Networked control systems (NCSs) are feedback control loops that are closed over a communication network. Emerging applications, such as telerobotics, drones and autonomous driving are the most prominent examples of such systems. Regular and timely information sharing between the components of NCSs is essential, as stale information can lead to performance degradation or even physical damage. In this work, we consider multiple heterogeneous NCSs that transmit their system state over a shared physical wireless channel towards a gateway node. We conduct a comprehensive experimental study on selected MAC protocols using software-defined radios with state-of-the-art (SotA) solutions that have been designed to increase information freshness and control performance. As a significant improvement over the SotA, we propose a contention-free algorithm that is able to outperform the existing solutions by combining their strengths in one protocol. In addition, we propose a new metric called normalized mean squared error and demonstrate its effectiveness as utility for scheduling in a case study with multiple inverted pendulums. From our experimental study and results, we observe that a control-aware prioritization of the sub-systems contributes to minimizing the negative effects of information staleness on control performance. In particular, as the number of devices increases, the benefit of control-awareness to the quality of control stands out when compared to protocols that focus solely on maximizing information freshness.
翻译:网络控制系统(NCS)是通信网络上封闭的反馈控制环。新的应用程序,如调频机器人、无人机和自主驾驶等,是这类系统最突出的例子。NCS各组成部分之间定期和及时的信息共享至关重要,因为陈旧的信息可能导致性能退化甚至物理损害。在这项工作中,我们认为,多种不同的NCS通过共享的有形无线通道将其系统状态传送到一个网关节点。我们利用软件定义的具有最新技术的无线电(SotA)解决方案,对选定的MAC协议进行全面的实验研究,目的是增加信息新鲜度和控制性能。作为对SotA的重大改进,我们建议一种无争议的算法,能够通过将现有解决方案的长处结合到一个协议中来使其超越现有解决方案。此外,我们建议采用一种新的标准,即将系统标准归一化的中位平方误差,并展示其有效性,用于在案例研究中安排有多个完全颠倒式的穿透式输盘的案例研究。我们从实验研究和结果中看到,对亚系统控制性定位的优先排序,以降低质量控制为特定控制效果,从而最大限度地减少质量控制效果。