Event-based Scheduling of Multi-loop Stochastic Systems over Shared Communication Channels
Mohammad H. Mamduhi, Adam Molin, Sandra Hirche · 2014
This paper introduces a novel dynamic event-based scheduling mechanism for networked control systems (NCSs) composed of multiple linear heterogeneous stochastic plants whose feedback loops are closed over a shared constrained communication channel. Each subsystem competes for the channel access in order to update its own controller with true local state values. Employing an emulation-based control policy, a probabilistic scheduler allocates the communication resource according to a prioritized error-based (PEB) measure. Based on this policy, a higher chance of transmission is assigned to the subsystems with higher errors, while the other requests are blocked when the channel capacity is reached. Under some mild assumptions, the probabilistic nature of PEB scheduling scheme facilitates an approximative decentralized implementation. We evaluate the stochastic stability of the overall NCS scheduled by PEB policy in terms of networked-induced error ergodicity, by applying the drift criterion over a multi time-step horizon. Moreover, we derive uniform performance bounds for the networked-induced error variance, which demonstrates a significant reduction in comparison with static and random access scheduling schemes such as TDMA and CSMA.