Earticle

The paper studies the application of a prediction-based scheme for dynamic output feedback control in a networked control system with uncertainties, communication delay and data dropout. In order to make a compensation for communication delay and data dropout, a prediction-based output control scheme is developed. With the given theoretical derivation, the closed-loop networked predictive control system with uncertainties can be formulated into a robust system with a standard form, which makes it convenient to design the controller and analysis closed-loop stability. Simulation examples demonstrate the performance and stability of a networked control system using the proposed predictive output control scheme.

This paper studies the optimal linear filtering problem for networked control systems (NCSs) with multiple packet dropouts. When the current measurement is lost, the two popular compensation mechanisms (the hold-input and zero-input mechanism) are used for compensation, respectively. The hold-input strategy means that the latest measurements received is applied directly whereas the zero-input one adopts zero value. Based on the two popular compensators, the optimal linear filters in the linear minimum variance sense are given by innovation analysis approach, and their performances are compared in terms of two simulation examples. The conclusion is that neither of the two compensation mechanisms can be claimed to be superior to the other.

Networked control systems(NCSs) have gained increasing attention in recent years due to their advantages and potential applications. The network Quality-of-Service(QoS) in NCSs always fluctuates due to changes of the traffic load and available network resources. To handle the network QoS variations problem, this paper presents an intelligent scheduling control method for NCSs, where the sampling period and the control parameters are simultaneously scheduled to compensate the effect of QoS variation on NCSs performance. For NCSs with network-induced delays and packet dropouts, a discrete-time switch model is proposed. By defining a sampling-period-dependent Lyapunov function and a common quadratic Lyapunov function, the stability conditions are derived for NCSs in terms of linear matrix inequalities(LMIs). Based on the obtained stability conditions, the corresponding controller design problem is solved and the performance optimization problem is also investigated. Simulation results are given to demonstrate the effectiveness of the proposed approaches.

This paper discusses Robust $H{\infty}$ control problems for networked control systems (NCSs) with time delays and subject to norm-bounded parameter uncertainties. Based on a new discrete-time model, two approaches of robust controller design are proposed. A numerical example and experimental verification with an NCS test bed are given to illustrate the feasibility and effectiveness of proposed design methodologies.

This paper proposes an approach to quantify the concept of resiliency in terms of Quality of Control (QoC) of a control system. Based on this concept, an intelligent resilient control algorithm (RCA) is presented for wireless networked control systems (WNCS) to maintain operational normalcy in face of wireless interference incidents, such as Radio Frequency (RF) jamming and signal blocking. The proposed algorithm closes the control loop with wireless sensors feasible by significantly increasing control system's tolerance to data packet loss and delay caused by wireless interference. The proposed algorithm, along with other well developed wireless technologies, has the potential to enable implementing wireless sensors widely in the next generation of industrial automation and control systems.

This paper is concerned with $H_{\infty}$ control of networked control systems (NCSs) with both network-induced delay and packet disordering taken into account. A switching-based method depends on different cases of prediction numbers is presented to model the NCSs as a switched system. With the application of an improved prediciton-based method to compensate for the time delay and packet disordering, $H_{\infty}$ controller is designed by solving the linear matrix inequalities (LMIs). The proposed method can be applied variously due to all kinds of prediciton numbers of the consective disordering packet have been considered, which means that our techniques are less conservative than existing literatures. Finally numerical examples and simulations are used to illustrate the effectiveness and validity of the proposed switching-based method and the improved prediction-based $H_{\infty}$ controller design synthesis.

In this paper, we discuss real-time control of networked control systems (NCSs) and practical issues in the choice of the communication networks for this purpose. An appropriate integration of control systems, real-time environments, and network communication systems allows the optimization of the quality-of-control (QoC) in NCSs. We compare several prevailing network types that may be used in control applications to offer a guideline of choosing a proper network. A real-time operating environment is also presented as an important ingredient of NCS design. To evaluate its feasibility and effectiveness, a real-time NCS containing a ball magnetic levitation (Maglev) setup is implemented via an Ethernet. Based on the experimental results, it is concluded in this paper that real-time control via Ethernet is a practical and feasible solution to NCS design.

This paper concerns the fault tolerant control for discrete networked control systems (NCSs) with probabilistic sensor and actuator fault, random delay and packet dropout. The fault of each sensor or actuator happens in a random way, which is described by an individual random variable satisfying a certain probabilistic distribution. Using these stochastic variables in the system model, new type of NCSs fault model is proposed. The merit of the proposed fault model lies in its generalization and reality, which can cover some existing fault models as special cases. By using Lyapunov functional method and linear matrix inequality technology, sufficient conditions for the mean square stable (MSS) of the NCSs can be obtained. Then the reliable controller can be designed. Finally, a numerical example and a practical example are given to demonstrate the efficiency and application of the proposed method.

This paper investigates the stabilization problem for a class of uncertain networked control systems (NCSs) with random communication network-induced delays. A dynamic output feedback controller is designed for the uncertain NCSs in the presence of network effects, i.e., network-induced delays and packet dropouts in both the sensor-controller and controller-actuator channels. Based on the Lyapunov-Razumikhin method, the existence of such controller is given in terms of the solvability of bilinear matrix inequalities. An iterative algorithm is proposed to change this non-convex problem into quasi-convex optimization problems, which can be solved effectively by available mathematical tools. The effectiveness of the proposed design methodology is verified by a numerical example.

In this paper, we develop a co-design methodology of stochastic optimal controllers and network parameters that optimizes the overall quality of control (QoC) in networked control systems (NCSs). A new dynamic model for NCSs is provided. The relationship between the system stability and performance and the sampling frequency is investigated, and the analysis of co-design of control and network parameters is presented to determine the working range of the sampling frequency in an NCS. This optimal sampling frequency range is derived based on the system dynamics and the network characteristics such as data rate, time-delay upper bound, data-packet size, and device processing time. With the optimal sampling frequency, stochastic optimal controllers are designed to improve the overall QoC in an NCS. This co-design methodology is a useful rule of thumb to choose the network and control parameters for NCS implementation. The feasibility and effectiveness of this co-design methodology is verified experimentally by our NCS test bed, a ball magnetic-levitation (maglev) system.

There is an unavoidable tradeoff between the control performance and the quality of service in networked control systems with resource constraints. To address the impact of network resources availability on requirement of bandwidth (RoB) and quality of control (QoC), an intelligent control approach to dynamic bandwidth management, namely fuzzy bandwidth management, is proposed based on fuzzy logic control technique. In order to guarantee the system's stability, the lower and upper bound of the assignable bandwidth are evaluated in terms of linear matrix inequalities and the resource constraints, respectively. In addition, the normalizable criterions of QoC and RoB are also defined, which can estimate the performance of the whole networked control systems. Preliminary simulations are carried out to highlight the merits of the proposed approach. It is argued that the proposed approach can save significant bandwidth and simultaneously improve overall control performance in comparison with the fixed bandwidth allocation and optimal bandwidth allocation.

This paper studies the problem of $H_{\infty}$ model reference tracking control for continuous time networked control systems (NCSs) with communication constraints. By using the continuous Jensen inequality, linear matrix inequality (LMI)-based $H_{\infty}$ model reference tracking controller design for nominal NCSs with controller-to-actuator communication constraints is presented, and a new method is proposed to design $H_{\infty}$ model reference tracking controllers for NCSs with both controller-to-actuator and sensor-to-controller communication constraints. The results are also extended to NCSs with norm-bounded parameter uncertainties. The merits of the proposed methods lie in their less computational complexity and less conservatism, which are achieved by adopting continuous Jensen inequality and proposing new controller design methods, respectively. The simulation results illustrate the effectiveness of the proposed $H_{\infty}$ model reference tracking controller design for NCSs with communication constraints.

This paper proposes an output feedback method to stabilize and control networked control systems (NCSs). Random time delays and packet losses are treated separately when an NCS is modeled. The random time delays in the controller-to-actuator and sensor-to-controller links are modeled with two time-homogeneous Markov chains, while the packet losses are treated by the Dirac delta functions. An asymptotic mean-square stability criterion is established to compensate for the network-induced random time delays and packet losses in both the controller-to-actuator and sensor-to-controller links simultaneously. An algorithm to implement the asymptotic mean-square stability criterion is also proposed. Further, a DC-motor speed-control test bed with Ethernet using User Datagram Protocol (UDP) is constructed and employed for experimental verification. Two sets of experiments, with and without 10% packet losses in the links, are conducted on this NCS. Experimental results illustrate the effectiveness of the proposed output feedback method compared to conventional controllers. This method could compensate for the effects of the random time delays and packet losses and guarantee the system performance and stability. The integral time and absolute error (ITAE) of the experiments without packet losses is reduced by 13% with the proposed method, and the ITAE of experiments with 10% packet losses, by 30%. The NCS can track the reference command faithfully with the proposed method when random time delays and packet losses exist in the links, whereas the NCS fails to track the reference command with the conventional control algorithms.

In this paper, we present a co-design methodology of dynamic optimal network-bandwidth allocation (ONBA) and adaptive control for networked control systems (NCSs) to optimize overall control performance and reduce total network-bandwidth usage. The proposed dynamic co-design strategy integrates adaptive feedback control with real-time scheduling. As part of this co-design methodology, a "closed-loop" ONBA algorithm for NCSs with communication constraints is presented. Network-bandwidth is dynamically assigned to each control loop according to the quality of performance (QoP) information of each control loop. As another part of the co-design methodology, a network quality of service (QoS)-adaptive control design approach is also presented. The idea is based on calculating new control values with reference to the network QoS parameters such as time delays and packet losses measured online. Simulation results show that this co-design approach significantly improves overall control performance and utilizes less bandwidth compared to static strategies.

We propose an intelligent predictive control approach for a nonlinear networked control system (NCS) with time-varying delay and random observation. The control is given by the sum of a nominal control and a corrective control. The nominal control is determined analytically using a linearized system model with fixed time delay. The corrective control is generated online by a neural network optimizer. A Markov chain (MC) dynamic Bayesian network (DBN) predicts the dynamics of the stochastic system online to allow predictive control design. We apply our proposed method to a satellite attitude control system and evaluate its control performance through computer simulation.

In this paper, a wireless control network based on IEEE 802.15.4 MAC protocol is proposed. The superframe of IEEE 802.15.4 is applied to the proposed wireless control network. The transmission and bandwidth management method are proposed for efficient transmission in the superframe. By these methods, the proposed wireless control network protocol is able to transmit three types of data (periodic data, sporadic data, and non real-time message), and guarantee real-time transmission within deadline.

1. Introduction 2. The Netwoked Control System Description 2.1 A close-loop system with the network induced delay 2.2 Discretization and State Augmentation of NCS 3. Delay-dependent H_infinity Controller Design for NCS 4. Numerical Example 5. Conclusion

This paper examines the use of a wireless Fieldbus based on IEEE 802.15.4 MAC protocol. The superframe of IEEE 802.15.4 is applied to a transmission scheme of real-time mixed data. The transmission and bandwidth allocation scheme are proposed for real-time communication using a superframe. The proposed wireless Fieldbus protocol is able to transmit three types of data (periodic data, sporadic data, and non real-time messages), and guarantee realtime transmission simultaneously within a limited timeframe.