Interval Time-varying State Delay Research Articles

Robust local stabilization of discrete time-varying delayed state systems under saturating actuators

This paper deals with discrete time-varying systems with state-delayed and saturating actuators. A robust state feedback control gain is designed through convex methods ensuring the local stability of the time-varying system with interval time-varying state delay. The estimate of the set of admissible initial conditions is characterized by three convex sets allowing less conservative estimates. Through two numerical examples, we compare our approach with others in the literature and illustrate the better behavior of the proposed methods.

ISS Stabilization of Discrete-time LPV Systems with Interval Time-varying State Delay and Saturating Actuators

Abstract We address the problem of input-to-state stabilization of linear parameter-varying (LPV) discrete-time systems with delayed state and subject to saturated actuators and to l2-limited disturbance. It is assumed that the time-varying delay belongs to a known interval and its maximum variation between two consecutive instants has limited rate. We propose convex delay-dependent conditions for the synthesis of LPV state feedback controllers that do not require the real-time knowledge of the delay and ensure the local input-to-state stability of the closed-loop system for a set of initial conditions and subject to energy bounded disturbance input signals. The approach is based on rewriting the delayed system as a switched uncertain augmented delay-free system with a dead-zone non-linearity and on the application of the generalized sector condition to deal with the saturating actuators. To illustrate the efficiency of our approach, we present a numerical example.

Functional observer design for retarded system with interval time-varying delays

ABSTRACTFunctional observers are the key solution to numerous practical estimation problems, wherein full-order observers cannot be applied. This paper studies the novel problem of minimum-order functional observer design for time-delay systems with interval time-varying state delays. Moreover, unlike the majority of the existing papers on this topic, which consider either small or unknown delay rates, the delay derivative is assumed to possess an upper bound not limited to be less than one. A new augmented Lyapunov–Krasovskii functional with triple integral terms is employed to derive less conservative delay-dependent sufficient conditions for the stability of the closed-loop observer dynamics, which are expressed in terms of linear matrix inequalities. In addition, contemporary techniques such as Wirtinger-based single- and double-integral inequalities, delay splitting scheme, reciprocally convex approach and convex combination technique, along with the descriptor transformation, are adopted in constructing the new stability criterion that is exploited for obtaining the observer parameters. A genetic-algorithm-based searching schema is proposed to optimally tune a number of weighting parameters in the observer design procedure. Numerical examples and simulation results are demonstrated to confirm the effectiveness and the superiority of the proposed observer design algorithm.

Robust Nonfragile Stabilizing Controller for an Uncertain Stochastic Nonlinear System With Interval Time-Varying State-Delays: Prescribed H∞ Performance Level

In this technical brief, delay-dependent nonfragile H∞ control problem of a class of stochastic nonlinear systems with interval time-varying state-delays has been considered using Lyapunov–Krasovskii (LK) functional approach. By exploiting a candidate LK functional and using free-weighting matrix technique, a less conservative delay-dependent stabilization criterion is presented for the existence of a nonfragile memoryless state-feedback controller, which ensures stochastic stability as well as a prescribed H∞ performance level of the closed-loop system in the presence admissible parametric uncertainties in the system as well as in the controller gains and exogenous input signal. Since the resulting stabilization criterion is in terms of nonlinear matrix inequalities (NLMIs), it is solved using cone complementarity algorithm (CCA) to obtain a stabilizing controller. A numerical example is presented to illustrate the effectiveness of the proposed result.

Delay-dependent robust observer-based control for discrete-time uncertain singular systems with interval time-varying state delay

The problem of observer-based robust control design is studied for discrete-time singular systems with norm-bounded uncertainties and a time-varying delay. More precisely, a delay-dependent criterion is established that guarantees the admissibility of the considered systems, without resorting to its decomposition. Based on the proposed criterion and without the assumption that the considered systems are admissible, robust observer-based controllers are designed for discrete-time singular time-delay systems such that the closed-loop systems have the characteristics of regularity, causality and asymptotic stability. Seeking computational convenience, all the developed results are cast in the format of strict linear matrix inequalities (LMIs). Finally, some numerical examples are presented to show the feasibility of the proposed approach.

Sampled-data H∞ filtering of Takagi–Sugeno fuzzy systems with interval time-varying delays

The sampled-data H∞ filtering for a continuous-time Takagi–Sugeno fuzzy system with an interval time-varying state delay is investigated, where the measurement outputs from the plant to the filter are assumed to be sampled at discrete instants with a variable period. Firstly, by means of a newly proposed inequality bounding technique and a new Lyapunov–Krasovskii functional, the fuzzy sampled-data H∞ filtering performance analysis is carried out such that the resultant filter error system is asymptotically stable with a prescribed H∞ attenuation performance index. Secondly, sufficient conditions on the existence of fuzzy sampled-data H∞ filters are derived in the simultaneous presence of the time-varying state delay and the variable sampling period. The proposed bounding inequality lies in its more tightness and alleviates the enlargement of some inverse “coefficients” resulting from the utilization of the well-known Jensen integral inequality. Compared with some existing Lyapunov–Krasovskii functionals, more information about the relationship among the current state and its delayed state is considered. The upper bound of the derivative of the time-varying state delay is not required to be less than one. Different from some existing results in the literature, by applying the proposed results, each different value of such an upper bound (greater than one) leads to a different H∞ disturbance attenuation level. Finally, a numerical example and a modified continuous stirred tank reactor system are given to show the effectiveness of the proposed results.

A novel approach to delay-fractional-dependent stability criterion for linear systems with interval delay

This paper considers the problem of delay-fractional-dependent stability analysis of linear systems with interval time-varying state delay. By developing a delay variable decomposition approach, both the information of the variable dividing subinterval delay, and the information of the lower and upper bound of delay can be taken into full consideration. Then a new delay-fractional-dependent stability criterion is derived without involving any direct approximation in the time-derivative of the Lyapunov–Krasovskii (LK) functional via some suitable Jensen integral inequalities and convex combination technique. The merits of the proposed result lie in less conservatism, which are realized by choosing different Lyapunov matrices in the variable delay subintervals and estimating the upper bound of some cross term in LK functional more exactly. At last, two well-known numerical examples are employed to show the effectiveness and less conservatism of the proposed method.

Relaxed inequality approach to robust ℋ∞ stability analysis of discrete-time systems with time-varying delay

This study aims at deriving a less conservative delay-dependent criterion for the robust H ∞ stability analysis of discrete-time systems with interval time-varying state delay. To this end, an appropriate Lyapunov-Krasovskii functional containing triple summation terms is established and a relaxed inequality approach is proposed to address the induced double summation inequality and to exploits novel relaxation variables for null sum terms. Three numerical examples are provided to illustrate the effectiveness of the derived stability criteria.

Robust [formula omitted] control for T–S fuzzy systems with probabilistic interval time varying delay

In this paper, we are concerned with the problem of robust H∞ control for the Takagi–Sugeno (T–S) fuzzy system with probabilistic interval time-varying state delay. Considering the distribution property of time-varying delay, a new stochastic fuzzy model is first proposed. Then, a delay-distribution-dependent H∞ performance analysis result is established for the closed-loop stochastic fuzzy systems via the Lyapunov–Krasovskii functional method and linear matrix inequality (LMI) technique. Based on the derived H∞ performance analysis results, H∞ controller is designed in terms of LMIs. An illustrative example is proposed to show the effectiveness and feasibility of the proposed method.

New Stability Criteria for Linear Systems with Interval Time-varying State Delays

In the present paper, the problem of stability analysis for linear systems with interval time-varying delays is considered. By introducing a new Lyapunov-Krasovskii functional, new stability criteria are derived in terms of linear matrix inequalities (LMIs). Two numerical examples are given to show the superiority of the proposed method.

Improved delay-range-dependent robust stability criteria for a class of Lur’e systems with sector-bounded nonlinearity

In this paper, the problem of delay-dependent stability of a class of uncertain Lur’e systems of neutral type with interval time-varying state delay and sector-bounded nonlinearity has been considered based on Lyapunov–Krasovskii functional approach. By constructing a candidate Lyapunov–Krasovskii (LK) functional, less conservative robust stability criteria are proposed in terms of linear matrix inequalities (LMIs). The reduction in conservatism of the proposed stability criteria over recently reported results is attributed to the candidate LK functional used in the delay-dependent stability analysis, and to the tighter bounding of the time-derivative of the functional without neglecting any useful terms using minimal number of slack matrix variables. The proposed analysis, subsequently, yields a stability condition in convex LMI framework, and is solved non-conservatively at boundary conditions using standard numerical packages. The effectiveness of the proposed stability criterion is demonstrated through standard numerical examples.

Stability analysis and output-feedback stabilisation of discrete-time systems with an interval time-varying state delay

This study focuses on the stability of discrete-time systems with a time-varying state delay and uncertainties in system matrices. New linear matrix inequality conditions are derived for determining bounds of the delay size to ensure the asymptotic stability. There is no need to assume that the system is stable when the delay vanishes. Conservativeness of the conditions is reduced as much as possible by introducing the free-weighting matrices in a novel way, and using the least inequality in the derivation process. Then a new static output-feedback stabilisation method is proposed with the gain matrix as a direct design variable. Compared with the existing results, the proposed methods indeed give larger delay bounds for many cases.