Sampling jitter compensation for numeric PID controllers

Control applications demand the use of strict timing constraints. The commonly used priority-based preemptive scheduling methods introduce jitter on task executions. This implies that the separation between consecutive starting times of a given control task is not constant. In the same time control theory assumes that sampling periods were constant. These variations on the sampling period of control task implementation can degrade the control system performance and in ultimately can induce instability in the system. In this paper, we present a practical approach to deal with sampling errors created by variations of sampling jitter thru appropriate variations of controller parameters. This are calculated on-line based on ROTS indications regarding the distance between this and the last instance of the control task.