Our world today increasingly relies on the orchestration of digital and physical systems to ensure the successful operations of many complex and critical infrastructures. Simulation-based testbeds are useful tools for engineering those cyber-physical systems and evaluating their efficiency, security, and resilience. In this article, we present a cyber-physical system testing platform combining distributed physical computing and networking hardware and simulation models. A core component is the distributed virtual time system that enables the efficient synchronization of virtual clocks among distributed embedded Linux devices. Virtual clocks also enable high-fidelity experimentation by interrupting real and emulated cyber-physical applications to inject offline simulation data. We design and implement two modes of the distributed virtual time: periodic mode for scheduling repetitive events like sensor device measurements, and dynamic mode for on-demand interrupt-based synchronization. We also analyze the performance of both approaches to synchronization including overhead, accuracy, and error introduced from each approach. By interconnecting the embedded devices’ general purpose IO pins, they can coordinate and synchronize with low overhead, under 50 microseconds for eight processes across four embedded Linux devices. Finally, we demonstrate the usability of our testbed and the differences between both approaches in a power grid control application.

中文翻译：

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用于信息物理系统仿真的分布式虚拟时间同步

我们今天的世界越来越依赖数字和物理系统的协调来确保许多复杂和关键基础设施的成功运行。基于仿真的测试平台是设计这些网络物理系统并评估其效率、安全性和弹性的有用工具。在本文中，我们提出了一个结合分布式物理计算和网络硬件和仿真模型的信息物理系统测试平台。一个核心组件是分布式虚拟时间系统，它能够在分布式嵌入式 Linux 设备之间实现虚拟时钟的高效同步。虚拟时钟还可以通过中断真实和模拟的网络物理应用程序来注入离线模拟数据，从而实现高保真实验。我们设计并实现了两种分布式虚拟时间模式：周期模式用于安排重复事件，如传感器设备测量，以及动态模式用于按需中断的同步。我们还分析了两种同步方法的性能，包括每种方法引入的开销、准确性和错误。通过互连嵌入式设备的通用 IO 引脚，它们可以在 50 微秒内以低开销协调和同步四个嵌入式 Linux 设备上的八个进程。最后，我们展示了我们的测试平台的可用性以及两种方法在电网控制应用中的区别。