Suboptimal Guaranteed Cost Controller Design for Networked Control Systems

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

This study is concerned with the reliable controller design for networked control systems (NCS) against both probabilistic sensors faults and actuators faults. The faults of each sensor or actuator occur randomly and their failure rates are governed by two sets of unrelated random variables satisfying certain probabilistic distribution. In terms of the probabilistic failures of every sensor or actuator, new type of distribution-based NCS fault model is proposed. Based on the new built model, reliable controller is designed and sufficient conditions for the exponentially mean square stability (EMSS) of NCS are obtained by using Lyapunov functional method. The main contribution of the proposed fault model and methods lies with its practicality and generalisation, which contains many realistic problems in the NCS, such as probabilistic sensors or actuators failures, partial degradation, data distortion, packet dropout, network-induced delay and so on. Moreover, some existing models in the open literatures are deemed as special cases of the proposed fault model. To illustrate the implementation procedure, a vertical take-off and landing (VTOL) aircraft system is given to show the effectiveness and application of the proposed method.

A mathematical model of networked control systems (NCS) with dynamic controllers is presented when the network-induced random time-varying delays of NCS are bounded and the upper bound of which is longer than one sampling period. This paper discretizes the model of continuous-time systems, applies augmented state-space method to the model and builds a discrete-time jump system model governed by a finite state Markov process. And the necessary and sufficient conditions guaranteeing stability of the system are discussed. This paper applies interior-point algorithm to design stabilizing controllers, presents a method to get the feasible initial solution and replaces Newton direction which is generally used in the interior-point algorithm with conjugate gradient direction for simplifying the algorithm. And this improved algorithm stated above is applied effectively to the networked control system of a cart and inverted pendulum with long delays.

This paper investigates the quantized guaranteed cost control design (GCCD) for networked control systems (NCSs) with interval parameters and random delays. A comprehensive NCS model is established, incorporating three key elements: Interval parameters represented as convex combinations of endpoints, random delays governed by a Markov chain, and quantization effects described by the sector‐bound method. Based on the model, sufficient conditions for the GCCD are derived using the Lyapunov functional approach combined with the cone complementary linearization (CCL) algorithm. Numerical simulations demonstrate the efficacy of the proposed method.

Event-triggered controller design of nonlinear discrete-time networked control systems in T-S fuzzy model

Communication jamming across various durations and frequencies leads to unpredictable and time-varying measurement transmission intervals in networked systems. Consequently, the discrete-time models of filtering error systems become time-dependent, thereby complicating the design of filters. This paper addresses the ongoing challenge of [Formula: see text] filtering for networked sampled-data systems subjected to communication jamming attacks. By incorporating the uncertain model within a polytopic framework, the analysis and synthesis conditions for a full-order [Formula: see text] filter are expressed as linear matrix inequalities. The proposed filter guarantees both asymptotic stability and [Formula: see text] performance under stealthy jamming attacks. A key novelty of the proposed approach is that it operates without requiring prior knowledge of the jammer's active or inactive periods. Another advantage of the method lies in its capability to tune the desired level of accuracy by increasing the number of vertices in the polytopic model, albeit at the cost of higher computational demand. Three benchmark examples are presented to demonstrate the effectiveness of the proposed strategy and to compare its performance with existing filters. The proposed filter achieves over 80% improvement in [Formula: see text] performance compared to existing methods. Its offline design and enhanced performance make it particularly suitable for networked and embedded control systems with constrained computational or communication capabilities.

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.

The performance of a networked control system (NCS) is affected directly and indirectly by time delays generated in network communication. This paper addresses these time delays, their effects on system performance and the measures taken in an NCS design. For a time delay that is random but less than one sampling interval T, we model the system as a time-invariant control system with constant time delay T. For a time delay that is random and greater than one sampling interval T, we consider the system as a control system with packet drop and model it as a jump linear control system. Based on the above models, we propose a systematic method to improve the control system quality of performance by choosing a proper sampling interval to reduce data transmission, optimally scheduling to minimise packet loss and optimising controller design in case of packet loss. The simulation results and lab experiments demonstrate that the design method results in high performance in networked real-time control system.

This paper is concerned with the problem of fault detection for networked control systems (NCS), which based on delta operator. By using delta operator, a new model is proposed, then, based on the traditional shift operator described observer-based fault detection filter design, gives the delta operator model on NCS. The problem with uncertain delay and norm bounded unknown input affect NCS robust fault detection filter design problem boils down to the H ∞ filter design. By using the linear matrix inequality (LMI), solve the H ∞ filter optimal solution, which can ensure that the unknown input delay and uncertainty robustness, but also to maximize the sensitivity of the residual signal for fault. Finally, a numerical example is provided to show the effectiveness of the proposed design method.

This article addresses the problem of controller design for networked control systems over digital communication. The systems under consideration are stabilised via state feedback, where the effects of sampled signal, state quantisation, network-induced delay and packet dropout are considered. The proposed delay-dependent stability criteria are formulated in the form of a linear matrix inequality, which ensure asymptotic stability and a prescribed H ∞ performance level for networked control systems with admissible uncertainties. Maximum allowable delay bound of networked control systems is obtained by solving a convex optimisation problem. Furthermore, a numerical example is given to illustrate the effectiveness of the main result.

In this article, the observer‐based non‐fragile tracking control problem of networked control systems (NCSs) with dynamic quantization is studied. The Takagi‐Sugeno (T‐S) fuzzy model is employed to approximate the nonlinear components of NCSs. By considering the actual network transmission process, the network bandwidth is limited, to ensure the effective transmission of information, dynamic quantizers are introduced from the T‐S fuzzy model to the observer and controller to T‐S fuzzy model. The goal is to design an observer‐based tracking controller to ensure the tracking performance of the system. A two‐step decoupling approach is employed to address the coupling terms present in the system model and the controller. The required parameters for the observer‐based tracking controller can be determined through the resolution of linear matrix inequalities (LMIs). Finally, through the establishment of the photovoltaic (PV) maximum power point tracking (MPPT) fuzzy model, the viability and practicality of the proposed method within the actual system model have been validated.

The rapid growth in the size and complexity of modern Cyber-Physical Systems (CPS) imposes increasing demand for the embedded resources, especially the communication resources. As a result, resource-efficient CPS design has become an important issue. Towards the design of networked embedded control systems, a major branch of CPS, reliable and deterministic communication is able to achieve satisfactory control performance. However, the amount of this type of resource that can be provided by the embedded platform is often limited. On the other hand, it is difficult to guarantee the control performance with non-deterministic communication resources, due to their unpredictable behavior. In this paper, we propose a novel control scheme to efficiently utilize elastic communication resources. In general, the non-deterministic communication resources are flexibly deployed on top of the deterministic communication resources to achieve stability and good control performance. In the rare worst-case, when non-deterministic communication is completely unavailable, the deterministic communication resources are used to guarantee stability and the control performance satisfying the design requirement. The experimental results show that the performance of the control application is ensured to satisfy the design requirement in the worst case and that better control performance is achieved when non-deterministic resources are available.

This work is concerned with the design of a controller for networked control system on the basis of the two disk mixed sensitivity problem. To accomplish it, the state feedback decoupling technique is used to reduce the design problem into the one of establishing filter parameters that yield a system satisfying the design specifications. The key point is that here we are concerned with both the stability and performance of the overall networked control system.

This paper considers networked control systems (NCS) with data packet dropout, NCS with data packet dropout is equivalent to a continuous time-delay system. Based on Lyapunov-Krasovskii stability theory, a new condition for stabilization of the closed-loop system by output-feedback is presented. Moreover, by using the method of free weights matrix and parameter adjusting, LMI criterion of computing maximum data packets dropout is obtained. In accordance with the criterion, convex optimal condition is obtained, then data packets dropout of the system is estimated. Finally, a simulation experiment illustrates the effectiveness of the proposed method.

The controller design techniques for Networked Control Systems (NCSs) with uncertain, time-varying network induced delay and data packet dropout is studied. A state predictor is used to predict current plant states, predicted states is used to construct control law. Combined with the state predictor, the NCS with long time delay and data packet dropout is modelled as asynchronous dynamical system with event rate constraints. Based on the model, sufficient conditions of exponential stability for NCS are given in the form of matrix inequalities. Through the feasible solution of the matrix inequalities the control law can be obtained. A numerical example demonstrates the effectiveness of the proposed method.