Real-time analysis of engine control applications with speed estimation

Engine control applications include computational activities that adapt their behavior as a function of the engine speed, referred to as adaptive variable-rate (AVR) tasks. Although a substantial amount of work has been done to analyze the timing behavior of real-time applications with AVR tasks, most of the authors assumed the knowledge of the instantaneous engine speed at any instant. In practice, however, the instantaneous engine speed is not known and can only be estimated by various techniques, which hence introduce an error with respect to the ideal case of perfect knowledge. If not properly handled, such an error can result in a potentially unsafe analysis. This paper proposes a general approach to include speed estimators in the analysis of engine control applications and shows two particular examples using common speed estimators. Finally, estimators are also characterized through a numerical evaluation and experimental results are presented to evaluate their impact in terms of system schedulability.