DipIETE – ET (OLD SCHEME)

Code: DE15 Subject: CONTROL ENGINEERING

Time: 3 Hours Max. Marks: 100

NOTE: There are 9 Questions in all.

· Question 1 is compulsory and carries 20 marks. Answer to Q.1 must be written in the space provided for it in the answer book supplied and nowhere else.

· Out of the remaining EIGHT Questions, answer any FIVE Questions. Each question carries 16 marks.

· Any required data not explicitly given, may be suitably assumed and stated.

Q.1 Choose the correct or the best alternative in the following: (210)

a. The system with the characteristic equation is _________.

(A) stable (B) marginally stable

(C) not necessarily stable (D) unstable

b. Signal flow graph is used to obtain __________.

(A) stability of the system

(B) transfer function of the system

(C) dynamic response of the system

(D) poles of the system

c. The second order system is defined by is given a step input. The time taken for the response to settle within ± 2% of input is ________.

(A) 1.2 ses (B) 1.6 sec

(C) 2 sec (D) 0.4 sec

d. For the transfer function, the breakaway point will lie between _________.

(A) 0 and –1 (B) –1 and –2

(C) –2 and –3 (D) beyond –3

e. If the open loop transfer function G (jw) of a unity feedback system has a phase angle of –150^{o at the gain cross-over frequency, the phase margin of the system is equal to __________.}

(A) –150^o (B) 210^o

(C) 30^o (D) –30^o

f. The steady state error of a stable type ‘0’ unity feedback system for a unit step function is given as __________.

(A) 0 (B)

(C) (D)

g. From the Nichols chart, one can determine the following quantities pertaining to closed loop system as:

(A) Magnitude and phase (B) Bandwidth

(C) Magnitude only (D) Both (A) & (B)

h. The transfer function of a simple RC network functioning as compensator is. The condition for RC network to act as phase lead controller is ________.

(A) (B)

(C) (D)

i. Gain cross-over frequency is defined as the frequency at which _________.

(A) (B)

(C) (D)

j. If stability error for step input and speed of response be the criteria for design, what type of controller would you recommend?

(A) P Controller. (B) PD Controller.

(C) PI Controller. (D) PID controller.

Answer any FIVE Questions out of EIGHT Questions.

Each question carries 16 marks.

Q. 2 a. Define state space model and transfer function model. Give advantages and limitations of state space model over transfer function model. (8)

b. A unit step signal is applied on the second order system given by . Find the dynamic response for (8)

Q. 3 a. Reduce the block diagram shown in the Fig.1 below and obtain the transfer function. (8)

.

b. Explain with neat sketches the construction and working of synchros. (8)

Q. 4 a. Discuss the basic feedback characteristics of feedback control system. (8)

b. Define stability, absolute stability, relative stability and conditional stability.

(8)

Q. 5 a. Find the steady state error for unit step, unit velocity and unit acceleration inputs for the system with . (8)

b. Sketch the root locus of a unity feedback system with. (8)

Q. 6 a. Draw the bode plot for the following transfer function and determine the stability margins: (8)

b. What is M-circle? Explain in detail. (8)

Q.7 a. Using Nyquist Criterion, comment on the stability of the system whose open loop transfer function is . (8)

b. With the help of block diagrams explain briefly:

(i) Derivative error and

(ii) Integral error compensation. (8)

Q. 8 a. Write short note on:

(i) Use of digital computer as compensator.

(ii) Op-amp. (8)

b. State the necessary condition for the Routh’s criterion for stability. Determine the stability of the system whose characteristic equation is given by . (8)

Q. 9 a. What is Mason Gain Rule? Obtain for the signal flow graph shown in

Fig.2. (8)

b. Discuss the tuning of PID controllers. (8)