2018/9/8,1,外文版自动控制理论 多媒体课件制作,2018/9/8,2,Automatic Control System,1. Automatic Control System 1.1 Introduction 1.2 An example 1.3 Types of control system 2. Mathematical Foundation 2.1 The transfer function concept 2.2 The block diagram. 2.3 Signal flow graphs2.4 Construction of signal flow graphs 2.5 General input-output gain transfer function,2018/9/8,3,Automatic Control System,3. Time-Domain Analysis Of Control System 3.1 Introduction 3.2 Typical test signals for time response of control systems 3.3 First Order Systems 3.4 Performance of a Second-Order System 3.5 Concept of Stability4. The Root Locus Techniques4.1 Introduction4.2 Root Locus Concept,2018/9/8,4,Automatic Control System,4.3 The Root Locus Construction Procedure for General System 4.4 The zero-angle (negative) root locus 5. Frequency-Domain Analysis of Control System5.1 Frequency Response 5.2 Bode Diagrams 5.3 Bode Stability Criteria 5.4 The Nyquist Stability Criterion,2018/9/8,5,Automatic Control System,6. Control system design 6.1 Introduction6.2 Cascade Lead Compensation 6.3 Properties of the Cascade Lead Compensator 6.4 Parameter Design by the Root Locus Method,2018/9/8,6,1.Introduction,2018/9/8,7,1.1 Introduction,In recent years, automatic control systems have assumed an increasingly important role in the development and advancement of modern civilization and technology. Domestically, automatic controls in heating and air conditioning systems. Industrially, automatic control systems are found in numerous applications ,such as quality control of manufactured products ,machine tool control ,modern space technology and weapon systems .Even such problems as inventory control ,social and economic systems control ,and environment and hydrological systems control may be approached from the theory of automatic control.,2018/9/8,8,1.2 An example,The human being is a feedback control system ,let us consider that the objective is to reach for an object on a desk ,As one is reaching for the object ,the brain sends out a signal to the arm to perform the task .The eyes serve as a sencing device which feed back continuously the position of the hand .The distance between the hand and the object is the error ,which is eventually brought to zero as the hand reaches the object .This is a typical example of closed-loop control.,2018/9/8,9,1.3 Types of control system,Control systems are classified in terms that described either the system itself or its variables. These descriptive terms are mainly of the either-or form. 1 An open-loop system is shown in Fig1-1-1a and is characterized by the input entering directly into the control elements unaffected by the output ;the output is related to the input solely by the characteristics of the plant and control elements .In the closed-loop system of Fig.1-1-2b,however the input is modified by the actual output before entering the control elements.,2018/9/8,10,2018/9/8,11,2 Lumped parameter system are those for which the physical characteristics are assumed to be concentrated in one or more “lumps” and thus independent of any special distribution .For example springs are massless and electrical leads resistanceless. 3 A stationary or time-invariant system is one whose parameters do not vary with time. 4 A single-variable system is defined as one with only one output for one reference or command input (SISO) 5 A multivariable (MIMO)system has any number of inputs and outputs. 6 A continuous-variable system is one for which all the system variables are continuous functions of time .,2018/9/8,12,2.Mathematical Foundation,2018/9/8,13,2.1 The transfer function concept,From the mathematical standpoint, algebraic and differential or difference equations can be used to describe the dynamic behavior of a system .In systems theory, the block diagram is often used to portray system of all types .For linear systems, transfer functions and signal flow graphs are valuable tools for analysis as well as for designIf the input-output relationship of the linear system of Fig.1-2-1 is known, the characteristics of the system itself are also known. The transfer function of a system is the ratio of the transformed output to the transformed input.,2018/9/8,14,Finger 1-2-1 input-output relationships (a) general (b) transfer function,(2-1),2018/9/8,15,Summarizing over the properties of a function we state: 1.A transfer function is defined only for a linear system, and strictly, only for time-invariant system. 2.A transfer function between an input variable and output variable of a system is defined as the ratio of the Lap lace transform of the output to the input. 3.All initial conditions of the system are assumed to zero. 4.A transfer function is independent of input excitation.,2018/9/8,16,2.2 The block diagram.,Figure 2-3-1 shows the block diagram of a linear feedback control system. The following terminology often used in control systems is defined with preference to the block diagram. R(s), r (t)=reference input. C(s), c (t)=output signal (controlled variable). B(s), b (t)=feedback signal. E(s), e (t)=R(s)-C(s)=error signal. G(s)=C(s)/c(s)=open-loop transfer function or forward-path transfer function. M(s)=C(s)/R(s)=closed-loop transfer function H(s)=feedback-path transfer function. G(s)H(s)=loop transfer function.,