Modeling and Protocol Design for a Class of Networked Control Systems

The state feedback absolutely stabilizing controller for a class of networked control system is designed. Supposed that the network time-delay is random, the networked control system that the plan is a class of time-delay systems with nonlinearities satisfying a given sector condition is modeled as a hybrid system. Furthermore, the Lyapunov-Krasovskii function and linear matrix inequality methods are used to derive a sufficient condition, which can guarantee that the networked control system is absolute stable. Based on the sufficient condition, in terms of convex optimization techniques, the controller and the maximum allowable transfer interval are obtained easily. The numerical and simulation example are presented to demonstrate the effectiveness of the approach.

This paper is concerned with the robust stabilization problem for a class of networked control systems with nonlinear perturbations. The perturbations are assumed to be time-varying and satisfying quadratic constraints. Such networked control systems are modeled as systems with time-varying delays. Based on this model, observer-based controllers are designed to stabilize the nonlinear systems subject to the network-induced delay and data dropout. Sufficient conditions on existences of the stabilizing controllers are established. The controller gains can be obtained by solving a set of linear matrix inequalities. An illustrative example is given to demonstrate the effectiveness of the proposed method.

In this paper, stability and disturbance attenuation issues for a class of networked control systems (NCSs) under uncertain access delay and packet dropout effects are considered. Our aim is to find conditions on the delay and packet dropout rate, under which the system stability and H/sup /spl infin// disturbance attenuation properties are preserved to a desired level. The basic idea in this paper is to formulate such networked control system as a discrete-time switched system. Then the NCSs' stability and performance problems can be reduced to corresponding problems for the switched systems, which have been studied for decades and for which a number of results are available in the literature. The techniques in this paper are based in the discrete-time switched systems and piecewise Lyapunov functions.

Connecting a complex control system with various sensors, actuators, and controllers as a networked control system by a shared data network can effectively reduce complicated wiring connections. This system is also easy to install and maintain. The trend is to use networked control systems for time-sensitive applications, such as remote DC motor actuation control. The performance of a networked control system can be improved if the network can guarantee quality-of-service (QoS). Due to time-varying network traffic demands and disturbances, QoS requirements provided by a network may change. In this case, a network has to reallocate its resources and may not be able to provide QoS requirements to a networked control application as needed. Therefore, the application may have to gracefully degrade its performance and perform the task as best as possible with the provided network QoS. This paper proposes a novel approach for networked DC motor control systems using controller gain adaptation to compensate for the changes in QoS requirements. Numerical and experimental simulations, and prototyping, are presented to demonstrate the feasibility of the proposed adaptation scheme to handle network QoS variation in a control loop. The effective results show the promising future of the use of gain adaptation in networked control applications.

Driven by recent telecommunication demand, shared communication channels are more abundant today than ever before. These shared wired/wireless networks for communication are being exploited more and more in control systems to connect sensors, controllers and actuators resulting in so-called networked control systems (NCSs). NCSs replace the more traditional control systems where dedicated point-to-point (wired) connections are being used. The advantages of using NCS technology are inexpensive and easily modifiable communication links which allow control algorithms to be easily implemented in situations where dedicated connections are not possible (either economically or physically). However, the drawback is that the control system is susceptible to undesirable (possibly destabilizing) side-effects such as time-varying transmission intervals, time-varying delays, packet dropouts, quantization and a shared communication medium. These network-induced effects undermine fundamental assumptions on which traditional control theory is built and, therefore, it is essential to develop new techniques and tools that can be used to analyze and/or design control systems which communicate via a shared network. This thesis advances NCS analysis and design methodologies by contributing new theoretical developments, new software tools and new experimental validation results. The first new theoretical development is in the area of analyzing robust stability properties with respect to network-induced effects. A sum of squares (SOS) approach for a class of nonlinear NCSs incorporating bounded time-varying delays, bounded time-varying transmission intervals and a shared communication medium is developed. Mathematical models that describe these nonlinear NCSs are cast into suitable hybrid system formulations. Based on these hybrid system formulations, (families of) Lyapunov functions are constructed using SOS techniques. Amongst other benefits, it is shown that this technique improves the guaranteed robustness margins compared to existing work. The second new theoretical development concerns the design of networkaware decentralized controllers guaranteeing robust stability properties with respect to network-induced effects. We develop one of the first approaches based on semidefinite programming techniques to synthesize stabilizing decentralized observer-based output-feedback controllers for linear plants where the controllers, sensors and actuators are connected via a shared communication network subject to time-varying transmission intervals and delays. To effectively deal with the shared communication medium, a switched observer structure is adopted that switches based on the transmitted measured outputs and a switched controller structure is also adopted that switches based on the transmitted control inputs at each transmission time. By taking a discrete-time switched linear system perspective on modeling these decentralized NCSs, we are able to derive a general model that captures all these networked and decentralized control aspects. We provide linear matrix inequality (LMI)-based synthesis conditions which, if satisfied, provide stabilizing observer-based controllers that are both decentralized and robust to network effects. Regarding new software tools, the first prototype of a toolbox is developed to automate (robust) stability analysis (and controller design) for NCSs. Specifically, it is shown that the toolbox can be employed to efficiently verify if a linear time-invariant (LTI) plant and an LTI controller interconnected with a shared network are robust to certain network imperfections. The main intention of the toolbox is to make the available theory readily accessible to and applicable for the general control community. Additionally, the chosen software structure enables the incorporation of custom models or custom stability/performance analysis conditions in an easy manner, thereby allowing the control community to contribute and to further develop the toolbox. Finally, an experimental case study involving a wirelessly controlled inverted pendulum/cart system is investigated. In particular, the communication network itself is analyzed such that the network-induced effects can be characterized in terms of bounds on the transmission intervals and transmission delays. Based on these bounds, the prototype toolbox is applied to analyze the robustness regions for different performance specifications, which aid in tuning the controller to achieve more closed-loop robustness with respect to the network-induced effects. This leads to a validation of the developed theory in an experimental setting. In addition to the validation of the developed theory, many new insights into the network behavior are obtained and explained, thereby raising new interesting questions for future research on NCSs.

Due to major advancements in the area of networking over the past decade, a new paradigm of control systems has emerged, namely networked control systems. Such systems differ from classical control systems in that their control loops are closed around communication networks. Thus, the need for new stability and performance guarantees arises. In this paper, we aim to shed some light on the major advancements and inherent problems in networked control systems.

Design, Analysis and Real-time Implementation of Networked Predictive Control Systems

SummaryIn this paper, the multi‐tasking optimal control problem is addressed in the delta‐domain for a class of networked control systems (NCSs) with external disturbances. A delta‐domain model is proposed to describe the NCSs with random packet dropouts and long‐time delay, and the so‐called ε‐Nash equilibrium is employed to quantify the impacts from the disturbances on the underlying NCSs. The multi‐tasking optimal control strategies are developed and the upper bound for the ε‐Nash equilibrium is provided explicitly. Some simulation results on the two‐area load frequency control system are given to show the validity and applicability of the proposed method. Copyright © 2016 John Wiley & Sons, Ltd.

In this paper, the time-delay compensation control of a class of networked control system (NCS) with randomly varying long time-delays is addressed. Firstly, we give a novel modeling method which is easy to implement time delay compensation. By prediction of a model-based estimator in the controller node and building buffers in the actuator node, the NCS with delayed state feedback is compensated. A linear matrix inequality based (LMI-based) sufficient condition for stability of the NCS with time-delay compensation is derived. The simulation results of an Internet-based continuous stirred tank reactor (CSTR) demonstrate the efficiency and correctness of our compensation method.

This paper is concerned with <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> -design for a class of networked control systems (NCSs) with multiple state-delays via the Takagi-Sugeno (T-S) fuzzy model. The transfer delays and packet loss that are induced by the limited bandwidth of communication networks are considered. The focus of this paper is on the analysis and design of a full-order <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> filter, such that the filtering-error dynamics are stochastically stable, and a prescribed <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> attenuation level is guaranteed. Sufficient conditions are established for the existence of the desired filter in terms of linear-matrix inequalities (LMIs). An example is given to illustrate the effectiveness and applicability of the proposed design method.

Observer-based fault-tolerant control for a class of networked control systems with transfer delays

Input-to-state stability for networked control system with predictive scheme

Aiming at a class of networked control systems (NCSs) in the presence of network-induced delay and data packet dropout simultaneously from sensor to controller, a new optimal controller design method is proposed based on particle swarm optimization (PSO) with predatory search strategy. The rough feedback gain and its feasible region are firstly obtained through the state feedback control (SFC) approach, and then, the feed back gain is optimized in the obtained feasible region via improved PSO. The proposed controller can effectively reduce the conservatism of control methodology and improve the performance of whole system. The simulation results demonstrate that the proposed method is valid and effective.

Delay-dependent stability criteria for a class of networked control systems with multi-input and multi-output☆

Networked control systems (NCS) consist of sensors, actuators and controllers the operations of which may be distributed over geographically disparate locations and co-ordinated by the exchange of information passed over a communication network. The communication network may be physically wired or not. The widespread applications of the Internet have been a major driving force for research and development of NCS. NCS have advantages in terms of cost reduction, system diagnosis and flexibility, minimizing wiring and making the addition and replacement of individual elements relatively simple; efficient data sharing makes taking globally intelligent control decisions easier with an NCS. The applications of NCS are very wide, from the large scale of factory automation and plant monitoring to the smaller but complicated networks of computers in modern cars, places and autonomous robots. Networked Control Systems presents the most recent results in stability and robustness analysis as well as new developments related to networked fuzzy and optimal control. Many of the chapters contain details of case-studies, experimental, simulation and/or other application-related work showing how the theories put forward can be implemented in real systems. The state-of-the art research reported in this volume by an international team of contributors will make Networked Control Systems an essential reference for researchers and postgraduate students in control, electrical, computer and mechanical engineering and computer science.