration is the best, the maximum coverage rate can reach 99.82%, the average coverage rate is 97.11%, and the coverage rate in the whole period is 100%.

TABLE 1 different phase factor coverage analysis

In fig. 5, the abscissa represents latitude and the ordinate represents coverage, and it can be seen from the figure that 80% double coverage can be achieved in most regions, so that the algorithm can well achieve continuous coverage and implement target validity verification of TDOA.

(III) TDOA-based target validity verification method

In a satellite-based ADS-B system, through reasonable design of constellation configuration, if the coverage of 4 or more times of a target is realized, the TDOA of the space position of the target can be solved, the unique position of the target space is obtained, and the authenticity and the effectiveness of the target are judged through comparison of the positions reported by the ADS-B; as can be seen from the constellation design of the TDOA algorithm framework, the satellite constellation can not achieve coverage of 4 and more than a target in all positions, and when the satellite has only double coverage and triple coverage, target validity verification can be performed in the following way:

(1) double satellite coverage verification method

When only two satellites are covered, according to the TDOA positioning principle, it can be determined that the spatial target is located on a hyperboloid with two satellites S1 and S2 as axes at this time, but it cannot be directly verified whether the ADS-B target report position point is on the hyperboloid due to the time error of the satellite measurement and the hysteresis of the ADS-B position report, and the authenticity and validity of the ADS-B target can be verified by the following steps:

1) searching two pieces of message information received by two satellites receiving the same message sent by the same target through a ground data center;

2) calculating the time difference TDOA1 of the same message of the target reaching two satellites according to the time data in the two messages;

3) according to the formula (a), a hyperboloid formula of the time difference between the target and the two satellites can be obtained;

4) calculating the minimum distance from the ADS-B report position point to the hyperboloid, wherein the calculation method is as follows;

converting the TDOA equation in the formula (a) into a constraint equation G (x, y, z) of 0, (x)₀,y₀,z₀) For ADS-B report points, the problem of finding the minimum value from ADS-B target report points to hyperboloid is converted into the problem of finding the target functionThe minimum value of (d) can be calculated using the lagrange multiplier method;

5) determining a distance threshold value epsilon according to the time error precision on the satellite_dIf the minimum distance between the ADS-B report position and the hyperboloid exceeds the threshold, the target is false, otherwise, a confidence level is set for the target.

The principle of double coverage verification is shown in fig. 6.

(2) Triple satellite coverage verification method

When only the triple satellite is covered, two spatial position points can be obtained by calculation according to the TDOA positioning principle and the formula (1), and the authenticity of the ADS-B target can be verified through the following steps:

1) searching three satellites through a ground data center to receive three message information of the same message sent by the same target;

2) according to the time data in the three messages, time difference values TDOA1 and TDOA2 of the same message of the target reaching three satellites are calculated;

3) calculating two position points according to the TDOA formula (a), wherein one position point is a real target position, and the other position point is a false target position;

4) using other information such as whether the calculated target current altitude information accords with the flight altitude of the airplane or not, and eliminating false positions;

5) calculating the distance d between the ADS-B report position point and a real position point obtained by TDOA;

6) if the distance exceeds the threshold value epsilon_dThe target is identified as a false target, otherwise, the target is identified as a true target.

The data processing flow of the ground data center for verifying the effectiveness of the ADS-B target based on the TDOA method is shown in fig. 7.

Other embodiments than the above examples may be devised by those skilled in the art based on the foregoing disclosure, or by adapting and using knowledge or techniques of the relevant art, and features of various embodiments may be interchanged or substituted and such modifications and variations that may be made by those skilled in the art without departing from the spirit and scope of the present invention are intended to be within the scope of the following claims.