Principles of Control Systems - Dec 2013

Electronics Engineering (Semester 4)

TOTAL MARKS: 80
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Assume data if required.
(4) Figures to the right indicate full marks.

Answer any five of the following:-

1 (a) How to find gain margin and phase margin using bode plot?(4 marks) 1 (b) Compare open loop control system and closed loop control systems and give examples.(4 marks) 1 (c) Compare two stability methods:-
(i) Root locus
(ii) Routh's criterion.(4 marks) 1 (d) Draw the step responses of a standard second order undamped, under damped and critically damped system. Also show pole locations of these systems.(4 marks) 1 (e) Define 'Type' and 'Order' of the system. Hence determine type and order of control system with
(4 marks) 1 (f) Explain Hurwitz stability criterion. What are its disadvantages?(4 marks) 2 (a) Find the transfer function C(s)/(R(s) using block diagram reduction technique.
(10 marks) 2 (b) Derive the expression for output response of standard second order under damped system.(10 marks) 3 (a) Consider the following block diagram shown. Draw its equivalent signal flow graph and find its transfer function C(s)/R(s) using masons gain rule.
(10 marks) 3 (b) Find all the error coefficients for unity feedback systems having transfer function as
Calculate the type of system in each case.
(a)

(b)
(10 marks) 4 (a) Using Rouths stability criterion, determine the number of roots on imaginary axis for the system
s⁶+4s⁵+3s⁴-16s²-64s-48=0
and comment on stability of given system.(10 marks) 4 (b) Sketch the root locus for the system having

Obtain the value of K when damping ratio = 0.5 from the root locus. (10 marks) 5 (a) Sketch the Bode plot for the system.

Comment on system stability. (10 marks) 5 (b) Sketch the polar plot for the system having transfer function
(10 marks) 6 (a) Sketch the nyquist plot for
G(s)H(s)=50/[(s+1)(s+2)]
And comment on closed loop stability of system.(10 marks) 6 (b) Derive the transfer function of armature controlled dc servomotor and obtain the resulting block diagram.(10 marks)

Write short notes on the following:-

7 (a) Synchros.(7 marks) 7 (b) Correlation between time domain and frequency domain specifications.(7 marks) 7 (c) PI and PD controllers.(7 marks)