Research On Time Synchronization And Triggering Based On Distributed Network

There is no more accurate time benchmark in the distributed network.The test instruments at each node are independent of each other,and the test results have no time unity.Especially for special test targets in the light weapons target,a more accurate unified time benchmark is needed.Based on this background,this paper studies and implements time synchronization and triggering in distributed network.Firstly,this paper compares and analyzes the commonly used clock synchronization at home and abroad,such as coding timing,NTP protocol and PTP protocol.According to the requirements of light weapons target and the characteristics of distributed network,this paper proposes to use PTP protocol for timing synchronization and trigger,designs the network node synchronization and trigger unit,and carries out timing synchronization trigger experiment.In the design of network node synchronization and trigger unit,the principle of IEEE1588v2 protocol and the processing flow of synchronization message are analyzed.It is known that the main factors affecting synchronization are link asymmetry and network delay.Therefore,the IEEE 1588 clock is simulated,the Kalman filter and sliding mode control algorithms are compared and analyzed,and the hardware and software of network node synchronization and trigger unit are designed.In the hardware design,dp83640 is selected as the clock synchronization chip,and its external GPIO port can be used as the trigger interface;At the same time,STM32F407 is selected as the MCU,and the minimum control system is designed around the main control chip,including MCU module,power module,reset module and so on,to control the clock synchronization chip to synchronize and trigger.In order to simplify and facilitate the interface,RMII mode is adopted for the connection mode between the main control chip and the clock chip,and the number of interfaces in this mode is half less than that in MII mode;At the same time,peripheral circuits are designed around the clock chip,including network interface circuit and so on.In the software design,the corresponding software framework is constructed.Time synchronization requires two network node synchronization and trigger units as master and slave clocks respectively,so TCP / IP protocol is required for transmission,and Lw IP protocol with small resource consumption is selected for transmission;At the same time,BMC optimal master clock algorithm is selected in the selection of master-slave clock.In terms of trigger,for the external GPIO interface of dp83640,four of them are set as timing trigger,delay trigger,second pulse trigger and external event trigger interface to realize the synchronous trigger function.After completing the design of network node synchronization and trigger unit,the distributed network based on light weapons target is simulated and built.The time synchronization trigger under different network environments,different synchronization parameters and different trigger modes is tested.The experimental results show that the network node synchronization and trigger unit can meet the time synchronization accuracy required by the light weapon target,that is,the time synchronization accuracy can meet the requirements of less than 300 ns,and can realize the time synchronization trigger function and meet the design requirements.