Resolving priority inversions in composable conveyor systems

The well known problem of priority inversions that occurs in classical real-time systems also manifests in decentralized cyber-physical systems. Using a specific example of composable conveyor systems, we show how priority inversions hinder the transport of entities through the conveyor systems. We present a novel adaptation of the classical priority inheritance protocol for resolving these cyber-physical priority inversions. While the approach resolves cyber-physical priority inversions, the structure and constraints of the conveyor systems cause the jitter associated with the end-to-end latency of the highest priority parts to increase. Further, these constraints also limit the applicability of the classical priority ceiling protocol in this class of cyber-physical systems. Simulation results demonstrate the correctness and reasonable communication overhead of the approach.