Research Location Technology Of Ultrasonic Detection For Depth Charge Fuze

Target location technology of ultrasonic detection is very important to improve the damaging effect of the depth charge.With the more highly requirement for the techniques of the target detection and location,the modern underwater weapon system will be used to develop the new techniques for the target detection and location,in which the fuze target detector has the new abilities of fast and accurate discovery,recognition and tracking,all of which are very important in the improvement of the comprehensive combat capability for the underwater ammunition weapons.With the help of the key location problem in fuze ultrasonic detection,the fuze location techniques of simple two elements two dimensions are studied in this paper.Based on the signal processing theory of sonar and underwater acoustic,we analyze the sound velocity,the propagation loss and the interference.Then the volume reverberation model for the underwater ultrasonic detector is given out,and with the analysis of transmitted waveform,the signal waveform for the underwater ultrasonic detection is given.The pulse width of the signal is also obtained by the analysis of ambiguity function.Using the analysis of the ratio of noise,reverberation and echo,we get the signal frequency of underwater ultrasonic detection.And the signal cycle is also obtained by analysing the detecting distance.With the analysis of the echo detection model,we obtained the measuring conditions for the target echo delay and frequency shift.Based on the principle of three elements delay location and two elements pressure difference location,we analyzed the characteristics of the three array elements of delay location,and of the four array elements of pressure difference location,and discussed the principle of biological detection location,and then presented the two elements two dimensions location method,which was based on the biological spiking neural network information processing model and bionic binaural location mechanism.The two elements two dimensions location algorithm was designed based on the delay and pressure difference,which was combined with one dimension delay information and one dimension pressure difference information.With the theory of estimating parameters of Cramer Rao lower bound,we analysed the distribution of estimation error in the plane,the relationship between the estimation error and distance of two transducers,between the estimation error and distance difference of target and two transducers,and between the estimation error and the pressure difference.And then the method of delay estimation was selected,and the calculation method of pressure was also improved.The simulation results showed the feasibility of the two elements two dimensions location algorithm,which was based on the delay and sound pressure difference.Based on all of these,the transmitting-receiving circuit of the transducer array and the parallel transmitting-series receiving transducer array was designed,which could be achieved time delay and sound pressure difference.Two elements two dimensions location algorithm was realized in Field-Programmable Gate Array(FPGA),in which the algorithm unit was composed of the FIFO unit,"ping-pong"memory unit,time delay unit,sound pressure unit and location unit.The time delay unit was composed of Fourier transform subunit,conjugate subunit,PHAT weighting subunit,inverse Fourier transform subunit,modulo subunit and extreme detection subunit.With the use of asynchronous FIFO,the data of the asynchronous crossing clock transmission was achieved in each FPGA unit of different clock system.Four memory blocks of Block0-Block3 were carried out the "Ping-Pong" operation.The FFT/IFFT subunit was achieved by the method of time selection based 2.The speed of the butterfly operation was accelerated by improving the algorithm and pipelining.The simulation results showed that the algorithm can be implemented in FPGA hardware only need tens of microseconds,and fit the requirements of real-time location.We established the new ultrasonic array detection simulation experiment system,and conducted simulation experiments and pool test experiments,to verify the feasibility of the experiment system and the effectiveness of the location algorithm.The simulation experiment results showed the location relative error of the short range detection was less than 5%when the distance between the target and detector less than 6 meters.The pool experiment results showed the location relative error is less than 4%when the distance between the target and detector less than 3.5 meters,much close to the location accuracy of the simulation experiment.So in the future,it can be used in the dynamic simulation experiment in the ultrasonic detection and in the location of the fuze target detector.