A Novel Communication and Control Co-Design Method for Wireless Control Systems: A Communication Perspective

By providing cost-efficient flexibility beyond wired control systems, real-time wireless control systems (WCSs) are pivotal in industrial internet of things (IIoT), which can enable massive emerging applications in IIoT, e.g., autonomous driving, remote medical, teleoperation, etc. To guarantee good control performance over wireless networks, ultra-reliable and low-latency communications (URLLCs) are required from communication perspective. However, this would result in frequent high-rate data transmission, leading to extremely high resource consumption or even network congestion, which impedes the application of WCSs in IIoT. This paper proposes a novel co-design method for communication and control in WCSs, which offers a new strategy to address the challenges introduced by URLLC. Specifically, we first formulate an optimization problem aiming to minimize the communication and control cost by jointly optimizing transmission trigger, communication power, and Lyapunov cost, which, however, is NP-hard. To address this challenge, we employ a two-stage strategy by first defining a new metric, i.e, state-to-error ratio (SER), as a trigger condition to evaluate control performance. Based on this metric, we analyze the relationship between SER and signal-to-noise-ratio (SNR) and show their hidden consistency in evaluating both communication and control performance, thus facilitating our communication and control co-design. Subsequently, we establish a closed-form relationship between the control convergence rate and communication reliability and thereby obtain the optimal transmit power to ensure the overall system performance. Finally, simulation results are provided to demonstrate the efficacy of our proposed method.