Yongfang Xie

Retrospective analysis of 515 cases of Crohn's disease hospitalization in China: Nationwide study from 1990 to 2003

Background:  The purpose of the present paper was to investigate the status of Crohn’s disease hospitalization in China.

Decentralized Fault Detection System Design For Large-scale Interconnected System

Abstract In this paper, a decentralized fault detection (FD) system design approach is proposed for discrete-time large-scale interconnected systems. Such an FD system consists of two parts for each subsystem: a residual generator and a residual evaluator. The residual generator producing weighted output estimation errors is designed to match a proper reference residual model, such that it is robust against system disturbances and sensitive to system faults. The solution to a (sub)-optimal residual generator is given by solving a convex optimization problem with the help of linear matrix inequalities (LMIs). Then norm based evaluation functions are selected for each subsystem and the corresponding thresholds are presented for the residual evaluator design. The computation of thresholds are formulated also as an optimization problem, which can be solved by using LMIs. Finally, a numerical example is given to illustrate the results.

Intelligent prediction model of matte grade in copper flash smelting process

Due to the importance of detecting the matte grade in the copper flash smelting process, the mechanism model was established according to the multi-phase and multi-component mathematic model. Meanwhile this procedure was a complicated production process with characteristics of large time delay, nonlinearity and so on. A fuzzy neural network model was set up through a great deal of production data. Besides a novel constrained gradient descent algorithm used to update the parameters was put forward to improve the parameters learning efficiency. Ultimately the self-adaptive combination technology was adopted to paralleled integrate two models in order to obtain the prediction model of the matte grade. Industrial data validation shows that the intelligently integrated model is more precise than a single model. It can not only predict the matte grade exactly but also provide optimal control of the copper flash smelting process with potent guidance.

Memory State Feedback Control for Singular Systems with Multiple Internal Incommensurate Constant Point Delays

Abstract In this paper, the problem of delay-dependent stabilization for singular linear continuous-time systems with multiple internal incommensurate constant point delays (SLCS-MIID) is investigated. The condition when a singular system subject to point delays is regular independent of time delays is given and it can be easily tested with numerical or algebraic methods. Based on the Lyapunov-Krasovskii functional approach and the descriptor integral-inequality lemma, a suficient condition for delay-dependent stability is obtained. The main idea is to design multiple memory state feedback control laws such that the resulting closed-loop system is regular independently of time delays, impulse free, and asymptotically stable via solving some strict linear matrix inequalities (LMIs) problem. An explicit expression for the desired memory state feedback control law is also given. Finally, a numerical example illustrates effectiveness and availability for the proposed method.

Delay-dependent Stabilization of Singular Linear Continuous-time Systems with Time-varying State and Input Delays

The descriptor integral-inequality method is a new method to deal with the delay-dependent stabilization problem for singular linear continuous-time systems with time-varying state and input delays. Delay dependent stabilization conditions are established by using the Lyapunov-Krasovskii functional approach combined with an descriptor integral-inequality. An LMI based algorithm to design a memoryless state feedback control that stabilizes the system is provided. Finally, a numerical example is presented to illustrate the effectiveness and the availability for the design.

Decentralized Robust H ∞ Output Feedback Control for Value Bounded Uncertain Large-scale Interconnected Systems

For large-scale interconnected systems with value bounded uncertainties existing in the state, control and interconnected matrices, the design of a decentralized robust Hinfin output feedback controller is investigated. Based on the bounded real lemma sufficient conditions for the existence of a decentralized robust Hinfin controller are obtained in terms of a set of matrix inequalities. According to Schur complement, a homotopy iterative linear matrix inequality method is put forward to construct a decentralized robust Hinfin controller by fixing different variables. The controller obtained enables the closed-loop large-scale systems robust stable and satisfies the given Hinfin performance. At last a numerical example is given to illustrate the effectiveness of the offered method

Time-optimal state feedback stabilization of switched Boolean control networks

This paper investigates the time-optimal state-feedback stabilization of switched Boolean control networks (SBCNs). Based on the properties of the semi-tensor product (STP) of matrices, a technique is proposed to merge the switching signal and all inputs of subnetworks into a single input variable. This technique allows us to transfer a SBCN to an equivalent non-switching logical control network (LCN) and eases the analysis and design process significantly. So long as a state-feedback stabilizer is obtained for the resulting non-switching LCN, it can then be decomposed uniquely into the respective state feedbacks of the sub-networks and the state-dependent switching law. Based on this technique, the controllability and stabilisability of such SBCNs are solved and an algorithm for finding all time-optimal switching state feedbacks is proposed. An example is described to illustrate the main results and the design process proposed in this paper.

Reagent Addition Control for Stibium Rougher Flotation Based on Sensitive Froth Image Features

The reagent addition control level of stibium rougher flotation has a significant impact on the performance of cleaner and scavenger flotation. Currently, due to the complexity of the froth flotation process, the addition rates of reagents, which are controlled by operators, are often not regulated properly in time. Therefore, it is necessary to study a control strategy for the reagent addition rates. This paper proposes a sensitive froth image feature (FIF)-based control strategy that involves an estimator of the feed grade, a preset controller, and a feedback controller. Because the addition rates of reagents should be regulated according to the feed grade, an estimator model for feed grade is built based on the probabilistic support vector regress method. Then, the addition rates of reagents are preset according to the feed grade type based on the operational pattern method. To overcome the steady-state disturbances, a feedback dosage controller is developed to further regulate the reagent addition rates based on the interval type-II fuzzy control system. In the proposed control strategy, the selection of FIF, the inference of feed grade, and the process of uncertainty in sample data are described in detail. Finally, industrial experiments show the effectiveness of the proposed method.

Decoupling Smith Control for Multivariable System with Time Delays

Abstract In order to solve the decoupling control problem of multivariable system with time delays, a new decoupling Smith control method for multivariable system with time delays was proposed. Firstly, the decoupler based on the adjoint matrix of the multivariable system model with time delays was introduced. And the decoupled models were reduced to first-order plus time delay models by analyzing the amplitude-frequency and phase-frequency characteristics. Secondly, according to the closed-loop characteristic equation of Smith predictor structure, PI controllers were designed following the principle of pole assignment for Butterworth filter. Finally, using small-gain theorem and Nyquist stability criterion, sufficient and necessary conditions for robust stability were analyzed with multiplicative uncertainties which encountered frequently in practice. The illustrative example was given to show the superiority of response speed and load disturbance rejection performance.

Delay-dependent stabilization of singular linear time delay systems based on memory state feedback control

In this paper, the delay-dependent stabilization problem for singular linear time-delay systems is studied by designing a delay-dependent memory state feedback controller which makes the singular linear time-delay systems regular, impulse free and asymptotically stable. Firstly, the lemma of descriptor integral-inequality is derived. Secondly, delay dependent stabilization conditions are established by using the Lyapunov-Krasovskii functional approach combined with a descriptor integral-inequality. Thirdly, an LMI based algorithm to design a memory state feedback control that stabilizes the system is provided. Finally, a numerical example is presented to illustrate the effectiveness and the availability for the design.