**GITAM University B.E Electronics and Communication Control Systems Question paper**College of Engineering

Gandhi Institute of Technology and Management, Visakhapatnam

(Affiliated to Andhra University)

B.E. (Electronics and Communications Engineering ) Second Year

Second Semester Examinations 2004-2005

(Autonomous Stream)

EC 227 Control Systems

Time: 3 Hours Max. Marks: 60

1. Answer Question No. 1 ( Part – A) and any four of the remaining seven (Part – B)

2. All parts of a Question must be answered in one place, otherwise they will not be valued.

3. Figures in the right hand margin indicate marks allotted.

PART – A

1. Answer the following. 10x2=20

a) What are the advantages of a closed-loop system?

b) Compare the terms ‘stability’ & ‘sensitivity’.

c) The impulse response of a system is e-0.2t. Determine the transfer function of the system.

d) How does the performance of an automatic control system is effected by a positive feedback signal.

e) State Mason’s gain formula.

f) Define ‘rise time’ and ‘settling time’.

g) What are the effects of adding poles and zeros to the transfer function?

h) State the advantages of frequency domain analysis.

i) What will happen if a zero is added in the forward path of a second-order system?

j) Define a series-parallel compensation.

PART – B

Answer any four of the following. If you attempt more than four questions, only the first four in order will be valued.

2. Obtain the overall transfer function C/R from the signal flow graph shown: (10)

3. a) Determine the mathematical model for the system shown in the figure. (5)

b) Derive the transfer function of field controlled dc servomotor. (5)

4. Measurements conducted on a servomechanism show the system response to be

C(t)= 1 + 0.2 e-60t – 1.2 e-10t when subjected to a unit-step input.

a) Obtain the expression for the closed-loop transfer function.

b) Determine the undamped natural frequency and damping ratio of the system. (10)

5. Sketch the root locus diagram for the feedback control system having the following open-loop transfer function. Assume that ‘K’ will take all positive values from 0 to .

G(s) =

(10)

6. Draw the Bode plot of a closed-loop system which has the open-loop transfer function.

G(s)H(s) =

Determine the maximum value of ‘T’ for system to be stable. (10)

7. Write short notes on the following:

a) Effect of derivative control on transient and steady state performance of f.B.control system. (5)

b) Discuss lead compensator. Sketch the Bode plot of a lead compensator and give the design steps of a lead compensator. (5)

8. a) Explain Routh-Hurwitz criterion. (4)

b) Investigate the stability of the system with characteristic equation.

s5+2s4+24s3+48s2 – 25s – 50 = 0

Also find all the roots of this equation. (6)