线性控制系统课件Module1(免费)

23:55ຫໍສະໝຸດ Baidu
How to realize automatic control
Temperature sensors measure the water temperature and send it to the brain; The brain compares the water temperature with the desired temperature, and drives a control signal output by hand. The hand manipulates the mixer valve to achieve a desired temperature.
Assume that x is proportional to the error. Kg is the constant proportionality with units of millimeter seconds per radian, The governor performs the function of comparing ωg with the set speed ωd and represents the error in terms of a displacement of collar C that will be called x
Electrohydraulic servovalve (电液伺服阀门) Hydraulic actuator (液压执行器)
23:55 Hydraulic cylinder (液压缸)
Electrohydraulic servovalve: -Input: electrical signal, and it can change the magnetic field around the chamber.
Module 1: Introduction to Feedback Control
• Why we need automatic control ? • How to realize automatic control ? • Nature of automatic control ? • Tasks of control system analysis ?
Plant: motor and load Value setting device: input potentiometer Value feedback device: output potentiometer Differencing junction: differencing amplifier note: input and output potentiometer have the same characteristics
vout =
R4 R vp − 1 vn R3 R2
R4 R1 ka = = R3 R2
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vout = Ka (vp − vn )
The Plant includes motor and load. The function of the gearbox between motor and load is to overcome the load inertia. input: the voltage provided by the operational amplifier. output: angular position of the load. The motor Input: the voltage output: the speed
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How to realize automatic control
If the temperatures and pressures of hot and cold water are unchanged, the water temperature depends on the angle of valve If the temperatures and pressures of hot and cold water are changed, what will happen?
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Needs for the practical activities
• Human can not work day after night with the tremendous effects. • The efficiency of the productivity is always limited. • Material wealth is far from the needs of civilization society.
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How to realize automatic control
Automation refers to the unmanned machines or devices operate automatically in accordance with the preset procedure or directives. Question: • What kinds of structure can realize “unmanned” ? • Is there any rules can be followed?
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Why We Need Automation
• Inevitable results to understand and change the world. • inevitable requirements to improve the social productivity and efficiency. • inevitable choices for the energy conservation and the ensure of production quality. • Inevitable methods to improve the working condition and living quality. Automation will greatly accelerate the innovation of social structure and process of social informationization
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plant: the steam turbine
Input: the steam flow rate Q Output: the speed
ω
Feedback path: Gearbox
speed of governor: ωg = Nω N is gearbox ratio
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Governor block diagram:
The Principle of Automatic Control 自动控制原理
章 鹏
重庆大学光电工程学院
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• 教材 ：
Linear Control Systems Engineering Author: Morris Driels 《线性控制系统工程》
【出 版 社】清华大学出版社
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Sample Problem1.2 : Analyze the system in Fig.SP1.2.1, which uses a direct-current (DC) motor to position a load according to the angular position set by the input potentiometer.
Linkage block diagram:
Assume that rod P is connected halfway between C and the pivot. Inlet valve displacement y=x/2
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• Some transfer functions are easy to determine while others
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“Unmanned” Temperature control system
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Generalized feedback control system
Plant: the major component being controlled, it’s transfer function is fixed Controller: the control device designed by engineer Feedback path: the output variable fed back to be compared with desired value Forward path:
are not. Some may be simple constants while others are nonlinear function.
• In many cases there are more ‘boxes’ , and it is difficult to
allocate elements to the plant or the controller. It will be shown that this categorization is in fact not important, but deciding if an element is part of the forward path or feedback path may be of more significance. • Transfer functions, because they change one variable into another, usually have dimensions. • The differencing junction can only subtract two variables of same dimensions, producing an error variable of same dimension.
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Transducer:
Sample Problem1.1 : a speed control system originally developed by James Watt in 1769, for reciprocating(往复式) steam engines.
Inlet valve: 进气阀 Watt’s fly-ball governor: 飞球调节器 Shaft: 轴 Pin-jointed: 连接销 Centripetal force: 向心力 Equilibrium: 平衡
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Potentiometer is characterized by a coefficient, Kp with units of volts per radian. Wiper: 电位器抽头
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The differencing junction compares the voltage representing the demanded position with voltage representing the achieved position. this junction can be constructed using an operational amplifier and resistors
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Flap Angular Position Servo Control System (襟翼角位移伺服控制)
Purpose: To position the flap to the angular position set by the pilot potentiometer.
The difference from SP1.2 is that the system comprising electrical and hydraulic components