This brief is concerned with the active fault-tolerant control (FTC) problem for an Internet-based networked three-tank system (INTTS) serving as a benchmark system for evaluating networked FTC ...algorithms. The INTTS has two parts located at Tsinghua University in China and at the University of South Wales in the U.K., respectively, which are connected via the Internet. With the INTTS as an experimental platform, the active FTC problem is investigated for a class of nonlinear networked systems subject to partial actuator failures. Once a specific actuator failure is detected and confirmed by a fault diagnosis unit, the control law is then reconfigured based on the information of the detected fault. Both the stability and the acThis brief is concerned with the active faulttolerant control (FTC) problem for an Internet-based networked three-tank system (INTTS) serving as a benchmark system for evaluating networked FTC algorithms. The INTTS has two parts located at Tsinghua University in China and at the University of South Wales in the U.K., respectively, which are connected via the Internet. With the INTTS as an experimental platform, the active FTC problem is investigated for a class of nonlinear networked systems subject to partial actuator failures. Once a specific actuator failure is detected and confirmed by a fault diagnosis unit, the control law is then reconfigured based on the information of the detected fault. Both the stability and the acceptable H ∞ disturbance attenuation level are guaranteed for the closed-loop system using the remaining reliable actuators. Extensive experiments are carried out on the active FTC problem of the INTTS with partial actuator failures, and the effectiveness of the proposed scheme is illustrated.ceptable H ∞ disturbance attenuation level are guaranteed for the closed-loop system using the remaining reliable actuators. Extensive experiments are carried out on the active FTC problem of the INTTS with partial actuator failures, and the effectiveness of the proposed scheme is illustrated.
Autonomous Boolean networks （ABNs）, which are developed to model the Boolean networks （BNs） with regulatory delays, are well known for their advantages of characterizing the intrinsic evolution rules ...of biological systems such as the gene regulatory networks. As a special type of ABNs with binary inputs, the autonomous Boolean control networks （ABCNs） are introduced for designing and analyzing the therapeutic intervention strategies where the binary inputs represent whether a certain medicine is dominated or not. An important problem in the therapeutic intervention is to design a control sequence steering an ABCN from an undesirable location （implying a diseased state） to a desirable one （corresponding to a healthy state）. Motivated by such background, this paper aims to investigate the reachability and controllability of ABCNs with pinning controllers. Several necessary and sufficient criteria are provided by resorting to the semi-tensor product tech- niques of matrices. Moreover, an effective pinning control algorithm is presented for steering an ABCN from any given states to the desired state in the shortest time period. Numerical examples are also presented to demonstrate the results obtained.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Recently, ultrathin 2D photocatalysts have attracted people’s attention due to their performances in the area of solar energy conversion. However, the synthesis of ultrathin 2D photocatalysts with a ...nonlayered crystal structure is still full of challenges. Herein, ultrathin 2D BiVO4 nanosheets (NSs) with monoclinic crystal structure are synthesized through a convenient colloidal two-phase method. The as-prepared BiVO4 NSs possess a thickness of less than 3 nm but a diameter larger than 1.2 μm. Furthermore, the presence of HNO3 facilitates the growth of BiVO4 NSs with nearly naked surfaces, largely exposed {010} planes, and widely distributed oxygen vacancies (V O) inside the crystalline structure, which are of great benefit to their photocatalytic activity under visible light irradiation. As a result, our ultrathin 2D BiVO4 NSs exhibit an impressive photocatalytic performance for water oxidation. The O2 evolution rate is 107.4 μmol h–1, and the apparent quantum yield (AQY) is as high as 26.1% (420 nm). Furthermore, by employing our ultrathin 2D BiVO4 NSs as the O2-evolving photocatalyst, Ru-SrTiO3:Rh and Fe3+/Fe2+ as the H2-evolving photocatalyst, and the redox mediator, respectively, a Z-scheme overall water splitting system is successfully constructed. Under visible light irradiation, our Z-scheme photocatalytic system presents high H2 and O2 evolution rates (16.7 and 8.0 μmol h–1) with an AQY of 1.88% (420 nm) and good photocatalytic stability.
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IJS, KILJ, NUK, PNG, UL, UM
This paper investigates the robust sliding mode control (SMC) problem for a class of uncertain nonlinear stochastic systems with mixed time delays. Both the sectorlike nonlinearities and the ...norm-bounded uncertainties enter into the system in random ways, and such randomly occurring uncertainties and randomly occurring nonlinearities obey certain mutually uncorrelated Bernoulli distributed white noise sequences. The mixed time delays consist of both the discrete and the distributed delays. The time-varying delays are allowed in state. By employing the idea of delay fractioning and constructing a new Lyapunov-Krasovskii functional, sufficient conditions are established to ensure the stability of the system dynamics in the specified sliding surface by solving a certain semidefinite programming problem. A full-state feedback SMC law is designed to guarantee the reaching condition. A simulation example is given to demonstrate the effectiveness of the proposed SMC scheme.
This paper focuses on the fault-tolerant control problem for an Internet-based three-tank system in the presence of possible sensor bias faults. The Internet-based three-tank system is an ...experimental setup that can be regarded as a typical networked system for evaluating networked fault-diagnosis and fault-tolerant control methods. Packet dropout phenomenon in the sensor-to-controller link is considered in this paper, and the fault type we deal with is chosen as the sensor bias fault. Fault-diagnosis unit is designed toward an auxiliary system. Sensor bias faults can be detected by comparing the residual signal generated by the fault detection filter and a prescribed threshold. After that, the fault can be isolated by using the residual analysis approach. Once the fault is isolated, it can be estimated iteratively in the least-squares sense. A fault accommodation method is proposed, and a fault-tolerant control strategy is achieved based on the fault information provided by the fault-diagnosis unit. The approach brought forward in this paper is demonstrated via an experimental study on the practical Internet-based three-tank system. Results show the effectiveness and the applicability of the proposed techniques.
In this paper, we deal with the robust
H
∞
filtering problem for a class of uncertain nonlinear time-delay stochastic systems. The system under consideration contains parameter uncertainties, ...Itô-type stochastic disturbances, time-varying delays, as well as sector-bounded nonlinearities. We aim at designing a full-order filter such that, for all admissible uncertainties, nonlinearities and time delays, the dynamics of the filtering error is guaranteed to be robustly asymptotically stable in the mean square, while achieving the prescribed
H
∞
disturbance rejection attenuation level. By using the Lyapunov stability theory and Itô’s differential rule, sufficient conditions are first established to ensure the existence of the desired filters, which are expressed in the form of a linear matrix inequality (LMI). Then, the explicit expression of the desired filter gains is also characterized. Finally, a numerical example is exploited to show the usefulness of the results derived.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The fact that fractional-order models possess memory leads to modeling a fractional-order HIV-immune system. We discuss the necessary conditions for the optimality of a general fractional optimal ...control problem whose fractional derivative is described in the Caputo sense. Using an objective function that minimizes the infectious viral load and count of infected T cells, the optimal control problem is solved for the fractional-order optimality system with minimal dosage of anti-HIV drugs and the effects of mathematically optimal therapy are demonstrated. Simulation results show that the fractional-order optimal control scheme can achieve improved quality of the treatment.
This paper is concerned with the filtering problem for a class of discrete-time uncertain stochastic nonlinear time-delay systems with both the probabilistic missing measurements and external ...stochastic disturbances. The measurement missing phenomenon is assumed to occur in a random way, and the missing probability for each sensor is governed by an individual random variable satisfying a certain probabilistic distribution over the interval
0
1
. Such a probabilistic distribution could be any commonly used discrete distribution over the interval
0
1
. The multiplicative stochastic disturbances are in the form of a scalar Gaussian white noise with unit variance. The purpose of the addressed filtering problem is to design a filter such that, for the admissible random measurement missing, stochastic disturbances, norm-bounded uncertainties as well as stochastic nonlinearities, the error dynamics of the filtering process is exponentially mean-square stable. By using the linear matrix inequality (LMI) method, sufficient conditions are established that ensure the exponential mean-square stability of the filtering error, and then the filter parameters are characterized by the solution to a set of LMIs. Illustrative examples are exploited to show the effectiveness of the proposed design procedures.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
In this paper, the distributed filtering problem is investigated for a class of switched nonlinear positive systems over sensor networks. The randomly varying nonlinearities and missing measurements, ...which are governed by two mutually independent Bernoulli distributed white sequences, are taken into account. Based on the output measurements of the individual sensor and its neighbors, the distributed filter with positivity constraint is designed to ensure the prescribed average l ∞ performance index of the estimation error dynamics. Special attention is paid to preserve the positivity of the underlying system as well as the sparseness of the addressed network topology. Sufficient conditions are established on the existence of the desired filters by using the linear programming approach, and the filter gains are subsequently characterized. A simulation example is provided to illustrate the effectiveness of the proposed filtering method.
In this technical note, the robust control problem is investigated for a class of stochastic uncertain discrete time-delay systems with missing measurements. The parameter uncertainties enter into ...the state matrices, and the missing measurements are described by a binary switching sequence satisfying a conditional probability distribution. The purpose of the problem is to design a full-order dynamic feedback controller such that, for all possible missing observations and admissible parameter uncertainties, the closed-loop system is asymptotically mean-square stable and satisfies the prescribed performance constraint. Delay-dependent conditions are derived under which the desired solution exists, and the controller parameters are designed by solving a linear matrix inequality (LMI). A numerical example is provided to illustrate the usefulness of the proposed design method.
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