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Time-delay systems
This book comprehensively presents a recently developed novel methodology for analysis and control of time-delay systems. Time-delays frequently occurs in engineering and science. Such time-delays can cause problems (e.g. instability) and limit the achievable performance of control systems.
eBook
Quantized neural adaptive finite-time preassigned performance control for interconnected nonlinear systems
In this article, the issue of neural adaptive decentralized finite-time prescribed performance (FTPP) control is investigated for interconnected nonlinear time-delay systems. First, to bypass the potential singularity difficulties, the hyperbolic tangent function and the radial basis function neural networks are integrated to handle the unknown nonlinear items. Then, an adaptive FTPP control strategy is developed, where an improved fractional-order filter is applied to tackle the tremendous “amount of calculation” and eliminate the filter error simultaneously. Furthermore, by considering the impact of bandwidth limitation, an adaptive self-triggered control law is designed, in which the next trigger instant is determined through the current information. Ultimately, it can be demonstrated that the proposed control scheme not only guarantees that all states of the closed-loop system are semi-globally uniformly ultimately bounded, but also that the system output is confined to a small area in finite time. Two simulation examples are carried out to verify the effectiveness and superiority of the proposed method.
Journal Article
Fully actuated system approaches for continuous-time delay systems: part 2. Systems with input delays
In this paper, the fully actuated system (FAS) approaches for continuous-time systems with time-varying state delays and a constant input delay are presented. Two types of continuous-time high-order FASs are proposed: single-order FASs with both state and input delays and multi-order FASs with both state and input delays. Controllers for both types of time-delay FASs are designed based on the full-actuation features of the systems. Unlike the case of FASs with state delays only, a prediction scheme is required and constructed for both types of FASs with input delays. Similar to the case of FASs with state delays only, constant linear closed-loop systems with arbitrarily assignable eigenstructures are also developed. Illustrative examples are provided to demonstrate the effect of the proposed theories.
Journal Article
Color image encryption algorithm based on Mackey–Glass time-delay chaotic system and quantum random walk
To ensure the confidentiality and integrity of image data and prevent unauthorized data tampering and privacy leaks. This study proposes a new color image encryption scheme based on the Mackey–Glass time-delay chaotic system and quantum random walk. This approach fully leverages the unpredictability of quantum random walks to generate random values. It combines the differences in Hamming distance between the three RGB channels of color images to create a highly complex and random key. The overall image and the three independent RGB channels are arranged in ascending order using Logistic-tent chaotic mapping and the Mackey–Glass time-delay chaotic system to obfuscate the image data. The deformed fractional-order Lorenz chaotic system is introduced, integrated with DNA encoding and decoding technology, and XOR operations are performed to achieve encryption at the spatial and pixel levels, thereby increasing the complexity of decryption. Through extensive experimental research, this solution has demonstrated excellent results in tests such as adjacent pixel correlation, information entropy, and key sensitivity. It has an excellent ability to protect the privacy of images and provides a reliable guarantee for the security of image data.
Journal Article
Autapse-induced firing patterns transitions in the Morris–Lecar neuron model
In 1948, Hodgkin identified three firing patterns of a single neuron in response to increasing the external DC input. In this work, we investigated the responses of a single neuron with an autapse based on a modified Morris–Lecar neuron model, which can exhibit the three types of firing patterns by changing only one parameter. An excitatory autapse was found to enhance the firing frequency, but an inhibitory autapse suppressed neuron firing. With excitatory autaptic feedback, the firing of a Class-1 neuron could be switched to that of a Class-2 neuron, and a Class-3 neuron could exhibit a Class-2 firing pattern. The sustained response frequency of the Class-2 neuron transferred from that of Class-3 is only dependent on the autaptic time delay, and the frequency decays gradually with increased the delay time.
Journal Article
Fully actuated system approaches for continuous-time delay systems: part 1. Systems with state delays only
In this paper, the fully actuated system (FAS) approaches for continuous-time systems with time-varying state delays are proposed. Two types of continuous-time high-order FAS models with time delays: single-order time-delay FAS models and multi-order time-delay FASs, are proposed. Particularly, the type of sub-FASs that do not completely but partially satisfy the full actuation is investigated, and the sets of feasible points are defined. When the system states are constrained to the feasible set, a controller can be easily constructed for the sub-FAS such that the closed-loop system is a constant linear system with an arbitrarily assignable eigenstructure. In addition, it is demonstrated that the feasibility constraint can be transformed into a constraint on the initial values of the system, which vanishes when the system is a (global) FAS. Based on the unique control characteristic of the type of FAS models, the concepts of controllability and stabilizability of general dynamical time-delay systems are also proposed. The effect of the proposed theories is illustrated with examples.
Journal Article
Discrete-time delay systems: part 1. Global fully actuated case
A basic introduction to the fully actuated system (FAS) approaches for discrete-time systems with delays is given. Firstly, general dynamical discrete-time FAS models with time-varying state delays and constant input delays are proposed. The FAS models are classified into affine ones and non-affine ones, and also ones with and without interconnections. Secondly, controllers for such FASs are designed, which result in constant linear closed-loop systems with arbitrarily assignable eigenstructure. Different from the case of FAS with state delays only, the controller for a discrete-time FAS with an input delay involves a prediction scheme which is constructed based on the open-loop system. The contribution of this paper has laid a fundamental basis for FAS approaches to discrete-time delay systems, and further specific analysis and design problems can be established similar to the continuous-time system case.
Journal Article
On the Stability Analysis of Systems of Neutral Delay Differential Equations
This paper focuses on the stability analysis of systems modeled as neutral delay differential equations (NDDEs). These systems include delays in both the state variables and their time derivatives. The proposed approach consists of a descriptor model transformation that constructs an equivalent set of delay differential algebraic equations (DDAEs) of the original NDDEs. We first rigorously prove the equivalency between the original set of NDDEs and the transformed set of DDAEs. Then, the effect on stability analysis is evaluated numerically through a delay-independent stability criterion and the Chebyshev discretization of the characteristic equations.
Journal Article
Optimal Control Computation for Nonlinear Fractional Time-Delay Systems with State Inequality Constraints
In this paper, a numerical method is developed for solving a class of delay fractional optimal control problems involving nonlinear time-delay systems and subject to state inequality constraints. The fractional derivatives in this class of problems are described in the sense of Caputo, and they can be of different orders. First, we propose a numerical integration scheme for the fractional time-delay system and prove that the convergence rate of the numerical solution to the exact one is of second order based on Taylor expansion and linear interpolation. This gives rise to a discrete-time optimal control problem. Then, we derive the gradient formulas of the cost and constraint functions with respect to the decision variables and present a gradient computation procedure. On this basis, a gradient-based optimization algorithm is developed to solve the resulting discrete-time optimal control problem. Finally, several example problems are solved to demonstrate the effectiveness of the developed solution approach.
Journal Article