The document introduces control engineering concepts, defining key terms such as input, output, system, and control system. It differentiates between open loop and closed loop systems, providing examples and outlining their advantages and disadvantages. Open loop systems operate independently of output, while closed loop systems adjust based on output feedback, offering greater accuracy but increased complexity.

1. INTRODUCTION
TO
CONTROL
ENGINEERING

2. 2
What is Input?
 The stimulus or excitation applied to a
control system from an external source in
order to produce the output is called input.
Input

3. 3
What is Output?
Output
Input The actual response
obtained from a system is
called output.

4. 4
What is System?
SYSTEM
Input Output
 A system is an arrangement of or a combination of different physical
components connected or related in such a manner so as to form an entire unit
to attain a certain objective.

5. 5
 To regulate, direct or command a system so that the desired objective is
attained.
What is Control?
System + Control = Control System

6. 6
Control System
CONTROL
SYSTEM
Inpu
t
Outpu
t
It is an arrangement of different physical elements connected in such a manner so
as to regulate, direct or command itself to achieve a certain objective.

7. 7
Difference between System & Control System
System
Inpu
t
Control
System
Inpu
t
Desired
Outpu
t
Proper
Outpu
t
(May or may not
be desired)

8. 8
Difference between System & Control System
Fan
(System
)
230V/
50Hz
AC
Supply
Air
Flow
Input Outpu
t

9. 9
A Fan: Can’t say a System
Output
Input
 A Fan without blades cannot be a “SYSTEM” Because it cannot provide a
desired / proper output. i.e. airflow

10. 10
 A Fan with blades but without regulator can be a “SYSTEM” Because it can
provide a proper output. i.e. Airflow
 But it cannot be a “Control System” Because it cannot provide
desired output i.e. Controlled Airflow
A Fan: Can be a System
Input Outpu
t

11. 11
 A Fan with blades and with regulator can be a “CONTROL SYSTEM”
Because it can provide a Desired Output. i.e. Controlled Airflow
A Fan: Can be a Control System

12. 12
Classification of Control System
(Depending on control action)

13. 13
“A system in which the control action is totally independent of the output of the
system is called as open loop system”
Definition: Open Loop System
Block Diagram of Open loop Control System

14. 14
• Electric hand drier – Hot air
(output) comes out as long as
you keep your hand under the
machine, irrespective of how
much your hand is dried.
Example of Open Loop System

15. 15
 Automatic washing machine: This
machine runs according to the pre-set
time irrespective of washing is
completed or not.
Example of Open Loop System

16. 16
• Bread Toaster: This machine runs as per
adjusted time irrespective of toasting is
complete or not.
Example of Open Loop System

17. 17
• Automatic tea/coffee Vending Machine:
These machines also function for pre
adjusted time only.
Example of Open Loop System

18. 18
• Light Switch: Lamps glow whenever light switch is on irrespective of light is
required or not.
• Volume on Stereo System : Volume is adjusted manually irrespective
of output volume level.
Example of Open Loop System

19. 19
 Simple in construction and design
 Economical
 Easy to maintain
 Generally stable
 Convenient to use as output is difficult to measure
Advantages of Open Loop System

20. 20
Inaccurate
Unreliable
Any change in output can’t be corrected automatically
Disadvantages of Open Loop System

21. 21
“A system in which the control action is somehow dependent on
the output is called as closed loop system”.
Definition of Close Loop System

22. 22
Block Diagram of Close Loop System

23. 23
 Automatic
Electric Iron :
Heating
elements
are controlled
by output
temperature of
the iron.
Example of Close Loop System

24. 24
 Servo Voltage
Stabilizer: Voltage
controller operates
depending upon
output voltage of the
system.
Example of Close Loop System

25. 25
Perspiration
Example of Close Loop System

26. 26
 Closed loop control systems are more accurate even in the presence of non-linearity
 Highly accurate as any error arising is corrected due to presence of feedback signal
 Bandwidth range is large
 Facilitates automation
 The sensitivity of system may be made small to make system more stable
 This system is less affected by noise
Advantages of Close Loop System

27. 27
 They are costlier
 They are complicated to design
 Required more maintenance
 Feedback leads to oscillatory response
 Overall gain is reduced due to presence of feedback
 Stability is the major problem and more care is needed to design a stable closed
loop system
Disadvantages of Close Loop System

28. 28
Difference between Open Loop & Close Loop System