A Time-Triggered Distributed Computing Environment for Cyber-Physical Systems Based on Physical Time and Logical Time

The paper presents a time-triggered distributed computing environment for cyber-physical systems utilizing networks with varying communication time. The time-triggered architecture utilizing a time-triggered network is suitable for building hard real-time cyber-physical systems such as distributed embedded control systems that require minimal jitter. However, distributed embedded control systems utilizing networks with varying communication time such as wireless networks are increasing and the jitter should be also reduced in such systems. The paper presents a distributed computing environment in which input and output tasks are activated synchronized with physical time and computation tasks are activated by the reception of timestamped messages and managed based on logical time. The control performance is affected by the jitters of input and output tasks but not affected by the jitters of the computation tasks, so the jitter of the computation task activation caused by the variation of communication time is tolerated. We have developed a distributed computing middleware, which provides functions for managing timestamped messages and logical time. By using the middleware, application program can be developed without considering either timestamps or logical time.