T68型卧式镗床的PLC改造

T68卧式镗床是一种多用途的金属切削机床,传统的镗床采用继电——接触器控制,系统接线复杂,故障率高,可靠性差。本文介绍采用三菱公司的FX1N-40MR型PLC进行改造T68镗床。本文介绍改造程序和调试过程。根据T68镗床的加工工艺和工作原理,设置PLC的I／O地址,设计外部设备接线,根据原理图、控制要求和特点,设计系统梯形图,连接外部设备进行调试运行,达到系统改造的要求。     

A bifurcation method to calculate flutter characteristics of a helicopter blade having complex damping

A new method is presented for determining the stability and vibration modes of a class of parametric oscillations where the damping terms in the Mathieu-Hill type of differential equations are complex as well as periodic. The imaginary terms are converted to phase lagged terms in a set of simultaneous first-order differential equations used to express these equations with first-order derivatives treated as additional variables, thereby doubling the number of equations but allowing matrix methods to be conveniently used in a bifurcation procedure to obtain solutions and stability boundaries. The method has advantages over methods using series expansions in determining stability boundaries and vibration modes where convergence and summability become important considerations in the case of differential-difference equations with periodic damping terms. A particular example of a fluttering helicopter blade in slow forward flight is studied and stability boundaries shown to be displaced by up to 10% from those when the nature and extent of the rows of wakes below the rotor are neglected. The range of the parameters governing the stability are given for a specific numerical example. Application to an actual blade motion study shows reconciliation with previous experimental results and theory when the new method is applied. The importance of the effect of lagged arguments in simultaneous differential-difference equations is discussed with reference to two other examples in structural vibrations.     

On the Salient Properties of the Hysteresis Machine—I. Non-conducting Rotor

The properties of the hysteresis machine are analyzed on the basis of a cylindrical model. The electromagnetic field in the various regions of the motor is derived by field-theoretical methods (such as Maxwell's equations and Poynting's theorem), and the resulting parameters are applied in turn in determining torques and other relevant quantities. Three limiting particular cases of special interest are examined.     

Stability analysis of nonlinear control systems with characteristics equations having complex coefficients

In this paper, the stability equation method is applied to the analysis of nonlinear systems with characteristics equations having complex coefficients. Three types of systems are studied: those with unstable open-loop poles, unstable characteristics roots or an equal number of open-loop poles and zeros.     

A procedure to obtain the initial amplitude and phase for the Krylov–Bogoliubov method

Using the Krylov–Bogoliubov method for obtaining analytical solutions to systems with small non-linearities, a procedure is employed to determine the initial amplitude and phase in terms of the initial displacement and velocity. Equations representing the time rate of change of amplitude and phase are used directly. Whether the corresponding linear equations of the non-linear system has purely imaginary, complex conjugate or real roots, the same procedure can be applied.An example is given which demonstrates the initial amplitude and phase change for various higher order approximations.     

Hodograph transformation

Mapping of curves from the physical to the hodograph plane, when the Jacobian vanishes along a curve is discussed in detail here. A certain quadratic expression occuring in the equations has been identified as the important factor in the transformation. The nature of the transformation depends on whether the roots are complex or real distinct and so on. A geometrical representation of the referred quadratic expression is also presented, resulting in a better understanding of the transformation technique.     

基于遗传算法参数优化的最小二乘支持向量机财务困境预测

传统支持向量机应用于财务困境预测时,需要求解复杂的二次规划问题,求解难度大。而最小二乘支持向量机模型可以将二次规划问题变成一个线性方程组来求解,有效降低了模型求解的难度。尤其是将遗传算法应用于最小二乘支持向量机模型参数和核参数的优化时,显著提高了模型预测的正确率。本文从沪深两市随机抽取了2002年-2007年252家A股上市公司作为研究样本,并把研究样本分为两组,对这两组样本数据分别进行了短期及中长期预测。实证结果表明,基于遗传算法的最小二乘支持向量机模型的预测效果不但好于传统统计类Logit模型,也优于传统支持向量机模型。短期预测效果显著优于中长期预测效果,训练样本数直接影响到模型的预测效果,二者呈正相关关系。     

交互式汉—英机器翻译的理论基础

理想的机器翻译系统应该是全自动高质量的批处理式系统,在目前的计算语言学发展水平下,计算机还无法彻底解决自然语言的错综复杂现象,达到全自动高质量的翻译。本文认为人机交互的方法是最自然的手段,用户易学易会,具有广阔的发展前景。文章详细地分析归纳汉—英机器翻译的歧义问题,总结了现有的解决歧义的手段,提出了用人机对话解决歧义问题的交互式汉—英机器翻译的思想,并从语言学的角度提供了论据。基于这一思想设计的CEMT—Ⅱ汉英机器翻译系统模型已基本完成。     

非线性方程的智能化实现及应用

方程和方程组的解法一直是相关研究人员关注的焦点。针对非线性方程的解法做出智能化实现,以各种解方程的数学原理、方法为基础,以MATLAB为主要计算工具,编写程序实现智能化、最优化、简便化地解方程的根;进行各种分析,并应用于实际例子,验证其正确性、可行性以及智能化。     

A new approach to the modeling of distributed structures for control

Building structures represent complex distributed-parameter systems. The motion of such systems is described by partial differential equations complemented by suitable boundary conditions. For control design purposes, distributed-parameter systems must be discretized in the spatial variables. But, if the discrete model is not sufficiently accurate, controls designed on the basis of the discrete model can destabilize the actual distributed structure, in which case the controls are said to be sensitive to discretization errors. This paper presents a new approach to the discretization of distributed structures yielding accurate discrete models of relatively low order. A numerical example illustrates how controls can be designed for a complex structure subjected to earthquake excitations.     

On the Salient Properties of the Hysteresis Machine—II. Eddy-current Effects

The analysis of the asynchronous behavior of the hysteresis machine is undertaken based on a model describing its cylindrical structure. Assuming that the hysteresis shell of the rotor is manufactured out of materials with finite conductivities, the influence of the induced eddy- currents on the machine performance is pointed out via Maxwell's equations and Poynting's theorem. The characteristics of the machine are computed as functions of slip and three interesting limiting cases are revealed.     

一类多时滞的向量差分方程的渐近稳定性（英文）

本文讨论了一类具有时滞的差分方程的渐近稳定性。利用矩阵性质和不等式技巧给出了该类方程渐近稳定的充要条件。     

Electrodynamics of solid-rotor induction machines

In this paper a simplified model of the solid-rotor induction machine is discussed. Analysis is provided on the basis of Maxwell's equations yielding a dimensionless thrust-slip characteristic which permits rapid evaluation of various machine parameters in its performance. The salient feature of this kind of induction device—flat thrust-slip response—is borne out by the obtained curves.     

Eddy Current Effects on the Asynchronous Performance of the Hysteresis Machine

An analysis of the asynchronous behavior of the hysteresis machine is undertaken based on a “rectified” model of its structure. The hysteresis shell and the yoke of the rotor are assumed as being manufactured out of materials with finite conductivities. The field analysis undertaken via Maxwell's equations and Poynting's theorem shows the influence of the induced eddy currents on the machine performance at nonvanishing slips. The characteristics of the machine are computed as functions of slip, revealing three particularly interesting cases.     

A unified Krylov-Bogoliubov-Mitropolskii method for solving nth order nonlinear systems

A unified theory is presented for obtaining the transient response of nth order nonlinear systems with small nonlinearities by Krylov-Bogoliubov-Mitropolskii method. The method is a generalization of Bogoliubov's asymptotic method and covers all three cases when the roots of the corresponding linear equation are real, complex conjugate, or purely imaginary. It is shown that by suitable substitution for the roots in the general result that the solution corresponding to each of the three cases can be obtained. The method is illustrated by examples.     

实代数数符号判定的一种新算法

根据多元多项式结式、笛卡尔符号法则、多项式实根隔离和实连续函数的性质等理论,给出对任意实代数数进行符号判定的一种新算法.测试实例表明,本文提出的算法还能有效地解决Maple系统中关于浮点数运算的一些缺陷.     

Integraph solution of differential equations

In a previous article¹ a continuously recording integraph was described, by means of which differential equations, involving only one integration, could be solved. The present article describes a revision of this machine such that an equation involving two successive integrations, corresponding to practically any second-order total differential equation, with all terminal conditions included, can be solved. The need for a workable means of solving the differential equations involving empirical and discontinuous coefficients which occur repeatedly in electrical engineering and physics is recalled. In the machine described such solutions are effected by means of suitable interlinked integrating devices, the result being plotted continuously as a function of the independent variable. Tests and simple solutions show the over-all error to be approximately 1 or 2 per cent. The various sources of this error are discussed.     

A continuous integraph

A mechanical integraph has been developed which plots continuously the integral of the product of two functions. It uses the principle of the electrical integrating watthour-meter combined with a moving table. Errors of the machine have been reduced to an average of 1 per cent. for common uses. By cross-connecting the device in a simple mechanical way, it is possible to solve certain types of integral equations. A link motion has been added which plots the product of two given functions. Various uses have been made of the instrument for solving problems in connection with electrical circuits, continuous beams, etc., and certain problems involving integral equations.     

Continuous fixed-time convergent regulator for dynamic systems with unbounded disturbances

This paper presents a novel continuous fixed-time convergent control law for dynamic systems in the presence of unbounded disturbances. A continuous fixed-time convergent control is designed to drive all states of a multi-dimensional integrator chain at the origin for a finite pre-established (fixed) time, using a scalar input. The fixed-time convergence is established and the uniform upper bound of the settling time is computed. The designed control algorithm is applied to fixed-time stabilization of two mechatronic systems, a cart inverted pendulum and a single machine infinite bus turbo generator with main steam valve control.     

Numerical solution of systems of mixed partial differential equations associated with transport phenomena with exchange

The so-called “percolation operations” which involve simultaneous heat and mass transport are defined in terms of a system of mixed partial differential equations which are nonlinear and include variable coefficients. Second-order interpolation followed by integration over an increment of the time or space variable is proposed as a method for arriving at finite difference equation equivalents of the original partial differential equations. A model change is also used to give physical significance to finite difference equivalents associated with derivatives in the space dimension. It is shown that second-order interpolation has the advantage over linear interpolation that it introduces a factor β which in a stability analysis based on cencentrations offers a range of choices that will insure stable calculation on a digital machine.