JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD

JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III CONTROL SYSTEMES ENGINEERING Previous Question Paper (November/December - 2018 - R15)

B.Tech | III | III-I | R15 | November/December - 2018

Answer PaperPaper Code: 125DUMaximum Marks: 75Time: 3 hours

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

125 marks

Distinguish between open loop and closed loop control systems with the help of neat diagrams.

2 marks

Answer

An open loop control system is one where the control action is independent of the output; the input is simply processed to produce an output without feedback. A closed loop control system uses a feedback path to compare the output with the reference input, generating an error signal to adjust the control action for accuracy.

Diagrams: Input -> Controller -> Plant -> Output (Open Loop); Input -> Summing Point -> Controller -> Plant -> Output, with a feedback path from Output back to the Summing Point (Closed Loop).

Explain with block diagrams the various effects of feed-back signal on the control system.

3 marks

Answer

Feedback affects a system by: 1) Reducing sensitivity to parameter variations, 2) Improving accuracy by minimizing steady-state error, and 3) Improving transient response by modifying damping and bandwidth. Block diagrams show the feedback loop subtracting the measured output from the input to create an error signal that drives the system.

Define steady state error of a control system and explain steady state error constants?

2 marks

Answer

Briefly discuss the effects of proportional derivative, proportional integral systems.

3 marks

Answer

Give the limitations of Routh’s stability criterion.

2 marks

Answer

Two first order systems have pole at -1 and -5 respectively. Comment on their relative stability.

3 marks

Answer

Explain how polar plots are useful in finding the stability of a system.

2 marks

Answer

Explain the terms gain margin and phase margin.

3 marks

Answer

Define state transition matrix.

2 marks

Answer

Briefly explain the concepts of Controllability and Observability.

3 marks

Answer

Part B

210 marks

State different rules which govern the block diagram reduction technique to obtain transfer function of a system.

5 marks

Answer

Reduce the given block diagram shown in below figure 1 and hence obtain the transfer function C(s)/R(s).

5 marks

Answer

310 marks

Describe the analogy between electrical and mechanical systems.

5 marks

Answer

For a signal flow graph in below figure 2, draw the block diagram, there by obtain transfer function.

5 marks

Answer

410 marks

A unity feedback control system has an open loop transfer function

G(S)=10/s(s+1)

. Find the time response of the system and the time constant and % overshoot, for a unit step input.

5 marks

Answer

What are standard test signals? Explain their significance.

5 marks

Answer

510 marks

For an under damped second order system, define various time domain specifications.

5 marks

Answer

The forward path transfer function of a unity feed-back control system is given by

G(s) = 2/s(s+3)

. Obtain the expression for unit step response of the system.

5 marks

Answer

The open-loop transfer function of a unity feedback control system is given by

G(s) = K / [ (s+2)(s+4)(s^2+6s+25) ]

. By applying the Routh criterion, discuss the stability of the closed-loop system as a function of K. Determine the values of K, which will cause sustained oscillations in the closed-loop system. What are the corresponding oscillation frequencies?

10 marks

Answer

Sketch the root locus diagram for a feedback system with the characteristic equation of which is given by

G(s) = K / [ s(s+2)(s^2+2s+2) ]

. Show clearly the steps involved.

10 marks

Answer

810 marks

Explain how exact Bode plot is obtained from asymptotic plot, with a figure.

5 marks

Answer

The open loop transfer function of a unity feed-back system is

G(s) = 50K / [ s(s+10)(s+5)(s+1) ]

. i) Determine the gain margin and phase margin. ii) And determine the value of steady state error coefficient for a gain of 10 db and the value which will make the closed loop system marginally stable. Use Bode diagram.

5 marks

Answer

Sketch the Nyquist plot and find the stability of the following system

G(s)H(s) = 100 / [ (s+2)(s+4)(s+8) ]

10 marks

Answer

Obtain the transfer function of a control system whose state model is

X'=AX(t)+BU(t); Y=CX(t)

. Where

A = [0 1 0; 0 -1 1; 0 -1 -10]

;

B = [0; 0; 10]

and

C = [1 0 0]

10 marks

Answer

1110 marks

Obtain the state model of a field controlled d.c. shunt motor.

5 marks

Answer

Construct the canonical state model for the system characterized by the following differential equation

y'' + 3y' + 2y = u' + u

5 marks

JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III CONTROL SYSTEMES ENGINEERING Previous Question Paper (November/December - 2018 - R15)

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Part B

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