JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II CONTROL SYSTEMS Previous Question Paper (December - 2017 - R15)
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. Each question carries 10 marks and may have a, b, c as sub questions.
Part A
What are the advantages of Open and Closed loop Control System.
Answer
The Open-loop control system is simple in construction, easy to maintain, and cost-effective due to the absence of feedback components. The Closed-loop control system provides high accuracy by reducing errors through feedback, effectively rejects external disturbances, and is less sensitive to variations in system parameters.
Explain the translatory and rotary elements of mechanical system.
Answer
Mechanical systems are categorized based on the type of motion, involving specific physical elements that store or dissipate energy.
For translatory mechanical systems, the three basic elements are:
- Mass (M): Stores kinetic energy; the force is proportional to acceleration, F = M(d²x/dt²).
- Spring (K): Stores potential energy; the force is proportional to displacement, F = Kx.
- Dashpot (B): Dissipates energy through friction; the force is proportional to velocity, F = B(dx/dt).
For rotary mechanical systems, the elements involve angular motion:
- Moment of Inertia (J): Stores rotational kinetic energy; torque is proportional to angular acceleration, T = J(d²θ/dt²).
- Torsional Spring (K): Stores potential energy; torque is proportional to angular displacement, T = Kθ.
- Rotational Dashpot (B): Dissipates energy; torque is proportional to angular velocity, T = B(dθ/dt).
Write two applications of AC servo motor.
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What is the advantages and disadvantages of Block diagram Reduction technique.
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Define static error constants.
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Explain PI and PD controller in time response of the system.
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State the advantages and limitations of Routh’s criterion.
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Define Break away and Break even points in root locus method.
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What are the advantages of frequency response analysis over time domain Analysis?
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Define gain margin and phase margin in bode plots.
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Part B
For the mechanical system given figure 1. Derive an expression for the transfer function.
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Give the classification of control systems with suitable examples.
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Explain why it is necessary to employ feedback in control systems and discuss the effect of feedback on various aspects regarding the performance of the system.
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Write the dynamic equation in respect of the mechanical system shown in Figure 2. Then using force-voltage analogy, obtain the equivalent electrical network.
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Explain about AC servo motor and derive the transfer function of AC servo motor.
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Explain signal flow graph and provide the procedural steps for solving signal flow graph.
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Explain the operation of Synchro transmitter and receiver pair and mention its applications.
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For the system represented shown in figure 3 find the transfer function C(S)/R(S) with block diagram reduction technique.
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Explain error constants Kp, Kv and Ka for type II system.
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Obtain the unit step response of a unity feedback control system whose open loop transfer function is G(s) = 1 / (s(s+1)) obtain also the rise time, peak time, maximum overshoot and settling time.
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For an under damped second order system, sketch its time response for unit step input and define various time domain specifications.
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The open loop transfer function of unity feedback system is given by G(S) = K / (s(1+Ts)). By what factor the amplifier gain be reduced so that (i) The peak overshoot of unit step response of the system is reduced from 75% to 25% (ii) The damping ratio increases from 0.1 to 0.6.
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Using Routh-Hurwitz criterion, investigate the location of roots of the given equation s6 + 2s5 + 4s4 + 4s3 + 9s2 + s + 6=0 and state stability of the system.
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Sketch the root locus for the unity feedback system whose open loop transfer function is G(s)H(s)=K(s2 +6s+25)/[s(s+1)(s+2)] and comment on stability.
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Explain concept of stability by Routh’s stability criterion.
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Sketch the root loci for the system with G(s)H(s) = K / (s(s+0.5)(s+0.6)(s+10)).
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Explain the steps for construction of bode plot.
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Draw the Bode plot for the system having G(s)H(S) = 100(0.02s+1) / (s(s+1)(0.1s+1)(0.01s+1)) and justify its stability.
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For a system having G(s)=k/s(s+2)(s+20), H(s)=1, construct Bode plot and determine: a) limiting value of K for the system to be stable b) value of k for the gain margin to be 10db c) value of k for the phase margin to be 50deg.
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