![]() ![]() We can use virtual time to schedule sequentially executed processes so that from their perspective they are being run in parallel. Virtual time is a concept that was designed to enable multiple virtual machines to be multiplexed on a single physical hardware. One solution is to provide a notion of virtual time to the physical processes so that their executions can be explicitly scheduled with simulation models and advance together in virtual time. A capable testbed combines both physical and virtual components, including but not limited to real sensors, embedded devices, virtual machines, emulated communication networks, simulation models of physical processes, analytical models of background traffic, etc.Ī key challenge in simulating CPSs is to combine seamlessly the physical and cyber worlds to conduct high-fidelity experiments, as real components execute applications with the real-world wall clock and virtual components advance model states with a virtual clock. Virtual testbeds are tools designed to address this challenge. The mission-critical nature of some CPSs requires less intrusive techniques than manipulating them directly. ![]() As embedded computers monitor and control mission-critical physical processes in real time (e.g., an electrical power system), performing evaluation directly on them poses challenges. While great care is used to deploy modern cyber-physical systems, they are continuously being updated and expanded. ![]() These complex systems called cyber-physical systems (CPSs) require thorough testing and evaluation to ensure safety, security, and correct function. These observations are analyzed, transformed, and processed to interact and shape the physical world around them through actuators, motors, and controllers. When computers interact with the physical world, they pull information from sensors in the form of measurements and signals. Finally, we demonstrate the usability of our testbed and the differences between both approaches in a power grid control application.įrom the first ring of an alarm clock in the morning to the commute home from work, and from the manufacturing of products or robot-assisted surgery to the food on the table, computers are ingrained in every aspect of modern life. 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. We also analyze the performance of both approaches to synchronization including overhead, accuracy, and error introduced from each approach. 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. Virtual clocks also enable high-fidelity experimentation by interrupting real and emulated cyber-physical applications to inject offline simulation data. A core component is the distributed virtual time system that enables the efficient synchronization of virtual clocks among distributed embedded Linux devices. In this article, we present a cyber-physical system testing platform combining distributed physical computing and networking hardware and simulation models. ![]() Simulation-based testbeds are useful tools for engineering those cyber-physical systems and evaluating their efficiency, security, and resilience. Our world today increasingly relies on the orchestration of digital and physical systems to ensure the successful operations of many complex and critical infrastructures. ![]()
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