B Lecture1 Introduction Automatic control System
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Transcript of B Lecture1 Introduction Automatic control System
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Automatic Control Theory
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Please Note:
Two broad categories of control:
Manual Control
Automatic Control --- A machine(or system) works by machine-self, not by manual operation.
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Please Note:
This course introduces analyzing and designing of automatic control systems .
Topics include the properties and advantages of automatic control systems, time-domain and frequency-domain performance measures, stability and degree of stability, the Root locus method and frequency-domain design.
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Please Note:
Matlab will be required extensively. If you have not used it before,then start practicing. We suggest that everyone become familiar with the use of MATLAB
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Reasons for Using Automatic Control:
Reduce workload
Perform tasks people cant
Reduce the effects of disturbances
Reduce the effects of plant variations
Stabilize an unstable system
Improve the performance of a system (time response)
Improve the linearity of the system
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Many vehicles (spacecraft, aircraft, rockets) and aerospace processes (propulsion) need to be controlled just to function.
Example: the F-117 does not even fly without computer control, and the X-29 is unstable.
There are also many stable systems that simply require better performance in some sense (e.g., faster, less oscillatory), and we can use control to modify this behavior.
Reasons for Using Automatic Control:
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Examples of Automatic Control Systems
* Operating principle
* Feedback control A water-level control system
Example #1
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x2
x3
Signal(variable)
xxxComponents(devices)
+-
+x1 eAdders (comparison)
e=x1+x3-x2
x
The block diagram description for a control system : Convenience
Examples of Automatic Control Systems
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amplifier Motor Gearing Valve
Actuator
Water
container
Process controller
Float
measurement
(Sensor)
Error
Feedback
signal
resistance comparator
Desired
water level
Input
Actual
water level
Output
Examples of Automatic Control Systems
Example #1
The block diagram discription of a water-level control system
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Examples of Automatic Control Systems
A DC-Motor control system
Example #2
* Operating principle
* Feedback control
M
M
+
-
+
regulator
trigger
rectifier
DCmotor
techometer
load
e
Uf (Feedback)
ur
Fig. 1.4
ua
Uk=k(ur-uf)
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Examples of Automatic Control Systems
The block diagram discription of the DC-motor control system
Desired rotate speed n
Regulator Trigger Rectifier DCmotor
Techometer
Actuator
Processcontroller
measurement (Sensor)
comparator
Actual rotate speed n
Error
Feedback signal
Referenceinput ur
Output n
Fig. 1.9
auk ua
uf
e
Example #2
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Identify the control goal:
Identify the variables to control:
Position the reader head to read the date stored on a track on the disk.
The position of the read head.
Examples of Automatic Control Systems
Actuator
motor
Arm
Spindle Track a
Track b
Head slider
Rotation
of arm Dis
k
A disk drive read system
Example #3
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It is obvious :
a closed loop system
not a open loop system
Control
device
Actuator
motor
Read
arm
sensor
Desired
head
position
error Actual
head
position
Block diagram of a disk drive read system
Examples of Automatic Control Systems
Actuator
motor
Arm
Spindle Track a
Track b
Head slider
Rotation
of arm Dis
k Example #3
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Automatic control systems can be designed to hold an output steady or to track a desired reference signal.
Regulator: keep output at a steady, known value.
Tracking or servo system: Make output track a reference system.
Fundamental Structure of Control Systems
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We can further categorize control systems as either open-loop or closed-loop.
Closed-loop controllers(or feedback controllers) compute the control action based on the measured output of the system being controlled.
Fundamental Structure of Control Systems
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Open loop control systems
Features: Only there is a forward action from the input to the output.
Fundamental Structure of Control Systems
Controller Actuator Process
Disturbance(Noise)
Input r(t)
Reference desired output
Output c(t)(actual output)
Controlsignal
Actuatingsignal
uk uact
Fig. 1.10
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Closed loop (feedback) control systems
Features:
1) measuring the output (controlled variable) . 2) Feedback.
not only there is a forward action , also a backward action between the output and the input (measuring the output and comparing it with the input).
Fundamental Structure of Control Systems
Controller Actuator Process
Disturbance(Noise)
Input r(t)
Reference desired output
Output c(t)(actual output)
Controlsignal
Actuatingsignal
uk uact
Fig. 1.11
measurementFeedback signal b(t)
+-
(+)
e(t)=r(t)-b(t)
Notes: 1) Positive feedback; 2) Negative feedbackFeedback.
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Please Note:
Typically think of closed-loop control
so we would analyze the closed-loop dynamics.
Note that a typical control system includes the sensors, actuators, and the control law.
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Feedback Control System
Comparison between the reference input and the feedback signal results in an actuating signal that is the difference between these two quantities.
The actuating signal acts to maintain the output at the desired value.
This system is called a closed-loop control system.
Measurement
Dynamic process
Disturbance
Controller Output
Sensor
Actuator Reference
Control
signal
Sensor noise
Plant
Components in a typical control system
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Measurement
Dynamic process
Disturbance
Controller
Output
Sensor
Actuator
Reference Control
signal
Sensor noise
Plant
Typically, we are interested in cases where the plant and
controller are linear and time-invariant, or can be modeled
as such. Then we can represent components as transfer
functions.(We will learn this later)
Feedback Control of Dynamic System
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types of control systems
1) linear systems versus Nonlinear systems.
2) Time-invariant systems vs. Time-varying systems.
3) Continuous systems vs. Discrete (data) systems.
4) Constant input modulation vs. Servo control systems.
Basic performance requirements of control systems
1) Stability. 2) Rapidness (instantaneous characteristic).
3) Accuracy (steady state performance).
Please Note:
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Stability
Please Note:
0 1 2 3 4 5 6-0.5
0
0.5
1
1.5
2
2.5
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Rapidness (instantaneous characteristic)
Please Note:
0 1 2 3 4 5 6 7 80
0.2
0.4
0.6
0.8
1
1.2
1.4
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Accuracy (steady state performance).
Please Note:
0 1 2 3 4 5 6 7 80
0.2
0.4
0.6
0.8
1
1.2
1.4
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Main Content
1. Introduction to Control Systems
2. Mathematical Models of Systems
3. Time-Domain Analysis of Control Systems
4. The Root Locus Analysis
5. Frequency-Domain Analysis
6. Design of Feedback Control Systems
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This Course Credit 3
Teaching methods are composed of lecture in class and exercises/experiment after class.
Grading
Homework 20% (Due on Mondays at class)
Participation 10%
Midterm exam 30% (at approximately week8)
Final exam 40%
Pre-request Course
Calculas
Engineering Mathmatics (Complex Variables Functions)
Teaching and Grading
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References
1. Farid Golnarahi ,Benjamin C. KuoAutomatic Control Systems, Ninth edition, John Wiley & Sons Inc,2009.
2. Prof. Steven Hall, course materials for 16.06 Principles of Automatic Control, Fall 2012. MIT OpenCourseWare(http://ocw.mit.edu), Massachusetts Institute of Technology.
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References
3. Richard C. Dorf, Robert H. Bishop, Modern Control Systems, 12th Edition, Prentice Hall,2010.
(you can use an old edition)
4. Robert H. Bishop, Modern Control System Analysis and Design Using Matlab and Simulink,Tsinghua University Press,2003
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Classroom NMB F205
Time Monday 16:00PM - 17:45PM every week
Thursday 8:00AM 9:45AM biweekly
Please Note: