电气专业英语课文翻译(8)

The continuing advances in computer technology have had three principal effects on the controls field. one of these relates to the gigantic supercomputers. The size and class of problems that can now be modeled，analyzed，and controlled are considerably larger than they were when the first of this hook was written.

计算机技术的不断发展，已经对控制领域产生了三个方面的主要影响。影响之一与超大规模的巨型机有关。现在能够进行建模、分析和控制研究的问题的规模和困难级别都已经大大超过了本书的第一版的情况。

The second impact of computer technology has to do with the proliferation and wide availability of microcomputers in homes and in the work place. Classical control theory was dominated by graphical methods because at the time that was the only way to solve certain problems. Now every control designer has easy access to powerful computer packages for system analysis and design. The old graphic methods have not yet disappeared，but have been automated. They survive because of the insight and intuition that they can provide. However，some different techniques are often better suited to a computer. Although a computer can he used to carry out the classical transform-inverse transform methods, it is usually more efficient for a computer to integrate differential equations directly,

计算机技术的第二个影响与微型机在数量上的激增以及其在家庭、工作场所随处可用的便利性紧密相关。经典控制理论中图解方法占主导地位，这是因为当时图解式解决某些问题的唯一方法。现在，每一个控制工程设计人员都很容易获得功能强大的计算机软件包，用于进行系统的分析和设计工作。老的图解方法并没有消亡，不过已经能够自动进行工作了。他们之所以仍然存在的原因是其多具有的直观性和指导性。然而，一些完全不同的技术经常对计算机更加适合。尽管计算机课用于执行经典的变换-反变换运算，然而用计算机对微分方程直接进行积分则往往更加有效。

The third major impact of computers is that they are now so commonly used as just another component in the control system. Their cost, size and reliability make it possible to use them routinely in many systems. This means

Modern control theory LS well suited to the above trends because its time-domain techniques and its mathematical language (matrices，linear vector space, etc.) are ideal when dealing with a computer. Computers are a major reason for the existence of state variable methods.

现代控制理论特别适应上述的发展趋势。这是因为时间域技术及其数学表达语言（例如矩阵、线性向量空间等）在计算机上应用是非常理想的。计算机的发展也是状态变量方法之所以会产生的一个主要原因。

Most classical control techniques were developed for linear constant coefficient systems with one input and one output(perhaps a few inputs and outputs).The language of classical techniques is the Laplace or z-transform and transfer functions. When nonlinearities and time variations are present，the very basic for these classical techniques is removed. Some successful techniques such as phase-plane methods，describing functions and other ad hoc methods，have been developed to alleviate this shortcoming. However the greatest success has been limited to low-order systems. The state variable approach of modern control theory provides a uniform and powerful method of representing systems of arbitrary order，linear or nonlinear，with time-varying or constant coefficients. It provides an ideal formulation for computer implementation and is responsible for much of the progress its optimization theory.

大多数经典控制技术都是带有一个输入、一个输出（也许可有数个输入和输出）的线性、常系数系统而发展起来的。经典技术的表述语言是拉普拉斯或z变换以及传递函数。一旦出现非线性和时变性，经典技术最根本的基础就不复存在了。诸如相平面方法、描述函数法和其他有关方法这样一些很成功的技术能够得以发展的原因就是为了弥补这个短处。然而经典控制理论最大的成功也是局限于低阶系统中。现代控制理论的状态变量法提供了一种统一、高效的方法来描述具有任意阶次、线性或非线性、时变或常系数的各种系统。它也为计算机处理提供了一种理想的表达方法，并引起了许多方面的最优化理论的进展。

Modern control theory is a recent development in the field of control. Therefore，the name is justified at least as a descriptive title. However, the foundation of modern control theory is to be found in other well-established fields, representing a system in terms of state variables is equivalent to the approach of Hamiltonian mechanics，using generalized coordinates end generalized moments. The advantages of this approach have been well-known in classical physics for many years. The advantages of using matrices when deals with simultaneous equations of carious kinds have long been appreciated in applied mathematics. The field of linear algebra also contributes heavily to modern control theory. This due to the concise notation，the generality of the results，and the economy of thought that linear algebra provides.

现代控制理论是在控制领域中的新发展。因此可以说它是名副其实。然而现代控制理论的基础却应该在其他一些发展成熟的领域中寻找。以状态变量形式来表示一个系统的方法完全等价于再其他哈密尔顿力学中采用通用坐标和通用动量的方法。这种方法的优越性在经典物理学中多年来已经众所周知。当处理各种联立方程式采用矩阵的好处在应用数学领域中也已久为人知。线性代数对现代控制理论的发展更是功不可没。其原因在于线性代数所提供的简洁的表达、通用的结果以及高效的思路。

If we examine the word control, we find several meanings given in dictionary, e.g. command, direct, govern, and regulate. Thus, a control system may be regarded as a group of physical components arranged to direct the flow of energy to a machine or process in such a manner as to achieve the desired performance.

The word automatic means self-moving or self-acting; thus an automatic control system is a self-acting control system.

如果查询单词控制，我们会在字典中找到一些意思：命令，执行，管理和规范。因此控制系统可以称为是一组物理器件组合在一起执行机械或者程序的能量流动，从而获得给定特性。

自动这个单词的意思是自运动，自动做，因此一个自动控制系统是自动做控制系统。

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