Decentralized Auction-Based Bandwidth Allocation in a Wireless Networked Control Systems

This paper integrates the IEEE 802.11 g ad-hoc wireless network and the control area network (CAN) in the present network control systems (NCS) or wireless - NCS (WNCS). Both the TCP and the CAN protocols are adopted as the communication gateway in a remote control system. The time delay between the application layer of the client and the application layer of the remote control target has been measured and analyzed in this paper. Experimental results on an AC 400 W servo motor indicate that the communication jam mainly causes the instability due to the induced time delay. In this paper, by applying the adaptive Smith predictor with the switching sampling time, satisfactory control performance of WNCS can be obtained even though the time delay seriously increases. Moreover, the feasibility of the proposed WNCS has been proven through experimental results.

Wireless networked control system (WNCS) is given profound attention because of dynamic, flexibility and inexpensiveness. However, it is difficult to use a single simulator to simulate a WNCS which is a hybrid system. A co-simulation framework based on OPNET, Matlab and C++ is presented to capture both the system dynamics and communication events and depict the real WNCS accurately. MATLAB is good for simulating the mathematical modeling and feedback control, while OPNET is apt at simulating the WLAN communication behavior. The co-simulation framework can help WNCS designer understand and improve the performance of the WNCS.

A wireless networked control system (WNCS) consists of a dynamic system to be controlled, sensors, actuators, and a remote controller. A WNCS has two types of wireless transmissions, i.e., the sensor's measurement transmission to the controller and the controller's command transmission to the actuator. In this paper, we are surveying the literature on the communication networks in WNCSs and the challenges related to them, such as the communication standards, delay, Packet dropout, and delay jitter. Then, the control approaches in the design of a WNCS are presented, including the interactive design approaches and the joint design approaches. Also, several applications of WNCSs have been discussed in terms of their structure, functionality, and control design. These applications include Intra-Vehicle Wireless networks, Wireless Avionics Intra-Communication, Building Automation, and Water pumping. After that, security issues in WNCSs from a control engineering point of view are detailed while focusing on the major kinds of cyber attacks affecting WNCSs. Finally, future directions and conclusions are summarized at the end of the paper.

This paper aims at time-variant or uncertain wireless network delay in the wireless networked control systems (WNCS), a new Smith dynamic predictor is proposed.Because new Smith dynamic predictor hides predictor model of the network delay into real transmission process of the network data, further the network delay no longer need to be measured, identified or estimated on-line. It is applicable twosome occasions that wireless network delay is random, time variant or uncertain, possibly large compared to one, even tens sampling periods, at the same time, there are some data dropouts in closed loop. Based on IEEE 802.15.4 (ZigBee), the results of simulation show validity of the compensation scheme in the WNCS, and indicate that system has better dynamic performance and robustness.

This paper investigates the design of a robust fault detection observer for Wireless Networked Control Systems (WNCS) subject to random packet delays introduced by the wireless communication networks. The concept of input-delay analysis is adopted for analyzing the impacts of the packet delay on the residual generation, and a robust observer design and optimization method is proposed to improve the robustness of fault detection against the network induced delay. For the purpose of realistic simulation, a mixed simulation is carried out, where the control system is simulated in MATLAB and the network-induced delays are achieved by simulating an IEEE 802.11b wireless network at the recently developed OMNeT++ platform. The simulation results validate the proposed robust fault detection observer design approach.

Wireless Network Control Systems (WNCSs) have been developed and deployed in many applications because of the flexibility afforded by the wireless communications medium in accommodating the control loop. In this paper, we examine a wide area WNCS using LTE as the wireless fabric. We introduce a novel concept known as “reflection” which is a subscription model that allows an LTE eNodeB to inform certain nodes in a group about low level radio signalling from certain other nodes in the group before any application data has been sent. The mean Round Trip Time (RTT) for control in an LTE based wide area WNCS which is enhanced for reflection is reduced by at least 6ms compared to a standard LTE based wide area WNCS. This is demonstrated using an OPNET simulation model that compares a reflection based architecture with a reference architecture. The technique has applications in Smart Grid control applications (such as Fault Detection and Isolation) and in other vertical industries in which WNCSs may be relevant.

The integration of wireless communication and control systems revealed wireless networked control systems (WNCSs). One fundamental problem in WNCSs is to have a wide coverage area. For the first time in the literature, we address this problem and we obtain the maximum coverage area by solving an optimization problem. In this technical note, we consider a WNCS where the output sensor measurements are transmitted over separate heterogeneous multi-hop wireless ad-hoc subnetworks. The observation process is divided into N parts and the system state is estimated using the Kalman filter. We present the critical arrival probability for a sensor measurement packet such that if the packet arrival probability is larger than the critical value, it is guaranteed that the estimator of the WNCS converges. We derive the maximum total coverage area of the heterogeneous wireless subnetworks having maximum cost-efficiency under the constraint of the convergence of the WNCS estimator.

The Internet of things (IoT) becomes a new solution for the future industry. It aims to provide an intelligent environment to control systems in real time. We propose an embedded predictive application in the Wireless Networked Control Systems (W-NCS) to control a DC motor via RF links, under the presence of packet losses and limited size constraint of transmitted packets in the communication channel. To design an IoT predictive application in W-NCS, a Model Predictive Control (MPC) method is proposed. This strategy is developed and implemented in the embedded device by using the RIOT OS which granted maintenance costs of IoT products and offers a real-time support in the control of the systems. The proposed approach is tested in a wireless environment with an intention to be applied to tackle the problem of communication. The practical experiment results obtained demonstrate the effectiveness of the Networked Predictive Control (NPC) approach based on the W-NCS structure for this kind of problems.

A wireless networked control systems (NCS) is a control system whose feedback path is realized over a wireless communication network. The stability of such systems can be problematic given the random way in which wireless channels drop feedback messages. This paper establishes sufficient conditions for the almost sure stability of NCS under random dropouts. These conditions relate the burstiness in the dropout process to the nominal response of the controlled system. In particular, this means that the burstiness of the dropout process provides a convenient quality-of-service (QoS) constraint on the wireless channel that can be used to adaptively reconfigure the control system in a manner that guarantees the almost sure stability of the NCS. We also show how a probabilistic extension of the network calculus can be used to reconfigure multi-hop communication networks so this paper's sufficient stability condition is not violated.

In this paper, we presented a WNCS co-simulation platform based on OPNET/Simulink to verify the validity of the theory and method proposed in the study of wireless network control system (WNCS). The platform combines OPNET with Simulink, and produces the mathematical model of the control system by Simulink. OPNET simulates the network part, forming a co-simulation platform based on OPNET and Simulink. In order to simulate the real network environment more accurately, this paper added the Mobile Ad Hoc Network Routing Protocol (MANET) to the platform and carried on the secondary development of it, so as to realize the co-simulation of the control system and network environment under the framework of network protocol. Finally, through the simulation of the single-stage inverted pendulum control system in the wireless network environment, the effectiveness and good scalability of the platform were verified.

Wireless networked control systems (WNCS) over mobile ad hoc network (MANET) is a new area of research and has many potential applications, for instance, military or rescue missions, exploring hazardous environments, and so on. For performance evaluation, researchers mostly rely on computer simulations as WNCS experiments are expensive to execute. It will generate a significant benefit to conduct performance analysis of WNCS over MANET using co-simulation that utilises SIMULINK and OPtimised Network Engineering Tool (OPNET) to simulate plant/controller behaviour and the MANET, respectively. Previous conference papers by the authors reported the initial SIMULINK-OPNET co-simulation for only one network size. Here the authors present an extention of their previous work, and presents the SIMULINK-OPNET co-simulation, methodology and comprehensive simulation results that have not been reported previously. It also considers the impact of five network sizes with stationary and mobile nodes. The proposed SIMULINK-OPNET co-simulation is applied to WNCS over MANET using a realistic wireless communication model. It investigates the impact of network data rates, node mobility, the packet delay, packet drop on the system stability and performance.

In order to effectively restrain the impact of network delays for wireless networked control systems (WNCS), aiming to time-variant, random and uncertain network delays and controlled plant might be time-variant or nonlinear, as well as Smith predictor models might be imprecise, we propose a novel approach that modified Smith predictor combined with fuzzy immune self-regulating PID control for the WNCS. Because modified Smith predictor does not include network delay models, therefore, it is no need for measuring on line, identifying or estimating network delays, thus it is applicable to some occasions that network delays are larger than one, even tens of sampling periods. Based on IEEE 802.11 b/g (WLAN), the results of simulation experiment show validity of the control scheme and improvement in dynamic performance and robustness of the WNCS.

This letter considers a wireless networked control system (WNCS), where a controller sends packets carrying control information to an actuator through a wireless channel to control a physical process for industrial-control applications. In most of the existing work on WNCSs, the packet length for transmission is fixed. However, from the channel-encoding theory, if a message is encoded into a longer codeword, its reliability is improved at the expense of longer delay. Both delay and reliability have great impact on the control performance. Such a fundamental delay-reliability tradeoff has rarely been considered in WNCSs. In this letter, we propose a novel WNCS, where the controller adaptively changes the packet length for control based on the current status of the physical process. We formulate a decision-making problem and find the optimal variable-length packet-transmission policy for minimizing the long-term average cost of the WNCSs. We derive a necessary and sufficient condition on the existence of the optimal policy in terms of the transmission reliabilities with different packet lengths and the control system parameter.

Wireless Model Based Predictive Networked Control System

Markovian jumping systems have arisen naturally in the mathematical modeling of phenomena spanning disciplines in the social sciences, natural sciences, and engineering. This kind of stochastic dynamical systems can be employed to model the dynamics when parameters are subject to random abrupt changes due to sudden environment changes, subsystem switching, system noises, executor faults, and so forth. Much attention has been given to modeling, optimization, and real applications of such stochastic dynamical systems in the literature in recent years. As the advanced control and optimization will provide a basis for the design and application of such stochastic systems, these advanced techniques would result in substantial and sustainable benefits. The accepted papers in this special issue include stochastic stability, stabilization, stochastic control optimization, system modeling and identification methods, predictive control, signal processing, robust filtering, multiagent systems, networked control systems, time-delayed systems, neural networks, the Takagi-Sugeno fuzzy systems, simulated annealing, and fault detection methods.