A robust observer‐based stabilization method for systems with uncertain parameters and Lipschitz nonlinearities

This paper deals with the robust observer‐based control design for a class of Lipschitz nonlinear discrete‐time systems with parameter uncertainties. Based on the use of a reformulated Lipschitz property combined with the slack variable techniques and some mathematical artifacts, it is shown that the solution of the discrete‐time output feedback stabilization problem is conditioned by a set of bilinear matrix inequalities, which become linear matrix inequalities by freezing some scalars. Furthermore, we show that some existing and elegant results reported in the literature can be regarded as particular cases of the stability conditions presented here. Numerical examples are provided to show the validity and superiority of the proposed method. Copyright © 2015 John Wiley & Sons, Ltd.     

H∞Fuzzy State‐Feedback Control Plus State‐Derivative‐Feedback Control Synthesis for Photovoltaic Systems

This paper addresses the problem of designing an H_∞fuzzy state‐ feedback (SF) plus state‐derivative‐feedback (SDF) control system for photovoltaic (PV) systems based on a linear matrix inequality (LMI) approach. The TS fuzzy controller is designed on the basis of the Takagi‐Sugeno (TS) fuzzy model. The sufficient condition is found such that the system with the fuzzy controller is asymptotically stable and an H_∞performance is satisfied. First, a dc/dc buck converter is considered to regulate the power output by controlling state and state‐derivative variables of PV systems. The dynamic model of PV systems is approximated by the TS fuzzy model in the form of nonlinear systems. Then, based on a well‐known Lyapunov functional approach, the synthetic is formulated of an H_∞fuzzy SF plus SDF control law, which guarantees the L₂‐gain from an exogenous input to the regulated output to be less than or equal to some prescribed value. Finally, to show effectiveness, the simulation of the PV systems with the proposed control is assessed by the computer programme. The proposed control method shows good performance for power output and high stability for the PV system.     

Gain‐Scheduled Control via Switching of LTI Controllers and State Reset

This paper proposes a synthesis method of gain‐scheduled control systems that switch linear time‐invariant controllers according to hysteresis of the scheduling parameter. Stability and L₂‐gain analysis and synthesis methods for switched systems are applied to the switched gain‐scheduled control synthesis using reset of the controller state, where also the reset law is computed via linear matrix inequalities (LMIs). In addition to optimization of an upper bound of L₂‐gain, we reduce jumps of control input via an auxiliary optimization. Numerical examples are presented to illustrate the switched gain‐scheduled controller.     

二级倒立摆控制器设计及稳定性研究

在二级倒立摆控制器优化设计的研究中,由于二级倒立摆系统是一种复杂多变量、强耦合的不稳定系统,较难达到稳定平衡状态,首先要建立模型,之后才能够进行系统仿真与实际控制实验.由于系统对控制器性能要求较高,因此选用遗传算法训练的小波神经网络控制器,并针对遗传算法仍然存在的收敛速度慢,泛化性能差,可能陷入“早熟”等许多问题,对算法加以改进.将采用罚函数为基础的小生境技术引进到遗传算法中;并根据个体适应度来改进交叉概率.在仿真与实物控制实验中,控制器能够实现二级倒立摆系统的稳定控制,且抗干扰能力、系统平衡恢复速度优良,验证了设计的二级倒立摆控制器的有效性.     

Exponential stability of stochastic singular delay systems with general Markovian switchings

In recent years, Markovian jump systems have received much attention. However, there are very few results on the stability of stochastic singular systems with Markovian switching. In this paper, the discussed system is the stochastic singular delay system with general transition rate matrix in terms of uncertain and partially unknown transition rate matrix. The aim is to answer the question whether there are conditions guaranteeing the underlying system having a unique solution and being exponentially admissible simultaneously. The proposed results show that all the features of the underlying system such as time delay, diffusion, and general Markovian switchings play important roles in the system analysis of exponential admissibility. A numerical example is used to demonstrate the effectiveness of the proposed methods. Copyright © 2014 John Wiley & Sons, Ltd.     

Stochastic stability and stabilization of discrete‐time singular Markovian jump systems with partially unknown transition probabilities

This paper considers the stochastic stability and stabilization of discrete‐time singular Markovian jump systems with partially unknown transition probabilities. Firstly, a set of necessary and sufficient conditions for the stochastic stability is proposed in terms of LMIs, then a set of sufficient conditions is proposed for the design of a state feedback controller to guarantee that the corresponding closed‐loop systems are regular, causal, and stochastically stable by employing the LMI technique. Finally, some examples are provided to demonstrate the effectiveness of the proposed approaches. Copyright © 2014 John Wiley & Sons, Ltd.     

Decentralized Networked Control System Design Using Takagi-Sugeno (TS) Fuzzy Approach

This paper proposes a new method for control of continuous large-scale systems where the measures and control functions are distributed on calculating members which can be shared with other applications and connected to digital network communications.At first, the nonlinear large-scale system is described by a Takagi-Sugeno(TS) fuzzy model. After that, by using a fuzzy LyapunovKrasovskii functional, sufficient conditions of asymptotic stability of the behavior of the decentralized networked control system(DNCS),are developed in terms of linear matrix inequalities(LMIs). Finally, to illustrate the proposed approach, a numerical example and simulation results are presented.     

Delay dependent robust stability of singular systems with additive time-varying delays

This paper considers the problem of delay-dependent robust stability for uncertain singular systems with additive time-varying delays. The purpose of the robust stability problem is to give conditions such that the uncertain singular system is regular, impulse free, and stable for all admissible uncertainties. The results are expressed in terms of linear matrix inequalities (LMIs). Finally, two numerical examples are provided to illustrate the effectiveness of the proposed method.     

基于离散小波变换的改进SPIHT算法研究

随着现代信息社会对通信业务要求的不断增长,图像通信与通信容量的矛盾日益突出。为了缓解网络带宽的不足、加快图像信息的传播速度,对于基于高比率的图像压缩算法的研究很有必要。目前比较流行的多级树集合分裂算法压缩效果比较好,输出的比特流较少,但是需要对内存中的数据反复的读取,且反复的在链表结构中扫描不重要系数,增加内存的负担及软硬件实现的复杂度,从而降低了编码的效率。本文针对多级树集合分裂算法的缺点提出了一种基于离散小波变换的改进的多级树集合分裂算法,通过对小波系数排序过程的调整,减少了对内存反复的读取操作,减轻了对内存造成的负担,提高了编码的效率。     

一种基于改进支持向量机的文本倾向性分类算法

文本的倾向性分类器是文本倾向性分类的核心部分,它用于将待分类的文本映射到某一倾向性类别中去。传统支持向量机的核函数学习能力和泛化推广能力的平衡性有待提高,而且参数选择不易。对目前文本倾向性分类算法使用的传统的支持向量机进行了改进,一是构造了多核函数;二是使用粒子群算法对支持向量机的参数进行优化,平衡了核函数的全局性和局部性,更有利于对样本数据的学习和推广;最后利用改进的支持向量机构造文本倾向性分类算法。