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What are the Elements of Automatic Control System? and Properties

What are the Elements of Automatic Control System? and Properties

The method by which counteraction is produced in an automatic controller. It is called the mode of control action. An automatic controller consists of the following elements.

1. Measuring means (c - b)

2. Input means (v - r)

3. Actuating means (r - b)

4. Controlling means (l - m)

5. Final Control Elements (m - c)


c = Controlled variable

b = Feedback Variable

v = Setpoint

r = Reference input

l = Actuating signal

m = Manipulated Variable

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What are the Elements of Automatic Control System? and Properties

1. Measuring Means

It converts controller variables (temperature, pressure, etc.) into indicated variables (displacement). Example. Thermometer, pressure gauge, flow meter. 

Measuring means = controller variable - feedback variable

2. Input Means

It converts the reference input to the same unit as the set point. It follows the following rule.

Input Means = Set point - A reference point

3. Actuating Means

It is a simple subtracting device that follows the following rules.

Actuating means = Reference input - feedback Variable

4. Controlling Means

It converts the actuating signal by amplification, differentiating, integrating, etc. in which the controller receives the output, which operates the final controller element to change the magnitude of the manipulated variable.

5. Final Control Element 

The final control element is the mechanism that produces a change in the magnitude of the manipulated variable generated by the automatic device. Or final control element is a mechanism that changes the value of the manipulated variable based on the output signal received from the automatic control system device as shown in the figure.

Final Control Element

It consists of two parts (A) Actuator and (B) Manipulated Variable.

(A) Actuator Ues

It can be used in automatic control to change the output signal to the position of the high powered member.

(B) Manipulated Variable

We can specify all the elements suitable for the device used to adjust the value of the manipulated variable by a remote set pressure regulator. As shown the diaphragm of the chamber acts like a measuring means.

The upward force of downstream pressure is the feedback variable. The diaphragm and upper chamber act as input means that convert the desired value of pressure (set point) into downward force. This downward force is the reference (l) and input (r). Its diaphragm is the actuating means as a result of which the actuating signal is obtained. The steam and the plug act as controllers that convert the actuating signal into a variable flow of liquid through the regulator. Flow rates are the only manipulated variable. This is the action of the remote set point pressure regulator.

Process Variable in Control System

The process variable which is used to change the state or direction of magnitude is called the process variable.

There are three types of process variables i. The manipulated variables ii. Controlled variables iii. Load Variables.

(i) Manipulated Variable

The manipulated variable of the process is that variable that is selected for adjustment by the automatic controller so as to maintain the controller variable at the desired value.

(ii) Controlled Variable

The controlled variables of the process should be variables that must directly indicate the desired form or state of the product.

(iii) Load Variables

The load variable of the process is all other independent variables except the controlled variable and the manipulated variable.

Automatic Control System Properties

1. Finds the value of a controlled variable by measuring means. 

2. Compares the actual value with the desired value. 

3. Produces the necessary counteraction to maintain the small positive charge. 

4. In the end, with the help of all these functions, an equation is derived.

What is signal definition easy?

A signal is information that is sent from one part of the system to another. signal, mechanical, electrical, hydraulic means, etc. are generated from.

What is a transient response in the control system?

A transient response such as response input and output relation changes with time.

What is meant by a set point?

Controlled variables have a selected reference value from which maintenance is done called a set point.

What is called an offset?

The steady-state derivation obtained when the value of the load variable changes, is called offset.

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