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Control Engg : Question Paper Jun 2014 - Mechanical Engineering (Semester 8) | Visveswaraya Technological University (VTU)
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Control Engg - Jun 2014

Mechanical Engg. (Semester 8)

TOTAL MARKS: 100
TOTAL TIME: 3 HOURS
(1) Question 1 is compulsory.
(2) Attempt any four from the remaining questions.
(3) Assume data wherever required.
(4) Figures to the right indicate full marks.
1 (a) Distinguish between open-loop and closed loop systems with examples.(5 marks) 1 (b) Explain the requirements of a control system.(5 marks) 1 (c) Explain following controller. State its characteristics:
i) Proportional plus derivative control action
ii) Proportional plus integral plus derivative control action.
(10 marks)
2 (a) Write the equilibrium equations for the mechanical system shown in Fig Q2(a), hence obtain the F-I analogous system. (10 marks) 2 (b) Obtain the transfer function of field controlled DC motor.(10 marks) 3 (a) Reduce the block diagram and obtain its transfer function $$ \dfrac {C(s)}{R(s)} $$ (10 marks) 3 (b) Find $$ \dfrac {C(s)} {R(s)} $$ by Mason's gain formula. (10 marks) 4 (a) Obtain an expression for time response of the first order system subjected to unit step input.(8 marks) 4 (b) Determine the damping ratio and natural frequency for the system whose maximum overshoot response is 0.2 and peak time is 1 sec. Find rise time and settling time.(6 marks) 4 (c) State whether the system is stable or unstable s6+2s5+8s4+123+20s2+16s+16=0 using Routh's stability criterion.(6 marks) 5 (a) Sketch the polar plot of TF $$ G(s)H(s)= \dfrac {1}{(1+5s)(1+10s)} $$(6 marks) 5 (b) Sketch the Nyquist plot for a system, whose transfer function, $$ G(s) H(s)= \dfrac {K}{s(s+4)(s+8)} $$ Determine the range of values of K for which the system in stable.(14 marks) 6 For a system $$ G(s)H(s)= \dfrac {242(s+5)} {s(s+1)(s^2+5s+121)} $$ sketch the Bode plot. Find ωpc and ωgc GM, PM. Comment on stability.(20 marks) 7 For a unity feedback system, $$ G(s) H(s)= \dfrac {K}{s(s+4)(s+2)} $$ sketch the rough nature of the root locus, showing all details on it.(20 marks) 8 (a) What is compensation? How are compensators classified?(6 marks) 8 (b) Write notes on:
i) Lead compensator
ii) Lag compensator
(8 marks)
8 (c) A system is governed by the differential equation $$ \dfrac {d^3y}{dt^3}+ 6 \dfrac {d^2y}{dt^2}+ 11 \dfrac {dy}{dt}+10 =8u(t) $$ where y is the output and u is the input of the system. Obtain a state space representation of the system.(6 marks)

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