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Why are control systems important?What is an automatic control system?

Basic components and types of control system.How to evaluate a control system?The development of control theory.

What is a control system?examplesControl of Traffic LightsFurnace temperature control systemSwitchHeaterFurnacePowerTemperaturecontrol systemDesired temperaturethermometerfurnacemixeroperatorgasvalveair

Definition of a control systemAn interconnection of components forming a system configuration that will provide adesired system response.

由相互关联的部件按一定的结构构成的系统，能够提供预期的系统响应。

Why are control systems important?(1)控制系统无处不在.(2)提高产量，降低成本.(3)提高精度、可靠性.

(4)能够在许多人不到达的场所发挥作用.

What is an automatic control system?Desired temperaturethermometerfurnacemixeroperatorgasvalveair

Definition of automatic control systemA control system without people involved is called automatic control system.

Temperaturecontrol systemURAmplifierFurnaceUTAmplifierThermocouple PotentiometerMixerMotorGasValveAir

types and Basic components of control systems.Desired output response(Command input)

Actuatingdeviceprocessplant

Output

Controller

Furnace temperature control systemSwitchHeaterFurnacePowerCommand inputSwitch & HeaterFurnace被控对象OutputControllerPlant

Water Level control systemTankValve 1Valve 2Disturbance(valve 2)

LeverValve 1TankTemperature control systemURAmplifierPotentiometerUTAmplifierThermocouple FurnaceMotorGasValveMixerAirAirURCAmplifierUTAmplifierThermocoupleMotorValveMixerFurnaceBlock diagram of control systemsRControllerUPlant被控对象CReference inputFeedback signalComparisonControllerPlantOutput

MeasurementTypes of control systems(1) Open-loop control systems;

(2) Closed-loop control systems(feedback control

systems).

(3) Compound control systems

Open loop controlAn Open-loop control system utilizes an actuating device to control the process directly without using feedback.

开环控制(Open-loop Control)——系统的输出端与输入端之间不存在反馈回路，输出量对系统的控制作用没有影响。

Open-loop Control SystemRControllerUPlant被控对象CMeasurementControllernUPlantCThe output of the open-loop system has no effect upon the

input signal.

There is the need to know an accurate model of individual components.

Features of open-loop control优点：简单，相对来说成本低

缺点：对可能出现的被控量偏离给定值的偏差没有任何修正能力，抗干扰能力差，控制精度不高。

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Closed-loop control systemsA closed-loop control system uses a measurement of output and feedback of the signal to compare it with the desired output(reference or command).Reference inputFeedback signalComparisonControllerPlantOutput

MeasurementFeatures of feedback control systems优点：抗干扰能力强，控制精度高缺点：复杂，有时会产生不稳定。

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Compound Control systemsCombination of open-loop and closed-loop

CompensatorRControllerPlantC—Feedback elementCompensatorRnControllerPlantC—Feedback elementObjectives of controlThe objectives of the control system is to control the outputs in some prescribed manner by the inputs through the elements of control systems.In general,the objectives can be identified with inputs.通常目标规定为系统的输入。

Basic components of control systems被控对象(plant,process)测量元件（sensor）

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可以对被控量进行测量，并转换成能与输入信号进行比较的量纲和数值，也称为反馈元件；实现误差检测；

实现对受控对象的操控，起到功率放大的作用。

比较环节（comparison）

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执行机构（actuator）

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控制律或控制算法（algorithm):

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控制器的核心。

Analysis of automatic control systemStep1确定系统任务；

Step2明确：被控对象、被控量、给定值、测量元件、执行机构和比较元件；Step3 叙述系统工作原理；Step4系统原理方框图。

terms1. 被控对象（plant）

指被控制的设备或过程

2. 控制器（控制装置controller）

除了被控制对象之外的各部分的组合；

3. 控制系统(control system)

受控对象与控制装置构成控制系统。

4. 给定值（期望值、输入量reference/input）

被控制量要求的变化规律( Excitation applied to a control system from an external source).；；

terms5. 被控量(controlled variable)

被控制的物理量；

6. 输出（Output）

The response obtained from a system （通常与被控量一致。）

7.干扰(disturbance)

所有使被控量偏离期望值的因素

8. 反馈（Feedback）

-The output of a system that is returned to modify the input.

Turntable speed controlbatteryTurntableSpeedsettingdcamplifierdc motor TachometerDesiredSpeed(voltage)AmplifierdcmotorTachometerTurntableActualspeedAutomobile direction control systemHow to evaluate a control system?specifications

(1)Stability:stability ,smooth and steady(2)Swiftness :peak time, settling time(3)Accuracy: steady-sate error

History of Automatic Control1769: James Watt’s steam engine and flyball governor.

1868:J.C.Maxwell formulates a mathematical model for a governor control of steam engine.1932: H.Nyquist develops a method for analyzing the stability of systems.

1952:Numerical control developed at MIT for control of machine-tool axes.

1970:State-variable models and optimal control developed. (Liapunov, Minorsky,Pontryagin and Bellman)

1980:Robust control system design widely studied.

1994: feedback control widely used in automobiles. Reliable ,robust systems demanded in manufacturing.

参考书

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Richard C. Dorf, 现代控制系统（第九版），科学出版社

程鹏自动控制原理(第二版),高等教育出版社吴麒自动控制原理，清华大学出版社

Benjamin C. Kuo, Automatic control systems, John Wiley & Sons, Inc.

胡寿松自动控制原理(第四版)，科学出版社

程鹏自动控制原理常见题型解析及模拟题国防工业出版社.