外文翻译---自动控制基础

附录英文资料及其译文

CHAPTER 1 Basis of the automatic control

1. 1. Out line

This device is temperature control experimental device of temperature, lever, pressure , that are the most common control subject for water treatment plants, chemical factories and power plants.

At the experiment of automatic control, it is very important to keep the balance of system. Automatic control system is composed of control subjects and to keep control device. Especially process control has many control subjects to keep self-balance, so the experimental results is conducted with balance condition.

This experimental device experiments about the relation of input signal and output signal to keep the balance (System characteristics) at the cascade experiment and fixed command control, also experiments on dynamic characteristic (Balance condition without time variation),static characteristic (Balance condition considerating time variation).

And you record the change of control amount which was input handling amount or establishment of characteristic experiment. These typical response can be thought step response . Y ou experiment optimum control experiment , fixing P . I. D constant of control device

, relating this step response.

2. Process control

Process control keeps the balance of the system, automatically correcting toward deviation, and compares every variable to operating toward deviation, and compares every variable to operation condition of industrial process of flux, temperature, surface, pressure, etc with the established goal. Process control is decided into closed loop and Open loop control.

3. Kinds of automatic control

Control is composed of detection (measurement), comparison, judgment, operation and manual control is done by man’s hand and automatic control is done by measure or adjuster or other machinery. At present, automatic control is taken at the many plants .Moreover , we cannot think plant control without automatic control.

Kinds of automatic control is decided like below.

Automatic control Open loop control

Sequential control

Closed loop control Feedback control

3-1 .Feed back control

Feed back control detects (measure) compares , judges ,operates ,automatically. And it measures the results every moment , and corrects automatically if there is any differential between the desired value (set value).

Feed back control is one of the main process control .

This is the control that detecting (measuring) the results (Control amount: tank water lever ) with differential transmitter, and comparing the value with the set water lever and correct the deviation(Opening operation flow control of the control value)

Like the above, feed back control automatically does the movement of measurement(detection) comparison calculation modernfication. Feed back system has the element of doing these functions.

At the diagram 3-1 block line diagram it is the closed loop and it transmitted the correcting signal of the opposition toward the process flow.

Diagram 3—1 Block line diagram of feed back control corollary

Block line diagram: Indicating the constructing element of control system in block , and connecting the line expressing the signal flow.

Signal :The amount being used for transmit the information

3-2.Feed forward control

Feed forward control is the control method doing necessary correct movement before the influence appears to the control system , when disturbance enters into the control system.

At feed back control, it starts correct movement to erase the deviation after the influence by disturbance appears, so in case of sudden change of disturbance or set value, then control disorders transiently and arises many problems.

Feed forward control breaks down this weak point.

At feed forward control, results of the controller is not done feedback and becomes open-loop control, not being close-loop control. Accordingly, in case of feed back control, the relation between cause and effect of disturbance and the results of control must be understood well. That is ,relation of influence to the control amount toward load change, and operating amount needed to compensate it should be clear.

But it is generally difficult. In many cases it is difficult that all the disturbance is detected, and