Search

This paper proposes a specific algebraic structure and demonstrates its nature as an extension field, enabling the construction of Golomb Costas (GC) arrays. It provides detailed instructions and examples for constructing GC arrays using this extension field, along with a corresponding flowchart. Additionally, the paper conducts a thorough analysis, incorporating calculations and comparisons, to evaluate the autocorrelation of a GC array derived from the extension field compared to that of a diagonal frequency hopping array. The analysis reveals the superior autocorrelation properties of GC arrays based on the extension field. Furthermore, the paper establishes a mathematical model for the signal coded by the frequency hopping array and subsequently simulates and compares the ambiguity function of the signal coded by a GC array with that of a signal coded by a diagonal frequency hopping array. This comparison underscores the thumbtack ambiguity function of frequency hopping signal coded by a GC array. Moreover, the paper thoroughly investigates the relationship between the correlation function of GC arrays and the roots of an algebraic equation in a finite field, and strictly proves the ideal autocorrelation properties of Golomb Costas arrays. [ABSTRACT FROM AUTHOR]

This paper is concerned with the synchronization of stochastic uncertain complex dynamic networks with time‐varying delays. In contrast to existing synchronization network models, the current study considers both internal time‐varying delays and coupling time‐varying delays. By analyzing the two factors (i.e. time‐varying delays and uncertainties) on the synchronization performance of stochastic uncertain complex dynamic networks, a new inverse optimal adaptive control is proposed. The analysis tool developed in this paper is based on Lyapunov technique, algebraic graph theory and inverse optimality, which does not need to solve Hamilton‐Jacobi‐Bellman equation. Some sufficient conditions are established for the synchronization of stochastic uncertain complex dynamic networks with time‐varying delays. To demonstrate the effectiveness of the present approach, simulation results are illustrated. In this paper, we consider the synchronization of stochastic uncertain complex dynamic networks with time‐varying delays. Different from the existing synchronization of the networks model, we take the internal time‐varying delays and the coupling time‐varying delays into account. By analyzing the two factors (i.e. time‐varying delays and uncertainties) on the synchronization performance of stochastic uncertain complex dynamic networks, a novel inverse optimal adaptive control is proposed. The analysis tool developed in this paper is based on Lyapunov technique, algebraic graph theory and inverse optimality, which does not need to solve Hamilton‐Jacobi‐Bellman equation. Some sufficient conditions are established for the synchronization of stochastic uncertain complex dynamic networks with time‐varying delays. [ABSTRACT FROM AUTHOR]

This paper presents an edge‐based event‐triggered delay distributed algorithm for solving the economic dispatch problem (EDP) in smart grids. The objective of the EDP is to minimize the total generation cost by allocating power to individual generators, each with its local generation constraint. To save the overhead of communication resources between agents, an edge‐based event‐triggered mechanism is suggested. By setting distinct triggering thresholds for each communication edge, the agent may efficiently regulate the communication frequency among all neighbors. However, in practice, owing to the instability of the network, the agent may receive information regarding its neighbors, leading to communication lags for every communication link. The virtual agent technique and double‐stochastic matrix augmentation technique provide an equivalent delay‐free EDP. It is demonstrated that the proposed algorithm can asymptotically converge to the global optimal solution as long as the communication delay is arbitrary, time‐varying, and random, but bounded. Objective and clear evidence is provided through a case study in smart grids to verify the algorithm's feasibility. [ABSTRACT FROM AUTHOR]

The Chang'E‐5 (CE5) ascender achieved lunar orbit autonomous rendezvous and docking with orbiter‐returner successfully on 5 December 2020. Same‐beam Very Long Baseline Interferometry (VLBI) (SBI) observations were performed for the first time for autonomous rendezvous and docking in lunar orbit. In this paper, by studying the CE5 rendezvous and docking data observed by the Chinese VLBI network and analyzing the residual differential phase delay of the autonomous control phase, we successfully captured the maneuver of the 5 km holding of the orbiter‐returner. The differential phase delay (DPD) data of the far‐range guidance phase were used to perform orbit determination of the ascender and orbiter‐returner successfully. The results of orbit determination show that the DPD data can improve the relative position accuracy between the ascender and the orbiter‐returner, and the residual root mean square of the DPD data is 5 ps. Furthermore, when one of the probes has only DPD data, its orbit can also be determined. Key Points: The Chinese Very Long Baseline Interferometry (VLBI) network observes the autonomous rendezvous and docking of Chang'E‐5 in lunar orbit using Same‐beam VLBIThe residual differential phase delay monitors the maneuver of the orbiter‐returner in the autonomous control phaseThe differential phase delay improves the relative position accuracy between two probes in the far‐range guidance phase [ABSTRACT FROM AUTHOR]

Carbon footprint monitoring provides significant basis for computing facilities to improve the computing efficiency and reduce the energy cost, which can enable low/zero carbon computing and facilitate the construction of sustainable cites. Massive sensing devices access to 5G base station to transmit collected carbon emission data, which requires intelligent access management. Fast uplink grant possesses the advantages of reducing signalling overhead and access conflicts while facing the problems of incomplete information and difficulty in guaranteeing priority constraint. This paper examines, the maximum access queuing delay minimization problem is formulated under the long‐term service priority constraint and the short‐term access management constraint. First, Lyapunov optimization is leveraged to decouple the long‐term service priority constraint and short‐term access management optimization, and decompose the long‐term stochastic optimization problem into a series of short‐term deterministic problems. Then, a priority‐aware deep Q‐network (DQN)‐based fast uplink grant access management (PDAC) algorithm is proposed to achieve intelligent access management with differentiated service priority requirements. PDAC utilizes DQN to handle non‐convex high‐dimensional optimization problem with service priority constraint to achieve intelligent access management and priority awareness. Simulation results demonstrate that PDAC outperforms the existing algorithms in access queuing delay, buffer queue backlog, and priority deficit fluctuation. [ABSTRACT FROM AUTHOR]

When a DC line fault happens, the converter will be blocked instantly. This leads to an interruption of power transmission and influences the stability of DC and AC systems. To avoid the blocking of converters, this paper presents a novel protection scheme for VSC-HVDC system, which consists fault isolation and auto-reclosing of DC circuit breaker (DCCB). First, this paper coordinates the protective actions of converters and DCCB. The DC line fault is cut immediately by DCCB while the blocking signal of converter is isolated during the fault. Second, since the faults of long overhead transmission DC lines are mostly transient, an auto-reclosing strategy is developed. The emphasise of this part, which includes fault discrimination and time sequences, between DCCB and converter is elaborated, and the value of reclosing delay is derived by analysing the charging and discharging characteristics of capacitor paralleled with converter. Finally, the protection scheme is evaluated by overcurrent, overvoltage, and recovery time of DC system, and simulation results of a point-to-point VSC-HVDC transmission system proves its validity. [ABSTRACT FROM AUTHOR]

Summary: Systems in real world are always subject to perturbations. This paper addresses the convergence properties of a class of nominal systems with perturbations. It is assumed that the nominal system is a switched nonlinear exponentially stable one with time‐varying delays and that the perturbation exponentially or asymptotically converges to zero. It is revealed that the trajectories of the perturbed system behave as the perturbation, ie, trajectories exponentially or asymptotically converge to zero, depending on the property of perturbation. Applying these results to cascade switched nonlinear systems, it is shown that such systems are exponentially stable if and only if all the subsystems, obtained by removing the coupling terms, are exponentially stable. A similar conclusion is presented for systems being asymptotically stable. Finally, a numerical example illustrates the proposed theoretical results. [ABSTRACT FROM AUTHOR]

Actuator rate limit phenomenon is ubiquitous in control systems, but it has always been neglected in practical engineering. Especially, few papers are published to investigate the system identification while considering the rate limit. Step function is commonly used in parameter estimation and its first‐order derivative at the step time goes to infinity, which is not affordable by real actuators. As a result, the rate limit slows down the system response speed, misleads the parameter identification, and subsequently affects the controller design and deteriorates the control performance. This study proposes both graphical method and curve fitting method to identify the first‐order plus time‐delay (FOPTD) systems with consideration of the actuator rate limit effect whose limit value is unknown. Quantitative analyses of the parameter mismatch in the traditional FOPTD model and parameter sensitivity analyses are also carried out. Both simulation results and experimental results have shown the necessity and feasibility of defining a new model structure which includes the rate limit value. [ABSTRACT FROM AUTHOR]

This paper presents the development of a new double integral inequality (II) with the motivation of yielding quadratic approximation. It is well known that approximating integral quadratic terms with quadratic terms involves a certain degree of conservatism. In this paper, a sufficient gap has been identified in the approximation of two recent IIs reported in the literature, thereby leading to the new double II. The developed inequality has been applied to access the stability of a linear retarded system to estimate a maximum delay upper‐bound. Furthermore, a mathematical relationship of the new double II with existing inequalities is discussed to show that the developed inequality is more general, effective and bears less computational burden. Four numerical examples are given to validate the authors' claim with regard to the effective estimate of delay bound results for a linear retarded system. [ABSTRACT FROM AUTHOR]

This paper deals with robust stability and stabilization of linear discrete-time systems subject to uncertainties and network constraints. In network control systems, the control loop is closed over a network, which induces additional dynamics to the original control loop such as delays, sampling, and quantization among many others. This paper focuses on networked induced delays due to unreliable network for which packet losses may occur. An equivalent periodic-like representation of the resulting system is proposed. This allows first to revisit existing results in this framework and second to take model uncertainties into account by analyzing the closed-loop model by means of a recent method based on robust control for discrete-time time-varying systems. Stability analysis and dynamic state-feedback stabilization are characterized via new conditions, whose conservatism is extensively discussed. Effectiveness of the proposed methodology is illustrated by numerical examples. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Objectives: Little is known about the experiences of women who travel within Europe for abortion care from countries with relatively liberal laws. This paper aims to assess the primary reasons for travel among a sample of women who travelled from European countries with relatively liberal abortion laws to obtain abortion care mainly in the UK and the Netherlands. Design: Multi‐country, 5‐year mixed methods study on barriers to legal abortion and travel for abortion. Setting: UK, the Netherlands and Spain. Population or Sample: We present quantitative data from 204 surveys, and qualitative data from 30 in‐depth interviews with pregnant people who travelled to the UK, the Netherlands and Spain from countries where abortion is legal on broad grounds within specific gestational age (GA) limits. Methods: Mixed‐methods. Main outcome measures: GA when presenting at abortion clinic, primary reason for abortion‐related travel. Results: Study participants overwhelmingly reported travelling for abortion because they had exceeded GA limits in their country of residence. Participants also reported numerous delays and barriers to receiving care. Conclusions: Our findings highlight the need for policies that support access to abortion throughout pregnancy and illustrate that early access to it is necessary but not sufficient to meet people's reproductive health needs. Funding: This study is funded by the European Research Council (ERC). This study shows that GA limits drive women from EU countries where abortion is legal to seek abortions abroad. This study shows that GA limits drive women from EU countries where abortion is legal to seek abortions abroad. [ABSTRACT FROM AUTHOR]

The delay‐dependent stability problem for systems with time‐delay varying in an interval is addressed in this study. Based on Lyapunov–Krasovskii theory the proposed methods formulated as linear matrix inequality problems are able to check the stability interval when the time‐varying delay d (t) belongs to an interval [τ1, τ2]. The Lyapunov–Krasovskii functional (LKF) selected in the present paper is simpler than some ones considered in the literature. However, the criteria obtained, based on this simple LKF, outperformed the similar existing ones in all numerical tests accomplished in this paper. Notation: Through out this paper the superscript T stands for transpose. 0 refers to a null matrix with appropriate dimensions. For a real symmetric matrix M, the notation M > 0 (< 0) means that M is the positive (negative) definite. The symmetric term in a matrix is denoted by *. [ABSTRACT FROM AUTHOR]

This paper revisites the direct synthesis tuning method of continuous‐time low‐order controllers, and specially PID controllers, for control of time‐delayed single‐input single‐output processes. A setpoint prefilter is included to improve the servo response and integrating load disturbances are accounted for. Robustness is addressed by the feedback controller to obtain the desired maximum sensitivity value. Similar results in step disturbance compensation are obtained with simpler analytical tuning rules when compared to recently reported methods. However, the proposed procedure enables to compensate integrating load disturbances, which are not handled in the other methods. [ABSTRACT FROM AUTHOR]

This study demonstrates how a dynamic, aging chain model can support strategic decisions in workforce planning. More specifically, we used a system dynamics model (a modeling and simulation technique originating from supply chain management) to improve the recruiting and training process in a large German service provider in the wider field of logistics. The key findings are that the aging chain of service operators within the company is affected by a variety of delays in, for example, recruiting, training, and promoting employees, and that the structure of the planning process generates cyclic phases of workforce surplus and shortage. The discussion is based on an in-depth case study conducted in the service industry in 2008. Implications are that planning processes must be fine-tuned to account for delays in the aging chain. The dynamic model provides a tool to gain insight into the problem and to improve the actual human resource planning process. The value of the paper lies in the idea of applying a well-known and quantitative method from supply chain management to a human resource management issue. © 2010 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Summary: This paper is concerned with the delay‐dependent exponential stability analysis of two‐dimensional (2D) discrete switched systems with state delays described by the Roesser model; the delays under consideration are varying. By constructing an appropriate Lyapunov‐Krasovskii functional and using the average dwell time approach, new delay‐dependent sufficient conditions for the exponential stability of the system under study are proposed. In order to obtain less conservative conditions, the delay partitioning method is adopted as well as the free‐weighting matrix technique. The proposed conditions are formulated in the format of linear matrix inequality. The effectiveness and the reduced conservatism of the developed results are shown by illustrative examples. [ABSTRACT FROM AUTHOR]

Motivated by Markovian regime‐switching diffusion (MRSD), time‐varying delays and non‐linear coupling forms, this study is concerned with stabilisation of coupled regime‐switching diffusion with time‐varying delays (CRSDTD) under periodically intermittent control. Compared with most papers investigating MRSD, a striking feature of regime‐switching diffusion is that in the two‐component process (x(t),α(t)), switching process α(t) depends on the diffusion x(t), which can be regarded as the x ‐dependent process briefly. It is worth mentioning that time‐varying delays and non‐linear coupling forms are taken into consideration when modelling, which makes their work more realistic. Moreover, a periodically intermittent controller is adopted to guarantee that CRSDTD can achieve the p th moment exponential stability and some sufficient conditions are derived by using the Lyapunov method and Kirchhoff's matrix tree theorem. Furthermore, to illustrate the applicability of their theoretical results, an application to regime‐switching coupled oscillators with time‐varying delays (RSCOTD) is presented and a stability criterion is given. Conclusively, numerical simulations on RSCOTD are presented to illustrate the effectiveness of the theoretical results. [ABSTRACT FROM AUTHOR]

This paper addresses the stability and control problem of the linear positive two‐dimensional (2‐D) continuous‐time systems in Roesser model with multiple time delays. The contribution lies in two aspects. First, a simple novel proof is provided to establish necessary and sufficient conditions of asymptotic stability for 2‐D continuous delayed systems. It turns out that the magnitude of delays has no any impact on the stability of these systems, which is completely determined by the system matrices. Second, a necessary and sufficient condition for the existence of state‐feedback controllers is proposed for general delayed 2‐D systems, which ensures the non‐negativity and the stability of the resulting closed‐loop systems. Two examples are given to validate the proposed methods. [ABSTRACT FROM AUTHOR]

In this study, the authors consider the state estimation problem for a class of non‐linear systems with unknown time‐varying delays. Based on the H∞ filtering method, they propose a new observer design approach where the states of the non‐linear systems with unknown delays can be robustly estimated. While relevant results in the literature assume the unknown delays to be differentiable, the observer design proposed in this study only requires the knowledge of the unknown delays' upper and lower bounds which can be obtained in practical systems. The new observer design approach also allows us to consider delays in the output measurements. They further utilise the linear parameter varying approach to relax the conservativeness imposed on observer design conditions by the Lipschitz conditions. To show the effectiveness of the new results, the single‐link joint robotic system and the pendulum system are considered as illustrative examples. [ABSTRACT FROM AUTHOR]

This paper addresses the stabilization problem of neutral systems. The neutral systems assumed to be subjected to nonlinear perturbations and mixed time-varying delays. Specifically, the adaptive control method is used to stabilize the unknown neutral systems. If the system states and the delayed states with its derivatives are available for measurement, a new and less conservative adaptive control algorithm is proposed, and sufficient conditions for the existence of the adaptive control are derived based on Lyapunov's stability theory. The main idea is to make all the stability conditions of the system depend on desired arbitrary matrices, not on the given system matrices. This is accomplished by the adaptation process. Illustrative examples with numerical simulations are studied. The simulation results show the effectiveness of the proposed design methods. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this paper, a probabilistic approach is proposed to study the modeling, stability, and stabilization problems for networked control systems (NCSs) with simultaneous random network communication delay and data dropout. Different from existing modeling approaches, the proposed NCSs model naturally captures the stochastic characteristics of the considered NCSs by taking into account the effects of the random network communication delay and data dropout. Based on the developed NCSs model, necessary and sufficient conditions of stability analysis, state, and output feedback stabilization problems are tackled. Moreover, necessary and sufficient stability and stabilization conditions are also presented for the case when the occurrence probabilities of delay and data dropout are partially known. Finally, three numerical examples are provided to demonstrate the effectiveness and the reduced conservatism of the proposed method. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Cocoa mirid, Sahlbergella singularis, is one of the major pests of cocoa in West Africa. It is responsible of several damages in plots. In this paper, we study the dynamics of this pest. Based on biological and ecological partial knowledge, we develop 2 cooperative mathematical models that aim to describe the time dynamics of the cocoa mirids. We first develop a cooperative stage‐structured model, derived some qualitative results, and a sensitivity analysis study in order to determine the most important parameters. Assuming that all parameters are or not periodic, we obtain conditions that allow the persistence or not of the population. We highlight the influence of cocoa pods variation along the year on the time evolution of the population. Then, we derive a 2‐stage cooperative time‐delay model, with 2 delays, that takes into account the eggs' development time and the females' maturation time. We illustrate our theoretical results with some simulations and show that the delayed system provides the best results compared with real observations. Finally, we focus on chemical control that is commonly used in Cameroon and compare it to a new biological control, mixing mating disrupting and trapping. We discuss the results and provide future perspectives based on this work. [ABSTRACT FROM AUTHOR]

Cocoa mirid, Sahlbergella singularis, is one of the major pests of cocoa in West Africa. It is responsible of several damages in plots. In this paper, we study the dynamics of this pest. Based on biological and ecological partial knowledge, we develop 2 cooperative mathematical models that aim to describe the time dynamics of the cocoa mirids. We first develop a cooperative stage‐structured model, derived some qualitative results, and a sensitivity analysis study in order to determine the most important parameters. Assuming that all parameters are or not periodic, we obtain conditions that allow the persistence or not of the population. We highlight the influence of cocoa pods variation along the year on the time evolution of the population. Then, we derive a 2‐stage cooperative time‐delay model, with 2 delays, that takes into account the eggs' development time and the females' maturation time. We illustrate our theoretical results with some simulations and show that the delayed system provides the best results compared with real observations. Finally, we focus on chemical control that is commonly used in Cameroon and compare it to a new biological control, mixing mating disrupting and trapping. We discuss the results and provide future perspectives based on this work. [ABSTRACT FROM AUTHOR]

Modern power system involves growing use of open channel communication in secondary frequency regulation which introduces time delay in the automatic generation control loop which may lead to system instability. This study proposes a novel power system frequency stabiliser (PSFS) which is a modified secondary controller in order to improve the system stability in the presence of large communication delays. An auxiliary signal is added to the secondary controller to provide additional damping. The gain of the controller is obtained by meta‐heuristic methods. The proposed controller is first developed on a single area hydropower system and the same is then applied on the Western System Coordinating Council 3‐machine, 9‐bus power system. Furthermore, to show the effectiveness of the proposed PSFS in a large practical multi‐area system; it is also applied to the IEEE 39‐bus system. Results show that the proposed controller significantly improves the stability of a power system operating with large communication delay which is first considered as constant and then the stability improvement with the proposed PSFS in the presence of random communication delays is also shown. The PSFS performance is tested by the results obtained with MATLAB/Simulink simulations and further verified on a real‐time simulator. [ABSTRACT FROM AUTHOR]

This paper addresses the mean square consensus problem of leader‐following stochastic multi‐agent systems using a distributed event‐triggered control strategy. For each involving agent, generally, the time‐varying (or fixed) delay between controller and actuator is unavoidable. The controller is updated only when the event condition is triggered. Based on the Lyapunov function method and Itô formula, three sufficient conditions for leader‐following mean square consensus are established, including a delay‐independent consensus condition and a delay‐dependent criterion for the case with input fixed time delay, and a consensus criterion for the case with input time‐varying delay. Furthermore, an inter‐event time lower bound between two sampling points is derived. The results are illustrated through several numerical examples. [ABSTRACT FROM AUTHOR]

Converting the surplus power into rotor kinetic energy by changing the control functions of machine side converter (MSC) and grid side converter (GSC) is considered to be an efficient way for permanent magnet synchronous generator (PMSG)‐based wind turbine generator system (WTGS) to accomplish low‐voltage ride through (LVRT) without additional hardware components. However, because of the time delay of grid fault detection and the control system inertia, the dc‐link capacitor may still be subjected to overvoltage in the early tens of milliseconds after a grid fault happens. This study proposes a compositive control method of LVRT for PMSG‐based WTGS, in which the surplus power during LVRT is converted into rotor kinetic energy by controlling the electrical power of the PMSG according to the grid‐connected power of the GSC, and a crowbar circuit is reserved to consume the surplus power before MSC reacts to the grid fault. The proposed method does not change the control functions of MSC and GSC, and the related control parameters resetting can be avoid. Besides, it can also provide reactive power support to assist the grid voltage recovery. Simulations and experiments proved the proposed method to be feasible and effective. [ABSTRACT FROM AUTHOR]

Connected and automated vehicles (CAVs) are being developed and designed to operate on existing roads. Their safe and efficient operation during roadworks, where traffic management measures are often introduced, is crucial. Two alternative measures are commonly applied during roadworks on motorways: (i) closing one or multiple lanes (ii) narrowing one or all lanes. The former can cause delays and increased emissions, while the latter can pose safety risks. This study uses a VISSIM‐based traffic microsimulation to compare the effectiveness of these two strategies on traffic efficiency and safety, considering various market penetration rates (MPR) of CAVs. The model was calibrated and validated with the data collected from M1 motorway in the United Kingdom. Results show that average delays per vehicle‐kilometre‐travelled decreased from 102.7 to 2.5 s (with lane closure) and 23.6 to 0.6 s (with narrow lanes) with 0% and 100% CAV MPR, respectively. Moreover, safety in narrow lanes improved by 4.8 times compared to 1.5 times improvement in lane closure with a 100% CAV MPR; indicating that narrow lanes would result in better safety performance. These findings could assist transport authorities in designing temporary traffic management measure that results in better CAV performance when navigating through roadworks. [ABSTRACT FROM AUTHOR]

Concurrent multipath transfer (CMT) is a transport layer protocol used for transferring data over multiple paths concurrently. In the case of asymmetric paths, the dissimilarity of delay, bandwidth, and loss rate among paths leads to challenges such as out‐of‐order packets, receiver buffer blocking, and throughput reduction. A framework that uses the end‐to‐end delay of paths to distribute the packets over asymmetric paths in ordering policy is proposed. The proposed framework detects network congestion in the assigned path and reduces the congestion window. Furthermore, the proposed framework predicts receiver buffer blocking and deactivates the highest delay path that causes this problem. The simulation results show that the proposed framework achieves highest throughput, lower entropy and lower average application end‐to‐end delay than the previous algorithms. [ABSTRACT FROM AUTHOR]

Formation control for a group of autonomous underwater vehicles (AUVs) is challenging due to the complex systems dynamics and time delay in the cooperative feedback loops. This paper introduces a decoupled design procedure, so that formation controllers designed for particle dynamics can be generalised to formation controllers for fully actuated AUVs with six‐degree‐of‐freedom dynamic models for motions in three‐dimensional space. The orientation control and the translation control are first decoupled following a standard inner–outer loop approach. Then, a geometric approach is followed to separate the translation dynamics into formation shape dynamics and formation centre dynamics. Coupling terms between the two portions of the dynamics are treated as perturbations and are tolerated by a robust formation‐keeping controller. The controller is also robust to constant bounded time delays. This decoupling procedure simplified the entire design process comparing with other existing approaches with similar goals. Both rigorous theoretical analysis and simulation results are presented to justify the effectiveness of this method. [ABSTRACT FROM AUTHOR]

In this paper, based on the topological degree theory, Lyapunov functional method and inequality analysis technique, the existence and global exponential stability of equilibrium of impulsive fuzzy Cohen-Grossberg bi-directional associative memory neural networks with delays, are investigated. Moreover, an illustrative example is given to demonstrate the effectiveness of the results obtained. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This study formulates and studies a model of hybrid impulsive and switching dynamical networks with time delays. There are two separable switching functions acting on the network. One drives inherent network structures and the other induces finite‐state feedback in the control law. These hybrid networks have both continuous‐time and discrete‐time dynamics. At each moment, the coupling structure changes from one graph to another. At the same time, the continuous state variables may jump from one value to another. Time delays considered in this paper exist in isolated dynamical nodes, interconnections and impulsive noise disturbances. Based on Lyapunov stability theory, some new sufficient criteria are derived for exponential convergence of disagreement dynamics, which implies that network synchronisation of such hybrid‐delayed network is achieved. An illustrative example of a delayed chaotic network with switching topology and impulse effects is used to demonstrate the main results. [ABSTRACT FROM AUTHOR]

In an interconnected bulk power system, wide‐area measurement system (WAMS) can provide abundant remote measurement for the coordinated control system. However, WAMS data have obvious time delays, which affect the performance of the control system and should be properly considered. Time‐delay stability margin (TDSM) is an index to reflect the maximum delay that a time‐delay system can sustain without losing its stability. To construct a coordinated control system based on WAMS data, it is crucial to accurately and rapidly determine the TDSM value. In this paper, a novel Jordan‐Taylor‐Schur (JTS) approach to determine the TDSM value of power system is proposed. It consists of three, Jordan standardization, Taylor separation and Schur simplification. With the three procedures of this method, the model dimension of time‐delay system can be reduced, and the stability criterion derivation can be rebuilt to omit some unnecessary variables so that both the computational efficiency and accuracy can be boosted. Further, it is worth highlighting that the proposed method can be applied to various Lyapunov‐based stability criteria to improve their efficiency with small errors. Finally, three power systems with time delays have been used to demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Due to the disturbances and varying latency, a teleoperated robotic manipulator might not comply with the master control commands. Although prior studies on minimising the impact of network latency and disturbances on teleoperated robots were conducted, there has been very little research on the prediction of minimal operation regions of robotic arms, especially in the worst‐case scenarios when the disturbances and time delays still prevail even after impact minimisation. This study investigates the problem and proposes a novel solution to predicting minimal operation regions of networked control robotic manipulators. The proposed method can be used to forecast safe operation regions in which the manipulators will certainly enter and exclude regions that the robots will never penetrate. Leveraging on a Lyanonov Krasovskii criterion, the method performs region prediction by establishing minimal reachable bounding sets of the nonlinear, perturbed robotic arm's state vectors guided via a time‐varying delay‐dominant network. Though predominantly nonlinear, the entire prediction process is formulated as a tractable Linear Matrix Inequality (LMI) optimisation problem, which can be solved efficiently and effectively. Efficacy of the proposed method is validated with simulations where a simulated robotic arm is distorted with time‐varying delays and disturbances. [ABSTRACT FROM AUTHOR]

This study addresses the problem of distributed optimization in control of heterogeneous linear multi‐agent systems. Instead of assuming a perfect communication medium as in many existing approaches, two important issues arising from communication networks are considered. First, the existence of communication delays is assumed when each agent receives information from its neighbors. Second, since communication networks are generally unreliable, it is assumed that each agent interacts with other agents through random digraphs. Finally, delay‐dependent sufficient conditions are derived in the form of linear matrix inequalities (LMIs) to prove convergence to optimal solutions. Numerical simulation results are analyzed to demonstrate the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

In this paper, we study the cooperative output regulation problem for the discrete linear time‐delay multi‐agent systems by distributed observer approach. In contrast with the same problem for continuous‐time linear time‐delay multi‐agent systems, the problem has two new features. First, in the presence of time‐delay, the regulator equations for discrete‐time linear systems are different from those for continuous‐time linear systems. Second, under the standard assumption on the connectivity of the communication graph, a distributed observer for any continuous‐time linear leader system always exists. However, this is not the case for the discrete counterpart of the distributed observer for the continuous‐time systems. Another type of discrete distributed observer is proposed. It turns out that such an observer always exists under some mild assumptions. Using this result, the authors further present the solvability conditions of the problem by distributed dynamic output feedback control law. [ABSTRACT FROM AUTHOR]

In this paper, the authors discuss the means for reducing the negative effects of transport delays in digital current controllers. The signal acquisition path introduces delays due to anti‐aliasing pre‐filters and digital signal processing. The voltage actuators in digital current control systems are the pulse‐width modulated (PWM) inverters. They introduce delays caused by the nature of the PWM process and by imperfections in the gating signal chain. A modified digital current controller is devised in this study, enhanced by derivative control action and suited to reduce the effects of transport delays. The controller is aided by a dedicated gain‐setting procedure, suited to secure an improved bandwidth and robustness against the parameter changes. Analytical considerations and experimental results demonstrate the benefits of the devised solutions, which improve disturbance rejection and increase the closed‐loop bandwidth by 1.46 times. The main results are directly applicable to all stationary frame controllers, and also to PR controllers and d–q frame controllers, as they share the same basic control actions. [ABSTRACT FROM AUTHOR]

This study discusses wireless data flow controller design accounting for input signal saturation and an unknown delay. A main focus is to maintain a low real‐time computational complexity. This is motivated by a need to run a very large number of controllers in a single network node, e.g. in wireless 5G data flow control applications. Linear quadratic Gaussian design is therefore first applied to compute feedback and feedforward gains, for assumed nominal delays without accounting for the saturation that is caused by the one‐directional data flow. Gridding of design penalties, system parameters and delays are then used to pre‐compute and tabulate a subset of the ℒ2 stability region by repeated evaluation of the Popov criterion. This step secures a second requirement of robust stability with respect to the uncertain feedback delay. The design is validated with simulation using a detailed model of a networked wireless data flow controller used in cellular communications. [ABSTRACT FROM AUTHOR]

This paper addresses the links between three stabilities (attractivity, asymptotic stability, and exponential stability) of switched homogeneous systems with delays and uncertainties. A system has a certain property over a given set S of switching signals if the property holds for all switching signals in S. It is shown that a switched homogeneous system of degree one is exponentially stable over a given set of switching signals if it is attractive or asymptotically stable over the same set. The result is then applied to switched linear systems with delays and uncertainties. Finally, an example follows to show that ‘being over a given set of switching signals’ is necessary to guarantee the equivalence between different stabilities. [ABSTRACT FROM AUTHOR]

This article studies the stability problems of linear systems with time‐varying delay. An improved negativity condition for a quadratic function parameterised by time‐varying delay is derived. Based on this condition, less conservative stability criteria are obtained. Through two well‐known numerical examples, it is proved that the proposed method can reduce the conservativeness of the computed results. [ABSTRACT FROM AUTHOR]

This study addresses the robust predictive control of a class of discrete‐time switched systems under arbitrary switching signals. The subsystems of the considered switched system involve polytopic uncertainties, the state delay, non‐linear terms, and input constraint. The main goal is to provide two switched delayed state feedback controllers for the cases of known and unknown state delays based on a constrained robust model predictive control method. An appropriate Lyapunov–Krasovskii functional is used to design the controller via an optimisation problem developed as linear matrix inequalities (LMIs). Both approaches are delay dependent because the online LMIs depend on the value of state delay in the first case and the upper bound of the state delay in the second one. The other advantages of the proposed method are considering a non‐constrained switching signal, its ability to handle constraints, and shaping a transient response. Finally, numerical examples are provided to illustrate the effectiveness of the theoretical results and also to compare the results with previous researches. [ABSTRACT FROM AUTHOR]

In this study, the authors derive some new refined Jensen‐based inequalities, which encompass both the Jensen inequality and its most recent improvement based on the Wirtinger integral inequality. The potential capability of this approach is demonstrated through applications to stability analysis of time‐delay systems. More precisely, by using the newly derived inequalities, they establish new stability criteria for two classes of time‐delay systems, namely discrete and distributed constant delays systems and interval time‐varying delay systems. The resulting stability conditions are derived in terms of linear matrix inequalities, which can be efficiently solved by various convex optimisation algorithms. Numerical examples are given to show the effectiveness and least conservativeness of the results obtained in this study. [ABSTRACT FROM AUTHOR]

In this study, the problem of robust stabilisation is considered for a class of uncertain dynamical systems with state delays. Here, it is assumed that the upper bounds of the delayed state perturbations, uncertainties and external disturbances are completely unknown. For such a class of uncertain time‐delay dynamical systems, a novel design method is presented in which a class of continuous memoryless robust stabilising controllers is constructed. In particular, by making use of the presented method, it is not required to introduce some adaptive schemes to update the unknown upper bounds, which makes the control schemes simpler than adaptive robust control schemes reported in the control literature. Moreover, such a control scheme proposed in this study will be called adaptation‐free robust control scheme. It is also shown that the solutions of the resulting closed‐loop time‐delay dynamical systems can be guaranteed to be uniformly ultimately bounded. Finally, the simulations of some numerical examples are provided to demonstrate the validity of the theoretical results. [ABSTRACT FROM AUTHOR]

In this paper, the fault detection problem is studied for a class of non‐linear discrete‐time networked control systems (NCSs). An individual stochastic variable satisfying a certain probabilistic distribution is utilised to describe the data drift of each sensor. The random transmission delays with the upper bound and the data drift phenomena are taken into account in a unified framework. By augmenting the states of the original non‐linear NCS and the constructed full‐order fault detection filter, the resulting fault detection dynamics is converted into an H∞ filtering problem of a non‐linear time‐delay system. A sufficient condition for the existence of the designed fault detection filter is given in terms of a feasible linear matrix inequality, guaranteeing that the fault detection dynamics is stochastically stable and attains the prescribed H∞ attenuation level. Finally, a numerical example is presented to show the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In this study, a new method is put forward for the stability and stabilisation analysis of the event‐triggered load frequency control (LFC) with interval time‐varying delays, considering the global sliding mode controller. To lighten the network bandwidth and save more limited networked resources, the event‐triggered scheme is optimised through quantum genetic algorithm, according to different circumstances. Additionally, global sliding mode control (GSMC) scheme is proposed to provide stronger robustness performance, which against the frequency deviation caused by power unbalance or transmission time delays better. Based on the proposed schemes, multi‐area LFC for the power system model is formulated as a Markov jump linear system model, considering transmission time delays and external disturbances. By applying improved Lyapunov stability theory, criteria about the stability and stabilisation conditions for multi‐area power system can be deduced in terms of linear matrix inequality. Finally, to validate a more realistic LFC application, the proposed event‐triggered GSMC is also deployed on Kundur's two‐area test system. Simulation studies are carried out to illustrate the effectiveness and superiority of the developed schemes. [ABSTRACT FROM AUTHOR]

In this study, a method for fine adjustment of Xilinx field programmable gate array (FPGA) routing delays is proposed and applied to improve the linearity of an unbalanced multi‐measurement time‐to‐digital converter (TDC). The delay control method increases load capacitances of interconnect points of switch matrices by small amounts using additional connections to unused interconnects in the FPGA fabric. The novel delay control method uses the tool command language (TCL) scripting feature available in the Xilinx Vivado tool to automatically add wires into a fully placed and routed design. A total of 61 additional wires were successfully and automatically added to reduce the differential and integral non‐linearities of the target TDC from 0.51 and −0.54 LSB to 0.05 and 0.06 LSB, respectively (reduction factors of 10.2 and 9) for an LSB equal to 333 ps. [ABSTRACT FROM AUTHOR]

This study considers the stability and ℓ∞ ‐gain analysis problem for discrete‐time positive singular systems with unbounded time‐varying delays. By proposing some new techniques and employing mathematical induction method, the authors first derive a sufficient condition to analyse the stability of the system. The authors then investigate the ℓ∞ ‐gain by exploiting the monotonicity of state trajectory. They show that the ℓ∞ ‐gain for the considered systems is independent of the magnitude of delays and fully determined by the system matrices. The validity of the theoretical results is demonstrated by a numerical example. [ABSTRACT FROM AUTHOR]

In this article, we investigate a new way of dealing with fault detection and isolation (FDI) for a class of delayed non‐linear systems with an event‐triggered mechanism (ETM). This article is based on 1) To estimate the dynamics of the nonlinear plant, Sliding Mode Observers (SMO's) is manipulated with Luenberger. 2) Under the ETM, sampled data is released only when the plant's measurement (sampled) violate the specific threshold of the event condition. 3) First, transform into two subsystems. In subsystem‐A contains uncertainties without sensor fault and vice‐versa in subsystem‐B. To handle the uncertainties that appeared in subsystem‐A, a new SMO's implemented while traditional Luenberger is employed to detect the sensor fault. Then, by using a new Lyapunov‐Krasovskii function approach performance index is proposed. Based on stability criteria, sufficient conditions are provided in the account of Linear Matrix Inequalities (LMIs). The simulation example is given to demonstrate the effectiveness of our design method. [ABSTRACT FROM AUTHOR]

This study tackles the problems of exponential stability analysis and model reduction for spatially interconnected discrete‐time systems with time‐varying delay. The well‐posedness, exponential stability, and contractiveness of spatially interconnected discrete‐time systems subject to time‐varying delay are defined and a sufficient condition in terms of linear matrix inequality (LMI) is put forth to test these properties. By exploiting the above analysis result, a sufficient condition for guaranteeing the existence of a reduced‐order system is derived. With the help of Finsler lemma, a reduced‐order system is derived based on the LMI method. By taking advantage of the same method, a delay‐free reduced‐order system for a given spatially interconnected discrete time‐varying delay system can also be attained. Finally, two examples have been carried out to show the feasibility and validity of the derived theories. [ABSTRACT FROM AUTHOR]

In this study, by means of the techniques of adaptive multi‐dimensional Taylor network (MTN) control, the tracking problem of a class of stochastic non‐linear systems with input delay is studied. Firstly, based on the Padé approximation method, a new variable is employed to overcome the problem of input delay, and MTNs are applied to estimate the non‐linear functions in the design of the controller. Secondly, an adaptive MTN controller design scheme is developed in the framework of backstepping. Thirdly, the stability of the closed‐loop system is analysed using Lyapunov's stability theory. Finally, the effectiveness of the proposed design approach is demonstrated by two examples. [ABSTRACT FROM AUTHOR]

This study proposes a modified internal model control (IMC) structure in which an additional controller is added to the standard IMC structure to improve the closed‐loop system bandwidth. The resulting structure is evaluated to satisfy standard IMC objectives of nominal performance and robust stability. The novelty of the work is to design a fractional order (FO) filter in the IMC structure so that gain margin (Am) and phase margin (ϕm) specifications could be independently satisfied for a first‐order plus time delay (FOPTD) process control plant. The proposed modified IMC (m‐IMC) is simulated for three different FOPTD systems to validate and substantiate the theoretical analysis. The proposed m‐IMC is compared with different integer order as well as FO controllers. The transient performance are compared in terms of rise time (Tr), settling time (Ts), maximum overshoot (% Mp) and the effectiveness is measured in terms of integral square error. To validate the viability of the proposed control scheme, it is implemented on a laboratory DC servo‐system. [ABSTRACT FROM AUTHOR]

In this study, the (Q,S,R) ‐ γ ‐dissipativity problem is addressed for Markovian multiple‐weighted coupled neural networks (MWCNNs) with coupling delays by using pinning control and dynamic event‐triggered mechanism. By controlling a small number of nodes in the network combining with dynamic event‐triggered strategy, the system resources can not only be utilised more efficiently but also more conducive to engineering implementation. First, the authors propose a (Q,S,R) ‐ γ ‐dissipativity condition of Markovian MWCNNs. Second, pinning controller and dynamic event‐triggered scheme are both designed based on the derived dissipativity criterion. Furthermore, the elimination of Zeno phenomenon is proofed for the proposed event‐triggered method. Finally, a numerical example is provided to verify the admissibility and effectiveness of the acquired results. [ABSTRACT FROM AUTHOR]