1、 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 contro
2、l, 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 de
3、vice 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 consi
4、derating 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 . You experiment optimum control experiment , fixing P . I. D constant of control device , relating
5、 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, press
6、ure, 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 mans hand and automatic control is done by measure or adj
7、uster 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 Feed forward control Sequential control Closed loop control F
8、eedback control 1 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 proc
9、ess 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 contro
10、l 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
11、. 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 b
12、efore 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 tra
13、nsiently 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 o
14、f 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,
15、and Controlling means Final control part Control object Primary control element Setting part Disturbance Diagram 3 1 Block line diagram of feed back control corollary 2 to get the perfect process model in actual process. Moreover it is difficult to avoid constant deviation, so it is used combined wi
16、th feed back control. 3-3 Sequence control Sequence control processes the fixed process in advance step by step. This sequence control is used in neon signs, vending machines, or electric washing machines. On the other hand, it is needed in the producing process at chemical factory, automobile facto
17、ry, conveyer, automatic warehouse as automation. 3.4 Classification of control methods Production method by continuous process is employed, when scale of process industry gets bigger and larger production amount id requested. You need to make proper use of the control method on some different condit
18、ion of operation. To classfy automatic control system is difficult strictly because their control system has correlation. But general method of cassification will be like below. 4-1 Classification by desired value Automatic control Fixed command control Following control Follow up control Program co
19、ntrol 4-1-1 Fixed command control Most of the controls belong to this control when desired value is constant. 4-1-2 Following command control Servo mechanism composed to follow the change belongs to this control when desired value changes optionally. 4-1-3 Program control It is used for the control
20、in which desired value changes according to fixed time schedule. Normally , it is well used to temp. Control of fever process of metal or batch process at the chemical industry. 4-2. Classification by control method Automatic control Unity control loop Ratio control Cascade control 4-2-1 ratio contr
21、ol It is well used to flow control of 2 fluid when desired value keeps with other fluid (other amount) constantly. You compare and measure if special ratio keeps toward basic fluid (B), then maintain the ratio as the purpose. 4-2-2 Cascade control It is the control method that more than 2 automatic
22、control systems control by output of other control device. In short, control circuit is combined in series. You change the desired value of flow by output of flux adjuster. If you control the desired value of flow control to fix water level in water tank, then you can prevent the influence to the level such as main pressure change of flow itself. The purpose of cascade control method is to absorb disturbance at first control, also to make easy the next step control, and to progress the control on the whole.
