7/27/2019 Digital Control Systems (4)

1/2

Code No: C7502

JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD

M.Tech I SEMESTER EXAMINATIONS, APRIL/MAY-2013

DIGITAL CONTROL SYSTEMS

(CONTROL SYSTEMS)

Time: 3hours Max.Marks:60

Answer any five questions

All questions carry equal marks- - -

1.a) With the help of suitable circuit explain the principle of operation of sample and

hold devices. Derive the transfer function of zero order hold circuit.

b) With suitable diagram explain any method of analog to digital conversion.

2.a) Obtain the z transform of the following x(t)

i) x(t) = )1(1 at

ea

and ii) atettx = 2)( where a is a constant.

b) Obtain the inverse z-transform of the following:

i) X(z)=2

2

)1(

154.0478.0368.0

zz

zz

++ and ii)

1)(

2 +=z

zzX .

3. The block diagram of a digital control system is shown in Figure 1, where

)5()(

+=

ss

KsG

p .

Using Jurys stability criterion, determine the range of K for the system to be

asymptotically stable.

4. The block diagram of a discrete data control system is shown in Figure 2, in

which)2(

)1(2)(

+

+=

ss

ssGp and T = 0.5 sec. Compute and plot the unit step response

c*

(t) of the system. Find the step, ramp, and parabolic error constants. Also findvalue of c(kT).

ZOH Gp(s)R(s)

+

-

Y (s)

Plant

T

E(s) E*s)

Gh0(s) Gp(s)

r(t) +

-

y (t)

PlantT= 0.5sec

R09

Figure: 1

Figure: 2

w.jntuworld.com

www.jntuworld.com

www.jwwww.android.jntuworld.com

7/27/2019 Digital Control Systems (4)

2/2

5. Draw root locus in the z-plane for the system shown in Figure 3 for 0