M.Sc. (Electronic Science) (Semester
(CBCS) Examination, 2017
CONTROL SYSTEMS wateriI
Day Date: Wednesday19-04-2017 Max. Marks: 70
Time: 10.30 AM to 01.00 PM
N.B. and are compulsory.
Answer any three questions from Q.3 to Q.7.
All questions carry equal marks.
Use of nonprogrammable calculator is allowed.
Q.1 Select the correct alternative 08
The input to a controller
Sensed signal Desired variable value
Error signal Servo-signal
The laplace transform of unit step signal is
1/s 1 1/s2 1/s3
Two loops are said to be non-touching only if no common
exists between them.
Loop Feedback path Branch Node
While specifying the angle and magnitude conditions, angles
are added whereas magnitudes
Subtracted Multiplied
Divided All of the above
If any root of the characteristic equation has a positive real
part, the system
Stable Unstable
Oscillatory Conditionally stable
system has tendency to oscillate.
Open loop system Closed loop system
Both a and b Neither a and b
Controller with a proportional term and a derivative term is
controller.
PI P PD PID
When two blocks are connected in series, the transfer
functions are to
Added Subtracted
Multiplied Divided
Page 1 of 2
SLR-RH 366
Say true or false. 6
A refrigerator is an example of closed loop system.
Transfer function is applicable to linear time-variant system.
Frequency response of a system is the steady state response
to a unit step input signal.
A compensating network is added to alter the locus of the
roots as the system parameter is varied.
Root locus technique is applicable to single as well as
multiple loop system.
DC servomotors are also called two phase induction motors.
Q.2 Attempt the following. 14
Explain the terms utilized in signal flow graph. 05
Write a short note on on-off controller. 05
Briefly describe the concept of stability. 04
Q.3 Draw a block diagram of closed loop system and an expression for
its transfer function.
08
Derive an expression for transfer function using LTI differential
equation.
06
Q4 Find the gain of the system represented by the following equations. 08
X2 a22 x1 a32 x3
X3 a23 x2 a34 x4
X4 a24 x2 a34 x3 a44 x4
X5 a25 x2 a45 x4
Here, the input node is x1 and output node is x5.
What is signal flow graph? Explain mason's gain formula. 06
Q5 Consider the system with S=-1.21
confirmed to be on the root locus. Determine at what value of
S=-1.21 is one of the roots of use magnitude
condition.
08
Explain the stability of given equation using Hurwitz method. 06
S3 4S2 3S 8
Q.6 Obtain gain margin and phase margin for the loop transfer function
using Bode plot.
08

Explain state model from transfer function using direct method. 06
Q.7 Design and explain a PI controller. Mention its advantages and
disadvantage?
08
Draw and explain the working of potentiometer error detector and
represent in block diagram form.