PALS: Physically Asynchronous Logically Synchronous Systems

In networked cyber physical systems real time global computations, e.g., the supervisory control of a ight control system, require consistent views, consistent actions and synchronized state transitions across net- work nodes in real time. This paper presents a real time logical synchrony protocol, Physically Asynchronous Logically Synchronous (PALS), to support real time global computation. Under the PALS protocol, engi- neers design and verify applications as if all the dis- tributed state machines were driven by a single global clock. The PALS protocol is optimal in the sense that 1) the bound on the periods of the real time global computation, such as the supervisory controller, is the shortest possible, and 2) the message overhead in achieving logical synchrony is minimal.published or submitted for publicatio