This document provides an introduction to PID controllers and PLC systems. It discusses the basic components and functions of PID controllers, including proportional, integral and derivative controls. It also summarizes the basic architecture of PLC systems, including the CPU, memory, input/output units and programming methods like ladder logic, statement lists and function block diagrams. Common instructions for timers, counters and logic operations are also covered.

1. PID Controllers
and introduction to
PLC systems
By
Dr. Palitha Dassanayake

2. Control Systems
Speed
Time
Motion
profile
Micro-processor control system

3. Fly ball governor
Steam
valve
James watt
(speed increases,
Steam value closes)
Control Systems in early days

4. Input- Voltage
Output-Rotated angle
Control System
Voltage
Voltage
Amplifier
Telephone line

5. Amplifications Amplifications Amplifications
Telephone line amplification problem
noise noise noise noise
noise
With the amplification, noise gets increased and increased…

6. Input
voltage(a) Amplifier
gain
Output
voltage
Amplifier
gain
Attenuator
circuit
Input
voltage
Output
voltage(b)
_
+

7. -
Feedback
gain
+
Reference
input(b) Controller
Controlled
variable
Process
Actuating
signal
Reference
input
(a)
Controller
Controlled
variable
Process
Actuating
signal
Open Loop control system
Closed Loop control system

8. PID controller
P= proportional
I=Integral
D=Derivative
90%-95% closed loop automatic
controllers are PID

9. Automatic Controller
-
Sensor
+
Reference
input r(t)
Controller PlantActuator
Output y(t)

10. Step input and on and
off controller
r(t)
Time
A
If y(t)<r(t) ON
If y(t)>r(t) OFF
Time
y(t)

11. P controllers
_
Sensor
feedback
+
Set value r(t) Output y(t)
P process
Steady State Error ?
Transient Response
Time
u(t)
SSE
)()(()( trtykptu −=

12. P controller outputs
Input r(t)= step input value 2
s+
=
1
1
functionTransfer
Kp=1
Kp=5
Steady state error decreases with kp for this particular application
Plant

13. Reducing S.S.E
_
+
Set value Output
P
+
+
plant
U(t)
We may place an external input,
but different set points have different SSE ?

14. PI Controller
))()(()( tytrte −=
P
_
+
Set value Output
I
+
+
process
U(t)
e(t)
∫+= dttekitekptu )(*)(*)(
Integral part

15. PI controller output
Step input value =2 Kp=5
KI=1
KI=5
S.S.E exists
S.S.E is zero
KI=20 There is an overshoot

16. PID controllers
P
_
+
Set value Output
I
D
+
+
+
plant
dt
tde
kddttekitekptu
)(
*)(*)(*)( ++= ∫
))()(()( tytrte −=

17. PID controller output
Step input value =2 Kp=5 and KI=20
KD=1
KD=10
S.S.E still exists
Transient response is also less

18. PID controller output
contd. Kp=5, KI=20 and KD=10
input r(t)- pulse input
output y(t)

19. Tuning of PID
controllers
PID values are different from one system to another
It is required to tune a P, PD, PI or PID controller
Basic industrial approaches
 Design a stable tuned PID controller after modeling
 Develop a simulator after modeling and tune
observing the simulator result
 On site tuning
 Combination of all three approaches

20. PLC is similar to using a computer but has certain features
that are specific to their use as controllers.
These are:
1. They are rugged and designed to withstand vibrations,
temperature, humidity and noise.
2. The interfacing for inputs and outputs is inside the controller.
3. They are easily programmed and have an easily understood
programming language. Programming is primary concerned
with logic and switching operations.
Programmable Logic Controllers

21. Data bus
Address bus
Control bus
CPU
clock
Memory
Input/
Output
unit
Program
panel
Input
channels
Output
channels
Architecture of a Programmable Logic Controller

22. Normally opened contact
Normally closed contact
AND operation
LADDER DIAGRAMS
OR operation
Output
Special Instruction

23. I0.0 Q0.0
I0.1 Q0.1
I0.0 I0.1 Q0.0
Ladder diagram using S7 200
Q0.0I0.0
I0.1

24. Setting and Resetting an output
I0.0 Q0.0
I0.1 Q0.0
S
R
Setting and Resetting a Memory
I0.0 M0.0
S
I0.1 M0.0
R

25. Memory
Input Register I
Type Symbol Example
Bit I0.1
Byte IB4
Output Register O
Type Symbol Example
Bit Q1.1
Byte QB5

26. Variable Memory V
Store intermediate results performed by the
control logic in a program
Type Symbol Example
Bit V10.1
Byte VW100
Bit Memory M
Store intermediate status of an operation or
other control information
Type Symbol Example
Bit M26.7
Byte MD20

27. Two types of timers available
1. On Delay Timer
2. Off Delay Timer

28. On Delay Timer (T33- steps of 10ms)
I0.0 T33
2000+
IN
PT
TON
Q
ET
T33 Q0.0
Time
onSwitch
ON
Bulb
OFF
20s
offSwitch

29. Off Delay Timer (T33- steps of 10ms)
I0.0 T33
1500+
IN
PT
TOF
Q
ET
T33 Q0.0
Time
onSwitch
ON
Bulb
OFF
15s
offSwitch

30. Counters
I0.0 C48
5+
UP
R
C48 Q0.0
PV
I0.1

31. Logo Programming
&
I1
I2
Q1
AND Operation
I1
I2
Q1
OR Operation
1≤

32. S7 200 Programming Techniques
1. Ladder Programming
2. Statement Lists (SLT)
3. Function Block Diagrams

33. Statement List (SLT)
This programming method introduces a list of statements.
Let’s look at the basic programming using SLT.
Statement List (SLT)
This programming method introduces a list of statements.
Let’s look at the basic programming using SLT.
AND Operation
LD I I0.0 // Read I0.0
A I I0.1 //and with I0.1
= Q0.0 //write the value to Q0.0
Statement List (SLT)
This programming method introduces a list of statements.
Let’s look at the basic programming using SLT.
AND Operation
LD I I0.0 // Read I0.0
A I I0.1 //and with I0.1
= Q0.0 //write the value to Q0.0
OR Operation
LD I I0.0 // Read I0.0
O I I0.1 //or with I0.1
= Q0.0 //write the value to Q0.0

34. On delay Timer
Network 1
LD I0.0
TON T33,+2000
Network 2
LD T33
= Q0.0
Network 1
LD I0.0
LD I0.1
CTU C48,+5
Network 2
LD C48
= Q0.0
Timers Counters

35. I0.0
I0.1
AND
Q0.0
Functional Block Diagrams
I0.0
I0.1
OR
Q0.0

36. END