Kreatryx

Subject Test

Control Systems

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1

KST- General Instructions during Examination

1. Total Duration of KST is 60 minutes.

2. The question paper consists of 2 parts. Questions 1-10 carry one mark each and

Question 11-20 carry 2 marks each.

3. The question paper may consist of questions of Multiple Choice Type (MCQ) and

Numerical Answer Type.

4. Multiple choice type questions will have four choices against A, B, C, D, out of which

only ONE is the correct answer.

5. All questions that are not attempted will result in zero marks. However, wrong

answers for multiple choice type questions (MCQ) will result in NEGATIVE marks.

For all MCQ questions a wrong answer will result in deduction of 𝟏/𝟑 marks for a 1-mark

question and 𝟐/𝟑 marks for a 2-mark question.

6. There is NO NEGATIVE MARKING for questions of NUMERICAL ANSWER TYPE.

7. Non-programmable type Calculator is allowed. Charts, graph sheets, and

mathematical tables are NOT allowed during the Examination.

2

Q.1 In the Bode – plot of a unity feedback control system, the value of phase of G(jω) at the

gain cross over frequency is 0125 . The phase margin the system is

(A) 0125 (B) 055 (C) 055 (D) 0125

Q.2 The transfer function for this plot is

(A)

4 1 0.5s

s 1 0.1s

(B)

4 1 2s

s 1 10s

(C)

4s 1 0.5s

s 1 0.1s

(D)

4s 1 2s

s 1 10s

Q.3 The Nyquist plot of a system is shown below. What is the type of the system?

(A) 1

(B) 2

(C) 0

(D) 3

Q.4 The open – loop transfer function of a feedback control system is

3

1G s .H s

s 1 The

given margin of the system is

(A)2 (B)4 (C)8 (D)16

3

Q.5 Consider a closed-loop system shown in fig. (A) below. The roots locus for it is shown in fig.

(B). The closed loop transfer function for the system is

(A)

K

1 0.5s 1 10s 1 (B)

K

s 2 s 0.1

(C)

K

1 K 0.5s 1 10s 1 (D)

K

K 0.2 0.5s 1 10s 1

Q.6 The root locus diagram for a closed – loop feedback system is shown in figure. The system

is over damped.

(A)Only if 0 K 1

(B)Only if 1 K 5

(C)Only if K 5

(D) If 0 K 1 or K 5

Q.7 The roots-locus plot of the system having the open loop transfer function

2

kG s H s

s s 1 s 4s 5

has

(A) No break away point (B) Three real break away point

(C) Only break away point (D) One real & two complex breakaway points

Q.8 The set of differential equation 1 1 2 2 1 2

X X 4X ,X 2X X u t where 1X , 2X are

states and u(t) is the input to the system. The system is

(A)Controllable & stable (B)Controllable & Unstable

(C)Uncontrollable & stable (C)Uncontrollable & unstable

4

Q.9The Laplace transformation of f(t) is

2 2

F ss

, the final value of f(t) is

(A)Infinity

(B)Zero

(C)One

(D)None of these

Q.10 For a second order system with unity feedback and

225G(s)

s(s 6). The resonance peak is?

(A)2.55 (B)14.39 (C)6 (D)22.64

Q.11 Determine the response when input is unit step of the system

2

C S 1

R S S 1 S 1

(A) t1 11 e sin t / 4

2 2

(B) t1 11 e sin t / 4

2 2

(C) t1 11 e sin t / 4

2 2

(D)None of the above

Q.12 For what values of ‘a’ does the system shown in figure have a zero steady state error

ti.e. lim E t for a step input?

(A)a = 0

(B)a 4

(C)a = 2

(D)For no value of ‘a’

Q.13

*

1 1

*2

2

X 0 1 X 0u

1 2 X 1X

, the STM is

(A)t t t

t t t

e e te

te te e

(C)t t t

t t t

te e te

te te e

(B)t t t

t t t

te e te

te te e

(D)None

5

Q.14 The feedback control system is shown n0.5 & 3

(A) tK 1, K 0.75

(B) tK 9, K 0.22

(C) tK 10, K 0.5

(D) tK 3, K 0.5

Q.15 Consider the unit step response of unity feedback control system whose open loop

transfer function is

1G s

s s 1

the maximum overshoot is equal to

(A)0.143 (B)0.153 (C)0.163 (D)0.173

Q.16 Match List – 1 (characteristics equation) with list – 2 (Nature of unity step response) and

select the correct answer using the code given below the lists:

List – I List - II

(Characteristics equation) (Nature of unit step response)

A 2s 8s 15 0 1. Un-damped

B 2s 24s 225 0 2. Under damped

C 2s 100 0 3. Critically damped

D 2s 20s 100 0 4. Over damped

A B C D

(A) 1 3 2 4

(B) 4 3 1 2

(C) 1 4 3 2

(D) 4 2 1 3

Q.17 The signal flow graph of a control system is shown below. Find the transfer function

relating input and output.

(A)

1 2

1 1 2 2

G G

1 G H G H (B)

1 1 2 2

1 2

G H G H

1 H H

(C)

1

2 1 2

G

1 G H H (D)

1 2

1 2

G G

1 H H

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Q.18 The circuit given below is which type of compensator

(A)Lead compensator

(B)Lag compensator

(C)Lead-Lag compensator

(D)None of the above

Q.19 The closed loop transfer function of a system is

5 4 3 2

s 8 s 6T s

s s 4s 4s s 2

The number of poles on RHP, LHP, imaginary axis

(A) 4,1,0

(B) 1,2,2

(C) 3,2,0

(D) 2,2,1

Q.20 The forward-path transfer function of a ufb system is

2

K(s )(s 3)G(s)

s(s 1)

The root-loci for a > 0 with K = 10 is

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Answer Key

Signals and Systems KST

1 2 3 4 5 6 7 8 9 10

D D B B 8000 C D D C D

11 12 13 14 15 16 17 18 19 20

B 891-909 .99-1.01 D C A A 2 C 4