Stabilization of carrier-frequency servomechanisms. I. Gain-phase margin diagrams of controller characteristics

In this first part a method of analysis of linear carrier-frequency systems is indicated, and applied in particular to electrical servomechanisms using a two-phase alternating-current control motor. The performance of such a servo, as regards stability and fidelity of the output as a copy of the input, depends on the action of a controller-demodulator unit including the motor. A calculation of the steady-state effect of a linear transfer characteristic on the suppressed-carrier modulated error signal makes possible application of the Nyquist stability criterion.The method does not require symmetry of the characteristics about the carrier frequency; if such symmetry is present the system is similar to an ordinary or d-c. servo. Thus a band-rejection network tuned to the carrier frequency has an approximate proportional plus derivative action on the envelope of the error signal, resulting in an “anti-hunt” or stabilizing effect similar to that due to a translated band-rejection characteristic (center at zero-frequency) in a corresponding d-c. servo.A procedure is given for construction of transformed Nyquist diagrams, or gain-phase margin diagrams. The effect of the correctly tuned band-rejection network, as well as the effects of bandwidth, of the network being tuned off the carrier frequency, of increasing gain or velocity constant k_ν, and of the use of phase-shifting networks, are clearly shown by a series of such diagrams.     

Stabilization of carrier-frequency servomechanisms. III. Methods of obtaining required carrier phase-shift

In a servomechanism using a two-phase alternating current control motor, a 90° difference is required in the phases of the carrier-frequency voltages applied to the fixed and control windings. This part describes and compares various methods of obtaining the phase difference.The question of the possibility of a phase-shifting proportional-derivative parallel “T” is answered in the negative, by the result that in any parallel “T” transfer characteristic, if the quadratic factor in the numerator is of the proportional-derivative form at the correct resonant frequency, the amount of phase shift which may be obtained from the remaining portion of the transfer characteristic is less than are tan $\text{(}\text{2}\text{n}\text{)}$, where n is twice the carrier frequency divided by notch width. Thus for values of n high enough to have an appreciable stabilizing effect, the maximum obtainable intrinsic phase shift is negligible.In order to obtain a large phase shift it is necessary to add either a series input or a load impedance to the parallel “T,” or to use a phase-shifting network preceding or following the parallel “T.” Formulae and design charts are given for determination of the values of the components of phase lag networks.The method of calculation of tolerance requirements on the components, in terms of allowable deviation from the correct phase, is illustrated by an example of a phase lag network used in conjunction with a bridge “T” proportional-derivative network.     

Stabilization of Boolean control networks with stochastic impulses

This paper studies the stabilization problem of Boolean control networks with stochastic impulses, where stochastic impulses model is described as a series of possible regulatory models with corresponding probabilities. The stochastic impulses model makes the research more realistic. The global stabilization problem is trying to drive all states to reach the predefined target with probability 1. A necessary and sufficient condition is presented to judge whether a given system is globally stabilizable. Meanwhile, an algorithm is proposed to stabilize the given system by designing a state feedback controller and different impulses strategies. As an extension, these results are applied to analyze the global stabilization to a fixed state of probability Boolean control networks with stochastic impulses. Finally, two examples are given to demonstrate the effectiveness of the obtained results.     

Stabilization of dynamic-algebraic Boolean control networks via state feedback control

In this paper, we study the state feedback stabilization of dynamic-algebraic Boolean control networks (DABCNs). Using a novel normalization approach, we present necessary and sufficient conditions for the feedback stabilization of DABCNs, and a construction method for the corresponding feedback controllers is proposed. Reduced order feedback stabilization is also studied in this paper. Two examples are given to illustrate the obtained results.     

Stabilization effect of diffusion in delayed neural networks systems with Dirichlet boundary conditions

In this paper, reaction–diffusion neural networks with unbounded time-varying delays and Dirichlet boundary conditions is studied. A new concept of global μ-stability in the sense of L² norm is introduced, and sufficient conditions are given to guarantee global μ-stability of the equilibrium point. The results obtained not only improve those in the earlier findings, but also show diffusion terms contribute to stabilization of neural networks systems.     

Design of a model-based online management information system for interlibrary loan networks

The inputs to mathematical models of library operations require periodic updating. The data collection effort necessary for such updating can be quite expensive. However, if the data collected can serve multiple purposes, the costs can perhaps be justified. A management information system offers a vehicle for multiple uses of data and thus, offers an appropriate environment for implementation of models of library operations. Within this paper, the design of a model-based management information system is discussed in terms of mathematical /statistical, information processing, and human factors issues. A prototype system for interlibrary loan networks is discussed.     

Design of memory controllers for finite-time stabilization of delayed neural networks with uncertainty

In this paper, we investigate the problem of finite-time stabilization of time-varying delayed neural networks with uncertainty. By employing the Lyapunov approach and linear matrix inequalities (LMIs), two different memory controllers are derived to achieve the finite-time stabilization of the addressed neural networks. Moreover, the upper bound of the setting-time for stabilization can be estimated via different Lyapunov functions. Our results improve and extend some recent works. Finally, the effectiveness and feasibility of the proposed controllers are demonstrated by numerical simulations.     

一组多输入非线性系统的同时镇定(英文)

考虑设计一个控制器同时镇定一组多输入非线性系统的问题.利用李雅普诺夫函数方法, 给出了时不变同时镇定状态反馈控制器存在地充分条件,然后给出构造同时镇定一组系统的连续控制器的统一公式. 该结果是对文献[1]中讨论的单输入系统的结论的推广.     

基于非线性方程组数值解法的严格正则系统同时镇定

先运用多项式分解，将严格正则线性系统同时镇定问题化成一组相容非线性方程的求解，然后提出了一种求解相容非线性方程组的拟牛顿下山数值算法，并应用该方法求解同时镇定问题。算例表明本文方法的有效性。     

Stabilization irrespective of bounds of uncertain variations for linear uncertain systems with delays

In this study, the stabilizability irrespective of the bounds of uncertain parameters and time delays is investigated for linear uncertain delay systems. For uncertain systems without delays, a linear time-varying or time-invariant uncertain system has been shown to be stabilizable independent of the bounds of uncertain variations if and only if the system has a particular geometric configuration called an antisymmetric stepwise configuration (ASC) or a generalized antisymmetric stepwise configuration (GASC), respectively. In this study, fundamental approaches to investigating the stabilizability of delay systems with specific uncertainty structures such as ASCs or GASCs are presented. For a class of 3-dimensional systems, it is shown here that if a linear time-varying or time-invariant uncertain delay system has an ASC or a GASC, respectively, then the system can be stabilized, however large the given bounds of delays and uncertain parameters might be.     

Stabilization for a class of strict-feedback nonlinear systems via the PWM control law

This paper studies the PWM control problem of a class of nonlinear systems. During a modulation period, the PWM control signal maintains a pulse waveform with tunable width and fixed magnitude. The PWM control only possesses finite states, and has relatively limited control capability. This causes the degradation of system performance, and even the instability when implementing into a nonlinear system. We will introduce a novel method to design both the state feedback stabilizer and the output feedback stabilizer for strict-feedback nonlinear systems via the PWM control. The system performance is analyzed in a novel framework and the stability criteria is derived to ensure the system convergence. At last, two examples are considered to illustrate the effectiveness of our proposed method.     

知识网络的构建过程分析

本文在分析组织存在知识缺口问题的基础上 ,指出了构建知识网络的实际意义 ,并进一步提出了知识网络构建过程中的构成要素、构建原则和构建方法。最后通过春兰集团的一个实际分析案例 ,说明了组织如何构建知识网络以及知识网络所体现的显著成效     

基于.NET的网络店铺管理系统设计

本文针对.NET平台的技术特点,结合社交网站设计思路与常规的网络店铺结构理念,设计了一种集休闲娱乐于一体的新网络店铺模式,解决了传统店铺功能单一、安全性低等问题,易于开发实现并且系统稳定性强。软件测试结果表明,基于.NET平台设计的网络店铺管理系统能实现功能的多样化,并有效解决数据的冗余、重复问题,系统运行正常。     

新农村建设中知识服务网络模式分析

建立具有知识服务特点的新农村将对构建和谐社会提供多方面的支持,如何构建与城市无缝衔接的先进的知识服务模式成为目前新农村建设中不可避免的问题.本文针对目前新农村建设中的热点问题,注重各种知识在农村领域的应用,提出了构建知识服务网络的机制,并对文化知识网络模式、村务公开服务网络模式、科技知识协作网络模式和农产品知识服务网络模式进行了较详尽的阐述,为相关研究决策提供一种新的思路.