实时分布式仿真测试平台时钟同步算法

针对Cristian算法和Berkeley算法同步时间精度不高的缺陷,提出一种基于反射内存的网络时钟同步算法。该算法通过计算出准确的延迟得到较精确的漂移率,并采用渐入渐出的同步冗余策略来确定较精确的同步周期和同步方式。实验测试结果证明,与Cristian算法相比,该算法的时间精度更高。     

网络时间协议实现分布式系统内时钟同步的原理分析

在某些关键应用中，分布式系统对系统内时钟的一致性要求是比较高的．网络时间协议作为一个Internet标准协议，可以作为分布式系统时钟同步的有效工具．本文介绍了网络时间协议的基本模型和体系结构，并着重分析了使用网络时间协议实现时钟同步的基本原理．     

一类网络化控制系统的时延分析及时钟同步方法

针对如何保证精确的分布式时钟同步以实现预期的实时调度和控制问题,通过对一类基于全双工交换式以太网并采用总线型拓扑的网络化控制系统时延特征的分析,结合网络精确时钟同步协议,在分析了其可行性的基础上,给出了网络化控制系统时钟同步的设计及实现方法.     

CesiumSpray: a Precise and Accurate Global Time Service for Large-scale Systems

In large-scale systems, such as Internet-based distributed systems, classical clock-synchronization solutions become impractical or poorly performing, due to the number of nodes and/or the distance among them. We present a global time service for world-wide systems, based on an innovative clock synchronization scheme, named CesiumSpray. The service exhibits high precision and accuracy; it is virtually indefinitely scalable; and it is fault-tolerant. It is deterministic for real-time machinery in the local area, which makes it particularly well-suited for, though not limited to, large-scale real-time systems. The main features of our clock synchronization scheme can be summarized as follows: hybrid external/internal synchronization protocol improves effectiveness of synchronization; heterogeneous failure semantics for clocks and processors improves previous lower bounds on processors; two-level hierarchy improves scalability. The root of the hierarchy is the GPS satellite constellation, which sprays its reference time over a set of nodes provided with GPS receivers, one per local network. The second level of the hierarchy performs internal synchronization, further spraying the external time inside the local network.     

A Network Time Interface M-Module for Distributing GPS-Time over LANs

This paper provides a comprehensive overview of our Network Time Interface (NTI) M-Module, which facilitates high-accuracy time distribution in LAN-based distributed real-time systems. Built around our custom UTCSU VLSI chip, it hosts all the hardware support required for interval-based external clock synchronization: A high-resolution state- and rate-adjustable clock, local accuracy intervals, interfaces to GPS receivers, and various timestamping features. Maximum network controller and CPU independence ensures that the available NTI prototype can be employed in virtually any COTS-based system with MA-Module interface. Our experimental evaluation shows that time distribution with s-accuracy is possible even in Ethernet-based system architectures, provided that the available configuration parameters are suitably chosen to cope with the various hidden sources of timing uncertainty.     

航空发动机FADEC系统双机时钟级同步技术研究

随首航空发动机控制技术的发展,全权限数字电子控制（FADEC）系统的可靠性设计变得越来越重要;在FADEC系统中,同步设计对于提高航空发动机全权限数字式电子控制器的可靠性具有重要的意义;为了解决如何在FADEC系统中实现双机时钟缓同步设计,简要的分析了应注意的问题;随限介绍了设计中采取软硬件相结合来同步两计算机实时时钟的基本方法,在实践中证明了该方法是行之有效的。