1、1,The Principle of Automatic Control自动控制原理,Lecturers：Prof. Jiang Bin Dr. Lu NingyunCollege of Automation EngineeringNUAA，2008. Autumn,2,NUAA-The Principle of Automatic Control,Chapter 1Introduction to control systems控制系统简介,3,Course Description,This course is concerned with the analysis and design of
2、 control system,Time-domain techniques (root-locus analysis);Frequency-domain techniques (Bode plot, Nyquist stability theory),System modeling, sensitivity and stability,Analysis,Design,Simulation,Analysis and design using MATLAB,4,References,胡寿松主编，自动控制原理，科学出版社K. Ogata，Modern control engineering (现代
3、控制工程,第四版)，有原版翻印本和中译本B.C.Kuo & F. Golnaraghi， Automatic control systems, 8th edition, John Wiley & Sons, 2003 （有原版翻印）,http:/www- control.eng.cam.ac.uk/extras/Virtual_Library/Control_VL.htmlhttp:/www.engin.umich.edu/group/ctm/http:/csd.newcastle.edu.au/,5,Course Evaluation,64 hours, 3 credits:Homework
4、: 5% Class participation: 5%Final exam: 90%,6,Welcome to contact us,Prof. Jiang Bin Email: Tel: 84892301-6041(O); 13611590498(M)Office: A17-604 (明故宫校区）Dr. Lu NingyunEmail: Tel:84892301-6063(O); 13585112514(M)Office: A17-606 (明故宫校区）,7,Chapter 1. Introduction to control systems,WHAT a control system i
5、s?WHY control systems are important?WHAT the basic components of a control system are?Examples of control system applicationsWHY feedback is incorporated into most control systems?Types of control systems,8,Outline,1-1 Basic concepts of control systems1-2 Control system examples 1-3 Classification o
6、f control systems1-4 Basic requirements of a control system1-5 Brief introduction to MATLAB,9,1-1 Basic concepts,10,What is control?,Control：使某些物理量按指定的规律变化（e.g. keep constant, or track a reference signal），以保证生产安全，经济及产品质量等要求的技术手段。,Controlled variable (被控量）：指被测量(measured)并被控制(controlled)到期望值(expected
7、value)的变量Manipulated variable （操纵量）:按照指定规律变化使得被控量达到指定目标的变量(varied by controller so as to affect the controlled variable),Automatic Control：就是应用自动化仪表或控制装置代替人，自动地对机器设备或生产过程进行控制，使之达到预期的状态或性能要求。,e.g. Temperature control system (空调） Speed control system （汽车）,11,Generally speaking, a control system is a s
8、ystem that is used to realize a desired output or objective,What is control system?,Plant (对象）：Maybe a piece of equipment, perhaps just a set of machine parts, functioning together, to perform a particular operation,Process（过程）：A natural or artificial, progressively continuing operation or developme
9、nt toward a particular result,System（系统）：A combination of components that act together and perform a certain objective,Disturbance (扰动）: A signal tends to affect the output of a system,12,controller,Manipulated var.,Open-loop control system,Definition：those systems in which the output has no effect
10、on the control action.,input,Controlled var.,applications,13,Open-loop DC Motor speed-control system,电位器,电压放大器,可控硅功放,直流电动机,扰动,14,Comments on open-loop control system,The output is not measured and compared with the input, no feedbackEach input corresponds a fixed operating condition (电位器0-10v转速0-100
11、0转)The accuracy of the system depends on calibrationIn the presence of disturbance,?,15,Feedback control system,A 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 system,erro
12、r,16,Block diagram,comparison component (comparison point) :its output equals the algebraic sum of all input signals.“+”: plus“-”: minus,lead-out point:Here, the signal is transferred along two separate routes.,The Block representsthe function and name of itscorresponding mode, we dont need to draw
13、detailed structure,and the line guides for the transfer route.,u,17,Feedback control systems exist everywhere,E.g. the human body is highly advanced feedback control system.Body temperature and blood pressure are kept constant by means of physiological feedback.Feedback makes the human body relative
14、ly insensitive to external disturbance. Thus we can survive in a changing environment.,18,In 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 reduce system error,Closed-loop cont
15、rol system,19,Closed-loop DC motor speed control system,20,工作原理,同开环系统相比，该系统由于干扰引起的转速误差要小得多。,21,正反馈不能用于控制系统,用途振荡器（正弦信号发生器）,22,Open-loop control systems Simple structure, low cost Easy to regulate Low accuracy and resistance of disturbanceClosed-loop control systems Ability to correct error High accur
16、acy and resistance of disturbance Complex structure, high cost Critical for selecting parameters (may cause stability problem)Open-loopClosed-loopComposite control system,Comparison between open-loop and closed-loop systems,23,1-2 More examples of feedback control system,24,Flush toilet (冲水马桶）,Level
17、,Water Tank,Float,Piston,Plant:Input:Output:Expected value: Sensor:Controller:Actuator:,Plant,Controller,Actuator,Sensor,water tank,water flow,water level,float,lever,piston,25,Plane-autopilot（自动驾驶）,26,俯仰角控制系统方块图,27,Other examples,胡寿松教材pages7-9Ogata教材pages3-6Kuo教材pages2-6,28,Why control systems are
18、important?,In other words, why we (engineer) 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 des
19、igners extra degrees of freedomControl has beautiful theoretical results and really neat devices,29,1-3 Classification of control systems,30,According to structure,Open-loop control systemsClosed-loop control systemsComposite control systems,31,According to type of reference input,Constant-value con
20、trol system （常值控制系统） 输入量是恒定的常值， 在各种扰动作用下都能使输出量保持在恒定希望值附近， 如恒温、水位、恒压控制系统Servo/tracking(侍服/跟踪） control system （随动控制系统） 输入量是事先不知道的任意时间函数， 使输出量迅速而准确地跟随输入量的变化而变化， 比如：飞机和舰船的操舵系统，雷达自动跟踪系统。Programming control system （程序控制系统） 输入量按照给定的程序变化， 使输出量按预先给定的程序指令而动作， 最典型的就是数控车床和机器人控制系统。,32,According to system charact
21、er,Linear system principle of superposition applies （齐次叠加原理） described by linear differential equation（线性微分方程）Nonlinear systemdescribed by nonlinear differential equation （非线性微分方程）,33,According to system character with respect to time,Time-invariant systemThe parameters of a control system are stati
22、onary with respect to timeTime-varying systemSystem contain 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,34,According to form of the signals,Continuous-data control system （连续控制系统）The signals are
23、all functions of continuous time variable t （信号是时间的连续值）Discrete-data control system The signals are in the form of either a pulse train or a digital code （信号是脉冲序列或数字编码）sample-data and digital control system,35,1-4 Basic requirements for control systems,胡寿松教材，p13,36,Two-fold tasks:how the system resp
24、onses to the external input? how the system resists disturbances?,The system is expected to be affected ONLY by control input, NOT by disturbance.,37,Typical external signals,为了能对不同的控制系统的性能用统一的标准来恒量，通常需要选择几种典型的外作用,Rules of selection（1）Easy to generate（2）Frequently encountered（3）Simple mathematical e
25、xpression。,38,Step-function input （阶跃输入）,在t=0时刻出现幅值为R的跳变， R=1时的阶跃函数叫unit step function （单位阶跃函数），denoted by 1(t) 。,最不利的外作用, 常用阶跃函数作为评价系统动态性能的典型外作用, 所以阶跃函数在自动控制系统的分析中起着特别重要的作用。,例如飞机飞行中遇到的常值阵风扰动。,39,例如雷达-高射炮防空系统，当雷达跟踪的目标以恒定速率飞行时， 便可视为该系统工作于斜坡函数作用之下。,Ramp-function input （斜坡输入）,在t=0时刻开始，以恒定速率R随时间变化,40,Pu
26、lse/Impulse function input （脉冲输入）,Pulse function 脉动函数,impulse function冲激函数,？,Note: （1）The above impulse function does not exist in reality, it is just mathematical definition. When A=1时，it is called unit impulse function，denoted by (t); (2) 脉冲函数很重要，任意一个外作用的输出响应可分解为不同时刻系列脉冲输入之和,41,Sinusoid function i
27、nput （正弦输入）,A Amplitudew=2f angular frequency,If the initial phase is non-zero，then r(t) can be described by,例如海浪对舰船的颠簸，电源及机械振动的噪声可视为正弦扰动。系统在正弦函数作用下的响应，即frequency characteristic，是自动控制理论中研究系统性能的重要依据。,42,Basic requirements for system performance,Since step input function jumps from zero to a constant
28、value, it is always chosen as a typical input signal to investigate system performance.,System performance about step input response can be summarized as: 1. Stability 稳定性 2. Accuracy 准确性 3. Quickness快速性,43,A control system without disturbance,当输入信号突然发生跳变时，这时输出量还处在原有的平衡状态，这样就出现了偏差，这个偏差控制输出量达到新的平衡，这就
29、是一个 regulation process （调节过程）。,44,Response curve1,Response curve2,理想的调节过程是：出现偏差后，执行机构突然动作，使输出量立即达到新的平衡状态，调节过程瞬时完成，实际上这是不可能的，为什么呢？,系统从原平衡状态到达新的平衡状态都要经历一个过渡过程，过渡过程的曲线形状随系统的不同而有所差异.,物理系统均是惯性系统,Curve 1 monotonously increases to the steady-state value.Curve 2 (decaying) oscillates to the steady-state val
30、ue.,stable,45,The whole regulation process can be divided into two stages:,Steady-state process（稳态过程） reflects steady-state character ，即输出量稳定在新的平衡状态，并保持不变。,Transient process (瞬态过程） reflects dynamic character（动态特性），即输出量处于激烈变化之中。,Quickness（快速性）,Stability（稳定性）,Accuracy(准确性）,46,Definitions,Stability：ref
31、ers to ability of a system to 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),47
32、,Note,For a control system, the above three performance indices (stability, quickness, accuracy) are sometimes contradictory. In design of a practical control system, we always need to make compromise.,48,1-5 MATLAB,49,MATLAB,MATLAB是具有很强数值计算、符号运算、仿真和图形显示功能的计算分析软件。它具有编程方便、简单易学等诸多优点，同时提供了大量的内置函数和外置工具箱
33、，被广泛应用于数学计算、工程应用和社会科学研究的诸多领域。,50,Simulation using MATLAB,1 请同学们自学MATLAB基础知识2. 本课程部分章节中将给出MATLAB常用函数以及程序实例，辅助学习课程相关内容,51,1-6 Additional reading materials short history of control,52,Keeping accurate track of time Water clock (Ktesibios, 270 BC),Short history of control,53,Short history of control,Ind
34、ustrial revolutionTemperature regulator for furnace (Drebbel, 1624)Float regulator for steam boiler (Brindley, 1758)Pressure regulator for steam engine (Papin, 1707),54,Short history of control,Birth of mathematical control theory Differential equations for telescope pointing (Airy, 1840)Stability t
35、heory for Watts flyball governor (Maxwell,1868)System theory of organic mechanism (Whitehead, 1925),55,Short history of control,Mass communication Frequency domain analysis for communication systems (1920s, Bell Telephone Laboratory),56,Short history of control,World Wars and classical controlShip c
36、ontrol (Minorsky, 1922)Weapons development and gun pointing (Hazen,1934)MIT radiation laboratory (1940s)Stochastic analysis (Wiener, 1942),57,Short history of control,Space/computer age and modern controlTime-domain design for nonlinear systemsOptimal control and estimation theoryNonlinear control t
37、heoryComputers in controls design and implementation,58,Short history of control,Union of modern and classical control Advanced control theories,59,Suggestions on the course study,Pay enough attention control theory is very interesting, very useful, but sometimes, very difficultPractice, practice, and practice,60,End of Chapter 1,Thank you all!,
