MixCPS: Mixed Time/Event-Triggered Architecture of Cyber–Physical Systems

Cyber–physical system (CPS) integrates variety of applications where some work in a time-triggered manner while others work in an event-triggered manner. Supporting unified designs of both time-triggered and event-triggered tasks facilitates the integration of CPS applications. This paper presents a mixed time/event-triggered architecture called MixCPS to make CPS applications work in the integrated and optimized manner. To optimize MixCPS, we propose a new timing performance metric for CPS applications, i.e., the application-level delay, which is induced from sensor to actuator and captures the coupling between cyber and physical worlds. Using the system-level time-triggered scheduling based on the synchronization between computation and communication nodes, we optimize the assignment of computation tasks and the packet transmissions in order to minimize the application-level delays. Furthermore, we discuss the scheduling policy for event-trigged tasks after the resource reservation for time-trigged tasks. Finally, the proposed MixCPS is evaluated by several simulations which show that the application-level delays can be significantly reduced through the time-triggered cooperation mechanism of computation and communication.