Networked control system (NCS) refers to a set of control loops that are closed over a communication network. In this article, the joint operation of control and networking for NCS is investigated wherein the network serves the sensor-to-controller communication links for multiple stochastic linear time-invariant (LTI) subsystems. The sensors sample packets based on the observed plant state, which they send over a shared multihop network. The network has limited communication resources, which need to be assigned to competing links to support proper control loop operation. In this setup, we formulate an optimization problem to minimize the weighted-sum linear-quadratic-Gaussian cost of all loops, taking into account the admissible sampling, control, congestion control (CC), and scheduling policies. Under some mild assumptions on the sampling frequencies of the control loops and the communication network, we find the joint optimal solution to be given by a certainty equivalence control with a threshold-based sampling policy, as well as a back-pressure-type scheduler with a simple pass-through CC. The interface between network and control loops is identified to be the buffer state of the sensor node, which can be interpreted as network price for sampling a packet from the control perspective. We validate our theoretical claims by simulating NCSs comprised of multiple LTI stochastic control loops communicating over a two-hop cellular network.

中文翻译：

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实时网络控制系统中的联合跨层优化

网络控制系统（NCS）是指通过通信网络闭合的一组控制环。在本文中，研究了NCS的控制和联网的联合操作，其中网络为多个随机线性时不变（LTI）子系统的传感器到控制器通信链路提供服务。传感器根据观察到的工厂状态对数据包进行采样，然后通过共享的多跳网络发送这些数据包。网络的通信资源有限，需要将其分配给竞争链路以支持正确的控制环路操作。在此设置中，我们考虑到允许的采样，控制，拥塞控制（CC）和调度策略，制定了一个优化问题，以使所有环路的加权和线性二次高斯成本最小化。在对控制环和通信网络的采样频率进行一些温和假设的情况下，我们发现联合最优解将由具有基于阈值的采样策略的确定性等价控制以及具有简单的传递CC。网络和控制回路之间的接口被标识为传感器节点的缓冲区状态，从控制角度看，这可以解释为对数据包进行采样的网络价格。我们通过模拟由多个LTI随机控制回路组成的NCS（通过两跳蜂窝网络进行通信）来验证我们的理论主张。以及带有简单传递CC的背压式计划程序。网络和控制回路之间的接口被标识为传感器节点的缓冲区状态，从控制角度看，这可以解释为对数据包进行采样的网络价格。我们通过模拟由多个LTI随机控制回路组成的NCS（通过两跳蜂窝网络进行通信）来验证我们的理论主张。以及带有简单传递CC的背压式计划程序。网络和控制回路之间的接口被标识为传感器节点的缓冲区状态，从控制角度看，这可以解释为对数据包进行采样的网络价格。我们通过模拟由多个LTI随机控制回路组成的NCS（通过两跳蜂窝网络进行通信）来验证我们的理论主张。