| Since the birth of the Traffic Collision Avoidance System(TCAS),it has quickly played a vital role in aviation safety.However,with the rapid development of the aviation industry,the number of aircraft in the airspace has increased dramatically,and the frequency of communication between aircraft through TCAS has become higher and higher.The problem of communication interference will greatly reduce the performance of the TCAS system and bring hidden dangers to aviation safety.Although Automatic Dependent Surveillance-Broadcast(ADS-B)has been adopted by many countries and regions as the main aviation surveillance method in the future,it cannot completely replace the existing TCAS II.At this time,it should combine active surveillance and ADS-B passive surveillance to develop hybrid surveillance technology.Based on the latest standard DO-385 of Airborne Collision Avoidance System X(ACAS X),this paper designs a hybrid surveillance technology based on active surveillance and ADS-B passive surveillance.While not reducing the performance of the collision avoidance system,reducing the frequency and power of communication between aircraft,and increasing the surveillance range.The main contents of this paper are as follows:This paper firstly analyzes the ACAS X system framework and principle.After combining active surveillance and ADS-B passive surveillance,it proposes to divide the surveillance status of ownship into active surveillance status,hybrid surveillance status,and extended hybrid surveillance status.It also studies the conversion between the three surveillance states.The tracking of targets of surveillance and tracking module(STM)is divided into altitude tracking and range tracking.This paper studies an approximate minimum mean square error estimation(MMSE)Kalman filter with quantized measurement in altitude tracking.The target state value is the altitude and altitude rate.It simulates the root-mean-square error of the state value when the height quantization is 25 ft and 100 ft.The simulation results show that both the traditionally linear Kalman filter with quantized measurement and the approximate minimum mean square error estimation Kalman filter with quantized measurement show a good effect on the altitude tracking of the target,and the approximate minimum mean square error estimation Kalman filter with quantized measurement shows better tracking performance.The range tracking of the target adopts unscented Kalman filter in polar coordinates,and the target state value is relative range,relative range rate,and relative velocity rate.It simulates and vertifes the root mean square error of the state value.The simulation results show that unscented Kalman filter shows good performance in range tracking of targets.Then this paper studies the implementation of the STM.The STM receives multiple inputs and has multiple entry points.It focuses on studying the implementation processes of the mode S reply,mode C reply,and three types of ADS-B passive surveillance reports.And it studies the conversion between the three coordinates of WGS84,ECEF and ENU involved in the surveillance and tracking module during passive surveillance.Finally,this paper simulates and tests the surveillance function of STM.It gives the structure of the simulation test program,the test platform,the programming language,the structure and test standards of STM input and output data.The test data are all from ACAS X's latest standard DO-385 test suite.There are a total of seven groups of test data(422 test cases).From each group of data,it selects a total of 158 test cases,and obtains the corresponding output report through the simulation program.It compares the data in the output report with the expected output data and the test results show that the selected 158 test cases have passed the test,and the pass rate is 100%.At last,a graphical method is used to visually show the tracking process of several of the test cases in relative and WGS84 absolute coordinate systems. |
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