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Code No: NR220206 NRII B.Tech II Semester Supplementary Examinations, Apr/May 2006

CONTROL SYSTEMS(Electrical & Electronic Engineering)

Time: 3 hours Max Marks: 80Answer any FIVE Questions

All Questions carry equal marks

1. (a) Explain the operation of ordinary traffic signal, which control automobile traf-c at roadway intersections. Why are they open loop control systems? Howcan traffic be controlled more effectively?

(b) For a signal ow graph in Figure 1 given below, determine the overall gain bymasons gain formula. [8+8]

Figure 1:

2. (a) Derive the Transfer Function for potential divider.(b) Derive the Transfer Function for a.c. servomotor. [8+8]

3. (a) Determine whether the largest time constant of the characteristic equationgiven below is greater than, less than, or equal to 1.0 sec. s3 + 4 s2+6s+4=0

(b) Figure2. is a block diagram of a space-vehicle attitude-control system. As-suming the time constant T of the controller to be 3 sec., and the ratio K/J tobe 29 rad

2/sec 2, nd the damping ratio and natural frequency of the system.[6+10]

4. (a) Find the roots of the characteristic equation for systems whose open-looptransfer functions are given below. Locate the roots in the s-plane and indicatethe stability of each system.

i. G(s)H(s)= 1(s +2)( s +4)ii. G(s)H(s)= 5( s +3)s (s +3)( s +8)

(b) A feedback system has an open-loop transfer function of G(s)H(s)= Ke s

s (s 2 +5 s +9). Determine the use of Routh criterion, the maximum value of K for theclosed-loop system to be stable. [8+8]

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Code No: NR220206 NR

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5. (a) Calculate the values of K and for the point in s-plane at which the root locusof G(s)H(s)= K s (s +2)( s 2 +2 s +2) intersects the imaginary axis.

(b) Determine the Breakaway points of the root locus for the open loop transferfunction G(s)H(s)= K (s +2)( s +4) [8+8]

6. G(s)H(S) = K 10 (1 s )S (S +2)( S 2 +2 S +25) with K = 1,Sketch asymptotic bode plot & nd gain margin & phase margin. By what factorshould K be increased or decreased to obtain a gain margin of 40 db. [4x4]

7. (a) Explain how Nyquist contour is selected for stability analysis.(b) Discuss the stability of the following system using Nyquist stability criterion

G(s)H (s) = K (T s +1) s [6+10]

8. (a) Dene the termsi. State variable

ii. State transition matrix. [4+4](b) Obtain the state equation and output equation of the electric network show

in Figure3 [8]

Figure 3:

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