A Design Of Acoustic Direction Finding System For Civil UAV

With the rapid development of unmanned aerial vehicle(UAV)technology,Civil UAVs are gradually entering people's daily life,and playing an important role in remote sensing,mapping,disaster prevention and mitigation.At the same time,more and more problems caused by UAV have followed.Airports,power stations,secret-related units and other key departments have been repeatedly invaded by illegally flying UAV,which has brought serious security risks to people's lives and even to national security.Under the background of the gradual opening of low-altitude airspace in our country,how to detect the UAV intruding into control airspace in time has more and more important significance.This paper designs an acoustic direction finding system for civil UAV.Firstly,the typical noise signals of civil UAV are analyzed.On this basis,the passive direction finding algorithm based on tetrahedral array,time delay estimation algorithm based on generalized cross correlation or phase difference of line spectrum signal are simulated by MATLAB.Then,combined with the simulation results and expected performance indicators,the hardware platform and supporting software system are designed.The hardware system adopts modular design.According to different functions,it can be divided into four parts,including tetrahedral microphone array,signal acquisition unit and system control & data transmission unit.The signal acquisition unit includes signal conditioning module and analog-to-digital conversion module;the system control & data transmission unit includes digital control module and network communication module.The microphone array converts acoustic signal into analog electric signal which is initially amplified and output to the signal acquisition unit;the signal conditioning module filters and amplifies the input signal further,and the magnification factor is adjustable;the AD7768 chip is selected as the A/D chip for signal acquisition;the system control & data transmission unit selects the Cyclone IV series FPGA(EP4CE6E22C8N)as the main control chip,which is mainly responsible for controlling signal amplification and the data acquisition of the A/D chip's,communicating with the host computer to realize real-time uploading of data and reception of control commands through the network interface module which uses a W5300 network interface chip as the core.The software part of the system includes the control program of the FPGA and the comprehensive program of the host computer.The host computer integrated program has the functions of system parameter setting,data analysis and display.During the testing processthe original data and data analysis results can be real-time observed through the interface of the host computer program,and the original data can be stored for data accumulation and backup.Finally,the entire system is tested in the laboratory environment and outdoors,and the system functions and performance indicators are verified.The results show that the acoustic direction finding system for civil UAV works stably and basically meets the expected design requirements.Finally,the system is tested in the outdoor environment respectively to verify the system function and performance indicators.The results show that under the ideal SNR condition,the acoustic direction finding system can accurately measure the direction of the UAV target,which has practical value.It proves that the acoustic method is feasible for the direction finding of the UAV.