LINEAR CONTROL SYSTEM(paper no. 1) by SURESH KUMAR.....sureshkumarthegreat@yahoo.com

LINEAR CONTROL SYSTEM

PAPER NO. 1

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PUT ON: 9th June, 2K3

                                               IC-204
                              LINEAR CONTROL SYSTEM
                                  (B.Tech 4th Semester,2063)
Time : 3 Hours                                                                                        Maximum Marks : 60
NOTE:- This paper consist of Three Sections. Section A is compulsory. Do any Four questions from
                 Section B and any two questions from Section C

                                     Section-A                                         Marks : 20

1 Answer the following short questions:
(a) How is a servo-mechanism different from a regulating system? Give examples.
(b) Differentiate between the order and the type of control systems with illustrative examples.
(c) How are sensitivity and stability of an open loop control system modified, if it is incorporated a negative feedback?
(d) How is state variable modeling superior to differential equation modelling ? Explain.
(e) Draw the block diagram of a non-unity feedback control system and distinguish between loop
    TF and closed loop TF if feedback is negative.
(f) Explain necessary and sufficient conditions of Routh-Hurwitz criterion and mention its limitations.
(g) Obtain TF of the two-phase a.c. servomotor and explain briefly its applications.
(h) Explain briefly the use of M-circles and N-circles for stability study of a feedback system.
(i) Explain how will you obtain Transfer Function of the system if its db-plot vs frequency is given.
(j) A unity f.b. system is described by its open loop TF, G(s) = 4/s(s + 5) Obtain unit-step response of above system.

                                              Section-B                                          Marks:5 Each

2. What do you mean by Mason's gain formulla in signal flow graph? Obtain the expression for overall gain of a
    system whose signal flow graph is given below:

3. What do you mean by TF of a linear system? Derive TF of an armature-controlled d.c. motor as shown in Fig.
with armature voltage (e_a) as input and θ(t), the load position as output.

4. Enumerate typical test signals used as input for obtaining transient response of a system. Show that the TF of the
system shown in figure C(s)/R(s) has a zero lying in right half of s-plane. Obtain c(t) when r(t) is a unit step for the
system.

5. What are the limitations of Routh-Hurwitz criterion? A u.f.b. system is characterised by its open loop TF
    G(s) = K(s + 13)/s(s + 3)(s + 7) Obtain the range of K for the system to be stable. Use R-H criterion.
6. Discuss various schemes for error detection using (i) Potentiometers and(ii) Synchros. Describe merits and demerits
    of above schemes of error detection.

                                               Section-C                                        Marks : 10 Each

7. Define gain margin and pahse amrgin for a system and show these margins on Bode' Plots and Nyquist Plot.
    A system is described by its loop TF G(s) = 10/s(1 + 0.5s)(1 + 0.25s). Obtain GM and PM from Bode's Plots
    and varify your results usingh the Nyquist Plot.
8. State and explain the rules for sketching the roots loci for a feedback control system. The open loop TF of an
    unity feedback control system is G(s) = K/s(s + 1)(s + 5). Sketch tne root loan diagram for the system and
    obtain K for which the system is critically stable.
9. Write short notes on the following:
    (a) Importance of state-variable modeling
    (b) On compensating network
    (c) Applications of magnetic amplifiers.

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