Optimal controller location in wireless networked control systems

Abstract

SUMMARYThe control performance of wireless networked control systems (WNCS) has been shown to heavily depend on the packet delivery quality of both the sensor‐to‐controller and controller‐to‐actuator communications. Such quality relies on the relative distance between the wireless transmitter and receiver, which naturally raises the challenging problem of controller placement in WNCS for optimal control performance. In this paper, we investigate the optimal controller location (OCL) problem in WNCS based on linear‐quadratic‐Gaussian control strategy. For the one‐hop network case where the controller can only be placed at either the sensor side or the actuator side, we derive a simple yet effective criterion to determine the OCL. For the more general multi‐hop case where the controller can be located at either one of the sensors, relays, or actuators, we obtain the necessary and sufficient condition under which the closed‐loop system is guaranteed to be stable. On the basis of these results, we further transform the OCL problem into an optimization problem that can be solved efficiently. Numerical results are provided to verify our analysis. Copyright © 2013 John Wiley & Sons, Ltd.

Optimal linear quadratic control for wireless sensor and actuator networks with random delays and packet dropouts

“…We can see that V N À2 has the same form as equation (18). Repeating the derivation from equations (18) to (23), the optimal control law of u l, N À2 can be obtained. And similarly for other steps of u l, k , 8k.…”

“…Here, we consider a general case that both network-induced delays and packet dropouts are taken into consideration, and all of them are assumed to be independent and stochastic, such that only their distributions are known. 4,5,18,19 For a given controller located at the lth node, the sensor-to-controller (S/C) delay t sc l , the controller-toactuator (C/A) delay t ca l , and the sensor-to-actuator (S/ A) delay t tot are given respectively as…”

“…The LQ Gaussian problem has also been studied in Lin et al 17 for systems with packet losses but without acknowledgment signals of status of control packet losses. In Xin et al, 18 the necessary and sufficient conditions under which the closed-loop WSAN is guaranteed to be stable for arbitrary controller location are studied in both one-hop and multi-hop network cases. Given the predesigned control strategy, the location distribution for the optimal controller placement is found in Quevedo et al, 19 where the actuator node is assumed to have the capability to broadcast the plant state information to the intermediate nodes over parallel unreliable links.…”

Stochastic optimal linear control of wireless networked control systems with delays and packet losses

“…The optimal LQ Gaussian control problem is considered in [19] [20] with the signal estimation over lossy networks. In [21] [22], the necessary and sufficient conditions under which the closed-loop WSAN is guaranteed to be stable are studied. Note that, all works mentioned above on both WSAN and wireless NCS focus on the case of the single controller.…”

“…WirelessHART [14], ISA-100 [15]. A significant amount of works have considered WSANs under unreliable wireless communications [16][17][18][19][20][21][22] and real system applications [23,24]. In particular, the problem of optimal controller placement in multi-hop WSANs is addressed in [16,17], and it is shown that placing the controller at the actuator node achieves better performance than at the sensor node under certain conditions.…”