JNTU
JNTU B.Tech II CONTROL SYSTEMS Previous Question Paper (May - 2019 - R13)
Note: This question paper contains two parts A and B. Part A is compulsory which carries 25 marks. Answer all questions in Part A. Part B consists of 5 Units. Answer any one full question from each unit.
Part A
Answer all questions:
Why negative feedback is invariably preferred in a closed loop system?
Answer
Negative feedback is preferred because it reduces system sensitivity to parameter variations, improves bandwidth, reduces noise and distortion, and enhances overall system stability by minimizing the error signal.
What are the basic elements used for modeling of mechanical translational and rotational system?
Answer
For mechanical translational systems, the basic elements are mass (M), spring (K), and dashpot/damper (B). For mechanical rotational systems, the basic elements are moment of inertia (J), torsional spring (K), and rotational damper (B).
What are the characteristics of servomotors? Compare the AC and DC servomotor.
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What are the merits and demerits of block diagram representation of a system?
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What are the standard test signals used in time domain analysis?
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Draw time response of second order system and represent time domain specifications on it.
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What are the limitations of Routh’s stability criterion?
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What are the effects of adding poles and zeroes to G(s)H(s) on the root loci?
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Define Phase Margin and Gain Margin.
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List out frequency domain specification and explain.
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Part B
Feedback characteristics and mechanical modeling.
What is a feedback? Discuss its characteristics. What are the effects of feedback on sensitivity and external noise? Discuss advantages and disadvantages of feedback?
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Find transfer function θ2(s)/T(s) for a given rotational mechanical system.
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Impulse response and mechanical system modeling.
Explain and derive the relation between impulse response and transfer function.
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Determine transfer function relating X1(s) to F(s) for the mechanical system.
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DC Servomotors and Signal Flow Graphs.
Derive transfer function and develop block diagram of field controlled DC servo motor. Also explain its torque-speed characteristics.
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Determine the closed loop transfer function from the signal flow graph.
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Mason's Gain Formula and block diagrams.
Derive the Mason’s gain formula of signal flow graph.
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Evaluate closed loop transfer function for given block diagram when input is (i) at station I (ii) at station II.
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Controllers and steady state analysis.
Discuss, in detail, the effects of proportional, derivative, proportional integral controllers on the system performance.
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For the given open loop transfer function, determine steady state error for unity step, unity ramp and unity acceleration inputs. Also determine damping factor and natural frequency of dominant roots.
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Error constants and servo systems.
Derive the expression for generalized error constants.
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Obtain steady state error of the system when subjected to an input signal.
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Routh-Hurwitz and Root Locus.
Construct Routh array and determine stability of the system. Comment on the location of the roots.
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Define and derive breakaway points on the root locus plot.
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Root Locus analysis.
Sketch root locus plot of closed loop system for positive values of K and there from determine value of K that would make system stable.
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Bode Plot stability analysis.
Draw Bode plot for the given open loop transfer function, find gain margin and phase margin and comment on stability.
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Frequency response design.
Determine value of gain constant K for the system so that it has a phase margin of about 35°. For this value of K, find new gain margin.
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