[EUREC 406]

B.Tech. DEGREE EXAMINATION

Electronics & Communication Engineering

IV SEMESTER

COSNTROL SYSTEMS (Effective from the admitted batch 2007–08)

Time: 3 Hours Max.Marks: 60

------------------------------------------------------------------------------------ Instructions: Each Unit carries 12 marks.

Answer all units choosing one question from each unit.

All parts of the unit must be answered in one place only.

Figures in the right hand margin indicate marks allotted.

------------------------------------------------------------------------------------------

UNIT-I

1. a) Discuss the reduction techniques for obtaining transfer

function of a block diagram. 6

b) Obtain the transfer function C(s) / R(s) for the SFG given

in fig.1. 6

OR

2. a) Derive the transfer function of a DC servomotor in armature

control. 6

b) Find the transfer function sF

sx2 of the system given in fig.2. 6

UNIT-II

3. a) The open loop transfer function of unity feedback system is

STsKsG 1/ , where K and T are positive constants.

How many times gain should be increased to increase the

overshoot from 40% to 60%? 6

b) A system has unit step response as c(t) =1-e-0.1t

. Determine

its unit impulse and ramp response. Assume zero initial

conditions. 6

OR

4. Discuss the effect of derivative control on transient and steady

state performance of feedback control systems. Also explain

the need for integral control. 12

UNIT-III

5. Determine the range of K for stability, frequency of oscillation

of the systems, if any, given by their characteristic equations. 12

i) 0322 234 KsKsss

ii) 015322 2345 sssss

iii) 016201282 23456 Kssssss

OR

6. Sketch the root locus of the system having loop transfer function.

22s 1 2 sss

KsHsG

and infer the relevant information. Also indicate the effect, if a

zero at -2 is introduced in the loop transfer function. 12

UNIT-IV

7. Explain the correlation between time and frequency response

specifications. 12

OR

8. A system has 0.02s1 0.1s1 1/ ssKsHsG .

Determine the value of K so that

i) Gain margin is + 10 db

ii) Phase margin is + 250. Draw the Bode plot. 12

UNIT-V

9. a) Define state and the significance of state variables. Also

compare the state variable representation to transfer function,

bringing out their advantages and disadvantages. 4

b) Obtain the unit step response of the system given by

uX 2

0x

52

30. 8

OR

10. a) Explain the properties of state transition matrix. 4

b) Define controllability and observability and determine the

same for the system given by 8

uX 5

3x

32

14

and

x21Y

[04/IVS/107]