Design And Implementation Of Water Surface Monitoring Unit For Underwater Acoustic Autonomous Navigation System

In order to carry out underwater missions efficiently,accurately and safely,underwater vehicles need to know their own location,running route and destination,so the positioning and navigation of underwater vehicles are very important.With the continuous enhancement of the range capability of the mobile buoy,the standby time and continuous working time of the long-baseline underwater acoustic navigation system are also prolonged,and the cycle of the mother ship’s continuous follow-up mission is getting longer and longer.In order to simplify the long-period following task of the mother ship,this paper designs a set of water surface monitoring unit for underwater cooperative target underwater acoustic autonomous navigation based on the long baseline underwater acoustic positioning navigation system,completes the hardware circuit design of the water surface monitoring unit,realizes the system design function and index on the basis of the hardware circuit,and verifies the accuracy and reliability of the underwater acoustic autonomous navigation system through lake test and sea test.When the underwater cooperative target makes sound,the underwater preprocessing unit collects the original acoustic data,which is packaged by the water surface monitoring unit ARM and put into the shared memory.The DSP reads the original data from the shared memory to detect and estimate the signal,calculates the acoustic measurement results sent to ARM,ARM to determine whether the detected pulse amplitude exceeds the set broadcast threshold,and establishes the master station buoy according to the mobile buoy that exceeds the broadcast threshold.The mobile buoy established as the master state can receive the position indication signal processing results of the slave state buoy,collect the position indication signal results of at least two slave states,and select the direct acoustic pulse from several groups of pulses in the acoustic measurement results.finally,the position of the mobile buoy is transformed,the TOA algorithm and the TDOA algorithm are studied horizontally,and the double pulse telemetry method is studied vertically.After calculating the position of the underwater vehicle,the main station buoy controls the navigation launch unit to complete the navigation of the underwater vehicle.When the distance between the host buoy and the underwater vehicle exceeds the defined radius of the community,the host buoy enters the transitional critical state.The host buoy will designate the next host buoy according to the collected acoustic measurement information in the community,so as to complete the transfer of the control center.The water surface monitoring unit can also send the position of the underwater vehicle to the command center through satellite communication to realize the remote monitoring function of the underwater vehicle.According to the design requirements and specifications of the system,taking SOMTL5728 as the core board,the power module design,interface module hardware design and synchronous circuit design are carried out to complete the functions of GNSS data receiving,Ethernet data transceiver,satellite communication data transceiver,radio data transceiver,data packaging,signal acquisition,synchronous differential transmission and so on.Linux operating system is selected for software design to carry out multi-thread programming.GNSS module programming,network communication programming,data packaging programming,original data storage programming,calibration solution programming,intercore communication programming,pulse selection programming and positioning solution programming are realized in the software.Finally,through the lake test and sea test,the positioning accuracy of underwater acoustic autonomous navigation is verified,and the accuracy and reliability of the system are confirmed.