Automatic Control system | Function | Elements | Advantage and disadvantage

Here we learn about Automatic Control system, Function, Elements,  Advantage and disadvantage



Automatic Control $ystem :

Definition of control $ystem :

~ A control $y$tem i$ defined a$ an asemblage of device$ and component$ connected or interrelated $o a$ to command, direct, or regulate it$elf or another $y$tem.

~ Example$ of control $ystem are an electric $witch, Air conditioner, Boiler control etc.

~ An automatic control $y$tem is a pre$et clo$ed-loop control $y$tem that require$ no operator action. Thi$ assume$ the proces$ remain$ in the normal range for the control $y$tem. An automatic control $y$tem ha$ two proce$$ variable$ a$$ociated with it a controlled variable and a manipulated variable .

~ A controlled variable i$ the proce$$ variable that i$ maintained at a $pecified value or within a $pecified range. For example. the $torage tank level i$ the controlled variable.

~ A manipulated variable i$ the proce$$ variable that i$ acted on by the control $y$tem to maintain the controlled variable at the $pecified value or within the $pecified range. For example, the flow rate of the water $upplied to the tank i$ the manipulated variable.

Function$ of Automatic Control :



~ In any automatic control $y$tem, the four ba$ic function$ that occur are :

(i) Mea$urement

(ii) Compari$on

(iii) Computation

(iv) Correction

~ In the water tank level control $y$tem in the example above, the level tran$mitter mea$ure$ the level within the tank. he level tran$mitter $end$ a $ignal repre$enting the tank level to the level control device, where it i$ compared to a de$ired tank level. The level control device then compute$ how far to open the $upply valve to correct any difference between actual and de$ired tank level$.



Elements of Automatic Control :





~ The three functional element$ needed to perform the function$ of an automatic control $y$tem are :

(i) A mea$urement element

(ii) An error detection element

(iii) A final control element



~ Relation$hip$ between the$e element$ and function$ they perform in an automatic control $y$tem are $hown in Fig. 6.1.1.

~ The mea$uring element perform$ the mea$uring function by $en$ing and evaluating the controlled variable. The error detection element fir$t compare$ the value of the controlled variable to the de$ired value, and then $ignal$ an error. If a deviation exi$t$ between the actual and de$ired value$, the final control element re$pond$ to the error $ignal by correcting the manipulated variable of the proce$$.

Automatic control $y$tem :

~ Automatic control $y$tem i$ a pre$et clo$ed loop $y$tem that require$ no operator action. Automatic control $y$tem$ are u$ed in almo$t every pha$e of indu$trial operation$. The different application$ of automatic control $y$tem$ are :

(1) Proce$$ indu$trie$ $uch a$ petroleum, chemical and $teel. Power etc. control of temperature, pre$$ure, flow and etc.

(2) In certain good$ $uch a$ automobile part$,

refrigeration. For control of a$$embly operation$, work, flow, heat treatment, etc.

(3) Tran$portation $y$tem$ $uch a$ railway, airplane$, $hip$ etc.

(4) Power machine$ $uch a$ machine tool$, compre$$or$, pump$, etc.



Advantage$ of automatic control $y$tem:

1. Uniformity of product$ improve$.

2. Production rate increa$e$.

Application$ of automatic control $y$tem:

1. In tran$portation $y$tem$ $uch a$ railway$, airplane$ etc.

2. Power machine$, compre$$or$ etc.

3. In refrigeration $y$tem$.