Lecture Control system design: Feedback control system characteristics presents the following content: Error signal analysis, sensitivity of control systems to parameter variations, disturbance signals in a feedback control system, control of the transient response, steady – state error, the cost of feedback, control system characteristics using control design software.
Trang 1Nguyễn Công Phương
CONTROL SYSTEM DESIGN
Feedback Control System
Characteristics
Trang 2I Introduction
II Mathematical Models of Systems
III State Variable Models
IV Feedback Control System Characteristics
V The Performance of Feedback Control Systems
VI The Stability of Linear Feedback Systems
VII The Root Locus Method
VIII.Frequency Response Methods
IX Stability in the Frequency Domain
X The Design of Feedback Control Systems
XI The Design of State Variable Feedback Systems
XII Robust Control Systems
XIII.Digital Control Systems
Trang 3Feedback Control System
Characteristics
1 Introduction
2 Error Signal Analysis
3 Sensitivity of Control Systems to Parameter
Variations
4 Disturbance Signals in a Feedback Control
System
5 Control of the Transient Response
6 Steady – State Error
7 The Cost of Feedback
8 Control System Characteristics Using Control
Design Software
sites.google.com/site/ncpdhbkhn 3
Trang 4Introduction (1)
• An open – loop system operates without
feedback & directly generates the output in
response to an input signal.
• It is highly sensitive to disturbances & to
changes in parameters of the process.
Process
Desired output
Open – loop control system (without feedback)
Disturbance
Trang 5Introduction (2)
• A closed – loop system uses a measurement of the input signal & a
comparison with the desired output to generate an error signal that is used
by the controller to adjust the actuator.
• Advantages:
– Decreased sensitivity of the system to variations in the parameters of the
process.
– Improved rejection of the disturbances.
– Improved measurement noise attenuation
– Improved reduction of the steady – state error of the system.
– Easy control & adjustment of the transient response of the system.
Closed – loop control system with external disturbances & measurement noise
Trang 6Feedback Control System
Characteristics
1 Introduction
2 Error Signal Analysis
3 Sensitivity of Control Systems to Parameter
Variations
4 Disturbance Signals in a Feedback Control
System
5 Control of the Transient Response
6 Steady – State Error
7 The Cost of Feedback
8 Control System Characteristics Using Control
Design Software
Trang 8Error Signal Analysis (2)
Trang 9Feedback Control System
Characteristics
1 Introduction
2 Error Signal Analysis
3 Sensitivity of Control Systems to Parameter
Variations
4 Disturbance Signals in a Feedback Control
System
5 Control of the Transient Response
6 Steady – State Error
7 The Cost of Feedback
8 Control System Characteristics Using Control
Design Software
sites.google.com/site/ncpdhbkhn 9
`
Trang 10Sensitivity of Control Systems to
Trang 12Sensitivity of Control Systems to
Parameter Variations (3)
( ) ( )
System sensitivity is the ratio of the change in the system
transfer function to the change of a process transfer function
(or parameter) for a small incremental change.
Trang 13sites.google.com/site/ncpdhbkhn 13
Sensitivity of Control Systems to
Parameter Variations (4)
( ) ( ) ( )
1 ( ) ( )
c c
T S
Trang 14Sensitivity of Control Systems to
K K T
G
K T
K K K
K G
Trang 151 1
1 1
Trang 16Sensitivity of Control Systems to
K G
a
T K
Trang 17Feedback Control System
Characteristics
1 Introduction
2 Error Signal Analysis
3 Sensitivity of Control Systems to Parameter
Variations
4 Disturbance Signals in a Feedback Control
System
5 Control of the Transient Response
6 Steady – State Error
7 The Cost of Feedback
8 Control System Characteristics Using Control
Design Software
sites.google.com/site/ncpdhbkhn 17
Trang 20K R
Trang 22Feedback Control System
Characteristics
1 Introduction
2 Error Signal Analysis
3 Sensitivity of Control Systems to Parameter
Variations
4 Disturbance Signals in a Feedback Control
System
5 Control of the Transient Response
6 Steady – State Error
7 The Cost of Feedback
8 Control System Characteristics Using Control
Design Software
Trang 23K s
m
a b m a
1
K k E s
Trang 24Control of the Transient
K R
a
a t
K G s s
Trang 26Feedback Control System
Characteristics
1 Introduction
2 Error Signal Analysis
3 Sensitivity of Control Systems to Parameter
Variations
4 Disturbance Signals in a Feedback Control
System
5 Control of the Transient Response
6 Steady – State Error
7 The Cost of Feedback
8 Control System Characteristics Using Control
Design Software
Trang 27R s
s
1 ( ) ( )
Trang 28Steady – State Error (2)
101 91
c
K
e K
Trang 29Feedback Control System
Characteristics
1 Introduction
2 Error Signal Analysis
3 Sensitivity of Control Systems to Parameter
Variations
4 Disturbance Signals in a Feedback Control
System
5 Control of the Transient Response
6 Steady – State Error
7 The Cost of Feedback
8 Control System Characteristics Using Control
Design Software
sites.google.com/site/ncpdhbkhn 29
Trang 30The Cost of Feedback
• Feedback control is very good, but
• An increased number of components &
• The loss of gain:
• The possibility of instability
( ) ( ) ( ) ( )
1 ( ) ( )
c c
Trang 31Feedback Control System
Characteristics
1 Introduction
2 Error Signal Analysis
3 Sensitivity of Control Systems to Parameter
Variations
4 Disturbance Signals in a Feedback Control
System
5 Control of the Transient Response
6 Steady – State Error
7 The Cost of Feedback
8 Control System Characteristics Using Control
Design Software
sites.google.com/site/ncpdhbkhn 31
Trang 32Control System Characteristics Using Control Design Software
s s
Load ( )
Ex.