block diagram for control systems

Block Diagram Representation of Control Systems

By MSc. Student Mohammed AboAjmaa

1By Mohammed AboAjmaa SDU

Dr. Selçuk ComlekçiA COURSE OFFERED BY

T.C Suleyman Demirel University

College of Engineering Electronic And Communications Eng. Department

What is Block Diagram

A bock diagram is pictorial representation of the functionsperformed by each component and of the flow signals . In a blockdiagram all system variables are linked to each other throughfunctional block, the functional block is a symbol for themathematical operation on the input signal to the block thatproduces the output. A block diagram is high-level type of flowchart.It is useful tool in designing new processes or improving existingprocesses.



Note: Team members who construct a block diagram must have a clear understanding of how the process operates.

Examples about Block Diagram

1- 522113 xaxax

2- 112211 nnn xaxaxax

Draw the Block Diagrams of the following equations:


An open-loop controller is a type of controller thatcomputes its input into a system using only thecurrent state and its model of the system. Acharacteristic of the open-loop controller doesn’tuse feedback to determine if its output has achieved thedesired goal of the input. This means that the systemdoesn’t observe the output of the

processes.

Open-loop control system

GH(s)= Open-loop transfer function



Ex:

A digital camera is used to take a photograph, it istransferred to the computer where processing of thepicture takes place and finally a printout isproduced. This is a open system because no attemptis made to improve the picture. If the person takingthe picture decides to improve the final printoutusing graphics software he has to change to closedloop system by adding

controller.

Closed-loop Control Systems

Feedback control systems are often referred to as closed-loopcontrol systems. In practice, the term feedback control andclosed-loop control are used interchangeably. In a feedbackcontrol system the actuating error signal is the differencebetween the input signal and the feedback signal (which may bethe output signal itself or a function of output signal and itsderivative or integration). The feedback is a fed to the controllerso as to reduce the error and bring the output of the system to adesired value. The term closed-loop control always mean the useof feedback control action in order to reduce system

error.


The General Form Of Feedback Control System


Characteristic Equation

The control ratio is the closed loop transfer function of the system:

)()(1

)(

)(

)(

sHsG

sG

sR

sC

The denominator of closed loop transfer function determines the characteristic equation of the system:

Which given by: 0)()(1 sHsG


For the above system The behavior depends on the value of gain (K).



Ex: Weather Station:

INPUT:The heat from the sun causes

the temperature sensor to produce data and this is sent

to the computer.

PROCESS:Data is received by the

computer and it is processed. The processed data is displayed on the

monitor as a graph.

OUTPUT:The temperature levels are printed out. This is one form of output.

FeedbackThe temperature is continuouslymonitored and this is called feedback.As long as the sensor works, thecomputer processes and the printerprints out - feed back is taking place.

Reduction techniques

The aim of reduction technique is to simplify the block diagram and get transfer function.

C(s)

R(s)=?


Reduction techniques procedure

:1. Combining blocks in cascade or in parallel

1G2G

21GG

1G

2G

21 GG


2. Moving a summing point behind a block:

G G

G

:3. Moving a summing point ahead of a block

G G

G

1


4. Moving a pickoff point behind a block:

G G

G

1

5. Moving a pickoff point ahead of a block:

G G

G


6. Eliminating a feedback loop:

G

H

G

1H

G

G

1

GH

G

1


Find the transfer function of the following block diagrams:

2G 3G1G

4G

1H

2H

)(sY)(sR


Sol:1-

2-


3-

4-

5-

)()(1

)(

)(

)(

32413242121

3241

GGGGGGGHHGG

GGGG

sR

sY


Thanks For Listening


block diagram for control systems

Engineering

loop system

open system

system error

mohammed aboajmaa sduex

mohammed aboajmaa sdunote

mohammed aboajmaa sdudr

student mohammed aboajmaa

openloop control system