Introduction to control system( open loop & closed loop system)

ADITYA COLLEGE OF ENGINEERING & TECHNOLOGY
Tuesday, May 5, 2020
CONTROL SYSTEMS
Presented by
Mrs. RAMA VASANTHA ADIRAJU
Sr.Asst.Professor
Department of Electronics and Communication Engineering
STAY SAFE
Time: 9:00 AM to 10.30 AMTopic
Introduction to Control Systems

II ECE- CONTROL SYSTEMS Mrs. RAMA VASANTHA ADIRAJU
Aditya College of Engineering & Technology
• Introduction
• Block diagram
• Types of Systems
• Open loop system
• Close Loop system
• Comparison of Systems
• Translational system
OVERVIEW OF PRESENTATION

• Control system are an integral part of our lives and play very important role.
• From a simple bread toaster to complex power plant, control system are all
around us .
• Generally there are two types of control systems
• Man made CS
• Natural CS
INTRODUCTION

Natural Made
Control systems

Man Made
Control systems

• System: When number of elements connected in a sequence to perform a
particular task is called a system.
• Input quantity: is an excitation of the system
• Output quantity : is a response of the system
• Control System: when the output quantity is controlled by the input quantity is
called a control system
INTRODUCTION

CONTROL
SYSTEM
OPEN LOOP CS
CLOSED LOOP
CS
TYPES OF CONTROL SYSTEMS:

OPEN LOOP CS:
INPUT
OPEN LOOP
CONTROL SYSTEM
OUTPUT
• In open loop control system, the output is varied by varying the input and
• The change in output has no effect on the input quantity

• Advantages
• Simple Construction & Design
• Economic
• Easy maintenance
• Stability
• Disadvantages
• unreliable
• Internal Disturbance
• Recalibration is required time to time
OPEN LOOP CS:
Applications
• In the traffic light controlling system
• TV remote control
• Iron box
• Simple Switch

EXAMPLE for OPEN LOOP CS:
A simple switch: ON & OFF

Controller Plant
Feedback
Error detector
CLOSED LOOP CS:
Feedback signal
output
signal fed
To the
feedback
Reference signal

• Advantages
• More accurate
• Feedback
• More flexible
• Less affected to external disturbances
• Disadvantages
• Complex Construction & Design
• Expensive
• Difficult to maintenance
• UnStability
CLOSED LOOP CS:
Applications
•Automatic Iron box
• Automatic water overflow control
•Temperature control system

EXAMPLE for CLOSED LOOP CS:

Comparison of Open loop and Close loop
systemSr.
No.
Open Loop System Close loop System
1. No feedback. Hence
feedback element is absent.
Feedback exists. Hence
feedback elements are exists.
2. No error detector. Error detector is present.
3. It is inaccurate. It is accurate.
4. Highly sensitive to
parameter changes.
Less sensitive to
parameter changes.
5 Small bandwidth. Large bandwidth.
6. Stable. May become unstable.
7. Economical. Costly.
8. Examples: Coffee maker, hair
drier
Example: automatic washing
machine, automatic iron box

Learn about transfer function
Electric network
Translational mechanical system
Rotational mechanical system
TRANSTIONAL MECHNAICAL SYSTEM:

Laplace transform review

You are going to apply transfer function in three types of mathematical modeling.
Electric network
Translational mechanical system
Rotational mechanical system
Transfer function

Electric Network Transfer Functions
Component
Voltage-
Current
Current-
voltage
Voltage-
charge
Impedance
Z(s)=
V(s)/I(s)
Admittance
Y(s)=
I(s)/V(s)

Simple circuit via mesh analysis
We can obtain transfer function using Kirchhoff’s voltage law and
summing voltages around loops or meshes. This method is called loop or
mesh analysis.

• Identify input & output in the circuit for the given circuit, Here
Input is V(s) Output is VC(s)
• Apply mesh analysis
We obtain
I(s) V(s)
Cs 
1 


Ls  R 

we can only find the input, V(s). In order to calculate the transfer
function we must have the output which is VC(s).
From the circuit,
Cs
CV (s)  I(s)
1

L LC
1/ LC
CLs2
 RCs1
Cs

V(s)
VC (s)

C
Cs

1
s2
R
s 
11





CsLs  R 
1 



Ls  R 
1 V (s)Cs V(s)
Cs
CV (s)  I(s)
1
I(s) VC (s)Cs

Cs
CV (s)  I(s)
1
I(s) VC (s)Cs
L LC
1/ LC
CLs2
 RCs1
Cs

V(s)
VC (s)

C
Cs

1
s2
R
s 
11





CsLs  R 
1 



Ls  R 
1 V (s)Cs V(s)
Cs
CV (s)  I(s)
1
I(s) VC (s)Cs

We can also present our answer in block diagram

Solution summary
Using mesh analysis

Simple circuit via nodal analysis
We obtain the transfer function using Kirchhoff’s current law and summing current
flowing from nodes. This method is called nodal analysis.

Solution:
We will look at the current flowing in and out of the node whose voltage is VC(s). We
assume the current leaving the node is positive and current entering the node is
negative.
L LC
R Ls
VC (s)

V sVC s
1/ Cs R Ls
VC (s)

V sVC s0
1/ Cs
VC (s)

1/ LC
1V(s) s2
R
s 

STAY SAFE
STAY AT HOME
HAPPY LEARNING

Introduction to control system( open loop & closed loop system)

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