# Control System Interview Questions with Answers: Part-2

### Control System Interview Questions with Answers - Part-2

[1] What are the three basic elements of control systems?
(i) Feedback element
(ii) Controller
(iii) Controller system

[2] What are the basic elements used for modelling mechanical rotational system?
By using three basic elements, the model of mechanical rotational system can be obtained.
They are
(1) Mass with moment of Inertia (J)
(2) Dash-pot with rotational frictional co-efficient(B)
(3) Torsional sprint with stiffness (K)

[3] Give some example for test input signals?
(1) Step signal
(2) Unit step signal
(3) Ramp signal
(4) Unit parabolic signal
(5) Impulse signal
(6) Sinusoidal signal

[4] What is a mathematical model?
A mathematical model consists of a collection of equations describing the behavior of the system.

[5] Name two types of electrical analogous for mechanical system
The two types of analogies for the mechanical system are
[1] Force - Voltage analogy and
[2] Force - Current analogy.

[6] Classify the system based on the value of s
(1) Undamped system s=0
(2) Under-damped system 0<s<1
(3) Critically damped system s=1
(4) Over-damped system s>1

[7] What is actuating signal?
The error detector compares the feedback from the plant output with the input signal and therefore deviation obtained is called actuating signal.

[8] What are the two main parts of time response?
It is the response of the system when it approaches infinity
Transient state response:
It is the response of the system when the system change from on state to another.

[9] Define damping ratio?
Damping ratio is defined as the ratio of actual damping to critical damping.

[10] List the time domain specification.
(1) Delay time (td)
(2) Rise time (tr)
(3) Peak time (tp)
(4) Peak overshoot (tmp)
(5) Settling time (tr)

Delay time:
The time taken for response to reach 50% of final value for the very first time is delay time.

Rise time:
The time taken for response to raise from 0% to 100% for the very first time to rise time.
Under-damped system - The rise time is from 0% to 100%
Over-damped system - The rise time is from 0% to 90%
Critically damped system - The rise time is from 5% to 95%

Peak time:
The time taken for the response to reach the peak value for the very first time is peak time.

Peak over shoot:
It is defined as the ratio of maximum peak value measured from the final value to final value
expression entered.

Settling time:
It is defined as the time taken by the response to reach and stay with in specified error. It is usually expressed as % of final value.