基于动态KECA的工业过程故障检测

针对工业过程数据中存在的非线性特性和时间延迟性问题,提出了一种基于动态核熵成分分析(DKECA)的工业过程故障检测方法.将数据集按照时间序列构造增广矩阵,建立DKECA模型,并计算训练数据的Cauchy-Schwarz(CS)统计量及其控制限.将在线监测数据投影到DKECA模型上,其相应的统计量超出控制限的数据作为故障数据.实验结果表明,与传统的非线性方法相比,所提方法能够在保持较低误报率的基础上有效提升故障检测效果,通过引入时间延迟系数提取工业过程的动态变化信息,为传统故障检测方法在动态工业过程中的应用提供了参考.

基于深度学习构建时序基因调控网络

基因调控是生命体中重要的运行机制,运用深度学习来预测p53相关基因的调控关系对了解基因调控具有重要意义。提出了一种基于卷积神经网络与全连接网络相结合的模型。在ArrayExpress获得了电离辐射Affymetrix数据集(E-MEXP-549)上,可通过微阵列表达水平预测基因间调控关系,为保留的验证集提供92.07%分类准确率,并且该模型的kappa系数达到0.84,AUC验证平均精度达到94.25%,从而构建了带有时延性的p53相关的基因调控网络。研究结果表明,该模型在筛选出已经论证调控关系的基因对上具有较好的验证关系,构建出可视化的基因调控网络。在筛选出未知调控关系的基因对上,具有较好的预测关系与研究价值。

Robust PID controller design for time delay processes with peak of maximum sensitivity criteria

The motivation of this work is to obtain single PI/PID tuning formula for different types of processes with enhanced disturbance rejection performance. The proposed tuning formula consistently gives better performance in comparison to several well-known methods at the same degree of robustness for stable, integrating and unstable processes. For the selection of the closed-loop time constant(τc), a guideline is provided over a broad range of time-delay/time-constant ratios on the basis of the peak of maximum sensitivity(Ms). An analysis has been performed for the uncertainty margin with the different process parameters for the robust controller design. It gives the guideline of the Ms-value settings for the PI controller designs based on the process parameters uncertainty. Furthermore, a relationship has been developed between Ms-value and uncertainty margin with the different process parameters(k, τ and θ). Simulation study has been conducted for the broad class of processes and the controllers are tuned to have the same degree of robustness by measuring the maximum sensitivity, Ms, in order to obtain a reasonable comparison.

Robust Predictive Control of Uncertain Systems with Time-delay Using Tight Sets of Predicted States

A robust model predictive control (MPC) algorithm for discrete time linear systems with time-delay (RPC-TDS) subjected to constrained input control is presented, where the polytopic uncertainties exist in state matrices and input matrices. In the algorithm the standard optimization of quadratic objective function has been transformed into optimization of sum of N+1 upper bounds of the quadratic objective function with respect to N control moves and a state feedback control law, where N is the control horizon. The feasibility of the optimization problem guarantees that the algorithm is robustly stable. The simulation results verify the effectiveness of the proposed algorithm.

Exponential stability for networked control systems based on the model of nonlinear discrete-time system with time-varying delay

An uncertain nonlinear discrete-time system model with time-varying input delays for networked control systems (NCSs) is presented. The problem of exponential stability for the system is considered and some new criteria of exponential stability are obtained based on norm inequality methods. A numerical example is given todemonstrate that those criteria are useful to analyzing the stability of nonlinear NCSs.

Guaranteed cost sampled-data control for uncertain nonlinear time-varying delay system

The robust guaranteed cost sampled-data control was studied for a class of uncertain nonlinear systems with time-varying delay. The parameter uncertainties are time-varying norm-bounded and appear in both the state and the input control matrices. By applying an input delay approach, the system was transformed into a continuous time-delay system. Attention was focused on the design of a robust guaranteed cost sampled-data control law which guarantees that the closed-loop system is asymptotically stable and the quadratic performance index is less than a certain bound for all admissible uncertainties. By applying Lyapunov stability theory, the theorems were derived to provide sufficient conditions for the existence of robust guaranteed cost sampled-data control law in the form of linear matrix inequalities (LMIs), especially an optimal state-feedback guaranteed cost sampled-data control law which ensures the minimization of the guaranteed cost was given. The effectiveness of the proposed method was illustrated by a simulation example with the asymptotically stable curves of system state under the initial condition of x(0)=[0.679 6 0].

Delay-dependent robust control for uncertain discrete singular systems with time-varying delay

The design problem of delay-dependent robust control for uncertain discrete singular systems with time-varying delay is addressed in this paper. The uncertainty is assumed to be norm-bounded. By establishing a finite sum inequality based on quadratic terms, a new delay-dependent robust stability condition is derived and expressed in terms of linear matrix inequalities (LMIs). A suitable robust state feedback control law is presented, which guarantees that the resultant closed-loop system is regular, causal and stable for all admissible uncertainties. Numerical examples are given to demonstrate the applicability of the proposed method.

H_∞ Control Based on LMIs for a Class of Time-delay Switched Systems

The problem of H∞ stability analysis and control synthesis of switched systems with delayed states under arb/trary switchirg laws is considered. By means of Lyapunov function and linear matrix inequality tools, sufficient ctmdition of H∞ stability is presented in terms of linear matrix inequalities. Furthermore, the robust H∞ control synthesis via state feedback and output feedack is studied. Finally, a numerical example is given to demonstrate the effectiveness of the proposed method.

A novel stabilization approach for small signal disturbance of power system with time-varying delay

Small signal instability may cause severe accidents for power system if it can not be dear correctly and timely. How to maintain power system stable under small signal disturbance is a big challenge for power system operators and dispatchers. Time delay existing in signal transmission process makes the problem more complex. Conventional eigenvalue analysis method neglects time delay influence and can not precisely describe power system dynamic behaviors. In this work, a modified small signal stability model considering time varying delay influence was constructed and a new time delay controller was proposed to stabilize power system under disturbance. By Lyapunov-Krasovskii function, the control law in the form of nonlinear matrix inequality （NLMI） was derived. Considering synthesis method limitation for time delay controller at present, both parameter adjustment method by using linear matrix inequality （LMI） solver and iteration searching method by solving nonlinear minimization problem were suggested to design the controller. Simulation tests were carried out on synchronous-machine infinite-bus power system. Satisfactory test results verify the correctness of the proposed model and the feasibility of the stabilization approach.

Stochastic Resonance in a Bistable System with Time-Delayed Feedback Loops

The phenomenon of stochastic resonance of a bistable system subjected to linear time-delayed feedback loops driven by multiplieative Gaussian coloured noise and additive Gaussian white noise is investigated. Firstly, the analytic expression of the quasi-steady distribution function Ps （x, t） is derived by applying the unified coloured noise approximation and the Novikov Theorem; Secondly, the expression of the signal-to-noise ratio （SNR） is obtained in the adiabatic limit to quantify the stochastic resonance. Finally, tile effects of the linear coefficient a, the nonlinear coefficient b, the linear time-delayed feedback coefficient c and the delay time r on Ps（x,t） and SNR^± are discussed. It is found that the effects of the linear coefficient and the nonlinear coefficient, the positive linear time-delayed feedback coefficient and the negative linear time-delayed feedback coefficient, the positive delayed time and the negative delayed time on Ps（x,t） and SNR^± are different, respectively. This discussion would be helpful to the study of the system reliability and controlling stochastic resonance.

Robust Stability and Performance Comparison of PID and PPI Control

Predictive PI (PPI) control form, capable of time delay compensation, has been put forward recently. This control algorithm is essentially a PI controller with enhanced derivative action, which is not only suitable for long time delay process, but also of simple structure and excellent robust stability. The performance of PPI controller was demonstrated and compared with that of traditional PID controller by different tuning methods.

Stabilization of a class of nonlinear discrete time systems with time varying delay

The stability and stabilization of a class of nonlinear discrete time delayed systems(NDTDS) with time-varying delay and norm-bounded nonlinearity are investigated. Based on discrete time Lyapunov–Krasovskii functional method, a sufficient delaydependent condition for asymptotic stability of nonlinear systems is offered. Then, this condition is used to design a new efficient delayed state feedback controller(DSFC) for stabilization of such systems. These conditions are in the linear matrix inequality(LMI) framework. Illustrative examples confirm the improvement of the proposed approach over the similar cases. Furthermore, the obtained stability and stabilization conditions will be extended to uncertain discrete time delayed systems(UDTDS) with polytopic parameter uncertainties and also with norm-bounded parameter uncertainties.

Robust Stability Analysis of a Kind of Combined Integrating Control System

This paper offeres an exact study on the robust stability of a kind of combined integrating control system, and the robust stability belongs to the analysis of a kind of quasi-polynomial with two independent time delays. The parameters of stable space under time delay uncertainty are fixed after Rekasius transformation, and then a new cluster treatment of characteristic roots (CTCR) procedure is adopted to determine the stable space. By this strategy we find that the unstable space is not continuous and both Karitonov vertices theory and Edge theory are unable to be extended to quasi-polynomial under time delay uncertainty.

Effects of Higher-order Dispersion on Time Delay in Femtosecond Pulse Generated from a Nonlinear Optical Loop Mirror Constructed from Dispersion Decreasing Fiber

The time delay（TD） of femtoseeond pulses is studied for the first time, which generated from the nonlinear optical loop mirror composed of dispersion decreasing fiber（DDF-NOLM）. The results show that the higher-order dispersion and high order nonlinearities such as Raman frequency shift play a key role in producing TD, and that the time delay ean be suppressed by the third-order dispersion（TOD） in DDF-NOLM. The mechanism of the time delay suppression is also discussed in detail.

PID Controller Stabilization for First-order Integral Processes with Time Delay

Due to the widespread application of the PID controller in industrial control systems, it is desirable to know the complete set of all the stabilizing PID controllers for a given plant before the controller design and tuning. In this paper, the stabilization problems of the classical proportionalintegral-derivative （PID） controller and the singleparameter PID controller （containing only one adjustable parameter） for integral processes with time delay are investigated, respectively. The complete set of stabilizing parameters of the classical PID controller is determined using a version of the Hermite-Biehler Theorem applicable to quasipolynomials. Since the stabilization problem of the singie-parameter PID controller cannot be treated by the Hermite-Biehler Theorem, a simple method called duallocus diagram is employed to derive the stabilizing range of the single-parameter PID controller. These results provide insight into the tuning of the PID controllers.

A software reliability growth model for component-based software incorporating debugging delay and imperfect debugging

In view of the problems and the weaknesses of component-based software （ CBS ） reliability modeling and analysis, and a lack of consideration for real debugging circumstance of integration tes- ting, a CBS reliability process analysis model is proposed incorporating debugging time delay, im- perfect debugging and limited debugging resources. CBS integration testing is formulated as a multi- queue muhichannel and finite server queuing model （MMFSQM） to illustrate fault detection process （FDP） and fault correction process （FCP）. A unified FCP is sketched, given debugging delay, the diversities of faults processing and the limitations of debugging resources. Furthermore, the impacts of imperfect debugging on fault detection and correction are explicitly elaborated, and the expres- sions of the cumulative number of fault detected and corrected are illustrated. Finally, the results of numerical experiments verify the effectiveness and rationality of the proposed model. By comparison, the proposed model is superior to the other models. The proposed model is closer to real CBS testing process and facilitates software engineer＇ s quantitatively analyzing, measuring and predicting CBS reliability. K

The Network coding based on synchronization in wireless mesh networks self- similar traffic

The wireless mesh networks trathc are of selt：snmlarlty and the network pertOrmance is degraded by seltsimillar traffic. Network coding is a new technology which improves network performance. An algorithm is presented that it uses network coding to reduce queue length and delay time when self-similar traffic occurs. Based on synchronization, data packets are classified by destination address and lengths. Simulation results show that with the proposed synchronization techniques, network coding, even in scenarios with burst self-similar traffic, where network coding could not have been deployed so far, increases throughput and lowers packet loss in wireless mesh networks.

Characteristics of S-wave Envelope Broadening in the Changbaishan Tianchi Volcano

High-frequency S-wave seismogram envelopes of microearthquakes broaden with increasing travel distance,a phenomenon known as S-wave envelope broadening. Multiple forward scattering and diffraction for the random inhomogeneities along the seismic ray path are the main causes of S-wave envelope broadening,so the phenomenon of S-wave envelope broadening is used to study the inhomogeneity of the medium. The peak delay time of an S-wave,which is defined as the time lag from the direct S-wave onset to the maximum amplitude arrival of its envelope,is accepted to quantify S-wave envelope broadening. 204 small earthquake records in Changbaishan Tianchi volcano were analyzed by the S-wave envelope broadening algorithm. The results show that S-wave envelope broadening in the Changbaishan Tianchi volcano is obvious,and that the peak delay time of S-wave has a positive correlation with the hypocenter distance and frequency of the S-wave. The relationships between the S-wave peak delay time and the hypocenter distance for different frequency bands were obtained using the statistics method. The results are beneficial to the understanding of the S-wave envelope broadening phenomena and the quantitative research on the inhomogeneities of the crust medium in the Changbaishan Tianchi volcano region.

PERIODIC SOLUTION AND PERSISTENCE FOR A THREE-SPECIES RATIO-DEPENDENT PREDATOR-PREY MODEL WITH TIME DELAYS IN TWO-PATCH ENVIRONMENTS

The author considers a three-species ratio-dependent predator-prey model with time delay in a two-patch environments. This model is of periodic coefficients, which incorporates the periodicity of the environment. By means of the coincidence degree theory, sufficient conditions for the existence of at least one positive periodic solution of this model are established. Moreover, The author shows that the system is uniformly persistent under the conditions.

Hopf bifurcation and chaos in an inertial neuron system with coupled delay

In this paper, inertia is added to a simplified neuron system with time delay. The stability of the trivial equilibrium of the net- work is analyzed and the condition for the existence of Hopf bifurcation is obtained by discussing the associated characteristic equation. Hopf bifurcation is investigated by using the perturbation scheme without the norm form theory and the center man- ifold theorem. Numerical simulations are performed to validate the theoretical results and chaotic behaviors are observed. Phase plots, time history plots, power spectra, and Poincar6 section are presented to confirm the chaoticity. To the best of our knowledge, the chaotic behavior in this paper is new to the previously published works.