Xiefu Jiang

Stability criteria for linear discrete-time systems with interval-like time-varying delay

This paper is concerned with the stability problem for a class of uncertain linear discrete-time systems with time-varying delay. The delay is of an interval-like type, which means that both lower and upper bounds for the time-varying delay are available. The uncertainty under consideration is norm-bounded uncertainty. Based on Lyapunov-Krasovskii functional approach, delay-dependent stability criteria are obtained using a sum inequality which is first introduced and plays an important role in deriving stability conditions. The criteria are formulated in the form of linear matrix inequalities (LMIs). A numerical example is given to show the effectiveness of the proposed criteria.

On Designing Fuzzy Controllers for a Class of Nonlinear Networked Control Systems

This paper is concerned with controller design for a class of nonlinear networked control systems. These systems are approximated by uncertain linear networked Takagi-Sugeno (T-S) models with both network-induced delay and data packet dropout. Sufficient conditions are derived for the existence of a fuzzy controllers. Then, an iterative algorithm for the controller design is proposed. A control problem of a flexible-joint robot arm system is studied to show the effectiveness of the iterative algorithm.

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

Abstract 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.

Observer-based fuzzy control design with adaptation to delay parameter for time-delay systems

This paper is concerned with the problem of observer-based fuzzy stabilization for time-delay systems. The time-delay under consideration is assumed to be a constant time-delay, but not known exactly. A new design method is proposed for an observer-based fuzzy controller with adaptation to the time-delay. The designed controller simultaneously contains both the current and past state information of the systems and can be derived by solving a set of linear matrix inequalities (LMIs). The existence of the controller is equivalent to that of a controller for time-delay systems where the constant time-delay is known exactly. A numerical example is given to illustrate the effectiveness of the design method.

An improved stability criterion of networked control systems

The stability criterion of networked control systems with both the network-induced delays and data packet dropouts is investigated. A Lyapunov-Krasovskii functional candidate, which makes use of the information of the lower, upper bounds and the middle point of the time-varying network-induced delay interval simultaneously, is proposed and a tighter bounding for an integral term of the delay is estimated to drive a less conservative stability condition for networked control systems. No redundant matrix variable is introduced. Finally, two numerical examples are given to show the effectiveness of the proposed stability criterion.

Robust H ∞ control for uncertain Takagi-Sugeno fuzzy systems with interval time-varying delay

This paper is concerned with the problem of delay-dependent robust H/sub /spl infin// control for uncertain time-delay fuzzy systems with norm-bounded uncertainty. The time-delay is assumed to be a time-varying continuous function belonging to a given interval, which means that the lower and upper bounds for the delay are available. No restriction on the derivative of the time-varying delay is needed, which allows the time-delay to be a fast time-varying function. The state-space Takagi-Sugeno (T-S) uncertain fuzzy model with interval time-varying delay is adopted. Delay-dependent conditions for the existence of robust H/sub /spl infin// controller are presented in the form of linear matrix inequalities (LMIs). A numerical example is given to demonstrate the effectiveness of the proposed method.

Local Adjustment and Global Adaptation of Control Periods for QoC Management of Control Systems

Linking real-time schedulability directly to the quality of control (QoC), the ultimate goal of a control system, a hierarchical feedback QoC management framework with the fixed priority (FP) and the earliest-deadline-first (EDF) policies as plug-ins is proposed in this brief for real-time control systems with multiple control tasks. It uses a task decomposition model for continuous QoC evaluation even in overload conditions and then employs heuristic rules to adjust the period of each of the control tasks for QoC improvement. If the total requested workload exceeds the desired value, global adaptation of control periods is triggered for workload maintenance. A sufficient stability condition is derived for a class of control systems with delay and period switching of the heuristic rules. Examples are given to demonstrate the proposed approach.

Distributed fault detection for sensor networks with Markovian sensing topology

This paper deals with the problem of distributed fault detection for discrete-time sensor networks subject to randomly switching sensing topology. The system dynamics and sensing topology are modeled by a discrete-time Markov chain with incomplete transition probabilities. Each sensor node can effectively communicate with certain neighboring sensors, and randomly switch among finite sensing modes via the Markovian switching rules. The process or the time at which the sensing topology changes does not need to be known a priori. The Kronecker product is adopted to realize the decoupling between the specifical sensor node and its underlying neighboring nodes. By means of the Lyapunov functional approach and an improved free weighting matrix technique, stochastic analysis and design results on distributed fault detection, in terms of a set of linear matrix inequalities (LMIs), are then presented in the simultaneous presence of incomplete transition probabilities, randomly switching sensing topology, uncertain network-induced delays and accumulated data packed dropouts. A simulation example is finally provided to illustrate the effectiveness of the developed theoretical results.

Distributed H ∞ consensus filtering of stochastic systems with markovian coupling intercommunication delays

This paper deals with the problem of distributed H∞ consensus filtering for a continuous-time Itô-type stochastic system with Wiener process disturbances and Markovian coupling intercommunication delays. The problem is solved based on distributed H∞ filters in combination with consensus strategies. The set of filter nodes form a communication network whose topology is modeled by a directed graph that describes estimates exchanged among neighboring nodes. A refined technique is provided to tackle the complicated coupling of the exchanged estimates in the presence of random coupling intercommunication delays. Moreover, a sufficient condition on the existence of desired distributed H∞ consensus-based filters is established such that the resultant filter error system is mean square exponentially stable with a weighting H∞ consensus performance index. The filter design problem is posed in terms of linear matrix inequalities. Finally an illustrative example is given to show the effectiveness of the proposed filter design method.

Controller Design for Networked Fuzzy Systems

This paper deals with the problem of network-based controller design for the given T-S fuzzy model. The effects of both network-induced delays which are assumed to be interval time-varying, and data packet dropout was investigated. Based on an integral inequality and a matrix inequality, a delay-dependent sufficient condition for the existence of a network-based controller is formulated in terms of a linear matrix inequality by adjusting two parameter matrices. And no model transformation is employed. Moreover, in order to obtain a less conservative design method of the network-based controller by solving the obtained nonlinear matrix inequalities and to avoid adjusting any parameter matrix, a novel iterative algorithm is proposed. An illustrative numerical example is also given to show the effectiveness of the proposed design method