线性系统的根轨迹分析法 (1).pdf

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1、1Chapter1 Introduction1.1 Basic Concept of Automatic Control1.2 Open-loop Control System and Closed-loopControl System1.3 Classification of Automatic Control Systems1.4 Basic Requirements for Control Systems2Definition：Open-loop control systemA system where controlled object(i.e.,output)takes nodire

2、ct effect on the control action.That is,a systemthat does not feed back the output to the input end.3A system does not feed back the output to the input end.guaunguauninputControlvariableOutput(controlled variable)Controlled objectOpen-loop control system：Motor speed control systemchangeControl proc

3、ess:guaun4The major defect:Once the input is determined,the speed is defined.This disturbance will cause the speed to deviate from the expected value.guaunThe aim of control:to maintain the motor speed at an expected value.Vulnerability to disturbance5How to overcome the defect of an open-loop contr

4、ol system and to improve the anti-disturbance capability of the system?uf6Definition：load+nvoltage amplifierpoweramplifierue+tachogeneratorugufuaMClosed-loop control systemA system that has not only positive effect but also feedback connectionbetween controller and controlled object.That is,a system

5、 in which theoutput has a direct effect on the control variable.7nuuae fgfueuuWhether a closed-loop control system can improve anti-disturbance capability or not?Counteract the reduction of speed caused by the increased load.n8By feeding the detected controlled variable back to the input end,and com

6、paring it with the inputvariable,the system deviation is obtained and it is employed to generate the control action,thusmaking the controlled variable get close to the desired value.Finally the deviation may be reducedor eliminated.This is the working principle of a feedback control system.The worki

7、ng principle of a closed-loop control system：Deviation control systemFeedback control systemClosed-loop control systemAutomaticcontrolsystem9Composition of a closed-loop control systemTo provide a value for the system input according to the expected value of the controlled variable.To detect the con

8、trolled variable and to feed it back to theinput end of the system.to change the controlled variableto a quantity of the same dimension as the input signal,such that they can be compared.10It refers to the physical quantity in thecontrolled object that is required to changeaccording to a predetermin

9、ed rule.It isalso called controlled variable or output.It is the difference between inputsignal and feedback signal.We alsosimply call it deviation.It measuresthe deviation at the input end.It represents the controlled variable fedback to the system input end.It refers to the differencebetween the desired valueand the actual value of thecontrolled variable of thesystem.We also simply callit error.+11SummaryOpen-loop control systemClosed-loop control systemComposition of a closed-loop control system