Conservative Synchronization Research Articles

Virtual Time III, Part 3: Throttling and Message Cancellation

This is Part 3 of a trio of papers that unify in a natural way the two historically distinct parallel discrete event synchronization paradigms, optimistic and conservative, combining the best properties of both into a single framework called Unified Virtual Time (UVT) . In this part we survey the synchronization effects that can be achieved by restricting to corner cases the relationships permitted among the control variables, GVT , CVT , TVT , and LVT , which were defined in Part 1 . We also survey various throttling policies from the literature and describe how they can be implemented in UVT by controlling the value of TVT , including policies that can take advantage of rollback in addition to LP blocking. A significant result is a new category of efficient and higher precision throttling algorithms for optimistic execution that are based on optimistic lookahead , defined in a way that is symmetric to what we now call the conservative lookahead information that is traditionally used for conservative synchronization. Finally, we present a novel algorithm allowing the choice between lazy and aggressive cancellation to be made on a message-by-message basis using either external logic expressed in the model code, or policy code internal to the simulator, or a mixture of both.

Submission to Special Issue to Explainable Representation Learning-Based Intelligent Inspection and Maintenance of Complex Systems: Synchronization of Inertial Neural Networks With Unbounded Delays via Sampled-Data Control.

This article addresses the synchronization issue for inertial neural networks (INNs) with heterogeneous time-varying delays and unbounded distributed delays, in which the state quantization is considered. First, by fully considering the delay and sampling time point information, a modified looped-functional is proposed for the synchronization error system. Compared with the existing Lyapunov-Krasovskii functional (LKF), the proposed functional contains the sawtooth structure term V8(t) and the time-varying terms ex(t-βħ (t)) and ey(t-βħ (t)) . Then, the obtained constraints may be further relaxed. Based on the functional and integral inequality, less conservative synchronization criteria are derived as the basis of controller design. In addition, the required quantized sampled-data controller is proposed by solving a set of linear matrix inequalities. Finally, two numerical examples are given to show the effectiveness and superiority of the proposed scheme in this article.

Mixed-Delay-Based Augmented Functional for Sampled-Data Synchronization of Delayed Neural Networks With Communication Delay.

The synchronization control for delayed neural networks (DNNs) via a sampled-data controller considering communication delay is studied by input delay approach. Although few scholars have put forward the coexistence of transmission delay and communication delay in this problem, no report has clarified the interaction between transmission delay and communication delay. Also, the time-squared terms are underutilized. Thus, a novel augmented Lyapunov functional, which consists of a mixed-delay-based augmented part and a time-squared two-sided looped part, is proposed to fill this gap. In the mixed-delay-based augmented part, not only the information of transmission delay and communication delay themselves, but also the interaction between those two delays is considered. Time-dependent quadratic terms as well as the sampling integral states are introduced in the two-sided looped part, so that more characteristic information of the sampling pattern is encompassed and the relationship of the states at the sampling instant is enhanced. Then, this novel augmented functional is applied to the synchronization control of DNNs. A less conservative synchronization criterion is obtained in the form of linear matrix inequalities. A numerical example illustrates the validity and superiority of the presented synchronization criterion.

On Master-Slave Synchronization of Chaotic Lur’e Systems Using Sampled-Data Control

This brief aims to achieve a less conservative master-slave synchronization criterion for chaotic Lur’e systems using sampled-data control. To this end, a novel piecewise differentiable Lyapunov-Krasovskii functional (LKF) is constructed to fully capture the characteristics about real sampling pattern and nonlinearities of the system. By using the new LKF, a less conservative synchronization criterion is presented to guarantee global exponential stability about synchronization error system. Chua’s circuit system is adopted to verify effectiveness and advantage of obtained approach.

Improvement master–slave robustly synchronous criteria of uncertain chaotic Lur’e systems via an augmented Lyapunov–Krasovskii functional

The robust synchronization of uncertain master–slave Lur’e systems based on time-delayed feedback control is further investigated. A less conservative synchronization stability criterion and a less conservative robust synchronization stability criterion than some recent published references are proposed via Lyapunov stability theory. First, an augmented delay-dependent Lyapunov–Krasovskii functional (LKF) is constructed, where some single integral terms are augmented to the integrand component of a single-integral subfunction. This not only increases some coupling information on some system variables but also increases the coupling information on some necessary variables contained in the inequality lemmas, which can make full use of the inequality lemmas and reduce the conservatism of the synchronization stability criterion. Second, to overcome the nonlinear phenomena in the synchronization criterion, the novel negative definite inequality equivalent transformation lemma is used to transform the nonlinear inequalities to the linear matrix inequalities (LMIs) equivalently, which can be easily solved by the MATLAB LMI-Toolbox. Finally, some common numerical examples are presented to show the effectiveness of the proposed approach.

Real-Time-Shift: Pseudo-Real-Time Event Scheduling for the Split-Protocol-Stack Radio-in-the-Loop Emulation

The incorporation of real radio hardware and physical emulated radio links into higher layer network and protocol simulation studies has been a largely untouched area of research so far. The Split-Protocol-Stack Radio-in-the-Loop emulation combines pure discrete-event protocol simulation with a hardware-based radio link emulation. Since the basic techniques involve contrary time concepts, event communication between the two domains requires a rethink of scheduling and synchronization. With the Real-Time-Shift conservative synchronization and time compensation scheme, the simulator is decoupled from real-time constraints and limitations by introducing predetermined pause times for event execution. In this work, we present the core synchronization and event scheduling approach allowing for scalable pseudo-real-time simulations with radio hardware in the loop. This enables discrete-event simulations for wireless host systems and networks with link-level emulation accuracy, accompanied by an overall high modeling flexibility.

Synchronization of discrete-time fractional fuzzy neural networks with delays via quantized control

In this paper, synchronization issue of discrete-time fractional fuzzy neural networks (DFFNNs) with delays is solved via quantized control, and is applied in image encryption. Firstly, a novel fractional-order h-difference inequality which makes Lyapunov method more flexible and practical is strictly proved based on the properties of convex functions and theory of discrete fractional calculus. Secondly, by using compression mapping theorem and mathematical induction, we obtain two sufficient conditions to ensure the existence and uniqueness of solutions for DFFNNs. Whereafter, we design a suitable quantized controller, which not only saves channel resources but also reduces control costs. By utilizing our inequality and some analytical techniques, several conservative synchronization criteria for DFFNNs are acquired. Finally, two examples are arranged to illustrate the validity and practicability of our results.

Intermittent sampled-data control for exponential synchronization of chaotic delayed neural networks via an interval-dependent functional

This paper focuses on the exponential synchronization of chaotic delayed neural networks (CDNNs) via the intermittent sampled-data control (ISC). To save the control cost and limited bandwidth, an ISC strategy which integrates the merits of the intermittent control (IC) scheme and the sampled-data control (SC) scheme is proposed. With the proposed ISC scheme, an interval-dependent Lyapunov functional (IDLF) is established for the synchronization control systems. The main characteristic of this functional is that it takes full advantage of the available state information of both working intervals and sleeping intervals. Due to the continuity of the proposed functional, some restrictive conditions on Lyapunov matrices are removed. In addition, some less conservative synchronization criteria are established by means of a combination of the Lyapunov stability theory, the reciprocally convex inequality and the Wirtinger inequality. Meanwhile, an algorithm for the ISC gain is effectively designed to realize the synchronization of master and slave CDNNs. Furthermore, a qualitative relationship between the duty ratio (DR) and the system decaying rate is analyzed. In the end, two examples are given to reveal that the proposed results are feasible and reasonable.

Virtual Time III, Part 2: Combining Conservative and Optimistic Synchronization

This is Part 2 of a trio of works intended to provide a unifying framework in which conservative and optimistic synchronization for parallel discrete event simulations can be freely and transparently combined in the same logical process on an event-by-event basis. In this article, we continue the outline of an approach called Unified Virtual Time (UVT) that was introduced in Part 1 , showing in detail via two extended examples how conservative synchronization can be refactored and combined with optimistic synchronization in the UVT framework. We describe UVT versions of both a basic time windowing algorithm called Unified Simple Time Windows and a refactored version of the Chandy-Misra-Bryant Null Message algorithm called Unified CMB .

Virtual Time III, Part 1: Unified Virtual Time Synchronization for Parallel Discrete Event Simulation

Algorithms for synchronization of parallel discrete event simulation have historically been divided between conservative methods that require lookahead but not rollback, and optimistic methods that require rollback but not lookahead. In this paper we present a new approach in the form of a framework called Unified Virtual Time (UVT) that unifies the two approaches, combining the advantages of both within a single synchronization theory. Whenever timely lookahead information is available, a logical process (LP) executes conservatively using an irreversible event handler. When lookahead information is not available the LP does not block, as it would in a classical conservative execution, but instead executes optimistically using a reversible event handler. The switch from conservative to optimistic synchronization and back is decided on an event-by-event basis by the simulator, transparently to the model code. UVT treats conservative synchronization algorithms as optional accelerators for an underlying optimistic synchronization algorithm, enabling the speed of conservative execution whenever it is applicable, but otherwise falling back on the generality of optimistic execution. We describe UVT in a novel way, based on fundamental invariants, monotonicity requirements, and synchronization rules. UVT permits zero-delay messages and pays careful attention to tie-handling using superposition. We prove that under fairly general conditions a UVT simulation always makes progress in virtual time. This is Part 1 of a trio of papers describing the UVT framework for PDES, mixing conservative and optimistic synchronization and integrating throttling control.

An Improved Result on Sampled-Data Synchronization of Markov Jump Delayed Neural Networks

This article deals with the issue of dissipative synchronization for Markov jump neural networks subject to time-varying interval delays by using the sampled-data control method. First, a new two-sided looped-functional is introduced to improve the informativeness of the formed Lyapunov-Krasovskii functional, which takes into an account the information of the entire sampling period. Compared with some traditional methods, the information between x(t) and x(t <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k+1</sub> ) is also emphasized. On this basis, an improved inequality technique is considered valid to acquire the less conservative synchronization criterion. In the end, two numerical examples are displayed, and a comparative example powerfully demonstrates the availability and the superiority of the developed technique.

Sampled-Data Synchronization Control for Chaotic Neural Networks With Mixed Delays: A Discontinuous Lyapunov Functional Approach

The sampled-data synchronization problem of chaotic neural networks with mixed time delays is investigated in this paper. A novel augmented discontinuous Lyapunov-Krasovskii functional (ADLKF) is constructed, which can make full capture the more information of delay variation and the characteristics about the actual sampling information. Based on the ADLKF and modified free-matrix-based integral inequality, novel less conservative synchronization criteria are developed to guarantee that the slave system is synchronous with the master system. Furthermore, the derived results are given in terms of simplified linear matrix inequalities (LMIs), which can be straightforwardly solved by Matlab. Finally, two numerical examples are proposed to demonstrate the effectiveness and the benefits of the presented synchronization scheme.

Distributed Dynamic Self-Triggered Control for Uncertain Complex Networks With Markov Switching Topologies and Random Time-Varying Delay

This paper studies the synchronization of complex networks with probabilistic interval delay and Markov switching topologies by using a novel dynamic self-triggered control (DSTC) scheme. Employing the probability distribution information of the input time-delay, the control protocol is transformed into a new rule with stochastic parameters. Also, a more general case of switching topologies, Markov switching topologies with partial information on transition rate, is discussed. By introducing a free-connection weighting matrix scheme and using the stability theory, a less conservative synchronization result is derived. It is shown by a numerical example that the DSTC method can reduce the sampling frequency apparently, and the tolerable delay upper bound can also be relaxed. In addition, continuous communication and the Zeno-behavior can be avoided.

Drive-response synchronization of uncertain Markov jump generalized neural networks with interval time varying delays via decentralized event-triggered communication scheme

This paper investigates the synchronization problem of uncertain Markov jump generalized neural networks with interval time varying delays using decentralized event-triggered approach. We present a decentralized event-triggered scheme is utilized to decide if the sensor estimations ought to be sent out or not. Every sensor can choose the transmitted sensor estimations locally as indicated by the related event-triggered condition. By constructing an appropriate Lyapunov–Krasovskii functional (LKF) both continuous and discontinuous LKF, handled by the Jensen’s inequality, peng-park’s inequality (PPI) and a new Wirtinger-based integral inequality (WII) technique respectively. A simple and less conservative synchronization criterion is given to ensure the master systems synchronize with the slave systems by using the linear matrix inequality (LMI) approach. The Lyapunov method is employed to derive a sufficient condition such that the error system is stochastically stable. Moreover, the desired controller gains and event-triggered parameters are derived provided that the sufficient condition is satisfied. Finally, numerical examples are included to show that the results obtained from the proposed method provide less conservative results, which support the superiority of our criteria.

Synchronization of Kuramoto Oscillators: A Regional Stability Framework

We develop a novel regional stability analysis framework based on the proposed region-parametrized Lyapunov function to study the synchronization of Kuramoto oscillators. A new synchronization definition is introduced and characterized by frequency boundedness and phase cohesiveness, the latter of which requires phase angles of any two connected nodes rather than any two arbitrary nodes to stay cohesive. This definition allows for time-varying natural frequencies and can lead to less conservative synchronization condition. Applying the analysis framework to Kuramoto oscillators, we derive two algebraic synchronization conditions that relate the underlying network topology and system parameters to the synchronization. Finally, we give estimations of the region of attraction explicitly in terms of phase angles as well as the energy function. They require no calculation for critical equilibrium points compared to traditional methods for power systems. The numerical example shows that two synchronization conditions can complement each other for predicting the synchronization.

Finite-Time Dissipative Synchronization for Markovian Jump Generalized Inertial Neural Networks With Reaction–Diffusion Terms

A novel generalized neural network (NN), which includes Markovian jump parameters, inertial items, and reaction-diffusion terms, is proposed, and the issue of finite-time dissipative synchronization for this kind of NNs is discussed in this article. First, an appropriate variable substitution is employed so that the original second-order differential system is transformed into a first-order one. Second, a novel time-varying memory-based controller is designed to ensure the dissipative synchronization of the drive and response systems over a finite-time interval. Then, a new Lyapunov-Krasovskii function is processed by reciprocally convex combination and free-weighting matrix methods, therefore, a less conservative synchronization criterion is derived. Finally, by providing three examples, the feasibility, superiority, and practicality of the obtained results are illustrated.

Finite-time nonfragile time-varying proportional retarded synchronization for Markovian Inertial Memristive NNs with reaction–diffusion items

The issue of synchronization for a class of inertial memristive neural networks over a finite-time interval is investigated in this paper. Specifically, reaction–diffusion items and Markovian jump parameters are both considered in the system model, meanwhile, a novel nonfragile time-varying proportional retarded control strategy is proposed. First, a befitting variable substitution is invoked to transform the original second-order differential system into a first-order one so that the corresponding synchronization error system that is represented by a first-order differential form is established. Second, by utilizing the integral inequality technique, reciprocally convex combination approach and free-weighting matrix method, a less conservative synchronization criterion in terms of linear matrix inequalities is obtained. Finally, three simulations are exploited to illustrate the feasibility, practicability and superiority of the designed controller so that the acquired theoretical results are supported.

Pinning Event-Triggered Sampling Control for Synchronization of T–S Fuzzy Complex Networks With Partial and Discrete-Time Couplings

This paper focuses on the synchronization problem of Takagi-Sugeno (T-S) fuzzy complex networks with partial and discrete-time couplings via event-triggered sampling control. Different from traditional control methods, a more general and practical event-triggered communication scheme with nonuniform sampling is newly designed for T-S fuzzy complex networks. Then, a Lyapunov-Krasovskii functional (LKF) with a novel input-delay-product-type (IDPT) term is presented. The IDPT term can fully capture the information of the nonlinear functions and the actual sampling pattern. Based on the new IDPT LKF, less conservative synchronization criteria are derived. Meanwhile, by solving a set of linear matrix inequalities, the desired pinning control gains are precisely obtained. Simulation examples are provided to illustrate the effectiveness and superiorities of the proposed results.

A new method for quantized sampled-data synchronization of delayed chaotic Lur’e systems

• The extended Wirtinger-inequality-based Lyapunov approach is newly proposed. • A zero equality is formulated, which can capture the information of system at the dynamic partitioning point. • A quantized sampled-data controller is designed. • Compared with some existing results, less conservative synchronization criteria are established for chaotic Lur’e systems. We design a quantized sampled-data controller for synchronization of delayed chaotic Lur’e systems. A new approach, extended Wirtinger-inequality-based Lyapunov–Krasovskii functional, is firstly proposed. This approach grasps more sampling information by introducing more free matrices in comparison with some existing methods. Using the system information at the dynamic partitioning point, a zero equality is formulated to fully utilize the inner sampling information. Based on the new approach and zero equality, some novel synchronization criteria are established. In the meantime, the desired quantized sampled-data control gain is obtained with larger sampling period than those in the existing works. Finally, two numerical examples illustrate the merits of the method.

Observer-Based Synchronization Control for Coronary Artery Time-Delay Chaotic System

This paper researches observer-based H ∞ synchronization of coronary artery system with input, output time-delays, and external disturbance. By designing chaotic observers for both the master system and slave system, the estimation of the states for master-slave systems has been accomplished. Based on the free-matrix-based integral inequality and Wirtinger-based inequality, the Lyapunov Krasovskii functional (LKF) is constructed to obtain a less conservative synchronization strategy for the chaotic coronary artery system with the existence of state estimation errors and synchronization error. The effectiveness of this control strategy has been demonstrated by some simulations.