Class Of Large-scale Interconnected Systems Research Articles

Distributed cyber attack detection and physical fault diagnosis for a class of interconnected large-scale systems

In this paper we focus on the distributed cyber attack detection and physical fault diagnosis problem for a class of interconnected large-scale systems (ILSSs). In the proposed scheme, apart from node measurement, edge measurement is also used to construct distributed Kalman filter to estimate the state of each subsystem. The gain matrices of Kalman filter are determined by minimizing the covariance of estimation error in the attack-free and fault-free case, which reduces the false alarm rate of cyber attack detection and physical fault diagnosis. Based on this filter, a bank of adjacent residual generators is constructed to characterize the influence of cyber attack on the edge measurement, and the Chi-square test is used to detect whether the received edge measurements are attacked. At the same time, a local residual generator is constructed for each subsystem to characterize the influence of physical faults on it, and the residual signal is evaluated by variance and directional residual, so as to make distributed fault detection and isolation of each subsystem. It is worth noting that at each step, each subsystem first performs attack detection on the received edge measurements, and then estimates its own state using the attack-free edge measurements and node measurement, which further improves the accuracy of fault detection and isolation. In addition, a sufficient condition that ensuring the mean square exponential boundedness of the estimation error is given. Finally, the proposed scheme is verified by an illustrative example.

Distributed predictive control of interconnected systems based on disturbance observation

In this study, a distributed model predictive control (MPC) method based on extended state observer is proposed for a class of large-scale interconnected systems by using a reduced state-space decomposition strategy. Firstly, the full state of the system is divided into internal state and external state to decrease computation and communication burden, where the former one is used for local optimisation, and the latter one is used to exchange with its neighbours. Based on the receding optimisation strategy, a reduced state-space decomposition iterative algorithm is proposed, and the convergence of the proposed algorithm is given. To improve the disturbance rejection capability of the system, an extended state observer is designed to estimate the disturbance by using a pole assignment method. By applying a feedforward compensation strategy, a composite controller is derived by combining with local MPC controller and compensation controller, then the input-to-state stability is analysed for the closed-loop system. Finally, an example of a ship engine room power system is given to demonstrate the effectiveness of the proposed method.

Decentralized event-triggered output feedback control for a class of interconnected large-scale systems

This paper is concerned with the problem of decentralized event-triggered dynamic output feedback control for large-scale systems with unknown interconnections. By using a modified cyclic-small-gain condition and introducing a free-matrix-based integral inequality, a novel sufficient condition is derived to ensure that the overall closed-loop system is asymptotically stable with a prescribed H∞ performance. Based on this condition, a convex condition is presented to design the controller gains and the event-triggered parameters simultaneously. In contrast with the existing event-triggered results, the derived stability criterion can be applied to the large-scale systems with unmatched unknown interconnections. The effectiveness of the proposed control strategy is demonstrated by a double-inverted pendulum model.

Decentralised zero-sum differential game for a class of large-scale interconnected systems via adaptive dynamic programming

ABSTRACTIn this paper, a novel decentralised differential game strategy for large-scale nonlinear systems with matched interconnections is developed by using adaptive dynamic programming technique. First, the Nash-equilibrium solutions of the corresponding isolated differential game subsystems are found by appropriately redefining the associated cost functions accounting for the bounds of interconnections. Then, the decentralised differential game strategy is established by integrating all the modified Nash-equilibrium solutions of the isolated subsystems to stabilise the overall system. Next, the solutions of Hamilton–Jacobi–Isaaci equations are approximated online by constructing a set of critic neural networks with adaptation law of weights. The stability analysis of each subsystem is provided to show that all the signals in the closed-loop system are guaranteed to be bounded by utilising Lyapunov method. Finally, the effectiveness of the proposed decentralised differential game method is illustrated by a simple example.

Decentralised variable gain robust controller design for a class of large-scale interconnected systems with mismatched uncertainties

ABSTRACTIn this paper, we propose an LMI-based design method of a decentralised variable gain robust controller for large-scale interconnected systems with mismatched uncertainties. The mismatched uncertainties under consideration are composed of the matched part and the mismatched one, and the proposed decentralised robust controller consists of a state feedback with a fixed gain and one with a variable gain tuned by parameter adjustment laws. Sufficient conditions for the existence of the proposed decentralised variable gain robust controller are given in terms of linear matrix inequalities (LMIs). Finally, a numerical example is illustrated to validate the proposed design procedure.

An LMI-based functional estimation scheme of large-scale time-delay systems with strong interconnections

In this paper, the problem of distributed functional state observer design for a class of large-scale interconnected systems in the presence of heterogeneous time-varying delays in the interconnections and the local state vectors is considered. The resulting observer scheme is suitable for strongly coupled subsystems with multiple time-varying delays, and is shown to give better results for systems with very strong interconnections while only some mild existence conditions are imposed. A set of existence conditions are derived along with a computationally simple observer constructive procedure. Based on the Lyapunov–Krasovskii functional method (LKF) in the framework of linear matrix inequalities (LMIs), delay-dependent conditions are derived to obtain the observer parameters ensuring the exponential convergence of the observer error dynamics. The effectiveness of the obtained results is illustrated and tested through a numerical example of a three-area interconnected system.

Decentralized Finite-TimeH∞Connective Control for a Class of Large-Scale Systems with Different Structural Forms

Decentralized finite-timeH∞connective control problem for a class of large-scale interconnected systems is studied in this paper. The research aims at two structural forms, namely, the interconnected structure and the one with expanding construction. A new method is proposed to design a decentralized state feedback control law for a large-scale interconnected system so that the closed-loop system is finite-timeH∞connectively bounded. The sufficient conditions for the existence of such a decentralized control law are deduced by using LMI method. Another method is presented for a large-scale interconnected system with expanding construction which can be used without changing the decentralized state feedback control law of the original system to design a controller for the newly added subsystem so that both the new subsystem and the resulting expanded system are finite-timeH∞connectively bounded. The feasibility and effectiveness of the proposed method are verified by some simulation results.

Decentralized continuous MRAC with local asymptotic sliding modes of nonlinear delayed interconnected systems

In this contribution, we develop continuous completely decentralized state-feedback adaptive controllers with sliding mode for a class of large-scale interconnected systems with nonlinear interconnections with unknown time-varying state delays. The novel contribution of this paper is that asymptotically exact tracking within the framework of completely decentralized direct continuous adaptive control is possible also for a class of nonlinear plants with matched interconnections and disturbances.

A Decentralized Stabilization Scheme for a Class of Large-scale Interconnected Systems

AbstractIn this paper, a decentralized control approach for a class of large-scale interconnected systems is proposed. A set of local decentralized controllers is constructed to guarantee the stability of the global system utilizing the notion of superstability. The control scheme and design are based on local state information and model knowledge of the adjacent subsystems. The approach leads to a computationally efficient method where the design procedure is performed on the subsystem level using linear programming. The solutions have been optimized and it is shown that the scheme has some useful features such as monotonic convergence and robustness under interval matrix uncertainty.

Continuous Decentralized MRAC with Sliding Mode of Nonlinear Delayed Dynamic Systems

AbstractIn this contribution, we develop continuous totally decentralized state-feedback adaptive controllers with sliding mode for a class of large-scale interconnected systems with nonlinear interconnections with unknown time-varying state delays. The novel contribution of this paper is that asymptotically exact tracking within the framework of totally decentralized direct continuous adaptive control is possible also for the class of nonlinear plants considered here.

On decentralised control of non-linear interconnected systems

The asymptotic stabilisation problem of a class of large-scale interconnected systems is considered, where the non-linear interconnections between subsystems satisfy quadratic constraints that are functions of the whole system's state vector. A decentralised combined observer-controller compensator is proposed and analysed, where the subsystems’ state vectors are estimated using local sliding mode observers. The closed-loop system driven by the proposed decentralised compensator is guaranteed to be asymptotically stable subject to two conditions that are easily verifiable. Simulation results illustrate the effectiveness of the proposed decentralised combined observer-controller compensator.

Decentralized output feedback control of a class of large-scale interconnected systems

Decentralized output feedback control of a class of large-scale interconnected systems

Optimal tracking control for large-scale interconnected systems with time-delays

This paper considers an infinite-horizon optimal tracking control problem for a class of large-scale interconnected systems with state time-delays. By using the successive approximation approach, two iteration sequences of vector differential equations are constructed. Meanwhile the large-scale interconnected system is decomposed into finite decoupled subsystems. The existence and uniqueness of the optimal solution is proved, as well as the convergence of the solution sequence. By finite iterations of the solution sequence, a suboptimal tracking control law is obtained. A reduced-order reference input observer is designed to make the feedforward term of the optimal tracking control law physically realizable. A numerical example shows that the presented algorithm is effective and easy to implement.

Robust adaptive control for interval time-delay systems

This paper focuses on the robust adaptive control problems for a class of interval time-delay systems and a class of large-scale interconnected systems. The nonlinear uncertainties of the systems under study are bounded by high-order polynomial functions with unknown gains. Firstly, the adaptive feedback controller which can guarantee the stability of the closed-loop system in the sense of uniform ultimate boundedness is proposed. Then the proposed adaptive idea is extended to robust stabilizing designing method for a class of large-scale interconnected systems. Here, another problem we address is to design a decentralized feedback adaptive controller such that the closed-loop system is stable in the sense of uniform ultimate boundedness for all admissible uncertainties and time-delay. Finally, an illustrative example is given to show the validity of the proposed approach.

A decentralized model following controllers for a class of large‐scale interconnected dynamical systems with uncertainties

AbstractThe problem of decentralized robust tracking and model following is considered for a class of large‐scale interconnected systems with uncertainties. A class of linear decentralized state feedback controllers are proposed for robust tracking of dynamical signals in such a class of uncertain large‐scale systems. The proposed decentralized tracking controllers can guarantee that the tracking errors between each subsystem and local reference model are uniformly ultimately bounded. Moreover, we modify the linear controllers by introducing some nonlinear parts so that the tracking errors decrease asymptotically to zero in the presence of uncertain parameters and interconnection terms. Finally, an illustrative example is given to demonstrate the validity of our results. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 142(2): 48–58, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10101

Decentralized Robust Tracking and Model Following for Uncertain Large-Scale Interconnected Systems

The problem of the decentralized robust tracking and model following is considered for a class of large-scale interconnected systems with uncertainties. A class of continuous (nonlinear) decentralized state feedback controllers is proposed. The proposed robust decentralized controllers can guarantee that the tracking errors between each subsystem and the local reference model decrease to zero asymptotically. Finally, an illustrative example is given to demonstrate the validity of the results.

Structural properties of large-scale systems possessing similar structures

This paper discusses a class of large-scale interconnected systems composed of several subsystems with similar structure and an external system. Under some assumptions on the interconnections, it is shown that some important qualitative properties such as connectability, structural controllability, structural observability and the occurrence of structurally fixed modes for such a large-scale system can be determined by the corresponding properties for the partly decoupled system or modified subsystem corresponding to the system.

Decentralized model-based control of a class of large-scale interconnected systems

Abstract A decentralized model-based control method for stabilization and tracking control of a class of large-scale interconnected nonlinear uncertain systems is proposed, following a generalized model-based control approach for robot manipulator control. The subsystem interconnections satisfy the ‘matching conditions’, and may be nonlinear and uncertain. Three controllers are derived, with a built-in trade-off between simplicity of implementation on the one hand and accuracy of tracking/stabilization on the other. In the independent servo control method, the subsystem interactions are treated as disturbances, so possibly large gains are required under purely local feedback. In the offline feedforward compensation method, feedforward compensation is applied for nominal interactions, so much lower local feedback gains are required. In the online feedforward compensation method, the compensation is made online, improving closed loop system performance further. Local bounded stability of the interconnected ...

Decentralized robust control for a class of large-scale interconnected systems with uncertainties

The design problem of decentralized robust controllers is considered for a class of large-scale systems. The system considered in this paper is composed of interconnected subsystems with time-varying uncertainties. For such large-scale uncertain systems, we give a simple und new method whereby we can derive the sufficient conditions for asymptotically stabilizing the overall system using decentralized feedback robust controllers. An illustrative example is given to demonstrate the design procedure of the decentralized feedback robust controllers, in the light of the method developed in this paper.

Design of stable decentralized adaptive model-following controllers for large-scale systems

Abstract A decentralized model reference adaptive control for a class of large-scale inter-connected systems is developed. The proposed scheme does not require identification of the system parameters, or satisfaction of perfect model-following conditions (PMFC). The boundedness of the output error and the controller parameters is guaranteed using Lyapunov stability theory. The effectiveness of the developed algorithm is demonstrated using a numerical example.