High-precision Network Synchronization Technology Between Dry And Wet End Of Sidescan Sonar

Along with the higher imaging precision of side-scan sonar equipment, a corresponding clock synchronization accuracy between dry and wet end of side-scan sonar is required. Meanwhile, the maturity of the Ethernet technology which shows its advantages on speed, stability and cost, brings about the fact that more and more underwater acoustic devices are equipped with Ethernet as data and control communication interface. Network synchronization technology is always involved when using the Ethernet interface between dry and wet end of side-scan sonar. At present people mainly adopt network time protocol(NTP) as well as PTP synchronization protocol based on the IEEE 1588 standard in the network synchronization methods which has a higher accuracy compared with the traditional technique of network time protocol (NTP) synchronization. The thesis brings forward a network time synchronization solution that is based on the IEEE 1588 standard on STM32F407 embedded platform to achieve the network synchronization between the dry and wet end of side-scan sonar. Also the synchronization performance of synchronous system was tested under different conditions of environment and system configurations.This paper expounds each component of the IEEE 1588 standard, including the prerequisite and requirement for the implementation of PTP protocol, PTP system composition, synchronization model, message timestamp generated solutions,state machines engines and so forth in order to provide the theoretical support for PTP clock synchronization system design and implementation.Secondly, the ordinary clock which is in the IEEE 1588 precision clock synchronization protocol, focused on message management, best master clock algorithm,clock servo and state machine protocol engine, was designed to realize. The hardware system including STM32F407 and DP83640 chip. The software system includes FreeRTOS operating system and LwIP network protocol stack. The PTP clock synchronization system software runs in this hardware system and software system.Finally, I tested synchronization performance of synchronous system under different environment and with different system configuration. The various factors influencing of the synchronization performance has analysis by from the test results. Finally corresponding clock synchronization schemes of side-scan sonar system are concluded under different conditions of lateral distance resolution. Test shows that the synchronous system reaches a time synchronization accuracy of sub-microsecond, which can meet the requirement for synchronization accuracy between dry and wet ends of portable side-scan sonar.