control system open loop and closed loop system explain and explain their applications this suitable for engineering student level,

2. Contents
 Open Loop Control Systems
 Closed Loop Control Systems

3. What is “controlling”?
 To cause a machine or process to
function in a predetermined manner.
 To energize or de-energize an output
 To set a data table bits to on or off a
machine, by a user program.

4. What is a Control System?
 A control system is a system of devices or set
of devices, that manages, commands, directs
or regulates the behaviour of other device or
system to achieve desire results.
 A control system is a system, which controls
other system.
ProcessInput Output

5. Control System
Open Loop
Control
System
Close Loop
Control
System

6. Open Loop Control System
Controller Process

7. A control system in which the
output has no effect on the control
action.
Do not provide feedback of the
actual state of the system.
There is no comparing of output
with the input for control purposes.
The action is totally independent of
output of the system.

8. Applications of Open Loop Control System
 Electric Hand Drier
 Automatic Washing Machine
 Bread Toaster
 Automatic Tea/Coffee Maker
 Timer Based Clothes Drier
 Light Switch
 Volume on Stereo System

9. Advantages
 Simple in construction and design.
 Economical.
 Easy to maintain.
 Generally stable.
 Convenient to use as output is difficult to
measure.

10. Disadvantages
 Open loop control systems are
inaccurate.
 These are not reliable.
 Any change in output cannot be
corrected automatically.
 These are slow

11. Closed Loop Control System
Controller Process Output
Command
Signal,
Setpoint
Measurement
+
-
Error

12.  Control system in which the output
has an effect on the input quantity.
A closed loop system is called a
feedback control system.
It provides feedback of the actual state
and compare it to the desired state of
the system.
The input quantity will be adjusted
based on the output generated to
produce the desired output response.

13. Applications of Closed Loop Control
System
Automatic Electric Iron
Servo Voltage Stabilizer
Water Level Controller
Missile Launched & Auto Tracked by
Radar
An Air Conditioner
Cooling System in Car

14. Advantages
 This system is more reliable
 A number of variables can be handled simultaneously.
 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.

15. Disadvantages
 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.

16. Requirement Of Good Control System
 Accuracy:
error detector should be present in control system to increase
accuracy
 Sensitivity :
It should be sensitive to input signal only
 Noise :
control system should be able tor reduce noise effect for better
performance
 Stability:
system must be able to remove offset
 Bandwidth:
bandwidth should be large as possible for frequency response
 Speed :
This is the time taken by control system to achieve its stable

17. Open Loop vs. Closed Loop
Open loop control system Closed loop control system
1
The feedback element is
absent
The feedback element is always
present
2
An error detector is not
present
An error detector is always
present
3 It is stable one. It may become unstable
4 Easy to construct Complicated construction
5
It is an economical
It is costly
6 Small bandwidth Large bandwidth
7
It is inaccurate
It is accurate
8
Less maintenance
More maintenance