Input Time Delay Research Articles

Observer-based neural adaptive control for a class of MIMO delayed nonlinear systems with input nonlinearities

Abstract An adaptive output-feedback control method is developed for a class of multi-input and multi-output (MIMO) delayed nonlinear systems which are subject to input saturated nonlinearities, modeling uncertainties and time delays. Because state variables are unobtainable, state observers are constructed first. And radial basis function (RBF) neural networks (NNs) are used as approximators to identify the unknown nonlinearities. Adaptive technique is applied to estimate the optimal weight vectors of the approximators. Backstepping method is used to construct the desired controllers. Based on Lyapunov stability theory, the proposed tracking control strategy ensure that all signals in the closed-loop systems are bounded and the target trajectories can be tracked within a enough small error as well. At last, numerical simulations demonstrate the effectiveness of the presented control method.

Computable Delay Margins for Adaptive Systems With State Variables Accessible

Robust adaptive control of plants whose state variables are accessible in the presence of an input time delay is established in this paper. It is shown that a standard model reference adaptive controller modified with projection ensures global boundedness of the overall adaptive system for a range of nonzero delays. The upper bound of such delays, that is, the delay margin, is explicitly defined and can be computed a priori .

EID‐Estimation‐Based Periodic Disturbance Rejection for Sintering Ignition Process with Input Time Delay

AbstractSintering plays a key role in generating blast furnace burden in metallurgical processes. The continuous production and stable quality of sintering significantly depends on the stable and precise control of sintering ignition, which, however, is achieved through an input time delay system, and suffers from different and unknown disturbances. To reject disturbances and enhance the control precision of ignition temperature, this paper introduces a modified equivalent input disturbance (EID)‐based disturbance compensation that is suitable for controlling sintering ignition. First, the periodic properties of disturbances induced by gas pressure fluctuations are obtained based on spectral density decomposition. Second, to obtain the dynamics of sintering ignition, an iterative subspace modeling method is developed, which estimates not only the model parameters but also the length of time delay. By considering the periodic property, a control structure of sintering ignition based on the modified EID‐based compensation is proposed, in which an additional time‐delay element is designed to make the phase difference between EID estimation and real disturbance close to zero. Finally, the validity of the proposed method is verified by a simulation.

Determination of Reactivity and Neutron Flux Using Modified Neural Network for HTGR

Nuclear kinetic calculations based on point kinetic model have been generally applied as the standard method for neutronics codes. As the central control rod (C-CR) withdrawal test has demonstrated in a prismatic core type high-temperature gas-cooled reactor (HTGR) named High Temperature Engineering Test Reactor (HTTR), the transient calculation of kinetic parameter, reactivity, and neutron fluxes, requires a new method to shorten calculation-process time. Development of neural network method was applied to point kinetic model as the necessity of real-time calculation that could work in parallel with the digital reactivity meter. The combination of Time Delayed Neural Network ( TDNN ) and Jordan Recurrent Neural Network ( Jordan RNN ) named TD-Jordan RNN was the result of the modeling approach. The application of TD-Jordan RNN with adequate learning, tested offline, determined results accurately even when signal inputs were noisy. Furthermore, the preprocessing for neural network input utilized noise reduction as one of the equations to transform two of twelve time-delayed inputs into power corrected inputs.

Observer-Based adaptive neural network controller for uncertain nonlinear systems with unknown control directions subject to input time delay and saturation

This paper addresses the design of an observer based adaptive neural controller for a class of strict-feedback nonlinear uncertain systems subject to input delay, saturation and unknown direction. The input delay has been handled using an integral compensator term in the controller design. A neural network observer has been developed to estimate the unmeasured states. In the observer design, the Lipschitz condition has been relaxed. To solve the problem of unknown control directions, the Nussbaum gain function has been applied in the backstepping controller design. “The explosion of complexity” occurred in the traditional backstepping technique has been avoided utilizing the dynamic surface control (DSC) technique and the designed controller is singularity free. It has been shown that all closed-loop signals are semi-globally uniformly ultimately bounded (SGUUB) and the output tracking error converges to a small neighborhood of the origin by choosing the design parameters appropriately. The numerical examples illustrate the effectiveness of the proposed control scheme.

Digital redesign of analog smith predictor for systems with long input time delays

The discretization of the analog Smith predictor by using the prediction-based state-matching digital redesign method for systems with various input time delays was recently investigated in the literature. This paper presents an alternative Chebyshev quadrature state-matching digital redesign method for discretization of the analog Smith predictor for systems with a long input time delay. In order to implement the digitally redesigned Smith predictor by utilizing the output-feedback of the plant, an ideal state reconstructor for the long input-delayed plant is established. The long dead time of interest is an integer plus a fractional input delay. An illustrative example is given to demonstrate the effective of the proposed approach.

Directional Drilling Attitude Control With Input Disturbances and Feedback Delay

This paper presents a general approach for the attitude control of directional drilling tools for the oil and gas industry. It extends the recent work where a kinematic bilinear model of the directional drilling tool was developed and used as the basis for Constant Build Rate (CBR) controller design. The CBR controller in combination with a modified Smith Predictor (SP) is implemented for the attitude control of the directional drilling. The results of a transient simulation of the proposed modified SP-CBR controller are presented and compared with that from the CBR controller of the earlier studies. It is shown that the modified SP-CBR controller significantly reduces the adverse effects of input disturbances and time delay on the feedback measurements with respect to stability and performance.

State Feedback Stabilization of Linear Systems with Unknown Input Time Delay

This paper investigates the control problem of linear systems affected by an unknown constant input delay by means of a finite-dimensional state feedback. The proposed solution extends an approach used in the case of known delays by means of a suitably developed delay identifier. A more general result about the convergence to zero of the controlled system when the delay estimation error only converges to some neighborhood of zero is provided. Numerical examples show the effectiveness of the proposed approach.

Further results on output-feedback stabilization of stochastic upper-triangular systems with state and input time-delays

Based on stochastic time-delay system stability criterion and a homogeneous domination approach, the output-feedback stabilization problem for a class of more general stochastic upper-triangular systems with state and input time-delays has been solved in this paper. Firstly, the initial system is changed into an equivalent one with a designed scalar by introducing a set of coordinate transformations. After that, by designing an implementable homogeneous reduced-order observer, and tactfully selecting a suitable Lyapunov–Krasoviskii functional and a low gain scale, a delay-independent output-feedback controller is explicitly constructed. Finally, the globally asymptotically stability in probability of the closed-loop system is ensured by rigorous proof. The simulation results demonstrate the efficiency of the proposed design scheme.

Design and control of a multi-wing dissipative chaotic system

Considering the dissipative condition, a multi-wing chaotic attractor with a unique perspective is designed, using geometry root locus. By using a nonlinear dissipative term, a new structure is proposed to obtain a dissipative chaotic system with a four-wing attractor. The system properties, namely the phase portraits, bifurcation diagrams, Lyapunov exponents spectrum, Poincare maps and local stability, are investigated by numerical simulations. The phenomenon of multiple attractors is discussed and two double-wing smooth chaotic attractors using two different initial conditions are generated. The nonlinear time-delayed inputs are proposed for chaos control of the new system via bifurcation theory. Based on center manifold and normal form theories, the procedure of determining the direction of the Hopf bifurcation and the stability of the bifurcating periodic solutions are investigated.

Consensus of Fractional-Order Multi-Agent Systems with Input Time Delay

AbstractMany phenomena in inter-disciplinary fields can be explained naturally by coordinated behavior of agents with fractional-order dynamics. Under the assumption that the interconnection topology of all agents has a spanning tree, the consensuses of linear and nonlinear fractional-order multi-agent systems with input time delay are studied, respectively. Based on the properties of Mittag-Leffler function, matrix theory, stability theory of fractional-order differential equations, some sufficient conditions on consensus are derived by using the technique of inequality, which shows that the consensus can be achieved for any bounded input time delay. Finally, two numerical examples are given to illustrate the effectiveness of the theoretical results.

Predictor-Based Control of Systems With State Multiplicative Noise

Linear, continuous-time systems with state-multiplicative noise and time-delayed input are considered. The problems of \(H_{\infty }\) state-feedback and output-feedback control are solved for these systems when uncertainty in their deterministic parameters is encountered. Cascaded sub-predictors of the Luenberger-type are applied that considerably increase the size of the input time delay that can be solved for. Two examples are given. The first is a practical control engineering design and the second is an illustrative example that compares several solution methods for the stochastic state-feedback control.

Robust output regulation problem for discrete-time linear systems with both input and communication delays

Recently, the robust output regulation problem for continuous-time linear systems with both input and communication time-delays was studied. This paper will further present the results on the robust output regulation problem for discrete-time linear systems with input and communication delays. The motivation of this paper comes from two aspects. First, it is known that the solvability of the output regulation problem for linear systems is dictated by two matrix equations. While, for delay-free systems, these two matrix equations are same for both continuous-time systems and discrete-time systems, they are different for continuous-time time-delay systems and discrete-time time-delay systems. Second, the stabilization methods for continuous-time timedelay systems and discrete-time time-delay systems are also somehow different. Thus, an independent treatment of the robust output regulation problem for discrete-time time-delay systems will be useful and necessary.

Heterogeneous and Competitive Multiagent Networks: Couple-Group Consensus with Communication or Input Time Delays

This paper discusses the couple-group consensus problems for a class of heterogeneous multiagent networks including the following two cases: with communication and input time delays, respectively. Different from the related cooperative networks, two novel delayed group consensus protocols are designed based on the competitive relationship between the agents. Furthermore, we absolutely relax the in-degree balance and other restrictive preconditions which existed in the relevant works. Some sufficient algebraic criteria for the achievement of couple-group consensus and the upper bound of the input time delays are technically obtained via the frequency domain method and matrix theory, respectively. The results show that the achievement of the couple-group consensus depends on the second-order agents’ in-degree and the control parameters of the systems, whereas it is independent of the communication time delays. Meanwhile, the upper bound of the input time delay is determined by the control parameters and the in-degree of the first-order agents. Finally, the validity of the proposed results is verified by several simulated examples.

Delay Robustness and Compensation in L1 Adaptive Control

Stability analysis of an L1 adaptive control design decomposes into i) the derivation of an inequality condition imposed on a filter in the control channel that guarantees transient performance bounds on the state and control input for a theoretical nonadaptive reference system, and ii) a Lyapunov-type proof of the decay of a predictor error as the inverse square root of the adaptive gain, which in turn can be made arbitrarily large without sacrificing robustness to time delay in the control input. This paper reviewsrecent results on the robustness to input and communication time delays for L1 control systems with uncertain nonlinearities and in nontrivial network configurations, as well as a possible scheme for compensating for large, constant input delays.

Consensus Control for a Multiagent System with Time Delays

In this paper, we consider the consensus control problem for a multiagent system (MAS) consisting of integrator dynamics with input and output time delays. First, we investigate a consensus condition for the MAS with a linear controller and without any delay compensation. We then propose a consensus controller with a state predictor to compensate the effect of time delay. The consensus condition for this controller is derived and investigated. Finally, we present an example of solving the consensus control problem for two-wheel mobile robots with feedback loops that pass through a computer network with time delays. To demonstrate the validity of the predictor-based controller, we conduct experiments with two-wheel mobile robots and present the results.

ADRC based control for a class of input time delay systems

ADRC based control for a class of input time delay systems

An almost periodic malaria transmission model with time-delayed input of vector

An almost periodic malaria transmission model with the time-delayed input of vector is considered. It is shown that the disease is uniformly persistent when the basic reproduction ratio $R_{0}>1$, and it will die out when $R_{0}

Predictor-based stabilization for chained form systems with input time delay

Abstract This note addresses the stabilization problem of nonlinear chained-form systems with input time delay. We first employ the so-called σ-process transformation that renders the feedback system under a linear form. We introduce a particular transformation to convert the original system into a delay-free system. Finally, we apply a state feedback control, which guarantees a quasi-exponential stabilization to all the system states, which in turn converge exponentially to zero. Then we employ the so-called -type control to achieve a quasi-exponential stabilization of the subsequent system. A simulation example illustrated on the model of a wheeled mobile robot is provided to demonstrate the effectiveness of the proposed approach.

Resilient and Robust Control of Time-Delay Wind Energy Conversion Systems

Wind energy is the fastest growing and the most promising renewable energy resource. High efficiency and reliability are required for wind energy conversion systems (WECSs) to be competitive within the energy market. Difficulties in achieving the maximum level of efficiency in power extraction from the available wind energy resources warrant the collective attention of control and power system engineers. A strong movement toward sustainable energy resources and advances in control system methodologies make previously unattainable levels of efficiency possible. In this paper, we design a general resilient and robust control framework for a time-delay variable speed permanent magnet synchronous generator (PMSG)-based WECS. A linear matrix inequality-based control approach is developed to accommodate the unstructured model uncertainties, L2 type of external disturbances, and time delays in input and state feedback variables. Computer simulation results have shown the efficacy of the proposed approach of achieving asymptotic stability and H∞ performance objectives.