the power point basics in control system

1. 1
Introduction to
Control System
CHAPTER 1

2. 2
 Basic terminologies.
 Open-loop and closed-loop.
 Block diagrams.
 Control structure.
 Advantages and Disadvantages of closed-loop.
Chapter Objective.

3. 3
Definition of a control system;
 The control system consists of subsystems and process (or
plant) assembled for the purpose of controlling the output with
desired performance, given a specified input.
1.1 Introduction.

4. 4
Cont’d…
Advantages of control systems;
 Can move large objects with precision; for example (i) elevator,
(ii) radar antenna to pickup strong radio signal and (iii) robot to
operate in the dangerous environment.
 Example:
(i) Elevator
When pressed fourth-floor from first floor, the elevator rises to
the fourth floor with a speed and floor-leveling accuracy design
for passenger comfort.

5. 5
(a) Sub-system and System
subsystem subsystem subsystem
 Subsystem is part of the system that is grouped for a certain
function
 System is a combination of physical and non-physical components
that are configured to serve certain tasks to maintain the output
(b) Plant subsystem
input output
 Plant is a subsystem where an output signal is derived from the
input signal
blower
room thermostat
plant
1.2 Basic Terminologies.

6. 6
(c) Input and Output
 Input = Stimulus
 Output = Response
Cont’d…

7. 7
Cont’d…
(d) System Response
 Ability of system to achieve desired result is measured in terms
of system response: comparison of output versus input.
 Transient response.
 Steady State Response.
 Steady State Error.

8. 8
 Disturbance is the unwanted signal that may sway the output .
 Controller is a subsystem that is used to ensure the output
signal follows the input signal.
 The Open-Loop System cannot compensate for any
disturbance that add to the system.
 Example; bread toaster.
1.3 Open Loop System.

9. 9
 The Close-Loop (feedback control) System can overcome the
problem of the Open Loop System in term of sensitivity to
disturbance and inability to correct the disturbance.
1.4 Close-Loop System.

10. 10
The design of a control system follows these steps;
Step 1: Transform Requirement into a Physical System.
Step 2: Draw the Functional Block Diagram.
Step 3: Create the Schematic.
Step 4: Develop the Mathematical Model or Block Diagram.
Step 5: Reduce the Block Diagram.
Step 6: Analyze and Design.
1.5 The Design Process.

11. 11
 Transfer function is the ratio of the output over the input
variables.
 The output signal can then be derived as; C = GR
(a) Multi-variables.
1.7 Block Diagram.
)
(
)
(
)
(
s
R
s
C
s
G 

12. 12
(b) Block Diagram Summing point.
Cont’d…
Figure 1.7: Block Diagram of Summing Point.

13. 13
(c) Linear Time Invariant System.
Cont’d…
Figure 1.8: Components of a Block Diagram for a Linear, Time-
Invariant System.

14. 14
Cont’d…
Figure 1.10: Parallel System and the Equivalent Transfer Function.
Figure 1.9: Cascade System and the Equivalent Transfer Function.
(d) Cascade System.

15. 15
(e) Summing Junction.
(f) Pickoff Points.
Cont’d…
Figure 1.12: Block diagram algebra for
pickoff points— equivalent forms for
moving a block (a) to the left past a pickoff
point; (b) to the right past a pickoff point.
Figure 1.11: Block diagram algebra for
summing junctions: equivalent forms for
moving a block (a) to the left past a
summing junction; (b) to the right past a
summing junction.

16. 16
Cont’d…
Figure 1.13: Block diagram reduction Example 1. (a) collapse summing
junctions; (b) form equivalent cascaded system in the forward path and
equivalent parallel system in the feedback path; © form equivalent
feedback system and multiply by cascaded G1(s)

17. 17
 E(s) error signal
R(s) reference signal
Y(s) output signal
C(s) output signal
B(s) output signal from feedback
 Feed forward transfer function,
 Feedback transfer function,
 Open-loop transfer function,
1.8 Control Signal.
)
(
)
(
)
(
s
R
s
C
s
G 
)
(
)
(
)
(
s
C
s
B
s
H 
)
(
)
(
)
(
)
(
s
H
s
G
s
E
s
B


18. 18
 Close-Loop transfer function,
 Assume give
 Variable difference,
 Characteristic equation,
)
(
)
(
)
( s
B
s
R
s
E 

)
(
)
(
)
(
)
( s
Y
s
H
s
R
s
E 

)
(
)
(
)
(
)
(
)
(
s
Y
s
H
s
R
s
G
s
Y


)
(
)
(
1
)
(
)
(
)
(
s
H
s
G
s
G
s
R
s
Y


Cont’d…
1
)
( 
s
H )
(
)
( s
B
s
Y 
.
)
(
)
(
1
)
( s
H
s
G
s
T 

0
)
(
)
(
1 
 s
H
s
G

19. 19
 Physical model.
 Graphical model.
 Mathematical model.
(a) Current-voltage relationship v = ir.
v – voltage in Volt (V).
i – current in Ampere (A).
r – resistance in Ohm.
(b) Force-deflection relationship
f – force in Newton (N).
k – spring constant
x – displacement in meter (m).
(c) Mass-spring model
fo - applied force
x - displacement
fs - reaction force
1.9 Model.

20. 20
Transient state
 A state whereby the system response after a perturbation before
the response approach to a steady condition
Steady state
 A state whereby the system response becomes steady after a
transient state.
Stability
 The condition of the steady state. If the response converges to
a finite value then it is said to be in a stable condition and if the
response diverges, it is known to be unstable.
 A system must be stable in order to produce the proper
transient and steady state response.
 Transient response is important because it effects the speed of
the system and influence human patience and comfort.
1.10 Design Analysis.

21. 21
1.11 Design.
Analogue controller
 A controller that used analogue subsystem.
Digital Controller
 A controller that used computer as its subsystem.
Figure 1.14: Controller in Computer Subsystem.
computer drive plant
sensor
_
+
Referene
input
Actual
output

22. 22
0 2 4 6 8 10 12 14 16
0
500
1000
1500
Time [seconds]
S
pe
e
d
[rpm]
Sine Wave Reference and Speed Response of Direct Inverse Control Scheme.

23. 23
0 2 4 6 8 10 12 14 16
0
200
400
600
800
1000
1200
1400
1600
Time [seconds]
S
pe
e
d
[rpm]
Ramp Wave Reference and Speed Response of Direct Inverse Control Scheme.

24. 24
0 1 2 3 4 5 6 7 8 9 10
0
200
400
600
800
1000
1200
1400
1600
1800
Time [seconds]
S
pe
e
d
[rpm]
Unit Step Response with Direct Inverse Control.

25. 25
0 2 4 6 8 10 12 14 16
0
200
400
600
800
1000
1200
1400
1600
1800
Time [seconds]
S
pe
e
d
[rpm]
Square Wave Reference and Speed Response of Direct Inverse Control Scheme.