无GPS受限的分布式时钟同步系统的设计  

Circuit design of a distributed time synchronization system without GPS restriction

作　　者：淳少恒 刁庶 陈儒军[2] CHUN ShaoHeng;DIAO Shu;CHEN RuJun(Control Technology Institute,Wuxi Institute of Technology,Wuxi 214121,China;School of Geosciences and Info-Physics,Central South University,Changsha 410083,China)

机构地区：[1]无锡职业技术学院控制技术学院,无锡214121 [2]中南大学地球科学与信息物理学院,长沙410083

出　　处：《地球物理学进展》2022年第5期2138-2146,共9页Progress in Geophysics

基　　金：校级博士科研课题基金项目(10492722007);国家自然科学基金基础科学中心项目(72088101);国家自然科学基金青年项目(42104142)联合资助。

摘　　要：为解决在井下或者隧道内这些完全没有GPS信号的环境下,地球物理仪器也能进行分布式勘探这一问题,本文首先对分布式算法LSTS(Least Square Estimation Based Time Synchronization)进行改进得到一种常增益的LSTS算法,记为LSTS-CG(LSTS with Constant Gain),然后基于该算法设计出一种全新的不依赖GPS的分布式时钟同步系统.LSTS算法最开始是针对无线传感网提出的,但对地球物理仪器具有极强的借鉴意义.改进后的LSTS-CG算法不仅具有同步误差小,同步效果稳定,还具有计算量少,存储量小等优点,所以十分适用于分布式勘探系统.在实际设计中,本文在FPGA芯片中实现了LSTS-CG算法,包括设计实现相对斜率估计算法,低通滤波器,斜率补偿算法和相位补偿算法,并且解决了该类电路设计的一些普遍的关键性问题,如连续离散的虚拟时钟的产生和兼容GPS授时方式的设计等.这些问题的解决很好地确保了本系统的高效性和实用性,使得本系统被大规模应用成为了可能.本文在一片FPGA内就完成了所有功能模块的设计,最大程度地简化了电路结构,提升了系统的稳定性.通过对本系统的同步误差进行测试,结果表明,即使是采用普通晶振,该系统的同步误差也能达到亚微秒级,并且还具有功耗低,成本低廉等优点.最后,本文从通信时延,拓扑和周期这三个方面,测试了本系统的性能,所得结果具有一定的规律性,能为野外施工方案的设计提供指导意见.This paper designs a new distributed time synchronization system without GPS restriction to help geophysical instruments perform distributed prospecting in an environment where there is no GPS signal at all,such as in the mine or the tunnel.In order to solve the problem that geophysical instruments can also perform distributed prospecting in underground or tunnel environments where there is no GPS signal at all,this paper first optimizes the distributed algorithm LSTS(Least Square Estimation Based Time Synchronization)to obtain a constant gain LSTS algorithm which denoted as LSTS-CG(LSTS with Constant Gain),and based on this algorithm,a new distributed time synchronization system without GPS restriction is designed.The LSTS algorithm was originally proposed for WSNs(Wireless Sensor Networks),but it has a strong reference for geophysical instruments.The optimized LSTS-CG not only has the advantages of smaller synchronization error and more stable synchronization effect,but also has the advantages of less computation and smaller storage,so it is very suitable for distributed prospecting systems.In the actual design,this paper implements the LSTS-CG algorithm in FPGA(Field Programmable Gate Array),including designing the implementation of relative drift estimation algorithm,low-pass filter,drift compensation algorithm and offset compensation algorithm.And some common key problems in this type of circuits have been solved,including the generation of continuous discrete virtual time and the design of GPS-compatible timing mode.The solution of these problems ensures the efficiency and practicability of the system,making it possible for the system to be applied on a large scale.In this paper,the all functional modules are completed in a FPGA,which simplifies the circuit structure and improves the stability of the system.By testing the synchronization error of this system,the results show that even with ordinary crystal oscillator,the synchronization error can reach sub-microsecond level,and the system also has the advan

关 键 词：时钟同步 常增益的LSTS算法 地球物理仪器 分布式勘探 FPGA 

分 类 号：P631[天文地球—地质矿产勘探]