Timing analysis of cyber-physical applications for hybrid communication protocols

Many cyber-physical systems consist of a collection of control loops implemented on multiple electronic control units (ECUs) communicating via buses such as FlexRay. Such buses support hybrid communication protocols consisting of a mix of time- and event-triggered slots. The time-triggered slots may be perfectly synchronized to the ECUs and hence result in zero communication delay, while the event-triggered slots are arbitrated using a priority-based policy and hence messages mapped onto them can suffer non-negligible delays. In this paper, we study a switching scheme where control messages are dynamically scheduled between the time-triggered and the event-triggered slots. This allows more efficient use of time-triggered slots which are often scarce and therefore should be used sparingly. Our focus is to perform a schedulability analysis for this setup, i.e., in the event of an external disturbance, can a message be switched from an event-triggered to a time-triggered slot within a specified deadline? We show that this analysis can check whether desired control performance objectives may be satisfied, with a limited number of time-triggered slots being used.