Block diagram representation

BLOCK DIAGRAM REPRESENTATION

MADE BY - NIRALI MONANIBRANCH - ELECTRONICS & COMMUNICATION

INTRODUCTION

• A Block Diagram is a shorthand pictorialrepresentation of the cause-and-effectrelationship of a system.

• The interior of the rectangle representing theblock usually contains a description of or thename of the element, gain, or the symbol for themathematical operation to be performed on theinput to yield the output.

• The arrows represent the direction of information or signal flow.

dt

dx y

COMPONENTS OF BLOCK DIAGRAM

ADVANTAGES OF BLOCK DIAGRAM

• THE FUNCTIONAL OPERATION OF THE SYSTEM CAN BE OBSERVED FROM BLOCK DIAGRAM

• BLOCK DIAGRAM GIVES THE INFORMATION ABOUT PERFORMANCE OF SYSTEM

• BLOCK DIAGRAM IS USED FOR ANALYSIS & DESIGN OF CONTROL SYSTEM

• IT IS VERY SIMPLE TO CONSTRUST THE BLOCK DIAGRAM FOR BIG & COMPLICATED SYSTEM

DISADVANTAGES OF BLOCK DIAGRAM

• BLOCK DIAGRAM FOR GIVEN SYSTEM ARE NON UNIQUE

• SOURCE OF ENERGY IN THE SYSTEM IS NOT SHOWN IN THE DIAGRAM

• IN THE PROCEDURE OF REDUCTION OF BLOCK DIAGRAM ALGEBRA SOME IMPORTANT FUNCTIONSMAY BE OMITTED . THERE IS NO CHECK FOR IT

• IT DOESN’T GIVE ANY INFORMATION ABOUT PHYSICAL CONSTRUCTION OF THE SYSTEM

Canonical Form of A Feedback Control System

Characteristic Equation

• The control ratio is the closed loop transfer function of the system.

• The denominator of closed loop transfer function determines thecharacteristic equation of the system.

• Which is usually determined as:

)()(

)(

)(

)(

sHsG

sG

sR

sC

1

01 )()( sHsG

RULES OF BLOCK DIAGRAM REDUCTION

Reduction techniques procedure

:1. Combining blocks in cascade or in parallel

1G2G

21GG

1G

2G

21 GG

14

2. Moving a summing point behind a block:

G G

G

:3. Moving a summing point ahead of a block

G G

G

1

15

4. Moving a pickoff point behind a block:

G G

G

1

5. Moving a pickoff point ahead of a block:

G G

G

16

6. Eliminating a feedback loop:

G

H

G

1H

G

G

1

GH

G

1

17

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