Design And Implementation On An Underwater Acoustic Positioning And Communicating System

With the development of marine resources,underwater activities relying on divers or underwater robots become more and more common.During underwater operation,the control center on the mother ship or wharf needs to obtain the location of the underwater vehicle and establish communication with it.In this paper,a set of underwater acoustic equipment with positioning and communication functions is designed.The short baseline positioning technology is used to locate the target,and the multi-carrier multi-band frequency shift keying(MFSK)communication technology is used to communicate.It can monitor the status of the underwater target in real time,command the detection behavior and receive the feedback information of the underwater unit,so as to ensure the smooth progress of the underwater operation.Firstly,the basic principle of short baseline positioning technology is analyzed in theory and simulation.The LFM signal is selected as the positioning signal,and the parameters of the signal are demonstrated.Then,according to the positioning model,the positioning equations are established,and aiming at the error between the sound speed and the mechanical structure of the equipment,the calibration method of the sound speed and the attitude of the array is proposed,and the positioning trajectory is post filtered to make the trajectory close to the real value.The performance of underwater acoustic multi-carrier MFSK communication is affected by multipath channels,and there are serious time-varying,frequency-varying and spacevarying phenomena when acoustic waves propagate underwater.Firstly,this paper introduces the digital modulation and demodulation method of multi-carrier MFSK,introduces the timedomain and frequency-domain measurement method of doppler factor,and studies the theory and simulation of doppler compensation.Then the channel estimation technology is introduced to compensate the selective fading of frequency.At last,the principle of channel coding,PAPR suppression and cyclic prefix are introduced,and the error rate of MFSK communication is simulated.In this paper,the system is designed,which is composed of acoustic array,main device and transponder.Firstly,the acoustic array composed of four receiving transducer and onetransmitting transducer is designed,and the digital signal processing module based on TMS320C6748 digital signal processing chip(DSP)is designed.Then the transmit and receive indexes of the system are calculated,and the transmit frame structure and parameters of the system are determined.Finally,the software flow and algorithm are introduced.The equipment is positioned and tested in the channel pool.The results of pool experiment show that the error of fixed target location is in line with the index,the track of moving target location can reflect the real position,the communication transmission speed and error rate are in line with the index,and the transmission can be stable.