自動控制原理雙語chapter

1、The Principle of Automatic Control自動控制原理Lecturers：Prof. Jiang Bin Dr. Lu NingyunCollege of Automation EngineeringNUAA，2008. Autumn1NUAA-The Principle of Automatic Control Chapter 1Introduction to control systems控制系統(tǒng)簡介2Course DescriptionThis course is concerned with the analysis and design of control

2、 systemTime-domain techniques (root-locus analysis);Frequency-domain techniques (Bode plot, Nyquist stability theory)System modeling, sensitivity and stabilityAnalysisDesignSimulationAnalysis and design using MATLAB3References胡壽松主編，自動控制原理，科學出版社K. Ogata，Modern control engineering (現(xiàn)代控制工程,第四版)，有原版翻印本和

3、中譯本B.C.Kuo & F. Golnaraghi， Automatic control systems, 8th edition, John Wiley & Sons, 2003 （有原版翻印） control.eng.cam.ac.uk/extras/Virtual_Library/Control_VL.html4Course Evaluation64 hours, 3 credits:Homework: 5% Class participation: 5%Final exam: 90%5Welcome to contact us Prof. Jiang Bin Email: Tel:

4、84892301-6041(O); (M)Office: A17-604 (明故宮校區(qū)）Dr. Lu NingyunEmail: Tel:84892301-6063(O); (M)Office: A17-606 (明故宮校區(qū)）6Chapter 1. Introduction to control systemsWHAT a control system is?WHY control systems are important?WHAT the basic components of a control system are?Examples of control system applicat

5、ionsWHY feedback is incorporated into most control systems?Types of control systems7Outline1-1 Basic concepts of control systems1-2 Control system examples 1-3 Classification of control systems1-4 Basic requirements of a control system1-5 Brief introduction to MATLAB81-1 Basic concepts 9What is cont

6、rol? Control：使某些物理量按指定的規(guī)律變化（e.g. keep constant, or track a reference signal），以保證生產(chǎn)安全，經(jīng)濟及產(chǎn)品質量等要求的技術手段。Controlled variable (被控量）：指被測量(measured)并被控制(controlled)到期望值(expected value)的變量Manipulated variable （操縱量）:按照指定規(guī)律變化使得被控量達到指定目標的變量(varied by controller so as to affect the controlled variable) Automati

7、c Control：就是應用自動化儀表或控制裝置代替人，自動地對機器設備或生產(chǎn)過程進行控制，使之達到預期的狀態(tài)或性能要求。e.g. Temperature control system (空調） Speed control system （汽車）10Generally speaking, a control system is a system that is used to realize a desired output or objectiveWhat is control system? Plant (對象）：Maybe a piece of equipment, perhaps ju

8、st a set of machine parts, functioning together, to perform a particular operation Process（過程）：A natural or artificial, progressively continuing operation or development toward a particular result System（系統(tǒng)）：A combination of components that act together and perform a certain objective Disturbance (擾

9、動）: A signal tends to affect the output of a system11controllerManipulated var.Open-loop control systemDefinition：those systems in which the output has no effect on the control action.inputplantdisturbanceControlled var.applications12Open-loop DC Motor speed-control system電位器（產(chǎn)生給定電壓ur）假定010V轉速01000轉

10、電位器電壓放大器可控硅功放直流電動機n擾動Purukua13Comments on open-loop control systemThe output is not measured and compared with the input, no feedbackEach input corresponds a fixed operating condition (電位器0-10v轉速0-1000轉)The accuracy of the system depends on calibrationIn the presence of disturbance?14Feedback contro

11、l systemA system that maintains a prescribed relationship between the output and the reference input bycomparing and using the difference (error) as a means of control feedback control systemRef inputcontrollerManipulated var.plantdisturbanceOutputerrorsensor15Block diagramControllerActuatorPlantSen

12、sor-rExpected valuee ErrorDisturbanceControlledvariableny comparison component (comparison point) :its output equals the algebraic sum of all input signals.“+”: plus“-”: minuslead-out point:Here, the signal is transferred along two separate routes.The Block representsthe function and name of itscorr

13、esponding mode, we dont need to draw detailed structure,and the line guides for the transfer route.u16Feedback control systems exist everywhereE.g. the human body is highly advanced feedback control system.Body temperature and blood pressure are kept constant by means of physiological feedback.Feedb

14、ack makes the human body relatively insensitive to external disturbance. Thus we can survive in a changing environment.17In practice, feedback control system and closed-loop control system are used interchangeablyClosed-loop control always implies the use of feedback control action in order to reduc

15、e system errorClosed-loop control system18Closed-loop DC motor speed control system19電位器電壓放大器可控硅放大器直流電動機測速機Purubuk-n擾動ua工作原理引入測速發(fā)電機，這時電壓放大器的輸入 ，如果外來的電網(wǎng)電壓波動使電機的轉速n ，則由測速發(fā)電機確定的則 則uk ，ua 則n ，消除了偏差，控制轉速穩(wěn)定。負反饋。同開環(huán)系統(tǒng)相比，該系統(tǒng)由于干擾引起的轉速誤差要小得多。20電位器電壓放大器可控硅放大器直流電動機測速機Purubukn擾動ua正反饋不能用于控制系統(tǒng)用途振蕩器（正弦信號發(fā)生器）如果極性接錯，

16、這時電壓放大器的輸入 ，如果外來的電網(wǎng)電壓波動使電機的轉速n ，則由測速發(fā)電機確定的則 則uk ，ua 則n ，則轉速越來越大，電動機損壞，失去控制。正反饋。21Open-loop control systems Simple structure, low cost Easy to regulate Low accuracy and resistance of disturbanceClosed-loop control systems Ability to correct error High accuracy and resistance of disturbance Complex st

17、ructure, high cost Critical for selecting parameters (may cause stability problem)Open-loopClosed-loopComposite control systemComparison between open-loop and closed-loop systems221-2 More examples of feedback control system23Flush toilet (沖水馬桶）LevelWater TankFloatPistonPlant:Input:Output:Expected v

18、alue: Sensor:Controller:Actuator:PlantControllerActuatorSensorwater tankwater flowwater levelfloatleverpiston24Plane-autopilot（自動駕駛）25給定裝置放大器舵機飛機 反饋 電位器 垂直 陀螺儀0c擾動俯仰角控制系統(tǒng)方塊圖26Other examples胡壽松教材pages7-9Ogata教材pages3-6Kuo教材pages2-627Why control systems are important?In other words, why we (engineer)

19、should know control?Control is an essential element of almost all engineering systemsIt happens very often that systems perform poorly because they are designed from purely static analysis, with no consideration of dynamics and controlControl can give designers extra degrees of freedomControl has be

20、autiful theoretical results and really neat devices281-3 Classification of control systems29According to structureOpen-loop control systemsClosed-loop control systemsComposite control systems30According to type of reference inputConstant-value control system （常值控制系統(tǒng)） 輸入量是恒定的常值， 在各種擾動作用下都能使輸出量保持在恒定希望

21、值附近， 如恒溫、水位、恒壓控制系統(tǒng)Servo/tracking(侍服/跟蹤） control system （隨動控制系統(tǒng)） 輸入量是事先不知道的任意時間函數(shù)， 使輸出量迅速而準確地跟隨輸入量的變化而變化， 比如：飛機和艦船的操舵系統(tǒng)，雷達自動跟蹤系統(tǒng)。Programming control system （程序控制系統(tǒng)） 輸入量按照給定的程序變化， 使輸出量按預先給定的程序指令而動作， 最典型的就是數(shù)控車床和機器人控制系統(tǒng)。31According to system characterLinear system principle of superposition applies （齊次疊

22、加原理） described by linear differential equation（線性微分方程）Nonlinear systemdescribed by nonlinear differential equation （非線性微分方程）32According to system character with respect to timeTime-invariant systemThe parameters of a control system are stationary with respect to timeTime-varying systemSystem contain

23、 elements that drift or vary with time E.g. Guided-missile control system, time-varying mass results in time-varying parameters of the control system 33According to form of the signalsContinuous-data control system （連續(xù)控制系統(tǒng)）The signals are all functions of continuous time variable t （信號是時間的連續(xù)值）Discre

24、te-data control system The signals are in the form of either a pulse train or a digital code （信號是脈沖序列或數(shù)字編碼）sample-data and digital control system341-4 Basic requirements for control systems胡壽松教材，p1335Two-fold tasks:how the system responses to the external input? how the system resists disturbances?T

25、he system is expected to be affected ONLY by control input, NOT by disturbance.36Typical external signals為了能對不同的控制系統(tǒng)的性能用統(tǒng)一的標準來恒量，通常需要選擇幾種典型的外作用Rules of selection（1）Easy to generate（2）Frequently encountered（3）Simple mathematical expression。37Step-function input （階躍輸入）在t=0時刻出現(xiàn)幅值為R的跳變， R=1時的階躍函數(shù)叫unit s

26、tep function （單位階躍函數(shù)），denoted by 1(t) 。最不利的外作用, 常用階躍函數(shù)作為評價系統(tǒng)動態(tài)性能的典型外作用, 所以階躍函數(shù)在自動控制系統(tǒng)的分析中起著特別重要的作用。例如飛機飛行中遇到的常值陣風擾動。38例如雷達-高射炮防空系統(tǒng)，當雷達跟蹤的目標以恒定速率飛行時， 便可視為該系統(tǒng)工作于斜坡函數(shù)作用之下。Ramp-function input （斜坡輸入）在t=0時刻開始，以恒定速率R隨時間變化0tr(t)39t0Pulse/Impulse function input （脈沖輸入）r(t)0tPulse function 脈動函數(shù)impulse function

27、沖激函數(shù)？Note: （1）The above impulse function does not exist in reality, it is just mathematical definition. When A=1時，it is called unit impulse function，denoted by (t); (2) 脈沖函數(shù)很重要，任意一個外作用的輸出響應可分解為不同時刻系列脈沖輸入之和40Sinusoid function input （正弦輸入）A Amplitudew=2f angular frequencyIf the initial phase is non-ze

28、ro，then r(t) can be described by例如海浪對艦船的顛簸，電源及機械振動的噪聲可視為正弦擾動。系統(tǒng)在正弦函數(shù)作用下的響應，即frequency characteristic，是自動控制理論中研究系統(tǒng)性能的重要依據(jù)。41Basic requirements for system performanceSince step input function jumps from zero to a constant value, it is always chosen as a typical input signal to investigate system perfo

29、rmance.System performance about step input response can be summarized as: 1. Stability 穩(wěn)定性 2. Accuracy 準確性 3. Quickness快速性42控制器執(zhí)行機構被控對象輸入信號給定值偏差-測量傳感元件輸出量A control system without disturbance當輸入信號突然發(fā)生跳變時，這時輸出量還處在原有的平衡狀態(tài)，這樣就出現(xiàn)了偏差，這個偏差控制輸出量達到新的平衡，這就是一個 regulation process （調節(jié)過程）。43t01Input r(t)t01Output

30、 c(t)Response curve1Response curve2理想的調節(jié)過程是：出現(xiàn)偏差后，執(zhí)行機構突然動作，使輸出量立即達到新的平衡狀態(tài)，調節(jié)過程瞬時完成，實際上這是不可能的，為什么呢？系統(tǒng)從原平衡狀態(tài)到達新的平衡狀態(tài)都要經(jīng)歷一個過渡過程，過渡過程的曲線形狀隨系統(tǒng)的不同而有所差異. 物理系統(tǒng)均是慣性系統(tǒng)Curve 1 monotonously increases to the steady-state value.Curve 2 (decaying) oscillates to the steady-state value.stable44t01Output c(t)The whol

31、e regulation process can be divided into two stages: Steady-state process（穩(wěn)態(tài)過程） reflects steady-state character ，即輸出量穩(wěn)定在新的平衡狀態(tài)，并保持不變。Transient process (瞬態(tài)過程） reflects dynamic character（動態(tài)特性），即輸出量處于激烈變化之中。Quickness（快速性）Stability（穩(wěn)定性）Accuracy(準確性）45DefinitionsStability：refers to ability of a system to

32、 recover equilibrium, i.e., convergence of transient process (converge)Quickness: refers to duration of transient process (quick)Accuracy：refers to the size of steady-state error when the transient process ends.（small) (Steady-state error=desired output actual output)46NoteFor a control system, the

33、above three performance indices (stability, quickness, accuracy) are sometimes contradictory. In design of a practical control system, we always need to make compromise.471-5 MATLAB48MATLABMATLAB是具有很強數(shù)值計算、符號運算、仿真和圖形顯示功能的計算分析軟件。它具有編程方便、簡單易學等諸多優(yōu)點，同時提供了大量的內置函數(shù)和外置工具箱，被廣泛應用于數(shù)學計算、工程應用和社會科學研究的諸多領域。 49Simul

34、ation using MATLAB1 請同學們自學MATLAB基礎知識2. 本課程部分章節(jié)中將給出MATLAB常用函數(shù)以及程序實例，輔助學習課程相關內容501-6 Additional reading materials short history of control51Keeping accurate track of time Water clock (Ktesibios, 270 BC)Short history of control52Short history of controlIndustrial revolutionTemperature regulator for furnace (Drebbel, 1624)Float regulator for st