This document discusses open loop and closed loop control systems. An open loop system does not use feedback, so its output is not affected by its input and it cannot compensate for disturbances not accounted for in its design. A closed loop system uses feedback to minimize errors between its output and a desired setpoint, allowing it to reject disturbances and make the system more stable. Examples given of open loop systems are a clothes dryer controlled by a timer and closed loop systems include HVAC systems that use a thermostat for feedback control.

1. Open Loop
& Closed
Loop System
NAME- NITYANANDA GHOSH
DEPARTMENT- APPLIED ELECTRONICS &
INSTRUMENTATION ENGINEERING
UNIVERSITY ROLL NO- 10505522026
SEMESTER- 5TH
CLASS ROLL NO- 17

2. Control
Systems
• An integral part of any industrial society
• Many applications including transportation,
automation, manufacturing, home appliances,…
• Helped exploration of the oceans and space
• Examples: –
 Temperature control
 Flight control
 Process control

3. TypesofControlSystems
Plant
r Sensors
Actuators
Controller
control
input
u
disturbance
d
command output
y
Open loop system
Plant Sensors
Actuators
Controller
error
e
control
input
u
disturbance
d
command
+
r
_
output
y
Closed loop system

4. ControlSystem
Comparison
• Openloop:
 Theoutputvariablesdonotaffecttheinputvariables
 Thesystemwill followthedesiredreferencecommandsif nounpredictableeffects
occur
 Itcancompensatefordisturbancesthataretakenintoaccount
 Itdoesnotchangethesystemstability
• Closedloop:
 Theoutputvariables doaffecttheinputvariablesinordertomaintainadesired
systembehavior
 Requiresmeasurement(controlledvariablesorothervariables)
 Requirescontrolerrorscomputedasthedifferencebetween thecontrolledvariable
andthereferencecommand
 Computescontrolinputsbasedonthecontrolerrorssuchthatthecontrolerroris
minimized
 Abletorejecttheeffectofdisturbances
 Canmakethesystemunstable,wherethecontrolledvariablesgrowwithout bound

5. OverviewofClosedLoopControlSystems
Disturbances
Computer /
Microcontroller
Plant
Inputs
Outputs
Sensors
Actuators
ADC
DAC
Control Algorithm
Scope
Model
Power Amp
Function
Generator
Reference Inputs
(Setpoints)

6. Example-
Open Loop
System
 The clothes dryer is one of the examples of the
open-loop control system. In this, the control action
can be done physically through the operator.
Based on the clothing’s wetness, the operator will
fix the timer to 30 minutes. So after that, the timer
will discontinue even after the machine clothes are
wet.
The dryer in the machine will stop functioning even
if the preferred output is not attained. This displays
that the control system doesn’t feedback. In this
system, the controller of the system is the timer.

7. Example-
Open Loop
System
 The best example of the closed-loop control
system is AC or air conditioner. The AC controls
the temperature by evaluating it with the nearby
temperature. The evaluation of temperature can be
done through the thermostat. Once the air
conditioner gives the error signal is the main
difference between the room and the surrounding
temperature. So the thermostat will control the
compressor.
These systems are accurate, expensive, reliable,
and requires high maintenance.