State-dependent priority scheduling for networked control systems

Abstract

Networked control systems (NCS) have attracted considerable attention in recent years. While the stabilizability and optimal control of NCS for a given communication system has already been studied extensively, the design of the communication system for NCS has recently seen an increase in more thorough investigation. In this paper, we address an optimal scheduling problem for a set of NCS sharing a dedicated communication channel, providing performance bounds and asymptotic stability. We derive a suboptimal scheduling policy with dynamic state-based priorities calculated at the sensors, which are then used for stateless priority queuing in the network, making it both scalable and efficient to implement on routers or multi-layer switches. These properties are beneficial towards leveraging existing IP networks for control, which will be a crucial factor for the proliferation of wide-area NCS applications. By allowing for an arbitrary number of concurrent transmissions, we are able to investigate the relationship between available bandwidth, transmission rate, and delay. To demonstrate the feasibility of our approach, we provide a proofof-concept implementation of the priority scheduler using real networking hardware.

Delay-sensitive Joint Optimal Control and Resource Management in Multi-loop Networked Control Systems

“…As (33) is a standard LQG problem, we drop the derivation of γ i, * for brevity. This is, however, known that the optimal law γ i, * k and gain L i, * k in ( 14) and ( 15) are the solutions of the problem (33). (Full derivation can be found in [4].…”

“…To achieve this, a main issue to address is optimal timeliness, i.e., when is the best time to make a specific action such as sampling, transmission or actuation. This problem is addressed in the control community mainly for data sampling over singleservice communication support leading to optimal event-based technique to restrict unnecessary transmission [30]- [32], and prioritized MAC protocols to distribute resources based on urgency [33], [34]. These approaches consider some measured or observed quantity of the control system, such as estimation error, as the triggering function.…”

Integration of Communication Networks and Control Systems Using a Slotted Transmission Classification Model

“…How, for instance, can network resources for opportunistic transmissions be shared by multiple NCS such that their performance is maximized? Possible approaches include packet priority based scheduling [16] in the network or the use of performance-oriented event-based control methods [17] in the control system. To this end, we plan to extend previous work to explicitly consider deterministic transmissions in the scheduling or event-triggering decisions for opportunistic transmissions.…”

Packet-Drop Design in URLLC for Real-Time Wireless Control Systems

“…The associate editor coordinating the review of this manuscript and approving it for publication was Cunhua Pan . where imperfect transmission coefficients are introduced by communication protocols, e.g., transmission control protocol (TCP) or user datagram protocol (UDP). In [4]- [9], the authors further investigated the control performance of different control categories with imperfect communications. In [10], the authors provided a tutorial and reviewed the existing advances of wireless network design and optimization for wireless networked control systems.…”