外文翻译-现代的控制理论的简单介绍.doc

1、毕 业 设 计 外 文 参 考 资 料 及 译 文译文题目： 现代的控制理论的简单介绍 学生姓名： 学 号： 专 业： 所在学院： 指导教师： 职 称： 20xx年 2月 27日Introduction to Modern Control TheorySeveral factors provided the stimulus for the development of modern control theory: a. The necessary of dealing with more realistic models of system.b. The shift in emphasis

2、towards optimal control and optimal system design. c. The continuing developments in digital computer technology. d. The shortcoming of previous approaches. e. Recognition of the applicability of well-known methods in other fields of knowledge.The transition from simple approximate models, which are

3、 easy to work with, to more realistic models, produces two effects. First, a large number of variables must be included in the models. Second, a more realistic model is more likely to contain nonlinearities and time-varying parameters. Previously ignored aspects of the system, such as interactions w

4、ith feedback through the environment, are more likely to be included. With an advancing technological society, there is a trend towards more ambitious goals. This also means dealing with complex system with a large number of interacting components. The need for greater accuracy and efficiency has ch

5、anger the emphasis on control system performance. The classical specifications in terms of percent overshoot, setting time, bandwidth, etc. have in many cases given way to optimal criteria such as mini mum energy, minimum cost, and minimum time operation. Optimization of these criteria makes it even

6、 more difficult to avoid dealing with unpleasant nonlinearities. Optimal control theory often dictates that nonlinear time-varying control laws are used, even if the basic system is linear and time-invariant. The continuing advances in computer technology have had three principal effects on the cont

7、rols field. One of these relates to the gigantic supercomputers. The size and the class of the problems that can now be modeled, analyzed, and controlled are considerably large than they were when the first edition of this book was written. The second impact of the computer technology has to so with

8、 the proliferation and wide availability of the microcomputers in homes and I 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

9、systems analysis and design. The old graphical methods have not yet disappeared, but have been automated. They survive because of the insight and intuition that they can provide, some different techniques are often better suited to a computer. Although a computer can be used to carry out the classic

10、al transform-inverse transform methods, it is used usually more efficient for a computer to integrate differential equations directly.The third major impact of the computers is that they are now so commonly used as just another component in the control systems. This means that the discrete-time and

11、digital system control now deserves much more attention than it did in the past.Modern control theory is well suited to the above trends because its time-domain techniques and its mathematical language (matrices, linear vector spaces, etc.) are ideal when dealing with a computer. Computers are a maj

12、or reason for the existence of state variable methods.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.

13、When nonlinearities ad time variations are present, the very basis for these classical techniques is removed. Some successful techniques such as phase-plane methods, describing function s, and other ad hoc methods, have been developed to alleviant this shortcoming. However, the greatest success has

14、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 coefficient. It provides an ideal formulation for computer implementation and

15、is responsible for much of the progress in optimization theory. 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 foundations of modern control theory are 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 and generalized moment. The advantages of this approach have been well-known I classical physics for many years. The advantages of using mat