Effects of Scale-Free Topological Properties on Dynamical Synchronization and Control in Coupled Map Lattices

In the paper, we study effects of scale-free （SF） topology on dynamical synchronization and control in coupled map lattices （CIVIL）. Our strategy is to apply three feedback control methods, including constant feedback and two types of time-delayed feedback, to a small fraction of network nodes to reach desired synchronous state. Two controlled bifurcation diagrams verses feedback strength are obtained respectively. It is found that the value of critical feedback strength γc for the first time-delayed feedback control is increased linearly as e is increased linearly. The GML with SF loses synchronization and intermittency occurs if γ 〉 γc. Numerical examples are presented to demonstrate all results.

Controller Design for Electric Power Steering System Using T-S Fuzzy Model Approach

Pressure ripples in electric power steering （EPS） systems can be caused by the phase lag between the driver s steering torque and steer angle, the nonlinear frictions, and the disturbances from road and sensor noise especially during high-frequency maneuvers. This paper investigates the use of the robust fuzzy control method for actively reducing pressure ripples for EPS systems. Remarkable progress on steering maneuverability is achieved. The EPS dynamics is described with an eight-order nonlinear state-space model and approximated by a Takagi-Sugeno （T-S） fuzzy model with time-varying delays and external disturbances. A stabilization approach is then presented for nonlinear time-delay systems through fuzzy state feedback controller in parallel distributed compensation （PDC） structure. The closed-loop stability conditions of EPS system with the fuzzy controller are parameterized in terms of the linear matrix inequality （LMI） problem. Simulations and experiments using the proposed robust fuzzy controller and traditional PID controller have been carried out for EPS systems. Both the simulation and experiment results show that the proposed fuzzy controller can reduce the torque ripples and allow us to have a good steering feeling and stable driving.

Fault detection observer design for networked control system with long time-delays and data packet dropout

Focusing on the networked control system with long time-delays and data packet dropout,the problem of observerbased fault detection of the system is studied.According to conditions of data arrival of the controller,the state observers of the system are designed to detect faults when they occur in the system.When the system is normal,the observers system is modeled as an uncertain switched system.Based on the model,stability condition of the whole system is given.When conditions are satisfied,the system is asymptotically stable.When a fault occurs,the observers residual can change rapidly to detect the fault.A numerical example shows the effectiveness of the proposed method.

Application of PID Controller Based on BP Neural Network in Export Steam’s Temperature Control System

By combining the Back-Propagation （BP） neural network with conventional proportional Integral Derivative （PID） controller, a new temperature control strategy of the export steam in supercritical electric power plant is put forward. This scheme can effectively overcome the large time delay, inertia of the export steam and the influencee of object in varying operational parameters. Thus excellent control quality is obtaitud. The present paper describes the development and application of neural network based controller to control the temperature of the boiler＇s export steam. Through simulation in various situations, it validates that the control quality of this control system is apparently superior to the conventional PID control system.

直接序列扩频通信侦察技术实验模型

直接序列扩频通信侦察技术实验模型主研人员：郭伟余敬东洪福明李牧张国平三超时冯天久蒋明该研究成果直接应用于＂直接序列扩频通信对抗系统＂中，为直扩通信对抗装备和直扩通信侦收提供技术支撑，同时本项目成果所突破的关键技术可应用于ＣＤＭＡ通信系统的开发和管理。...

Stability of stochastic switched epidemic systems with discrete or distributed time delay

Stochastic switched epidemic systems with a discrete or distributed time delay are constructed and investigated. By the Lyapunov method and lto＇s differential rule, the existence and uniqueness of global positive solution of each system is proved. And stability conditions of the disease-free equilibrium of the systems are obtained. Numerical simulations are presented to illustrate the results.

Extended parameter-dependent H∞ filtering for uncertain continuous-time state-delayed systems

The design of robust H∞ filtering problem of polytopic uncertain linear time-delay systems is addressed. The uncertain parameters are supposed to reside in a polytope. A parameter-dependent Lyapunov function approach is proposed for the design of filters that ensure a prescribed H∞performance level for al ad-missible uncertain parameters, which is different from the quadratic framework that entails fixed matrices for the entire uncertainty do-main. This idea is realized by careful y selecting the structure of the matrices involved in the products with system matrices. An extended H∞ sufficient condition for the existence of robust esti-mators is formulated in terms of linear matrix inequalities, which can be solved via efficient interior-point algorithms.

Audible Threshold of Early Reflections with Different Orientations and Delays

Early reflection is an important component in an enclosedsound field. Due to the precedence effect, the early reflection maynot be the dominant factor in sound source localization;however,it still has obvious influences on spatial position, loudness, timbre,and etc. Till now, there have sparse studies on evaluation of theaudible threshold of early reflections with lacking of general andquantitative results. This work investigated the audible thresholdof early reflection with a simplified sound field model undervarious experimental conditions including the combination ofeight incidence angles and five time delays. Three-down-one-upadaptive strategy with three-interval three-alternativeforced-choice (3I-3AFC) paradigm was used due to its efficiencyand robustness. Results indicate that (1) the audible threshold ofearly reflections decreases monotonically with increasing timedelay relative to the direct sound. Furthermore, a linear equationbetween early reflection threshold and time delay is establishedwith correlation coefficient higher than 0.9;(2) When the directsound and the reflection locate in the same half-plane, the audiblethreshold of early reflections decreases with increasing angledeviation between the direct sound and the reflection. Moreover,a front-back symmetry of early reflection threshold is observedfor stimuli below 5 kHz;(3) Considerable variations in earlyreflection threshold are found among individuals, especially atlarge angle deviation and time delay of early reflections relativeto the direct sound.

On Stabilizing Sets of PI Controllers for Multiple Time Delayed Process

This paper considers the problem of stabilizing multiple time delayed processes using proportional integral(PI) controller.The presented approach is based on finding all possible values of control parameters which will result in pure imaginary roots of closed loop characteristic equation under all process parameters fixed.The ergodic search of three PI control parameters are converted from the range of infinity to finite range by introducing trigonometric tangent function.After all possible stability boundaries are obtained,the Nyquist stability method is used to determine the actual stability region of the controller parameters.This method also permits design for simultaneous minimum gain and phase margin requirement.An illustrative example case is also presented.

A Robust Fault Detection and Isolation Scheme Based on Unknown Input Observers for Discrete Time-delay System with Disturbance

This paper proposes a robust fault detection and isolation (FDI) scheme for discrete time-delay system with disturbance. The FDI scheme can not only detect but also isolate the faults. The lifting method is exploited to transform the discrete time-delay system into the non-time-delay form. A generalized structured residual set is designed based on the unknown input observer (UIO). For each residual generator, one of the system input signals together with the corresponding actuator fault and the disturbance signals are treated as an unknown input term. The residual signals can not only be robust against the disturbance, but also be of the capacity to isolate the actuator faults. The proposed method has been verified by a numerical example.

Sufficient Conditions for Robust Stability of Discrete Large-Scale Interval Systems with Multiple Time Delays

The robust stability analysis for discrete large-scale uncertain systems with multiple time delays is addressed in this paper. We establish a method for selecting properly a positive definite matrix Q to derive a very simple upper solution bound of the discrete algebraic Lyapunov equation (DALE). Then, using the Lyapunov equation approach method with this upper bound, several sufficient conditions are presented to guarantee the robust stability of the overall systems. Comparisons between the proposed results with a previous one are also given.

EFFECT OF KAIROMONE ON PREDATOR-PREY DYNAMICS -- A DELAY MODEL

In most of the predator-prey systems, prey individuals make transitions between vulnerable and invulnerable states or locations. This transition is regulated by various inducible defense mechanisms. Diel vertical migration （DVM） in zooplankton is the most effective and instantaneous defense observed in zooplankton population. Zooplankton shows downward vertical migration in the daytime in the presence of predators （or predator kairomones） to avoid predation （i.e. refuge use）, and it enters into the surface water again at night to graze phytoplankton. The dynamics of the planktonic ecosystem under DVM of zooplankton along with fish kairomone and the multiple delays due to migration for vulnerable and invulnerable prey and reproduction in the predator population is of considerable interest both in theoretical and experimental ecologists. By developing mathematical model, we analyze such a system. The conditions for which the system enters into Hopf-bifurcation are obtained. Moreover, the conditions for which the bifurcating branches are supercritical are also derived. Our results indicate that DVM along with the effect of kairomone and multiple delays with a certain range are responsible to enhance the stability of the system around the positive interior equilibrium point.

SOME SYNCHRONIZATION CRITERIA FOR GENERAL COMPLEX NETWORKS WITH COUPLING DELAYS

A general complex delayed dynamical network model with asymmetric coupling matrix is considered in this paper. For reducing the conservativeness of synchronization criteria, several novel synchronization stability conditions are presented by using delay decomposition methods. Numerical examples which are widely used to study delay-dependent synchronization stability are given to illustrate the effectiveness of the proposed methods.

DYNAMIC PRICE MODEL BASED ON TRANSMISSION DELAY——PETROLEUM PRICE FLUCTUATION IN CHINA

Petroleum is a kind of fundamental energy resource. Its price fluctuation transmits from upper-stream industry to the lower-stream industry as the production factors price changes. And this leads to the price changes of final consumption. Meantime, due to the cycle of industrial chain, the price changes of lower-stream industry also affect the upper-stream industry in return. This price transmission path is quite complicated. Firstly, it includes both direct and indirect paths; secondly, the transmission process is accompanied with time delay. The traditional input-output price model based on cost-push theory can efficiently solve the first problem when estimating the impact of price fluctuation on the whole price system. However, it neither reflects the dynamic characteristics of price transmission with time nor solves the second problem. To solve this problem, this paper uses the directed weighted network to describe the price transmission among industrial sectors by taking the time-dimension into account, and dynamic price transmission network model is constructed. This model not only describes transmission time delay more accurately, but also calculates the price fluctuation dynamically. On this basis, by utilizing the 2007 Chinese input-output table, this paper conducts empirical analysis on the impact of petroleum price fluctuation on other sectors. The empirical results indicate that the price fluctuation transmission mainly depends on two factors, the orice reaction period Tk and the consumption relationship with petroleum aik. 1） If t 〈 Tk, then the price change of sector k at period t △pkt = 0, the petroleum price fluctuation has not transmitted to the sector k, so the price of sector k remains unchanged. 2） If t 〉 Tk, then Apt 〉 0, and the greater aik, the higher price change rate. 3） If t →∞, it is the same with that in traditional input-output price model. So it can be clearly seen that dynamic price transmission network model is more general than the traditional model, and the traditional model is just an asymptotical special case when time approaches to infinity. Keywords Directed weighted network, input-output price model, petroleum price, transmission time delay.

Time-domain programmable digital multi-beamforming system

A new beamforming method in time-domain is described in this paper. Based on the pipe line architecture, the variable digital filtering algorithm, rising sampling rate (interpolation), down-sampling rate (decimation), and optimum weighting are combined. The high accuracy time-delay compensation for multi-beam signal processing system is designed by high speed RAM (Random Access Memory) and VLSI (Very Large Scale Integrated) DSP (Digital Signal Processing) chips. Comparing with the traditional beamforming method, the new method presented in this paper is highly accurate, less complex in computation, easy progranunable and have compact hardware architecture. The design philosophy of time-domain RAM-dynamic bearnforming method and hardware implementation is given.